GB1492592A - Electrical switches - Google Patents

Abstract

1492592 Thermal switches; fluid pressure switches UNITED GAS INDUSTRIES 5 March 1975 [13 March 1974 20 March 1974] 11084/74 and 12251/74 Heading H1N A pressure or temperature operated electrical switch comprises a housing 13 containing an expansible capsule 17 for moving a pivotable operating arm 22 and having at one end a screw threaded collar 12 for mounting the switch in a threaded opening and being screwed at its other end to another housing 31 containing a pair of contacts 36, 37 which are opened and closed by movement of the arm 22 acting via a push rod 28 extending between the two housings 13, 31, the position of the pivot point of the arm 22 being adjustable by a screw 26. In one embodiment, a temperature operated switch comprises a phial 11 containing methyl alcohol and communicating with a capsule 17 comprising a pair of flexible stainless steel discs secured together at their peripheries. The capsule 17, which expands and contracts in dependence on the vapour pressure of the alcohol which is determined by the surrounding temperature, acts via the arm 22 and the push rod 28, on a spring 39 having a pair of integral arms 42 located in notches 44 and a contact 37 which is movable between a pair of fixed contacts 35, 36. The height of a pin 25 about which the arm 22 is pivotable is adjusted by the screw 26 to adjust the temperature at which the switch changes over. The screw 26 is locked in its adjusted position by a coating of resin applied to the upper surface 45 of the switch housing 31. The switch may alternatively be pressure responsive (Fig. 3, not shown).