GB732943A - Improvements in snap action electric switch mechanisms - Google Patents

Abstract

732,943. Thermal switches. LANDIS & GYR AKT.-GES. June 19, 1953 [June 21, 1952], No. 16965/53. Class 38 (5). A snap-action switch mechanism (Figs. 1, 3, 4, 5) comprises a base-plate 7 having knifeedge bearings 7a, 7b at its opposite ends in which are pivoted the edges 9b, 10b of an operating lever 9 and a switch arm 10, respectively. The lever 9 and arm 10 are held in position by a leaf-spring 11 stressed between hooks 9a, 10a of the members 9, 10, the throw of the mechanism being limited by a contactcarrying tongue 10c which, in one switch position engages a stop 14, whilst in the other, the movable contacts engage the fixed contacts (not shown). The lever 9 is operated by lengthwise movement of a bolt 13 having a nut 12 with trunnions 12a received in bearings 9c formed in the lever 9. The bolt 13 is shown operated by a thermostat element 6 and hence the operating temperature of the thermostat may be varied by rotating the bolt. Figs. 6, 8, 10 show the mechanism applied to a thermostat comprising a liquid-filled space defined by a tube 5, base-plate 1 and diaphragm 4, the plate 7 being mounted on the plate 1, and a cup 6 mounted on the diaphragm receiving the end of the bolt 13. The tongue 10c is moulded in an insulating member 10d freely carrying a contact bridge 19 biased by a spring plunger 20. The stationary contacts 18 are carried by terminals 17 moulded in a detachable housing 15. The amount by which the bolt 13 may be adjusted is determined by a stop 22 which engages shoulders (Fig. 9, not shown), formed on the housing 15, the stop 22 being locked to the bolt in the desired position by tightening a screw 24 in a circular head member 23. A screw 26 adjustably connects a scale disc 25 to the head 23, the disc 25 having a slot 25b engageable by a tool to rotationally adjust the bolt 13.