US3321926A - Fluid-actuated cryogenic refrigerator - Google Patents

Description

May 30, 1967 F. F. CHELLIS FLUID-ACTUATED CRYOGENIC REFRIGERATOR 5 Sheets-Sheet 1 Filed Dec. 5, 1965 JNVLN'IOR Fred F. Chellis Fig.1

Attorney May 30, 1967 F. F. CHELLIS 3,321,926

FLUID-ACTUATED CRYOGENIC REFRIGERATOR Filed Dec. 5, 1965 5 Sheets-Sheet,

Fred F Challis Attorney May 30, 1967 F. F. CHELLIS FLUID-ACTUATED CRYOGENIC REFRIGERATOR 5 Sheets-Sheet 3 Filed Dec. 5, 1965 Fig. 7 Fig. 8

Fig. 5 Fig. 6

lNV EN'TOR. Fred F CheHis Attorney United States Patent 3,321,926 FLUID ACTUATED CRYOGENIC REFRIGERATUR Fred F. Chellis, Manchester, Mass, assignor to Arthur D. Little, Inc, Qarnbridge, Mass, a corporation of Massachusetts Filed Dec. 3, 1965, Ser. No. 511,796 Claims. (Cl. 62-6) This invention relates to apparatus for developing low temperature cryogenic refrigeration, and more particularly to refrigeration apparatus which includes a novel valve system which makes the apparatus self-regulating, and in a preferable form requires no external driving means other than a source of the high-pressure expansible fluid used in the refrigerator. It further relates to the refrigeration apparatus for producing net refrigeration in a system in which some of the work extracted from the compressing, cooling, and expanding of a fluid may be in the form of thermal energy, wherein the fluid leaving the system is at a temperature higher than that at which it entered the system.

In United States Patent No. 2,966,035 there is described a refrigeration method and apparatus which is directed to a so-called no-work cycle in which refrigeration is obtained by removing more sensible heat from a system than is taken into the system by the refrigerating fluid used. In operation, however, both thermal and mechanical energy are delivered by this cryogenic refrigerator. Although the cycle described in U.S.P. 2,966,035 has a been found to be very successful in producing refrigeration, even as low as K., the method and apparatus of that cycle possess an inherent disadvantage in that the equipment required to control the flow of fluid and thus to achieve refrigeration by the method and cycle described is expensive and diflicult to assemble.

It would therefore be desirable to have available a more simple, eflicient, and reliable means for controlling the valve operation of this type of clyogenic refrigerator and thereby supply high-pressure fluid and discharge lowpressure fluid in proper sequence to achieve the refrigeration method described in U.S.P. 2,966,035. Since the refrigerator requires a high-pressure fluid to operate on, it would also be desirable if the driving means were fluid actuated. The apparatus of this invention provides a fluidactuated driving system incorporating valving means which are an integral part of a refrigerator operating on the cycle described in UB1. 2,966,035. The driving system of this invention can also be used with pulse-tube type refrigerators such as shown and described in U.S.P. 3,188,818.

Taking for example a small gas-operated refrigerator it may be pointed out that such a device can be operated on shop compressed air to find many uses. Most medical and biology laboratories require small amounts of lowtemperature refrigeration for such work as the preparation of tissues for microscopic examination and the freezing of solutions. Usually, refrigeration needs are met by liquid nitrogen or solid CO For those requiring large quantities of continuous refrigeration, this is not too difficult. But it is not easy to obtain just one liter of liquid nitrogen or one pound of solid CO and if a small amount of cooling is desired continuously for weeks around the clock, it is diflicult to arrange for this using cryogenic fluids or solids. Many experiments that require temperatures below 233 K. (40 C.)the nominal lower limit of Freon refrigeration-must be performed at temperatures fixed by the refrigerant used, e.g., liquid nitrogen (about 77 K.) and solid CO (about 195 K.). Temperatures between 100 K. and 230 K. have been difficult to realize experimentally. There is therefore a need for a small refrigerator which requires only a source of compressed gas, whether air, helium or some other gas.

It is therefore a primary object of this invention to provide a cryogenic refrigerator which incorporates a self-regulating fluid-actuated driving system, the fluid being used as the refrigerant in the refrigerator. It is an other object of this invention to provide apparatus of the character described which is particularly suitable for performing the cryogenic refrigeration cycle described in U.S.P. 2,966,035 and 3,188,818. It is yet another object to provide a cryogenic refrigerator which may be connected to a high-pressure fluid source and run continuously over a long period of time without attendance or maintenance. Other objects of the invention will in part be obvious and will in part be apparent hereinafter.

The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawings in which FIG. 1 is a longitudinal cross-section of the cryogenic refrigerator of this invention showing the fluid-actuating valving system as an integral part of the refrigerator;

FIG. 2 is a cross-section of the refrigerator of FIG. 1 taken along line 2--2 of that figure;

FIG. 3 is a cross-section of the valving system of FIG.

'1 showing one embodiment of a Work extracting means;

FIG. 4 is a cross-section of the valving system showing another embodiment of a work extracting means; and

FIGS. 5-8 are partial cross sections of the valving system and displacer illustrating the operation of the apparatus during one complete cycle.

The refrigerator of FIG. 1 comprises an external housing 10 sealed on the bottom end by a plug 11 of a material which has high thermal capacity at the refrigeration temperature. Within the cylindrical housing In is a displacer 12 which reciprocates up and down to define within the housing a warm fluid chamber 13 and a cold or refrigerating chamber 14. These are, of course, of variable volume, the volume d-epending upon the position of the displacer. Chambers 13 and 14 are in fluid communication through a fluid flow path which contains suitable heat-storage means. In the embodiment of the refrigerator shown in FIG. 1, the fluid flow path comprises an axial conduit 15 which communicates through the valving system between warm chamber 13 and a regenerator 16 which is located within the displacer 12. The regenerator may be formed of packed lead balls 17, fine screening, of wire, or of any other suitable heatstorage material. From the regenerator 16 the fluid floW path continues in the form of radial passages 18 and a narrow annular passage 19 which is defined by a smaller diameter lower section of the displacer and the internal walls of the refrigerator. A heat station 21 is positioned around the external housing 10 in heat conducting relationship with the cold chamber 14. Heat station 21 serves to stabilize the temperature of the cold chamber 14 and hence the refrigeration delivered at the surface of bottom end plug 11.

The fluid-actuated driving system of this invention is indicated generally by the numeral 23 and it will be seen to be positioned in fluid-tight relationship with the refrigerator. In order to do this, external housing 10 terminates at its upper end in a threaded section 25 which is adapted to be joined to a threaded base 26 of the driving system. A sealing ring 27 completes the fluid-tight connection. Base 26 conveniently has a flange 28 which is adapted for joining to a refrigerator support 29.

The displacer 12 has at its upper end a threaded connector piece 33 which is joined to the main displacer 12 through sealing ring 34 and forms a fluid-tight seal with threaded section 25 through a sealing ring 35. The refrigerator has an adaptor 38 which is arranged to permit connecting it to a supply of compressed fluid through means not shown. Within adaptor 38 there is provided a high-pressure gas inlet 39 which communicates directly into warm chamber 13 of the refrigerator. A section 41 of the main displacer extends into the valve housing which is completed by a vertically extending section 42 having a removable end plug 43. A sealing ring 36 is provided to insure that chamber 13 remains fluid tight.

The valving mechanism of this fluid-actuated driving means is indicated generally by the numeral 45. It is made up of inlet poppet valves 46 (of which there may be two or more) and a discharge poppet valve 47. All of these poppet valves are mounted on a yoke 49 which is located in a small valve chamber 44 within the top of the displacer. The inlet poppet valves 46 are connected to a yoke 4-9 through valve stems 48 which pass down through ports 53 drilled in the threaded displacer connector section 33. As will be seen, the outlet poppet valve 47 is mounted directly on the yoke, and integral with it is a vertical extension 50 which is terminated at the upper end in a threaded section 51 on which is mounted a valve shifer collar 52. Associated with the valve mechanism are three springs 55, 56, and 57, the purpose of which will become apparent in the description of the operation of the refrigerator. Guide vanes 58, mounted on the valve extension 50, serve to position it within the displacer extension 41.

In FIG. 1 the paths of the high-pressure fluid and of the exhaust fluid may be traced. The high-pressure fluid entering through inlet 39 into warm chamber 13 passes through ports 53 into valve chamber 44 and thence by way of conduit 15, regenerator 16, radial passages 18 and annular passage 19 into the refrigeration chamber 14. The path of the low-pressure exhaust fluid is the reverse of the high-pressure fluid up to the point where the exhaust fluid enters chamber 44. It then is discharged through poppet valve 47 into an annular passage 64 which is defined between the displacer extension 41 and the valve extension 50. The low-pressure fluid then enters chamber 65 to pass around collar 52 into outlet chamber 66 and thence through throttle valve 67, the purpose of which is to modulate the flow of fluid from the system and control the operation of the refrigerator during the low-pressure portion of the cycle. It will, of course, be understood that the low-pressure fluid may exhaust to the atmosphere (open cycle) or may be returned to the system by way of suitable conduits which lead first into a compressor and then into a high-pressure storage system (closed cycle).

FIG. 3 illustrates a modification of the fluid-actuator and includes a modified sealing system as well as means for absorbing work energy developed in the system. This is desirable since the combination displacer-piston used (displacer 12 plus displacer extension 41) develops some mechanical energy and a work absorbing means can conveniently be employed as a form of governor to regulate the operation of the refrigerator.

In FIG. 3 two sealing-rings 70 and 71 replace the single sealing ring 35 of FIG. 1 between the upper end of the displacer and the cylindrical housing. Between the grooves in which sealing rings 70 and 71 are located there is provided a narrow annular passage 72 which is in fluid communication by way of bleed-off line 73 with the low-pressure side of the system. This arrangement prevents any high-pressure fluid in chamber 13 from leaking into the cold voids of the refrigerator where contaminants can freeze and interfere with the movement of the displacer. This seal is the subject of my copending application Ser. No. 503,726, filed Oct. 23, 1965.

Energy may be extracted from the system through the development of friction. This can conveniently be done by providing a high-pressure annular channel 76, connected to the high-pressure inlet through conduit 77. An elastic band 78 seals the channel 76 and by reason of the high-pressure fluid acting on it, it applies pressure against suitable pressure-applying members 79 which are in frictional contact with a portion of the surface of the displacer extension 41. As this extension moves up and down friction is developed at these contacting surfaces thus removing energy from the system. Any other suitable means, e.g., springs, screws, etc., may of course be used in place of tfuid pressure to maintain the members 79 in contact with the displacer extension 41.

Other minor modification included in the embodiment of FIG. 3 include an enlarged extension 80 of the valve extension 5% on which the collar 52 is mounted. The lowpressure fluid path also includes ports 81 which communicat-e between annular passage 64 and 82 which connect directly to an upper exhaust fluid passage 83 and an outlet 84.

FIG. 4 is a cross-sectional view of a portion of a refrigerator constructed in accordance with this invention showing another modification of an energy-absorbing means which may be associated with the fluid-actuated valve system. As pointed out in conjunction with the description of FIG. 3, some work-absorbing means is desirable in the refrigerator. In FIG. 4 like reference numerals refer to like apparatus components in FIGS. 1-3.

The work-absorbing means of FIG. 4 is hydraulic in character and incorporates an additional fluid chamber and piston. The piston, in its vertical motion, does work on a fluid by moving it from one section of chamber to another through a constriction or orifice. The fluid chamher is located above chamber 13 and in the modification shown in FIG. 4 is defined by a lower plate 88 and an upper plate 89 which are permanently aflixed to the inner wall of the refrigerator housing 10. Suitable sealing means such as O- ring seals 90 and 91 are provided to permit the displacer extension 4 1 to move vertically within the fluid chamber 92 and maintain it fluid tight. Attached to the.

displacer extension 41 is a piston 93 having an O-ring seal 94. As the displacer moves up and down it moves piston 93 in chamber 92 to transfer fluid between subchambers 95 and 96 which are connected through a conduit 97 having an orifice 98. Thus work is absorbed in the movement of the fluid through the orifice.

The cycle of the operation of the cryogenic refrigerator is shown in FIGS. 5-8 which represent the four steps of the cycle. These steps are essentially those which are described in some detail in U.S.P. 2,966,035.

In FIGS. 58 only that part of the apparatus is drawn which enters into the operation of the refrigerator in the cycle described. The displacer in these drawings is shown as a single unit 12 and the details of the regenerator and various fluid paths which are shown in FIG. 1 have not been repeated. The various springs are illustrated since they enter into the operation of the valve system. However, the details of the housing around these springs which defines the fluid flow paths are not repeated in these drawings. In all cases like numerals refer to like elements in all of the figures.

It is necessary in the operation of the refrigerator cycle to introduce high-pressure, initially cooled fluid into the refrigeration chamber 14 through the fluid flow path described. It is then necessary to expand the high-pressure fluid through the system and to further cool it by causing the exhaust valve to open, some of the fluid to discharge, and refrigeration to be delivered to the refrigerating end plug 11 which in this example is the point at which refrigeration is delivered to a load.

In describing the operation of the apparatus of this invention assume that FIG. 5 represents the position of the displacer and the valve system at the point where the displacer 12 has reached top dead center. At this step in the cycle the refrigerating chamber 14 has attained its maximum volume, the discharge valve has just opened and the fluid is just beginning to be discharged and ex= panded. It will be seen that under these circumstances the inlet valves 46 are closed and the discharge valve 47 is open. This has been brought about by the fact that collar 52 has made contact with the valve shifter spring 55 thus forcing the inlet poppet valves 46 to seat and the outlet valve 47 to open. High-pressure fluid entering through inlet 39 indicated in FIGS. -8 by the arrow exerts pressure on the poppet valves 46 and maintains them in a closed position by virtue of the pressure difference which exists between this high-pressure fluid and the fluid pressure throughout the refrigerator. This condition of the valve system obtains throughout that portion of the cycle which includes the downward movement of the displacer as indicated by the arrow in FIG. 6.

As the displacer 12 moves downwardly, the now lowpressure fluid in chamber 14 is swept out of the refrigerator as indicated by the arrow in conduit 15. Because of the high-pressure fluid in chamber 13 the inlet valves remain closed and the low-pressure fluid which gives up refrigeration to the regenerator sweeps out of the refrigerator through the low-pressure fluid path consisting of passages 64, 6-5, 66 and throttle valve 67 (see FIG. 1). The displacer is caused to move downwardly through the action of the high-pressure fluid in chamber 13 until it reaches its lowermost position. It will be seen in FIG. 7 that at this point collar 52 contacts valve shifter spring 56 and there is a point reached at which the upward force of the spring 56 overcomes the downward force of the fluid pressure in chamber 13 and snaps the valve system upwardly to close the discharge valve 47 and open the inlet valves 46. The position of the apparatus components just subsequent to the snap action exerted by spring 56 is shown in FIG. 7. At this point there is no appreciable quantity of fluid in the cold chamber 14 but warm chamber 13 has reached its maximum volume.

At this point it is necessary to move displacer 12 up- Wardly and transfer the warm high-pressure fluid into the refrigerating chamber 14 by way of the regenerator to cool it and to deliver to chamber 14 initially-cooled highpressure fluid. As the displacer 12 moves upwardly, the inlet poppet valves 46 remain open as shown in FIG. 8. The upward movement of the displacer is brought about by the fact that the pressure of the fluid in chamber 14 is greater than that pressure which is acting upon the displacer extension 41 which is, of course, within the lowpressure region of the refrigerator.

When the displacer 12 reaches its uppermost position then collar 52 contacts valve shifter spring 55' which causes the valves to snap into the position shown in FIG. 4-i.e., the high-pressure inlet valves 46 are closed and the exhaust valve 47 is opened to begin the cycle at the point described in connection with the discussion of FIG. 4. Spring 57 is included to insure that yoke 49 is always in a definite position when the unit is stopped. This prevents the valves from assuming an intermediate position wherein both are open, a situation which would prevent the unit from being self-starting.

The operation of the refrigerators of FIGS. 3 and 4 is identical to that of FIG. 1. in addition, the annular channel 76 in the apparatus of FIG. 3 is continuously maintained at high-pressure by virtue of the fact that the highpressure inlet is in constant fluid communication with this channel. The high-pressure fluid in 76 continuously forces the elastic band 78 against the pressure-applying members 79 thus maintaining continuous contact between them and the surface of displacer extension 41. The friction developed in the apparatus of FIG. 3 and the work required to move the hydraulic fluid in the apparatus of FIG. 4 serve as work extracting means.

Although the refrigerator illustrated in FIG. 1 shows only a single cold chamber, it is within the scope of this invention to incorporate the driving system shown herein in cryogenic refrigerators which are constructed to have a stepped displacer and multiple, successively colder refrigeration chambers. Each segment or step of the displacer in such a modification has a regenerator associated with it. (See for example FIGS. 6, 9 and 10 of U.S.P. 3,218,815.) The operation of the driving system and the cycle are the same as that described for the refrigerator of FIG. I.

The cryogenic refrigerator of this invention Will be seen to have its driving mechanism and valving system incorporated directly in it. No external driving means or valving system are necessary since the entire operation of the refrigerator depends only upon supplying a highpressure fluid to it. This high-pressure fluid may be shop compressed air, or compressed nitrogen, hydrogen or helium. The fluid-actuation of all parts insures a steady coordinated operation.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efliciently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

I claim:

1. In a cryogenic refrigerator in which a high-pressure fluid is delivered from a high-pressure chamber of variable volume with initial cooling to at least one refrigerating chamber of variable volume for subsequent expansion and further cooling by discharge from the refrigerator, and in which said fluid is transferred through said refrigerator by the movement of displacer means controlled through the introduction of high-pressure fluid and the discharge of low-pressure fluid, the improvement which comprises a fluid-actuated driving means which forms an integral part of said refrigerator, said driving means comprising in combination (a) an auxiliary high-pressure fluid chamber of constant volume in the upper end of said displacer;

(b) a fluid-pressure responsive piston extension integral with said upper end of said displacer and having a channel therethrough providing fluid communication between said auxiliary high-pressure fluid chamber and the low-pressure region of said refrigerator;

(c) high-pressure inlet ports communicating between said high-pressure chamber and said auxiliary highpressure chamber; and

(d) pressure-responsive, valve means associated with said inlet ports and said channel and adapted to close said inlet ports and open said channel during that portion of the refrigeration cycle when said refrigerating chamber attains maximum volume and is thereafter decreasing in volume and to open said inlet ports and close said channel during that portion of the refrigeration cycle when said high-pressure fluid chamber attains maximum volume and is thereafter decreasing in volume.

2. A refrigerator in accordance with claim 1 wherein said valve means comprises (a) a yoke;

(b) inlet poppet valves mounted on said yoke;

(c) a discharge poppet valve mounted on said yoke;

(d) a valve extension located within said channel and terminating thereabove in a collar; and

(e) spring means associated with said collar and being adapted to apply sufficient pressure to said valve means to overcome fluid pressure applied thereto thereby to effect snap action of said valve means when said displacer reaches its lowermost and uppermost positions.

3. A refrigerator in accordance with claim 1 further characterized by having work extracting means associated with said piston extension.

4. A refrigerator in accordance with claim 3 wherein said work extraction means comprises pressure-applying means in friction developing contact with said piston extension.

5. A refrigerator in accordance with claim 3 wherein said work extraction means comprises a fluid chamber, a piston afiixed to said piston extension movable within said chamber to define two subchambers and a fluid conduit having an orifice providing a fluid communication between said subchambers.

References Cited UNITED STATES PATENTS 3,188,821 1/1965 Chellis 62-6 WILLIAM J. WYE, Primary Examiner.

Claims (1)

1. IN A CRYOGENIC REFRIGERATOR IN WHICH A HIGH-PRESSURE FLUID IS DELIVERED FROM A HIGH-PRESSURE CHAMBER OF VARIABLE VOLUME WITH INITIAL COOLING TO AT LEAST ONE REFRIGERATING CHAMBER OF VARIABLE VOLUME FOR SUBSEQUENT EXPANSION AND FURTHER COOLING BY DISCHARGE FROM THE REFRIGERATOR, AND IN WHICH SAID FLUID IS TRANSFERRED THROUGH SAID REFRIGERATOR BY THE MOVEMENT OF DISPLACER MEANS CONTROLLED THROUGH THE INTRODUCTION OF HIGH-PRESSURE FLUID AND THE DISCHARGE OF LOW-PRESSURE FLUID, THE IMPROVEMENT WHICH COMPRISES A FLUID-ACTUATED DRIVING MEANS WHICH FORMS AN INTEGRAL PART OF SAID REFRIGERATOR, SAID DRIVING MEANS COMPRISING IN COMBINATION (A) AN AUXILIARY HIGH-PRESSURE FLUID CHAMBER OF CONSTANT VOLUME IN THE UPPER END OF SAID DISPLACER; (B) A FLUID-PRESSURE RESPONSIVE PISTON EXTENSION INTEGRAL WITH SAID UPPER END OF SAID DISPLACER AND HAVING A CHANNEL THERETHROUGH PROVIDING FLUID COMMUNICATION BETWEEN SAID AUXILIARY HIGH-PRESSURE FLUID CHAMBER AND THE LOW-PRESSURE REGION OF SAID REFRIGERATOR; (C) HIGH-PRESSURE INLET PORTS COMMUNICATING BETWEEN SAID HIGH-PRESSURE CHAMBER AND SAID AUXILIARY HIGHPRESSURE CHAMBER; AND (D) PRESSURE-RESPONSIVE, VALVE MEANS ASSOCIATED WITH SAID INLET PORTS AND SAID CHANNEL AND ADAPTED TO CLOSE SAID INLET PORTS AND OPEN SAID CHANNEL DURING THAT PORTION OF THE REFRIGERATION CYCLE WHEN SAID REFRIGERATING CHAMBER ATTAINS MAXIMUM VOLUME AND IS THEREAFTER DECREASING IN VOLUME AND TO OPEN SAID INLET PORTS AND CLOSE SAID CHANNEL DURING THAT PORTION OF THE REFRIGERATION CYCLE WHEN SAID HIGH-PRESSURE FLUID CHAMBER ATTAINS MAXIMUM VOLUME AND IS THEREAFTER DECREASING IN VOLUME.

Images