Patent GB-875014-A (GB)
Title: Improvements in and relating to hydraulically-actuated electrical switchgear
Inventor: FARR IVOR A COURT
IPC: H01H33/30
Filed: 1957-01-11
Abstract: 875,014. Automatic circuit - breakers. ENGLISH ELECTRIC CO. Ltd. Jan. 7, 1958 [Jan. 11, 1957], No. 1134/57. Class 38 (5). A non trip-free hydraulically-operated circuitbreaker has common valve means to control both the liquid supply to and the exhaust from the actuating mechanism, the valve means being operated to connect the mechanism to exhaust before completion of the closing movement of the contacts. The breaker (shown in the open position) is closed by upward movement of an actuating piston 102 within a cylinder 101, the piston being connected by a link 301, an arm 302 pivoted at 303, and a further link 303a, to the contacts (not shown) to close them against an opening spring force A. Pressure liquid is fed to the cylinder 101 from a channel 201 by an inlet valve 204 and exhausted from it by an exhaust valve 203, the valves 203, 204 being connected by a stem 205 and biased to the position shown by a spring 207 which exerts a greater force than a retaining spring 216. The valves 203, 204 are controlled by spring-loaded pilot valves 208, 209 which are interconnected as shown in Fig. 2, by a rocker-arm 212a connected to the stem 208a of the valve 208 by a pin-and-slot connection and to the stem 209a of the valve 209 by a tappet connection. When the closing magnet 213 is energized, connecting rod 213a lifts the rocker arm 212a to open the pilot valve 208 and allow pressure liquid to pass from the channel 201 through the hollow body of the valve 204 to a chamber 206 at the back of the valve 203. The force exerted by the liquid here opens the valve 204 and closes the valve 203 against the biasing spring 207 so that pressure liquid is fed from the channel 201 to the cylinder 101, thus raising the piston 102. As the piston rises, a latch member 306, forming part of a main latching mechanism 304 connected to the link 303a, is rotated clockwise. Shortly before the contacts close, an arm 305 on the member 306 contacts a limit stop 214a on an arm 214 pivoted at 214b and raises a connecting rod 214c so opening the valve 209 and closing the valve 208. The chamber 206 then being connected to the pilot exhaust 215, the biasing spring 207 closes the valve 204 and opens the valve 203 so that the pressure liquid is no longer applied to the cylinder and the remainder of the contactmovement is caused by the inertia of the moving parts. During the clockwise rotation of the member 306, its upper surface 306a slides past the under surface 401a of a trigger 401 pivoted at 402 until, in the " contacts closed " position, the trigger can turn anti-clockwise and allow the holding insert 401c to engage the latch face 306b. Anti-clockwise movement of the trigger 401 rotates a trip latch 403 which is latched in the erect position by a member 406 pivoted at 407. The breaker is opened by energizing a tripping magnet 408 which turns the member 406 clockwise and so unlatches the trip latch 403. The pin-and-slot connection between the connecting rod 213a and the rocker-arm 212a allows the valve 208 to be kept open by liquid pressure and the closing movement thus continues should the closing magnet be deenergized before the contacts are closed. A spring-loaded valve 250 controls the pressure in the chamber 206 and therefore the pressure in the cylinder 101.