Patent GB-796626-A (GB)
Title: Improved refrigerator
IPC: F25D17/04
Filed: 1956-07-10
Abstract: 796,626. Refrigerating. GENERAL MOTORS CORPORATION. July 10, 1956 [Aug. 9, 1955; Aug. 9, 1955], No. 21339/56. Class 29 In a refrigerator having freezer and food Storage compartments cooled by a forced air circulation flowing over the evaporator of a compression system, a defrosting control system so operates during defrosting that the compresser is stopped and the air circulation is ineffective for cooling the freezer compartment. As shown in Fig. 1, fans 30 draw air down a shaft 35 in which evaporator 22 is located and which is located at the rear of the food storage compartment 21 behind a wall 36. The fans force the cold air up a shaft 31 behind shaft 35 whence it flows around the freezer compartment 20 and enters the latter through apertures. The air leaves compartment 20 through holes 34 and returns to the top of shaft 35 through passage 34b. Compartment 21 is cooled by heat conduction through wall 36 and by air-flow over part of evaparator 22 when a damper 45 is opened by a thermo-responsive element 47. The arrangement is such that moisture never freezes in compartment 21 and any frost formed in or on compartment 20 sublimes and is deposited on evaporator 22, The compressor 23 is controlled by a thermo-responsive element 61, Fig. 9, on the evaporator 22. Defrosting is effected by an electric heater 40 around the lower end of the evaporator. Defrost water from the bottom of shaft 35 and condensate from compartment 21 are led into a tray 87 in the machinery compartment for evaporation. The defrost control, Figs. 9 and 11, includes a three-contact switch actuated by a cam 51 driven by a timer 50, the middle contact 56 being connected to the power supply, the upper contact 75 to the heater 40, and the lower contact 76 to the compressor motor 23 and the motors 60 of fans 30, Fig. 11 shows the refrigerating condition in which contacts 56, 76 are made to energize the compresser and fan motors, cam follower 54 riding on the high part 52 of cam 51. When the follower enters the low part 53 of the cam, contact 56 moves up clear of contact 76 to meet contact 75, which is held down by a catch 72, so that heater 40 is energized. When defrosting ends, the evaporator temperature rises and this is detected by a thermoresponsive element 70 which removes catch 72 from contact 75. The parts then move to the position of Fig. 9 in which the heater is de-energized and the compresser and fans are operative even though the follower may still be on the defrosting part of the cam. As shown in Fig. 12, fan 30 circulates air over evaporator 22 and in parallel through compartments 20, 21, the flow into the latter being controlled by damper 45 actuated in dependence on the temperature of the compartment. For defrosting, the compresser motor is shut off and a damper 45A is closed to prevent circulation of air through the freezer compartment. The fan circulates air above freezing temperatures from the compartment 21 over the evaporator which is thus defrosted. The defrost melt flows to a tray 87 where it is evaporated by a hot-gas conduit 23A from the compressor. Each compartment contains thermal elements 61, 61A connected in parallel and in series with the compressor motor which is thus cut out if neither compartment needs refrigeration. Alternatively or in addition, the compressor can be cut out by a switch responsive to suction pressure. As shown in Fig. 16, fans 112, 113 circulate air over evaporator sections 22A, 22B and through compartments 20, 21, entry of air into the latter being controlled by a damper 120 actuated in dependence on the temperature of the compartment. For defrosting, the compressor motor is cut out and dampers 125, 126 are actuated so that air from compartment 21 flows over the evaporator sections to defrost them and returns to the compartment. The embodiments of Figs. 12 and 16 may be defrosted after the manner of the embodiment of Fig. 1 by stopping the fan during defrosting and providing an electric heater adjacent the evaporator, dampers 45A or 125 and 126 being omitted. The air-cooling unit may be mounted directly above or below the cooling compartments or may be connected thereto by conduits 177, in which case one cooling unit may supply several pairs of compartments in parallel. The apparatus may form part of unit kitchen cabinet structures. The compartments may have top and bottom air entry and exit ports, the inoperative ones being closed by insulating plugs 178. One or more compartments may have a light energized by opening the access door or doors.