Friday, August 28, 2009

United States Patent 7,040,213
WWW.USPTO.GOV
Herring
May 9, 2006

Firearm receiver system with belt-feed capability

Abstract

A firearm receiver system including a receiver body, an ammunition belt feeding assembly and a bolt carrier. The receiver body includes a first face and a second face approximately opposite the first face. The receiver body is configured for having means for triggering engaged therewith at the first face and for receiving belt-fed ammunition through the second face. The ammunition belt feeding assembly is mounted at least partially on the receiver body and the ammunition belt feeding assembly is configured for supplying the belt-fed ammunition to the receiver body through the second face. The bolt carrier is movably mounted on the receiver body between the first and second faces of the receiver body and the bolt carrier is configured for being actuated by gas-energized piston-driven means.
Inventors: Herring; Geoffrey A. (Blacksburg, VA)
Appl. No.: 10/640,133
Filed: August 13, 2003
Related U.S. Patent Documents

Application Number Filing Date Patent Number Issue Date
09734279 Dec., 2000 6634274

Current U.S. Class: 89/33.14 ; 89/33.16
Current International Class: F41A 9/00 (20060101)
Field of Search: 89/33.14,33.16,33.04,191.01,193
References Cited [Referenced By]
U.S. Patent Documents

2058897 October 1936 Marek
2383487 August 1945 Johnson, Jr.
2792761 May 1957 Simpson
2951424 September 1960 Stoner
3035495 May 1962 Stoner
3045555 July 1962 Stoner
3198076 August 1965 Stoner
3713363 January 1973 Hurlemann
4942802 July 1990 Stoner
5117735 June 1992 Flashkes
Primary Examiner: Clement; M.
Attorney, Agent or Firm: Galasso; Raymond M. Galasso & Associates, L.P.
WWW.GAPATENTS.COM

Parent Case Text


CROSS-REFERNCE TO RELATED APPLICATION

This is a Divisional Utility patent application to U.S. patent application having Ser. No. 09/734,279 filed on Dec. 11, 2000 now U.S. Pat. No. 6,634,274.
Claims


What is claimed is:

1. A firearm receiver system, comprising: a receiver body having a first face and a second face approximately opposite the first face, wherein the receiver body is configured for having means for triggering engaged therewith at the first face and for receiving belt-fed ammunition through the second face; and a self-contained ammunition belt feeding assembly mounted completely on the receiver body, wherein the self-contained ammunition belt feeding assembly includes an ammunition belt feeding mechanism configured for supplying said belt-fed ammunition to the receiver body through the second face.

2. The firearm receiver system of claim 1, further comprising: a bolt carrier movably mounted on the receiver body between the first and second faces of the receiver body, wherein the bolt carrier is configured for being actuated by gas-energized piston-driven means.

3. The firearm receiver system of claim 2 wherein being configured for being actuated by gas-energized piston-driven means includes having a tappet rod engagement member extending from the bolt carrier.

4. The firearm receiver system of claim 3 wherein the tappet rod engagement member is positioned between the first and second faces of the receiver body.

5. The firearm receiver system of claim 3 wherein: the tappet rod engagement member is positioned within a channel in the receiver body; and the channel is in a wall of the receiver body between the first and second faces of the receiver body.

6. The firearm receiver system of claim 1, further comprising: a bolt carrier movably mounted on the receiver body between the first and second faces of the receiver body, wherein the bolt carrier is configured for being actuated by gas-energized piston-driven means.

7. The firearm receiver system of claim 6 wherein being configured being actuated by gas-energized piston-driven means includes having a tappet rod engagement member extending from the bolt carrier.

8. The firearm receiver system of claim 6 wherein the receiver body includes a magazine-fed ammunition port in the first face and a belt-fed ammunition port in the second face.

9. The firearm receiver system of claim 1, further comprising: a bolt carrier movably mounted on the receiver body between the first and second faces of the receiver body, wherein the bolt carrier is configured for being actuated by gas-energized piston-driven means; and a bolt attached to the bolt carrier and having a cam pin attached thereto extending through a cam slot in the bolt carrier, wherein the bolt has a retaining arm attached thereto that is engaged with the cam pin for retaining the cam pin in a first region of the cam slot when the bolt is in an unlocked position and wherein the retaining member is pivotable for allowing the cam pin to rotate to a second region of the cam slot when the bolt carrier reaches a closed position.

10. The firearm receiver system of claim 1, further comprising: a bolt carrier movably mounted on the receiver body between the first and second faces of the receiver body, wherein the bolt carrier is configured for being actuated by gas-energized piston-driven means; and a bolt attached to the bolt carrier and having a cam pin attached thereto extending through a cam slot in the bolt carrier into a bolt carrier lug channel of the receiver body, wherein the cam pin is positioned in a first region of the cam slot when the bolt carrier is in an open position and wherein the cam pin being rotated to a second region of the cam slot and into a corresponding relief in the receiver body when the bolt carrier reaches a closed position.

11. The firearm receiver system of claim 1, further comprising: a bolt carrier movably mounted on the receiver body between the first and second faces of the receiver body, wherein the bolt carrier is configured for being actuated by gas-energized piston-driven means and wherein the ammunition belt feeding mechanism is coupled to the bolt carrier.

12. A firearm receiver system, comprising: a receiver body having a first face and a second face approximately opposite the first face, wherein the receiver body is configured for having means for triggering engaged therewith at the first face and for receiving belt-fed ammunition through the second face; an ammunition belt feeding assembly mounted completely on the receiver body, wherein the ammunition belt feeding assembly is configured for supplying said belt-fed ammunition to the receiver body through the second face; and a bolt carrier movably mounted on the receiver body between the first and second faces of the receiver body, wherein the bolt carrier includes a tappet rod engagement member extending therefrom for enabling actuation of the bolt carrier by gas-energized piston-driven means and wherein the tappet rod engagement member is positioned between the first and second faces of the receiver body.

13. The firearm receiver system of claim 12 wherein: the tappet rod engagement member is positioned within a channel in the receiver body; and the channel is in a wall of the receiver body between the first and second faces of the receiver body.

14. The firearm receiver system of claim 12 wherein the receiver body includes a magazine-fed ammunition port in the first face and a belt-fed ammunition port in the second face.

15. The firearm receiver system of claim 12, further comprising: a bolt attached to the bolt carrier and having a cam pin attached thereto extending through a cam slot in the bolt carrier, wherein the bolt has a retaining arm attached thereto that is engaged with the cam pin for retaining the cam pin in a first region of the cam slot when the bolt is in an unlocked position and wherein the retaining member is pivotable for allowing the cam pin to rotate to a second region of the cam slot when the bolt carrier reaches a closed position.

16. The firearm receiver system of claim 12, further comprising: a bolt attached to the bolt carrier and having a cam pin attached thereto extending through a cam slot in the bolt carrier into a bolt carrier lug channel of the receiver body, wherein the cam pin is positioned in a first region of the cam slot when the bolt carrier is in an open position and wherein the cam pin being rotated to a second region of the cam slot and into a corresponding relief in the receiver body when the bolt carrier reaches a closed position.

17. The firearm receiver system of claim 12 wherein the bolt carrier is configured for being actuated by gas-energized piston-driven means and wherein the ammunition belt feeding assembly includes an ammunition belt feeding mechanism coupled to the bolt carrier.

18. A firearm upper receiver system, comprising: an upper receiver body having a first face and a second face approximately opposite the first face, wherein the upper receiver body is configured for having a lower receiver engaged with the upper receiver body at the first face, for receiving magazine-fed ammunition through the first face and for receiving belt-fed ammunition through the second face; an ammunition belt feeding assembly mounted completely on the upper receiver body, wherein the ammunition belt feeding assembly is configured for supplying said belt-fed ammunition to the upper receiver body through the second face; and a bolt carrier movably mounted on the upper receiver body between the first and second faces of the receiver body, wherein the bolt carrier includes a tappet rod engagement member extending therefrom for enabling actuation of the bolt carrier by gas-energized piston-driven means and wherein the tappet rod engagement member is positioned between the first and second faces of the upper receiver body.

19. The firearm upper receiver system of claim 18, further comprising: a bolt attached to the bolt carrier and having a cam pin attached thereto extending through a cam slot in the bolt carrier, wherein the bolt has a retaining arm attached thereto that is engaged with the cam pin for retaining the cam pin in a first region of the cam slot when the bolt is in an unlocked position and wherein the retaining member is pivotable for allowing the cam pin to rotate to a second region of the cam slot when the bolt carrier reaches a closed position.

20. The firearm upper receiver system of claim 18, further comprising: a bolt attached to the bolt carrier and having a cam pin attached thereto extending through a cam slot in the bolt carrier into a bolt carrier lug channel of the receiver body, wherein the cam pin is positioned in a first region of the cam slot when the bolt carrier is in an open position and wherein the cam pin being rotated to a second region of the cam slot and into a corresponding relief in the receiver body when the bolt carrier reaches a closed position.

21. The firearm upper receiver system of claim 18 wherein the bolt carrier is configured for being actuated by gas-energized piston-driven means and wherein the ammunition belt feeding assembly includes an ammunition belt feeding mechanism coupled to the bolt carrier.
Description


BACKGROUND OF THE INVENTION

The disclosures herein relate generally to firearms, and more particularly to firearm upper receivers with belt-feed capability.

Many firearms, such as assault rifles, that are commonly used in military situations are not designed by their manufacturer for use with belt-feed ammunition. Typically, such firearms are designed by their manufacturer for receiving ammunition from an ammunition magazine. The AR-15 family of firearms, including the M-16 type firearms, illustrate examples of assault rifles that are designed by their manufacturer to receive ammunition exclusively from an ammunition magazine. M-16 type firearms are a military version of the AR-15 family of firearms capable of operating in a fully automatic mode. M-16 type firearms have been manufactured by companies including, but not limited to Colt Manufacturing Company, the ArmaLite Division of Fairchild Aircraft and Engine Company, BushMaster Firearms Incorporated and Fabrique Nationale. A standard ammunition magazine for M-16 type firearms holds approximately 30 rounds of ammunition. The versatility of firearms that are intended for use in military situations and that are designed for receiving ammunition exclusively from an ammunition magazine is significantly limited.

Some firearms, such as M-16 type firearms, may be operated in a fully automatic mode. When being operated in the fully automatic mode, firing of a round of ammunition automatically facilitates ejection of each spent round from the firing chamber and chambering of a new round into the firing chamber. As long as the trigger of such as firearm is depressed, the firearm will continue to fire until all of the ammunition is depleted.

Due to the attainable firing rate of firearms operated in a fully automatic mode and the limited ammunition capacity of standard ammunition magazines, the use of ammunition magazines with such firearms results in a significant amount of down-time of the firearm for allowing a depleted magazine to be replaced with a full ammunition magazine. Most automatic firearms are capable of firing ammunition at a rate of 150 rounds or more per minute. At a firing rate of 150 rounds per minute, a 30 round ammunition magazine can be depleted of ammunition in as little as about 12 seconds of continuous firing.

In many situations, such as in military combat, a high-capacity ammunition delivery system such as a belt-feed system is preferred over an ammunition magazine. A typical ammunition belt for a belt-feed system holds 200 or more rounds of ammunition. At a firing rate of 150 rounds per minute, a 200 round ammunition belt can be depleted in as little as about 80 seconds. Accordingly, for a given firearm design, the minimum time to depletion of a 200 round ammunition belt is as much as about 7 times greater than that of a 30 round ammunition magazine. As a result of the increased time to depletion, belt-feed ammunition systems are preferred in many military situations.

Attempts have been made to increase the versatility of magazine-fed firearms by modifying them to accept belt-feed ammunition. The CAR-15 heavy assault rifle model M2, developed by Colt Manufacturing Company, illustrates an example of such a modified firearm. The ArmaLite Division of the Fairchild Engine and Airplane Corporation also developed such a modified firearm for receiving magazine-fed and belt-feed ammunition.

To date, magazine-fed firearms that have been modified to accept belt-feed ammunition, including those discussed above, have required modification to an upper receiver assembly and a lower receiver assembly of the firearm. Facilitating modifications to the upper and to the lower receiver assemblies is costly. Furthermore, the lower receiver assembly of many firearms, such as M-16 type firearms, is the registerable portion of the firearm that carries a serial number for enabling compliance with registration requirements of the United States Bureau of Alcohol, Tobacco & Firearms. As a result of the lower receiver assembly being the portion of the firearm that is registerable, it can only be modified legally by a licensed firearm manufacturer.

The bolt carrier group of many automatic firearms, such as M-16 type firearms, are energized using pressure generated by the combustion of powder in a cartridge. Such firearms are considered to be gas energized. In such firearms, it is typical for combustion gas to be routed from the barrel to the receiver assembly that carries the bolt carrier group (referred to herein as the bolt-carrying receiver). In this manner, pressure associated with the combustion gas is used to supply the energy needed for facilitating ejection of a spent cartridge from the firing chamber and feeding of a new round of ammunition into the firing chamber. Accordingly, the bolt carrier groups of types of firearms are gas driven as well as gas energized.

The routing of the combustion gas to the bolt-carrying receiver results in several adverse situations. One adverse situation is that over time, deposits from the combustion gas are formed inside the bolt-carrying receiver. Such deposits adversely affect operation of the firearm and, in some cases, prevent its operation until the bolt-carrying receiver is cleaned. Another adverse situation is that the combustion gases are vented into the general area of an operator's face, impairing the operator's sight and respiration.

Accordingly, what is needed is a receiver assembly capable of reducing the shortcomings associated with conventional gas-driven automatic firearms that are manufacturer configured for receiving ammunition exclusively from an ammunition magazine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view illustrating an embodiment of a firearm having an ammunition belt attached to an upper receiver assembly.

FIG. 1B is a side view of the firearm of FIG. 1A having an ammunition magazine attached to a lower receiver assembly, and the ammunition belt detached from the upper receiver assembly.

FIG. 1C is a side view illustrating an embodiment of a trigger group in the lower receiver assembly of the firearm of FIG. 1A.

FIGS. 2A 2H are fragmentary side views illustrating an embodiment of an operational cycle of the firearm of FIG. 1B with the ammunition being supplied from an ammunition magazine.

FIG. 3A is a side view illustrating an embodiment of an upper receiver assembly having a piston tube assembly and a barrel assembly attached thereto.

FIG. 3B is a perspective view of the upper receiver assembly, the piston tube assembly and barrel assembly depicted in FIG. 3A.

FIG. 4 is side view illustrating the barrel assembly depicted in FIG. 3A.

FIGS. 5A and 5B are cross-sectional views illustrating an embodiment of a firearm having an adjustable gas regulator coupled to a piston tube assembly for displacing a tappet assembly, with an operating rod of the piston tube assembly being in a static position and a displaced position, respectively.

FIGS. 6A and 6B are side views illustrating an embodiment of a tappet assembly in relation to the displaced position and the static position, respectively, of the operating rod depicted in FIGS. 5A and 5B.

FIG. 7 is a cross-sectional view taken along the line 7--7 in FIG. 6A.

FIG. 8 is a partial top view illustrating an upper receiver assembly as disclosed herein.

FIG. 9 is a cross-sectional view taken along the line 9--9 in FIG. 8, depicting a bolt catch in an unlocked position.

FIG. 10 is a cross-sectional view taken along the line 10--10 in FIG. 8, depicting a bolt catch in a locked position.

FIG. 11 is a partial perspective view illustrating an embodiment of a mechanism for rotating a bolt, with the bolt being depicted in an unlocked position.

FIG. 12 is a partial top perspective view of the mechanism depicted in FIG. 11, with the bolt being depicted in a locked position.

FIG. 13 is an exploded perspective view illustrating embodiments of a bolt, a firing pin, and cam pin.

FIG. 14 is a perspective view illustrating another embodiment of a mechanism for rotating a bolt.

FIG. 15 is a partial side view of the mechanism depicted in FIG. 14 mounted in an upper receiver body, with the bolt being depicted in the unlocked position.

FIG. 16 is a partial side view of the mechanism depicted in FIG. 14 mounted in an upper receiver body, with the bolt being depicted in the locked position.

FIG. 17 is a perspective view illustrating an embodiment of a bolt carrier of the mechanism depicted in FIG. 14.

FIG. 18 is a partial perspective view illustrating an embodiment of an ammunition belt feeding assembly.

FIG. 19 is a top view illustrating an embodiment of a top cover of the ammunition belt feeding assembly depicted in FIG. 18.

FIG. 20 is a perspective view illustrating an embodiment of a feed tray of the ammunition belt feeding assembly depicted in FIG. 18.

FIGS. 21A and 21B are diagrammatic views illustrating an embodiment of a lever-type ammunition belt feeding mechanism with a cam lever in a static position and a displaced position, respectively.

FIG. 22 is a plan view illustrating an embodiment of a feed link of the ammunition belt feeding mechanism depicted in FIGS. 21A and 21B.

FIG. 23 is a plan view illustrating an embodiment of a first slide member of the ammunition belt feeding mechanism depicted in FIGS. 21A and 21B.

FIG. 24 is a plan view illustrating an embodiment of a second slide member of the ammunition belt feeding mechanism depicted in FIGS. 21A and 21B.

FIGS. 25A 25E are diagrammatic views illustrating an embodiment of an operational cycle of the ammunition belt feeding mechanism depicted in FIGS. 21A and 21B.

FIG. 26 is a diagrammatic view illustrating an embodiment of a sprocket-type ammunition belt feeding mechanism.

FIG. 27 is an exploded perspective view illustrating an embodiment of a drive shaft assembly of the sprocket-type ammunition belt feeding mechanism depicted in FIG. 26.

FIGS. 28A 28C are diagrammatic views illustrating an embodiment of an operational cycle of the ammunition belt feeding mechanism depicted in FIG. 26.

DETAILED DESCRIPTION

An embodiment of a firearm 10 including an upper receiver assembly 12 and having an ammunition belt 14 attached to the upper receiver assembly 12 is depicted in FIG. 1A. The firearm 10 is depicted in FIG. 1B having an ammunition magazine 16 attached to a lower receiver assembly 18 of the firearm 10. As depicted in FIG. 1C, the lower receiver assembly 18 includes a lower receiver body 19 having a trigger group 20 mounted thereon. The trigger group 20 comprises a trigger 22, a hammer 24, a disconnect 26, and an automatic sear 28.

A lower receiver assembly from an M-16 type firearm illustrates an example of the lower receiver assembly 18. M-16 type firearms are manufacturer configured for receiving ammunition exclusively from an ammunition magazine attached to their lower receiver assembly. The upper and lower receiver assemblies of an unmodified M-16 type firearm illustrate examples of as-manufactured original equipment manufacturer (OEM) upper and lower receiver assemblies.

It is advantageous to enable a firearm configured by its manufacturer for receiving ammunition exclusively from an ammunition magazine to also receive ammunition from an ammunition belt. For firearms having a registerable lower receiver assembly, it is particularly advantageous for the an upper receiver assembly capable of supplying ammunition from an ammunition belt to be mountable on an unmodified lower receiver assembly. In this manner, such an upper receiver assembly may be legally fitted to the registerable lower receiver assembly by parties other than the manufacturer.

An embodiment of an operational cycle of the firearm 10 for ammunition supplied from the magazine 16 is depicted in FIGS. 2A 2H. When the firearm 10 has a selector switch (not depicted) set for semi-automatic fire, the operational cycle begins with a chambered round 30 in a firing chamber 31 and the hammer 24 in a cocked position H1 with a lower hammer notch 24a engaged with a trigger sear 22a, as depicted in FIG. 2A. Each round of ammunition includes a cartridge and a bullet. The chambered round 30 includes a bullet 30a that is projected down a barrel 33 when the chambered round 30 is fired.

As the trigger 22 is pulled from a ready position R, FIG. 2A, to a firing position F, FIG. 2B, the hammer 24 is released and rotates forward, striking a firing pin 32 thereby causing the chambered round 30 to be fired and a bullet 30a, FIG. 2A, to be projected down a barrel 33. The firing pin 32 is mounted on a bolt 34 and the bolt 34 is mounted on a bolt carrier 36. A bolt carrier group comprises the bolt 34 and the bolt carrier 36. As the bullet 30a travels down the barrel 33, combustion gas 38 creates pressure in the barrel 33 between the bullet 30a and the chambered round 30, FIG. 2B. The pressure associated with the combustion gas 38 facilitates ejection of the chambered round 30 and chambering of an unfired round 40 via a conventional gas-driven bolt actuating technique, such as that used in Colt M-16 type firearms, or an embodiment of a piston-driven bolt actuating technique as disclosed herein.

Regardless of the bolt actuating technique used, firing of the chambered round 30 results in the bolt 34 and the bolt carrier 36 being moved in a rearward direction away from the barrel 33 from a closed position C, FIG. 2C, toward an open position O, FIG. 2D. Accordingly, the bolt carrier group and all of its components are moved from the closed position C toward the open position O. In response to the bolt carrier 36 being moved in the rearward direction, the bolt 34 is rotated such that lugs of the bolt 34 are unlocked from corresponding lugs of a barrel extension. In this manner, the bolt 34 is free to move, as a component of the bolt carrier group, from the closed position C toward the open position O. As the bolt 34 and bolt carrier 36 move in the rearward direction, the chambered round 30 is withdrawn from the firing chamber 31 and is ejected from the firearm 10 through an ejection port. The movement of the bolt carrier 36 in the rearward direction also returns the hammer 24 from a firing H2, FIG. 2B, to the cocked position H1', FIG. 2D, with an upper hammer notch 24b engaged with a disconnect hook 26b.

The rearward movement of the bolt carrier 36, and consequently the bolt 34, is arrested by a buffer assembly 41, FIG. 2C. The buffer assembly 41 includes an action spring 41a that is compressed by the bolt carrier 36 during its rearward movement. As depicted in FIG. 2D, the compressed action spring 41a forces the bolt carrier group in a forward direction towards the closed position C, towards the barrel 33. Upon moving forward toward the closed position C, the bolt 34 engages the unfired round 40 in the magazine 16 and thrusts the unfired round 40 into the firing chamber 31, FIG. 2E. As the bolt carrier 36 and the bolt 34 continue to move towards the closed position C, the lugs of the bolt 34 enter the bolt extension of the barrel 33 and the bolt 34 engages a face of the barrel extension. An ejector pin is depressed against the unfired round 40 and an extractor snaps into an extracting groove of the unfired round 40, facilitating ejection after the unfired round 40 is fired.

While the bolt 34 is engaged with the face of the barrel extension, the bolt carrier 36 continues to move towards the closed position C. As the bolt carrier 36 continues to move in the forward direction toward the closed position C, the bolt 34 is rotated such that the lugs of the bolt 34 are locked relative to the lugs of the barrel extension. The bolt carrier group is said to be in the closed position C when the lugs of the bolt 34 are locked relative to the lugs of the barrel extension. Mechanisms and techniques for rotating the bolt 34 such that the lugs can be locked and unlocked from the lugs of the barrel extension are disclosed below in greater detail.

When the selector switch is set to the semi-automatic position, firing the unfired round 40 requires releasing and pulling the trigger 22 for each fired round. When the trigger is released, a trigger spring 22c, FIG. 2E, causes the trigger 22 to move from the firing position F to the ready position R, FIG. 2F. Releasing the trigger 22 also causes the upper hammer notch 24b to disengage from the disconnect hook 26b. In this manner, the hammer 24 is released, allowing it to move to the cocked position H1, FIG. 2F, with the lower hammer notch 24a engaged with the trigger sear 22a. The firearm is now ready to fire the unfired round 40.

Moving the selector switch (not depicted) to the automatic position permits the firearm to operate in a fully automatic mode. With the selector switch set in the automatic position, FIG. 2G, a lower edge 28a of the automatic sear 28 engages a top outside hammer notch 24c during the rearward movement of the bolt carrier 36. This action holds the hammer 24 in the automatic cocked position H1''. During the forward movement of the bolt carrier 36, FIG. 2H, the bolt carrier 36 strikes an upper edge 28b of the automatic sear 28, releasing the automatic sear 28 from the hammer 24 thereby permitting the hammer 24 to strike the firing pin 32 and fire the unfired round 40. In this manner, rounds of ammunition will be automatically fired, ejected and chambered until the trigger 22 is released or all of the rounds are used.

As depicted in FIGS. 3A and 3B, the upper receiver assembly 12 includes an upper receiver body 42. A piston tube assembly 44 is attached to the upper receiver body 42. The piston tube assembly 44 includes a piston tube 46 having a tappet assembly 47, FIG. 3B, movably mounted thereon. The piston tube 46 includes a first end 46a that is mounted in a piston tube receptacle 48 of the upper receiver body 42. A press pin 50 extends through the upper receiver body 42 and a corresponding hole in the piston tube 46, securing the piston tube 46 in place relative to the upper receiver body 42.

The tappet assembly 47, FIG. 3B, includes a yoke 47a that rides on the piston tube 46 and a tappet rod 47b attached to the yoke 47a. The tappet rod 47b extends from the yoke 47a through the upper receiver body 42 into contact with a bolt carrier lug 36a, FIG. 7 that is movably mounted on the upper receiver body 42. The tappet rod 47b and a charging member 51 extend along substantially parallel longitudinal axes.

A barrel assembly 52, FIGS. 3 4, is configured for being attached to the upper receiver assembly 12. The barrel assembly 52 includes the barrel 33 (discussed above in reference to FIGS. 2A 2H) and a gas block 56, FIGS. 3A and 4, attached to the barrel 33. A pressure regulator 58, FIGS. 3A and 4, is mounted in the gas block 56. A first end 33a of the barrel 33 is configured for being received in a barrel receptacle 60, FIG. 3B, of the upper receiver body 42. A nipple 58a, FIG. 4, of the pressure regulator 58 is configured for being received in a second end 46b, FIG. 3A, of the piston tube 46.

As depicted in FIG. 3B, the upper receiver assembly 12 includes a barrel retention mechanism 62 pivotally mounted thereon for securing the barrel assembly 52 to the upper receiver body 42. The barrel retention mechanism 62 is biased by a spring 62a to a locked position L1. By depressing a release lever portion 62b of the barrel retention mechanism 62, a pin extending through the upper receiver body 42 is disengaged from the barrel 33, permitting the barrel 33 to be withdrawn from the barrel receptacle 60.

Referring to FIGS. 5A and 5B, the piston tube assembly 44 includes an operating rod 64 movably mounted in a bore 46c of the piston tube 46. A piston 66 is attached at a first end 64a of the operating rod 64. The yoke 47a is attached to the operating rod 64 by a pin 68. The pin 68 extends through the yoke 47a and the operating rod 64. The piston tube 46 has opposing elongated slots 46d through which the pin 68 extends, allowing the yoke 47a and the operating rod 64 to move along the longitudinal axis of the piston tube 46. A return spring 70 is captured in the bore 46c of the piston tube 46 between a second end 64b of the operating rod 64 and a closed end portion 46e of the piston tube 46. The return spring 70 biases the operating rod 64 to a static position S.

A passage 72 extends through the barrel 33 to a pressure regulator receptacle 56a of the gas block 56. The pressure regulator 58 depicted in FIGS. 5A and 5B is an adjustable pressure regulator including a plurality of orifices 58b extending between an outer surface 58c and a gas communication passage 58d of the pressure regulator 58. During operating of the firearm 10, one of the orifices 58b is aligned with the passage 72.

When a chambered round of ammunition in the firearm 10 is fired, FIG. 5B, a bullet 74 travels down the bore of the barrel 33. Firing of the chambered round of ammunition produces combustion gases creating pressure in the bore of the barrel 33 between the bullet 74 and the cartridge of the fired round of ammunition. When the bullet travels past the passage 72, a portion of the combustion gas travels through the passage 72 and the pressure regulator 58 into the bore 46a of the piston tube 46. In doing so, a face of the piston 66 is exposed to pressure associated with the combustion gases. The pressure drives the piston 66, and consequently the operating rod 64 from the static position S to a displaced position D, compressing the return spring 70.

One or more gas exhaust ports 76 are formed in the piston tube 46 adjacent to the displaced position D for venting the combustion gas to the ambient environment. Upon venting the combustion gases, the return spring 70 biases the piston 66 and operating rod 64 towards the static position S. A vent hole 78 may be provided in the piston tube 46 for relieving movement-induced pressure behind the piston 66.

The pressure regulator 58 may be rotated for individually aligning a particular one of the orifices 58b with the passage 72. By each of the orifices 58b being a different size, the amount of pressure exerted on the piston 66 can be selectively varied. In many situations, it will be advantageous to adjust the pressure that is exerted on the piston. For example, to maintain a desired level of performance of the firearm 10 as components of the firearm 10 wear, as the components become fouled from the combustion gas or when the firearm is used in different ambient environments, it is advantageous to be able to compensate for such situations. However, in some applications, the pressure regulator 58 may have only one orifice 58b, resulting in the pressure regulator being non-adjustable. In the case of a non-adjustable pressure regulator, the size of the orifice 58b will be determined based on a compromise for intended and predicted conditions.

As depicted in FIGS. 6A and 6B, displacement of the operating rod 64 from the static position S to the displaced position D results in a corresponding displacement of the yoke 47a. The tappet rod 47b is engaged with the bolt carrier lug 36a of the bolt carrier 36. The bolt carrier lug 36a is constrained to forward and rearward movement in a bolt carrier lug channel 42b, FIG. 7, of the upper receiver body 42. Accordingly, the displacement of the operating rod 64 also results in a corresponding displacement of the bolt carrier 36. The displacement of the bolt carrier 36 that is associated with the displacement of the operating rod 64 is an initial displacement of the bolt carrier 36. Due to inertia associated with the speed at which the operating rod 64 is displaced, the bolt carrier 36 continues to travel after the operating rod 64 reached its maximum displacement. Thus, the overall displacement of the bolt carrier 36 is greater than the displacement of the operating rod 64. Accordingly, the upper receiver assembly is said to be gas energized and piston driven.

Implementation of embodiments of the piston tube assembly 44 and tappet assembly 47 are advantageous. One advantage is that the piston tube assembly 44 and the tappet assembly 47 transfer the energy associated with the combustion gases more efficiently to the bolt carrier 36. Because the piston 66 is mechanically coupled through the operating rod 64 and the tappet assembly to the bolt carrier 36, the length over which the combustion gases must travel to build sufficient pressure to energize the bolt carrier 36 is significantly reduced. Accordingly, the length over which compression of the combustion gas occurs is significantly reduced. By reducing the length over which compression of the combustion gases occurs and by mechanically coupling the piston 66 to the bolt carrier 36, the bolt 34 and the bolt carrier 36 are more efficiently moved from the closed position towards the open position.

Another advantage associated with the piston tube assembly 44 and the tappet assembly 47 relates to fouling of the firearm associated with the combustion gases. Conventional gas driven bolt actuation mechanisms result in fouling of the upper and lower receiver assemblies of a firearm. Fouling of the firearm can result in degraded performance of the firearm and, if not timely addressed, malfunction of the firearm. Because embodiments of the piston tube assembly 44 and the tappet assembly 47 disclosed herein preclude the need to route combustion gases to the upper receiver assembly 12, the potential for the combustion gases to foul of the upper receiver assembly 12 and the lower receiver assembly 18 is greatly reduced.

The piston tube assembly 44 and the pressure regulator 58 are susceptible to being fouled by the combustion gases. However, when these components require cleaning, they may be quickly and easily detached from the upper receiver assembly 12 to facilitate cleaning. It is a significant advantage that when fouled, the piston tube assembly 44 and the pressure regulator 58 can be detached, cleaned and re-attached to the upper receiver assembly 12 in a timely manner. Furthermore, because the piston tube assembly 44 is a unitary assembly, it can be quickly and easily replaced. In situations such as military combat, it may be desirable and advantageous to replace the piston tube assembly 44 rather than clean it.

Yet another advantage associated with embodiments of the piston tube assembly 44 disclosed herein is the location at which the combustion gases are vented. In some conventional firearms such as M-16 type firearms, during firing of the firearm, the combustion gases are vented from the firearm very close to the firearm operator's face. As a result, the vision and respiration of the operator may be impaired. Implementation of an embodiment of the piston tube assembly 44 disclosed herein results in the combustion gases being vented at a location that significantly reduces the potential for the vision and respiration of the operator to be impaired.

The design of this piston tube assembly 44 aIlows the tappet to contact a portion of the bolt carrier 36 that is not directly in line with the piston 66. In this manner, a bipod mounting bracket may be fitted to the piston tube 46 in a manner in which the bipod attachment does not hinder removal of the barrel 33. In conventional configurations, the bipod mounting bracket is attached to a barrel of a conventional weapon, thus making the barrel of such conventional weapon difficult to remove with the weapon supported on the bipod. Furthermore, this results in each such barrel having the added weight of a bipod mounting bracket.

Referring to FIG. 7, the tappet rod 47b engages a first surface 36a' of the bolt carrier lug 36a. The charging member 51 includes a charging member lug 51a that engages a second surface 36a'' of the bolt carrier lug 36a. The charging member 51 includes flanges 51b that are each received by a respective groove 42a of the upper receiver body 42, thus allowing the charging member 51 to be displaced relative to the upper receiver body 42. The configuration and orientation of the bolt carrier lug 36a, the tappet rod 47b and the charging member lug 51a permits the bolt carrier 36 to be manually displaced by pulling on a charging handle 51c of the charging member 51.

Referring to FIGS. 8 10, a bolt catch 80 is pivotally attached to the lower receiver body 19 at a pivot pin 81. The bolt catch 80 includes an upper leg 80a and a lower leg 80b. The pivot pin 81 is positioned between the upper leg 80a and the lower leg 80b. A contact pin 82 is mounted in a recess 84 of the upper leg 80a and engages a contact surface 51c, FIGS. 8 and 9, of the charging member 51. A first spring 86 is disposed in the recess 84, biasing the contact pin 82 away from the upper leg 80a. A second spring 88 is mounted between the lower leg 80b and the lower receiver body 19. The first and the second springs 86, 88 have respective spring rates such that the bolt catch 80 is biased to an unlocked position U, FIG. 9.

The bolt 34 and the bolt carrier 36 may be manually moved from the closed position C to the open position O, FIG. 8, by moving the charging member 51 in a rearward direction. When the charging member 51 is moved in the rearward direction, the contact pin 82 encounters a contoured portion 51d of the charging member 51. The position of the contoured portion 51d relative to the bolt 34 and the profile of the contoured portion 51d result in the bolt catch 80 being moved by the charging member 51 to a locked position L, FIG. 10, when the bolt 34 is moved to the open position O.

As mentioned above in reference to FIG. 2C, the bolt 34 and bolt carrier 36 are biased in a forward direction toward the closed position C by the action spring 41a. Accordingly, after the charging member 51 is moved in the rearward direction sufficiently, the bolt 34 is urged in the forward direction against a locking leg 80c by the action spring 41a as the chargin member 51 is moved in the forward direction. In this manner, the locking leg 80c engages a face 34a of the bolt 34, thus holding the bolt 34 and the bolt carrier 36 in the open position O. By manually pressing the upper leg 80a, the bolt catch 80 is moved to the unlocked position U, disengaging the locking leg 80c from the face 34a of the bolt 34, thereby allowing the bolt 34 and bolt carrier 36 to return to the closed position C under the influence of the action spring 41a.

Implementation of an embodiment of the bolt catch 80 disclosed herein simplifies the operation of locking the bolt of a firearm in the open position. Many conventional bolt catches, such as that used on M-16 type firearms, require manual manipulation of the bolt catch to lock the bolt in the open position. In situations such as military combat, it is advantageous and desirable to preclude the need to manually manipulate the bolt catch when locking the bolt in the open position. Embodiments of the bolt catch 80 disclosed herein allow the bolt 34 to be locked in the open position O without requiring manual manipulation of the bolt catch 80. The bolt catch 80 described herein, can also be moved automatically from an unlocked position U to a locked position L, by action of a magazine follower from an empty magazine upon a protruding tang (not shown) on the bolt catch 80. This facilitates the rapid reloading of the weapon when used with ammunition magazines.

As mentioned above in reference to FIG. 2E, moving the bolt 34 and the bolt carrier 36 between the open position O and the closed position C includes rotating the bolt 34 for unlocking and locking, respectively, the lugs of the bolt 34 from corresponding lugs of the barrel extension. FIGS. 11 13 show an embodiment of a mechanism for rotating lugs 34b of the bolt 34 between the unlocked position U' and the locked position L'. A cam pin 90 is attached to the bolt 34. The cam pin 90 is positioned in a cam pin hole 34c of the bolt 34, FIG. 13. The firing pin 32 extends through a firing pin hole 34d of the bolt 34 and a firing pin hole 90a of the cam pin 90. The cam pin 90 is captured in a cam slot 92 of the bolt carrier 36, FIGS. 11 and 12. When the bolt 34 is rotated such that the lugs 34b, FIG. 11, of the bolt 34 are unlocked from the lugs of the barrel extension, the cam pin 90 is positioned in a first region 92a of the cam slot 92. When the lugs 34b are unlocked from the lugs of the barrel extension, a retaining arm 94 is engaged with the cam pin 90 for retaining the cam pin 90 in the first region 92a of the cam slot 92. When the bolt 34 is moved toward the closed position and the bolt 34 engages the barrel extension, a ramp 94a of the retaining member 94, FIG. 11, engages a stationary ramp, thereby pivoting the retaining member 94 for allowing the cam pin 90 to move into a second region 92b of the cam slot 92. A feed tray 96 is a suitable stationary component to which the stationary ramp may be attached. When the cam pin 90 is in the second region 92b of the cam slot 92, the lugs 34b of the bolt 34 are in the locked position relative to the lugs of the barrel extension.

Another embodiment of a mechanism for rotating the lugs 34b of the bolt 34 between the unlocked position and the locked position is depicted in FIGS. 14 17. In this embodiment, the cam pin 90 extends through the cam pin slot 92 and into the bolt carrier lug channel 42b of the upper receiver body 42. In this manner, the cam pin 90 is constrained to follow a path defined by the bolt carrier lug channel 42b. When the bolt 34 is in the unlocked position U', FIGS. 14 and 15, the cam pin 90 is positioned in the first region 92a of the cam slot 92 and is free to travel in the forward and rearward directions along the length of the bolt carrier lug channel 42b. When the face 34a of the bolt 34 contacts the barrel extension, the bolt carrier 36 continues its forward movement. The continued forward movement of the bolt carrier 36 results in the cam pin 90 rotating in the cam slot 92 to the second region of the cam pin slot 92b, locking the lugs 34b of the bolt 34 relative to the lugs of the barrel extension. The bolt 34 is now in the locked position L'. A relief 42c is formed adjacent to the bolt carrier lug channel 42b for receiving the cam pin 90 when the bolt 34 is in the locked position L'. The bolt carrier lug 36a has a sufficient length such that it cannot rotate into the relief 42c. A bolt carrier assembly comprises the bolt 34 and the bolt carrier 36.

Referring to FIGS. 18 25, an ammunition belt feeding assembly 100 is mounted on the upper receiver body 42 of the upper receiver assembly 12. The ammunition belt feeding assembly 100 and the upper receiver assembly 12 comprise a belt feed receiver system. The ammunition belt feeding assembly 100 includes a top cover 102 mounted adjacent to the feed tray 96. The top cover 102 and the feed tray 96 are pivotally attached to the upper receiver body 42 through a plurality of bosses 104. A latch mechanism releasably engages a mounting bracket 106, FIG. 20, that is attached to the upper receiver body 42. The feed tray 96 includes a belt channel 96a and a link ejection channel 96b. A feed pin 108, FIG. 20, is attached to the bolt carrier 36 and extends through a feed pin channel 110 in the upper receiver body 42. The feed pin 108 moves in unison with the bolt carrier 36 along the feed pin channel 110.

The ammunition belt feeding assembly 100 includes a two-stage cam-lever type ammunition belt feeding mechanism 112, FIGS. 21A 21B, attached to the top cover 102. It is contemplated that other types of cam-lever type ammunition belt feeding mechanisms, such as a single-stage cam-lever type, may be implemented with the upper receiver assembly 12 disclosed herein. It is beneficial for a cam-lever type ammunition belt feeding mechanism to be configured to limit adverse affects associated with acceleration and deceleration of the ammunition belt 114.

Referring to FIGS. 21 25, a cam lever 113 is pivotally attached to the top cover 102 at a pivot pin 116. The cam lever 113 includes a cam lever slot 118 having a dwell region 118a and a feed region 118b. The feed pin 108 is received in the cam lever slot 118. The cam lever 118 is engaged with a feed link 120 for pivoting the feed link 120 about a pivot pin 122. A first slide member 124 and a second slide member 126 are attached to the feed link 120 at respective feed link pins 124a, 126a. Primary feed pawls 128 are pivotally attached to the first slide member 124 and a secondary feed pawl 130 is pivotally attached to the second slide member 126. The first slide member 124 and the second slide member 126 include respective guide slots 124b, 126b. A guide pin 132 is attached to the top cover 102 and engages the first and the second slide members 124, 126 at the respective guide slots 124b, 126b.

Still referring to FIGS. 21 25, the ammunition belt feeding mechanism 112 operates in two distinct phases and feeds an ammunition belt 114 through the belt channel 96a towards the link ejection channel 96b. When the bolt and bolt carrier begins their forward travel toward the closed position, the feed pin 108 moves in a dwell region 118a of the cam lever slot 118 from a first dwell position D1 to a second dwell position D2, FIG. 21A. The operation and travel of the bolt and carrier are discussed above. The feed pin 108 is in the dwell region 118a of the cam lever slot 118 during a first portion of the forward travel of the bolt and the bolt carrier. While the feed pin 108 is in the dwell region 118a of the cam lever slot 118, the first and the second slide members 124, 126 are stationary, FIGS. 25A and 25B. Thus, the primary and the secondary feed pawls 128, 130 remain stationary while the feed pin 108 is in the dwell region 118a of the cam lever slot 118. As depicted in FIGS. 25A and 25B, a first round 114a at a chambering position C1 is chambered while the feed pin 108 is in the dwell region 118a of the cam lever slot 118. The first round 114a is now in a chambered position C2, as depicted in FIG. 25B, ready for being fired.

During the second portion of the forward travel of the bolt and the bolt carrier, the feed pin 108 reaches the feed region 118b of the cam lever slot 118 and travels from the second dwell position D2 to a feed position F, FIG. 21B. As a result of the feed region 118b being skewed with respect to the dwell region 118a, the cam lever 113 pivots from a static position S', FIG. 21A, to a displaced position D', FIG. 21B, as the feed pin 108 travels from the second dwell position D2 to the feed position F. The pivoting action of the cam lever 113 pivots the feed link 120. Accordingly, because the first and the second slide members 124, 126 are pinned to the feed link 120 on opposing sides of the pivot pin 122, the primary feed pawls 128 move towards the chambering position C1 and the secondary feed pawl 130 moves away from the chambering position C1, FIGS. 25C and 25D.

During movement towards the chambering position C1, the primary feed pawls 128 advance the second round 114b towards the chambering position C1 and into engagement with a cartridge follower 134. The cartridge follower 134, FIG. 25D, exerts a downward force on the cartridge of the second round 114b, biasing the second round 114b towards the chambered position C2. During movement away from the chambering position C1, the secondary feed pawl 130 ratchets over the cartridge of the second round 114b, FIG. 25C. In this manner, when the feed pin 108 reached the feed position F, the second round 114b is advanced towards the chambering position C1 and all of the feed pawls 128, 130 are positioned between the second round 114b and a third round 114c, FIG. 25D.

The primary and the secondary feed pawls 128, 130 may be biased to an engagement position E, FIG. 25D, by respective springs, by gravity, or any other suitable means for being automatically returned to the engagement position E after being ratcheted over a cartridge. The travel of the feed pin 108 from the second dwell position D2 to the feed position F results in the second round 114b being advanced approximately a first half of a pitch P of the ammunition belt 114. The bolt attains its closed position when the feed pin 108 reaches the feed position F.

After the first round 114a is fired, the bolt and the bolt carrier travel rearward towards the open position. The operation and travel of the bolt is discussed above. Accordingly, the feed pin 108 travels from the feed position F towards the second dwell position D2. As the feed pin 108 travels from the feed position F toward the second dwell position D2, the cam lever 113 pivots from the displaced position D' to the static position S'. As the feed pin 108 travels from the displaced position D' to the static position S', the primary feed pawls 128 move away from the chambering position C1 and the secondary feed pawl 130 moves towards the chambering position C1, FIGS. 25D and 25E.

During movement towards the chambering position C1, the secondary feed pawl 130 advance the second round 114b to the chambering position C1. As the secondary feed pawl 130 advances the second round 114b towards the chambering position C1, the cartridge follower 134 exerts additional force on the cartridge of the second round 114b, further biasing the second round 114b towards the chambered position C2. During movement away from the chambering position C1, the primary feed pawls 128 ratchet over the cartridge of the third round 114c. The second round 114b is now positioned at the chambering position C1, FIG. 25E. The secondary feed pawl 130 is now positioned between the second round 114b and the third round 114c. The primary feed pawls 128 are now positioned between the third round 114c and a fourth round 114d. The travel of the feed pin 108 from the feed position F to the second dwell position D2 results in the second round 114b being advanced a second half of the pitch P of the ammunition belt 114. The feed pawls 128, 130 do not move as the feed pin 108 travels from the second dwell position D2 back to the first dwell position D1.

Referring to FIGS. 26 28, an embodiment of a sprocket type ammunition belt feeding mechanism 212 includes a feed sprocket 215 and a drive shaft assembly 216 coupled to the feed sprocket 215. As depicted in FIG. 26, a mounting shaft 213 extends through the feed sprocket 215 and drive shaft assembly 216, permitting the feed sprocket 215 and the drive shaft assembly 216 to rotate relative to a top cover 202 of an ammunition belt feeding assembly. The mounting shaft 213 is attached to the top cover 202 via a first and a second mounting bracket 217a, 217b. At least one of the mounting brackets 217a, 217b is removable from the top cover 202 for permitting the ammunition belt feeding mechanism 212 to be detached from the top cover 202.

In an alternated embodiment (not shown), the feed sprocket 215 and the drive shaft assembly 216 are mounted on a common axle shaft. The common axle shaft extends through the feed assembly and top cover ends. The axle shaft is secured by a cross-pin through the cover and radius of the axle shaft on one end of the cover.

The drive shaft assembly 216, FIGS. 26 and 27, includes a drive shaft 218 and a drive sleeve 220 mounted in a counter-bored end 218a of the drive shaft 218. The feed sprocket 215 includes a drive hub 215a that is fixedly attached to the feed sprocket 215 such that the feed sprocket 215 is precluded from rotating relative to the drive hub 215a. The drive sleeve 220 includes a plurality of ribs 220a thereon that mate with corresponding grooves 218b of the drive shaft 218 such that the drive sleeve 220 is precluded from rotating relative to the drive shaft 218. A spring 222, FIG. 27, is mounted between the drive sleeve 220 and the drive shaft 218 for biasing the drive sleeve 220 into engagement with the drive hub 215a of the feed sprocket 215, FIG. 26. The drive sleeve 220 and the drive hub 215a have mating tapered teeth. Accordingly, the drive shaft 218 can rotate relative to the feed sprocket 215 in only one direction.

An operational cycle of the ammunition belt feeding mechanism 212 begins with a first round 214a being stripped from the ammunition belt 214 at the chambering position C1 by the bolt and chambered into the firing chamber, FIG. 28A. The first round 214a is now at the chambered position C2. After the first round 214a is fired, the bolt and bolt carrier travel from the closed position toward the open position. The drive shaft 218 includes a spiral drive slot 218c that receives the feed pin of the bolt carrier (discussed above). The profile of the drive slot 218c may be configured for minimize adverse affects associated with acceleration and deceleration of the ammunition belt 214.

As the bolt carrier travels towards the open position, the feed pin travels in the drive slot 218c of the drive shaft 218, rotating the drive shaft 218 and the feed sprocket 215 from the static position S'', FIG. 28A, to the rotated position R'', FIG. 28B. The profile of the drive slot 218c is configured for rotating the drive shaft 218 through an angular displacement corresponding to the pitch P of the ammunition belt 214. Accordingly, a second round 214b is advanced to the chambering position C1 during rotation of the drive shaft 218 from the static position S'' to the rotated position R''. The cartridge of the first round 214a is withdrawn from the firing chamber and is ejected from the firearm as the bolt carrier travels from the closed position towards the open position.

An action spring (discussed above) arrests the travel of the bolt carrier toward the open position and urges the bolt carrier towards the closed position. As the bolt carrier travels from the open position toward the closed position, the drive shaft 218 rotates from the rotated position R'' back to the static position S'', FIG. 28C. An anti-reverse member 224 is engaged with the feed sprocket 215. The anti-reverse member 224 provides a retention force on the feed sprocket 215, holding the feed sprocket 215 stationary while the drive shaft 218 rotates back to the static position S''.

In the preceding detailed description, reference has been made to the accompanying drawings which form a part hereof, and in which are depicted by way of illustration specific embodiments in which the invention may be practiced. These embodiments, and certain variants thereof, have been described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that other suitable embodiments may be utilized and that logical, mechanical, chemical and electrical changes may be made without departing from the spirit or scope of the invention. For example, functional blocks depicted in the figures could be further combined or divided in any manner without departing from the spirit or scope of the invention. To avoid unnecessary detail, the description omits certain information known to those skilled in the art. The preceding detailed description is, therefore, not intended to be limited to the specific forms set forth herein, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents, as can be reasonably included within the spirit and scope of the appended claims. For more information go to WWW.GAPATENTS.COM or WWW.GOOGLE.COM.

Wednesday, August 26, 2009

United States Patent 7,032,396
WWW.USPTO.GOV
Wood, et al.
April 25, 2006

Cooling method for controlled high speed chilling or freezing

Abstract

A cooling method for controlled high speed chilling or freezing is disclosed. Cooling fluid is circulated by a submersed circulator, such as a motor, at a substantially constant velocity past a substance to be cooled . The velocity of fluid flow is maintained despite changes in the viscosity of the cooling fluid, by either increasing or decreasing the amount of torque supplied by the motor. The cooling fluid is cooled to a desired temperature by circulating the fluid past a multi-path heat exchanging coil connected to a refrigeration system. An optimal cooling fluid temperature for a variety of applications is in the range of about -24.degree. C. to -26.degree. C., resulting in significant efficiency gains over conventional cooling processes.
Inventors: Wood; Brian (Lubbock, TX), Cassell; Allan J. (West Heidelberg, AU)
Assignee: Supachill Technologies Pty. Ltd. (AU)
Appl. No.: 10/276,440
Filed: May 16, 2001
PCT Filed: May 16, 2001
PCT No.: PCT/US01/15821
371(c)(1),(2),(4) Date: April 09, 2003
PCT Pub. No.: WO02/14753
PCT Pub. Date: February 21, 2002
Related U.S. Patent Documents

Application Number Filing Date Patent Number Issue Date
60205635 May., 2000

Current U.S. Class: 62/185 ; 62/434
Current International Class: F25D 17/02 (20060101)
Field of Search: 62/185,434,177,430,62,76,114,201,203,204,205
References Cited [Referenced By]
U.S. Patent Documents

4888956 December 1989 le Roux Murray
5003787 April 1991 Zlobinsky
5191773 March 1993 Cassell
6519954 February 2003 Prien et al.
2003/0154729 August 2003 Prien et al.
Primary Examiner: Jiang; Chen Wen
Attorney, Agent or Firm: Galasso; Raymond M. Galasso & Associates, L.P.
WWW.GAPATENTS.COM

Parent Case Text


CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. .sctn. 119 of U.S. provisional patent application Ser. No. 60/205,635, entitled Cooling Method For Controlled High Speed Chilling or Freezing, which was filed on May 18, 2000. This application claims benefit under 35 U.S.C. .sctn. 365 of PCT international application Ser. No. PCT/US01/15821, entitled Cooling Method For Controlled High Speed Chilling or Freezing, which was filed May 16, 2001 now abandoned.
Claims


What is claimed is:

1. A method for cooling substances comprising: circulating cooling fluid past a substance to be cooled; and controlling the circulation of the cooling fluid such that the cooling fluid is circulated at a substantially constant predetermined velocity past the substance to be cooled by associating the circulation with a change in cooling fluid viscosity so as to maintain circulation of the cooling fluid at the substantially constant predetermined velocity even as viscosity of the cooling fluid changes.

2. The method as in claim 1, further comprising circulating the cooling fluid past a heat exchanging coil submersed in the cooling fluid, and wherein the heat exchanging coil is capable of removing the same amount of heat from the cooling fluid as the amount of heat the cooling fluid removes from the substance.

3. The method as in claim 2, wherein the heat exchanging coil is a multi-path coil.

4. The method as in claim 2, wherein the size of the heat exchanging coil is directly related to an area through which the cooling fluid is circulated, wherein the area is about 24 inches wide and 48 inches deep.

5. The method as in claim 2, further comprising cooling the heat exchanging coil with a refrigeration unit substantially matching load requirements of the heat exchanging coil.

6. The method as in claim 1, further comprising maintaining the cooling fluid at a temperature of between about -24 degrees centigrade and -26 degrees centigrade.

7. The method as in claim 1, wherein at least one circulator is used to circulate the cooling fluid, and wherein controlling the circulation comprises controlling the circulator to produce a desired circulation rate.

8. The method as in claim 7, wherein the circulator comprises: a motor; and an impeller rotatably coupled to the motor such that the impeller rotates to circulate the cooling fluid.

9. The method as in claim 7, wherein an additional circulator is employed for each foot of cooling fluid to be circulated past an area not greater than about 24 inches wide and 48 inches deep.

10. The method as in claim 1, wherein the circulation rate is about 35 liters per minute per foot of cooling fluid through an area not greater than about 24 inches wide and 48 inches deep.

11. The method as in claim 1, wherein the cooling fluid is a solute.

12. The method as in claim 1, further comprising freezing the substance at a controlled freezing rate.

13. The method as in claim 12, wherein controlling the freezing rate comprises controlling the substantially constant predetermined circulation rate of the cooling fluid.

14. The method as in claim 12, wherein controlling the freezing rate comprises controlling the velocity of cooling fluid flowing past the substance to be cooled.

15. The method as in claim 12, wherein controlling the freezing rate comprises controlling the temperature of the cooling fluid.

16. The method as in claim 1, further comprising cooling the substance at a controlled cooling rate.

17. The method as in claim 16, wherein controlling the cooling rate comprises controlling the substantially constant predetermined circulation rate of the cooling fluid.

18. The method as in claim 16, wherein controlling the cooling rate comprises controlling the velocity of cooling fluid flowing past the substance to be cooled.

19. The method as in claim 16, wherein controlling the cooling rate comprises controlling the temperature of the cooling fluid such that the temperature differential throughout the cooling fluid is maintained within about 0.5 degrees centigrade.

20. A method for cooling substances comprising: circulating cooling fluid past a substance to be cooled using at least one circulator; and controlling the at least one circulator to maintain a substantially constant predetermined velocity of cooling fluid circulated past the substance to be cooled, wherein said controlling the at least one circulator includes changing at least one operating parameter of the at least one circulator while the cooling fluid is being circulated in response to associating a change in at least one operating parameter of the at least one circulator with a change in cooling fluid viscosity thereby maintaining circulation of the cooling fluid at the substantially constant predetermined velocity even as viscosity of the cooling fluid changes.

21. The method as in claim 20, further comprising circulating the cooling fluid, at the substantially predetermined velocity, past a heat exchanging coil submersed in the cooling fluid, and wherein the heat exchanging coil is capable of removing at least the same amount of heat from the cooling fluid as the amount of heat the cooling fluid removes from the substance.

22. The method as in claim 21, wherein the heat exchanging coil is a multi-path coil.

23. The method as in claim 21, wherein the size of the heat exchanging coil is directly related to an area through which the cooling fluid is circulated, wherein the area is about 24 inches wide by 48 inches deep.

24. The method as in claim 21, further comprising cooling the heat exchanging coil with a refrigeration unit substantially matching load requirements of the heat exchanging coil.

25. The method as in claim 20, further comprising maintaining the cooling fluid at a temperature of between about -24 degrees centigrade and -26 degrees centigrade.

26. The method as in claim 20, wherein controlling the at least one circulator comprises adjusting the force exerted by the circulator on the cooling fluid such that the substantially constant predetermined velocity of the cooling fluid circulated past the substance to be cooled is maintained.

27. The method as in claim 20, wherein the circulation rate is about 35 liters per minute per foot of cooling fluid through an area not greater than about 24 inches wide and 48 inches deep.

28. The method as in claim 20, wherein the circulator comprises: a motor; and an impeller rotatably coupled to the motor such that the impeller rotates to circulate the cooling fluid.

29. The method as in claim 20, wherein an additional circulator is employed for each foot of cooling fluid to be circulated past an area not greater than about 24 inches wide and 48 inches deep.

30. The method as in claim 20, wherein the cooling fluid is a solute.

31. The method as in claim 20, further comprising freezing the substance at a controlled freezing rate.

32. The method as in claim 31, wherein controlling the freezing rate comprises controlling the substantially constant predetermined velocity of the cooling fluid circulated past the substance to be cooled.

33. The method as in claim 31, wherein controlling the freezing rate comprises controlling the volume of cooling fluid.

34. The method as in claim 31, wherein controlling the freezing rate comprises controlling the temperature of the cooling fluid.

35. The method as in claim 20, further comprising cooling the substance at a controlled cooling rate.

36. The method as in claim 35, wherein controlling the cooling rate comprises controlling the substantially constant predetermined velocity of the cooling fluid circulated past the substance to be cooled.

37. The method as in claim 35, wherein controlling the cooling rate comprises controlling the volume of cooling fluid.

38. The method as in claim 35, wherein controlling the cooling rate comprises controlling the temperature of the cooling fluid such that the temperature differential throughout the cooling fluid is maintained within about 0.5 degrees centigrade.

39. A method for cooling a substance comprising: circulating cooling fluid past the substance using at least one circulator; determining changes in cooling fluid viscosity due to thermal transfer; and altering circulator force to compensate for the changes in cooling fluid viscosity, such that a substantially constant predetermined velocity of fluid past the substance is maintained.

40. The method as in claim 39, further comprising circulating the cooling fluid at the substantially constant predetermined velocity past a heat exchanging coil submersed in the cooling fluid, and wherein the heat exchanging coil is capable of removing at least the same amount of heat from the cooling fluid as the amount of heat the cooling fluid removes from the substance.

41. The method as in claim 40, wherein the heat exchanging coil is a multi-path coil.

42. The method as in claim 40, wherein the size of the heat exchanging coil is directly related to an area through which the cooling fluid is circulated, wherein the area is about 24 inches wide and 48 inches deep.

43. The method as in claim 40, further comprising cooling the heat exchanging coil with a refrigeration unit substantially matching load requirements of the heat exchanging coil.

44. The method as in claim 39, further comprising maintaining the cooling fluid at a temperature of between about -24 degrees centigrade and -26 degrees centigrade.

45. The method as in claim 39, wherein the circulation rate is about 35 liters per minute per foot of cooling fluid through an area not greater than about 24 inches wide and 48 inches deep.

46. The method as in claim 39, wherein the circulator comprises: a motor; and an impeller rotatably coupled to the motor such that the impeller rotates to circulate the cooling fluid; and wherein the circulator force is a torque supplied by the motor.

47. The method as in claim 39, wherein an additional circulator is employed for each foot of cooling fluid to be circulated past an area not greater than about 24 inches wide and 48 inches deep.

48. The method as in claim 39, wherein the cooling fluid is a solute.

49. The method as in claim 39, further comprising freezing the substance at a controlled freezing rate.

50. The method as in claim 49, wherein controlling the freezing rate comprises controlling the substantially constant predetermined circulation rate of the cooling fluid.

51. The method as in claim 49, wherein controlling the freezing rate comprises controlling the volume of cooling fluid.

52. The method as in claim 49, wherein controlling the freezing rate comprises controlling the temperature of the cooling fluid.

53. The method as in claim 39, further comprising cooling the substance at a controlled cooling rate.

54. The method as in claim 53, wherein controlling the cooling rate comprises controlling the substantially constant predetermined circulation rate of the cooling fluid.

55. The method as in claim 53, wherein controlling the cooling rate comprises controlling the velocity of the cooling fluid flowing past the substance to be cooled.

56. The method as in claim 53, wherein controlling the cooling rate comprises controlling the temperature of the cooling fluid such that the temperature differential throughout the cooling fluid is maintained within about 0.5 degrees centigrade.
Description


FIELD OF THE INVENTION

The present invention relates generally to cooling methods and more particularly to methods for rapidly cooling, chilling, or freezing various substances.

BACKGROUND OF THE INVENTION

In many industries, rapid cooling, chilling or freezing of items is desirable. While currently available cooling and freezing techniques perform adequately in many instances, numerous industries could benefit from faster or more efficient cooling or freezing methods. Consider, for example, the frozen food industry. The taste, texture, and general appearance of many vegetables, fruits, etc., can vary significantly depending upon the rate at which the item is cooled. Additionally, faster cooling can shorten the time needed to get a frozen food item to market and decrease the amount of inventory storage. For example, if unfrozen product could be received, frozen, and shipped all in the same day, remarkable cost savings might be achieved.

Commercial establishments such as restaurants, hotels, convenience stores, etc. can benefit from rapid cooling of food and beverages that are normally served chilled. For example, if bottled or canned beverages could be chilled quickly enough, only a small number of bottles or cans would need to be kept cool at any one time; most of a stores inventory could be chilled "on demand." As a result, the use of costly, energy consuming refrigerators could be reduced.

Other industries, such as the medical and pharmaceutical industries, may also benefit from rapid cooling of items. These industries rely on various tissues, organs, serums, medicines, etc., to be cooled or frozen. In general, the more quickly such items can be cooled, the longer the items should remain usable.

SUMMARY OF THE INVENTION

Therefore, what is needed is a method of cooling, chilling or freezing food, beverages, pharmaceuticals, or other substances more effectively and/or efficiently. Accordingly, at least one embodiment of the present invention provides a method for cooling substances comprising circulating cooling fluid past a substance to be cooled, and controlling the circulation of the cooling fluid such that the cooling fluid is circulated at a substantially constant predetermined velocity independent of changes in cooling fluid viscosity. In one embodiment, at least one circulator is used to circulate the cooling fluid. In another embodiment, the method includes determining changes in cooling fluid viscosity due to thermal transfer, and altering circulator force to compensate for the changes in cooling fluid viscosity, such that a substantially constant predetermined flow of fluid past the substance is maintained. In at least one embodiment, a circulator comprises a motor and an impeller. Various embodiments circulate cooling fluid past a heat exchanging coil submersed in the cooling fluid. This heat exchanging coil is preferably a "multi-path coil," which allows refrigerant to travel through multiple paths, in contrast to conventional refrigeration coils in which refrigerant is generally restricted to one or two continuous paths. As a result the heat exchanging coil used to implement the present invention can be made approximately fifty percent of the size of a conventional coil required to handle the same heat load. The heat exchanging coil is cooled by a refrigeration unit, and is employed to keep the cooling fluid at a desired temperature.

An object of at least one embodiment of the present invention is to quickly and efficiently cool, chill or freeze various substances.

An advantage of at least one embodiment of the present invention is that sensitive or delicate substances can be frozen without damage to the substance.

Another advantage of at least one embodiment of the present invention is that cooling, chilling or freezing is accomplished more rapidly than by many conventional methods.

Yet another advantage of various embodiments of the present invention is that various substances can be cooled, chilled or frozen more cost effectively due to decreased energy usage.

A further advantage of the present invention is that at least one embodiment employs a heat exchanging coil approximately 50 percent smaller than that used with conventional cooling methods handling the same heat load.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, advantages, features and characteristics of the present invention, as well as methods, operation and functions of related elements of structure, and the combination of parts and economies of manufacture, will become apparent upon consideration of the following description and claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures, and wherein:

FIG. 1 is a side view of a chilling apparatus suitable for practicing a method according to at least one embodiment of the present invention;

FIG. 2 is an end view of a cross-section of the chilling apparatus illustrated in FIG. 1; and

FIG. 3 is a flow diagram illustrating a method according to at least one embodiment of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Referring first to FIGS. 1 and 2, a chilling apparatus suitable for practicing a method according to at least one embodiment of the present invention is discussed, and designated generally as cooling unit 100. Cooling unit 100 preferably comprises tank 110 containing cooling fluid 140. Submersed in cooling fluid 140 are circulators 134 such as motors 130 having impellers 132, heat exchanging coil 120, and rack 150, which in one embodiment comprises shelves 155 for supporting substances to be cooled, chilled or frozen. External to tank 110, and coupled to heat exchanging coil 120, is refrigeration unit 190.

Tank 110 may be of any dimensions necessary to immerse substances to be cooled, chilled or frozen in a volume of cooling fluid 140, in which the dimensions are scaled multiples of 12 inches by 24 inches by 48 inches. Other size tanks may be employed consistent with the teachings set forth herein. For example, in one embodiment (not illustrated), tank 110 is sized to hold just enough cooling fluid 140, so that beverage containers, such as wine bottles, milk jugs, soft drink cans, and the like, can be placed in tank 110 for rapid cooling or chilling. In other embodiments, tank 110 is large enough to completely immerse large quantities of meats, vegetables, or other items for rapid freezing. It will be appreciated that tank 110 can be made larger or smaller, as needed to efficiently accommodate various sizes and quantities of substances to be cooled, chilled or frozen. Such substances include, but are not limited to, food items, liquids, pharmaceuticals, or animal, human or plant cells, and the like.

Tank 110 holds cooling fluid 140. In one embodiment, the cooling fluid is a food grade solute. The use of a food grade cooling fluid allows cooling, chilling or freezing of foodstuffs without risk of contamination from the fluid. Good examples of food grade quality fluids are those based on propylene glycol, sodium chloride solutions, or the like. In other embodiments, other fluids, and preferably solutes, are used as cooling fluids. When using a food grade cooling fluid to freeze food items, the food item may be immersed directly in the cooling fluid for rapid and effective freezing. Even relatively delicate food items, such as fish, asparagus and the like, retain their color and texture better than if the same items had been conventionally frozen.

In order to quickly and effectively cool, chill or freeze substances, one embodiment of the present invention circulates cooling fluid 140 past the substance to be cooled, at a relatively constant rate of 35 liters per minute for every foot of cooling fluid contained in an area not more than 24 inches wide by 48 inches deep. The necessary circulation is provided by one or more circulators 134, such as motors 130. In at least one embodiment of the present invention, submersed motors 130 drive impellers 132 to circulate cooling fluid 140 past substances to be cooled, chilled or frozen. Other circulators 134, including various pumps (not illustrated), can be employed consistent with the objects of the present invention. At least one embodiment of the present invention increases the area and volume through which cooling fluid is circulated by employing at least one circulator 134 in addition to motors 130. In embodiments using multiple circulators 134, the area and volume of cooling fluid circulation are increased in direct proportion to each additional circulator employed. For example, in a preferred embodiment, one additional circulator is used for each foot of cooling fluid that is to be circulated through an area of not more than about 24 inches wide by 48 inches deep.

Preferably, motors 130 can be controlled to maintain a constant predetermined velocity of cooling fluid flow past substances to be cooled, chilled or frozen, while at the same time maintaining an even distribution of cooling fluid temperature within +/-0.5.degree. C. at all points within tank 110. The substantially constant predetermined velocity of cooling fluid circulating past substances to be cooled, provides a constant, measured removal of heat, which allows for a controlled, high speed rate of cooling, chilling or freezing. In one embodiment, cooling fluid properties, such as viscosity, temperature, etc., are measured and processed, and control signals are sent to motors 130 to increase or decrease the rotational speed or torque of impellers 132 as needed. In other embodiments, motors 130 are constructed to maintain a given rotational velocity over a range of fluid conditions. In such a case, the torque or rotational speed of impellers 132 imparted by motors 130 are not externally controlled. Of note is the fact that no external pumps, shafts, or pulleys are needed to implement a preferred embodiment of the present invention. Motors 130, or other circulators 134, are immersed directly in cooling fluid 140. As a result, cooling fluid 140 not only cools, chills or freezes the substances placed in tank 110, but cooling fluid 140 also provides cooling for motors 130.

Heat exchanging coil 120 is preferably a "multi-path coil," which allows refrigerant to travel through multiple paths (i.e. three or more paths), in contrast to conventional refrigeration coils in which refrigerant is generally restricted to one or two continuous paths. In addition, the coil size is in direct relationship to the cross sectional area containing the measured amount of the cooling fluid 140. For example, in a preferred embodiment, tank 110 is one foot long, two feet deep and four feet wide, and uses a heat exchanging coil 120 that is one foot by two feet. If the length of tank 110 is increased to twenty feet, then the length of heat exchanging coil 120 is also increased to twenty feet. As a result, heat exchanging coil 120 can be made approximately fifty percent of the size of a conventional coil required to handle the same heat load. As discussed below, circulators 134 such as motors 130, circulate chilled cooling fluid 140 over a substance to be cooled, chilled or frozen, and then transport warmer cooling fluid to heat exchanging coil 120, which is submersed in cooling fluid 140. In at least one embodiment, heat exchanging coil 120 is so designed to remove not less than the same amount of heat from cooling fluid 140 as that removed from the substance to be cooled, chilled or frozen, thereby maintaining the temperature of cooling fluid 140 in a predetermined range. Heat exchanging coil 120 is connected to refrigeration unit 190, which removes the heat from heat exchanging coil 120 and the system.

In a preferred embodiment, refrigeration unit 190 is designed to match the load requirement of heat exchanging coil 120, so that the heat is removed from the system in a balanced and efficient manner, resulting in the controlled, rapid cooling, chilling or freezing of a substance. The efficiency of the refrigeration unit 190 is directly related to the method employed for controlling suction pressures by the efficient feeding of the heat exchange coil 120 and the efficient output of compressors used in refrigeration unit 190.

This methodology requires very close tolerances to be maintained between the refrigerant and cooling fluid 140 temperatures, and between the condensing temperature and the ambient temperature. These temperature criteria, together with the design of the heat exchange coil 120, allows heat exchange coil 120 to be fed more efficiently, which in turn allows the compressor to be fed in a balanced and tightly controlled manner to achieve in excess of twenty-five percent greater performance from the compressors than that which is accepted as the compressor manufacturer's standard rating.

Note that in the embodiment illustrated in FIG. 1, refrigeration unit 190 is an external, remotely located refrigeration system. However, in another embodiment (not illustrated), refrigeration unit 190 is incorporated into another section of tank 110. It will be appreciated that various configurations for refrigeration unit 190 may be more or less appropriate for certain configurations of cooling unit 100. For example, if tank 110 is extremely large, a separate refrigeration unit 190 may be desirable, while a portable embodiment may benefit from an integrated refrigeration unit 190. Such an integration is only made possible by the efficiencies achieved by implementing the principles as set forth herein, and particularly the use of a reduced-size heat exchanging coil.

By virtue of refrigeration unit 190 and heat exchanging coil 120, in a preferred embodiment, the cooling fluid is cooled to a temperature of between -24.degree. C. and -26.degree. C., with a temperature differential throughout the cooling fluid of less than about +/-0.5.degree. C. In other embodiments, the cooling fluid is cooled to temperatures outside the -24.degree. C. to -26.degree. C. range in order to control the rate at which a substance is to be cooled, chilled or frozen. Other embodiments control the circulation rate of the cooling fluid to achieve desired cooling, chilling or freezing rates. Alternatively, the volume of cooling fluid may be changed in order to facilitate a particular cooling, chilling or freezing rate. It will be appreciated that various combinations of cooling fluid circulation rate, cooling fluid volume, and cooling fluid temperature can be used to achieve desired cooling, chilling and freezing rates.

By properly balancing the refrigeration plant and coil size, heat can be removed from a substance up to 80% faster than known conventional refrigeration systems. Additionally, heat removal can be held at a constant rate 24 hours per day. At least one embodiment of the present invention has been shown to provide a performance coefficient greater than 1. Recall that the performance coefficient of a cooling system is

##EQU00001## where P.sub.c is the performance coefficient, Q.sub.c is the amount of heat removed, and W is the amount of work needed to remove the heat. For example, a system according to the present invention has been shown to be capable of removing 41,000 Watts of heat from a substance to be cooled using only 31,000 Watts of electricity. Using these values to compute the performance coefficient yields the following equation:

.times..times..times..times. ##EQU00002## which shows that the performance coefficient for at least one embodiment of the present invention is 1.32. In addition, tests have been performed showing that the measured refrigeration load required to freeze a 5 kg piece of Beef Rump from +6.degree. C. to a core temperature of -18.degree. C. is 1479 BTU's. An operational freezer in a normal production process freezes the Beef Rump in 40 hours or more. A method according to at least one embodiment of the present invention has been shown to freeze a 5 kg piece of Beef Rump in approximately 3 hours, a time savings of 37 hours.

In addition to the rapid rate at which substances may be frozen, the controlled rate of cooling, chilling and freezing provided by a preferred embodiment of the present invention can prevent damage to substances being cooled, chilled or frozen (such as the Beef Rump), by preventing the formation of ice crystals and lessening the damage to cell structures.

Referring now to FIG. 2, an embodiment of cooling system 100 suitable for cooling, chilling or freezing relatively large quantities of substances is discussed. Reference numerals in FIG. 2 that are like, similar or identical to reference numerals in FIG. 1 indicate like, similar or identical features. Tank 110 contains cooling fluid 140, into which rack 150 may be lowered. Rack 150 is movably coupled to rack support 210, such that rack 150 may be raised or lowered to facilitate the placement of substances into tank 110.

In use, substances to be cooled, chilled or frozen are placed on shelves 155 of rack 150. Preferably, shelves 155 are constructed of wire, mesh, or otherwise, so that cooling fluid 140 may freely circulate over, under and/or around substances placed thereon. Preferably, once the cooling fluid is chilled to a desired temperature, rack support 210 lowers rack 150 into tank 110, in order to submerge shelves 155 in cooling fluid 140. Lowering rack 150 may be accomplished manually or using various gear, chain, and/or pulley configurations known to those skilled in the art. Circulators 134 circulate cooling fluid 140 across substances placed on shelves 155 to provide quick and controlled cooling, chilling or freezing.

Referring now to FIG. 3, a method according to one embodiment of the present invention is illustrated, and designated generally by reference numeral 300. The illustrated method begins at step 310, where cooling fluid is circulated past a heat exchange coil. The heat exchange coil is operably coupled to a refrigeration system as discussed above, and is used to reduce the temperature of the cooling fluid as the cooling fluid is circulated past the heat exchange coil. In step 320, the temperature of the cooling fluid is measured, and the method proceeds to step 330 where it is determined whether the temperature of the cooling fluid is within an optimal temperature range. This optimal cooling fluid temperature range may be different for different applications, however, a preferred optimal temperature range for many applications is between -24.degree. C. and -26.degree. C.

If the cooling fluid temperature is determined not to be within an optimal, predetermined temperature range, step 335 is performed. In step 335, the heat exchanging coil is cooled by a refrigeration unit, and the method returns to step 310, in which the cooling fluid is circulated past the heat exchange coil in order to lower the temperature of the cooling fluid. Preferably, steps 310, 320, 330 and 335 are performed continually until the cooling fluid reaches the optimal temperature range.

Once the cooling fluid reaches a proper temperature, the method proceeds to step 337, in which a circulator, such as a submersed motor/impeller assembly or pump, is used to circulate the cooling fluid at the velocity previously discussed, past a substance to be cooled, chilled or frozen. As the cooling fluid passes by the substance, heat is removed from the substance, which is at a higher temperature than the temperature of the cooling fluid, and is transferred to the cooling fluid, which transports the heat away from the substance to be cooled, chilled or frozen. As thermal energy is transferred to the cooling fluid, the cooling fluid's viscosity is generally lowered, so that as long as the substance to be cooled is relatively hot compared to the cooling fluid, the viscosity of the cooling fluid having just flowed past the substance is less than the viscosity of the cooling fluid that has just flowed past the heat exchanging coil.

According to at least one embodiment of the present invention, a substantially constant circulation of cooling fluid past the substance to be cooled, chilled or frozen, should be maintained in order to provide a rapid and controlled rate of cooling. However, the flow rate of the cooling fluid is dependent, at least in part, on the viscosity of the cooling fluid. As mentioned in the previous paragraph, the viscosity of the cooling fluid changes. In order to compensate for the changes in cooling fluid viscosity, step 340 is performed to measure the viscosity of the cooling fluid. Step 350 then determines if the viscosity of the cooling fluid has changed, either due to heating of the cooling fluid by the substance or due to chilling of the cooling fluid by the heat exchanging coil. If the cooling fluid's viscosity has increased, step 358 is performed, wherein the force (e.g. torque) supplied by a circulator (e.g. motor and impeller), is increased to compensate for the increased fluid viscosity. Alternatively, if it is determined in step 358 that the cooling fluid viscosity has decreased, step 353 is performed to reduce the force produced by the circulator. If an insignificant change in viscosity is detected, the circulator continues to circulate the cooling fluid with an unchanged amount of force, or torque. The method then returns to step 310, and begins again.

The steps illustrated in FIG. 3 are shown and discussed in a sequential order. However, the illustrated method is of a nature wherein some or all of the steps are continuously performed, and may be performed in a different order. For example, at least one embodiment of the present invention uses a single circulating motor to circulate the cooling fluid. In such an embodiment, cooling fluid is circulated past a heat exchanging coil as in step 310 and past a substance to be cooled in step 337 at the same time. In addition, one embodiment of the present invention measures cooling fluid temperatures and viscosities continually, and at multiple locations within the system.

In yet another embodiment, in step 350 the viscosity of the cooling fluid is not directly measured and compared to a previous measurement in order to determine a change in the cooling fluid viscosity. Rather, the change in cooling fluid viscosity is determined indirectly from the rotational speed of a circulation motor. If the motor is turning at a slower rate, then the viscosity is assumed to be increasing, and additional power can be supplied to the motor to return the motor to the desired rotational speed, thereby compensating for the change in cooling fluid viscosity. In at least one embodiment, a motor is configured to maintain a substantially constant rate of rotation. This substantially constant rate of motor rotation will result in a substantially constant rate of cooling fluid circulation.

At least one embodiment of the present invention cools, chills or freezes substances in a controlled and balanced manner so as to achieve extremely high rates of heat exchange, resulting in a freezing rate up to more than 80% faster than conventional freezing methods. In addition, at least one method according to the present invention freezes at a high speed at a relatively high temperature without causing damage to the substance, and thereby providing a recovery and or preservation rate higher than known conventional freezers. These methods also reduce the amount of electrical energy used by up to over 50% when compared to existing operational freezers.

In the preceding detailed description, reference has been made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, chemical and electrical changes may be made without departing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the invention, the description omits certain information known to those skilled in the art. The preceding detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. For more information go to WWW.GAPATENTS.COM or WWW.GOOGLE.COM.

Monday, August 24, 2009

United States Patent 6,615,592
WWW.USPTO.GOV
Prien, et al.
September 9, 2003

Method and system for preparing tissue samples for histological and pathological examination

Abstract

Viable biological material is cryogenically preserved (cryopreservation) by immersing the material in a tank of cooling fluid, and circulating the cooling fluid past the material at a substantially constant predetermined velocity and temperature to freeze the material. The material may either be directly plunged into the cooling fluid without preparation, or chemically prepared prior to freezing. A method according to the present invention freezes the biologic material quickly enough to avoid the formation of ice crystals within cell structures (vitrification) and allows the samples to maintain anatomical structure and remain biochemically active after thaw. The temperature of the cooling fluid is preferably between -20 degrees centigrade and -30 degrees centigrade, which is warm enough to minimize the formation of stress fractures and other artefacts in cell membranes due to thermal changes. Cells frozen using a method according to the present invention have been shown to have a significantly less cellular and intercellular damage than cells frozen by other cryopreservation methods used for pathological and histological techniques. Because the present invention can freeze biological material such that the material is vitrified, biochemical activity within the cell is not lost after freezing and thus various embodiments of the present method may be employed in a system to prepare biological material for the newer techniques of cryopathology and immunohistochemistry in the areas of research and patient care.
Inventors: Prien; Samuel D. (Shallowater, TX), Blanton; John (Lubbock, TX), Wood; Brian (Lubbock, TX), Cassell; Allan J. (West Heidelberg, AU)
Assignee: Supachill Technologies Pty. Ltd. (West Heidelberg, AU)
Appl. No.: 10/034,999
Filed: December 28, 2001

Current U.S. Class: 62/64 ; 435/374; 62/376; 62/51.1
Current International Class: A01N 1/02 (20060101); F25D 31/00 (20060101); G01N 1/42 (20060101); F25D 25/00 (20060101); F25D 017/02 (); F25B 019/00 (); C12N 005/00 ()
Field of Search: 62/64,373,375,376,62,51.1 435/374,1.3
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Other References

Database-BIOSIS Online!, Biosciences Information Service, Philadelphia, PA, US; R.P. Cohen et al.: "Predicting Cold Tolerance In Perennial Ryegrass Lolium-Perenne Through Alcohol Bath Freezing of Seedling Plants"; XP002187229 abstract & Agronomy Journal, vol. 30, 1986, pp. 560-563..

Primary Examiner: Doerrler; William C.
Attorney, Agent or Firm: Galasso; Raymond M. Simon, Galasso & Frantz PLC
WWW.GAPATENTS.COM

Parent Case Text


CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit under 35 U.S.C. .sctn.119 of the following U.S. provisional patent application Serial No. 60/259,418, entitled "Method And System For Preparing Tissue Samples For Histological And Pathological Examination", which was filed on Jan. 2, 2001.
Claims


What is claimed is:

1. A method comprising: freezing a biochemically active tissue sample, wherein freezing includes: immersing the tissue sample in cooling fluid; circulating the cooling fluid past the tissue sample at a substantially constant predetermined velocity and temperature to freeze the tissue sample such that the tissue sample is vitrified; and wherein at least a portion of the tissue sample maintains its anatomical structure and remains biochemically active after thaw; thawing the tissue sample; and examining the thawed tissue sample.

2. The method as in claim 1, further comprising sectioning the tissue sample.

3. The method as in claim 1, wherein examining the thawed tissue sample includes histological examination.

4. The method as in claim 1, wherein examining the thawed tissue sample includes ultrastructural examination.

5. The method as in claim 1, wherein examining includes the use of immunohistochemistry examination.

6. The method as in claim 5, wherein immunohistochemistry includes fluorescent labeled antibody staining.

7. The method as in claim 1, wherein more than about 55 percent of the tissue sample exhibits no damage to cellular anatomical structure and remains biochemically active after thaw.

8. The method as in claim 1, wherein more than about 45 percent of the tissue sample exhibits no damage to cellular anatomical structure and remains biochemically active after thaw.

9. The method as in claim 1, wherein more than about 85 percent of the tissue sample maintains its anatomical structure and remains undamaged after thaw.

10. The method as in claim 1, wherein the cooling fluid is maintained at a temperature of between about -20 degrees centigrade and about -30 degrees centigrade.

11. The method as in claim 1, wherein the velocity of the cooling fluid past the tissue sample is about 35 liters per minute per foot of cooling fluid through an area not greater than about 24 inches wide and 48 inches deep.

12. The method as in claim 1, wherein, the cooling fluid is circulated by a motor/impeller assembly immersed in the cooling fluid.

13. The method as in claim 1, further comprising circulating the cooling fluid past a multi-path heat exchanging coil submersed in the cooling fluid, and wherein the heat exchanging coil is capable of removing at least the same amount of heat from the cooling fluid, as the cooling fluid removes from the tissue sample.

14. A method for use in preparing a tissue sample for examination, the method comprising: immersing a biologically active tissue sample in cooling fluid; and freezing the tissue sample directly to a temperature higher than about -30 degrees centigrade by circulating the cooling fluid past the tissue sample at a substantially constant predetermined velocity and temperature such that the tissue sample is vitrified, at least a portion of the tissue sample maintains its anatomical structure, and at least a portion of the tissue sample remains biochemically active after thaw.

15. The method as in claim 14, further comprising sectioning the tissue sample.

16. The method as in claim 14, further comprising thawing the tissue sample.

17. The method as in claim 14, wherein examination includes histological examination.

18. The method as in claim 14, wherein examination includes ultrastructural examination.

19. The method as in claim 14, wherein examination includes the use of immunohistochemistry examination.

20. The method as in claim 19, wherein immunohistochemistry includes fluorescent labeled antibody staining.

21. The method as in claim 14, wherein more than about 40 percent of the tissue sample maintains its anatomical structure and remains biochemically active after thaw.

22. The method as in claim 14, wherein more than about 80 percent of the tissue sample maintains its anatomical structure and remains biochemically active after thaw.

23. The method as in claim 14, wherein more than about 85 percent of the tissue sample maintains its anatomical structure and remains undamaged after thaw.

24. The method as in claim 14, wherein the cooling fluid is maintained at a temperature of between about -20 degrees centigrade and about -30 degrees centigrade.

25. The method as in claim 14, wherein the velocity of the cooling fluid past the tissue sample is about 35 liters per minute per foot of cooling fluid through an area not greater than about 24 inches wide and 48 inches deep.

26. The method as in claim 14, wherein, the cooling fluid is circulated by a motor/impeller assembly immersed in the cooling fluid.

27. The method as in claim 14, further comprising circulating the cooling fluid past a multi-path heat exchanging coil submersed in the cooling fluid, and wherein the heat exchanging coil is capable of removing at least the same amount of heat from the cooling fluid, as the cooling fluid removes from the tissue sample.

28. A system for use in preparing a tissue sample for examination, the system comprising: a cooling fluid reservoir configured to receive a biochemically active tissue sample for immersion in cooling fluid; one or more cooling fluid circulators configured to circulate said cooling fluid; a heat exchanging coil for removing heat from said cooling fluid; a refrigeration unit to remove heat from said heat exchanging coil; and wherein said cooling fluid reservoir, said one or more circulators, and said refrigeration unit cooperate to freeze the tissue sample directly to a temperature higher than about -30 degrees centigrade by circulating the cooling fluid past the tissue sample at a substantially constant predetermined velocity and temperature such that the tissue sample is vitrified, at least a portion of the tissue sample maintains its anatomical structure, and at least a portion of the tissue sample remains biochemically active after thaw.

29. The system as in claim 28, wherein examination includes histological examination.

30. The system as in claim 28, wherein examination includes ultrastructural examination.

31. The system as in claim 28, wherein examination includes the use of immunohistochemistry examination.

32. The system as in claim 31, wherein immunohistochemistry includes fluorescent labeled antibody staining.

33. The system as in claim 28, wherein more than about 40 percent of the tissue sample maintains its anatomical structure and remains biochemically active after thaw.

34. The system as in claim 28, wherein more than about 80 percent of the tissue sample maintains its anatomical structure and remains biochemically active after thaw.

35. The system as in claim 28, wherein more than about 85 percent of the tissue sample maintains its anatomical structure and remains undamaged.

36. The system as in claim 28, wherein the cooling fluid is maintained at a temperature of between about -20 degrees centigrade and about -30 degrees centigrade.

37. The system as in claim 28, wherein the velocity of the cooling fluid past the tissue sample is about 35 liters per minute per foot of cooling fluid through an area not greater than about 24 inches wide and 48 inches deep.

38. The system as in claim 28, wherein, the circulator is a motor/impeller assembly immersed in the cooling fluid.

39. The system as in claim 28, wherein the cooling fluid is circulated past a multi-path heat exchanging coil submersed in the cooling fluid, and wherein the heat exchanging coil is capable of removing at least the same amount of heat from the cooling fluid, as the cooling fluid removes from the tissue sample.
Description


FIELD OF THE INVENTION

The present invention relates generally to cryogenic preservation and more particularly to a method of preserving for examination and diagnostic purposes.

BACKGROUND OF THE INVENTION

Biological materials such as tissues are subjected to various treatments in an histology laboratory to prepare specimens on slides for viewing under a microscope. Pathologists carefully examine the slides and report their findings, which aids physicians in the diagnosis of disease or disease processes. Histopathology has traditionally relied upon examination of samples prepared by one of two basic methods. In the first histological method, samples undergo significant processing in the laboratory, such as fixation to preserve tissues, dehydration to remove water from tissues, infiltration with embedding agents such as paraffin, embedment, sectioning or cutting sections of the tissue for placement on a slide, mounting the sections, and staining the sections to enhance details. The second method, cryogenic preparation, significantly reduces the processing of the first method in that it generally involves snap freezing in a cold liquid or environment, sectioning, mounting, and staining.

While the first method yields significantly superior visualization, it requires an extended period of time for processing, generally a minimum of 18 to 24 hours. Thus this method cannot be applied in situations where a rapid diagnosis of a pathologic process is required, such as during a surgical procedure. Additionally, the processing techniques employed may destroy all or part of the biological activity of the tissues.

The second method has the advantage of speed (30 minutes to 1 hour), however tissue specimens prepared using cryogenic preparation are often subject to cellular damage due to ice crystal formation, which can also cause the loss of biological function of molecules of interest within the tissues, and overall loss of tissue integrity manifested as degraded anatomical structure. Many commercial pathology laboratories discourage the use of frozen tissue for immunohistochemistry in all but special circumstances, because ice crystal formation in stored tissue causes many abnormal artifacts within the sample which make diagnostic interpretation quite difficult, or even impossible in some cases.

With the advent of poly- and then monoclonal antibodies, the focus of both traditional microscopic histology and pathology has shifted from simple subjective observation, to direct objective staining procedures. These newer immunohistochemistry (IHC) techniques help in determining diagnosis when histopathology alone proves inconclusive. However, IHC techniques are dependent on biologically intact receptors within the specimen for proper staining to occur. Therefore it is desirable to utilize a method of tissue specimen preparation that does not limit the amount of active biological material present after preparation is complete.

SUMMARY OF THE INVENTION

Therefore, what is needed is an improved way to cryogenically preserve viable single cells, tissues, organs, nucleic acids, or other biologically active molecules, that avoids at least some of the problems inherent in currently available methods. Accordingly, the present invention provides a method of cryopreservation for freezing a biochemically active tissue sample by immersing the sample in cooling fluid and circulating the cooling fluid past the material. The cooling fluid is circulated past the tissue sample at a substantially constant, predetermined velocity and temperature to freeze the tissue sample such that it is vitrified, yet the tissue sample maintains its anatomical structure and remains biochemically active after thaw. In at least one embodiment, the cooling fluid is maintained at a temperature of between about -20 degrees centigrade and -30 degrees centigrade, and the velocity of the cooling fluid past the tissue sample is about 35 liters per minute per foot of cooling fluid through an area not greater than about 24 inches wide and 48 inches deep. Additionally, at least one embodiment of the present invention immerses a biologically active tissue sample in cooling fluid to freeze the sample directly to a temperature higher than about -30 degrees centigrade. A further embodiment of the present invention provides for circulating the cooling fluid past a multi-path heat exchanging coil submersed in the cooling fluid, where the heat exchanging coil is capable of removing at least the same amount of heat from the cooling fluid as the cooling fluid removes from the tissue sample. At least one embodiment provides a system for implementing the above mentioned methods.

An object of at least one embodiment of the present invention is application of a method to freeze biological material wherein the formation of ice crystals and stress fractures is avoided, and cellular biochemical function is maintained after freezing.

An advantage of at least one embodiment of the present invention is that cryopreservation recovery rates are significantly increased, because biological material is vitrified during freezing.

Another advantage of at least one embodiment of the present invention is that cryopreservation recovery rates are improved, because biological material is vitrified at a high enough temperature to avoid the formation of stress fractures within cell membranes.

Another advantage of at least one embodiment of the present invention is that cryopreservation recovery rates are such that a considerably higher percentage of the biological material maintains its anatomical structure and remains biochemically active after thaw as compared to currently available methods.

An additional advantage of at least one embodiment of the present invention is that cryopreservation recovery rates are such that the biological material samples lend themselves to the application of sectioning, processing and subsequent histological, ultrastructural, and immunohistochemistry examination in shorter periods of time than traditional pathology techniques, thus shortening time to results.

A further advantage of at least one embodiment of the present invention is that once frozen, existing cryopreservation storage facilities and mechanisms can be used to store the frozen biological materials.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, advantages, features and characteristics of the present invention, as well as methods, operation and functions of related elements of structure, and the combination of parts and economies of manufacture, will become apparent upon consideration of the following description and claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures, and wherein:

FIG. 1 is a side view of a chilling apparatus for practicing a method according to at least one embodiment of the present invention;

FIG. 2 is a cross sectional view of the chilling apparatus illustrated in FIG. 1 indicating implementation of cooling systems suitable for freezing relatively large quantities of biological material;

FIG. 2A is a cross sectional view of the chilling apparatus shown in FIG. 1, configured for use with a spiral conveyor according to one embodiment of the present invention;

FIG. 3 is a flow diagram illustrating a system implemented according to at least one embodiment of the present invention;

FIG. 4 is a bar chart showing the results of experimental comparisons between various prior art freezing methods and a freezing method according to a preferred embodiment of the present invention;

FIG. 5 illustrates views, as seen through a microscope, of the morphological appearance of noncryoprotected grape tissue following freeze-thaw cycles of the method of liquid nitrogen and the freezing method according to a preferred embodiment of the present invention;

FIG. 6 illustrates views, as seen through a microscope, of the morphological appearance of heart tissue after freezing using standard cryopreparative techniques, and after application of the method according to a preferred embodiment of the present invention; and

FIG. 7 is an electron microscope view illustrating the complex ultrastructural features such as cellular mitochondria that may be seen after application of the method according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific preferred embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, chemical and electrical changes may be made without departing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the invention, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

Referring first to FIGS. 1 and 2, a chilling apparatus suitable for practicing a method according to at least one embodiment of the present invention is discussed, and designated generally as cooling unit 100. Cooling unit 100 preferably comprises tank 110 containing cooling fluid 140. Submersed in cooling fluid 140 are circulators 134 such as motors 130 having impellers 132, heat exchanging coil 120, and rack 150, which in one embodiment comprises trays 155 for supporting biological material to be frozen. Biological material may include, but is not limited to, viable single cells, tissues and organs, nucleic acids, and other biologically active molecules. Biological material is not required to be species-specific. External to tank 110, and coupled to heat exchanging coil 120, is refrigeration unit 190.

Tank 110 may be of any dimensions necessary to immerse biological material to be frozen in a volume of cooling fluid 140, in which dimensions are scaled multiples of 12 inches by 24 inches by 48 inches. Other tank sizes may be employed consistent with the teachings set forth herein. For example, in one embodiment (not illustrated), tank 110 is sized to hold just enough cooling fluid 140, so containers such as vials, test tubes, beakers, graduated cylinders or the like, can be placed in tank 110 for rapid freezing of suspensions including biological materials and cryoprotectants. In other embodiments, tank 110 is large enough to completely immerse entire organs and or organisms for rapid freezing. It will be appreciated that tank 110 can be made larger or smaller as needed to efficiently accommodate various sizes and quantities of biological material to be frozen. The biological material may be treated with a cryoprotectant prior to being immersed in tank 110.

Tank 110 holds cooling fluid 140. In one embodiment, the cooling fluid is a food-grade solute. Good examples of food-grade quality fluids are those based on propylene glycol, sodium chloride solutions, or the like. In another embodiment, the cooling fluid is itself a cryoprotectant such as dimethylsulfoxide (DMSO), ethylene glycol, propylene glycol, polyethylene glycol or the like. Note that in some instances, the cryoprotectant is itself a food-grade quality fluid. In other embodiments, other fluids, and preferably solutes, are used as cooling fluids. While various containers may be used to hold the biological material, some embodiments of the present invention provide for the biological material to be directly immersed in the cooling fluid for rapid and effective freezing. Such direct immersion may simplify the cryopreservation of some tissues and organs.

In order to freeze biological material while avoiding the formation of ice crystals, one embodiment of the present invention circulates cooling fluid 140 past the biological material to be frozen, at a relatively constant rate of 35 liters per minute for every foot of cooling fluid contained in an area not more than about 24 inches wide by 48 inches deep. The necessary circulation is provided by one or more circulators 134, such as motors 130. In at least one embodiment of the present invention, submersed motors 130 drive impellers 132 to circulate cooling fluid 140 past biological material be to frozen. Other circulators 134, including various pumps (not illustrated), can be employed consistent with the objects of the present invention. At least one embodiment of the present invention increases the area and volume through which cooling fluid is circulated by employing at least one circulator 134, in addition to motors 130. In embodiments using multiple circulators 134, the area and volume of cooling fluid circulation are increased in direct proportion to each additional circulator employed. For example, in a preferred embodiment, one additional circulator is used for each foot of cooling fluid that is to be circulated through an area of not more than about 24 inches wide by 48 inches deep.

Preferably, motors 130 can be controlled to maintain a constant, predetermined velocity of cooling fluid flow past the biological material to be preserved, while at the same time maintaining an even distribution of cooling fluid temperature within +/-0.5 degrees centigrade at all points within tank 110. The substantially constant predetermined velocity of cooling fluid circulating past the biological material provides a constant, measured removal of heat, which allows for the vitrification of the biological material during freezing. In one embodiment, cooling fluid properties such as viscosity, temperature, et cetera, are measured and processed, and control signals are sent to motors 130 to increase or decrease the rotational speed or torque of impellers 132 as needed. In other embodiments, motors 130 are constructed to maintain a given rotational velocity over a range of fluid conditions. In such a case, the torque or rotational speed of impellers 132 imparted by motors 130 are not externally controlled. Of note is the fact that no external pumps, shafts, or pulleys are needed to implement a preferred embodiment of the present invention. Motors 130, or other circulators 134, are immersed directly in cooling fluid 140. As a result, cooling fluid 140 not only freezes biological material placed in tank 110, but cooling fluid 140 also provides cooling for motors 130.

Heat exchanging coil 120 is preferably a "multi-path coil," which allows refrigerant to travel through multiple paths (i.e., three or more paths), in contrast to conventional refrigeration coils in which refrigerant is generally restricted to one or two continuous paths. In addition, the coil size is in direct relationship to the cross sectional area containing the measured amount of the cooling fluid 140. For example, in a preferred embodiment, tank 110 is one foot long, two feet deep, and four feet wide, and uses a heat exchanging coil 120 that is one foot by two feet. If the length of tank 110 is increased to twenty feet, then the length of heat exchanging coil 120 is also increased to twenty feet. As a result, heat exchanging coil 120 can be made approximately fifty percent of the size of a conventional coil required to handle the same heat load. Circulators 134 such as motors 130, circulate chilled cooling fluid 140 over biological material to be frozen, and then transport warmer cooling fluid to heat exchanging coil 120, which is submersed in cooling fluid 140. In at least one embodiment, heat exchanging coil 120 is connected to refrigeration unit 190, which removes the heat from heat exchanging coil 120 and the system.

In a preferred embodiment, refrigeration unit 190 is designed to match the load requirement of heat exchanging coil 120, so that heat is removed from the system in a balanced and efficient manner, resulting in the controlled, rapid freezing of a material. The efficiency of the refrigeration unit 190 is directly related to the method employed for controlling suction pressures by the efficient feeding or the heat exchange coil 120 and the efficient output of compressors used in refrigeration unit 190. This methodology requires very close tolerances to be maintained between the refrigerant and cooling fluid 140 temperatures, and between the condensing temperature and the ambient temperature. These temperature criteria, together with the design of the heat exchange coil 120, allow heat exchange coil 120 to be fed more efficiently, which in turn allows the compressor to be fed in a balanced and tightly controlled manner to achieve in excess of twenty five percent greater performance from the compressors than that which is accepted as the compressor manufacturer's standard rating.

Note that in the embodiment illustrated in FIG. 1, refrigeration unit 190 is an external, remotely located refrigeration system. However, in another embodiment (not illustrated), refrigeration unit 190 is incorporated into another section of tank 110. It will be appreciated that various configurations for refrigeration unit 190 may be more or less appropriate for certain configurations of cooling unit 100. For example, if tank 110 is extremely large, a separate refrigeration unit 190 may be desirable, while a portable embodiment may benefit from an integrated refrigeration unit 190. Such an integration is only made possible by the efficiencies achieved by implementing the principles as set forth herein, and particularly the use of a reduced-size heat exchanging coil.

By virtue of refrigeration unit 190 and heat exchanging coil 120, in a preferred embodiment, the cooling fluid is cooled to a temperature of between -20 degrees centigrade and -30 degrees centigrade, with a temperature differential throughout the cooling fluid of less than about +/-0.5 degrees centigrade. In other embodiments, the cooling fluid is cooled to temperatures outside the -20 degrees centigrade to -30 degrees centigrade range in order to control the rate at which a substance is to be frozen. Other embodiments control the circulation rate of the cooling fluid to achieve desired freezing rates. Alternatively, the volume of cooling fluid may be changed in order to facilitate a particular freezing rate. It will be appreciated that various combinations of cooling fluid circulation rate, cooling fluid volume, and cooling fluid temperature can be used to achieve desired freezing rates.

Referring now to FIG. 2, a cross sectional view of the chilling apparatus illustrated in FIG. 1 indicating implementation of cooling systems suitable for freezing relatively large quantities of biological material; an embodiment of cooling system 100 suitable for freezing relatively large quantities of biological material is discussed. Reference numerals in FIG. 2 that are like, similar, or identical to reference numerals in FIG. 1 indicate like, similar, or identical features. Tank 110 contains cooling fluid 140, into which rack 150 may be lowered. Rack 150 is movably coupled to rack support 210, such that rack 150 may be raised or lowered to facilitate the placement of substances into tank 110.

In use, biological material to be frozen is placed in trays 155 of rack 150. Preferably, trays 155 are constructed of wire, mesh, or otherwise, so that cooling fluid 140 may freely circulate over, under, and/or around items placed thereon. Preferably, once the cooling fluid is chilled to a desired temperature, rack support 210 lowers rack 150 into tank 110, in order to submerge trays 155 in cooling fluid 140. Lowering rack 150 may be accomplished manually or using various gear, chain, and/or pulley configurations known to those skilled in the art. Circulators 134 circulate cooling fluid 140 across substances placed in trays 155 to provide quick and controlled freezing. It will be appreciated that other arrangements for immersing biological material into tank 110 may be employed, and that use of an automatic lowering system is not necessarily preferred for use in all circumstances.

Referring now to FIG. 2A, an embodiment of the present invention employing a multi-tiered spiral path conveyor system is discussed. As illustrated, spiral conveyor 200 may be configured to fit inside tank 110 in order to submerge biological material into cooling fluid 140. In use, once the cooling fluid is chilled to a desired temperature, materials to be frozen are fed into an input feed 160 where they are taken onto conveyor belt 170. The material travels from input feed 160, into the cooling fluid 140 on downward spiral 175, out of cooling fluid 140 on upward spiral 176, and out of spiral conveyor at output feed 180. As noted earlier, the cooling fluid 140 is preferably kept at a constant predetermined temperature, and circulated at a rate that ensures rapid, safe freezing of material to be frozen. The time the material spends submerged in cooling fluid 140 can be varied by adjusting the drive unit, 230, or by other suitable means. Ideally, the speed of conveyor belt 170, in combination with the temperature and circulation rate of cooling fluid 140, will be adjusted so that exactly the desired amount of heat will be removed from materials as they travel through tank 110 on the multi-tiered spiral path conveyor system 200.

Referring now to FIG. 3, a method according to one embodiment of the present invention is illustrated, and designated generally by reference numeral 300. The illustrated method begins at step 310, where cooling fluid is circulated past a heat exchange coil. The heat exchange coil is operably coupled to a refrigeration system as discussed above, and is used to reduce the temperature of the cooling fluid as the cooling fluid is circulated past the heat exchange coil. In step 320, the temperature of the cooling fluid is measured, and the method proceeds to step 330, where it is determined whether the temperature of the cooling fluid is within an optimal temperature range. This optimal cooling fluid temperature range may be different for different applications, however a preferred optimal temperature range for many applications is between -20 degrees centigrade and -30 degrees centigrade.

Should the cooling fluid temperature be determined not to be within an optimal, predetermined temperature range, step 335 is performed. In step 335, the heat exchanging coil is cooled by a refrigeration unit, and the method returns to step 310, in which the cooling fluid is circulated past the heat exchange coil in order to lower the temperature of the cooling fluid. Preferably, steps 310, 320, 330, and 335 are performed continually until the cooling fluid reaches the optimal temperature range.

The temperature of the cooling fluid used to freeze the biological material is an important element of at least one embodiment of the present invention. In order to achieve vitrification using conventional processes, biological material is generally quenched in liquid nitrogen, at a temperature of -196 degrees centigrade. Such a drastic change in temperature over a very short period of time freezes water within cell structures so quickly that ice crystals do not have a chance to form. However, freezing biological material by quenching in liquid nitrogen can cause stress fractures in cellular membranes, thereby limiting the usefulness of quenching in liquid nitrogen for cryopreservation. Since the temperatures used in a preferred embodiment of the present invention are between -20 degrees centigrade and -30 degrees centigrade, stress fractures due to temperature changes are minimized, and vitrification can be achieved with far less damage to cellular membranes.

While the cooling fluid is being cooled to the proper temperature, biological material to be frozen may be chemically prepared for freezing in step 305. It will be appreciated that materials to be used for pathology do not normally require chemical preparation, and foregoing step 305 by plunging materials to be frozen directly into a cooling fluid is consistent with the teachings set forth herein. As noted earlier, biological material includes, but is not limited to, viable single cells, tissues and organs, nucleic acids, and other biologically active molecules. The biological material does not have to be species specific. Chemically preparing the biological material may include pretreatment of the biological material with agents (stabilizers) that increase cellular viability by removing harmful substances secreted by the cells during growth or cell death. Useful stabilizers include those chemicals and chemical compounds, many of which are known to those skilled in the art, which sequester highly reactive and damaging molecules such as oxygen radicals.

Chemically preparing biological material may also include an acclimation step (not illustrated). During or at some time after pretreatment, the biological material to be preserved may be acclimated to a temperature which is reduced from culturing temperatures, but still above freezing. This may help prepare the biological material for the cryopreservation process by retarding cellular metabolism and reducing the shock of rapid temperature transition. Note well, however, than an acclimation step is not required in order to practice the present invention.

In a preferred embodiment, chemically preparing biological material for freezing includes loading the biological material with a cryoprotectant. Loading generally involves the equilibration of biological material in a solution of one or more cryoprotectants. Substances utilized during loading may be referred to as loading agents. Useful loading agents may include one or more dehydrating agents, permeating and non-permeating agents, and osmotic agents. Both permeating agents such as DMSO and ethylene glycol, and a combination of permeating and non-permeating osmotic agents such as fructose, sucrose or glucose, and sorbitol, mannitol, or glycerol can be used. It will be appreciated that other suitable cryoprotectants may be employed consistent with the objects of the present invention.

After the cooling fluid reaches a proper temperature, step 315 is performed, in which the chemically prepared biological material is immersed in cooling fluid. As noted earlier, the biological material may be held in a container, or placed directly into the cooling fluid. The method then proceeds to step 337, in which a circulator, such as a submersed motor/impeller assembly or pump, is used to circulate the cooling fluid at the velocity previously discussed, past the immersed biological material. As the cooling fluid passes by the biological material, heat is removed from the material, which is at a higher temperature than the temperature of the cooling fluid, and is transferred to be cooling fluid, which transports the heat away from the biological material to be frozen. According to at least one embodiment of the present invention, a substantially constant circulation of cooling fluid past the biological material to be frozen should be maintained in order to freeze the prepared biological material such that the prepared material is vitrified.

After the cooling fluid is circulated past the biological material to be frozen, step 339 is performed. Step 339 adjusts the velocity of the cooling fluid as necessary to account for changes in the cooling fluid viscosity, temperature, and the like. Preferably, the velocity of the cooling fluid is held constant by adjusting the force provided by one or more circulators. Once the biological material has reached the desired frozen state, it is removed as shown in step 340. After the material is removed from the cooling fluid in step 340 by means previously discussed, it may be sectioned and thawed for histological, ultrastructural, and immunohistochemistry examinations, such as fluorescent labeled antibody staining.

The steps illustrated in FIG. 3 are shown and discussed in a sequential order. However, the illustrated method is of a nature wherein some or all of the steps are continuously performed, and may be performed in a different order. For example, at least one embodiment of the present invention uses a single circulating motor to circulate the cooling fluid. In such an embodiment, cooling fluid is circulated past a heat exchanging coil as in step 310, and past the biological material to be preserved in step 337 at the same time. In addition, one embodiment of the present invention measures cooling fluid temperatures, viscosities, and other fluid properties continually, and at multiple locations within the system.

In yet another embodiment, some properties of the cooling fluid are not directly measured. Rather, the change in cooling fluid properties is determined indirectly from the rotational speed of a circulation motor. If the motor is turning at a slower rate, then additional power can be supplied to the motor to return the motor to the desired rotational speed, thereby compensating for the change in cooling fluid properties. In at least one embodiment, a motor is configured to maintain a substantially constant rate of rotation. This substantially constant rate of rotation will result in a substantially constant rate of cooling fluid circulation.

A test of one embodiment of the present invention was performed in which five milliliters (5 ml) of water was frozen in a graduated container. Upon freezing, there was less than one percent increase in total volume, much less than expected with conventional freezing. In another test, ice was frozen in sheets in a conventional freezer, and in a cooling system according to a preferred method of the present invention. After freezing, the ice was examined under dark microscope. As expected, the conventional ice displayed a crystalline pattern, whereas the ice frozen according to the principles of the present invention exhibited no light displacement, indicating little to no ice crystal formation.

Refer now to FIG. 4, in which experimental results comparing various cryopreservation methods are compared. Bar graph 400 compares the number of individual cells damaged by use of four different cryopreservation methods B, C, D, and E against a control group A. No cryopreservation was performed on control group A, method B used a conventional freezer to freeze cells to a temperature of -20 degrees centigrade, method C used an ultralow freezer to freeze cells to a temperature of -80 degrees centigrade, method D used liquid nitrogen to freeze cells to a temperature of -196 degrees centigrade, and method E used a preferred embodiment of the present invention to freeze cells to a temperature of -25 degrees centigrade.

The results of the experiments, shown in bar graph 400, used plant tissue (seedless grapes) which were frozen by the conventional methods previously discussed, as well as by the method as embodied by the present invention, without any form of preparation or cryoprotectant. The frozen plant tissue was then thawed and thin sections were cut and examined, unstained, using phase-contrast microscopy. Plant tissue was employed in the experiments because gross distortion of the tissue by ice crystal formation or water expansion caused by freezing would disrupt the tissue's cell wall structure and could be readily observed. The results, as illustrated in FIG. 4, clearly show the superiority of the method performed according to a preferred embodiment of the present invention. As expected, the control, A, exhibited no cellular damage. Method B, the -20 C. freezer, exhibited damage in approximately 45% of the cellular wall structures; method C, the -80 C. freezer, exhibited damage in approximately 55% of the cellular wall structures; method D, liquid nitrogen, exhibited damage in approximately 59% of the cellular wall structures. However, the method performed according to a preferred embodiment of the present invention exhibited only about 12.5% cellular damage.

The superiority of the method performed according to a preferred embodiment is also seen in FIG. 5, which illustrates views, as seen through a phase-contrast microscope, of the morphological appearance of noncryoprotected grape tissue following freeze-thaw cycles of the method of liquid nitrogen and the freezing method according to a preferred embodiment of the present invention. Note in FIG. 5 the altered form and structure of the tissue indicating cellular wall damage is seen to be considerably less in the freeze-thaw method performed according to a preferred embodiment than that seen in the view of tissue freeze-thaw cycled with a method using liquid nitrogen.

Referring now to FIG. 6, views, as seen through a microscope, of the morphological appearance of heart tissue after freezing using standard cryopreparative techniques, and after application of the method according to a preferred embodiment of the present invention is discussed. FIG. 6 illustrates the results of a different experiment which was performed on tissue samples collected post-mortem from mice and canine cadavers. Tissue samples were collected from five organ systems: ovarian, heart, liver, kidney, and lung. Tissues were prepared for conventional histology, cryo-sectioning, or ultrastructural examination using standard freezing techniques, and also following freezing by the method performed according to a preferred embodiment of the present invention. The resulting sections were then evaluated by a trained clinical pathologist. As expected, samples that were never frozen exhibited superior morphology upon histological evaluation. However, the pathologist report states that tissue frozen according to the method of a preferred embodiment of the present invention was at least as well preserved as tissue using standard cryogenic technology, and further that several types of tissue, most notably kidney and muscle (heart) demonstrated marked improvement in tissue integrity when frozen according to the method embodied by the present invention. FIG. 6 clearly indicates that the standard cryopreparative technique has numerous artifacts, such as "accordion folds" 605 seen within the heart muscle sample, as compared to the heart muscle sample which underwent the method as embodied by the present invention.

Refer now to FIG. 7, in which an electron microscope view illustrates the complex ultrastructural features, such as cellular mitochondria 705, seen after application of the method according to a preferred embodiment of the present invention as compared to a control which was never frozen. The electron microscope views illustrated in FIG. 7 clearly show little if any difference between the tissues frozen by the method according to a preferred embodiment of the present invention and control tissue which had never been frozen. Additionally, tissues frozen by the standard techniques of liquid nitrogen or mechanical freezing (not illustrated) exhibited significantly more damage upon examination than those of tissues frozen by the method according to a preferred embodiment of the present invention.

As stated earlier, a major problem with frozen sections created using the current technology is the loss of specific chemical reactions upon freezing. Loss of this activity renders these samples essentially useless for the more modern techniques of immunohistochemistry based upon antibody stain. An experiment which was conducted using a fluorescent labeled antibody (5.1H11, a human NCAM that is muscle specific) demonstrated that primary porcine satellite cells which were previously stained for fluorescence with this antibody continued to fluoresce after freezing when prepared according to the method of a preferred embodiment of the present invention. However, cells frozen in liquid nitrogen failed to fluoresce after thaw. The results of this experiment indicate that the method of a preferred embodiment will allow the newer techniques of cryopathology and immunohistochemistry to be applied in the areas of research and patient care.

Because the present invention can freeze biological material such that the material is vitrified, the formation of stress fractures in cellular membranes is minimized, and chemical activity within the cell is not lost after freezing, various embodiments of the present invention may find application in other medical fields with proper chemical preparation, such as skin grafts, cornea storage, circulatory vessel storage, freezing of transplant tissues, and infertility treatment, as well as in the investigation of molecular regeneration disease (cancer).

Although an embodiment of the present invention has been shown and described in detail herein, along with certain variants thereof, many other varied embodiments that incorporate the teachings of the invention may be easily constructed by those skilled in the art. Accordingly, the present invention is not intended to be limited to the specific form set forth herein, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents, as can be reasonably included within the spirit and scope of the invention. For more information go to WWW.GAPATENTS.COM or WWW.GOOGLE.COM.