Patent GB-516238-A (GB)
Title: Improvements in or relating to electric circuit-breaking devices of the gas-blast type
IPC: H01H33/74
Filed: 1938-06-22
Abstract: 516,238. Gas-blast switches. REYROLLE & CO., Ltd., A., COATES, F., LEESON, B. H., and ALLAN, A. June 22, 1938, Nos. 18548/38, and 16269/39. [Class 38 (v)] In a gas-blast switch in which the arc is drawn out within an enclosure past one or more lateral vents in the wall thereof, and a second arc in series with the main arc sets up a pressure which forces the blast through the arc and out from the enclosure through the vents, a member constituted by one of the relatively movable contact-members of the main break, or by a part associated therewith is arranged to act as a valve for controlling the blast. The generation of the blast may be aided by disposing in proximity to the series arc, fibre, boron, or other insulating material which gives off gas when acted upon by the arc. Preferably the vent throats are so small, and the arc is drawn in such close proximity thereto, that all the gas discharged through the vents must pass through the arc path. The positioning of the arc may be assisted by magnetic inserts in the enclosure body and by placing the main and series breaks so as to form a current loop acting electrodynamically on the main arc. as well as by arranging the arcing tips against the vents, and by providing in the enclosure a narrow slot from which the vents extend. The movable main or series contact may be withdrawn completely from the enclosure into insulating liquid or clean gas, or the enclosure may be placed in a pressure-gas casing and the discharge led directly by way of a contactoperated valve to the outside. In Fig. 1, the main fixed and movable rod contact A, C separate in an enclosure B in an insulating structure comprising blocks B' secured together by lateral bolts B<2> and having registering grooves cut in their engaging faces to form lateral vents B' and a port, or ports, B' to which is connected the gas - supply pipe B<5> from the adjacent chamber E containing the series-break E<1>, E<3>. The contacts C, E<3> are electrically connected through sliding contacts C<3>, E<5> and plate C<1> and are insulated at C<4>, E<6> from the operating mechanism, which comprises pivoted cranks F<1>, F<2>, links F<5>, F<6>, and a link F', the arrangement being such that the series break opens first and a valve B<6> is opened at once to admit the gas-pressure to the enclosure B. The blast is controlled by the contact C acting as a valve which initially closes the vents B<3> and port B'. The vents may be radially arranged with respect to the arc, or they may be offset and straight or curved so as to discharge on either side of the central plane of the ports and vent throats. In Fig. 2, the enclosure B and chamber E are in the same structure in which the pipe B<@> is formed as a duct. The rod E' is lowered by the operating mechanism to draw the series arc and when adequate pressure is developed, the movable contact G is raised by means of its piston G' against the action of spring G<3>, and acts as a valve to control the blast through the vents B<3>. In Fig. 3 the vents H<2> and ports H' are formed by slots in alternate plates H of a stack, and the valve is formed by a separate member H<5> operated by a spring H<6> and normally held closed by a projection H' on the movable contact C. The ports H' communicate with the supply pipe B<5> over a passage H' formed by aligned holes in the stack, no valve B<6> being provided. This arrangement may be modified, Fig. 4 (not shown), by dispensing with the ports and admitting the blast into the enclosure through a hollow movable contact which acts as the valve and is apertured so as to communicate with a container which surrounds the contact C' and receives the end of the gas-supply pipe from the series break. The aperture is normally closed but opens at the moment the contact moves. This arrangement may be modified by maintaining communication between the pipe and hollow contact and placing a depending plug in the enclosure so as to close the hollow contact when the breaker is closed. In Fig. 6, the enclosure B and chamber E are in the same structure, as in Fig. 2, and a further isolating gap L', L<2> is provided in an adjacent chamber L and operated so as to open after the series and main breaks. The main break is effected by movement of the insulating structure, the contact G of the main break being fixed to the top plate of the casing D. This movement is effected by a rod K and lever K' from a yoke K<2> operated by a cam K<3> on the shaft F' which carries the crank arm F<1> operating the contact E'. Blast-control is effected by a valve K<4> which is placed in the duct B<5> and fixed to the top plate of casing D so as to be opened by downward movement of the structure. The chamber L may contain liquid or compressed gas, such as air, nitrogen, carbon dioxide, argon, or difluoro-dichloro-methane, or other fluorinated alkyl chloride. In Fig. 7, the main contacts N, A separate in a structure comprising an insulating tube M, with a lateral opening M', and one or more annular insulating plates M<2> closely surrounding the movable contact and provided with a passage M<3> co-operating with the opening M' and a gas-inlet passage M' leading into a space M'. Contact N carries a piston N<3> which slides in a cylinder N<2> in metal casing N<1> and is normally urged upwards by a spring N' to bring a surface N<5> thereon against a valve-seating N" and shut off the enclosure B. A stop N<7> limits the downward movement of N to the position shown, which is the most favourable for arc-extinction, and an extension of the contact engages a ring contact N<8>. The cylinder N<2> communicates with an insulating casing O in which is supported by brackets O<6> a further insulating chamber O<1> in which the series break occurs between O<2>, O<3>. The chamber O is closed by the extension O<5>. The movable contact O<3> passes through a ring contact O<4> to provide an adequate isolating gap. Instead of being operated by the gas-pressure, the contact N may be mechanically operated to separate after the series break, Fig. 8 (not shown). The casing D may have discharge outlets opposite the vents and leading into a surrounding casing, the discharge-part of which is separated from upper and lower parts containing compressed gas, insulating compound, or pulverulent solid insulations such as magnesia.