GB537678A - Improvements in electric circuit breakers - Google Patents

Abstract

537,678. Automatic circuit-breakers. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 23, 1940, No. 14470. Convention date, Sept. 22, 1939. [Class 38 (v)] A thermally-released circuit-breaker, adapted also for manual operation in both directions by means of a dead-centre spring, comprises an insulating contact-carrying arm 10 pivoted at 11 and connected through a toggle 14, 15 to the fixed pivot 18, 18a of the handle 26 and a pair of levers 19, 20. A pin 21 at the free ends of the latter serves as anchorage for the dead-centre spring 27 and for an opening-spring 39, the other end of which is connected to the common toggle pivot 16. The links 15 are releasably fixed to levers 19, 20 for manual operation, by lugs 25 on the levers taking over the links 15, and by abutments 24 on the levers normally engaged by latches 22 pivoted on a pin 23 passing through the links 15. The latches 22 are tripped, for automatic release, by a bimetal thermostat which deflects and allows a spring 32 to rotate an insulating lever 30 clockwise about its pivot 31 and, by means of pin-and-slot connection 33, 34, rotate a lever 35 anticlockwise about pivot 23 to engage a lug 41 on latch 22, the spring 39 then breaking the toggle 14, 15 downwards. To reset, handle 26 is moved to the " off " position whereby a projection 40 thereon restores the levers 30, 35 to their original positions, tensioning the springs 42. When the spring 27 has crossed the dead-centre position, levers 19, 20 are moved to their normal "off " position and springs 42 move the latches 22 back to latching position ready for manual reclosure. The pivots 33 are shown as collinear with those 18, 18a so that arms 35 are free to rotate about pivots 33 during manual operation, but if those pivots are displaced the slot must be correspondingly modified, as by curving, Fig. 4 (not shown).