GB748893A - Improvements relating to commutators for dynamo-electric machines - Google Patents

Abstract

748,893. Commutators for dynamo-electric machines. HOOVER, Ltd. April 9, 1954 [April 14, 1953], No. 10210/53. Addition to 677,779. Class 35. [Also in Group XXII] A modification of the method of making a commutator claimed in the parent Specification comprises impact extruding a metal blank to form an annular member having a tubular wall, 11, Fig. 5, with internal fins 12 and an internal flange or a closed end 13, and at least one connecting tongue 14 for each segment, removing at least part of the flanged or closed end 13 so that at the junction between adjacent segments it will have the same inner radius as the tubular wall, moulding plastic insulating material 33, Fig. 11, into the tubular wall and then dividing the latter into seg. ments. A solid or annular disc of copper is placed in an extrusion die 15, Fig. 1, and pressure is applied thereto by a punch 26 to extrude the disc forwardly over a fixed vertical pin 19, having longitudinal grooves 25 which form the keying fins 12, and rearwardly into longitudinal grooves 27 in the punch which form the connecting tongues 14. The annular member thus produced is removed from the die by an ejector 24 operated by push-rods 23. The closed end 13 is then partly removed by punching to form the member of Fig. 8 (not shown). After the insulating material 33, Fig. 11, has been moulded between an inner bush 34 and the tubular wall, into which it is secured by dovetails 35 formed between adjacent fins 12, the commutator blank is inserted in a die 36, Fig. 9, and the connecting tongues 14 are first bent at right angles by a punch 37 and then bent rearwardly by a second punch 38. The tubular wall is finally divided by saw-cutting. The keying fins 12 of each segment may alternatively overlap each other or may be inclined away from each other.