GB1012788A - Control switch for cycling and defrosting refrigerating apparatus - Google Patents

Abstract

1,012,788. Thermal switches. RANCO Inc. May 19, 1964, No. 20685/64. Heading H2B. A refrigerator control switch, basically similar to that disclosed in Specification 942,106, has additional snap-action means 106, 108 and contacts 55, 61 (Fig. 7) for defrosting, which contacts are closed by manual operation of a button P at the centre of the normal control knob K and opened by the thermally responsive element 86 at a temperature appreciably above the normal cycling temperatures of the main contacts 67, 72 due to the said snap-action means also imposing additional spring-loading on the thermal element when defrosting is initiated. The toggle 106 (pivoted at 107) and overcentre spring 108 are normally in the position shown in Fig. 7, and an extension 116a of the toggle 106 holds contact 61 away from contact 55. When button P and thus rod 105 are depressed the end 105a snaps the toggle 106 and spring 108 into the position shown in Fig. 14, allowing contacts 55, 61 to close (Fig. 11, hot shown), and a tab 106f is urged against a tab 83d on the end of main lever 83 (pivoted at 84) thereby adding to the force exerted by spring 90 against capsule 86 via the nose 83b. Therefore a relatively high temperature is necessary before capsule 86 moves lever 83 clockwise to snap main contacts 67, 72 into engagement and to restore the snap mechanism 106, 108 by tab 83d acting on tab 106f. The final defrost temperature is adjustable by means of screw 109, and is rendered substantially independent of the setting of knob K by means of a compensating spring 120 which extends from the cam follower 94 to the toggle 106 such that increase in tension of main spring 90 is offset under defrost conditions by spring 120 reducing the additional force exerted on tab 83d by spring 108. The contacts 55, 61 may be used to-energize a heater in the evaporator of the refrigerator (Fig. 13, not shown), but if it is desired to defrost by diverting hot compressed refrigerator gases to the evaporator a solenoid valve is used and it is necessary for the compressor to run during defrost. To this end a nose 106e (Fig. 7) is provided on toggle 106 to engage a projection 118 on member 82 and depress the latter away from lever 83, thereby maintaining contacts 67, 72 closed (Fig. 10, not shown) while defrosting.