GB1395083A - Combination type refrigerator - Google Patents

Abstract

1395083 Control circuits for defrosting refrigerators NANIWA SANGYO KABUSHIKIGAISHA 22 July 1972 34381/72 Heading H2H [Also in Division F4] A refrigerator having a main compartment 8 and a deep-freeze compartment 7, includes a compressor 1, a condenser 3, an expansion valve 4, a deep-freeze evaporator 9, a main compartment evaporator 10 and a defrosting bypass line 12. In normal operation, refrigerant passes to the evaporator 9 via the condenser 3, and then to the evaporator 10 via an electromagnetic valve 11. A thermo-couple or thermistor is provided for controlling the temperature of the main compartment 8 by controlling the power supply to the compressor. The deepfreeze compartment is provided with a frost sensor 52 and a temperature sensor A. The frost sensor is actuated by vibrations from the refrigeration system and includes a gap 50 which becomes blocked with ice; causing an electric output to appear between the terminals 47E and 48E. The temperature sensor A includes a cylinder filled with water; the resistance between terminals 23 and 24 being small while the water remains liquid, but large when it becomes ice. Connected across the terminals 23, 24, 47E and 48E is a defrosting control circuit 54 which comprises transformers 55, 56 and 57, transistors 58 and 59, normally closed micro-relay 61, normally open micro-relay 60 and the contacts 67 and 68 of the defrosting operation switch. A series connected circuit comprising microrelay 60, microrelay 61 and the coil of a relay 66 having a self-holding circuit comprising contacts 64, 65 is connected across source terminals 62, 63. In normal operation, the defrosting operation switch contacts 67 and 68 are open. Upon cooling, frost eventually forms in the gap 50 causing current to flow between the terminals 47 and 48. As a result the switch contacts 67 and 68 are closed, and hot refrigerant passes via the bypass line 12 to the evaporator 9. During defrosting it is essential for the compressor to operate continuously. However, when the compartment 8 has been cooled down to a predetermined temperature, the controlling thermo-couple cuts off the power to the compressor. A resistance heater 16 is therefore provided within the compartment 8 and is connected to the contacts 67, 68 such that during the defrosting operation, the heater 16 counteracts the evaporator 10, thus preventing the said predetermined temperature from being reached.