GB793688A - Improved refrigeration apparatus - Google Patents

Abstract

793,688. Refrigerating. GENERAL MOTORS CORPORATION. Jan. 2, 1957 [Jan. 6, 1956], No. 175/57. Addition to 716,651. Class 29 A compression refrigeration system including evaporators 28, 34 for cooling freezer and storage compartments respectively, in which the compressor 18 is switched on or off in response to the temperature of the evaporator 34. has a defrost' device adapted to supply warm refrigerant vapour to the evaporator 28 thus defrosting the latter at less frequent intervals than the evaporator 34. The system also includes a superheat removing coil 22, condenser 24, fixed restrictor tube 26 and accumulators 30, 36. A by-pass pipe 68, in which is a solenoid valve 66, extends from the entry of the condenser to the entry of the evaporator 28. The compressor is switched on and off by a thermostat 42 having a bulb 40 in contact with the evaporator 34. A cam 74 is rotated by a motor 50 operating When the compressor is switched on and has two cam surfaces 58 and 62. The cam follower 56 is attached to the contact 70 and on riding over surface 58 closes the contacts 70 and 60. This takes the thermostat 42 out of circuit and allows an uninterrupted period of operation for the compressor during which the pressure of the warm refrigerant vapour is built up. On riding over surface 62 the cam follower closes the contacts 70, 60 and 64, opening valve 66 and permitting warm vapour to flow to evaporators 28 and 34 through line 68. The sudden drop in condenser pressure causes refrigerant to boil and vapour Hows from the condenser to the evaporator. The length of defrosting is determined so that condensed vapour in evaporator 28 is re-evaporated during defrosting.