GB848522A - Improvements in and relating to electric circuit breakers - Google Patents

Abstract

848,522. Automatic circuit-breakers. MECHANICAL PRODUCTS Inc. April 17, 1957 [May 29, 1956], No. 12619/57. Class 38 (5). The overload protection arrangement of a circuit-breaker, Fig. 1, includes a " hot " wire 63 which is electricallyconnected to the moving contact 47 via a pivotally-mounted element 51 forming part of a latch device normally keeping the contacts 19, 47 closed. Expansion of the wire 63 on passage of overload allows the element 51 to pivot and release the latch so that the spring 49 can move the arm 43 anticlockwise and thus open the contacts. The plunger 21 simultaneously rises under the influence of a spring 33 and the circuit-breaker can be reset by pulling a knob 27 on the plunger downwards. The circuitbreaker may also be opened manually by pulling the knob 27 down until the flanges 37 on the plunger engage detents 41 on a spring 39 attached to the casing. Indication of whether the breaker is closed or has been opened manually or by overload is given by the position of the knob 27 and differently-coloured rings 31, 32 above the knob. Fig. 5 shows a modification which is not equipped for manual operation. When the " hot " wire 147 extends on overload the spring 143 pulls a lever 131 to the right and releases a pawl 135 from the end of the pivoted arm 123 carrying the moving contact 127. A spring 129 opens the contacts and the plunger 119 is raised by a spring 121. The breaker is reset by pushing down the plunger. The tension in the wire 147 may be adjusted by a screw 155. Fig. 8 shows a further form having a fixed contact 221 mounted on one main terminal 219 and one end of the " hot " wire 251 connected to the other main terminal 215. The other end of the wire is attached to one arm of a bell-crank lever 237 pivoted at 239 and the other arm of the lever carries a pawl 241 which engages one end of a pivoted arm carrying the moving contact 223 at its other end. Extension of the wire 251 on overload causes the lever 237 to be moved clockwise by a spring 253, thus unlatching the arm 225 and allowing the contacts to be opened by the spring 235. Simultaneously the plunger 229, on which the arm 225 is pivoted, is moved downwards by a spring 231. In the open position, the pawl 241 completes a circuit from the main contact 215 to an auxiliary terminal 255 which is in a warning circuit. The " hot " wire may, in all forms, be shunted across the load current.