GB380770A - Improvements in or relating to dynamo electric machines - Google Patents

Abstract

380,770. Alternating -current commutator motors. SCOTT, W., 13, Edwardes Square, Kensington, London. June 13, 1932, No. 16660. [Class 35.] Commutator short-circuiting and brush lifting mechanism for an induction motor started as a repulsion motor comprises a series of shortcircuiting elements each of which moves about one axis to short-circuit the commutator and thereafter moves about a second axis to raise the brushes. The short-circuiting elements 21, Figs. 1, 5 surround a sleeve 17 slidable but not rotable on the shaft 1 and are held by a steel or other conducting ring 20 engaging hook-like extensions 22. The elements are maintained in the position shown in Fig. 1 by an endless spring 24 accommodated in slots 23. The sleeve 17 carries a cylindrical shield 25 surrounding the members 21, and a second sleeve 27 mounted between flanges or washers 29, 30. The elements 21 are driven by means of a washer 34 having projections 35 extending between some of the elements. The brushholders 7 are pivoted to lugs 6 on the brush rocker 5 which has radial holes to receive brush lifting push-rods 15. In operation, the elements 21 first turn about the pivoting ring 20 so that their ends 36 bear against extensions 4 of the commutator segments, which are thereby shortcircuited. The slots 23 are of such length and shape that the spring moves down the base thereof and effects a rapid overbalancing action. As the speed increases, the elements 21 continue to move outwards but the ends 36 constitute the pivots. The ends 22 accordingly move to the right whereby the sleeve 17 is moved against the action of a spring 33. At the same time, the sleeve 27 is moved axially' without rotating and the surface has such a shape that through the balls 16, the rods 15 are forced outwards, thus raising the brusharms 7. During slowing down of the motor, the spring 24 again produces a quick overbalancing to replace the commutator brushes and to remove the commutator short-circuit. In a modification, the brush boxes are fixed and the push-rods 15 operate on members engaging under pins projecting from both sides of the brushes to lift the brushes from the commutator.