Patent GB-392930-A (GB)
Title: Improvements in electrical switches or circuit breakers and in the co-operating contacts thereof
IPC: E21F9/00
Filed: 1931-11-18
Abstract: 392,930. Heavy-current switches. WHITEHEAD, G. E. and WHITEHEAD'S ELECTRICAL INVENTIONS, Ltd., 38, Rhiwbina Hill, Rhiwbina, near Cardiff. Nov. 18, 1931, Nos. 4859/33 and 4860/33. Divided on 392,926. [Class 38 (v).] The contacts of heavy - current switches or circuit-breakers each comprise a pair of relatively longitudinallv movable co-operating contacts one of which is of plug or similar elongated form whilst the other contact has its contact surface or surfaces disposed within and between the ends of a tubular metal arcing chamber or housing and moderately protruding inwards from the inner wall surface of said arcing chamber or housing which has a ring mouth through which the elongated co-operating contact can enter with a small annular clearance, to engage only the contact surface or surfaces within said housing which comparatively closely surrounds the engaged contacts and is provided with at least some further moderately restricted opening for the free escape of arc gases, the housing constituting an arc-confining and arcquenching cage having at all times a free oil channel through it. As shown in Fig. 1, the plug contact 5 projects within the metal arcing housing 21 and is engaged on its periphery by contact fingers 3 which project inwardly through holes in the housing and are carried by arms 25 terminating in spherical bearing projections 26 resting in corresponding recesses formed in the arcing housing. The contacts 3 are pressed against the sides of the plug 5 by springs 27 on studs 28 and may be spaced at 120 around the housing. The housing is formed with an enlarged mouth 20 terminating in a flange against which the laminated main contacts 6 are adapted to bear. The housing is formed with at least one moderately restricted outlet 22 for the escape of the arc gases, which with the space separating the plug contact from the housing permits a free oil channel through the housing at all times and especially when the arc is drawn between the plug 5 and the contacts 3. The arcing housing may be secured in an oil-tight:manner within an insulating tube 9. which may be located in a partition within a tank the space below which is completely filled with oil, the openings 22 communicating with the atmosphere. In a modified form of contact, Fig. 4, a plug 5 of hexagonal form is employed, alternate faces of which are engaged by flattened contact fingers 3. The arcing housing in this form is constituted by a cagelike structure consisting of the contact finger supports 25 and of metal strips 36 intermediate the contact fingers and supporting at their lower ends a mouth ring 20. In a further modification, Fig. 5 (not shown), the mouth ring is formed into 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 contacts, but a passage for the flow of oil &c. still exists' between its internal bore and the reduced tip of contact 5. Specifications 286,429, [Class 38 (v), Electric switches &c.], 350,529, 350,915, 351,253, 376,300, 388,509, and 392,926 are referred to.