A BRUSH WEAR INDICATOR

Abstract

Disclosed herein is a brush wear indicator comprising and brush (3) moveable within a holder (2). The brush (3) is urged against a collector surface (10) of a rotor by a spring (4) which is mounted to a bracket (6) supported by the holder (2). A proximity sensor (5) is mounted to either a) the spring (4) or the brush (3), or b) a non-moveable part of the indicator which includes the bracket and configured to determine the distance to a) the non-moveable parts or b) the spring (4) or brush (3), respectively. The proximity sensor (5) in electrical communication with a CPU configured to determine the amount of wear that has occurred to the at least one brush (3) depending on the distance determined by the sensor (5) between the spring (4) or the brush (3) and the non-moveable parts.

Claims

1. A brush wear indicator comprising: a brush holder; a brush located within the brush holder; a spring in contact with the at least one brush and configured to bias the brush against an electrically conductive collector surface, the spring and the brush being moveable in use; a proximity sensor mounted to either a) the spring or the brush, or b) a non-moveable part of the indicator, said proximity sensor being configured to determine a distance from the proximity sensor to the non-moveable part or to the spring or brush, respectively; the non-moveable part including a bracket supported by the holder; the proximity sensor being in electrical communication with a CPU that is configured to determine an amount of wear that has occurred to the brush according to the distance determined by the sensor between the spring or the brush and the non-moveable part.

2. The brush wear indicator according to claim 1, wherein the proximity sensor and/or the spring are mounted on the bracket.

3. The brush wear indicator according to claim 1, wherein the bracket is attachable to the holder.

4. The brush wear indicator according to claim 1, wherein the bracket comprises a resiliently deformable portion mounted between inside surfaces of the holder.

5. The brush wear indicator according to claim 1, wherein the sensor is directed at either the spring or the brush.

6. The brush wear indicator according to claim 1, wherein the sensor is directed at the bracket.

7. The brush wear indicator according to claim 1, wherein the spring is any of a coil spring, a constant force spring, a V shaped clip spring, a bayonet spring, a sugar tong spring, a bobbin spring, a helical spring, a torsion spring, a calliper spring, a clock spring, and a cassette mechanism spring.

8. The brush wear indicator according to claim 1, wherein the proximity sensor is either a laser sensor or an ultrasound sensor.

9. The brush wear indicator according to claim 1, wherein the brush is a carbon brush.

10. The brush wear indicator according to claim 9, wherein the brush comprises a metal that increases its conductivity.

11. The brush wear indicator according to claim 1, wherein the brush is any of a monobloc brush, a multi-wafer brush, a multipart brush, a split brush, a wire brush, a calliper brush, and a fibre brush.

12. The brush wear indicator according to claim 1, wherein the holder is any of a radial holder, a trailing holder, a reaction holder, a tandem holder, a cantilever holder, a cartridge holder, and a calliper holder.

13. The brush wear indicator according to claim 1, wherein the collector surface is a surface of a generator, a motor, or a rotor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows a cross sectional view of an embodiment of the brush wear indicator and

[0033] FIG. 2 shows a perspective view of the bracket as embodied within FIG. 1.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

[0034] FIG. 1 shows a cross sectional view of an embodiment of the brush wear indicator generally designated 1. The indicator is made up of a holder 2, a brush 3, a coil spring 4, and a laser proximity sensor 5. The holder 2 is a brass tube having a rectangular cross section with two adjacent pockets 2a and 2b. One side 2c of the pocket 2b is sloped. Other material for the holder could be used though and these include aluminium, steel or polymers. The brush 3 fits inside the pocket 2a of the holder 2 and is able to move freely therein backwards and forwards from and to the rotating collector surface 10, which in this example is on a rotor of a generator. The brush 3 is a relatively tight fit within the pocket 2a, in order that movement within the pocket is not hindered by lateral forces which the brush experiences when in contact with a rotating collector surface 10, or a collector surface 10 which is moving laterally underneath the brush, or the brush moving with respect to the static collector surface 10. The brush 3 is a carbon brush. In use the holder 2 with the brush 3 therein is mounted adjacent the rotating collector surface 10 of a generator. As indicated by the arrows, the collector surface 10 may rotate both clockwise and anticlockwise. In some examples though the collector surface 10 rotates unidirectionally. In other examples the indicator 1 is substantially as described but the collector surface 10 is linear, such as that on a railway line. One end 3a of the brush 3 is positioned in contact with the collector surface 10 at a bearing surface of the collector surface 10 which is electrically conductive.

[0035] The brush 3 is in electrical communication with a power unit (not shown) and in use electrical power is delivered through wires (not shown) from the power unit to the brush 3 and then from the brush 3 to the collector surface 10. The current is transmitted through the brush by wires which are tamped, rivetted, soldered, bolted or clamped.

[0036] The coil spring 4 is a steel coil spring and has one end mounted to a bracket 6 adjacent the opposite end 3b of the brush 3. The spring 4 bears against the end 3b of the brush 3 and urges the end 3a of the brush 3 into engagement with the collector surface 10. As the collector surface 10 rotates it wears the end 3a of the brush 3 away. As the brush 3 wears away the spring uncoils as it does so, maintaining contact with the end 3b of the brush. The main coil of the spring 4 therefore moves with the end 3b of the brush 3. The distal surface of the spring 4 (i.e. the part from the spring farthest away from the collector surface 10), will also move but somewhat less, as expected from a coil spring that uncoils. It will be appreciated that in other examples where different types of springs are used, the degree of movement of the spring at one end compared to that of the other follows the same pattern.

[0037] Unchecked the spring 4 will continue to urge the brush 3 into engagement with the collector surface 10 until all of the brush 3 has worn away, thereby causing failure of the brush 3, at which point the electrical connection through the brush 3 to the collector surface 10 would be compromised and the electrical continuity lost.

[0038] In order to determine the wear on the brush 3 a laser proximity sensor 5 is mounted to a protrusion 7 at the distal end of the bracket 6, (that is the end farthest away from the collector surface 10). The sensor 5 is directed to the end 3b of the brush 3, but may also be directed to the distal surface of the spring 4. The sensor 5 measures the distance between the sensor 5 and the brush 3, or the spring 4, which ever it is arranged to do. As the brush 3 wears in use, the distance measured gets greater. The sensor 5 is in electrical communication with a central processing unit, which calculates the wear on the brush 3 from the distance measured. The wear data is transmitted by wires or wirelessly using conventional data transfer methodologies to a remote station, where the user can monitor the wear on the brush 3 or detect for failure.

[0039] The bracket 6 may simply bolt or clip onto a side of the holder 2. In the example shown the bracket 6 is V shaped, and is made of spring steel. The spring 4 and the sensor 5 are mounted on one side of the bracket 6 and the V portion 8 of the bracket 6 extends on the opposite side. In use the bracket 6 is inserted into the pocket 2b of the holder 2. The bracket 6 has a protrusion (not shown) which fits into a matching recess (not shown) in wall 2c the holder 2. In use the resiliently deformable portion deflects as the bracket 6 is introduced into the holder 2 until the recess and the protrusion engage, at which point the resilient nature forces a tight fit of the two parts together. The resilient nature of the bracket 6 makes sure that the protrusion is held within the recess and therefore that the bracket is held firmly against the inside of the pocket 2b of the holder 2. The bracket 6 is thus fixed in place and serves therefore to hold the spring 4 and the sensor 5 in position, whilst the spring 4 urges the brush 3 against the collector surface 10. Another benefit of the V shaped bracket 6 is that when the brush 3 requires replacement it can be simply clamped together therefore disengaging the protrusion from the recess, and pulled out, the brush 3 replaced and then reinserted, with the act of reinsertion causing the coiling of the spring 4 under tension as it does so, thereby forcing the brush 3 into engagement with the collector surface 10.

[0040] In another example of the invention there is an indicator substantially as described above, but the sensor 5 is mounted onto the end 3b of the brush 3. The sensor 5 is directed to the protrusion which is in a fixed position relative to the brush 3 and the sensor 5. In this case it is the sensor 5 that moves, but the distance measurement methodology is the same.

[0041] In another example of the invention there is an indicator substantially as described above, but the sensor 5 is mounted onto the spring 4. The sensor 5 is directed to the protrusion which is in a fixed position relative to the spring 4 and the sensor 5. In this case it is the spring 4/sensor 5 that moves, but the distance measurement methodology is the same.

[0042] It will be understood that the laser sensor 5 described above may be replaced for an ultrasound sensor 5.

[0043] The holder 2 described above is a radial type holder. The holder 2 used with the indicator may be of a number of different types however which are all provided as examples herein. In each example the indicator is substantially as described above but differs in the aspects that the holder is a trailing holder, reaction holder, tandem holder, cantilever holder, cartridge holder or calliper holder

[0044] Whilst in the examples provided above the brush 3 is used for power transfer, it may also be used to transfer data in the form of electrical current from the collector surface 10 through the brush 3 and then to a data collection unit (not shown) and vice versa. The current in this sense therefore may be described as electrical signals.

[0045] In another example the indicator 1 is substantially as described above however the collector surface 10 is a linear U or V shaped track. The brush 3 and the holder 2 are mounted to a movable object such that the brush engages within the U or V shaped track and such that the brush 3 moves up and down the track laterally. This enables current and signal transfer between the part holding the collector surface and the part holding the holder 2 which are moving laterally with respect to one another. In this example there may be a plurality of tracks/collector surfaces and therefore a corresponding number of indicators engaged therein.

[0046] In another example of the invention there is an indicator 1 as described above except the collector surface is provided at least one electrically conductive ring on the top of a rotating door. The ring is centred on the central axle of the door. The indicator 1 is mounted to an arm above the door. The brush 3 is mounted within the holder 2 of the indicator 1. The brush 3 bears against the collector surface 10 as the door rotates, and current is transferred between the door and the indicator. This installation is typical in faceplate or flat slip ring in a rotating door.