Electric motor with brush holder and its assemblage method

Abstract

A universal motor has a brush cage assembly in which a U-shaped clip 34 is located about a wall of a through hole 28 of a bearing bracket 24 for receiving a brush cage 30. The clip 34 has an outer limb 42 with inwardly and rearwardly directed barbs 44 to grip an outer surface of the wall to prevent removal of the clip 34 and an inner limb 36 with outwardly and forwardly directed barbs 42 which resiliently deform as the cage 30 is inserted to snare the cage 30 should it move in the opposite direction. The clip 34 thus prevents withdrawal of the brush cage 30 and provides a lateral spring force against the cage 30 to reduce cage lateral position tolerance and movement.

Description

technical field [0001] The present invention relates to motors, and more particularly to brush holder assemblies for small motors. Background technique [0002] Many small brush motors, such as fractional horsepower general purpose motors and miniature DC motors, have brush boxes that direct the brushes into contact with the commutator. Typically such a brush box is basically a brass tube in which the brushes slide under the action of brush springs. The brush tubes are fixed to the motor structure to ensure accurate positioning of the contact points between the brushes and the commutator. Typically, the motor construction consists of a plastic or similar insulating material bearing housing into which a brass tube is pressed into a bore. Also, when the bearing housing is conductive, insulating bushings are used to secure the brass tube to the bearing housing. [0003] The brush tube requires means for fixing the brush tube in the hole of the insulator. Typically this is a...

AI Technical Summary

Problems solved by technology

If the inner diameter of the pipe is too small, the brush will not be able to slide; if the inner diameter is too large, the brush will shake in the pipe, causing instantaneous discharge of the commutator, resulting in rapid wear of the brush and commutator

Likewise, the holes in the insulator must be tightly controlled so that the pipe is properly gripped, but not so tight that the pipe deforms and catches the brushes

Another downside is that the snap fingers are not very resilient and usually don't spring back enough to keep the pipe in place

To overcome this problem, the groove for this finger is made relatively large to ensure the clearance between the finger and the groove, however, this will cause axial movement of the brush, which in turn will cause vibration under the effect of vibration. instantaneous discharge

[0005] Although some motors do not use brass brush boxes and allow the brushes to slide directly in the through holes in the bearing housing, this is not suitable for high speed and high power motors, where positioning and heat dissipation are extremely important issues

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