GB1283800A - Improvements in and relating to earthing switches - Google Patents

Abstract

1283800 High voltage switches; fluid actuation of switches COQ NV 28 Oct 1970 [4 Nov l969] 51255/70 Heading H1N An earthing switch comprises fixed contacts 2, 3 separated by insulation 1 and having a movable contact rod 4 connected to earth via contact 2, metal block 6, cover 7 and earthed metal envelope 5, the rod being actuated by a piston 9 attached to it which moves within double-acting cylinder 8 between end stops 10 and 11, and is connected to a screwed shaft 36 having a biasing arrangement at its free end to bias the piston into its two end positions. Valve housings 18 and 19, which control the piston 9, are connected to cylinder chambers 12, 13 respectively via chambers 14, 15 and passages 16, 17. In Fig. 3 the chamber 20 of housing 18 is connected by valve 21 either with the atmosphere via passage 22 or with chamber 24, the valve being operated by piston 25 loaded by spring 26. Cylinder chamber 27 can either be connected to chamber 24 or to atmosphere via a three-way valve 30. Chamber 24 is connected to chamber 35 through passages 32, 33, 34 which latter chamber is filled with compressed gas. In both piston end positions the valves in housings 18, 19 are in the position shown and both the cylinder chambers 12, 13 are under high pressure. For the operation of the switch the respective valve 30 is changed over so that either of the chambers 12, 13, connected to a respective valve chamber 27, is connected to atmosphere, thus causing the piston to move to the other end position. Screwed shaft 36 is mounted in the hollow contact rod and cooperates with rollers 40, which act as a nut, mounted in the piston 9. Piston 9 and rod 4 are locked against rotation by axial rods 41 such that on rotation of the screw 36, the piston and rod move axially, and vice versa. Mounted on end 36a of the screw is a locking disc 42 which co-operates with locking roller 43 mounted on an arm 45 loaded by spring 46, which arrangement, Fig. 2 (not shown), locks the piston in its respective end positions. The switch can be operated by a spanner, Fig. 4 (not shown), engaging projections 47. Locking disc 42 has marks (50, 51) which indicate the switch position through a casing window.