GB2047478A - Contact brush for commutators - Google Patents

Abstract

A contact brush has means for lifting it from a commutator or the like when, due to wear, the brush becomes inefficient or prejudicial to operation of associated equipment, and comprises a spring-loaded plunger (10) accommodated in a recess in the top of the brush (12), so that when the brush is worn down the plunger breaks through and protrudes from the bottom of the recess so lifting the brush. The remote end (13a) of the spring may be held in a circular or helical groove in a self-tapping capsule (11) screwed into the end of the brush or, alternatively, by a disc held in the groove; or the spring may be screwed directly into the brush. <IMAGE>

Description

SPECIFICATION Electrical contact brush This invention relates to electrical contact brushes made of carbon or a similarly wearable conductive material, e.g. a metal-graphite mix, and provides such a brush with built-in means for lifting the brush out of contact with a relatively movable contacted surface, such as of a commutator, when the brush has worn down to a condition beyond which continued use would be inefficient or prejudicial to operation of the equipment concerned.

According to the invention, such an electrical contact brush is provided, in the head thereof, with a recess in which is located an insulating plunger spring-loaded towards the contact face of the brush so that when recession of the contact face, due to wear in use, almost reaches the base of the recess the plunger, under the thrust of its spring-loading, can break through and protrude from the contact face to lift the brush out of contact with the contacted commutator or other surface.

Conveniently, the plunger is contained within a capsule which is formed externally with ribbing to key into the wall of the recess in the brush.

In one form, the ribbing is helical being provided for example by the screw-thread of a self-tapping screw which can be threaded into a hole of appropriate size drilled in the top of the brush.

In another form, the capsule is formed by a closely-wound helix of metal wire, preferably consolidated by immersion in solder or by coating with metal by electroplating. In this case the capsule can be compacted into the brush at the time of pressing the brush in manufacture.

The plunger may be loaded by a spring retained in the capsule in any of a number of simple ways. For example, the capsule may have an internal circular groove in its top end, or an internal helical groove, the spring having its end remote from the plunger flared to engage in, and be retained by, the groove.

Another feature facilitates attachment of a flexible conductor to the brush. The spring abuts a thin disc pressed into the capsule to leave a cavity which is filled, as by tamping in conductive powder, with conductive material which retains the end of the conductor.

The accompanying drawings show three examples of brush in diagrammatic section.

In Figs. 1 and 2, the insulating plunger 10 is in a capsule 11 which has external ribbing 11 a of the self-tapping thread type to retain it in a hole drilled in the brush 1 2. The capsule also has an internal helical groove 11 b. A loading spring 1 3 for the plunger 10 has its end 1 3a remote from plunger 10 flared to a larger diameter than the minimum diameter of the capsule bore so that when the spring is pressed into the bore the flared end enters the groove 11 b and is retained under compression.

In Fig. 2, there is shown means for securing a flexible conductor 1 4 to the brush. The means in this case comprises a thin disc 1 5 which seals off the capsule bore above the spring 1 3 and compactable conductive powder 1 6 filling the end of the bore above the disc, the end of the conductor being embedded in, and thus retained by, the compacted powder.

In Fig. 3, the capsule 1 7 is a closely-wound helix of wire which is consolidated and retained in the brush 1 2 by the latter being pressed around the capsule. The loading spring can be retained as shown in Figs. 1 and 2.

In other arrangements a flexible conductor is secured to the capsule by soldering or welding.

1. An electrical contact brush provided in the head thereof with a recess in which is located an insulating plunger and a spring loading the plunger towards the contact face of the brush so that, when recession of the contact face due to wear in use almost reaches the base of the recess, the plunger under the thrust of the spring loading can break through and protrude from the contact face to lift the brush out of contact with a contacted commutator or the like.

2. An electrical contact brush according to claim 1, wherein the plunger is contained within a capsule which is formed externally with ribbing to key into the wall of the recess in the brush.

3. An electrical contact brush according to claim 2, wherein the ribbing is helical.

4. An electrical contact brush according to claim 3, wherein the ribbing is provided by the screwthread of a self-tapping screw which can be threaded into a hole of appropriate size drilled in the top of the brush.

5. An electrical contact brush according to claim 2; wherein the capsule is formed by a closely-wound helix of metal wire.

6. An electrical contact brush according to claim 5, wherein the helix is consolidated by immersion in solder or by coating with metal by electroplating.

7. An electrical contact brush according to claim 5 or 6, wherein the capsule is retained by compaction of the brush material.

8. An electrical contact brush according to any of claims 2 to 7, wherein the spring for loading the plunger is retained in the capsule by the capsule having an internal circular groove or helical groove and by the spring having its end remote from the plunger flared into retaining engagement with the groove.

9. An electrical contact brush according to

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

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electrical contact brush This invention relates to electrical contact brushes made of carbon or a similarly wearable conductive material, e.g. a metal-graphite mix, and provides such a brush with built-in means for lifting the brush out of contact with a relatively movable contacted surface, such as of a commutator, when the brush has worn down to a condition beyond which continued use would be inefficient or prejudicial to operation of the equipment concerned. According to the invention, such an electrical contact brush is provided, in the head thereof, with a recess in which is located an insulating plunger spring-loaded towards the contact face of the brush so that when recession of the contact face, due to wear in use, almost reaches the base of the recess the plunger, under the thrust of its spring-loading, can break through and protrude from the contact face to lift the brush out of contact with the contacted commutator or other surface. Conveniently, the plunger is contained within a capsule which is formed externally with ribbing to key into the wall of the recess in the brush. In one form, the ribbing is helical being provided for example by the screw-thread of a self-tapping screw which can be threaded into a hole of appropriate size drilled in the top of the brush. In another form, the capsule is formed by a closely-wound helix of metal wire, preferably consolidated by immersion in solder or by coating with metal by electroplating. In this case the capsule can be compacted into the brush at the time of pressing the brush in manufacture. The plunger may be loaded by a spring retained in the capsule in any of a number of simple ways. For example, the capsule may have an internal circular groove in its top end, or an internal helical groove, the spring having its end remote from the plunger flared to engage in, and be retained by, the groove. Another feature facilitates attachment of a flexible conductor to the brush. The spring abuts a thin disc pressed into the capsule to leave a cavity which is filled, as by tamping in conductive powder, with conductive material which retains the end of the conductor. The accompanying drawings show three examples of brush in diagrammatic section. In Figs. 1 and 2, the insulating plunger 10 is in a capsule 11 which has external ribbing 11 a of the self-tapping thread type to retain it in a hole drilled in the brush 1 2. The capsule also has an internal helical groove 11 b. A loading spring 1 3 for the plunger 10 has its end 1 3a remote from plunger 10 flared to a larger diameter than the minimum diameter of the capsule bore so that when the spring is pressed into the bore the flared end enters the groove 11 b and is retained under compression. In Fig. 2, there is shown means for securing a flexible conductor 1 4 to the brush. The means in this case comprises a thin disc 1 5 which seals off the capsule bore above the spring 1 3 and compactable conductive powder 1 6 filling the end of the bore above the disc, the end of the conductor being embedded in, and thus retained by, the compacted powder. In Fig. 3, the capsule 1 7 is a closely-wound helix of wire which is consolidated and retained in the brush 1 2 by the latter being pressed around the capsule. The loading spring can be retained as shown in Figs. 1 and 2. In other arrangements a flexible conductor is secured to the capsule by soldering or welding. CLAIMS

1. An electrical contact brush provided in the head thereof with a recess in which is located an insulating plunger and a spring loading the plunger towards the contact face of the brush so that, when recession of the contact face due to wear in use almost reaches the base of the recess, the plunger under the thrust of the spring loading can break through and protrude from the contact face to lift the brush out of contact with a contacted commutator or the like.

2. An electrical contact brush according to claim 1, wherein the plunger is contained within a capsule which is formed externally with ribbing to key into the wall of the recess in the brush.

3. An electrical contact brush according to claim 2, wherein the ribbing is helical.

4. An electrical contact brush according to claim 3, wherein the ribbing is provided by the screwthread of a self-tapping screw which can be threaded into a hole of appropriate size drilled in the top of the brush.

5. An electrical contact brush according to claim 2; wherein the capsule is formed by a closely-wound helix of metal wire.

6. An electrical contact brush according to claim 5, wherein the helix is consolidated by immersion in solder or by coating with metal by electroplating.

7. An electrical contact brush according to claim 5 or 6, wherein the capsule is retained by compaction of the brush material.

8. An electrical contact brush according to any of claims 2 to 7, wherein the spring for loading the plunger is retained in the capsule by the capsule having an internal circular groove or helical groove and by the spring having its end remote from the plunger flared into retaining engagement with the groove.

9. An electrical contact brush according to any of claims 2 to 8, wherein the spring abuts a thin disc pressed into the capsule to leave a cavity which is filled with conductive materials which retains the end of a flexible conductor.

1 0. An electrical contact bush according to any of claims 2 to 8, wherein a flexible conductor is secured to the capsule by soldering or welding.

11. An electrical contact brush substantially as hereinbefore described with reference to and as illustrated in Fig. 1 or Fig. 2 or Fig.

3 of the drawings.