GB534286A - Improvements in or relating to pressure relieving means for electric circuit interrupters of the liquid immersed or other type in which pressure is generated upon establishment of an arc or arcs - Google Patents

Abstract

534,286. Liquid-blast switches; switch cases. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Sept. 20, 1939, No. 26229. Convention date, Sept. 21, 1938. [Class 38 (v)] A pressure - relieving device comprises a metal cap 20 normally maintained against the metal cylinder 18 which is carried on a metal plate 16 seating on a porcelain housing 14, within which is an insulating strain cylinder 22, the upper metal collar 24 of which is bolted to a metal annulus 30 which is bolted in turn to plate 16. The relative lengths of 14, 22 are such that, when clamped together, 14 is in compression and 22 is in tension and takes all lateral stresses. The member 22 houses two interrupting units, one above the other, the upper 34 having a flanged metal casing 38 with four lateral arms 40 whereby it is bolted at 42 to plate 30. Also secured to arms 40 are four guide rods 68 united above by a stop plate 70 against which bears the upper 64 of two pressure-plates, the lower 66 of which carries the contactoperating member 56. When the latter is released by a straight-line operating mechanism, Fig. 1 (not shown), a battery of compression springs 62 drive it downwards, separating the movable contact 58 from fixed contacts 52 and drawing an are in extinguishing liquid. Arc products escape through vents 74 in the units and if the pressure is excessive it lifts the cap 20. The latter carries a bolt 76 the head 80 of which loosely fits in a hole 82 in plate 70, and bears on the inner ends of four levers 88, which fulcrum on the upper edges of holes 86 in a boxlike structure 84 fast on plate 70. The free ends of the levers 88 have conical recesses 90 engaging the ends of bolts 92 threaded in the pressure-plate 64, so that upward movement of cap 20 and bolt 76 depresses the plate 64 and compresses the springs 62, so increasing the switch-opening force of the latter. When the pressure subsides, the springs act reversely to restore the cap, the flange 98 guiding it back to its seating. Each unit 34 comprises an outer casing 44 in which are insulating washers 45, 46 of alternately different diameters forming a corrugated arc-chamber 48. The member 56 carries washers 60. 61 forming a corrugated insulating surface which limits the dimensions of the arc-chamber in opening circuit. The contact 58 of the upper unit is connected by a conducting sleeve 57 and flexible shunts 59 to the fixed contacts of the lower unit, the contact 58 being enlarged on its left-hand side so as to draw the arc.