GB2224605A

GB2224605A - Assembled commutator for electric motor

Info

Publication number: GB2224605A
Application number: GB8823991A
Authority: GB
Inventors: Patrick Shui-Chung Wang
Original assignee: Johnson Electric Industrial Manufactory Ltd
Current assignee: Johnson Electric Industrial Manufactory Ltd
Priority date: 1988-10-13
Filing date: 1988-10-13
Publication date: 1990-05-09
Anticipated expiration: 2008-10-13
Also published as: GB8823991D0; GB2224605B

Abstract

An assembled commutator 1 has a thermoplastics base 2 supporting segments 6. A ring 15 of high temperature, non- softening material, such as phenolic, fits on a shelf 14 on the base beneath tangs 9 which are for hot connection, particularly forging, to an armature wire. The ring 15 is held in place by fingers 16 on the tangs. <IMAGE>

Description

ASSEMBLED COMMUTATOR The present invention relates to an assembled commutator in which the segments have tangs arranged to be connected to an armature winding wire by a hot connection, such as forging or soldering.

When forging a connection between the segment tang and armature wire, both heat and pressure are applied to the tang. This can result in distortion of the commutator base beneath the tang. If the distortion is too great the base collapses away from beneath the tang so that it is no longer adequately supported in the forging process. The forging process typically produces a temperature of 430 degrees centigrade at the tang. Thermoplastics materials, which are most desirable for forming the commutator base, can withstand this temperature, but the combination of temperature and pressure distorts the base.

According to the present invention, there is provided an assembled commutator comprising a cylindrical base of thermoplastics material having a plurality of commutator segments mounted thereon, each segment having at an end thereof a tang for connection to an armature winding wire by a process involving heat, wherein an annular ring is provided on the base beneath the tangs, the ring being of high temperature non-softening material.

Preferably the ring is of phenolic, fibre-filled phenolic, or fibre material. Such materials may withstand temperatures higher than 500 degrees centigrade and will not soften, but rather will char at too high a temperature. The invention is particularly applicable to hot forging but also applicable to other techniques such as soldering the wire to the tangs.

Preferably the ring is held in place by fingers on the segment end which grip the ring.

The invention will be further described by way of example with reference to the accompanying drawing which is a side view in partial cross-section of an assembled commutator forming an embodiment of the invention.

Referring to the drawing, an assembled commutator 1 comprises a cylindrical base 2 of thermoplastics having a main segment supporting part 3, a collar 4 and a spacer part 5 at â rear end which is arranges to abut a lamination stack of an armature. A plurality of commutator segments 6 (five in the example shown) are mounted on the base 2. Each segment 6 has a brush contacting part 7 with a finger at one end which locks into a recess 8 in the front end of the base 2, and a tang 9 at other end. Tangs 9 extend radially out from the brush contacting parts 7, 12 and have apertures 10 which fit over projections 11 on the front face of the collar 4 to hold that end of the segment against the base. The brush contacting part 7 may be glued to the base.

The tangs 9 end in a U-shape 13 which rests on the collar 4. A shelf 14 is formed in the rear of the collar 12. A ring 15 of phenolic material or other high temperature, non-softening material such as fibre or fibre-filled phenolic is fitted on the shelf 14 beneath the U-shape parts 13. Fingers 16 on the tangs 9 extend to either side of the U-shape parts 13 and are bent over to hold the ring 15 in place, and also help hold the segments against axial movement on the base 2.

When forging a wire to a tang 9, the wire is looped into the U-shape part 13. A first electrode bears down on the U-shape part to collapse it onto the wire and a second electrode bears onto a wing 17 to one side. The phenolic ring 15 will withstand the heat generated and the pressure of the first electrode without softening or collapsing.

The invention is also of advantage when the wire is soldered to the tang.

As shown in dotted outline, a resistor or varistor ring 18, or other suppression element may be positioned on a second shelf 19 inside the ring 15 and the fingers 16 extended down to make electrical contact with the ring. In another embodiment, the suppression element may be positioned beside the phenolic ring and make electrical contact with the underside of the tangs or fingers. In another embodiment the ring 15 has a coating of resistive material which electrically connects the fingers 16 of adjacent segments.

The shelf 14 need not be continuous but may, for example, be formed on buttresses at the rear of the collar 4.

Various modifications may be made to the described embodiment and it is desired to include all such modifications as fall within the scope of the accompanying claims.

Claims

1. An assembled commutator comprising a cylindrical base of thermoplastics material having a plurality of commutator segments mounted thereon, each segment having at an end thereof a tang for connection to an armature winding wire by a process involving heat, wherein an annular ring is provided on the base beneath the tangs, the ring being of high temperature, non-softening material.

2. A commutator as claimed in claim 1, wherein the ring is supported on a shelf beneath the tangs.

3. A commutator as claimed in claim 1 or 2, wherein the ring is held in place by a finger on a tang.

4. A commutator as claimed in claim 1, 2 or 3, wherein the ring is of phenolic material.

5. A commutator as claimed in claim 1, 2 or 3, wherein the ring is of fibre material.

6. A commutator as claimed in any one of claims 1 to 5, wherein the ring has a coating of electrically resistive material which electrically connects adjacent segments.

7. A commutator as claimed in any one of claims 1 to 5, wherein a suppression element is provided adjacent the ring and in electrical contact with the segments.

8. A commutator substantially as hereinbefore described with reference to the accompanying drawings.