GB514759A - Improvements in and relating to electric gas blast switches - Google Patents

Abstract

514,759. Gas - blast switches. BRITISH THOMSON-HOUSTON CO., Ltd. June 2, 1938, No. 16558. Convention date, June 5, 1937. [Class 38 (v)] The fixed contact of a gas-blast switch comprises contact-elements so individually mounted and arranged that, on opening the switch, they separate to form at the point at which the arc is struck an opening of greater cross-section than that of the movable contact. Thus, in the closed position, gas leakage is minimized, and during opening the maximum blast-area is available. The fixed contact of Fig. 2 comprises elements 1 supported within a nozzle formed by elements 8, 28, the elements being pivoted to operating levers 2, which may be resilient but, as shown, are urged by springs 4 so as to bear at their lower ends against the widened part of the movable contact 6. When the latter is lowered to open circuit, the shoulder 7 allows the elements 1 to be forced outwards by springs 5, so providing an enlarged outlet for the upflowing blast. The arc formed is blown from elements 1 on to the member 8 and thence to arcing-contact 9. In Fig. 3, contact elements 1 arranged as in Specification 494,829, are provided with springs 16 to press them against the movable contact 6 and, at their bearing surfaces 10, against the retaining wall 11. A castellated operating-member 12 is provided, the upward projections of which, when the member 12 is rotated clockwise by the operating member for contact 6, engage the elements to move them outwards. In Fig. 5 (not shown), the elements 1 are slidable on current-conducting ball-bearings and the elements 2 are resilient. In other forms, Figs. 6-9 (not shown), the nozzle 28 closely surrounds the movable contact, and a modified linkage is provided. Separation of elements 1 may be effected just before, or at, current-zero, as by locking the levers 2 by a device which is released at current-zero, or by operating the member 12 of Fig. 3 by a spring or weight set into operation by zero-current responsive means.