GB1478883A - Commutators - Google Patents

Abstract

1478883 Commutators NATIONAL RESEARCH DEVELOPMENT CORP 22 May 1975 [10 June 1974] 25623/74 Heading H2A A commutator has a set of conductive segments, e.g. segments 18, 19 of cylindrical form, each shaped so that on rotation of the commutator a brush 23 makes a substantially stepwise increase in the contact area with a segment 19 as the brush crosses a boundary 17 between two segments, and it then either (a) increases the contact area with segment 19 at a substantially linear rate, i.e. when the boundary 17 continues in the straight line shape indicated by the line 21, or (b) subsequently increases the contact area with segment 19 at a mean rate which progressively declines, i.e. when the boundary 17 continues in a curved form such as indicated by line 24 or line 25. The continuation boundary may be generally curved, but formed by small steps (26, Fig. 5, not shown), and it may include a strip section (27) to reduce the possibility of sparking. The segments may alternatively form a disc commutator (1, Fig. 1, not shown). In each case, the brush may be of carbon fibre structure, as in Fig. 6 (not shown), the brush having a greater contact resistance at the trailing edge than at the leading edge.