AU724875B2 - Brushes - Google Patents

Description

Regulation 3.2 AUST R A LIA Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

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5* Name of Applicant: Actual Inventor(s): Address for Service: Invention Title: JOHN NICHOLAS WALTRICH JOHN NICHOLAS WALTRICH SANDERCOCK COWIE 69 Robinson Street, DANDENONG VIC 3175

BRUSHES

Details of Associated Provisional Application(s): No(s): Australian Provisional Application No. P02806 The following statement is a full description of this invention, including the best method of performing it known to me/us: 1 97 1001msdat. VS.WALTRICHAU,I la-

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*FIELD OF THE INVENTION This invention relates to brushes.

BACKGROUND TO THE INVENTION It is the usual practice in many electric motors to conduct electric current to the motor via brushes which engage with a commutator.

In due course, the commutator becomes dirty and it is necessary to use a commutator stone or some other means to clean the commutator. This last is usually done by replacing the brushes one at a time by the commutator 97093pnsdat.123,waitrichcap,1 2 stone. Such commutator cleaning or polishing stones are usually the same size as the brushes normally used on a particular motor.

However, there is another problem with electric motors in that in due course the brushes wear down and when this occurs various things associated with the brushes, such as brush holders, brush springs or electric cables carrying electric current to the brushes, can scrape against the commutator and damage it.

The problem is, however, to know when to replace brushes as too early replacement involves wastage of part of each brush plus downtime and service person costs and too late 15 replacement causes damage to the commutator.

Thus, in practice, electric motors need to be inspected 'regularly to ensure that the brushes have not worn down too much. Much of such inspection is wasteful and of no value 20 but the inspection is done as the alternative of not regularly inspecting can lead to damage.

Applicant is aware of an electronic device which is capable •of warning when brush wear exceeds a certain limit but the device is very expensive and would really only be feasible S" in respect of very large electric motors and associated equipment where the cost would represent only a small fraction of the cost of the a whole motor.

Accordingly, the applicant has considered alternative ways of determining when brush wear exceeds a predetermined amount.

SUMMARY OF THE INVENTION The present invention provides:- 97093XcmsdatU3,waItrUkh.sp2 3 a brush having a first end adapted for contacting a commutator of an electric motor, a second end adapted for forming an electrical connection for the conduction of electricity from a source of electricity to the brush and thence to the commutator, and a body of marking material having an end spaced a predetermined distance from said first end whereby, in use, when the brush has worn in use by said distance, said marking material will come into contact with 15 the commutator and act on the commutator whereby to give a S: visual indication of wear.

•PREFERRED ASPECTS OF THE INVENTION 20 Preferably the marking material has a width less than the width of the brush so as to only act on the commutator in a band.

Such a band should desirably show up in marked contrast to 25 darker areas of the commutator.

In general, it is preferred that the marking material is one quarter or less of the width of the brush.

The marking material may be located in the middle or on a side of the brush.

More preferably, the marking material is located in a hole in the brush.

That hole may be a specially formed hole.

970930xansdat.,w9tricxcap3 4 However, since it is usual to provide holes in brushes in which an electrical cable (often called a pigtail) is inserted, Applicant prefers to locate the marking material at the bottom of that hole.

The marking material may be forced into place but being held in place with an adhesive is preferred.

Suitable adhesives are known for bonding pigtails to brushes and may be used to hold the marking material.

Those adhesives are usually electrically conductive or contain an electrically conductive material. A suitable electrical conductive material is graphite powder.

15 The marking material is preferably the same material as is used for commutator stones for cleaning and polishing.

The shape of the marking material is not critical but Applicant prefers to use a cylinder as this is easily 20 formed and can be easily located in a hole in the brush.

The marking material is preferably a polishing or an abrasive material.

A specific embodiment of brushes in accordance with this •e invention will now be described with the aid of the accompanying drawings which are given by way of example only.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS Figure 1 is a schematic representation of a first brush in accordance with this invention, Figure 2 is a schematic representation of a second brush in accordance with this invention, and 970930,nsda.23,waltrkcap.4 5 Figure 3 is a schematic representation of a third brush in accordance with this invention.

INTEGER LIST 1. First brush 2. Second brush 3, Third brush 21. Commutator end 22. Commutator end 23. Commutator end 31. Pigtail end 32. Pigtail end 33. Pigtail end 15 41. Pigtail 42. Pigtail 43. Pigtail 51. Pigtail hole 52. Pigtail hole 20 53. Pigtail hole 54. Additional hole Stone 56. Spring 57. Closure cap 58. Additional hole 59. Stone Closure cap Stone DETAILED DESCRIPTION WITH RESPECT TO THE DRAWINGS The first brush 1 shown in Figure 1 has a commutator end 21 which will normally contact a commutator of an electric motor and a pigtail end 31 to which a pigtail 41 is fitted in a pigtail hole 51.

In addition, the first brush 1 has an additional hole 54.

97o93pnsdat.M3waltrh.cap.5 6 At the bottom of the hole 54 is a stone 55 which is urged towards the bottom by a spring 56 and which spring is kept in place by a closure cap 57.

It is to be noted that the additional hole 54 is deeper than the pigtail hole 51 and in consequence when the brush has worn sufficiently, the stone 55 will make contact with the commutator and polish or clean the commutator in a region which will be detectable in a narrow polished or cleaned band against a darker background.

The second brush 2 has a commutator end 22 and a pigtail end 32.

15 A pigtail 42 is located in a pigtail hole 52.

The brush 2 has an additional hole 58 in which is located a stone 59. The hole 58 is closed by a closure cap "20 Once again, the additional hole 58 is deeper than the pigtail hole 52.

The second brush 2 will operate in similar manner to the first brush 1.

The third brush 3 shown in Figure 3 has a commutator end 23, a pigtail end 33, and a pigtail 43 which is located in a pigtail hole 53.

In this instance, however, there is no additional hole and rather a stone 65 is located at the bottom of the pigtail hole, which may need to be made deeper than usual to accommodate the stone.

In this instance the stone 65 was held in place by means of an adhesive and containing graphite powder.

97093Onsdat.123,watrichcapA 7 The above described brushes have been found to work quite satisfactorily and will give a good visual indication of brush wear.

The claims, illustrations, photographs and drawings, if any, form part of the disclosure of this specification as does the description, claims, illustrations, photographs and drawings of any associated provisional or parent specification or of any priority document, if any, all of which are imported hereinto as part of the record hereof.

Finally it is to be understood that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements or parts without 15 departing from the spirit and ambit of the invention.

V 97093,asdat.123,waItich-aP,7

Claims (6)

1. 2. A brush as claimed in Claim 1, wherein the marking :material has a width less than the width of the brush oo so as to only act on the commutator in a band. 25 3. A brush as claimed in Claim 1 or Claim 2, wherein the marking material is such as to show up in marked contrast to other areas of the commutator.
2. 4. A brush as claimed in any preceding claim, wherein the 30 marking material is one quarter or less of the width of the brush. A brush as claimed in any preceding claim, wherein the marking material is located on a side of the brush. 00628,cmsdat. I 23,waltric.cap,8
3. 9- 6. A brush as claimed in any one of Claims 1 to 4, wherein the marking material is located in a hole in the brush. 7. A brush as claimed in any one of Claims 1 6, wherein the brush has a pigtail hole and the marking material is located in the bottom of that hole. 8. A brush as claimed in any preceding claim, wherein the marking material is forced into place. 9. A brush as claimed in any one of Claims 1 to 7 wherein the marking material is held in place with an adhesive. A brush as claimed in any preceding claim, wherein the marking material is a polishing material.
4. 11. A brush as claimed in any preceding claim, wherein the 20 marking material is an abrasive material.
5. 12. A brush as claimed in any preceding claim, substantially as described with reference to any one of the accompanying drawings.
6. 13. A brush substantially as hereinbefore described with reference to any one of the accompanying drawings. Dated this 2 8 th of June, 2000. SANDERCOCK COWIE PATENT ATTORNEYS FOR IF JOHN NICHOLAS WALTRICH 00628,cmsdat. I23,watrich.cap,9