US3418824A - Manually operated closed-cycle refrigeration system - Google Patents

Description

Dec. 3l, 1968 H, K, BEUTEL ET Al. 3,418,824

MANUALLY-OPERATED CLOSED-CYCLE REFRIGERATION SYSTEM Sheet Filed June 16, 1967 Dec. 31, 1968 H, K, BEUTEL ET AL 3,418,824

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United States Patent O 3,418,824 MANUALLY OPERATED CLOSED-CYCLE REFRIGERATION SYSTEM Helmuth K. Beutel, Azusa, Arvel D. Markum, Covina,

and Charles W. ODonnell, Cucamonga, Calif., assignors to General Dynamics Corporation, a corporation of Delaware Filed June 16, 1967, Ser. No. 646,573 6 Claims. (C1. s2- 474) ABSTRACT OF THE DISCLOSURE This disclosure is directed to a manually-operated closed-cycle refrigeration system. More particularly, the system includes three major sections: (l) a miniature Joule-Thomson heat exchanger (or cryostat), (2) a handoperated compressor/low pressure reservoir section, and (3) a high pressure reservoir/control valve section. The hand-operated compressor comprises first and second compression stages each including a cylinder and piston, said second stage being operatively coupled in series with said rst stage whereby gas is introduced into said rst stage through an intake check valve from 'a low pressure reservoir connected with the system return line during the suction stroke of the first stage piston. During the compression stroke of the iirst stage piston the gas is forced through an interstage check valve into the second stage cylinder cavity `and is then compressed to a higher pressure upon the compression stroke of the second stage piston. The two pistons are arranged so that when the lirst stage piston is in its compression stroke the second stage piston is in its suction stroke. The respective pistons are operatively coupled to a hand-operated reciprocating lever by way of ya rack and pinion arrangement. Both of the compression stages lare operatively associated with the low pressure reservoir such that leakage past the piston seals is collected by the reservoir thus preventing external leakage of the system.

Background f the invention This invention relates to closed-cycle refrigeration systems, and more particularly to such a system which utilizes a hand-operated compressor. While closed-cycle cooling systems including a cryostat and a multistage cornpressor are known in the prior art as exemplified by U.S. Patent 3,204,422, such a system, as the present invention which utilizes a compressor which can be operated manually in an environment where electrical or mechanical power is not available is not previously known. Also, two-stage hand-operated pumps as exemplified by U.S. Patent 57,897 are known in the art. However, a twostage hand-operated compressor utilizing the piston low pressure reservoir arrangement of the present invention is not previously known. Thus, this invention advances the stage of the art by providing a manually-Operated closedcycle refrigeration system which incorporates a novel twostage hand-operated compressor.

Summary `of the invention Therefore, it is an object `of this invention to provide a manually-operated closed-cycle refrigeration system.

A further object of the invention is to provide a manually-operated closed-cycle refrigeration system which utilizes a two-stage hand-operated compressor.

Another object of the invention is to provide a handoperated two-stage pump assembly.

Another object of the invention is to provide a dualstage hand-operated compressor wherein the piston units thereof are positioned with respect to a low pressure reser- Voir such as to collect any fluid leaking past the pistons.

Other objects of the invention, not specifically set forth above, will become readily apparent from the following Written description and the accompanying drawings wherein:

Brief description: of the drawings FIG. l is a schematic view of an embodiment of the inventive closed-cycle manually-operated refrigeration system;

FIG. 2 is a schematic partial cross-sectional view of the novel hand-operated multistage compressor;

FIG. 3 is a side view partially in cross-section and with portions thereof cut away illustrating an embodiment of the inventive `compressor of the type illustrated in FIG. 2;

FIG. 4 is a view taken along the lines 4-4 of FIG. 3; and

FIG. 5 is an end view of the FIG. 3 compressor with the cylinder head removed.

Description of the embodiment The system is composed of three major sections; the miniature Joule-Thomson heat exchanger (or cryostat), the hand-operated compressor/ low pressure reservoir section, and the high-pressure reservoir/control valve section. Referring now to FIG. l, the illustrated embodiment of the inventive system comprises a Joule-Thomson heat exchanger or cryostat 10, which is provided with the conventional cooling coiled tubing 11 connected with a high pressure gas reservoir and molecular sieve generally indicated at 12 via a particulate filter 13, a fill valve assembly 14, a pressure gage assembly 15, a control valve assembly 16 which may be of the coaxial solenoid or handoperated type, and a second particulate filter 17. Cryostat 10 is also provided with discharge tubing indicated at 18 and connected to a low pressure reservoir 19 via a one-way valve assembly 20. Low pressure reservoir 19 is defined by the housing of two-stage compressor generally indicated `at 21. The input of the iirst compressor stage indicated at 22 of compressor 21 is connected with the cryostat discharge line 13 and low pressure reservoir 19 via a one-way valve assembly 23. The output of the first stage 22 is connected to the input of the second cornpressor stage indicated at 24 via a one-way valve assembly 25 and the output from the second stage 24 is connected with high pressure reservoir 12 via a one-way valve assembly 26. A pressure gage 27 is operatively connected to the housing of compressor 21 for indicating the pressure within low pressure reservoir 19. The compressor 21 and the associated valve assemblies 23, 25 and 26 will be described in greater detail hereinafter.

The FIG. 1 system operation occurs in the following sequence, assuming that the high pressure reservoir 12 had been previously pressurized by compressor 21:

(1) Upon activation of the control solenoid valve 16, high pressure refrigerant gas flows as indicated by the flow arrow from the high pressure gas reservoir 12 to the miniature Joule-Thomson heat exchanger 10.

(2) Upon existing the expansion nozzle portion of tubing coil 11, the refrigerant gas c-ools (due to sudden release of pressure) to its desired temperature.

(3) The refrigerant gas then removes heat from the encasing sleeve or housing of cryostat 10, and the incoming refrigerant gas is further cooled by the exhausting gas dischargnig between the cryostat coils 11 and the walls of the encasing sleeve of the cryostat, as known in the art.

(4) The exhausted gas is then accumulated in the low pressure reservoir 19 as indicated by the flow arrow.

(5) The exhausted low pressure refrigerant is then pumped from the low pressure reservoir 19 to the high pressure reservoir 12 by operating the two-stage compressor 21 as described hereinafter. Note that any leakage of the fluid about the pistons of compressor 21 will .be received by the low pressure reservoir 19 thus preventing loss of the fluid.

(6) The molecular sieve portion of reservoir 12 removes contaminants frorn the refrigerant gas which may have been introduced during the cycle.

Tests conducted on the FIG. l system have demonstrated low leakage rates and the ability to recompress the refrigerant from a low reservoir pressure of l0 p.s.i.g. to a high output pressure of 1800 p.s.i.g. The closed cycle system makes it economically possible to use high priced exotic refrigerants to cool small components or miniature systems to cyrogenic temperatures. The system has applications in many areas requiring cyrogenic temperature environments, such as infrared detectors, superconductivity applications, materials compatibility investigations, etc.

FIGS. 2-5 illustrate in greater detail the manually-operated two-stage compressor 21 of the FIG. 1 system. Referring first to FIG. 2, the flow diagram and mechanical operational sequence is illustrated. Compressor 21 comprises a housing 28, a portion of which defines low pressure reservoir 19 which is connected with cryostat discharge conduit 18 and the first compressor stage 22 via passageways 29 and 30, respectively. First compressor stage 22 comprises a chamber or cylinder 31, defined by housing 28, within which a first stage compression piston 32 reciprocates, piston 32 being connected via a piston rod or rack 33 to a hand-operated piston drive mechanism indicated at 34 and actuated by a crank handle 35. Unidirectional ow check valve 23 of the -ball and spring type functions as the inlet or intake valve for the first stage 22 while the similarly constructed unidirectional flow check valve 25 positioned in a passageway 36 in housing 28 interconnecting the compressor stages functions as the output or exhaust valve therefor. The second compressor stage 24 comprises a chamber or cylinder 37, defined by housing 28, within which a second stage compression piston 38 reciprocates, piston 38 being connected via a piston rod or rack 39 to piston drive mechanism 34. The pistons 32 and 38 are connected to drive mechanism 34 in such a manner that when piston 32 is on its intake stroke (movement to the right as shown) piston 38 is on its compression stroke, and vice versa, as illustrated in FIG. 2 and indicated by the double arrows on the piston rods 33 and 39. Movement of crank handle 35 from the solid line position to the right so as to be in the phantom position causes pistons 32 and 38 to reverse the position shown, thus placing the first stage 22 on compression and the second stage 24 on intake. Unidirectional flow check valve 25 in passageway 36 functions as the input or intake valve for the second stage 24 while the similarly constructed unidirectional iiow check valve 26 positioned in a passageway 40 of housing 28, interconnecting the second stage with a conduit 41 connected to high pressure reservoir 12 for example, functions as the output or exhaust valve therefor.

It is seen from FiG. 2 that low pressure fluid in tubing or conduit 18 flows into low pressure reservoir 19 via passageway 29 and upon movement of the first stage piston 32 on the suction stroke, to the right, the fluid is drawn into chamber or cylinder 31 from conduit 18 and/ or low pressure reservoir via passageway 30 and val-ve assembly 23 as shown by the iiow arrows. Simultaneously, upon movement of piston 32 to the right, second stage piston 38 moves to the left as shown on the compression stroke and forces fiuid under high pressure via valve assembly 26 and passageway 40 to a point of use. Due to the uid pressure in cylinder 37 being greater than the uid pressure in cylinder 31, the valve assembly 25 is positioned as shown thus preventing communication between the cylinders during compression of the second stage 24. Movement of the crank handle to the position shown in phantom places the first stage 22 on compression and the second stage 24 on intake or suction thus forcing uid from cylinder 31 through passageway 36 and valve assembly 25 into cylinder 37 as indicated by the flow arrow in passageway 36. It is thus seen that continuous oscillation of the crank handle causes continuous two stage compressor operation.

Pumping efciency is maintained by minimizing the volumes of the unidirectional flow check valves and by reducing the dead-end volume to a minimum. Additional efficiency is obtained by properly balancing the compression ratios between stages. The ratios are determined by the expected operating parameters of the compressor.

Referring now to the specific embodiment of the inventive two-stage compressor as illustrated in FIGS. 3-5, like reference numerals are utilized for the components above described with respect to FIGS. l and 2. Compressor housing 28, as shown in FIG. 3, comprises a section 42 defining the cylinders, a section 43 defining the low pressure reservoir, and a cylinder head 44 containing certain of the passageways and the check valves, secured to housing portion 42 via bolts 45, sections 42 and 43 having a reservoir seal 46 disposed therebetween, while a pair of cylinder seals 46' are disposed between section 42 and cylinder head 44. The hand-operated piston drive mechanism 34 illustrated in detail in FIGS. 3 and 4 comprises a pinion drive gear 47 drivingly connected to crank 35 via a drive shaft 48 mounted on bearings 49 in housing section 43. A pair of shaft seals 50 are positioned around drive shaft 48, while a pair of spacers 51 are positioned within housing section 43 intermediate the pinion drive gear 47 and the internal surface of the housing section. A pair` of driven rack gears 52 and 53 are operatively mounted with respect to drive gear 47 and may be integral with piston rods 33 and 39, respectively, or connected by means such as pins 54 with said piston rods for driving same.

Loss of gas due to leakage is minimized by making all internal seals either static or low-pressure reciprocating seals. Leakage past the piston seals, while decreasing pumping efficiency, is not a serious factor since it is collected in the low pressure reservoir. The only dynamic seals from internal to external are the reciprocating seals that seal the drive shaft in the low-pressure reservoir. By the use of fine finishes on the rack gears, gear ways, shaft and compression cylinders, lubrication requirements are minimal, for example, lubrication could consist of using high vacuum grease on the piston seals, rackways and shaft seals.

lIt has thus been shown that the present invention provides a closed-cycle refrigeration system which includes a two-stage manually-operated compressor which incorporates a low pressure reservoir around the compression pistons to collect leakage past the piston seals. Also, if desired, the compressor can be operated by any type power plant capable of providing the necessary reciprocating motion for the pistons.

lthough a particular embodiment of the invention has been illustrated and described, modifications will become apparent to those skilled in the art, and it is intended to cover in the appended claims all such modifications as come within the true spirit and scope of the invention.

What we claim is:

1. A two stage compressor comprising: a housing, a first piston cylinder positioned within said housing at one end thereof, a second piston cylinder positioned within said housing at the same end thereof as said first cylinder and parallelly disposed substantially adjacent to said first cylinder, said first and second piston cylinders each having an open end and a substantially closed end, a reservoir within said housing at the opposite end of said housing from said first and second cylinders said reservoir in communication with the open ends of said first and second piston cylinders, a first piston head operable within said first piston cylinder, a first piston rod connected to said first piston head and extending into said reservoir, a second piston rod connected to said second piston head and extending into said reservoir, said first piston rod including a rack gear portion and said second piston rod including a rack gear portion parallelly disposed to said rack gear portion of said first piston rod, a drive shaft rotatably mounted in said housing and extending outward therefrom, a drive gear mounted upon said drive shaft for rotation therewith, said drive gear operably associated with said rack gear portions of said first and said second piston rods, a crank assembly secured to the external portion of said drive shaft to rotate said drive shaft and thereby reciprocate the piston rods, a first fluid passageway within said housing extending from the substantially closed end of said first cylinder to the exterior of said housing, a second uid passageway within said housing interconnecting the substantially closed end of said first cylinder with the substantially closed end of said second cylinder, a third uid passageway within said housing extending from the substantially closed end 0f said second cylinder to the exterior of said housing, a fourth uid passageway within said housing interconnecting said reservoir with said first fluid passageway, a first unidirectional valve means operably positioned Within said first passageway to pass fiuid into the first cylinder, a second unidirectional valve means operably positioned within said second passageway to pass fluid from said first cylinder to said second cylinder, and a third unidirectional valve means operably positioned within said third passageway to pass fiuid under pressure from said second cylinder to the exterior of said housing.

2. The two-stage compressor defined in claim 1, additionally including bearing means for said drive shaft operatively mounted in said housing.

3. The two-stage compressor defined in clairn 2, additionally including seal means operatively positioned about said drive shaft.

4. The two-stage compressor defined in claim 1, additionally including spacer means positioned within said housing on each side of said drive gear means.

5. The two-stage compressor defined in claim 1, in combination with a closed refrigeration system including a high pressure reservoir, a control valve assembly and a heat exchanger assembly, said third passageway being operatively connected to said high pressure reservoir, and said first passageway being operatively connected to said heat exchanger.

6. The combination defined in claim 5, additionally including a molecular sieve positioned between said compressor and said control Valve assembly, a pressure gage positioned between said high pressure reservoir and said control valve, and `at least one particulate filter means positioned between said high pressure reservoir and said heat exchanger means.

References Cited UNITED STATES PATENTS 1,288,966 12/1918 Nielsen 23o-183 3,206,106 9/ 1965 Woolfenden 230-183 MEYER PERLIN, Przmm'y Examiner.

U.S. Cl. X.R.

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