GB472496A - Improvements in or relating to electric switches or circuit breakers - Google Patents

Abstract

472,496. Automatic circuit-breakers. CIRCUIT BREAKERS, Inc. March 23, 1936, No. 8691. Convention date, June 18, 1935. I-Class 38 (v)] In an automatic circuit-breaker of the kind in which the circuit-closing member is moved into the closed position against the action of a spring and is retained by holding mechanism which is actuated to trip or release the circuitbreaker on the occurrence of an overload, the switch-actuating member is entirely separate from the holding mechanism and is disconnected from the circuit-closing member during the final circuit-closing movement by the action of a member carried by a stationary part of the switch. In the construction shown in Fig. 1, the switch is mounted in a threaded plug 30 bearing a metal shell 52 and a central contact 31 connected to a spring contact 67 with which a movable contact 68 engages to close the circuit. The contact 68 is carried by a plunger 36 mounted in guide members 69, 72 and normally urged to the "off" " position by a spring 71. The switchactuating member comprises a button 74 carrying claws 76, which, when the button is pressed inwards against the action of a spring 80, engage the plunger 36 and carry the movable contact 68 into engagement with the contact 67. In this position a collar 70 on the plunger engages an opening in a spring plate 83, which grips the collar and holds the plunger in the circuit-closing position. As this position is reached, the nose 79 of a fixed sleeve 78 carried by the guide plate 69 engages the claws 76 and disconnects them from the plunger in order to provide a trip free release. The plunger is released on overload by the bending of a U-shaped bimetallic member 81 carrying the current ; it can also be released manually by a push button 86, both the member 81 and button 86 engaging the end of the spring plate 83. In a modification, Fig. 4, a bridge member 87 is slidably mounted on the plunger 36 and carries one or more indicators 89 which project above recesses 90 in the casing 66 when the switch is open. When the switch is closed, a spring 88 presses the bridge member downwards, and the indicators are drawn into the recesses. In another construction the bimetallic strip itself constitutes the detent device and carries a central ring adapted to receive and hold the collar on the plunger until the collar is released by the bending of the strip. In the construction shown in Figs. 8 and 12, an enlarged head 114 on the plunger 36 is adapted to be received in and held by bulges 113 on a pair of bimetallic members 110, 111 mounted in the base of the plug 30. On overload, the strips bend outwards to release the plunger, or they may be spread apart to effect the same result by means of a wedge member 124 operated through a bell-crank lever from a push button. To prevent arcing when the circuit is opened, a wiping contact 118 secured to the plunger, engages a stud 117 of high-resistance material and provides a shunt circuit during the first part of the opening movement.