GB1404896A - Methods of manufacturing commutators for rotating electrical machines - Google Patents

Abstract

1404896 Making commutators ASSOCIATED ELECTRICAL INDUSTRIES Ltd 3 April 1974 [4 April 1973] 16087/73 Heading B3A [Also in Division C7] A method of making commutators for rotating electrical machines comprises disposing a plurality of insulating members 2 in spaced relation to form gaps, defining regions to be occupied by electrical conductors 1 and filling the gaps with electrically conductive material by an electrical deposition process. One of the flat sides of each insulating member 2 is cleaned and covered with a conductive dust, e.g. of silver or graphite. The covering is heated to form a conductive film on the member 2. The members are placed in a non-conductive frame at the required spacing and the gaps between them are bounded on one side by a coated face and on the other by an uncoated face. Each coated face is provided with an electrical connection and the assembly is immersed in an electrolyte containing an electrode of, e.g. copper or copper-silver alloy. Deposited metal builds up on each coated face and when the gaps are filled, the assembly is removed from the bath, rinsed and neutralized in known manner. The frame used during plating is replaced by a permanent one. In an alternative method, uncoated members (2), Fig. 2 (not shown), are again arranged in a non- conductive frame and the assembly is mounted on a conductive tubular mandrel (3). An electrical connection is made to the mandrel (3). An electrical connection is made to the mandrel and the assembly is immersed in a plating bath. Deposited metal builds up on the members (2) radially outwardly during plating and when this is completed the frame is replaced and the mandrel removed. Instead of the mandrel, a conductive tube (5) which surrounds the assembly may be used, or an electrode may be provided at one or both axial ends of the assembly. The commutator surfaces are machined to final dimensions and the ends of the rotor windings are connected to the conductors 1 by welding or brazing. Alternatively they may be located in the gaps between the members 2 prior to deposition, so that they become embedded in the conductors or metallic strips may be placed in the gaps for subsequent connection to the windings.