Improvements to the contacts or to the contact pads for electric circuit-breakers

摘要

493,454. Switch contacts. WEST & CO., Ltd., A., and BABLER, E. April 8, 1937, No. 9989. [Class 38 (v)] [Also in Group XXII] Methods of making a switch contact of the type described in Specification 471,538 comprising a body of good-conducting material reinforced by laminations of a material of higher melting-point, include that shown in Fig. 1. A plate of refractory material such as tungsten or molybdenum is bent backwards and forwards to form a laminated structure la which is immersed in molten conducting metal the whole being cut into contact tips when cold. The refractory material may be annealed after bending to remove its natural resiliency, and stiffened by welding cross-pieces, while to provide a larger adhering surface the plate may be corrugated or formed of interwoven strips. The mould used for casting may be of ceramic material, or of iron to be machined off later. Alternatively the refractory insert may be formed by pressing a powder into a mould with or without an organic binder such as gum-arabic or paraffin wax, or may be formed of graphite, alumina, silica, silicon oxide or zirconium oxide. The pores of the refractory material may be filled with a separate cementing metal such as iron, nickel, or platinum which has a melting-point between that of the insert and the conductor metal. Graphite inserts produce a surface film which helps to prevent welding between contacts. Other forms of insert are described including powdered material pressed into slots and soldered in position, and a sandwich of refractory material 16 between two layers of conducting metal 2b rolled up and machined circular as shown in Fig. 8. Reference has been directed by the Comptroller of Specification 471,538.