GB1280137A - An electrical switch - Google Patents

Abstract

1280137 Mechanical switches P T FLUMM 19 April 1971 [9 April 1970] 25222/71 Heading H1N In a push-push snap-action switch the movable contact 1, Fig. 1A, is yieldingly urged by spring 10 against alternate contacts or stops 7, 8 both against the direction of actuation of the operating member 4 to engage lugs 7a or 8a and transversely across an over-centre position towards faces 7b or 8b. In operation depression of the operating member 4 after some lost motion initially engages an extension arm 11, 14 of the contact 1, in recess 5 and forces the contact 1 down transversely sloping face 12 until the plane of the arm 11 and contact 1 moves over-centre of the spring attachment point 17, Fig. 1C, whereupon the contact 1 snaps across to engage the face 13 of the opposite contact or stop 8. On retraction of the operator 4 the spring 10 urges the portion 14 out of the recess 5 of the operator 4 and into the recess 6 while the further retraction permits the contact 1 to rise along face 8b, to engage lug 8a. In a particular embodiment the movable contact 42, Fig. 2, has a bent up loop 44 engaged by the grooved underside of a pivoted actuator 58 having a pin 60 for the attachment of the over-centre tension spring 48. The actuator 58 has arcuate lugs 68 for pivoting in recesses 72, 74 of the housing 20 and by an insulating cover plate 76 held in position by a top plate 88 having bent over attachment lugs 92, 96. The plate 76 and recess 85 in the housing further operate as limiting stops for the actuator 58 by engaging a projection 84 thereon. The fixed contacts 26, 52 and central terminal 30 are engaged in slots (as 22, 24) in the housing wall and are also retained in position by the insulating cover late 76. In further modification (not shown) the moving contact may have an extension which is visible through an aperture (122), Fig. 5 (not shown), in the housing to show the condition of the switch. The movable contact may also comprise a stamped out plate 166, Fig. 9, having an upwardly extending lug 180 engaged by a pivoted grooved plate 176 on a pivoted actuator 172 depressed by a pushbutton 182. The combined return and snap spring 174 is attached between the lug 180 and a bent up portion of the actuator extending between a pair of pivot lugs 168 on a terminal 158. The opposed fixed contacts 160, 162 may have a layer of silver 190 on the contact faces.