Electric contact element

567,616. Magnetic blow-outs. BRITISH THOMSON-HOUSTON CO., Ltd. May 3, 1943, No. 6972. Convention date, May 6, 1942. [Class 38 (v)] A magnetic blow-out device suitable for manually - operable and other slow - moving switches, comprises a magnet, which is preferably permanent and attached to the movable contact, arranged to produce a flux across the contact-surface, whereby the arc is drawn towards the movable contact and into cool air in the opening movement. The magnet may comprise an alloy of 6-15 per cent aluminium, 12-30 per cent nickel, 5 per cent copper if desired, and the rest iron. A button. 32 welded to a carrier strip 21 may be backed by a bar magnet, but, as shown, lies between polepieces 35, 36 of a U-shaped magnet 34 crimped into slots in strip 21. When 32 separates from fixed contact 15, successive planes of flux A , B , &c., each having the pattern shown at A' in Fig. 3, drive the arc from position A through B, C, &c. to H, so drawing the arc after the movable contact, with a force which gradually increases, into cooler air, where it is extinguished. The contact-structure is incorporated in a switch similar to that described in Specification 561,984, Figs. 1, 2 (not shown).