GB1563207A

GB1563207A - Brush for a dynamo electric machine

Info

Publication number: GB1563207A
Application number: GB5246375A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1975-12-20
Filing date: 1975-12-20
Publication date: 1980-03-19
Also published as: DE2657226A1; ES454236A1; AU2026076A; JPS5292304A; FR2335968A1; BR7608477A; IT1074227B

Description

(54) A BRUSH FOR A DYNAMO ELECTRIC MACHINE (71) We, LUCAS INDUSTRIES LIMITED, of Great King Street, Birmingham, B19 2FX, a British Company, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a brush for a dynamo electric machine.

According to the invention, a brush for a dynamo electric machine comprises a conductive carrier member, and a conductive body formed from a sintered powder compact containing copper, the body defining the electrical contact of the brush and being in part engaged as a press fit in a hole in the carrier member with the remainder of the body projecting from the carrier member, and said carrier member being adapted to have an electric lead connected thereto.

Preferably, said hole in the carrier member is formed by a plunging operation.

Preferably, said sintered powder compact contains at least 75% by weight of copper.

Conveniently said carrier member is formed of copper-plated steel.

The invention further resides in a method of producing a brush for a dynamo electric machine, comprising the steps of starting with a conductive carrier formed with a hole therein and adapted to have an electrical lead connected thereto, and engaging as a press fit in said hole part of a conductive body so that the remainder of the body projects from the carrier member to define the electrical contact of the brush, the body being formed from a sintered powder compact containing copper.

Preferably, said carrier member and said body, prior to interengagement thereof, are arranged so that the circumference of said part of the body exceeds the circumference of the hole by 1--3%, press fitting of the body in the hole thereby compressing said part of the body.

In the accompanying drawings, Figure 1 is a perspective view of a brush according to one example of the invention, Figure 2 is a sectional view of part of the brush shown in -Figure 1, and Figure 3 is a perspective view of part of a brush according to a modification of said one example.

Referring to IFigures 1 and 2, the brush of said one example includes a conductive, carrier member in the form of a copper-plated, steel strip 11. Alternatively, the strip 11 could be formed of brass or copper Formed in the strip 11 is a drilled, first hole 12 for enabling an electrical lead (not shown) to be connected to the strip and a plunged, second hole 13 spaced from the hole 12. Engaged as a press fit in the hole 12 is a cylindrical stem of a conductive, metal-containing body 15, the remainder of the body 15 being generally wedge-shaped in transverse cross-section and projecting from one surface of the strip 11 to define the electrical contact of the brush.

The body 15 is formed from a sintered powder compact which contains copper and preferably contains at least 75% by weight of copper. Thus, in one practical embodiment, the body 15 is formed from a sintered, compressed powder mixture consisting of not less than 76.5% by weight of copper, 3.7 to 5.1% by weight of manganese, 4.0% to 5.0% by weight of carbon, and 10.8 to 13.2% by weight of lead.

As shown in the drawings, the stem 14 and plunged hole 13 are circular in section and preferably, prior to engagement in the hole 13, the stem 14 is arranged to have a circumference exceeding the circumference of the hole 13 by between 1 and 3%. This of course means that press fitting of the stem 14 in the hole 13 compresses the stem 14 and, to a lesser extent, causes the wall of the hole 13 to expand. In addition, the length of the stem 14 is preferably arranged to exceed that of the hole 13 so that the free end of the stem projects beyond the hole in the assembled brush. In this way, during assembly of the brush, the free end of the stem is initially compressed by the wall of the hole 13, but thereafter the compressive forces are released so that, as it moved beyond the hole 13, the free end of the stem 14 tens to return to its original shape. This effect is apparent from Figure 2 and results in the formation of an annular lip 14a at the free end of the stem, which lip aids retention of the body 15 by the carrier member 11.

Figure 3 illustrates a modification of the above example, in which a similar carrier member 11 is employed, but now the plunged hole 13 is of generally rectangular configuration. Of course, with such an arrangement, the portion of the contact-defining body to be engaged in the hole 13 would also be of rectangular configuration.

WHAT WE CLAIM IS: 1. A brush for a dynamo electric machine, comprising a conductive carrier member, and a conductive body formed from a sintered powder compact containing copper, the body defining the electrical contact of the brush and being in part engaged as a press fit in a hole in the carrier member with the remainder of the body projecting from the carrier member, and said carrier member being adapted to have an electrical lead connected thereto.

2. A brush as claimed in Claim 1, wherein said hole in the carrier member is formed by a plunging operation.

3. A brush as claimed in Claim 1 or Claim 2, wherein said body is formed from a sintered powder compact containing at least.

75% by weight of copper.

4. A brush as claimed in Claim 3, wherein said carrier member is formed of copperplated steel.

5. A method of producing a brush for a dynamo electric machine, comprising the steps of starting with a conductive carrier formed with a hole therein and adapted to have an electrical lead connected thereto, and engaging as a press fit in said hole part of a conductive body so that the remainder of the body projects from the carrier member to define the electrical contact of the brush, said body being formed from a sintered powder compact containing copper.

6. A method as claimed in Claim 5, wherein said carrier member and said body, prior to interengagement thereof, are arranged so that the circumference of said part of the body exceeds the circumference of the hole by 13%, press fitting of the body in the hole thereby compressing said part of the body.

7. A method of protecting a brush for a dynamo electric machine, substantially as hereinbefore described.

8. A brush for a dynamo electric machine produced by a method as claimed in any one of Claims 5 to 7.

9. A brush for a dynamo electric machine substantially as hereinbefore described with reference to and as shown in Figures 1 and 2 or Figure 3 of the accompanying drawings.

10. A dynamo electric machine including a brush as claimed in any one of Claims 1 to 4 or Claim 8 or Claim 9.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. from Figure 2 and results in the formation of an annular lip 14a at the free end of the stem, which lip aids retention of the body 15 by the carrier member 11. Figure 3 illustrates a modification of the above example, in which a similar carrier member 11 is employed, but now the plunged hole 13 is of generally rectangular configuration. Of course, with such an arrangement, the portion of the contact-defining body to be engaged in the hole 13 would also be of rectangular configuration. WHAT WE CLAIM IS:

1. A brush for a dynamo electric machine, comprising a conductive carrier member, and a conductive body formed from a sintered powder compact containing copper, the body defining the electrical contact of the brush and being in part engaged as a press fit in a hole in the carrier member with the remainder of the body projecting from the carrier member, and said carrier member being adapted to have an electrical lead connected thereto.

75% by weight of copper.