GB738823A - Improvements relating to commutators - Google Patents

Abstract

738,823. Dynamo electric machines. HOOVER, Ltd. June 16, 1953 [June 24, 1952], No. 15901/52. Class 35. [Also in Group XXII] A radial face type commutator, Fig. 5, is made by pressing a blank of conducting material to form a generally flat cylindrical shell having a front contact face 25 and at least one projection standing out from the rear face thereof, dividing the projection or projections, if necessary, so as to provide at least one projection 27, 30 for each commutator segment, moulding a body of insulating material 32 to the rear face of the shell after distorting the projections to form a key for the insulating material, and dividing the shell into segments. A copper disc 10, Fig. 1, is inserted in the die 11 of an impact extrusion press having a hollow punch 20 with peripheral grooves 24. The copper is caused to flow into a closed annular space around a central pin 12 where it forms a tubular projection 28 and is also extruded rearwardly into the grooves 24 to form separate projections or anchoring pins 27. The forward end of the punch has radially extending ribs 23 which form grooves 26, Fig. 3 (not shown), in the shell between the projections 27. The shell is ejected from the die by an ejector 14 actuated by a plunger 17 through pins 15, and is subsequently ejected from the punch by an ejector 21. The projection 28 is then slotted in a broaching machine to provide an inner anchoring pin 30, Fig. 5, for each segment. The anchoring pins 27, 30 are then bent inwardly. The shell and a metal bush 31 are inserted in a mould and a body of synthetic resin 32 is moulded around them. Finally the shell is divided into segments by saw cuts which meet each of the radial grooves 26. If necessary the latter may extend to the full axial thickness of the finished segments, and the latter are separated by machining the front face 25 of the shell. A slot 33 is cut in each segment to receive the connecting wire. The outer projections 27 may . also be formed as a single tubular projection which is subsequently divided by broaching into separate anchoring pins. One or more than two projections may alternatively be provided for each segment. The shell may alternatively be formed by a cold upsetting process. Instead of bending the projections they may have outer heads formed thereon by upsetting.