GB1304277A - - Google Patents

Abstract

1304277 Retractive switches CRAIG & DERRICOTT Ltd 19 April 1971 [26 March 1970] 14702/70 Heading H1N A switch has both snap-acting and positivelyactuated contact members operable by a common operating member. As shown, a retractive plunger 2 carries a leaf-spring bridging contact member 16 secured between collars 9 and 18 and having two tension springs 17 whereby depression of plunger 2 causes the contacts 14 and 15 to snap away from fixed contacts 11 and 12. Additionally a rigid bridging contact plate 21 is carried by an insulating assembly 23, 24, which is axially slidable on plunger 2, and normally bridges fixed contacts 10 and 13. After a preset amount of lost motion of plunger 2 a collar 26 thereon engages the part 23 and thus opens contacts 10, 19 and 13, 20. The relative disposition of parts is preferably such that the snap-acting contacts 14, 15 are opened before the positivelyactuated contacts 19, 20, but the two actions may be in the reverse order or simultaneous. The plunger 2 may be formed in two structurally separate parts, one slidable in socket 7 and subject to retraction spring 8 and the other slidable in a wall of the housing 1. In a second embodiment (Fig. 4, not shown) common fixed contacts (10a and 13a) are provided between the plate (21a) and leaf spring (16a) and the both sets of contacts are normally open. In the embodiment of Fig. 5 the positively actuated contacts 19b, 20b form the "fixed" co-operating contacts for snap contacts 14b, 15b and if initial movement of plunger 2b does not snap the contacts open then a collar 26b positively moves contacts 19b, 20b while projections 29 of housing 1 prevent contacts 14b, 15b from following. To connect the contacts of this embodiment into an external circuit flexible connections (not shown) would be provided.