Patent GB-516529-A (GB)
Title: Improvements in or relating to electric circuit-breaking devices of the gas-blast type
IPC: H01H33/98
Filed: 1938-06-21
Abstract: 516,529. Fluid-blast switches. REYROLLE & CO., Ltd., A, COATES, F., LEESON, B. H., and ALLAN, A. June 21, 1938, No. 18386. [Class 38 (v)] The arc formed on opening the circuit is drawn across a lateral discharge vent (or a group of vents having aligned throats) in the wall of an enclosure within which the arc is formed, and is forced through such vents by a blast of deionizing gas under pressure supplied to the enclosure through one or more openings in the wall opposite the vents, and the latter are of such size and the arc is drawn in such close proximity thereto, that substantially all the gas discharged through the vents must pass through the arc path. The gas may be air, nitrogen, carbon dioxide, argon or gaseous fluorinated alkyl chloride such as difluorodichloro-methane. In Fig. 1, the fixed contact A with arcing-tip A<2> is in a metal housing A' in an insulating structure comprising a stack of plates B', secured by bolts B<2>, and certain plates being provided with vents B' extending from the central opening. The movable contact rod C is a close fit in the latter and may have an arcing-tip co-operating with A<2> to form the arc adjacent the vents B<3>. The rod C slides in a contact C' to which is attached a lead C‹ arranged to form with C a current-loop to force the arc electrodynamically against the vents, which action may be reinforced or replaced by that of magnetic inserts in certain of the plates. The rod C is in two parts separated by insulation C<4> and may, in the open position, move clear of the structure and into a body of clean gas or liquid, or a separate isolating break may be arranged alongside the main break to act electrodynamically thereon. In the former case gas is prevented from leaking by arranging in the discharge tube D<1> a valve which is opened for the switching operation in order to eliminate back-pressure. The gas-supply pipe G opens directly into the container F<3> acting as a reservoir and above the valve E<2> leads into the structure by way of aligned holes B<4> in the plate B<1>. The rod C may act as a valve controlling the delivery of blast-gas from the ports to the vents by progressively opening either or both of the latter. The vents may be in vertical alignment with one another or may be offset on either side alternately, or they may be arranged in the manner shown at G' in Fig. 8. Fig. 5 shows another structure comprising a pair of blocks H secured face-to-face by bolts H<1> and having registering grooves to form vents H<2>, H<3> and a port or ports H<4>, H<5>, but a further, and horizontal, vent may be provided between those shown. A slot H‹ adjacent the vent-throats ensures proper positioning of the arc in those throats, the slot being of such size that it will be filled by the arc. The slot may extend down the full length of the structure to receive an arcing projection on the rod C, or the latter may be a flat bar filling the slot. The gas-blast may be obtained by the means described in Specification 516,532. The structure D may exhaust into an outer casing N<1>, Fig. 8 by way of vents N located to provide a tortuous path for the escaping blast at N<2>. Transverse annular plates in the casing N' separate the exhaust-space from the remainder, which may contain insulating compound, compressed-gas, or pulverulent material such as magnesia. The lead-in conductors are arranged at right-angles to the movable contact-rod to provide a current-loop for forcing the arc against the vents G<7>. Circuit may be opened by moving the arcing structure and fixing the " movable " contact, or the movable contact may carry a pneumatically-actuated piston. The gas-pressure may also act on a piston on the movable contact to produce opening of the switch. Specification 516,530 is also referred to. The Provisional Specification describes a form employing a tubular blast-conveying contact, there being no other blast-opening.