US1922132A - Refrigeration - Google Patents

Description

Aug. 15, 1933. MES REFRIGERATION Filed Feb. 23, 1928 2 Sheets-Sheet 1 F, .5. INVENTOR." 7g Bna if0i3d B.J[o,lmes,

I x k BY c .93 i i ATTORNEYS.

B. B. HOLMES REFRIGERATION Aug. 15, 1933.

Filed Feb. 23, 1928 2 Sheets-Sheet 2 INVENTOR Bitagijlond 1?. Holmes,

MhJ

ATTORN EYS.

Patented Aug. 15, 1933 Lii-ZZJZSZ FECE 13 Claims.

This invention relates to refrigeration and particularly to a refrigerating device of the compressor, condenser, evaporator type.

.One characteristic of the invention is the use of a combined motor and compressor, both of the expansible chamber type, and having a single force transmitting abutment between the two. This motor-compressor may take various forms, but in its preferred form comprises a liquid containing U-tube with a submerged floating diaphragm to assure an absolute isolation of the power end from the pump end. The motor and pump are thus both of the liquid piston type.

The liquid abutment above described is oper ated in one direction by steam or other vapor pressure and in the opposite direction by evaporator pressure, 1. e., by the relatively low pressure in the evaporator of the refrigerating circuit preponderating over condenser pressure on the steam side. This arrangement has important results. In the first place it secures a simple motor devoid of all fly. wheels and related parts. In the second place it introduces a tendency toward inherent regulation, because as the evaporator temperature is reducedevaporator pressure is similarly reduced and the frequency of action of the pump is reduced because of the increasingly slow return stroke; Thus the speed of the pump varies with the demand for refrigeration.

Another feature of the invention is that it is operated by heat energy instead of by mechanical power. It thus oifersfor the first time a practical domestic refrigerating device of the compressor type (as contradistinguished from the absorption type) which may be operated by heat energy. There are many cases where no other energy is available.

The invention; however, derives its fullest pos- 4 sibilities when combined with a domestic water heating plant, because-it is capable of being so combined with a plant of this character as to conserve all the heat generated i. e., the waste heat of the burner, the rejected heat of the steam or other vapor pressure motor, and the heat rejected by the reversed thermal-cycle of the refrigerating machine.

The present refrigerating mechanism is capabio of interposition between the ordinary burner source of heat and the tank, in such a way as to deliver to the tank virtually all of the heat generated by the burner and yet cause this heat in its passage from the burner to the storage tank to operate the refrigerating mechanism. The refrigeration becomes a by-product of the water heating process, and it is technically possible to derive from the operation of a water heating plant heating one hundred and fifty to two hun dred gallons of water per day, sufiigcient refrigeraticn to cool a large ice box and freeze from twenty to thirty pounds of ice per day.

It the appears that a domestic hot water installs; of normal capacity can be availed of to furnish more refrigeration than would ordi narily be necessary. This is an important possibiiity, because the present domestic refrigerating systems, whether of the mechanical compressor type or of the absorption heat operated type, involve an almost prohibitive operating cost if the freezing of any substantial quantity of water be attempted.

In the embodiment of the invention to be described, a heating unit, for example, a gas burner, heats a boiler and generates vapor, ordinarily steam. This steam acts the power cylinderof the combined motor compressor to compress a volatile refrigerant. If water is used on the power side, anhydrousammonia, sulfur-dioxide or methyl-chloride may be used as the refrigerant. as they all evaporate, at refrigerating temperatures, under pressures sufficient to produce the reverse movement of the compressor-motor.

Any other suitable volatile refrigerant meeting this requirement may be substituted, but in the present discussionthe use of sulfur-dioxide as the refrigerant will be assumed.

The steam generated in the boiler operates the motor and from the motor to a condenser in the water storage tank, from which the con densate returns, by a simple trap arrangement, to the boiler. The refrigerant is drawn from the evaporator by the compressor and is compressed and delivered under pressure to a second condenser in which it is condensed partly by cool supply water flowing to the storage tank, and partly (at the timeswhen this flow does not occur) by water from the storage tank which flows in a thermal-siphon circuit in contact with the refrigerative condenser. In this way the heat rejected by the motor condenser and the heat rejected by the refrigerator condenser are both usefully applied. Finally the waste heat of the burner is availed of by passing the products of combustion through a flue in heat exchanging relation with the water in the storage tank.

A pref-erred embodiment of the invention is illustrated in the accompanying drawings, in

which,-

' Fig. l is an elevation, partly diagrammatic, of a combined water heating and refrigerating installation.

2 is a plan view of the evaporator used in the refrigerated chamber.

Fig. 3 is a right side elevation thereof.

Fig. 4 is a vertical axial section of the combined motor and compressor.

Fig. 5 is a section on the line .5-5 of Fig. 4.

Fig. 6 is a view looking upward from the under n v i of a cover plate for the compressor end of the motor compressor.

Fig. 7 is a plan view of a throttle plate used between the steam chest and the working space of the motor end of the combined motor and compressor.

The mo tor compressor unit, which is of general utility in the refrigeration field, whether combined or not with a hot water storage tank, will first be described. This unit comprises a casing 11, U-shaped in cross section, the upper right hand portion of which serves as a pump chamber 12 and the upper left hand portion of which serves as a motor chamber 13. The working abutment between these two chambers is made up of liquid, or preferably two liquids, such as oil, indicated at 14, floating above water, indicated at 15. The use of some water is convenient where the motive power is steam, because there will inevitably be some condensation in the chamber 13 and this must be collected and returned to the boiler. The use of the oil bath between the water and the chamber 13, is considered desirable, first, because it acts as a heat insulating medium and reduces condensation in the chamber 13, and because it causes the valves hereinafter described to seat more tightly, and lubricates the valve mechanism.

The use of oil 14 immediately below the working space 12 is preferred because the oil is inert relatively to the sulfur-dioxide or other refrigerant used. It is also vitally essential to isolate the water 15 completely from the refrigerant in the compression chamber 12, particularly because of chemical reactions which would occur in the case of certain refrigerants, notably sulfurdioxide and ammonia. To effect this isolation there is mounted within the oil bath 14, and below the chamber 12, a diaphragm or bell 16 which has a pendant rim sealed by an annular mercury bath 1'? into which this rim dips in all positions of the bell. The screw plug 13 is merely for the purpose of venting the bell when the device is first put in use. Within the mercury seal, and in a position to seal with the bell 16, if this moves slightly below its normal range of movement, is an annular gasket 19. In the normal operation of the device this gasket does not function, but when the system is shut down the refrigerant pressure heavily predominates. Under such circumstances the bell 16 seals on the gasket 19 and relieves the mercury seal 17 of the pressure to which it would otherwise be subjected. Except for this gasket the mercury seal would be blown out under such circumstances.

The bell 16 with the mercury seal isolates the working space 12 from the water 15 and preeludes any reaction between the water and the refrigerant. It serves another useful purpose, in that the bell, shifting as the liquid is displaced, operates the inlet and discharge valves of the steam working space 13.

This result is secured by a mechanism consisting of link 21 pivoted at 22 to the bell 16 and connected by a bell crank 23 with the second link 24. Bell crank 23 is pivoted at 25 to the shell 11 and has pivotal connections with links 21 and 24, as shown. The link 24 is hinged to a swinging arm 26 which is pivotally supported at 27 on the head 28 of the motor chamber 13. Also pivoted at 2'7 is a valve actuating arm 29 whose swinging end is connected by springs 31 with the pivot point 32 which connects the link 24 and the arm 26.

Pinned to the arm 29 is the stem 33 of the steam inlet valve 34 and the stem 35 of the steam exhaust valve 3% Valve seats down wardly on a seat 37 and the valve 36 seats upwardly against a seat 38. Collision of the valves with their respective seats limits the upward and downward motion of the swinging arm 29 and the parts are so arranged that when the bell 16 approaches the desired limit of its downward motion the resulting upward movement of the arm 26 carries the line of action of spring 32 above the pivot 27. When this occurs the arm 23 snaps upward from the position shown in Fig. 4, closing the exhaust valve 36 and opening the steam inlet valve 34. This shifting of the valves admits steam under pressure to the chamber 13 and the resulting depression of the liquid t the left of the device results in a rising of the bell 16. When this approaches its upper limit of motion the line of tension of the spring 5 31 passes below the pivot 27 reversing the valves, i. e., restoring them to the position shown in Fig. 4.

The valve seats 37 and 38 are at the upper end of a steam chamber 39 above and forming a sort of extension of the working space 13. The two spaces are partially isolated from each other by a diaphragm plate 41 held in place by a screw 42 and provided with relatively restricted ports and 44 through which the valve stems 35 and pass freely. Leading horizontally from the chamber 39 is a passage 45 which communicates by a dip pipe 46 with the lower portion of the interior oi the U-tube shell 11. In other words, the dip pipe 46 dips below the upper level of the water 15. The effective area of the dip pipe 16 is materially larger than the efiective area the two openings 43 and 44.

The purpose of this is as follows: When steam. is admitted to the chamber 13 a portion of it will condense, and the resulting condensate will pass through the oil layer 14 to the water bath 15. The gradual accumulation of water in the water bath reduces the clearance in the chamber 13 so that in the normal exhaust stroke the oil 14 will rise into contact with head 28 and tend to enter the chamber 39. The throttling effect of the ports 43 and 44 however is purposely made sufiicient to check this flow of oil into the chamber 39 and to cause the resulting pressure to be relieved by flow of water up the dip pipe 46 and to the passage 45 from which it flows by way of a connection 47, hereinafter described, back to the boiler.

A layer of insulation 48, of cork or the like, surrounds the motor chamber to reduce the loss of heat.

The inlet port 50 to the compressor working space 12 is restricted and is connected to refrigerator vapor line 49 through the inlet check valve 51. Discharge is by way of a plate valve 52 which rests on an annular seat 53 clamped between the upper end of the casting 11 and a removable head 54. The valve 52 does not seat perfectly but is designed to permit a slow seepage of oil back to the space 12. This is desirable to accommodate slight variations in the working stroke incident to the inherent variations in evaporator pressure and slight variations in the seating tendencies of the steam valves. The effect is to maintain practically no clearance in the compressor.

The head 54 is provided with a spiral pendant rib 56 surrounding the restricted discharge port 5'7 serving to limit the lift of the valve 52. The

interval between the successive convolutions of the rib 56 offers a curved passage in which a centrifugal oil separating action takes place, so that the compressed refrigerant is virtually freed of oil before it flows out through the restricting port 57.

The pipe 58 is used to conduct cooling water through the water bath 15 for the purpose of limiting the transfer of heat from the steam or motor chamber 13 to the compressor chamber 12. Cooling water from any source may be circulated through this pipe.

A preferred mode of using the motor compressor unit above described will now be explained with reference to Fig. 1.

61 is a water storage tank which as usual would be partly or wholly heat-insulated, the insulation not being illustrated in the drawings. 62 is a heating unit adequate to heat the contents of the boiler 61 to the proper temperature, and here shown as a Bunsen burner fed with gas through the pipe 63. The burner 62 is mounted within the depending annular water leg of a small cylindrical boiler 64 which is enclosed in an insulating mufiie 65. The mufile communicates by a flue 66 with a heat economizing pipe 67 which extends through the tank 61 and discharges through a discharge flue 68. From the top of the boiler 64 there leads a high pressure steam pipe 69 which as clearly shown in Fig. 4 communicates with the steam inlet above the valve 34. There is a pipe 71 which leads from the discharge port above the exhaust valve 36 to a larger pipe 72 extending from end to end of the storage tank 61 so that the pipe 72 is surrounded by the coolest water in the storage tank, i. e., the water near the bottom of the tank. The condensate forming in the pipe 72 discharges by way of the pipe 73 and check valve 74 to a gravity return pipe 75 with which the connection 47 communicates. The pipe 75 leads through a check valve 76 to the boiler 64. The functions of the check valves 74 and 76 will later be described.

77 represents a gas regulating valve of any known type which is subject in gas-valve closing direction to pressure in the boiler. The arrangement is such that rising pressure in the boiler 64 will reduce the flow of gas to the burner 62. This arrangement has not been illustrated in detail because mechanisms of this character are so well known as to be readily understood, and the mechanical details of this structure are not a feature of the present invention. All that is required is some means for reducing the input of heat on increase of pressure, to the end that a substantially constant boiler pressure be maintained.

The discharge port 57 of the compressor is connected by the pipe 78 with the refrigerant condenser which consists of a pipe 79 surrounded by a larger pipe 81. The compressed refrigerant flows through the pipe 79 and is surrounded by water flowing through the pipe 81. The pipe 81 is connected at both ends by fittings 82 and 83 with ends of the tank 61. Thus there may be at any time a thermo-siphon circulation of water through the pipe 81. The main supply connection for the tank 61 is made at 84 so that when water is drawn from the tank 61 through the outlet connection 85 the entering cold water flows through the pipe 81, thus offering the lowest available temperature for condensing the refrigerant. The cooling pipe 58 is shown connected by branches 86 with the pipe 81, but may be connected in various other ways to provide a circulation of cooling water through the pipe 58. The condenser pipe 79 discharges through pipe 87 into the float chamber 88 where the liquid refrigerant accumulates. It discharges under the control of a float 89 and connected needle valve 91 into a manifold 92 from which it flows through a plurality of parallel evaporator loops 93 to a manifold 94 which is connected by the vapor pipe 49 with the inlet valve 51 of the compressor. A drain connection 90 allows back flow of liquid refrigerant from manifold 94 to manifold 92.

The parts numbered 88 to 94 are enclosed within a refrigerator, indicated convenionally at 95. The ports 50 and 57 have been described as restricted and are designed to perform a wiredrawing function, it being, as hereinafter described, essential to the satisfactory operation of the device that these ports be more restricted than the analogous steam ports on the motor side. It being understood that the system is suitably charged, that the burner 62 is lighted and. that the pipe 84 is connected to the city water supply so as to furnish water under pressure to take the place of that which may be drawn off through the outlet connection 85, the operation of the device is as follows:

In the position shown in Fig. 4 the motor space 13 is connected to the condenser and hence is subject to low pressure. The evaporator coils 93 are discharging through the inlet valve 51 into the pump space 12, depressing the oil level and with it the bell 16. In other words, the inlet stroke of the compressor and the exhaust stroke of the motor will take place concurrently under I When the bell 16 reaches its limit of downward motion the spring 31 will pass the critical point and shift the valves 34 and 36 closing the exhaust valve 36 and opening the steam valve 34. The high pressure steam entering the chamber 37 will depress the liquid level in the space 13 with a consequent rise of liquid level in the space 12 and upward movement of the bell 16. This motion proceeds until the level of the oil 14 reaches the valve 52, displacing the compressed refrigerant past this valve and through the pipe 78. At or about this time the steam valves will be again reversed.

The cycle just described is recurrent and results in the discharge of compressed refri erant through the condenser pipe 79 assuring its liquefaction in such pipe and its delivery in liquid form to the float chamber 88. From there it flows past the float controlled needle valve, through the expansion coil 93 and in the vapor state by way of pipe 49 and valve 51, back to the compressor chamber.

The steam exhausting through the valve 36 enters the condenser pipe 72 where it is condensed and the condensate flows downward through the pipe 73 to the check valve 74. On each exhaust stroke of the mo or the pressures will substantially equalize so that the static head in the pipe 73 will suffice to feed the condensate through the check valve 74 to the gravity pipe 75.

It also is obvious that the accumulation of condensate in the lower part of the casing 11 will result in the overflow of a certain amount of condensate upward through the pipe 46 to the gravity pipe 75.

During each pressure stroke in the working space 13 boiler pressure is established in the connection 47. Thus pressure at the upper and lower ends of the gravity pipe '75 substantially equalizes during each power stroke. The effect of such pressure is to hold the check valve 74 closed while the static head in the gravity pipe 75 feeds the condensate therein past the check valve '76 back to the boiler. The check valve 76 prevents back flow from the boiler. The check valve 74 prevents steam pressure in chamber 13 from reaching the condenser.

The pressures in chamber 13 and the boiler and condenser cannot exactly equalize because of the restriction offered in the passage of steam into and out of the chamber through the valves. To reduce this difference in pressure and thus reduce the gravity head necessary to allow the condensed steam to return to the boiler, ports 50 and 57 in the pump chamber are made substantially smaller in cross section than the steam valve ports so that the wire drawing effect which must take place when filling and emptying the cylinders, takes place mostly on the compressor side of the machine and as little as possible on the motor side. This ensures the condensate re turn with a small gravity head.

In effect, therefore, the device includes a sim ple form of drip trap associated with the motor and operating to return to the boiler condensate from the motor as well as condensate from the condenser. As the device is tightly sealed and vapor operates in a closed cycle, the steam and water circuit is wholly free of air and remains so, just as does the refrigerant circuit. The regulative action is as follows:

As the temperature in the refrigerator $5 falls, the pressure in the evaporator coils 93 will fall. This pressure causes the return stroke of the motor and as the desired temperature is approached the return stroke becomes slower and slower, thus reducing the number of operating cycles in a given unit of time. This slowing up will continue until the proper rate is established. A smaller number of cycles in a given unit of time necessarily results in a lowered steam consumption with a consequent tendency toward rise of boiler pressure. This tendency is corrected by the regulating valve '77 which reduces the flame at the burner 62 to maintain a constant pressure. Accordingly the device operates at a rate responsive to the demand for refrigeration. This may not conform at times to the demand for heated water, in which event it would be an obvious expedient to supply auxiliary temperature controlled heating means to the tank 61. Ordinarily, however, this is not believed to be necessary.

An important characteristic of the invention is that the entire heat of the burner 62 except for inevitable radiation losses, is delivered to the tank 61. Thus the total input of heat to the tank 61 is virtually the same as it would be were no refrigerating apparatus used.

It is not essential that the motive fluid be steam, as various volatile liquids might be substituted for water. Nor is it essential that the steam and refrigerative condensers be associated with a domestic hot water tank, for obviously the device would be operative if these condensers were cooled in any other effective way. Consequently certain elements of the invention are claimed separately and develop useful characteristics in specifically different combinations.

The mechanical structure illustrated has been developed to secure the utmost simplicity, but is subject to wide variation, which is contemplated. The sealed bell 16 is merely a floating diaphragm and any equivalent diaphragm structure may be substituted.

What is claimed is,--

1. The combination of a steam motor having a condenser; a refrigerating plant driven thereby and including a compressor, a condenser and an evaporator connected in a closed circuit; a hot water storage tank; and means for transferring to the water in said tank the heat rejected by both said condensers.

2. The combination of a steam motor having a condenser; a refrigerating plant driven thereby and including a compressor, a condenser and an evaporator connected in a closed circuit; a hot water storage tank; means for feeding water to said tank; and means for transferring to the water in said tank the heat rejected by said condensers, the heat rejected by the refrigerating plant condenser being taken up by said feed water when the latter flows.

3. The combination of a steam motor having a boiler and condenser connected therewith; a source of heat for said boiler; a refrigerating plant driven by said motor and including a compressor, a condenser and an evaporator connected in a closed circuit; a hot water storage tank; means for transferring to the water in said tank the heat rejected by both said condensers, and the waste heat from said source.

4. The combination of two closed circuits, each containing a different volatile liquid, and each including an evaporator, a condenser and a variable volume chamber, said chambers for the two circuits being isolated from each other as to fluid flow, but being mechanically related to vary inversely as to one another in volume; valve means for performing a cyclic alternating volume variation of said chambers primarily by opposing therein the evaporative pressure of alternate circuits to the condenser pressure of the opposite circuit; means for supplying heat at different temperatures to said evaporators; and means for absorbing the heat rejected through said condensers.

5. The combination of two closed circuits each containing a different volatile liquid, and each including an evaporator, a condenser and a variable volume chamber, said chambers for the two circuits being substantially isolated from each other as to heat and wholly as to fluid flow, but being mechanically related to vary inversely as to one another in volume; valve means for performing a cyclic alternating volume variation of said chambers primarily by opposing therein the evaporative pressure of alternate circuits to the condenser pressure of the opposite circuit; means for supplying heat at different temperatures to said evaporators; and means for absorbing the heat rejected through said condensers.

6. The combination of two closed circuits one a power circuit containing a volatile pressure generating fluid and including a relatively highpressure evaporator and a relatively low-pressure condenser, and the other a refrigerating circuit containing a volatile refrigerant and including a relatively low-pressure evaporator and a relatively high-pressure condenser; a motor compressor unit intercalated as a motor in the first and as a compressor in the second of such circuits, and forming a mechanical connection between them while otherwise substantially isolating them from each other; valve means for operating said motor compressor unit alternately by the preponderance of pressure in the high pressure evaporator of the first circuit over the pressure in the high pressure condenser of the second circuit and by the preponderance of lowpressure evaporator pressure in the second circuit over the low-pressure condenser pressure of the first circuit; and means for supplying heat at different temperatures to said evaporators.

7. The combination of two closed circuits, one a power circuit containing a volatile pressure generating fluid and including a relatively highpressure evaporator and a relatively low-pressure condenser, and the other a refrigerating circuit containing a volatile refrigerant and including a relatively low-pressure evaporator and a relatively high-p essure condenser; a motor compressor unit intcrcalated as a motor in the first and as a compressor in the second of said circuits, and forming a mechanical connection between them while otherwise isolating them from each other; valve means for operating said motor compressor unit alternately by the preponderance of pressure in the highpressure evaporator of the first circuit over the pressure in the high-pressure condenser of the second circuit and by the preponderance of low-pressure evaporator pressure in the second circuit over the low-pressure condenser pressure of the first circuit; means for supplying heat at different temperatures to said evaporators; and automatic means for maintaining the pressure in the highpressure evaporator substantially constant.

8. The combination of two closed circuits, one a power circuit containing a volatile pressuregenerating liquid, a relatively high pressureevaporator and a relative y low-pressure condenser, and the other a r rating circuit containing a volatile refrigerant and including a relatively low-pressure evaporator and relatively high-pressure condenser; a motor-compressor unit including a single acting expansible chamber motor in the power circuit and a single acting expansible chamber compri r d ectly connected therewith and in the refrigerat -g circuit; and valve means for operating motor-compressor in one direction by pressure preponderance of the high pressure evaporator over the high-pressure condenser and in the reverse direction by pressure preponderance of the low-pressure evaporator over the low-pressure condenser.

9. The combination of two closed circuits, one a power circuit containing volatile pressuregenerating liquid, a relatively high pressureevaporator and a relatively low-pressure condenser, and the other a refrigerating circuit containing a volatile refrigerant and including a relatively low-pressure evaporator and a relatively high-pressure condenser; a motor compressor unit including a single acting; oxpansible charmber motor in the power circuit and a single acting expansible chamber compressor dire ly connected therewith and in the refri, ating circuit; valve means for operating said motor compressor in one direction by pre Lire preponderance of the high pressure evaporator over the high-pressure condenser and in the reverse direction by pressure preponderance of the low-pressure evaporator over the low-pressure condenser; and means for maintaining high-pressure evaporator pressure substantially constant.

10. The combination of two closed circuits each containing a different volatile liquid and each including an evaporator; a condenser and a variable volume chamber, said chambers for the two circuits being formed in the upper portions of a U-tube and isolated from each other by a body of liquid whereby such chambers vary inversely in volume; means for performing a cyclic volume variation of said chambers by opposing therein the evaporative pressure of alternate circuits to the condenser pressure of the opposed circuit; means for supplying heat at different temperatures to said evaporators; and means for absorbing the heat rejected through said condensers.

11. The combination of two closed circuits each containing a different volatile liquid and each including an evaporator, a condenser and a variable volume chamber, said chambers for the two circuits being formed in the upper portions of a U-tube and isolated from each other by a body of liquid whereby such chambers vary inversely in volume; secondary means moving with said body of liquid and serving positively to isolate said chambers; means for performing a cyclic volume variation of said chambers by opposing therein the evaporative pressure 01" alternate circuits to the condenser pressure of the opposed circuit; means for supplying heat at different temperatures to said evaporators: and means for absorbing the heat rejected through said condensers.

12. The combination of two closed circuits each containing a different volatile liquid and each including an evaporator, a condenser and a variable volume chamber, said chambers for the two circuits being formed in the upper portions of a U-tube and isolated from each other by a body of liquid whereby said chambers vary inversely in volume; an abutment moving with said body of liquid and serving completely to isolate said chambers; valve means actuated by the motion of said abutment and controlling the alternate admission and discharge of pressure fluid generated in the evaporator of one circuit to and from the variable volume chamber of the same circuit, whereby said circuit operates as a motor circuit, pump valve means associated with the other variable volume chamber; means for supplying heat at different temperatures to the two evaporators; and means for absorbing heat rejected through said condensers.

13. The combination of a motor circuit and a refrigerator circuit each containing a different volatile liquid and each including an evaporator. a condenser and a variable volume chamber, said chambers for the two circuits varying inversely in volume and one being a motor and the other a compressor chamber; valve mechanism for freely admitting and exhausting pressure fluid to the motor chamber from the evaporator and from the motor chamber to the condenser of the motor circuit alternately; valve means including throttling orifices controlling the admission to and discharge from the compressor chamber; a gravity condensate drain connection from the motor chamber to the evaporator of the motor circuit; a check valve preventing back flow therein: a gravity condensate drain connection from the condenser to the first named drain connecion; and a check valve preventing back flow in the last named connection.

BRADFORD B. HOLMES.

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