Patent GB-518314-A (GB)
Title: Improvements in or relating to electric circuit-breakers having arc-control devices
IPC: H01H33/75
Filed: 1938-08-22
Abstract: 518,314. Liquid-blast switches. REYROLLE & CO., Ltd., A., and WILD, R. W. Aug. 12, 1938, No. 24602. [Class 38 (v)] A liquid-insulated A.C. switch has one or more arc-control devices each comprising an insulating enclosure having lateral vents and surrounding a single set of co-operating contacts and within which enclosure a high pressure is generated during the arcing-period by the arc drawn by the contact-separating movement. A blast of deionizing fluid is thereby discharged at zerocurrent through the arc path and lateral vents and out of the enclosure. The interior of each device is in communication with a resilient energy-storing device which acts to absorb some of the pressure-energy developed during the arcing period (thus relieving impact-pressure due to rupturing heavy currents) and to release such energy during zero-current so as to assist the blast of deionizing fluid out of the enclosure. The arc-control devices may be of the character described in Specifications 435,250, 435,308, 452,146 and 460,219. In Fig. 1, the arcing enclosures D are placed around the arcing contacts of each phase of a double-break arrangement, the movable bridging-member C of which has contact surfaces C<2> co-operating with main fixed contacts E'. The fixed arcing contact E enters the enclosure D through an aperture in the top and engages movable contacts mounted on the bridging-member C by spring fingers D<2>, the contacts being arranged so that the arc is drawn out close to, so as to seal, the aligned throats of the lateral vents D' which are themselves alternately offset from the plane of the longitudinal axis of the enclosure. Positioning of the arc in this way may be effected by arcing tips assisted by the current-loop and magnetic inserts D<5>, and the contact E may occupy a recess in the enclosure along the line of vent throats. Each device D has an opening F<1> communicating with the energy-storing device over the passages F<2> in member C. The device may comprise an air-chamber formed in the operating rod or carried by the member C, but, as shown, comprises a spring-loaded piston F in a cylinder F', the passage F<2> being so formed that a gastrap is formed beneath the piston F. Alternatively, Fig. 3 (not shown), a gas trap may be formed in a tubular bridging-member, the movable contacts being constituted by hollow, upwardly-directed extensions of the member and being adapted to enter, from below, arcing enclosures attached to lead-in conductors. Instead of providing a common energy-storing device for the two (or more) breaks of a single phase switch, or of each phase of a polyphase switch, an independent device may be provided for each break. Thus, in Fig. 4, a stack of insulating plates is slotted to provide, in addition to the vents H<1> and central arcing space, a closed chamber H' communicating with the latter space at a point opposite to the vent throats. In a modification, Fig. 6 (not shown), the enclosure has a domed cover communicating with the arcing space by way of a perforated plate. Alternativly, Fig. 9, the enclosure-wall K is apertured radially at K' opposite the vents K' to receive pistons K<2> urged inwardly by springs K<3> and/or gas-cushions. In Fig. 10, the enclosure L communicates through the fixed contact L' with a chamber M constituted by a metal bellows which can expand against a spring M<2> and air-cushion within the dome L<2>. A vent tube M' allows oil to enter the bellows until pressure-balance is achieved. Alternatively, a sealed bellows may be carried by, and within, the dome, Fig. 11 (not shown).