Patent GB-403235-A (GB)
Title: Improvements relating to electrical circuit breakers
IPC: H01H33/98
Filed: 1932-07-01
Abstract: 403,235. Arc-rupturing in switches; high-tension switches. BRITISH ELECTRICAL & ALLIED INDUSTRIES RESEARCH ASSOCIATION, WHITNEY, W. B., and WEDMORE, E. B., 36, Kingsway, London. July 1, 1932, Nos. 1559/33 (divided on 389,882), 1586/33 (divided on 394,560), and 1693/33. [Class 38 (v).] A circuit-breaker has relatively movable electrodes so arranged in a pressure-resisting enclosure that, during opening, arcing may occur in two or more successive stages, the enclosure having an outlet or a number of closely spaced outlets immediately adjacent the arc gap formed during the first stage of arcing and through which the products of arcing can escape. If arcing should occur at a later stage, substantially all the deionizing fluid which is set in motion by that later stage is driven through a walled passage longer than the direct path between the successive stages of arcing and across the path of the earlier stage and out through the outlet or outlets. The deionizing fluid may be a liquid, vapour, or gas. The invention is described in connection with Fig. 1 of Specification 389,882 and Figs. 9-11 of Specification 394,560 [without, however, supplying the lower gate of that Figure]. In Fig. 2, metal cylinders 17, 18 are arranged as shown to leave a space between them for oil or other fluid, and the outer cylinder has an outlet 22 serving as the fixed contact and formed with a deflector 24 for the arc products. An intermediate contact 25 is urged by a spring 26 to follow the movable contact 11 when the latter is lowered to open the circuit, so striking an arc between it and the contact 22, which arc is subsequently transferred to the cylinder 18. When contact 11 leaves the contact-members 7 on the intermediate contact, an arc is struck in chamber 18 (provided the original arc in chamber 17 is not extinguished), the pressure of which acts through openings 19 and drives the oil located between the two chambers across the original arc and out of the outlet 22. This action may be assisted by an annular spring- restored piston 28 and the outlet 22 may have a cooling grid for the discharged gases. Numerical data as to the speed of electrode movement are given. When used with oil or other insulating liquid, or with air, the chamber 18 may carry cooling and deionizing baffles of copper or fibre, the baffles serving in the latter case to confine the arc to the centre of the chamber and protect the walls. When used with a gas which it is desired to conserve, the whole may be enclosed in a gas-tight enclosure, or the base of the chamber 17 may be made gas-tight and the outlet 22 may exhaust into a large closed receiver. Fig. 3 shows a form using a "straightthrough" stroke of contact 11, with a pair of gates 30 arranged to close over that contact and fingers 7 arranged to provide a suitable delay before the second arc is formed between them and contact 11. In Fig. 4, fixed contacts 39 are mounted in a metal case 36a on flexible springs 40 which permit the contacts to abut on one another when the contact 11 is withdrawn and the pressure subsides. Contacts 39a on perforated springs 40a are mounted in an insulating case 36 and arranged to close and be latched when contact 11 is withdrawn, thus causing the arc products to escape through the fine holes in the springs 40a or through passages in the case 36. Insulating blocks 39b are mounted on perforated springs 40b and likewise arranged to abut on one another when the pressure beneath them subsides. By arranging for current to be led up the springs 40, 40a, a magnetic field may be set up for retaining the arc in the centre of the case. The blocks 39b may, alternatively, be replaced by hinged or resilient insulating members arranged to close over the withdrawn movable contact but to leave a small passage for the arc. In another form, Fig. 6 (not shown), the bridge-member is U-shaped and hollow, each limb constituting a contact arranged in an explosion chamber, one contact separating before the other and arranged adjacent an outlet. The later-breaking contact sets up a pressure to drive oil through the hollow bridge-member across the carlier-formed arc and out of the outlet.