GB752947A - Electric circuit breaker with hydraulic motor controlled by a hydraulically biased valve - Google Patents

Abstract

752,947. Automatic circuit-breaker; actuation of switches. ALLIS-CHALMERS MANUFACTURING CO. May 17, 1954 [May 26, 1953], No. 14437/54. Class 38(5) [Also in Group XXIX] A circuit-breaker is closed by a piston actuated by liquid stored under pressure in a pneumo-hydraulic accumulator and released under control of an electromagnetically-actuated valve having land surfaces separated by grooves which are so shaped that liquid exhausted from beyond the piston assists the operation movement of the valve. In the circuit-breaker shown, movement of a trip lever 47 or energizing of coil 45 causes a latch 41 to move clear of a roller 28 whereby, under the action of opening spring 17, toggle links 24, 26 collapse upwards and a roller 31 at the knee of toggle links 26, 27 slips off a retaining prop 33 and comes to rest on a ram 32, the toggle 24, 26 being reset and relatched by 41 in the process. To reclose, the ram 32 is hydraulically raised and lifts the roller 31 against a resilient stop 36, the prop 33 then slipping under the roller 31 to retain it. The ram 32 forms part of a piston 8 the upper and lower faces of which communicate by pipes 97, 79, respectively, with a valve chamber having supply and exhaust pipes 82, 86, respectively. The movable element of the valve has lands 67...70 co-operating with transverse ports 72, 73, and can be actuated either manually or by an electromagnet 95 against spring-action 98. The spaces between the outer pairs of lands are shaped so that liquid emerging from the exhaust side of piston 8 into the valve casing sets up a pressure on the movable valve element to assist the motion means in rapidly moving it to its actuated position. To close, 'the element is moved to the left and admits liquid from pipe 82 to pipe 79, liquid above the piston 8 exhausting via pipe 97 into chamber 80 and acting on the land 68 to assist the leftwards movement of the element. When the breaker is fully closed, a limit switch de-energizes the electromagnet 95 and spring 98 restores the element to its right-hand position. Liquid is now supplied via 82 and 97 above the piston 8 to lower it, the liquid beneath it being exhausted via 79 and chamber 81, arid assisting the spring' 98 in moving the element. In both cases the exhaust liquid is returned via pipe 86 to a reservoir 60 whence it. is pumped by a motor pump 62 or hand pump 61 (which may be used for jacking up the piston 8) into a pneumohydraulic accumulator 50. The latter comprises a high-pressure shell 51 normally filled by a synthetic rubber bag 53 charged via valve 52 with dry nitrogen to two-thirds the desired operating pressure. The bag is held inside the shell by a valve 56, but when liquid (such as oil) is pumped into the shell, the bag is compressed to the normal operating pressure. The inlet chamber 83 may, alternatively, be adapted to accelerate the movement of the movable valve element.