Patent GB-375808-A (GB)
Title: Improvements relating to electric switches or circuit breakers
IPC: H01H33/985
Filed: 1931-03-30
Abstract: 375,808. High - tension switches. BRITISH ELECTRICAL & ALLIED INDUSTRIES RESEARCH ASSOCIATION, WHITNEY, W. B., WEDMORE, E. B., and CASSIE, A. M., 36, Kingsway, London. March 30, 1931, No. 9596. [Class 38 (v).] Arc-rupturing devices; pneumatic blow-outs.-In switches of the general character in which fluid is put in motion in the neighbourhood of the arc to assist in interrupting the arc, as set out, for example, in Specification 366,998, the range of current values over which interruption can be satisfactorily effected is extended by providing means for automatically varying the cross-sectional area of the outlets for arc products in accordance with the current or are energy. In general, the outlets are normally adjusted for the minimum current the switch is likely to be called upon to rupture, so that an effective blast is set up with the small pressure available, the outlets being enlarged by the current or fluid pressure set up by shortcircuit arcs so as to limit the rise in pressure. Fig. 1 shows the invention applied to a baffle plate as used in Fig. 1 of Specification 366,998. The outer part 1 is fixed and the inner flexible part 2 is reduced at 3 to provide a hinge such that pressure set up by the arc in the chamber 5 can separate the jaws 2a, 2b of the plate 2 to vary the area of the outlet 6 in accordance with the pressure. The restoring force of the elasticity of the member 2 may be supplemented by springs 7, or the latter may be used alone in conjunction with an ordinary hinge at 3. Alternatively, the outlet 6 may be of maximum area and blocked up by a wedge member so as to give an effective minimum area, pressure acting on the wedge against spring action to drive it out of, and enlarge, the outlet. In Figs. 4, 5 a pile of plates is made up of parts 2a, 2b alternating with parts 14a, 14b with securing rods 10, 12 such that the parts 2b, 14b are fixed. The parts 2a, 14a are movable as a body about a hinge pin 11 against the action of a spring 13 to vary the outlet 6. Such a structure is placed in a container of the kind shown in Specification 366,998, to which Specification the form shown in Fig. 7 is also applicable. The pile of plates 2 alternated with baffles is mounted to rotate as a body on ball bearings 18 and is normally held by spiral spring 19 so that the passages 6 in the plates 2 and the outlet 6a are out of register but for the small part 21. Pressure causes the body to rotate about the axis 17 to enlarge the part 21 to the necessary extent. In Fig. 8, the arc current flowing through a solenoid 31 acts on an arm 29 secured to a spring- controlled valve 22 to rotate it about an axis 25 and enlarge the openings 27, 28 leading from the chamber 5 to the outlets 6, 6a. Alternatively, the valve may be a vertically-reciprocable slotted member which is moved by a solenoid to vary the degree of register between the slots in the valve and the outlets. Fig. 14 shows the invention applied to the outlets of explosion pots of oil-switches, the members 34 being movable radially outwards against the action of springs 35 to admit the movable contact and having surfaces on which the oil-pressure acts to move them radially in like manner, the degree of movement depending on the pressure. The plates 37 are secured one to each member 34 and slide in slots in the adjacent members so as to prevent leakage of arc products between the members 34. The Specification also outlines other modifications in details. The Provisional Specification states also that the outlet from an explosion pot may be constituted by the inner convolution of a spiral of metal which spreads out under the arc pressure.