Patent GB-435250-A (GB)
Title: Improvements in or relating to electric circuit-breakers
IPC: H01H33/18
Filed: 1933-12-18
Abstract: 435,250. Liquid-break switches; arcrupturing in switches. REYROLLE & CO., Ltd., A., Hebburn-on-Tyne, LEESON, B. H., Waverley, Tynemouth, and WILD, R. W., 33, Oakwood Avenue, Harlow Green, Low Fell, Co. Durham. Dec. 18, 1933, Nos. 35635 /33 and 1426 /35. [Class 38 (v)] In a liquid-break A.C. switch of the kind wherein the movable contact is drawn through an enclosure in which a high pressure is set up by the arc, so that the compressed liquid, vapour and/or gas in the enclosure constitutes a deionizing fluid or blast which forces the ionized gases through vents which are arranged laterally of the arc path, the moving contact in the closed position substantially closes some or all of the lateral vents, and means is provided whereby the arc is magnetically deflected towards or into the throats of the vents, so that the vents opened by withdrawal of the movable contact are virtually sealed during the arcing period. The pressure within the enclosure thereby increases very rapidly until, when the arc ceases at zero of the cycle, the fluid is forced under high pressure towards and through the vents, so that it mixes with the ionized gases and forces them through the vents. In Figs. 1, 2, a stack of insulating baffles of the character disclosed in Specification 366,998, comprises plates B alternating with plates B<1> having radial slots B<2> extending from the central apertures to the periphery and arranged in vertical alignment. The central holes are enlarged on the side of the movable contact D opposite to the slots and vary in size to provide oil pockets. The structure is secured between the top-plate A and a metal plate F by means of bolts E .. E<3> with insulating sleeves, the bolts E, E<1> on either side of the vents B<2> being in conducting connection with A, whereas E<2>, E<3> are insulated by plates H<1>. The fixed contact C is mounted on a metal ring G which is insulated at H from the top-plate A and connected by insulated bolts J with the bolts E<2>, E<3>, whereby in operation the current traverses the loop shown by the arrows in Fig. 1 and sets up a magnetic field which holds the arc in the vent throats when the circuit is being opened. The vents are thus sealed by the arc, and the sealing action is aided by making the movable contact D keep as close as possible to the rounded corners B<3> of the slots. A shrouding ring F<3> is provided for keeping an external arc from the plate F, and an adjustable washer F<1>, apertured at F<2> just to take the contact D, closes the bottom of the enclosure. To avoid a permanent conducting loop, the bolts E<2>, E3 may terminate in a conducting ring, which carries arcing contacts and is insulated from the topplate A on which the main fixed contact is directly mounted, Fig. 3 (not shown). Alternatively, instead of utilizing the bolts and plate F, a separate structure of similar configuration outside the enclosure may serve as a loop, Figs. 4, 5 (not shown). In Figs. 6, 7, the field is set up by horse-shoe shaped laminµ B<7> of magnetic material located in cut-away parts of plates B<5> sandwiched between plates B<4>, B<6>. Each group B<4> . . B<6> is interleaved with a slotted plate B<1> as described with reference to Fig. 1, and has the central holes shaped at B<8> to surround closely a large part of contact D. The top and bottom plates R, R<1> and bolts S clamp between them a metal ring T having an annular recess T<1> and slots leading therefrom, so as to form with lugs O<1> on the fixed-contact carrier O a bayonet connection. A catch T<2> prevents inadvertent rotation and detachment of the baffle-structure. In Fig. 9 the slots B<10> are offset and preferably are alternately oppositely directed, and the unvented plates, corresponding to those B<4> . . B<6> in Fig. 6, are formed at B" to fit closely about the bar-like contact D<1>. The latter is engaged on each side by three spring-mounted contact blocks C<3>, of which the one nearest the vents is extended downwards to co-operate with a renewable upstanding tip D3 on D<1>, whereby the arc is formed next the vents. Fig. 12 shows a renewable fibre liner W for the enclosure, having a series of oil-pockets W and shoulders W<2> abutting similar shoulders on the disc apertures. The liner can be detached without dismantling the structure, and may have the size and shape of its pockets varied to suit different operating conditions. In Fig. 13, a fixed contact structure as shown in Fig. 6 is combined with a baffle structure as shown in Fig. 9, but the baffle plates are cut to a straight edge X<3>, so forming a segment-shaped flue X<2> into which the vents B<10> open. In this form, as in others where complete sealing of the vents occurs, excessive pressures due to rupturing very heavy loads can be relieved by compressing the baffle-structure by means of, for example, dished springy rings Z between the clamping ring Y<1> and throat washer F<7>. The relief orifices may be longitudinally or laterally arranged in the casing X or may comprise the flues X<2>, and the relief springs may be arranged on the clamping bolts, where such are used. Other modifications refer to the non-sealing by the movable contact of the topmost vent and to the enlargement of the normal seep-hole, whereby the pressure in the enclosure is not large enough to make closure difficult ; the arrangement of oppositely-directed radial vents or of offset vents coplanar with the fixed contacts and movable bridge-contact ; the employment of laminµ embedded in baffle plates, or of the clamping bolts adjacent the vents as magnetic members ; a combination of the two methods, current loop and magnetic members ; and the use of varying vent areas, as disclosed in Specification 421,552, for extinquishing lowcurrent arcs. Certain forms of the present invention utilize the invention of Specification 421,552. Specification and 435,308 also is referred to.