GB1306048A - - Google Patents

Abstract

1306048 Fluid-pressure senvomotor systems; automatic control of pressure or temperature WESTINGHOUSE ELECTRIC CORP 19 April 1971 [15 April 1970] 24944/71 Heading G3P G3R [Also in Division F4] The temperature or pressure of a refrigerant is maintained at a pre-set value by adjusting the ca- pacity of a centrifugal compressor 11 with a piston 43 controlled by a pair of solenoid operated valves VA, VB respectively responsive to positive and negative deviations from the preset value, the signals for energizing the valves changing from intermittent to continuous as the deviation increases. In the preferred embodiment, a temperature sensing element 27 adjacent the water outlet 26 of an evaporator 17 operates a bellows 70 and a pivoted platform 73 carrying a pair of contacts 79, 80 co-operating with fixed contacts 77, 78 to energize one of the two valves VA, VB. A heating coil, such as 83, surrounding a bimetallic strip, such as 81, forms part of each solenoid circuit to provide an intermittent energizing signal until the deviation from the preset value is sufficient to maintain the fixed and movable contacts in engagement. Each solenoid valve is arranged to connect a space at one side of the piston 43 with either a supply conduit 52 or a drain conduit 60 while the piston 43 is arranged to rotate spin vanes 41 in the inlet 19 of the compressor. The solenoid valves may be controlled manually and energization of an overload relay OR in the circuit of a motor 10 for driving the compressor energizes the solenoid valve for moving the piston 43 to minimum capacity position.