GB2256753A

GB2256753A - Roller brushes for an electric motor

Info

Publication number: GB2256753A
Application number: GB9112412A
Authority: GB
Inventors: Tak-Tung Tse
Original assignee: TSE TAK TUNG
Current assignee: TSE TAK TUNG
Priority date: 1991-06-10
Filing date: 1991-06-10
Publication date: 1992-12-16
Also published as: GB9112412D0

Abstract

An electric motor (1) is provided with brushes in the form of rollers (2). The rollers (2) and the segments of the commutator (4) may be arranged at a skew angle to one another to prevent the rollers (2) entering the gaps between the segments. The rollers may also be arranged to produce a wiping action in addition to their rolling action, so as to clean the contacting surfaces. <IMAGE>

Description

AN ELECTRIC MOTOR The present invention relates to electric motors.

Electric motors include a rotating commutator divided into a number of segments with gaps between them, and stationary brushes which engage the surface of the commutator, engaging each segment in turn as the commutator rotates.

In conventional electric motors, the commutator is generally cylindrical, and is divided into linear segments. The brushes are in the form of blocks. The disadvantage of this arrangement is that there is friction between the rotating commutator and the stationary brushes, requiring additional power to start the motor, a waste of power during operation of the motor, heating problems, noise problems, sparks which may cause electrical interference, and quick wear of the brushes.

The invention provides a motor in which the brushes are in the form of rollers, thereby eliminating the above described problems.

The invention will now be described more particularly with reference to the accompanying drawings in wnich Figures 1 to 6 show a variety of different constructions of electric motor provided with roller brushes.

Referring initially to Figure 1, there is shown a particularly simple motor according to the invention. The commutator 1 is of conventional design. The brushes 2 consist of rollers instead of blocks. This particularly simple design suffers from the disadvantage that as the commutator 1 rotates the brushes 2 are depressed into the gaps 3 between commutator segments 4, and therefore the segments tend to deform at the edges 5 and finally lead to short circuiting between segments. This disadvantage may be overcome by filling the gaps 3 between the segments 4 with an insulating material (not shown) to provide a smooth outer surface for the commutator 1, but this modification in turn leads to the problem that when the motor is switched off one or both of the brushes 2 may come to rest in engagement with the insulating material, presenting possible difficulties in re-starting the motor.

Referring now to Figure 2 there is shown an alternative construction in which the commutator 20 is again cylindrical but the segments 24 of the commutator and the gaps 23 between the segments are of spiral shape. The brushes (not shown) which are of linear shape cannot enter these spiral shaped gaps 23, and are always in contact with at least one segment 24.

Referring now to Figure 3 there is shown a still further construction in which the brushes 31 consist of conical rollers. As the conical rollers 31 rotate, the speed of rotation varies along the length of the conical roller, being greatest at the wide end of the roller and least at the narrow end of the roller. This difference in speed along the length provides a wiping action which is intermediate between a pure rolling action and the sliding action of the conventional brushes. The purpose of this wiping action is to clean the surface of the brushes 31 and the commutator 30, which a pure rolling action may not do.

Referring now to Figure 4 there is shown a still further construction in which the brush 41 is cylindrical, and the wiping action is produced by axial movement of the brush 41. The axial movement is produced by means of a spiral groove 45 in the roller brush, and a fixed guided member 46 projecting into the spiral groove 45 so that as the roller rotates it is caused to reciprocate axially.

Referring now to Figure 5 there is shown a still further arrangement comprising a conventional commutator 50, and brushes 51 which have the shape of reels for thread and are disposed at a skew angle to the commutator. This arrangement overcomes the possible problem of the brushes entering the gap 23 between segments 24 or coming to rest in engagement with the gaps 23, and also provides a wiping action.

Referring now to Figure 6 there is shown a still further construction, in which the commutator 60 and the brushes 61 are gear shaped. This arrangement produces a larger area of surface contact and good wiping and cleaning.

Claims

1. An electric motor in which the brushes are in the form of rollers.

2. An electric motor according to Claim 1 in which the line of contact of the rollers with the commutator and the lines of division of the segments of the commutator are at a skew angle to one another.

3. An electric motor according to Claim 1 or Claim 2, in which the rollers are so arranged as to produce a wiping action on the surface of the commutator.

4. An electric motor according to Claim 1 in which the brushes and the commutator are in the shape of meshing gears.

5. An electric motor substantially as herein described, with reference to or as illustrated in the accompanying drawings.

6. Any novel combination or sub-combination disclosed and/or illustrated herein.