GB143263A - Improvements relating to electric switches - Google Patents

Abstract

143,263. Murray, E. T. R., and Shotter, G. F. May 14, 1919, [Convention date]. Electro-magnetic switches and interrupters.- A switch particularly adapted for use as a current limiter comprises a switch arm 1 pivoted at 2 and so balanced that normally the bridging contact 3 is maintained in engagement with the fixed contacts 5, 6 by gravity and is latched in this position, to prevent accidental movement, by a bell-crank lever 19 one arm of which engages a pin 20 on the contact arm. The main circuit passes through a wedge-shaped operating winding 7 having a fixed U-shaped yoke 8 which, when an excess current passes, attracts the pivoted armature 9 which, at the end of its movement, strikes a rod 12 and moves the latch out of the latching position and, through the intermediary of a bent spring-arm 15 carried by the pin, pushes the switch arm out of the contact position whereupon the arm swings upwards and returns in a time depending on its natural frequency of oscillation. The upwards movement of the arm removes a pin 21 carried thereby away from a spring contact 22 which closes against its co-operating contact 23 and short-circuits the operating winding. On the return of the contact arm the shortcircuit is removed and if the overload persists the arm is again moved under the action of the full impact of the armature 9. Specifications 5200/15 and 5201/15 are referred to.