GB698716A - Improvements in the manufacture of insulated rings - Google Patents

Abstract

A method of forming an insulating coating on a ring comprises applying to the surface to be coated a layer of a heat hardenable insulating varnish, distributing over the surface fine grains of a hard insulating material, and baking the coated ring to cause the varnish to set hard and bond the said grains to each other and to the ring surface. A V-ring 15 for a commutator of an electric dynamo is held by a cup-shaped head 45 on a shaft 44, Figs. 2 and 6, rotated about its axis by an electric motor 40 through a reduction gear 41, Fig. 4. As the ring rotates the surfaces 15a and 15b, Fig. 6, are coated with a thermo-setting plastic varnish by a roll 35, Fig. 2, which receives the varnish from a roll 34 dipping in a vessel 22. The surface 15 b is coated because <PICT:0698716/III/1> <PICT:0698716/III/2> <PICT:0698716/III/3> varnish received on 15a creeps along 15b. The mounting for the shaft 44 is supported by a bracket 51, pivoted on a screw 52, Figs. 2 and 4, and held in the coating position by a peg 53. When the ring has been coated the roll 35, which is supported by a yoke 30, Fig. 2, is removed from contact with the ring 15 by swinging the yoke about a shaft 24, which carries the roll 34. The bracket 51 is then turned about the pivot 52 to a position where the peg 53 locates a hole 15b, Fig. 4. In this position fine dry sand runs from a container 60 when a valve is opened and falls in a stream upon the wet varnish of the rotating ring. When the ring has retained sufficient sand it is removed from the holder 45 and baked to harden the varnish, to produce an insulating layer of sand bonded to the ring.