GB639691A - Improvements in and relating to refrigerating systems - Google Patents

Abstract

639,691. Refrigerating. BRITISH THOMSON-HOUSTON CO., Ltd. Jan. 5, 1948. No. 321. Convention date, Jan. 4, 1947. '[Class 29] [Also in Group XXIX] In compression systems having two evaporators 1, 2 operating at different temperatures, a pressure-operated valve 7 is provided for selectively connecting one or other of the evaporators to the suction line 6, in response to the difference of pressure in the evaporators, the actuation being modified by an auxiliary pressure-actuated valve 36 after a pre-determined pressure has been attained in one of the evaporators. The high temperature evaporator 2 is supplied with liquid refrigerant from the condenser 4 through a capillary tube 5 and has a suction header 10 from which liquid refrigerant is supplied through a further capillary tube 11 to the low temperature evaporator 1 having a suction header 12. Suction pipes 9, 8 from the headers 10, 12 are connected to the valve casing 7 from which the pipe 6 leads to the suction side of the compressor 3. A piston valve 26 in a valve chamber 20 is subjected on its opposite sides to the pressures in the two evaporators through passages 23, 24 in the casing 7, and is connected by a shaft 30 with a second piston 29 with a groove 41 and rubber buffers 31 which cushion its impact and provide a space between it and the end of the chamber 20. A spring 33 normally forces the piston 26 towards the left, placing the low temperature evaporator suction pipe 8 in connection with the suction line 6. The pressure in the high temperature evaporator also acts upon a bellows 37 having a lost motion connection 42, 43, 44 with a valve 36 in a bye-pass passage 40 equalizing the pressure on both sides of the piston. On starting, valve 36 will be closed due to the high pressure in the high temperature evaporator, and the piston will be in the left-hand position due. to the spring 33. As the temperature and pressure in the low temperature evaporator 1 fall the piston moves to the right, putting the high temperature evaporator 2 into connection with the suction pipe. When the high temperature evaporator reaches a predetermined low pressure the bellows 37 opens the valve 36 by contacting the shoulder 43, thus equalizing the pressure on opposite sides of the piston, which is then forced to the left by the spring 33 to put the low temperature evaporator into connection with the suction pipe. Reduced portions on the piston allow of both evaporators being placed under suction and reduce shock. During normal working one or other of the evaporators is connected to suction in accordance with the demand, and if both require refrigeration preference is given to the high temperature evaporator. The motor is controlled by a thermostat 13 through a bellows 15 and switch 18.