GB432264A - Improvements in and relating to fluid-operated electric switches - Google Patents

Abstract

432,264. High tension switches. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. April 24, 1935, No. 12369. Convention date, April 24, 1934. [Class 38 (v)] Pneumatic actuation.-A switch which is normally moved to the " off " position by a fluid pressure medium, which preferably serves also to extinguish the arc, is provided with additional means influenced by the switch position for admitting the pressure medium to the driving device automatically if the switch contacts start moving towards the " off " position under the influence of other forces. In the arrangement shown, when the switch is to be opened, compressed gas is led from a container 1 to the driving cylinder 3 and to the contact points 4 through a valve 2 which is normally operated by an electromagnetic device 5 controlled by hand or by an excess current relay. The switch is closed by admitting compressed gas to the cylinder 3 through a pipe 22, and is held in the closed position by a latch (not shown). If the switch fails to latch properly, or for any other reason moves towards the open position without the opening of the valve 2, a pin 12 on the switch rod 11 moves a lever 13 loosely pivoted about a shaft 14 to which a ratchet 15 and cam 16 are keyed. A pawl 19 on the lever 13 engages the ratchet and moves the cam into engagement with a roller 17 on a lever 8 to open a valve 9 and admit compressed gas to a cylinder 7 having a piston 10 connected to the valve 2 through a bellcrank arrangement 6. The arrangement is such that the valve 2 is opened before the actual separation of the contacts 4, so that the switching-out movement is completed by compressed gas in the normal manner. When the switch reaches the " off " position, the pawl, 19 is released by engagement with a stop 20 and a spring 21 returns the ratchet 15 and cam 16 to their inoperative position, allowing the valve 9 to close again. Instead of actuating the valve 9, the switch rod may be arranged to close a circuit for operating the valve 2 in the event of the switch rod moving towards the " off " position under abnormal conditions.