GB486739A - Improvements in and relating to electric circuit breakers having arc-extinguishing arrangements - Google Patents

Abstract

486,739. Arc-rupturing in switches. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 17, 1937, No. 35015. Convention date, Dec. 17, 1936. [Class 38 (v)] A circuit-interrupter comprises a pair of contacts one of which is movable between open and closed circuit positions, walls of pressureresistant material surrounding the contacts to form a gas-tightly sealed compressionchamber having a volume such that gas-pressures of substantial magnitude are set up therein by the heat of the arc, and a plurality of spaced metallic arcsplitting members disposed adjacent the path of the movable contact for cooling the arc, the metal members and gas-pressures co-operating to effect rapid arc-extinction. The arrangement ensures arc-extinction by employing relatively low gas-pressures, so obviating the risk of rupture of the chamber walls. The compression-chambers of a multi-pole circuitbreaker are identical, and each comprises a cup 16, for example of drawn steel, provided with a slot 17 for receiving the horizontal limb of an L-shaped member 15 forming with a similar member 14 the end wall of the chamber, the member 14, 15 being preferably of die-cast aluminium. The cup 16 is riveted at 20 to member 15, preferably with joint-sealing compound. Members 14, 15 are placed together to form a recess 21, 23 which leads to cylindricalbearing grooves 22 for the shaft 27 and to an aperture through which passes the movablecontact arm secured to the shaft. The arm comprises leaf-springs 30 carrying an arcing- member 31, preferably of nickel, and a contact 32, which co-operates with a fixed contact 35 on an arcing-member 36 secured to a stud 37 extending through insulating bushings 38, 39 to conductor 41. When the parts are assembled in place and secured by screws 58, insulating compound 59a is run in and allowed to set. The configuration of the contacts and arcing- members is such as to blow the arc magnetically outwards into contact with the stack of spaced plates which subdivide and cool it. Plates 49 are magnetic and plates 50 of good heat-conductivity metal, but all may be magnetic or of copper. They are formed with central apertures 63 to equalize the gas-pressure set up by the arc-sections, and with tongues 52 engaging notches in the insulating support 53, an insulating surround 55 prevents contact between the cup 16 and tongues 52. The ends of shaft 27 are squared to receive insulating operating cranks and sealing material is applied at the bearings. The circuit-breaker is manually operable by means of handle 62 and may be releasable to open on overload. Specification 420,042 is referred to.