GB831527A - Improvements in and relating to thermostatically controlled electric switches - Google Patents

Abstract

831,527. Thermal switches. DIAMOND H SWITCHES Ltd. March 11, 1957 [March 23, 1956], No. 9101/56. Class 38 (5). In a thermal switch in which the motion of the expansible element is transmitted to the switch by a lever assembly including a prestressed part which is adapted to yield when the load thereon exceeds a predetermined value so that relatively large movements of the element will not unduly stress the operative parts of the switch, the lever assembly is carried by a housing and the switch is arranged as a separate assembly which can be readily removed as a unit from the housing. Fig. 6 shows diagrammatically the arrangement of a thermostat having as the expansible element a liquid-filled bellows 43, 44 which is also separately removable as a unit. The bellows rod 48 engages an ambient-temperature-compensating bimetal 21 at one end of the two-part pivoted lever 15, 20, the parts being connected by a partially compressed spring 19 and a slidable pin which actuates the snap-action switch arranged in a separate casing 26. The part 15 of the lever is pivoted on a further lever 12, the position of which is altered by the control-rod 2 to adjust the operating temperature. A suitable snapaction switch, Fig. 3, comprises a trifurcated blade-spring 31 having a compression spring 38 of zig-zag form between the outer spring parts and the central compression leaf 37. A subsidiary heater 52 as described in Specification 655,989 may be incorporated in the thermostat.