Patent GB-477006-A (GB)
Title: Improvements in electric circuit breakers
IPC: H01H33/32
Filed: 1936-06-18
Abstract: 477,006. Liquid - blast switches. FLURSCHEIM, C. H., VANCE, W. G. C., DISBURY, E. R., and METROPOLITANVICKERS ELECTRICAL CO., Ltd. June 18, 1936, No. 17006. [Class 38 (v)] An oil-blast or impulse circuit-breaker has an operating arrangement comprising a power cylinder and piston, a compressed-air reservoir or supply, a trippable valve therebetween and means connecting the air-piston with both the moving contact and the oil piston in such manner that the latter is moved at a substantially uniform speed whilst the contact separates at a varying speed. The invention is applicable to the arrangements disclosed in Specifications 386,326, 435,143, and 441,734. As applied to the circuit-breaker of Fig. 2 of Specification 477,005, in which the insulating tube 9 operating the movable contact is provided with a collar 11 having guides 12 engaging pins 13 on the final member 14 of the operating mechanism, main and auxiliary air cylinders 1, 4 for opening and closing the breaker, respectively, are controlled by a valve 7 and by a valve in a casing 8, and provided with pistons 5, 6 linked at 16, 17 with a cam 18 rotatable on a shaft 19. Lever 14 is pivoted at 15, which may be a common shaft for the phases of a polyphase breaker, and carries a roller 23 engaging in a slot 20 in the cam 18. A toggle spring 25 is anchored between the pin of roller 23 and a fixed pin 26, and the piston 2 of the blast-pump 2, 3 is linked to the cam 18 by link 27. In opening circuit, 5 moves downwards, rotating 18 counterclockwise, so producing a continuous movement of the blast piston 2. The slot 20, however, is specially formed so that at the region 21-22 of its lefthand surface, roller 23 is engaged to drive the lever 14 positively, whereas after roller 23 passes point 22, by which time it has moved across the dead-centre line 15, 26, spring 25 completes the opening movement, which may be under the control of a dashpot arrangement as described in Specification 477,005. The right-hand side of slot 20 is shaped to provide positive reclosure, means as disclosed in Specification 477,005 being preferably provided to allow unimpeded return of piston 2. Instead of the right-hand surface of slot 20 being utilized to reclose, the cam 18 may have a peripheral surface, corresponding to that shown, for opening, and roller 23 may engage a slot in a link pivoted to cam 18, the slot-length allowing the spring 25 to " take over " and at the same time providing the positive closing force. Alternatively, a lever and linkage arrangement as disclosed in Specification 477,007 may be employed, as may also the means of that Specification for operating the valve 7 and that in chamber 8. The blast piston and piston 5 may be connected together within a common cylinder, as in Specification 477,005. The compressed-air reservoir may be formed by hollow parts of the supporting framework, and in a polyphase breaker of the character disclosed in Specification 435,419, may comprise tubes welded to the central earthed metal chambers, or a tube supporting the latter from below. The contacts of a polyphase switch may be coupled by a tension rod for joint operation by an opening and a closing piston respectively connected to the outer contacts, Fig. 2 (not shown). Other polyphase arrangements comprise a valve connecting a common air-piston with individual pumppistons and contact-actuating mechanisms, or connecting by individual air-pipes the valve with individual air-pistons.