GB404178A - Brush lifting gear for electric motors - Google Patents

Abstract

404,178. Alternating-current commutator machines. WOODS, Ltd., M. W., and GREENWOOD, M. I., Windifan Works, Colchester. April 11, 1933, No. 10816. [Class 35.] In brush-lifting gear wherein the brush-holders are engaged in both their directions of movement by pivoted centrifugal arms which swing in a plane transverse to the motor shaft, the brushes are moved substantially radially through a mechanism which is urged away from an unstable mid position in both directions so that a snap action is obtained. In the form shown, the brush-holders 3, which are slidable on pins 5, are urged inwards when the motor is stationary by leaf springs 9 lodged between notches 8 in the brush-boxes and notched pins 11 carried by a stationary plate 6. As the arms 14 move outwards, the brush-holders are pushed outwards until the springs 9 pass their mid position and cause the holders to snap into their outermost position shown in Fig. 3. The brushes 1 are urged by the springs 4 to remain in contact with the commutator but they are provided with flanges 22 and are of such maximum length that they are lifted before the holders reach their outermost position. As the arms 14, which are pivoted at 16 on a disc 13 on the shaft, are drawn inwards by springs they engage a projection 23 on the holder and return the brushes. The movement of the arms is limited by slots 19 such that in both end positions the arms are out of contact with the holders 3 and lugs 23. The movement of the weights may be equalized by a ball and socket engagement at their pivot ends, a common spring being used, or alternatively the two weights may be independent. Any type of short-circuiting device may be provided.