Patent GB-716651-A (GB)
Title: Improved refrigeration apparatus
IPC: F25B5/04
Filed: 1952-04-21
Abstract: 716,651. Refrigerating; heat insulation. GENERAL MOTORS CORPORATION. April 21, 1952 [April 28, 1951], No. 9957/52. Classes 29 and 64(2) A refrigerator compris-  ing an upper deep freeze compartment separated by an insulating partition from a lower storage compartment, individual doors 42, 46 being provided, cooled by a compression refrigerating system the evaporator of which comprises two sections connected in series, the first cooling the deep-freeze compartment and the second cooling the storage compartment. A control device has a part in direct thermal contact with the second section and pre. vents the start of the compressor before the temperature of the second section has risen above 32‹F and prevents the stopping of the compressor before the temperature of the second section has fallen below 32‹F. The refrigerant is mixed with lubricant so that at high ambient temperatures less will be dissolved in the lubricant and hence more will circulate in the system. Mixed refrigerant from compressor 50 flows through a cooling coil 51 where the lubricant is liquefied, the mixture returning to the compressor casing. The refrigerant vapour flows through condenser 52 and capillary tube 54 to an evaporator coil 58 which cools the top, bottom and left-hand side of the deep-freeze compartment. The refrigerant then flows through a coil 60 on the underside of an ice-making shelf 62 and a coil 68 on the right-hand side of the compartment. Coils 58, 60, 68 constitute the first evaporator section. An additional ice-making shelf 64 is provided. Refrigerant then, flows through an inverted U- pipe 69, which retains liquid refrigerant in the first section, and a pipe 72 to the second section of the evaporator which comprises a vertically disposed plate 90 to which is secured a U-shaped pipe 92 forming the evaporator. The top of the pipe 92 is connected by a pipe 94 to a third evaporator section 96 which is connected by piping 121, 125 to the suction of the compressor and which helps cooling of the deep freeze compartment. The deep-freeze section comprises a continuous metal box 32 sealed to the outer shell 36 of the cabinet by a breaker strip 34 and the box 32 is in thermal contact with the evaporator coils 58, 68 and, through connection 98, with the evaporator section 96. The deep-freeze unit is of substantial thermal mass and can thus be maintained at a low temperature. The evaporator section 90, 92 is of small thermal mass and is cycled between the same low temperature and a temperature a few degrees above the freezing point of water, this being effected by controlling the compressor motor by a switch 80 actuated by a thermal element 370 on the section 90, 92. Thus any moisture will, while the compressor is working, migrate from the cabinet and the insulation to the second section and will be melted therefrom during the idle period of the compressor. When the compressor is idle,' the rise in temperature of the second section 90, 92 forces any liquid refrigerant therein up pipe 72 into the first section, pipe 69 preventing return flow. The cabinet insulation is provided by bags 147, 153 of polyethylene or polyvinylidene chloridecompletely sealed and stuffed with glass or other mineral wool. The storage compartment is defined by a liner 38 to which plate 90 is fixed by brackets 91. It contains at the bottom twocovered pans 127,-129 which are cooled by a secondary system, the condenser 137 of which is behind liner 38 adjacent to plate 90 and the evaporator 131 of which is on the back of liner 38 adjacent the pans. The inner surface of the outer shell 36 is sealed with asphalt. Condensate from the shell 32 can pass through an opening 162 and, together with moisture from the outer surface of the shell, collects in a tray 141 discharging through an opening 143 and spout 145 down a side wall of liner 38. Condensate from spout 145 and from plate 90 passes from the, cabinet to a pan 159 in the machinery compartment through an opening 157. In modifications (Figs. 18 and 19, not shown), the inverted U-pipe 69 may include a refrigerant trap in the form of a tank and the third evaporator section may also be located on plate 90. In further modifications (Figs. 20-22, not shown) the condenser of the secondary system is cooled by the first or third sections of the evaporator and, in the latter case, the third section may be located in the rear insulation of the storage compartment. The procedure for setting up the controls and for charging the system to ensure correct operation is described.