GB855730A - Improvements in and relating to electrical circuit-breakers - Google Patents

Abstract

855,730. Automatic circuit-breakers; contact-members for switches. CHILTON ELECTRIC PRODUCTS Ltd. June 10, 1958 [March 27, 1957], No. 9966/57. Class 38 (5). In an automatic circuit-breaker having a contact-carrying switch arm 2 which may be closed by angular displacement against spring-bias by a cam 3 about an abutment 5 movable under overload conditions to release the arm, the arm comprises an outer part 22 co-operating with the abutment 5 and an inner contact-carrying part 21 capable of limited pivotal and sliding movement relative to the outer part 22 so as to produce a wiping action between the contacts 11, 23. In the arrangement shown, a guide-pin 26 passes through a slot 28 in the inner part 21 and through holes in the outer part 22, the ends of the pin being guided by curved slots 9 formed in the two halves of the outer casing 10. A further pin 27 mounted in the outer part extends through a slot 29 arranged angularly with respect to the slot 28 in the inner part. With this arrangement the inner part pivots with the outer part during the initial closing operation until the edge of the moving contact 23 remote from the cam touches the surface of the fixed contact 11, Fig. 3. Thereafter, as the angular movement of the outer part 22 by the cam 3 about the abutment 5 is completed, the inner part is caused to pivot about the pin 26 and at the same time the relative motion between the pin 27 and slot 29 causes the inner part to slide within the outer part so that the contact 23 slides on the contact 11 as it is turned into full engagement with the contact 11, Fig. 10. In the event of an overload condition, a bimetallic element 8 or an electromagnet 7 turns a pivoted member 6 to move the abutment 5 from the end of the switch arm 2 which then pivots about the cam 3 to open the contacts. During this tripping action the cam 3 is returned to the " off " position and the mechanism is automatically reset. The contacts open in a compartment having spaced plates 101 for arc quenching purposes and gases produced by the arc are discharged through passages 102, 104 and a spring- pressed valve 103 which conserves the pressure of the gases whilst limiting the pressure to a safe value. The casing 10 is in two halves formed with recesses for pivots 31, 61, the curved slots 9, slots for the plates 101 and recess, seatings, outlets &c., for the terminals, springs and the electromagnet. The casing 10 may be provided with " knock-outs to permit the interconnection of the tripping members 6 in the adjacent units of a multiple unit circuitbreaker.