Patent GB-378471-A (GB)
Title: Improvements relating to electric switches or circuit breakers
IPC: H01H33/92
Filed: 1931-05-09
Abstract: 378,471. High-tension switches. BRITISH ELECTRICAL & ALLIED INDUSTRIES RESEARCH ASSOCIATION, WHITNEY, W. B., WEDMORE, E. B., and CASSIE, A. M., 36, Kingsway, London. May 9, 1931, Nos. 22492 (divided on 378,493) and 22502. [Class 38 (v).] In oil or gas break switches in which a blast of the fluid (or a spray of liquid particles) is forced across the arc at break, the movable contact in closing acts directly on a spring-pressed piston to compress it so that in the breaking movement the piston follows the moving contact and forces a stream of fluid across the arc, the movement of the piston being finally arrested and the contact continuing its movement. As shown in Fig. 1, the piston 7 in addition to control by the spring 14 according to the invention is also acted upon additionally by the differential action of the arc gases on its unequal upper and lower surfaces as described in Specification 378,493. The fixed contact 4 is mounted in a sleeve 5 depending from the cover 2 of the container which is supported as a whole by the insulator 3. The sleeve is slotted and through the slots the arms 16 of a spider project into bearing engagement with the pistons. The spider is acted on by the spring 14. In closing, the moving contact 11 engages an insulating pin 19 attached to the spider and compresses the spring. In breaking the circuit, the spider and with it the piston 7 follows the contact 11 and, as the contacts separate, a jet of oil is forced between them. The are gases acting differentially on the piston assist the downward movement thereof and when this is completed the contact 11 continues its movement and leaves the pin 19. At its lowermost point the piston opens ports 22 relieving the pressure on its upper face whereupon the piston rises somewhat under the action of the spring 12 and when the switch is closed again the pressure of the spring 14 is taken off the piston by the engagement of 11 with 19 so that the piston resumes its set position. The differential piston may be dispensed with and the spring 14 act upon a simple central piston to force oil across the gap. In this form the movable contact may be surrounded by a nest of baffle plates with a vent to one side as described in Specification 366,998. In a modified form, a piston located as in Fig. 1, but with equal upper and lower faces is controlled by a single spring set by the movement of the contact-member. The piston may be mechanically connected with the trip mechanism of the switch to lock it at all positions except the fully raised position of the piston. In Fig. 6 two breaks in series are provided for by means of an intermediate contact 27 mounted on the spring-controlled piston 7. The blast of fluid across the second break passes through the tubular contact 11 and through ports 30 therein to the main oil tank. A spray of oil may be forced across the arc by arranging the pin 19 (through which the moving contact acts upon the piston) in the form of an injector, Fig. 7 (not shown). In Fig. 8, the hollow pin 35 (correspond to 19) slides through a closing plate 40. The piston, on moving downwards, forces oil and entrapped gas as a spray through the ports 37 and through the hollow pin across the arc. Specifications 278,764,318,292 and 330,616, [all in Class 38 (v), Electric switches &c.], also are referred to.