Patent GB-560916-A (GB)
Title: Improvements in or relating to overload responsive electric circuit breakers
IPC: H01H71/10
Filed: 1942-10-21
Abstract: 560,916. Automatic circuit - breakers. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Oct. 21, 1942, No. 14792. Convention date, Oct. 21, 1941. [Class 38 (v)] The trip mechanism of a circuit-breaker includes a toggle which is spring-biassed towards the tripping position when the breaker is closed and, during opening movement thereof, is restored substantially to its original position. The toggle is normally latched and a compression spring connects its knee to the contactcarrying arm, opening movement. of which is adapted to restore the toggle in readiness for relatching when the tripping force is removed and the breaker is reclosed. The invention is shown in its application to the breaker describedin Specification 555,021 wherein the contact-arm 31 is pivoted at 29 and retained closed against spring-action 85 by means of a main toggle 93, 95 which is pivoted at 101 to a lever 89 pivoted at 91. A further toggle 103, 105, having a fixed pivot 87 to which spring 85 is anchored, interconnects lever 89 and a tripping toggle 107, 109 which is normally retained overcentre by a light spring 128 connected between the fixed pivot 113 of link 109 and an extension 119 on link 107, the extension carrying a part 121 engageable with a part on the handle 141 on backward movement thereof for manual tripping. Tripping on overload is effected by a rod 135 engaging a part 123 of link 109, to break toggle 107, 109 to the right, thus causing lever 89 to rotate clockwise and toggle*93, 95 to move bodily to the right until it collapses downwards, permitting the lever 89 and links 103 .. 109 to restore. The breaker is reset by engaging toggle 93, 95 by a roller 155 on a reclosing lever 145 pivoted at 91 and operable by either the handle 141 engaging roller 153 or roller 130 on a motordriven crank disc 129 engaging a cam surface 132 on lever 145. The rod 135 is adapted to be raised for tripping by means of lever 273 which is pivoted at 272 and connected by a toggle 253, 263 to a fixed pivot 251. The common pivot 261 is connected to .the contact-arm 31 by means of a spring-plunger arrangement 281 in which the spring is always maintained in compression and the amount of compression is greater in the closed position and is such as to pull on plunger rod 287 and, through link 265, tend to rotate lever 273 in tripping direction. This tendency is normally restrained by an extension 255 of toggle-link 251 engaging the tail 227 of a lever 223 which is latched by a part 219 of a pivoted trip member 203. Thus, when member 203 is rotated clockwise, lever 223 rotates clockwise about its pivot 225, so releasing the trip force of plunger 281. When the contact-arm 31 reaches open position, lever 253 is rotated clockwise, so allowing spring 231 to rotate lever 223 into the position where, when the breaker is again closed, it will automatically re-engage trip member 203, which is restored by a spring 213 as soon as the tripping force is removed. The tripping force is applied by a bimetal strip 179 heated by a reduced-section main conductor loop, which also passes through, so as to magnetize, a U-shaped magnetic core 183 adapted to attract an armature 193 and, by means of a spring plunger 195 and notch in. the trip member, rotate the latter electromagnetically into releasing position.