GB1276026A - Electrical switch components and switches formed thereby - Google Patents

Abstract

1276026 Snap-action and retractive switches J O ROESER 31 Oct 1969 [25 Nov 1968] 53546/69 Heading H1N In a snap-action switch each movable contact 109a, Fig. 5, comprises a pair of spaced legs 112, 114, Fig. 8, pivotable on knife edges 132 and having a pair of upper and lower contact regions 128, 130 formed by curving the end 118 of the contact to a part-cylindrical form. A centre portion of the cylindrical end 118 has a stamped out recessed portion 124 on which the end of the snap-action tension coil spring 120 is hooked at a point which is at a greater distance from the pivot edge 132 of the blade than that of the contact regions 128, 130 whereby the vertical component of the spring force has a mechanical advantage in applying contact pressure and thereby reduces contact bounce. In the example described a pair of blades 109a, 109b is arranged in grooves 106 on opposite sides of a rectilinearly moving and conductive actuator part 96 moulded on a push-button 14 and engaging a pair of return springs 76, 78 resting on a central terminal 174. One spring 76 may be of stainless steel for mechanical strength and the other spring 78 may be of a silver-magnesium, nickel alloy or beryllium-copper alloy to provide a current carrying capacity. The fixed upper and lower contacts 146, 148, 156 are mounted in slots such as 50a, 50b in the casing 42 and sealed by potting compound 198. Each contact may be formed integral with a terminal 158 and bent up from a stamped out bimetal plate having a layer 162 of silver with a brass backing 164 which may be silver coated. The mounting of the lower terminal 174 is described and claimed in the Specification 1,276,027 of the divided application. In a modification the actuator may operate more than one pair of contacts and may have push-pull actuation, the return springs 76, 78 being omitted. The contacts may operate simultaneously and the push-button may be resiliently coupled to the central actuator 96 by means of a rubber ring (236), Fig. 16 (not shown), whereby energy stored during initial compression of the ring (236) is released on actuation of one set of contacts to ensure the simultaneous action of the other set. A further embodiment, Fig. 20 (not shown) is described in which the fixed contacts are staggered at different distances apart, whereby a sequential actuation of different sets of movable contacts is obtained due to the contacts going over centre at different stages of movement of the actuator.