GB547681A - Improvements in or relating to operating mechanisms for electric circuit interrupters - Google Patents

Abstract

547,681. Fluid-pressure servomotor-control systems. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. March 7, 1941, No. 3121. Convention date, March 9, 1940. [Class 135] [Also in Group XXXVII] A fluid-operated gas-blast switch comprises, for each phase, a movable contact 28 which is rotatable about pivot 32 to engage and disengage a fixed contact 16 in an arc chute 22 supported on the blast pipe 12 on a main reservoir 6. Movement of the contact is effected by a double-acting piston 42 in a cylinder 40, Fig. 5, the piston rod 44 operating through a lever 48 a shaft 50 which is common to all the phases. Each contact is closed by a toggle 54, 56 moved overcentre against a stop 55, the toggle-link 54 having a cam surface 58 which engages a roller 60 on a lever 62 pivoted at 64 so as to open the blast valve 68 at each actuation. Similar control means are provided for each end of cylinder 40, comprising solenoid-operated opening and closing valves 70, 72 which communicate, respectively, with auxiliary reservoirs 83, 85 defined by barriers 86 in cylinders 82, 84 and adjustable along threaded rods 88 so as to provide gas-storage for a single operation. Each barrier comprises a threaded collar 90, a washer 92 of yieldable material, a metal washer 94, and lock nut 96 and washer 98. Air passes into cylinders 82, 84 by way of orifices 100 which have removable plugs 102 for adjusting the rate of flow. Operation of a solenoid 136 admits air from cylinder 82 or 84, through a valve 124 and passage 126 to depress a spring-piston 130 which first closes ports 134 in the valve casing and then depresses valve 108. The descent or ascent of piston 42 is initially rapid but slows up owing to the building-up of pressure behind the piston, due to the ports 134 of the other valve and also to the relatively small size of the auxiliary source 83 or 85 which may have only half the volume of cylinder 40. A switch, Fig. 1 (not shown), operated by shaft 50 de-energizes the solenoid at the end of the operating stroke, the springs returning the valve 108 and piston 130 to their closed positions. In order to obtain a quick reversal of piston 42 if the switch closes on to an overload and valve 70 is operated, the final closing movement of piston 42 lifts a rod 150 and opens a valve 144 against the action of spring 148, so enabling the initial return movement of the piston to take place quickly. The space 83 is made larger than 85 so as to ensure the switch opening on overload in the event of inadvertent operation of both solenoids 136.