GB982544A - Improvements in or relating to tripping devices for automatic circuit breakers - Google Patents

Abstract

982,544. Automatic circuit-breakers. G. ALLARD. July 19, 1961 [July 20, 1960], No. 26176/61. Heading H2B. A tripping device for a circuit-breaker which comprises a contact-carrying lever biased to the open position but retained closed by a catch, and a percussion member spring-loaded to its release position against a restraining device which when operated allows the percussion member to impinge on and actuate the catch, thereby opening the contacts, is characterized by the catch and percussion member being automatically reset by the tripping movement of the contact-carrying lever. In the double-pole circuit-breaker described, an insulating plate 28 carries main contacts 5a and 5b co-operating with fixed contacts 2a and 2b respectively, arcing contacts 5<SP>1</SP>a and 5<SP>1</SP>b being provided as shown. A spring 36 urges plate 28 against a knife-edge 35 on the reset button 21 and a spring 8 urges a catch plate 6 to underlie the extension at the rear of plate 28 (see especially Fig. 8). Percussion members 10a and 10b are pivoted at 11a and 11b (see Figs. 9 and 12) and urged by springs 16 but restrained by the ends of U-shaped bimetal strips 14a, 14b, respectively, which carry the current to fixed contacts 2a and 2b. Depression of button 21 (against spring 36) pivots plate 28 about the top edge of catch plate 6 and closes contacts 5a, 5b, 5<SP>1</SP>a, 5<SP>1</SP>b on to contacts 2a and 2b, a latch 40 (Fig. 8) engaging a notch 38 to retain the button 21 in the depressed condition. If either bimetal 14a or 14b is now flexed by current overload its associated member 10a or 10b is released and a tongue 9 thereon (Figs. 9 and 12) impinges on catch plate 6 to remove it from beneath plate 28, allowing spring 36 to pivot plate 28 and open the contacts. Plate 28 also impinges upon latch 40 to release the button 21 which moves upwards together with plate 28, thereby restoring the members 10a and 10b such that plate 6 returns to the position shown in Fig. 8 and the device is automatically ready for reclosing as soon as the flexed bimetal has returned to its normal position. Depression of button 21 before the bimetal has restored merely allows the member 10a or 10b to push the catch 6 aside and contacts 5 cannot then be moved down far enough to engage contacts 2. A button 64 is provided for manual tripping by acting mechanically on bimetal strip 14a, for example. Resistor shunts 52 and 53 (Fig. 10) may be connected in parallel with a bimetal strip by adjustment of screws 55 and 56, thereby providing alternative current ratings. Ambient temperature compensation may be provided by a bimetal 50 (Fig. 12) acting as one leg of a percussion member, adjustment being possible by means of a screw 51.