Patent GB-466427-A (GB)
Title: Improvements in liquid break circuit breakers
IPC: H01H33/92
Filed: 1935-11-28
Abstract: 466,427. Liquid-blast switches. BRITISH THOMSON-HOUSTON CO., Ltd., TRENCHAM, H., and COX, H. E. Nov. 28, 1935, No. 541. [Class 38 (v)] A circuit-breaker of the impulse-type has the moving contact withdrawn from engagement with the fixed contact through an aperture formed in a pair of spaced transverse members, the space between which forms a passageway into which the insulating liquid is forced by the piston during the circuit-opening movement, a separate vent being provided in or adjacent the fixed contact for permitting escape of gas from its vicinity, whereby the tendency to build up back-pressure against the piston is avoided. The oil-casing 1 has insulators 2, 5 supporting the housing 3 containing the fixed contact 4, and an insulator 7 supporting a contact 6 with which the movable-rod contact 8 is in sliding engagement. A cylindrical part 11 of housing 3 is open at the right-hand end and within it is reciprocable a piston 12 on a rod 13. The housing 3 and part 11 are closed by a pair of insulating plates 14, 15 which have an aperture 16 to admit contact 8 and are spaced apart to provide a passage 17 communicating via aperture 18 with the interior of 11. When 8 is moved to the left to open circuit, piston 12 moves simultaneously in the same direction and forces a stream of oil through passage 17 across the arc. A venting passage 20 adjacent the removable arcing tip 19 of contact 4 allows the gas-bubble to escape to the right-hand face of piston 12, so compensating for the effect of the back-pressure of the bubble on the oil stream. The piston 12 may alternatively be arranged below the contact 4 so that the stream is directed vertically upwards, and space 20 may exhaust into an expansion chamber which is situated on the top of housing 3 and mainly above the oil-level, and has a bleed hole to allow escape of gas and return of oil to the housing 3, Fig. 2 (not shown). In two arrangements in which the contact separation and piston stroke are effected in a vertical direction, the space 20 may communicate with a passage in the wall of the housing 3 adjacent to it, Fig. 3 (not shown), or the fixed contact may be hollow to permit the escape of gas, Fig. 4 (not shown). Actuating.-An operating shaft 21 carries an arm 22 which is adjustably linked at 23 to a lever 24. The latter is pivoted to a lever 25 having a fixed pivot 26 in a cross-bar 29 and a pivotal connection with a lever 27 pivoted at 28 to the rod 8. The upper end of 24 is pivoted to rod 13 and lever 27 also has a pivotal and sliding connection at 30 with the cross-bar 29. Rotation of 21 anticlockwise to the position shown has extended the spring 32 biassing the piston to the left, and further anticlockwise rotation causes lever 24 to rotate 25 anticlockwise about 26 and thereby to rotate 27 clockwise, so sliding 30 along the bar 29, stressing the contact-opening spring 33, and closing the contact 8. The parts are retained by the links 22, 23 moving into a slightly overset position. Reverse rotation of 21 causes the contact 8 and piston 12 to be retracted by their several springs.