Patent GB-489126-A (GB)
Title: Improvements in or relating to temperature control of evaporators or the like of refrigerating apparatus
IPC: F25B47/02
Filed: 1937-04-12
Abstract: 489,126. Refrigerating ; heating systems. ELECTROLUX, Ltd. April 12, 1937, No. 10375. Convention date, April 16, 1936. [Classes 29 and 64 (ii)] The temperature of the evaporator 10, Fig. 1, of an absorption refrigerating system is modified to maintain a desired temperature in a refrigerating cabinet or to effect defrosting by supplying heat thereto by a controllable closed condensing-evaporating heat transfer system 13, 12, 11, receiving heat from the generator 15 of the refrigerating system. The heat transfer system includes a device by which variable amounts of medium (butane for example) may be retained out of circulation to control the heating effect. This device comprises a pair of bellows 17, 21 connected together by a piston 24 and rod 25 and to a fixed ring 16 traversed by the conduit 12. The piston rod is extended as a knob 26 adapted to be held by a pair of springs 27. The lower bellows is of larger diameter than the upper so that upon rise of pressure consequent upon rise of temperature in the system after all ice has been melted off the evaporator, the piston 24 moves downwards and allows condensate to accumulate in the lower bellows and stop the heat transfer. A defrosting action may be initiated by lifting the knob 26 past the springs 27 by a wire 28 on a pulley 29 rotated from a setting member 33. The condenser element 11 may be cast in the wall of the evaporator or of a cooling body thereon, which may have ribs 34 to increase the conductivity through the ice layer. In adapting the bellows reservoir 21 for thermostatic control, a further bellows 42, Fig. 2, connected by conduit 44 with a sensitive element 45 in the cabinet, is connected by an open frame member 46 with the lower wall of the bellows 21, which is urged upwards by a spring 41. Undue drop in temperature in the cabinet causes the displacement of heat transfer medium out of bellows 21 and into circulation.. The grip of the spring arms 27 may be adjusted by a thermostat. In another arrangement, Fig. 4, the position of the bellows piston 24 is dependent on the position of a feeler arm 51 contacting the ice layer 50 on the evaporator. The arm extends from a stepped sector 52, 53 pivoted eccentrically at 56 on a disc 55 pivoted at 61 in the lower arm of a fixed frame 57, 58. The piston 24 has a part 54 adapted to rest on the edge of the sector and a depending arm 65 carrying a spring pin 64 adapted to engage a notch in the disc 55. A spring 59 urges the feeler into contact with the ice and a coil spring on pivot 61 urges the disc 55 to rotate clockwise. In the position shown defrosting is proceeding, and when it is completed the edge 53 is pulled to the left to allow part 54 to drop on to edge 52. This establishes the reservoir in bellows 21 and at the same time the pin 64 is lowered out of notch 63, whereupon the disc 55 is rotated to bring the sector to a position in which the feeler arm cannot be frozen in. The spring 59 is released from tension in this position. The parts are brought into position for another defrosting operation by manual or other rotation of the disc 55 in a counterclockwise direction.