Patent GB-781538-A (GB)
Title: Combined unloading and reversing valve for reversible refrigerating system
IPC: F25B41/04
Filed: 1955-10-05
Abstract: 781,538. Refrigerating; heat pumps. GENERAL ELECTRIC CO. Oct. 5, 1955 [Oct. 6, 1954], No. 28410/55. Class 29 [Also in Group XXIX] In a combination unloading and reversing valve for a reversible refrigerating system comprising a casing 40, Fig. 2, having therein a high-pressure valve chamber 42 including an inlet 16 and opposed outlet ports 49, 50 for controlling the flow of refrigerant in either of two paths to the system, a low-pressure valve-chamber 43 including an outlet 26 and a pair of opposed inlet ports 71, 72 for receiving refrigerant from the system, and spaced valve closures 58, 59 and 97, 98 for alternatively closing the ports in each of the chambers, the closures 58-59 are sleeve valves slidably mounted on a shaft 61 for movement therealong beyond a port closing position temporarily to interconnect the high and low pressure paths of the system during reversing operation of the valve. System Arrangement: An indoor heat-exchange coil 1, Fig. 1, which operates either as a condenser or evaporator to heat or cool air admitted to a duct 2 from a fresh-air inlet 3 and a room-return inlet 4, has the air circulated thereover by a blower 5 driven by an electric motor 6, before being discharged into the room via a duct 7. Refrigerant is circulated through the coil by a compressor 8 driven by an electric motor 9. A second coil 11 is provided over which outdoor air is circulated by a blower 12 driven by an electric motor 13, the blower 12 drawing air through a duct 14 and discharging it to an exhaust connection, not shown. A five-way valve 15 controls the flow of refrigerant to the coils 1 and 11. System Operation: (a) Heating Hot-compressed refrigerant is delivered from the compressor 8 through the highpressure discharge conduit 16 to the valve 15 from whence it flows into a conduit 17 to the coil 1 to heat the air entering the duct 7, the condensed refrigerant then traverses a conduit 18 and a check valve 19 before entering a receiver 20 from which It passes through a conduit 21, expansion Valve 22, and conduits 23, 24 to the coil 11 to absorb heat from the air in the duct 14. The vaporized refrigerant then flows into the compressor intake conduit 26 by way of a conduit 25 and the valve 15. An expansion valve 22 is provided having a feeler bulb 28 in heat exchange relationship with the outlet of the coil 11 to maintain a given degree of superheating of the refrigerant when coil 11 is acting as an evaporator. (b) Cooling The high-pressure refrigerant from the compressor 8 flows through the discharge conduit 16, valve 15, conduit 31 and 24 to the coil 11, the expansion valve 22 being closed, wherein it is condensed before passing through a conduit 33 and receiver 20 into a conduit 34 and then to another expansion valve 35 which controls the refrigerant flow through conduits 36 and 18 and into the coil 1 where the refrigerant is 'vaporized by the air flowing in the duct 2. The refrigerant returns to the compressor via conduit 17, valve 15 and conduit 26. The degree of superheating of the refrigerant from the coil 1 is controlled by the expansion valve 35 which embodies a feeler bulb 37 in contact with the conduit 17. Valve construction: In addition to the high and low pressure chambers 42-43. Fig. 2, the casing 40 also provides valve chambers 45, 46 and 47; these five chambers are open to conduits 16, 26, 17, 31 and 25, respectively. Communication between chamber 42 and adjacent chambers 45 and 46 is effected through the opposed co-axial ports 49 and 50 each of which is made up of a packing ring 51 and a retainer ring 52 with an interposed sealing ring 53, the central apertures in each ring being coaxial and co-extensive and together forming the ports 49 and 50. A spring 54 bears at each end against the rings 52 to compress the seals 53 and keep them in contact with the casing 40; each of the rings 51 are secured by snap rings 55. The inner periphery of the seals 53 engage closure discs 58 and 59 which, respectively, slide into and close the ports 49 and 50; only one port is closed at any one time. The discs 58 and 59 which are slidably mounted on the common shaft 61 are spaced apart a distance greater than that separating the ports 49 and 50 and are held in this position by a spring 64 and stops 62, 63. The other pair of opposed ports 71 and 72 provide communication between the low pressure chamber 43 and adjacent chambers 45 and 47 whilst the closure disc 97 between supporting discs 73 and 99 and fixed to the shaft 61 is arranged to close port 71 and the second closure disc 98 between similar discs 74 and 100 is adapted to close port 72; these closure discs are spaced apart the same distance as discs 58 and 59 so that only one port is closed at any one time. The closure discs 97 and 98 co-operate with seats 75 and 76 respectively, surrounding the corresponding ports 71 and 72 each of which latter incorporate an extension 77 and 78 in which the supporting discs 73 and 74 are a loose fit. The shaft 61 embodies a piston 80 comprising a plate 90 and spring discs 91 on each side thereof having sealing rings of such material as "TEFLON"; the piston, which forms an end wall of chamber 47, slides in a cylinder 81 under the action of a pressure differential cause by admitting into the latter refrigerant at either suction or discharge pressure depending upon the pressure in chamber 47. Valve Actuating Apparatus: The cylinder 81 is connected by a conduit 84 to both conduits 16 and 2'6, Fig. 1, by branches 85 and 86 each provided with a solenoid operated valve 87 and 88, respectively, which valves are operated by an electrical system including a room thermostat 90 which also controls the electric motors 6, 9 and 13. Valve operation: With the valve in the leftward position shown in Fig. 2 the system is set for a cooling cycle and high-pressure refrigerant is present in chambers 42, 46 and 47, since the pressures in chambers 46 and 47 are always equal, and low-pressure refrigerant is present in chambers 43 and 45 so that opposite pressure differentials exist across closure discs 59 and 98 but since discs 97-98 are of larger effective area than discs 58 and 59 there is a small resultant force tending to hold the valve mechanism in the position shown; during this time high pressure refrigerant has been acting on both sides of the piston 80. Upon a demand arising for a heating cycle the thermostat 90, Fig. 1, causes deenergization of valve 88 and energization of valve 87 so that the suction duct 26 is connected to the cylinder 81 and, since the piston has a larger effective area than that between the closure discs, the piston and shaft move rightwardly until the disc 74, Fig. 2, begins to move out of its extension 78 whereupon (1) disc 73 begins to move into extension 77 so that conduit 26 is substantially cut off from the conduit 17, and (2) disc 74 has moved off its seat and permits leakage betwen itself and the extension 78 so equalizing the pressure across this disc. The admission of high-pressure refrigerant from the conduit 25 and chamber 47 to the conduit 26 causes an equalization of pressure across the piston 80 due to flow of refrigerant through the conduit 26, valve 87 and conduit 84 into the cylinder 81 whereupon the piston 80 can no longr move the shaft 61. At this point the disc 59 has moved away from the port 50 whilst the disc 58 has isolated chambers 42 and 46, a pressure differential is in consequence created which acts on the left of the disc 58 and moves the latter against the spring 64 into the chamber 42; a sleeve 93 limits this travel. The compressor connected to the conduit 16 and the portion of the system including the coil 11 and conduit 31 now supply high-pressure refrigerant through the port 50 to the conduit 17 and coil 1 until the pressures in both coils 1 and 11 are equalized to enable the disc 58 to be returned by the spring 64 to the operating position against the stop 62 and within port 49. The resulting pressure build up of the side of the system including coil 1 results in a pressure difference acting on the difference in areas of the discs 73 and 58 so that the'shaft 61 is urged rightwardly to complete its stroke i.e. when disc 97 engages seat 75. A similar but reverse sequence of events will take place upon a demand arising for a reversal of the system to the cooling operation. The arrangement also enables the valve to be shifted to either of its operating positions when starting up the system from a pressure equalized condition regardless of the position of the valve shaft when the compressor is started.