GB920481A - Tumbler switch with spring release - Google Patents

Abstract

920,481. Snap action switches; thermal switches. LANDIS & GYR A.G. Aug. 9, 1961 [Sept. 7, 1960], No. 28801/61. Class 38 (5). A snap action switch comprises a leaf spring 14 cut away to form two tongues 7, 8 extending from opposite ends of the spring, one end of which is clamped and the other is free to move between fixed contacts 20, 21. The two tongues are biased apart by a second spring 15 which engages the tongue 8 between its ends while the free end of tongue 8 moves between two stops. The stops are formed by the upper and lower edges of a slot 26 in a bracket 5 which also serves to support a return spring 23. On depression of the tongue 7 beyond the dead-centre position, first the free end of tongue 8 moves upwards to engage the upper stop and then tongue 8 pivots rapidly about the stop to change over the contacts. The arrangement ensures that a residual contact pressure remains up to the instant of breaking, thus reducing sparking &c. The differential lift can be varied by altering the separation of the stops. Any variation of the lift due to burning away of contacts is stated to be reduced by arranging that the line of support of the spring 15 on the lever 7 in its dead-centre position is closer to the stops than is the line of intersection of the planes containing the tongue 8 in its two end positions (Fig. 10, not shown). In a thermostat (Fig. 4), the sensing element is a heat expansible tube 36 attached at one end to a base plate 27 and at the other to a low expansion rod 35. The free end of rod 35 acts on a pivoted lever 33 to operate the switch. The operating temperature is variable by means of a screw-threaded knob 37 on the end of rod 35.