Patent GB-796581-A (GB)
Title: Improvements in and relating to electric circuit-breakers of the gas-blast type
Inventor: BOLTON ERIC
IPC: H01H33/32
Filed: 1954-03-02
Abstract: 796,581. Air-break switches. ENGLISH ELECTRIC CO., Ltd. Feb. 25, 1955 [March 2, 1954], No. 6066/54. Class 38 (5). The contacts 9, 11 of an air-blast circuitbreaker are mounted in a compressed-air container 2 and separated in two stages with an interval between them, the first constituting the interrupting movement, the interval ensuring quenching of the arc, and the second constituting the isolating movement. The movable contact 11 is actuated by rotation of an axially-movable hollow insulator 8, supplying compressed air to the container, which causes the piston 25 of valve 26 to move to the right and thus exhaust air from the left-hand side of a piston 13 and supply compressed air to the right-hand side, which causes piston 13 to move to the left, until it strikes an auxiliary piston 15, and separate contacts 9, 11. Movement of the piston 25 also exhausts the lower side of piston 32 of an exhaust valve 7, causing the valve to open to atmosphere, thus producing an arc-quenching blast across the contacts. The space to the left of piston 15 is normally at the same pressure as container 2 but as the air between pistons 13 and 15 is exhausted, the air on the left of piston 15 exhausts through a bleed hole-35 so that after an interval both pistons 13 and 15 move to the left against spring 16 and cause the second, isolating, movement of contacts 11, 9. As soon as this movement commences a valve 29 is closed through a forked link 27 between it and contact 11, so that pressure on the lower side of piston 32 builds up through a bleed hole 36 and the exhaust valve 7 closes. To close the breaker, the rod 8 is rotated to return piston 25 of valve 26 to its original position when piston 13 closes the contacts, the valve 29 being re-opened through link 27 towards the end of the stroke. In another embodiment (Fig. 4), two interrupting units are mounted on one receiver (Fig. 3), and the contacts are separated by admitting air to a primary actuating cylinder 53, the piston of which acts on the hollow rotatable insulator 54, which acts through a link on the upper end of a lever 55, the lower end of which is temporarily held stationary by links 56, 57 connecting it to the moving contact, so that the upper seating of a valve 47 is opened through a link 58 and a crank-plate 59. The upper portion of a cylinder 44 is thus vented to atmosphere so that the compressed air in receiver 40 causes main piston 45 to move upwards until arrested by an auxiliary piston 46 as before. Valve 47 engages its lower seating before the piston of cylinder 53 has completed its travel and initially acts as a stop to prevent further movement of the piston, but once the contacts separate, links 56, 57 drive the lower end of lever 55 to the left, the piston then moving again and thus indicating the movement of the contacts. The exhaust valves (not shown) may each be controlled by a pilot valve as before. Thus, during opening of the breaker the contact driving links 52 rotate counter-clockwise round shaft 61 and the toggle 52, 52a causes contacts 49, 49a to make a small upward movement together which is used to open a pilot valve and thus the exhaust valve. Specification 796,582 is referred to.