GB764074A - Improvements in electric circuit interrupters having sickle-shaped contacts - Google Patents

Abstract

764,074. Liquid-blast switches; switch contacts. ALLIS-CHALMERS MANUFACTURING CO. Sept. 16, 1954 [Nov. 3, 1953], No. 26898/54. Class 38(5) Each arc-interrupting unit in a liquidblast switch has a stationary contact 11 formed by a plurality of segments biased together and grooved to form slots 17, 18 which provide contact surfaces co-operating with a moving arcing contact 10 on a pivoted sickle-shaped member 13 and a second moving contact 12, a barrier plate assembly 42 providing an arc extinguishing passageway 63 receiving the sickelshaped member 13. The stationary contact 11 is tubular and may have two segments biased by springs 15 which provide pivotal mountings for the segments for alignment purposes. The upper slot 17 is rectangular and forms a pressure generating enclosure whilst the lower slot is cylindrical. The barrier plate assembly 42, Figs. 6 to 11 (not shown) is arranged to provide transverse blasts of liquid across the passageway 63 when pressure is set up in a chamber 9 on the downward movement of a piston 37. This liquid may be exhausted from the assembly 42 past the contact 11 into a lower barrier plate assembly 43. Alternatively, a pipe plug 59 may be removed so that the liquid and arc gases may exhaust directly into the tank housing the switch. The lower assembly 43 may provide helical passages. Final arc extinction is ensured by two parallel resistors 45 (one shown) connected between the contact 10 and an auxiliary electrode 48 between the assembly 43 and an outlet nozzle 55. The contact 12 is secured to, and operated by, a conducting cross-bar 3 which, when raised, closes the contact 10 against the bias of springs 27 through the medium of a push rod 26 and links 29 pivoted at 28 to the sickle-shaped member 13 and at 30 to a bifurcated metallic cap member 32 on the push rod 26. The rod 26 also moves a push rod 34 to raise the spring-biased piston 37 and a valve 36. When the bar 3 is lowered to open the switch, the downward movement of the rod 26 under the bias of the springs 27 opens the contacts 10, 11 and simultaneously, or with a slight delay, the contacts 11, 12 open. The piston 37 moves downwardly with the rod 26 if the current to be interrupted is low or when permitted to do so by the pressure in the chamber 9 if the current is high. Specification 764,073 is referred to