Patent GB-428071-A (GB)
Title: Improvements in or relating to electrical circuit breakers
IPC: H01H33/92
Filed: 1933-11-06
Abstract: 428,071. High - tension switches. BRITISH ELECTRICAL & ALLIED INDUSTRIES RESEARCH ASSOCIATION, and WHITNEY, W. B., 15, Savoy Street, Strand, London. Nov. 6, 1933, Nos. 30808/33 and 15937/34. [Class 38 (v)] A circuit - interrupter has a casing surrounding the movable electrode and mounted to move with lost-motion on that electrode so that, during the first part of the opening movement, the arcing surface of the movable electrode moves towards or into the casing and a stream of extinguishing fluid (gas, vapour, liquid, or atomized spray) is caused to escape from the casing-interior across the arcing surface and then to flow with the arc products away from the arc path. The arrangement is such that the casing moves with the movable electrode after completion of the first part of the opening movement. In Figs. 2, 3, the fixed contact structure comprises four contacts of which all except 3<1> have fibre or other insulating tips 13, so that in opening circuit, the arc becomes rooted on 3<1>. The movable contact 7, which may have a hard wood or other insulating extension 14 formed with notches 15 for retaining fluid near the arc, is surrounded by a close-fitting cylindrical sleeve 6 of fibre or oil-absorbent material such as hard wood, which sleeve is normally urged by a spring 10 against the contacts 3 or other abutment. A series of vents 8 for arc products open out of a slot 16 in the sleeve, which may be recessed on either side of the slot in order to retain fluid in the neighbourhood of the arc drawn into the slot 16. When moving from the closed position (Fig. 2), a stop 17 on the contact 7 moves down a slot 18 in the sleeve 6 until it engages a screw 19 (Fig. 3) and so causes the sleeve to move with the contact. The arc should be extinguished before the sleeve leaves the fingers 3, but if this does not occur, a plain break occurs between them and inside the sleeve the arc is drawn in what is actually a baffle structure formed by the vents 8. The fingers 3 can be kept short by providing a hollow support for them and a hollow insulator to house the extension 14 in closed position. The vents 8 may be made wider or narrower in the opening direction, and the slot 16 may be closed at the top by a metal plate so as not to detract from the lateral blast through the vents by permitting escape of arc products in that direction. The slot 18 and stop 17 may serve as, respectively, a cylinder and piston for forcing fluid through a passage in the contact 7 opening into the slot 16 at its upper end, Fig. 5 (not shown). In Fig. 8, fluid is forced through the operating rod 39, cross-bar 40, and ports 41 into the sleeve 6, which has an insulating shell 22 turned over at 23 to form an annular slit 25 communicating through ports 24 with the interior of 6. When the contact 7, in opening, unseals the outlet from the slit 25, an annular jet is projected over the renewable tip 7a and forms an insulating barrier which is complete at current-zero. At the position shown, the stop 17 is about to move the sleeve from the contacts 3, 3<1>. In moving from the closed position, Fig. 11, a piston 32 on the contact 7 drives fluid from the metal sleeve 6 into the hollow contact 7 by way of ports 31. As the ports 30 are sealed by the contact 3, the fluid forces down a piston 34 in the bore 33 of the contact until the ports 30 come level with the arc space 37 in the insulating end 44 of the sleeve 6. The spring 35 then raises the piston 34 and drives the fluid through ports 30, into space 37, and over the contact tip, the volume of fluid being made adequate to produce a flow lasting a full A.C. cycle. In Fig. 9, the only outlet from sleeve 6 is at the top 27 and the interior has annular ribs 42 to retain fluid. In Fig. 10, (not shown), the internal diameter of the sleeve progressively diminishes to a minimum about midway of its length, the sleeve is provided with a special abutment, and the contact 7 has no extension. In the case of circuit interrupters to be used as rectifiers, the movable electrode 7 is reciprocated to make and break circuit during alternate half cycles of the alternating current.