GB561984A - Improvements in and relating to electric contact elements combined with magnetic blow-out devices - Google Patents

Abstract

561,984. Arc-rupturing in switches. BRITISH THOMSON - HOUSTON CO., Ltd. Jan. 7, 1943, No. 289. Convention date, Jan. 14, 1942. [Class 38 (v)] [Also in Group II] A magnetic blow-out device, suitable for a manually-operable or other slow-break switch, comprises a disc-like permanent magnet mounted within, and coaxially with, each contact, opposite poles being in juxtaposition. Movable contacts 32 co-operating with fixed contacts 15 are mounted on the ends of spring fingers 21, each apertured to receive a cylindrical contact-button 32 housing a permanent disc magnet 33 secured by spinning over the rim at 34 in both directions. The button may be of silver throughout but is preferably a silver-molybdenum tip brazed to a brass bushing, Fig. 4 (not shown). Contacts 15 are similar to 32 and interconnected by a strap 35 overlying a block 14 and provided with a terminal 16. A number of contact pairs may be assembled one behind the other in a casing 10, and separated by insulating partitions 17 secured together by octagonal bosses 18 in one engaging like recesses in the adjacent one, Fig. 1 (not shown). Levers 22 carrying the fingers 21 are pivoted at 18 and respectively operable by cams 27, 29 on a shaft 30 for closing circuit and both opened by cam 28 and pins 23. Suitable alloys for the permanent magnets are disclosed in Specifications 423,897 and 424,746, [both in Group II], comprising 6 to .15 per cent aluminium, 12 to 30 per cent nickel, about 5 per cent cobalt or chromium, if desired, and the remainder iron. The Specification as open to inspection under Sect. 91 discloses an alloy in which cobalt or chromium in the above alloy is replaced by copper. This subject-matter does not appear in the Specification as accepted.