GB240912A - Improvements in or relating to magnetic brakes - Google Patents

Abstract

240,912. Chopra, N. D., and Bullen, F. J. July 8, 1924. Electromagnets.-In brakes of the kind in which a magnet acts upon a moving surface, the magnet is provided with a wearing member or members of relatively soft material compared with that of the pole-pieces, whereby chattering and wear of the pole-pieces is avoided. A material, for example phosphorbronze, having the same co-efficient of thermal expansion as that of the magnet steel is preferably used. Fig. 1 shows a skid brake shoe for engagement with a rail 3 in which blocks 2 of bronze or other material are dovetailed into the polepieces 1 and project slightly therefrom. Fig. 8 shows strips 2 of wearing material disposed between and on either side of the pole-pieces 1. As shown in Fig. 12, the wearing material 2 is in the form of a block surrounding both pole-pieces and is provided with holes into which parts 10 of the pole-pieces extend. The wearing material-may be spring-mounted so as to yield with respect to the magnet proper when the brake or the like is applied. Fig. 16 shows such an arrangement in which also the material is adapted to collect current from the rail. The strip 2 of bronze, copper &c. is adapted to yield against springs 6 bearing in sockets formed in the strip and abutting also against stops 8 on the magnet, the holes for the rivets 4 being elongated to allow of the movement. Insulating strips and cups 11, 13 and bushes around the rivets serve to insulate the strip 2 from which a conductor is led. As shown in Fig. 18, the wearing material 2 is in the form of a number of short U-shaped strips extending through holes in the pole-pieces, insulated by strips 16 and each adapted to yield against a spring 15. Additional pieces of soft material may be fixed to the pole shoes so as to come into contact with the rail to increase the frictional action after a preliminary depression of the collecting pieces when the device is magnetized to act as a brake. White metal, fabrics containing asbestos. wire and the like, also wires or cords woven or twisted to provide a resilient mass are mentioned in addition to copper and bronze as suitable wearing materials. The Provisional Specification is not restricted to skid brakes and states that the wearing material may be flush with the pole faces.