Patent GB-450405-A (GB)
Title: Improvements in or relating to electric circuit-breakers
IPC: H01H33/75
Filed: 1935-01-16
Abstract: 450,405. Liquid - blast 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. Jan. 16, 1935, No. 1452. [Class 38 (v)] In liquid-insulated A.C. circuitbreakers of the kind in which the movable contact is drawn through an enclosure in an arc control device in which a relatively high pressure is produced by the arc so that the compressed liquid, vapour, and gas in the enclosure constitutes a deionizing fluid or blast which forces the ionized arc gases through vents in the enclosure which are laterally disposed with respect to the arc path, the part of the enclosure-wall in the vicinity of the vents (or some of them) is formed in one or more parts separate, and readily removable, from the rest of the structure. The enclosure A<1> is formed in a cylindrical moulded insulating block A, in the side of which are formed a series of apertures A<2> of rectangular section which are tapered at A<3> to receive the removable vent members C of fibre or other insulating material having grooves C<1> constituting the vents. A separate throat member D of fibre or other insulating material has a series of holes D' constituting the vent throats, and is removably received in a groove formed in the block A and by projections C<2> on the members C. The vents C<1> may all be radially directed from the axis of the movable contact B, or, as shown, may be offset, in which case they are preferably alternately oppositely directed, so that the reactive forces on the structure are partly eliminated, and in double-break switches a better distribution of arc products in the ambient liquid is obtained. The block A is mounted in an outer tube E of, for example, varnished paper which is provided with lateral outlets E<1> or a continuous slot or slots for the blast. The upper end carries one element E<2> of a bayonet joint, the other F<2> of which is supported by the bushing F, and a latch E<3> retains the parts in place. The movable contact B enters the enclosure through a throat washer G loosely mounted between a ring E<5> and end plates E<6>. Instead of the rod contact B shown, a flat bar with rounded edges may be employed, and in either case a renewable tip may be fitted. Magnetic means as disclosed in Specifications 435,250 and 435,308 may be employed to deflect the arc into, and seal, the throats D<3>, the means shown comprising laminµ H of magnetic material embedded or moulded in the block A. Since the remaining vents are also substantially closed by contact B, a high pressure is set up by the arc when it is formed in the enclosure A<1>, which pressure acts at the non-arcing period, that is, the zero of the cycle, to force the gases and fluid through the open vents. By varying the size of the vents or their number, as by providing plates C without vents, a single size of block and main structure may be added to a range of switchratings. Pockets for retaining liquid near the arc may be provided in the form of grooves in the enclosure-wall, one diametrically opposite each vent. Fig. 7 shows a modified structure comprising side members J, J<1> and baffles J<2> supported in J, J<1> by means of their edges J<3> so that inwardly tapering spaces C<3> constitute the vents. The outer faces have keyways J<4>, J<5> co-operating with keys in the block, which is cut away at one side snugly to receive the structure which narrows towards the periphery so as to resist outward movement due to the arc-pressure. The vent structure can alternatively be moulded in a single block. In Figs. 9, 10, the block is made up of alternately arranged circular plates and plates L having cut-away parts to receive the vent members C. Fig. 10 shows a form of removable oil-retaining member M, having oil pockets M<1> cut in a block of fibre or mouldable insulation, and defining with the throat-member D an arcing enclosure. Such a member M can be fitted to the other forms shown. The lateral outlets in the casing E may in all forms be replaced by a longitudinal passage discharging at the top and/or bottom of the structure, a suitable passage being formed by cutting the side of the block flat near the vents. The uppermost vent may be set back a little so as to reduce the pressure in the enclosure when closing the breaker, or alternatively the seep hole F<3> may be made sufficiently large for this purpose. The main block A may be of fibre, in which case the enclosure A<1> may be machined, vent members may be dispensed with by drilling vents in the block, and a groove may be cut to receive the removable throat member. Other materials for the block and vent and throat members are products having an asbestos base, as sindanyo, vitreous materials, as porcelain, and natural insulating materials as slate or a hardwood. The block may be alternatively of a phenol-formaldehyde or thio-urea product, such as the substances known under the Registered Trade Marks "Bakelite" and " Beetle." Specification 366,998 also is referred to. The Provisional Specification states also that, where baffle plates are employed, they may be resiliently clamped together to relieve excess pressures, for example, where the clamping is by means of longitudinal bolts, the latter may have spring washers.