GB2103889A

GB2103889A - Making connections to electrical brushes

Info

Publication number: GB2103889A
Application number: GB08123986A
Authority: GB
Inventors: Royston Amos Cheesmore
Original assignee: Morganite Electrical Carbon Ltd
Current assignee: Morganite Electrical Carbon Ltd
Priority date: 1981-08-05
Filing date: 1981-08-05
Publication date: 1983-02-23
Also published as: GB2103889B

Abstract

An electrical connector 5 is connected to an electrical brush having at least one surface portion (4) with a sufficiently high metallic content to render the portion malleable, by forming one or more integral studs (2, 3) upstanding from said surface portion; providing aperture(s) (8) or (9) in the electrical connector (5), each to fit with clearance over a stud; placing the connector on the brush with the or each stud projecting through a connector aperture; and deforming the free end (10) of the or each stud (11) to rivet or forge the connector to the brush. <IMAGE>

Description

SPECIFICATION Making connections to electrical brushes This invention relates to a method of making an electrical connection to an electrical brush, e.g. a carbon, metallic or graphitic brush for a dynamoelectric machine.

According to the present invention, a method of making an electrical connection to an electrical brush, having at least one surface portion with a sifficiently high metallic content to render the portion malleable, comprises the steps of forming one or more integral studs upstanding from said surface portion; providing an aperture or apertures in an electrical connector, each to fit with clearance over a stud; placing the connector on the brush with the or each stud projecting through a connector aperture; and then deforming the free end of the or each stud to rivet or forge the connector to the brush.

A variety of engineering materials can be used for the brush provided the material can be riveted or forged and remains malleable after the connector has been attached to the brush.

Generally, to be malleable, the brush surface portion should have a metallic content of approximately 60% by weight. Suitable metallic fillers include copper, iron, tin, steel, lead, aluminium, silver and alloys thereof.

In one emobidment of the invention the surface of said portion of the brush is metallised to further improve the electrical connection between the connector and the brush. Alternatively, or additionally, the connector may be soldered to the brush; again to further improve the electrical connection.

The advantages of brushes made in accordance with the invention are that it: saves brush material or allows a longer brush to be used in an existing brush assembly; enables larger electrical connections between flexible conducting shunts and the connector to be used and insulated flexibles (if required), both without effecting the operation of ancillary items such as the operating spring; permits connections to be made and terminated from many directions, thus making the entry and size of connection an easy and precise machine operation; increases the mechanical efficiency of the connection permitting maximum wear life with minimum cross-sectional area of the brush, which can be partitioned to allow an airgap for cross brush resistance; increases the thermal efficiency of the connection, thereby reducing brush operating temperatures;; enables a connection to be made with a minimum of tools, allowing on-the-spot repairs to be carried out; and allows brushes and connectors to be assembled by existing engineering methods which can be controlled for quality and mechanised and automated for ease of production.

The invention is illustrated by way of example in the Drawings, wherein:- Fig. 1 is a perspective view of a brush formed in accordance with the invention, prior to assembly with a cap; Fig. 2 is a similar view of a cap, prior to assembly with a brush; and Fig. 3 is a cross-section of an assembled brush and cap.

As shown, a generally conventional brush 1 , for example formed of a sintered copper-carbon or copper-graphite composition, typically 78% copper, 4.4% graphite, 12.2% litharge, 5.4% ferro manganese alloy (by weight), to have a rectangular cross-section and a concave contact surface, is formed with two rectangular studs 2 and 3 upstanding from the top 4 of the brush. The brush, which may be a one, two or multiple part brush, is first pressed to shape and size and the thus formed pellet is then heat treated to sinter the composite.

A generally rectangular metal cap 5, in this example of thick-tin plated mild steel, is preformed to have upstanding tabs 6 and 7 at each end and two rectangular apertures 8 and 9 to fit with clearance over the rectangular studs 2 and 3 respectively.

A brush and cap are then assembled as follows: The top surface 4 and the studs 2 and 3 are first sprayed with metal (e.g. copper) and the cap 5 is then placed on the brush top with the studs 2 and 3 projecting through the apertures 8 and 9.

The free ends 10 and 11 of the studs 2 and 3 are then mechanically deformed, i.e. peened over to rivet the cap to the brush. The cap and the brush top are then soldered to one another; solder covering all the external surfaces of the brush top and cap and flowing by capillary action, between the cap and the brush top surface.

The metallising by plating or spraying with metal and soldering both serve to further improve the electrical connection between the cap 5 and the brush 1.

A pair of flexible current shunts 12 and 13, e.g.

of copper, aluminium or other suitable material, are then attached to the tabs 6 and 7 respectively by any standard engineering technique, such as welding, soldering, crimping, forging or riveting.

CLAIM

A method of making an electrical connection to an electrical brush, having at least one surface portion with a sufficiently high metallic content to render the portion malleable, comprising the steps of forming one or more integral studs upstanding from said surface portion; providing an aperture or apertures in an electrical connector, each to fit with clearance over a peg; placing the connector on the brush with the or each stud projecting through a connector aperture; and deforming the free end of the or each stud to rivet or forge the connector to the brush.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Making connections to electrical brushes This invention relates to a method of making an electrical connection to an electrical brush, e.g. a carbon, metallic or graphitic brush for a dynamoelectric machine. According to the present invention, a method of making an electrical connection to an electrical brush, having at least one surface portion with a sifficiently high metallic content to render the portion malleable, comprises the steps of forming one or more integral studs upstanding from said surface portion; providing an aperture or apertures in an electrical connector, each to fit with clearance over a stud; placing the connector on the brush with the or each stud projecting through a connector aperture; and then deforming the free end of the or each stud to rivet or forge the connector to the brush. A variety of engineering materials can be used for the brush provided the material can be riveted or forged and remains malleable after the connector has been attached to the brush. Generally, to be malleable, the brush surface portion should have a metallic content of approximately 60% by weight. Suitable metallic fillers include copper, iron, tin, steel, lead, aluminium, silver and alloys thereof. In one emobidment of the invention the surface of said portion of the brush is metallised to further improve the electrical connection between the connector and the brush. Alternatively, or additionally, the connector may be soldered to the brush; again to further improve the electrical connection. The advantages of brushes made in accordance with the invention are that it: saves brush material or allows a longer brush to be used in an existing brush assembly; enables larger electrical connections between flexible conducting shunts and the connector to be used and insulated flexibles (if required), both without effecting the operation of ancillary items such as the operating spring; permits connections to be made and terminated from many directions, thus making the entry and size of connection an easy and precise machine operation; increases the mechanical efficiency of the connection permitting maximum wear life with minimum cross-sectional area of the brush, which can be partitioned to allow an airgap for cross brush resistance; increases the thermal efficiency of the connection, thereby reducing brush operating temperatures;; enables a connection to be made with a minimum of tools, allowing on-the-spot repairs to be carried out; and allows brushes and connectors to be assembled by existing engineering methods which can be controlled for quality and mechanised and automated for ease of production. The invention is illustrated by way of example in the Drawings, wherein:- Fig. 1 is a perspective view of a brush formed in accordance with the invention, prior to assembly with a cap; Fig. 2 is a similar view of a cap, prior to assembly with a brush; and Fig. 3 is a cross-section of an assembled brush and cap. As shown, a generally conventional brush 1 , for example formed of a sintered copper-carbon or copper-graphite composition, typically 78% copper, 4.4% graphite, 12.2% litharge, 5.4% ferro manganese alloy (by weight), to have a rectangular cross-section and a concave contact surface, is formed with two rectangular studs 2 and 3 upstanding from the top 4 of the brush. The brush, which may be a one, two or multiple part brush, is first pressed to shape and size and the thus formed pellet is then heat treated to sinter the composite. A generally rectangular metal cap 5, in this example of thick-tin plated mild steel, is preformed to have upstanding tabs 6 and 7 at each end and two rectangular apertures 8 and 9 to fit with clearance over the rectangular studs 2 and 3 respectively. A brush and cap are then assembled as follows: The top surface 4 and the studs 2 and 3 are first sprayed with metal (e.g. copper) and the cap 5 is then placed on the brush top with the studs 2 and 3 projecting through the apertures 8 and 9. The free ends 10 and 11 of the studs 2 and 3 are then mechanically deformed, i.e. peened over to rivet the cap to the brush. The cap and the brush top are then soldered to one another; solder covering all the external surfaces of the brush top and cap and flowing by capillary action, between the cap and the brush top surface. The metallising by plating or spraying with metal and soldering both serve to further improve the electrical connection between the cap 5 and the brush 1. A pair of flexible current shunts 12 and 13, e.g. of copper, aluminium or other suitable material, are then attached to the tabs 6 and 7 respectively by any standard engineering technique, such as welding, soldering, crimping, forging or riveting. CLAIM A method of making an electrical connection to an electrical brush, having at least one surface portion with a sufficiently high metallic content to render the portion malleable, comprising the steps of forming one or more integral studs upstanding from said surface portion; providing an aperture or apertures in an electrical connector, each to fit with clearance over a peg; placing the connector on the brush with the or each stud projecting through a connector aperture; and deforming the free end of the or each stud to rivet or forge the connector to the brush. New claims or amendments to claims filed on 26 August, 1 982. Superseded claim 1. New or amended claims:

1. A method of making an electrical connection to an electrical brush, the brush having at least one surface portion with a sufficiently high metallic content to render the portion malleable, comprising the steps of forming one or more integral studs upstanding from said surface portion; providing an aperture or apertures in an electrical connector, each to fit with clearance over a stud; placing the connector on the brush with the or each stud projecting through a connector aperture; and deforming the free end of the or each stud to rivet or forge the connector to the brush.

2. A method as claimed in claim 1 in which the surface portion of the brush is metallised prior to placing the connector on the brush.

3. A method as claimed in claims 1 or 2 in which the cap and brush top are soldered together subsequent to deforming the free end of the or each stud.

4. A method of making an electrical connection to an electrical brush substantially as described with reference to the drawings.

5. An electrical brush and connector as produced by any of the methods of claims 1 to 4.