US2768509A - Control valve for reversible refrigerating system - Google Patents

Description

Oct. 30, 1956 Filed Oct. 6, 195 I 2 Shets-Sheet 1 HIS ATTORNEY LI J H- 23 -25 000 I4 i g INVENTOR.

JOHN T. BATEMAN BY Oct. 30, 1956 J. T. BATEMAN CONTROL VALVE FOR REVERSIBLE REFRIGERATING SYSTEM Filed Oct. 6, 1954 2 Sheets-Sheet 2 D LO Q e 7 n a V N (I) d In 5 N g fzo Ll. INVENTOR.

q- \P m JOHN T. BATEMAN f BY HIS ATTORNEY United States Patent Ofiice 2,768,509 Patented Oct. 30, 1956 CONTROL VALVE FOR REVERSIBLE REFRIGERATING SYSTEM John T. Bateman, Marblehead, Mass., assignor to General Electric Company, a corporation of New York Application October 6, 1954, Serial No. 460,654

9 Claims. (Cl. 62-1159 The present invention relates to reversible refrigerating systems and particularly to a control valve for effecting the reversal of such systems.

The reversible refrigerating systems or heat pumps,

employed for heating dwellings or other structures in thewinter and for cooling in the summer, include an indoor heat exchange unit or coil and an outdoor heat exchange unit or coil and a compressor for circulating refrigerant through the two coils. During operation of the system on the heating cycle, the indoor coil functions as a condenser and the outdoor coil as an evaporator. To reverse the functions of the two coils for operation of the system on the cooling cycle, it is necessary to reverse the connections of the compressor to the system so that the refrigerant flow will be such that the indoor coil functions as a condenser and the outdoor coil as an evaporator. Various valving arrangements have been employed for connecting the two heat exchange units or coils alternatively to the suction and discharge sides of the compressor. Due to the normal high pressure differences prevailing betweenthe two sides of the refrigerating system, very substantial forces have been required to reverse these valves and various unloading arrangements have been suggested for overcoming this difficulty. However, these arrangements, comprising a plurality of reversing'valves and an unloader, have not been entirely satisfactory from the standpoint of simplicity and cost or for securing proper operation of the system over a wide range of pressure differences within the system.

Accordingly it is a primary object of the present invention to provide for a reversible refrigerating system, a single control valve Which is of simple construction and easy to operate.

It is another object of the invention to provide a control valve for a reversible refrigerating system which is pressure balanced to permit easy operation thereof over a wide range of pressure differences within the refrigerating system.

It is a further object of the invention to provide a simple and low cost five-way valve for connecting the two heat transfer units of a reversible refrigerating system alternatively to the suction and discharge sides of the compressor.

A further object of the invention is to provide a control valve for reversible refrigerating systems including a plurality of flow control valve chambers, a single valve actuating means including a plurality of valve members and means for assuring complete simultaneous seating of each of said valve members during changeover operation of the valve.

Further object and advantages of the invention will become apparent as the following description proceeds, and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the objects of this invention, there is provided a five-way valve structure for a reversible refrigerating system, which structure comprises a high pressure valve chamber having a pair of opposed ports for controlling the flow of compressed refrigerant from a compressor to either of two heat exchange units and a low pressure valve chamber connecting the other of the two units to the suction side of the compressor through either of two inlet ports. A valve member or disc is provided in each of these valve chambers and the valve members are arranged to be actuated by a single valve actuating means so that one port in each of the chambers is closed by the cooperating valve discs upon operation of the valve actuating means. The valve chambers connecting the valve to the refrigerating system, i. e., the heat exchange units, are provided within the valve casing on opposite sides of the high pressure and low pressure chambers and communicate therewith through ports in the high pressure and low pressure chambers. The system valve chambers are so arranged and connected to the refrigerating system that the pressure differences existing within the valve structure are substantially balanced or at least reduced to the maximum pressure differential necessary to hold the valve mechanism in one or the other of its two port closing positions.

For a better understanding of the invention, reference may be had to the accompanying drawing in which Fig. 1 is a diagrammatic illustration of an air conditioning or heat pump system provided with a reversible refrigerating machine including the valve embodying the present invention, and

Fig 2 is an enlarged detailed sectional view of the changeover valve forming the subject matter of the present invention.

Referring now to Fig. 1 of the drawing, the system disclosed comprises a heat exchange unit or coil 1 arranged in a duct 2 to heat or cool air admitted to the duct through a fresh air inlet 3 and through a room return air inlet 4 and circulated over the unit 1 by operation of a blower 5 driven by a motor 6, the air discharged from the blower being returned to the room by a duct 7. The indoor unit or coil 1 is arranged to operate either as the condenser or evaporator of a refrigerating system through which refrigerant is circulated by means of a compressor 8 driven by an electric motor 9. The system also includes a second heat exchange unit or coil 11 over which outdoor air is circulated by a blower 12 driven by an electric motor 13. The blower 12 is arranged to draw outside air through a duct 14 and to discharge the air to a suitable exhaust connection (not shown).

A five-way valve 15, which forms the subject of the present invention, controls the flow of refrigerant from the compressor to the coils 1 and 11 and back to the compressor so that the refrigerating machine can be operated with the coil 1 as the condenser for heating the air passing through duct 2 or as an evaporator for cooling that air. When the system is operated with the unit 1 as the condenser and the unit 11 as the evaporator for heating purposes during the winter, hot compressed refrigerant is delivered by the compressor 8 through the high pressure discharge line 16 to the five-way valve 15. From the valve 15, the high pressure refrigerant flows through the middle fluid flow connection or conduit 17 to the indoor coil 1. In the indoor coil 1, the refrigerant is cooled and liquefied by heat exchange with the air flowing through the duct 2 and the heated air is delivered by the blower 5 to the interior of the dwelling or other structure being conditioned. The liquefied refrigerant flows from the indoor coil 1 through the conduit 18 and check valve 19 to a liquid receiver 20. Liquid refrigerant from the receiver passes through the conduit 21, expansion valve 22, conduits 23 and 24 to the outdoor coil 11 where it is vaporized bythe absorption of heat from the outdoor air circulated through the duct 14 by the blower 12. The vaporized refrigerant a from the outdoor coil 11 then flows through the suction conduit 25, the five-way valve 15 and the suction or intake line 26 to the compressor 8. The expansion valve 22 is provided with a feeler bulb 23 in heat exchange with the outlet connection of the unit 11 and operates in the usual manner to maintain a predetermined amount of superheat of the refrigerant discharged from the coil 11 when this coil is acting as an evaporator.

During operation of the system on the cooling cycle with the indoor coil 1 functioning as an evaporator, the high pressure refrigerant from the compressor 8 flows through the discharge line 16, valve 15, conduit 31 and conduit 24 to the outdoor coil 11, flow of refrigerant through the conduit 23 being prevented by the fact that the expansion valve 22 is closed. From the outdoor coil 11, the liquefied or condensed refrigerant passes through conduit 33 and check valve 27 to the liquid receiver 20. From the receiver 20 liquid refrigerant flows through the conduit 34 to the expansion valve 35 which controls the flow of refrigerant to the indoor coil 1 through conduits 36 and 18. In the coil 1, the liquid refrigerant is vaporized or evaporated by heat exchange with the room air flowing through the duct 2 and the vaporized refrigerant is returned to the compressor through conduit 17 which now functions as a suction conduit, valve 15 and suction line 26. The degree of superheat of the refrigerantreturning from the indoor coil 1 is controlled by the expansion valve 35 provided with a thermal feeler bulb 37 in contact with the conduit 17 adjacent the outlet from coil 1. During the heating operation, when conduit 17 carries high pressure hot refrigerant from the compressor to the indoor coil 1 the bulb 37 sensing the relatively high temperatures then existing in the conduit 17 completely closes the expansion valve 35 to prevent fiow of the hot refrigerant through the conduits 36 and 34.

From the foregoing it will be apparent that the flow of refrigerant through the system is controlled by the single valve 15. The manner in which this valve operates will be more readily apparent by reference to the sectional View thereof in Fig. 2 of the drawing in which the valve is shown in its operating position for directing the flow of refrigerant through the system during the cooling cycle with the outdoor coil 11 functioning as a condenser and the indoor coil 1 an evaporator.

Referring now to Fig. 2 of the drawing, the valve 15 comprises a casing 41 having therein a plurality of valve chambers including a high or discharge pressure valve chamber 42 and a low or suction pressure valve cham ber 43. Compressed refrigerant is supplied to the valve chamber 42 through the inlet 44 communicating with the compressor discharge line 16 while the outlet 45 of the low pressure valve chamber 43 is connected to the compressor suction line 26.

' The high'pressure valve chamber 42 through which the compressed refrigerant flows to the refrigeration system includes two opposed ports 46 and 47 providing respectively communication between the valve chamber 42 and the adjacent system valve chambers 48 and 49. The low pressure valve chamber 43 is also provided with two opposed ports 50 and 51 which respectively communicate with the valve chamber 49 and a third system valve chamber 52. The middle chamber 49 and the end valve chambers 48 and 52 on opposite sides of the compressor chambers from the middle valve chamber 49 are each provided with an external fiuid flow connection connecting the chamber to the refrigerating system including the two heat exchangers or coils 1 and i1 and are therefore referred to as system valve chambers as distinguished from the compressor-connected valve chambers 42 and 43. The valve chamber 48 has an outlet 53 communicating with the conduit 31 leading to outdoor coil 11 while the valve chamber 52 has an outlet 54 communicating with the conduit 25 leading also to the outdoor coil 11. The middle system valve ch ber 49 differs from the end chambers 48 and 52 in that it communicates through the ports 47 and 59 with both the high pressure compression valve chamber 42 and the low pressure chamber 43. Its external flow connection 55 is connected to conduit 17 leading to the indoor coil 1, which conduit carries compressed refrigerant during one cycle of operation of the apparatus and suction gas during the other.

The direction of flow of refrigerant through the valve 15 and hence through the system is controlled by the positions of the valve member or disc 56 within the high pressure chamber 42 and the valve member or disc 57 within the low pressure valve chamber 53. These valve members are interconnected by a shaft 58 which forms part of a valve actuating means adapted to actuate the valve members to a first position in which ports 47 and 51 are closed and ports 46 and 50 open or a second position in which the ports 46 and 50 are closed and ports 47 and 51 open. Each of the ports 46, 47, 5t) and 51 are concentric about a common axis and the shaft 58 extends along this axis to provide a valve structure in which both of the valve members 56 and 57 can be mounted. on and operated by a single actuating shaft.

When the valve mechanism, including the valve member 56 and the valve member 57 are in the right-hand operating position so that the port 47 and the port 51 are closed, the compressor 8 is therefore connected to the refrigerating system for operation of the system on the cooling cycle with the discharge gas from the compressor discharge line 16 passing through chambers 42 and 48 and conduit 31 to the outdoor coil 11. Vaporized refrigerant is returned from coil 1 through the conduit 17 into the system chamber 49 and through the port 50 into the suction valve chamber 43 from which it passes through the suction line 26 to the compressor 8.

Thus with the valve members 56 and 57 in the position shown in Fig. 2 high pressure or compressor discharge pressure conditions exist in valve chambers 42 and 48 while low or suction pressure conditions are present in valve chambers 49 and 43. However, from a consideration of the conduit arrangement in Fig. 1 it will be seen that the conduit 25, coil 11, and conduit 31 connect the system valve chamber 52 directly to the system valve chamber 48 so that the pressures in the system valve chambers 48' and 52 are always the same and may be either high or low depending upon the position of valve chambers 56 and 57. With chambers 48 and 52 at the same pressures, there is a pressure differential across the valve member 56 in the direction of the valve member 57, that is, to the right and also a pressure differential across the valve member 57 in the opposite direction, that is to the left. For the same effective valve areas, these two pressure differentials would exactly balance one another so that unlike the usual threeway valve or valves employed for reversing reversible refrigerating systems the switchover movement of the valvemembers could. be effected with a minimum or theoretically no effort. Preferably, however, in order to provide a holding force to maintain the valve in either of its operating positions the valve member 56 in the high pressure or compressor discharge chamber 42 and its cooperating ports 46 and 47 are made slightly larger than the valve member 57 and its cooperating ports 50 and 51. The larger effective area of the high pressure valve member 56 as compared to the low pressure valve member 57 thereby provides a slight over-all pressure differential in the valve closing direction to hold the valve in its seated position.

The valve shaft 68 can be actuated by any suitable well known means such as by means of a solenoid coil, electric motor or the like. A preferred means for actuating the valve structure includes a pneumatic arrangement including a piston element 61 reciprocally arranged in a cylinder 62 formed by the extending end portion 63 of the casing 41, the piston being connected to and supgrasses porting one end of shaft 58. The other end of shaft 58 is slidably supported in a bearing member 60.

The actuation of the valve mechanism is effected by creating a pressure differential on the opposite sides of the piston 61 which is accomplished by admitting to the cylinder 62 through conduit 64 refrigerant gas at either suction pressure or discharge pressure. As shown in Fig. 1 of the drawing the other end of conduit 64 is in the form of branched lines 65 and 66 respectively connected to the suction line 26 and the compressor discharge line 16. Each of the branched lines 65 and 66 is provided with a solenoid operated valve 67 and 68 for controlling the admission of refrigerant gas at either suction pressure or discharge pressure to the cylinder 62 and the valves 67 and 68 are in turn operated by an electrical control system including a room thermostat 70 which also controls the operation of the remaining electrical elements of the refrigerating machine.

The room thermostat 70 comprises a bimetallic element 71 for selectively actuating heating and cooling switches 72 and 73 respectively. Upon a call for cooling, the bimetal strip 71 of the room thermostat 70 moves to the left to engage the contact 73 and connect the coil 74a of switch 74 across the secondary of a transformer 75, the primary of the transformer being connected to supply lines 76. The actuation of the switch 74 energizes the coil of solenoid valve 68 through the upper contacts of switch 74 While the lower arm of the switch 74 connects the coil 77 of the switch 78 across the supply line 76 and thereby connects the motors 6, 9 and 13 across the supply line 76.

On a call for heating by the room thermostat 70 the bimetallic strip 71 moves to the right away from the contact 73 and into engagement with the contact 72 which connects the coil 79a of switch 79 across the secondary of the transformer 75. The upper arm of the switch 79 connects the coil of the solenoid valve 67 across the supply line 76 while the lower arm of the switch 79 connects the coil 77 of switch 78 across the supply line 76 to energize the motors 6, 9 and 13 and start operation of the system.

It is thus apparent that upon a call for operation of the system on the cooling cycle the solenoid valve 68 is opened and the valve 67 is closed. On the other hand upon a call for heating the valve 67 is opened and the valve 68 is closed.

The admission of either suction gas or discharge gas to the cylinder 62 in combination with the pressure conditions exisiting Within the valve elfects actuation of the valve members.

Considering first the system as it has been operating on the cooling cycle with the valve members 56 and 57 in the position shown in Fig. 2, it will be apparent that the solenoid valve 68 controlled by the room thermostat 70 has been opened so that discharge pressure from the compressor discharge line 16 has been continuously introduced through the small conduit 64 into the cylinder 62. This pressure Within the cylinder 62 merely'serves to balance out the opposing pressure on the other side of the piston 61 after the valve actuating mechanism has once been moved to the port closing position. If the room thermostat 70 now calls for operation on the heating cycle the solenoid valve 68 would be closed and the valve 67 opened so that refrigerant gas at suction pressure would be introduced into the cylinder 62 or in other words the cylinder 62 would exhaust to suction pressure in line 26. Under these conditions With suction pressure conditions existing within the cylinder 62 and the discharge pressures existing within the valve chamber 48 on the other side of the piston 61 there would be a net pressure differential which results in the movement of the piston 61 and the shaft 58 connected thereto to the left first to open the valve ports 47 and 51 and thereafter to close the opposed valve ports 46 and 50. During the period when the valve mechanism is moving from the one position to the other these valve members so that the valve will function tounload the system.

After switchover the flow of compressed refrigerant is from the discharge line 16 and through the valve chamber 49 and the conduit 17 to the indoor coil 1 while the returning refrigerant vapor from the outdoor coil 11 enters the valve through the conduit 25 connected to the system valve chamber 52. As the conduits 25 and 31 are interconnected in the system, chambers 48, 43 and 52 are at suction pressures and the remaining valve chambers at discharge pressures so that with the valve members 56 and 57 in their heating position closing the lefthand ports 46 and 50 there is a net positive holding force to the left due to the difference in effective valve areas of the valve discs 56 and 57 which tends to hold the valve mechanism closed in the heating position. It will also be noted that in this position the pressures on the opposite sides of the valve actuating piston 61 are again balanced, that is, the pressures within the cylinder 62 and on the opposite side of the piston 61 are both low or suction pressures.

Since the valve members 56 and 57 are fixedly mounted on the valve shaft 58 it is desirable that some means be provided to assure that these members will both seat properly on their cooperating ports. To assure this result, the low pressure ports 50 and 51 include seats and. 101 of Telflon or other flexible, slippery material which are slidably arranged within the casing 41. The rear edges of each of both of these valve seats are tapered as indicated by the numeral 102 and there is also provided for each seat a backing ring 104 and 105 each having a cooperating tapered section 103 adapted to slidably engage the tapered section 102 on the valve seat. Each of the valve seats are biased in a direction towards the valve member 57 by springs 106 and 107 bearing against the backing rings 104 and 105. Forward movement of these seats is limited by contact thereof with the cylindrical stop 109 positioned centrally in the valve chamber 43.

,By thus providing for limited axial movement of the low pressure valve seats the proper seating of both of the valve members 56 and 57 is assured. For example, the positive pressure is exerted by the valve seat member 57 on the valve seat 101 to move this seat against the biasing action of spring 107 until the valve member 56 is properly seated on the port 47. Thereafter the high fluid pressure in the sealed-off chamber causes the tapered edge 102 of the valve seat to expand and more tightly engage the walls of the casing 41 thereby providing a more fluid-tight seal.

From the foregoing, it is believed apparent that a simple and effective valve has been provided for reversing the flow of refrigerant in a reversible refrigerating machine in which the valve operating member is pressure balanced so that the actuation thereof does not require an overcoming of the pressure differences prevailing between the high and low pressure sides of the system. The valve of the present invention also requires relatively few parts, eliminates the need for any separate unloading device, and its operation in connecting the compressor to the refrigcrating system for fiow or refrigerant in either direction is positively assured. It will be understood of course that the valve structure is not limited to a particular refrigerating system and may be used for example with any suitable system containing for example a capillary tube or equivalent fixed expansion device in place of the expansion valves specifically described herein.

Although the invention has been described in connection with specific forms of changeover valve mechanisms other arrangements will occur to those skilled in the art. It is, therefore, understood that the invention is not limited to the particular construction illustrated and described, and it is intended by the appended claims to cover all modifications within the spirit and scope of the invention.

7 What I claim as new and desire to secure by Letters Patent of the United States is:

1. A reversing valve for controlling the flow of refrigerant from a compressor through a refrigerating system including two heat exchange units, said valve comprising an elongated casing having a plurality of chambers therein including a high pressure inlet chamber, a low pressure outlet chamber, a first system chamber between said inlet and outlet chambers, interconnected second and third system chambers adjacent opposite ends of saidcasing, coaxial valve ports connecting adjacent chambers, valve means including a valve member in each of said inlet and outlet chambers mounted on a shaft extending along the axis of said ports for alternatively closing one of said ports in each of said high and low pressure chambers in the direction of fluid flow through said chambers, said ports communicating with said high pressure chamber being larger than those in said low pressure chamber to retain said valve members in either of their port closing positions.

2. A reversing valve for controlling the flow of refrig erant from a compressor through a refrigerating system including two heat exchange units, said valve comprising an elongated casing having a plurality of chambers therein including a high pressure inlet chamber, a low pressure outlet chamber, a first system chamber between said inlet and outlet chambers, second and third system chambers adjacent opposite ends of said casing connected to the same heat exchange unit and operating at the same pressure, coaxial valve ports connecting adjacent chambers, valve means including a valve member in each of said inlet and outlet chambers mounted on a shaft extending along the axis of said ports for alternatively closing one of said ports in each of said high and low pressure chambers, said ports communicating with said high pressure chamber being larger than those in said low pressure chamber.

3. A reversing valve for a reversereycle refrigerating system which includes a compressor for circulating refrigerant through a system including two heat exchangers each adapted to function either as a condenser or as an evaporator, said valve comprising, a casing having a plurality of chambers therein including a high pressure compressor chamber communicating with the compressor discharge line, and low pressure compressor chamber communicating with the compressor suction line, a first system i chamber between said compressor chambers and communicating with one of said heat exchangers and having ports communicatingwith both of said compressor chambers, a second system chamber having an outlet connected with the other of said exchangers and a port communicating with said high pressure compressor chamber, a third system chamber having an inlet connected to said other of said heat exchangers and a port communicating with said low pressure compressor chamber, said ports being concentric with respect to an axis extending therethrough, a valve assembly including a valve member within each of said compressor chambers fixedly mounted on a shaft extending along said axis and arranged to operate in one position to close the port between said high pressure chamber and said first system chamber and the port between said low pressure chamber and the third system chamber and in a second position to close the port between said second chamber and said high pressure chamber and the port between said first system chamber and said low pressure chamber, said second and third system chambers being interconnected through said system whereby the pressure diiierential on one of said valve members tending to hold said valve in a closed position is opposed by a pressure differential on the other of said valve members, said valve member in said high pressure compression chamber having a larger effective area than the valve member in said low pressure chamber to provide a net pressure differential on said assembly sufiicient to retain said assembly in either of said operating positions, and valve opera-ting means including a cylinder at one end of said casing communicating with said second system chamber, a piston connected to said shaft and arranged for movement within said cylinder, with the side thereof facing said second chamber continuously subjected to the refrigerant pressure condition therein and means for admitting refrigerant at the pressure existing in said compressor discharge line to said cylinder on the other side of said piston to move said valve assembly from one op erating position to the other operating position.

i 4. A reversing valve for a reverse cycle refrigerating system which includes a compressor for circulating refrigerant through a system including two heat exchangers each adapted to function either as a condenser or as an evaporator, said valve comprising a casing having a plurality of chambers therein including a high pressure compressor chamber communicating with the compressor discharge line, and low pressure compressor chamber communicating with the compressor suction line, a first system chamber between said compressor chambers and communicating with one of said heat exchangers and having ports communicating with both of said compressor chambers, a second system chamber having an outlet connected with the other of said exchangers and a port communieating with said high pressure compressor chamber, a third system chamber having an inlet connected to said other of said heat exchangers and a port communicating with said low pressure compressor chamber, said ports being concentric with respect to an axis extending therethrough, a valve assembly including a valve member within each of said compressor chambers fixedly mounted on a shaft extending along said axis and arranged to operate in one position to close the port between said high pressure chamber and said first system chamber and the port between said low pressure chamber and the third system chamber and in a second position to close the port between said second chamber and said high pressure chamber and the port between said first system chamber and said low pressure chamber, said second and third system chambers being interconnected through said system whereby the pressure differential on one of said valve members tending to hold said valve in a closed position is opposed by a pressure differential on the other of said valve members, said valve member in said high pressure compression chamber. having a larger effective area than the valve member in said low pressure chamber to provide a net pressure differential on said assembly sufiicient to retain said assembly in either of said operating positions, and valve operating means including a cylinder at one end of said casing communicating with said second system chamber, a piston connected to said shaft and arranged for movement within said cylinder, with the side thereof facing said second chamber continuously subjected to the refrigerant pressure condition therein and means for admitting refrigerant at the pressure existing in said coma pressor discharge lineto said cylinder on the other side of said piston to move said valve assembly from one operating position to the other operating position, the ports in one of said compressor chambers having valve seats arranged for limited axial movement to assure closing of said port by the cooperating valvemember when the other of said valvermembers is in its seated position.

5. A reversing valve for a reverse cycle refrigerating system which includes a compressor for circulating refrigerant through a system including two heat exchangers each adapted to function either as a condenser or as an evaporator, said valve comprising a casing having a plurality of chambers therein including a high pressure compressor chamber communicating with the compressor discharge line, and low pressure compressor chamber communicating with the compressor suction line, a first sys tem chamber between said compressor chambers and communicating with onerof said heat exchangers and having parts communicating with both of said compressor chambers, a second system chamber having an outlet connected with the other of said exchangersrand a port communicating with said high pressure compressor chamber, a third system chamber having an inlet connected to said other of said heat exchangers and a port communicating with said low pressure compressor chamber, said ports being concentric with respect to an axis extending therethrough, a valve assembly including a valve member within each of said compressor chambers fixedly mounted on a shaft extending along said axis and arranged to operate in one position to close the port between said high pressure chamber and said first system chamber and the port be-- tween said low pressure chamber and the third system chamber and in a second position to close the port between said second chamber and said high pressure chamher and the port between said first system chamber and said low pressure chamber, said second and third system chambers being interconnected through said system whereby the pressure differential on one of said valve members tending to hold said valve in a closed position is opposed by a pressure differential on the other of said valve members, said valve member in said high pressure compression chamber having a larger effective area than the valve member in said low pressure chamber to provide a net pressure differential on said assembly sutlicient to retain said assembly in either of said operating positions.

6. A fluid flow control valve including a casing having a plurality of chambers including a high pressure inlet chamber and a low pressure outlet chamber, opposed valve ports in each of said chambers, all of said ports being concentric with respect to common axis therethrough, a shaft extending along said axis, a valve member in each of said chambers for alternatively and simultaneously closing one of the ports communicating therewith, said valve members being mounted on said shaft, the ports in one of said chambers including sliding valve seats and resilient means biasing each of said seats toward the valve member cooperating therewith to effect positive seating of said valve member upon seating of said valve member in the other of said chambers.

7. A fluid flow control valve including a casing having a plurality of chambers including a high pressure inlet chamber and a low pressure outlet chamber, opposed valve ports in each of said chambers, all of said ports being concentric with respect to common axis therethrough, a shaft extending along said axis, a valve member in each of said chambers for alternatively and simultaneously closing one of the ports communicating therewith, said valve members being mounted on said shaft, the ports in said low pressure chamber including sliding valve seats and resilient means biasing each of said seats toward the valve member cooperating therewith to effect positive seating of said valve member upon seating of 10 said valve member in the said high pressure chambers.

8. A fluid flow control valve for delivering high pressure fluid from a compressor source to either of two outlet connections and returning low pressure fluid from either of two inlet connections to said source, said valve comprising a casing having therein a high pressure valve chamber including an inlet and opposed ports communicating with said outlet connections and a low pressure valve chamber including an outlet and opposed ports communicating with said inlet connections, all of said ports having a common axis, means including a valve member in each chamber fixedly mounted on a valve shaft extending along said axis for closing alternatively a port in each chamber, the ports in the low pressure chamber including slidable valve seats and means biasing said seats toward the cooperating valve member in said low pressure chamber to provide limited movement thereof when contacted by said cooperating low pressure valve member to assure proper seating of both valve members upon actuation of said valve.

9. A fluid flow control valve for delivering high pressure fluid from a compressor source to either of two outlet connections and returning low pressure fluid from either of two inlet connections to said source, said valve comprising a casing having therein a high pressure valve chamber including an inlet and opposed ports communicating with said outlet connections and a low pressure valve chamber including an outlet and opposed ports communicating with said inlet connections, all of said ports having a common axis, means including a valve member in each chamber fixedly mounted on a valve shaft extending along said axis for closing alternatively a port in each chamber, the ports in the low pressure chamber including slidable valve seats and means biasing said seats toward the valve member in said low pressure chamber to provide limited movement thereof when contacted by said operating low pressure valve member.

References Cited in the file of this patent UNITED STATES PATENTS 1,679,614 Lichtenberg Aug. 7, 1928 2,062,126 Gibson Nov. 24, 1934 2,432,721 Brown Dec. 16, 1947 2,503,639 Snyder Apr. 11, 1950 2,624,585 Churchill I an. 6, 1953 2,640,494 Kounovsky June 2, 1953 2,690,649 Borgerd Oct. 5, 1954 FOREIGN PATENTS 547,692 Great Britain 1942

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