GB466125A - Improvements in draw-out electric switchgear - Google Patents

Abstract

466,125. Switchgear structures. BRITISH THOMSON-HOUSTON CO., Ltd., GOODALL, J. M., and HAMLYN, W. P. Nov. 21, 1935, No. 32334. [Class 38 (v)] In switchgear of the draw-out type, particularly for controlling the supply to a trailing cable used in mines, an earthing device is mounted on the fixed part of the gear and connected between the circuit-breaker plugging contacts and the incoming or outgoing cable connection, and is so arranged that actuation thereof to the closed position automatically trips open and holds the breaker open before the device moves to the closed position. In a 3-phase application, three clip contacts 3 in the flameproof chamber 1 are solidly connected to the phase connections 4 and adapted to be connected together by means of blades on a pivoted bar 6, which is connected by a flexible, braided strip to a terminal in connection with an earth bar. The operating handle 7 is connected to bar 6 through a spindle 10 having a slotted end to give the requisite lost motion, and dead-centre springs may be provided. During the taking-up of the lost motion, the handle 7 depresses a guided pin which rotates a spring- controlled shaft 12 which, through connecting rod 13, holds up the trip bridge controlling the breaker mechanism, so producing the trip before the earthing blades move and preventing closure of the breaker 2 while the blades are " on." The blades may be padlocked in both positions. Where means are provided for tripping the breaker by the withdrawal thereof from the fixed part of the gear, such feature can be derived from the earthing device by arranging for the rod 13 to be moved to the right for tripping purposes, in which case withdrawal of the breaker will automatically cause tripping.