Patent GB-392926-A (GB)
Title: Improvements in electrical switches or circuit breakers
IPC: B23D49/00
Filed: 1931-11-18
Abstract: 392,926. Heavy-current switches. WHITEHEAD, G. E. and WHITEHEAD'S ELECTRICAL INVENTIONS, Ltd., 38, Rhiwbina Hill, Rhiwbina, near Cardiff. Nov. 18, 1931, Nos. 32025/31 and 17535/32. [Class 38 (v).] In switches in which a fluid blast between the contacts is produced on their separation contact is broken within a metal housing or arcing chamber enclosing the actual contacting surfaces and arranged with an entry mouth and at least one moderately restricted opening through which the fluid can escape, the housing being further so arranged that before, at, and, after the instant of contact separation, immersion fluid can flow through said entry mouth about the actual surfaces of contact and out through the gas escape openings without appreciable restriction by the contacts, whilst constraining means such as a barrier and tubes surrounding the contacts are associated with the entry mouth in such a manner that upon tripping the switch or circuit-breaker the fluid is adapted to flow into the entry mouth to produce an appreciable pressure within the housing for effecting the rapid extinction of the arc. As shown in Fig. 1, the arcing contacts consist of plug members 5 engaged by angularlyspaced contact fingers 3 which project inwardly through the sides of a metal housing 21. The fluid pressure is produced by a piston 12 in a cylinder 11 which on opening of the switch drives fluid from below the insulating barrier 10 upwardly through the contact housings which are each provided with one or more relief outlets 22. As shown in the detailed view of the contact structure in Fig. 2, the entry mouth 20 of the contact housing is tapered so that the plug contact is separated near its contacting portions by a narrow annular passage for the flow of insulating fluid and thus during operation of the circuit-breaker the oil can flow freely through the contact and housing in the neighbourhood of the arc, so producing a rapid extinction of the arc drawn between the separating contacts. The presence of large metal surfaces adjacent the separating contacts cools and restricts the arcing. The housing 21 is attached to the leading-in conductor 23 and is mounted within an insulating shrouding tube 9 in an oiltight manner. The contact fingers 3 are secured to arms 25 spring mounted upon studs 27 and provided with hemispherical pivotal end pieces 26 bearing on corresponding seatings to enable the contact fingers to bear evenly on the sides of the movable arcing contact 5. In the modified form of contact shown in Fig. 5 a hexagonal contact rod formation is employed and contact fingers 3 are mounted to engage alternate faces of the rod. The arcing housing in this arrangement is constituted by a cage-like structure consisting of the contact finger supports 25 and of metal strips 36 intermediate the contact fingers, the strips 36 supporting a mouth ring 24. In a further modification, Fig. 6 (not shown), the mouth ring is formed of segments normally pressed apart by an enlarged portion of the plug 5 so that when the contacts are in engagement passages are formed between the segments by which the flow of oil or other insulating fluid may take place into the arcing housing. During the separation of the contacts in this modification, the mouth ring contracts, but a passage for the flow of oil &c. still exists between its internal bore and the reduced tip of the contact rod 5. In a further modification of a switch arranged as shown in Fig. 1, the relatively fixed'contacts with their associated parts are arranged to be movable within the tank for isolating purposes. Specifications 286,429, [Class 38 (v), Electric switches &c.], 350,529, 350,915, 351,253, 372,027, 376,300, 388,509, and 392,930 are referred to.