AU594022B2

AU594022B2 - Commutator reinforcement system

Info

Publication number: AU594022B2
Application number: AU45246/85A
Authority: AU
Inventors: Rudolf Hanselmann
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-07-24
Filing date: 1985-07-22
Publication date: 1990-03-01
Anticipated expiration: 2005-07-22
Also published as: AU4524685A

Description

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LODGED AT SU3?7"! COMMONWEALTH c A 9 RAA 0 Ar l O1 iCE Patent Act 1952 Patent Act 1952 SC1 ~dney COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class 0* 0 0r r *999r

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o 9g* U 0O *9 .99 *a 9 a a az* Application Number Lodged PG 6194 24 July, 1984 Complete Specification Lodged Accepted Published This document contains the amendments made under Section 49 and is correct for printing.

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MAIL OFFICER......a Priority: Related Art #0 *n 4 o, 0 o 09 *n 9 a so 0 040 a. t 0 "r *4 L t c os ct Name of Applicant Address of Applicant RUDOLF HANSELMANN 6 Franlee Road, Round Corner, New South Wales, Commonwealth of Australia Actual Inventor Address for Service Rudolf Hanselmann F.B. RICE CO., Patent Attorneys, 28A Montague Street, BALMAIN. 2041.

Complete Specification for the invention entitled: "COMMUTATOR REINFORCEMENT SYSTEM" CT«- W< The following statement is a full description of this invention including the best method of performing it known to Me:r r g i:~t r f: 1'11"

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-2 The present invention relates generally to commutators Swherever they are used in particular provides an improved commutator structure and a method for manufacturing commutators according to that structure.

Prior art commutators are of basically two types, one being a high quality product wherein inter-segment insulation of the commutator is provided by mica sheets and the °I individual commutator Iegments are retained in the assembly by armour rings, the assembly being held together by tapered 10 nuts, screwed onto a threaded bush, while in the second type B of commutator, the commutator segments are loaded into the die of an injection moulding machine, with or without a 0 *central bush, and the segments are then moulded into a matrix

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of plastics material, which provides the inter-segment insulation, as well as holding the commutator together.

While the first of these commutator types provides excellent O results, it is relatively expensive to manufacture, whereas e S0-. the second type of commutator is relatively inexpensive but suffers from reduced dimensional accuracy, reduced strength, 20 poor thermal conductivity and are generally less well balanced, resulting in the second type of commutator S~ being generally unsuitable for high speed applications.

S--Aczording to a firSt aSP@Gt, the presenti 1. consists in a commutator comprising a metal bush, a plura ity 5 of commutator segments disposed about said metal b u, a pair of armour rings located around said bush, one f said rings being disposed on either side of said plj ality of segments, each of said armour rings comprisi an annular disc which is attached to said bush and a c entric axial flange directed towards said plurality o egments, the flange of each said armour ring extendi into a co-operating opening in said plurality of s eents and each of the segments, the armour rings and e bush being set in a matrix of insulating mate al such that each segment of the commutator is parated from the two adjacent segments, thP pair nf armp-,r AL1 L 2a According to a first aspect, the present invention provides a commutator comprising a metal bush, a plurality of commutator segments disposed about said metal bush, a pair of armour rings coaxial with said bush, the bush extending through and of the rings, said plurality of segments being located between said pair of armour rings, each of said armour rings comprising an annular disc which is coaxial with and attached to said bush and a concentric axial flange directed towards said plurality of segments, the flange of each said armour ring extending into a co-operating opening in said plurality of segments and each of the segments, the armour rings and the bush being set in a matrix of insulating material such that each 5 segment of the commutator is separated from the two 15 adjacent segments, the pair of armour rings and the bush by said insulating material.

.According to a second aspect, the present invention provides a method of manufacturing a commutator, said J method comprising the steps of: forming a ring of commutator segments; placing a bush in the centre of said ring of segments; attaching a pair of armour rings to said bush, said 'p ,ring of segments being located between the pair of the c cc armour rings projecting into openings in the segments to retain the segments about said bush; placing the assembly of segments, armour rings and bush into the die of a moulding machine; and injecting a matrix of plastics material into the Bspaces formed between adjacent segments of said ring and

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c ~30 into spaces formed between said segments and the armour rings and between said segments and bush.

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0O ft ft 00 ft ft* o Oft 00 0 000 0 0000 ft C OftO a @o 00 C ft o #0 oo eq a ft ft ftaO rings and tcbush by' said incul ating matcriJal According to a second aspect, the present inventio consists in a method of manufacturing a commutator, id method comprising the steps of forming a ring o commutator segments; placing a bush in the centre of s ring of segments; attaching a pair of armour ri s to said bush, one armour ring being disposed on ther side of said ring of segments, the armour ring engaging openings in the segments 10 to retain the segment -'about said bush; placing the ssembly of segments, armour rings and bushi into the die fa moulding machine; and inj ting a matrix of plastics material into the spaces between adjacent segments of said ring and into spaces An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in Fig,. 1 illustrates part of an end view of a. commutator 20 according to the present invention; and Fig. 1.Fig. 2 illustrates a view through section line A-A of Referring to the drawings, a commutator made in accordance with the present invention comprises a central metal bush 10, surrounded by a plurality of commutator segments 11 each of which is separated by an inter-segment gap 12. A pair of armour rings 13 are provided, comprising an annular disc 14 and an axial flange 15 adapted to hold the commutator segments 1.1 captive about the bush 10, each flange 15 extending into one of a pair of openings 16 provided in the side of each of the commutator segments 11. The armour rings 13 are sized to attach to the bush 10 such that the armour rings are maintained in position on the bush during assembly of the commutator and such that good thermal conduction is provided between the armour rings a nd the ,~ft a ft ftO Oft ft. a ft.

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7 -4bush. In the embodiment illustrated, the armour rings 13 are pressed onto the bush The inter-segment gaps 12 and the spaces between the segments 11 and the armour rings 13 and bush 10 are filled with a plastics material 17 which is moulded into the assembly of the commutator to act as a matrix which holds the segments of the commutator in the correct spatial *arelationship. An undercut region 18 is provided in each inter-segment gap 12, in which the plastics material 17 is 1 0 absent, however, such undercut regions are not essential and 0 0 may not always be provided.

In order to manufacture the commutator illustrated in Figs. 1 and 2, a plurality of commutator segments 11 are eoo placed in a ring about a bush 10 and a pair of armour rings 13 are attached to the bush to hold the commutator rings captive. The assembly of bush armour rings and commutator segments is then placed into a die of a moulding apparatus, "such as an injection moulding machine, gravity die moulding '0 5 apparatus or other suitable moulding apparatus, the 20 commutator segments and the bush being held in the correct spatial relationship by the die, and the matrix of plastics material 17 is then placed into the commutator assembly to Sset the components of the assembly in position. The assembly It .o P of the present invention has the advantage that, because the armour rings are attached to the central bush, location of the armour rings in the assembly during moulding is achieved by locating the bush within the die of the moulding machine and therefore, the problem experienced with prior art commutators, wherein the armour rings tended not to be centrally located, is avoided.

The provision of armour rings which are in mechanical I' ,contact with the central metal bush 10 also provides reduced thermal resistance between the outer surface of the commutator and the bush, thereby allowing better conduction of heat and reduced temperature rise in the commutator. Further, due to ai-: 1 4 -L :i 6p ry Riv .1 1 0 '44 0 0 0000 0*00 '4 0000 00 0 00 00 o 00 00 0 000 0 0000 0 0000 0 00 0 4' 000 0 0 00 00 0 0 00 00 14*0 00 4' 0 0* 0 0 00 0* greater dimensional accuracy and increased dimensional stability of the assembly, operation of the commutator at higher speeds and temperatures is possible, speeds of 60,000 to 70,000 rpm being achieved with the commutator of the present invention, whereas prior art moulded commutators were typically limited to speeds of 20,000 rpm or lower. The improvement in dimensional stability and accuracy also allows a reduction in insulation thickness for a given electrical resistance, which in turn provides a further reduction in 10 thermal resistance.

It will be seen from the above discussion that the commutator of the present invention has many of the advantages of the prior art compression sleeve commutator while maintaining the advantage of lower production cost achieved by moulded commutators.

It will be recognised by persons skilled in the art that numerous variations and modifications may be made to the invention as described above without departing from the spirit or scope of the invention as broadly described.

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Claims

1. A commutator comprising a metal bush, a plurality of commutator segments disposed about said metal bush, a pair of armour rings coaxial with said bush, the bush extending through and of the rings, said plurality of segments being located between said pair of armour rings, each of said armour rings comprising an annular disc which is coaxial with and attached to said bush and a concentric axial flange directed towards said plurality of segments, the flange of each said armour ring extending into a co-operating opening in said plurality of segments and each of the segments, the armour rings and the bush being set in a matrix of insulating material such that each segment of the commutator is separated from the two adjacent segments, the pair of armour rings and the bush by said insulating material.

2. The commutator of claim 1, wherein the bush comprises a metal tube.

3. The commutator of claim 2, wherein the inner diameter of the armour rings is a press fit on said bush and the commutator is assembled by pressing the armour rings onto respective ends of the bush. 4 -he commuatoaccording to any S; wherein said axial flange extends from the peripheral e C Cof the armour ring. The commutator according to any one of t preceding S"claims, wherein each commutator segment miprises a body C 'I portion, a first pair of flanges ex nding axially of the S commutator from either side of ne end of the body portion to provide a brush contac gng surface, and a second pair o f flanges extendin xially of the commutator from either Sside of the ot end of the body portion to provide retaining eans arranged to engage with the armour ring in Sthe ent of failure of the matrix material, respective L; L 6a

4. The commutator according to any one of claims 1 to 3 wherein said axial flange extends from the peripheral edge of the armour r-ng.

The commutator according to any one of the preceding claims, wherein each commutator segment has an inner and outer side and comprises a body portion, a first pair of flanges extending axially of the commutator segment from either end of the outer side of the body portion to provide an extended brush contacting surface, and a second pair of flanges extending axially of the commutator segment from either end of the inner side of the body portion to provide retaining means arranged to engage with the armour ring in the event of failure of the matri:. >material, respective spaces between said first and second 2? pairs of flanges defining said openings into which the axial flanges of the armour rings extend. c c C I ui 4 1 .l 1 1 m i i t r- 4 de.ifiing aid opening .into .hich .h ax.ial f!angs. oF t- armou.c ring oxtend.

6. The commutator of claim 5, wherein the first pair of flanges are longer than the second pair of -flanges and the armour rings are located radially inwardly of respective ones of said first flanges.

7. A method of manufacturiig a commutator, said method comprising the steps of: forming a ring of commutator segments; placing a bush in the centre of said ring of segments; attaching a pair of armour rings to said bush, said ring of segments being located between the pair of the armour rings projecting into openings in the segments to retain the segments about said bush; placing the assembly of segments, armour rings and bush into the die of a moulding machine; and injecting a matrix of plastics material into the spaces formed between adjacent segments of said ring and into spaces formed between said segments and the armour rings and between said segments and bush.

8. A commutator substantially as hereinbefore described with reference to the acc:.mpanying drawings.

9. A method of manufactacing a commutator as claimed in claim 7, substantially as hereinbefore described. Dated this 29 day of November 1989 9 9 p 9 9* a 9* 9. C E t p CIa 14CC C C t 4 C 94tC~C C *64 CCC C *CC.C Ce 61 CC RUDOLF HANSELMANN By: Registered Patent Attorney <1 'V