GB648221A - Improvements relating to push button electric switches - Google Patents

Abstract

648,221. Latching and unlatching switches. DOWTY EQUIPMENT, Ltd., and SNELL. M. S. Dec. 22, 1948, No. 33069. [Class 38(v)] In a push-button switch having means whereby the button can be locked against normal operation, said means may be overcome in an emergency by the application of a force in the same sense as, but considerably in excess of, that necessary for normal operation. A tube 12 forming part of a push-button is slidable on a stem 11 having an annular channel 13 engageable by a portion 16 of a locking member in the form of a wire loop 14 pivoted at 15 to the switch base. The loop is attached to the armature 17 of an electromagnet 19 which when energized, unlocks the pushbutton by withdrawing the loop from channel 13 against .the action of a spring 20. Emergency operation of the push-button may be effected by pressing hard thereon, and causing the tube 12 to deform portion 16 into engagement with a chamfered surface 22 in the channel 13 which deflects said portion outwards to a position in which it may be byepassed by the tube. In a modification, the locking member is rigid and the push-button comprises inner and outer end parts united by a bowed strut. Normally the two parts move together and when locked, the locking member engages the inner part. In an emergency, the application of sufficient pressure to the push-button causes the strut to bow still further and permits the outer part to move relatively to the inner part and in so moving actuate the switch.