GB630526A - Improvements in and relating to thermally responsive electric circuit breakers - Google Patents

Abstract

630,526. Automatic circuit breakers. BRITISH THOMSON-HOUSTON CO., Ltd. July 11, 1947, No. 18520. Convention date. July 11, 1946. [Class 38(v)] An automatic circuit-breaker has a curved bimetallic strip which is stressed by an actuating member during the closing operation, the contacts then being latched closed by the strip abutting a projection on the actuating member. A switch arm 1 is secured to the free end of the bimetallic strip 2 and carries a contact 5 which co-operates with a fixed contact 4. To close the circuit-breaker an actuating member 6 having a projecting pin 9 is turned clockwise, when the pin 9 in engaging the side of the arm 1 moves the arm to close the contacts 4, 5 and stress the element 2. This stress is reduced when the pin 9 passes through an opening 10 allowing the element to move back until its abuts a projection 11, the contacts remaining closed. On overload the strip 2 bends and releases itself from the projection 11 so opening the contacts as shown in dotted lines in Fig. 4. After tripping the circuit-breaker is reset by turning the actuator 6 anti-clockwise, so moving the pin 9 up the back of the arm 1 until it passes through a further opening 13 into the position shown in Fig. 1. The circuitbreaker may be opened by hand in a similar manner, the initial anti-clockwise movement of the actuator 6 disengaging the projection 11 and allowing the contacts to open, a further projection 14 preventing rebound.