GB609143A - Improvements in and relating to the trip mechanism of automatic circuit breakers andsimilar electrical switchgear - Google Patents

Abstract

609,143. Automatic circuit-breakers. CRABTREE & CO., Ltd., J. A., BESAG, E., HILL, W. E., and WINTLE, T. D. G. March 6, 1946, No. 7040. [Class 38 (v)] A circuit-breaker, which may be adjusted for hand or automatic reclosing, comprises two blades g, g<1> carrying normally closed contacts h and having between them the upper ends of a stop arm f rotatably mounted and a trip arm c slidably and rotatably mounted on the extended spindle d of a spring-loaded push-button e. On overload, a thermal element (not shown) moves a bar a longitudinally so that a lug a<1> engages the lower part c<3> of the trip arm, rotating it about the spindle d. When set for hand-reclosing, as shown in Figs. 1, 3, as soon as the head c<2> of the trip arm comes out of engagement with a slot g<2> in the blade g<1>, a spring k bearing on the press-button e moves the arms c, f so that the head c<2> enters the constriction between g<3> and g<1> forcing the contacts open. For reclosing, the button e is depressed to carry back the arm f while the arm c is held in the tripped position until arm f enters between the blades g, g<1> at w, after which the shoulder d<1> on the spindle d engages the arm c carrying it back until it is forced into the slot g<2> by blade-spring m<2>. As the button is released the stronger spring k carries the arm f Back to the arm c allowing the contacts to close. For automatic reclosing the button e is pushed in and turned through 180 degrees so that the rib l engages the bearing i and renders the spring k inoperative. In this position the catch c<2> is lifted just clear of the end of the slot g<2> and trip bar a rotates the arm c to bear against the arm g to open the contacts directly, and allows them to reclose as soon as the overload is removed. To avoid retarded " automatic " tripping, the shaft on which the trip arms are mounted is eccentric at v so that compensation is obtained for the gap between the arm c and the blade g. The contacts can be opened manually at any time by depressing the button e so that the stop arm f is forced between the blades at w. Initial adjustment is made by a screw p extending through the cover i to bear on the trough of the blade g<1>.