GB642109A - Improvements in or relating to thermally responsive electric circuit controlling devices - Google Patents

Abstract

642,109. Thermal switches; mechanical switches, retained set. IGRANIC ELECTRIC CO., Ltd. Jan. 10, 1947, No. 887. Convention date, Oct. 31, 1941. [Class 38(v)] The fixed contacts 9 of a thermal switch for a refrigerator are normally engaged by a spring-urged bridging contact 10, opened by bell-crank levers 20 with a snap action when the ends 23 of the levers 20 are engaged by an operating lever 25. In the closed position shown, the lever 25, which is pivoted at 34 to the base, is held against an adjustable stop 39 by springs 27 which are also attached to a control lever 26 pivoted to the base at 35. The thermal element 3 comprises a diaphragm 44 sealed in a fixed cup 45. As the refrigerator evaporator cools, the diaphragm falls until. a spring 6 forces the springs 27 over-centre, by means of a stirrup 57 and the lever 26,. to open the contacts. As the evaporatorwarms up again, the diaphragm 44 rises against the action of the spring 6 until, at a predetermined temperature, the springs 27 and levers 25, 26 snap into the position shown, thereby allowing the contacts 9, 10 to close to restart the refrigerator. The operating temperatures may be adjusted by varying the compression of the spring 6. by rotation of a cam 63 by a control knob 7. The cam bears on a projection 76 of a plate 65 which engages one end of a lever 64 bearing on the upper end of the spring 6.. The rotation of the cam 63 is limited by a projection on the cam and co-operating. stops (not shown). The cam also has a radial lug 92 whereby the lever 26 can be moved into the " open position for defrosting. Adjustment of the screw 39 varies the differential between the opening and closing temperatures.