US3450914A - Commutators of rotary electric machines - Google Patents

Description

COMMUTATORS OF ROTARY ELECTRIC MACHINES FiG.1- 3

Filed June 9, 1966 Sheet I of 2 2 FI G.2 9v

1+ 2 3 5 6 FIG.3 1 ,X,

June 17, 1969 J. DEMERCIERE COMMUTATORS OF ROTARY ELECTRIC MACHINES 2 of 2 I Sheet Filed June 9, 1966 FiG.4.

United States Patent Int. (:1. H01r 39/04 US. Cl. 310-236 6 Claims ABSTRACT OF THE DISCLOSURE A communtator for rotary electrical machines having a sleeve on which are mounted a plurality of similar radial conductive elongated bars with interposed insulating plates separating successive bars. Each bar has a notch in its inner edge, which extends at least in part within the body of the bar to form a tongue therein along the edge. At one radial end of the bar is a further notch and at the other end is a radial outwardly directed extension and a lateral projection, the latter having an outline matching that of the further notch and being disposed at the same level thereof. An insulating body is secured to the sleeve and fills the notches and encloses the projections of the bars, there being rings imbedded in the insulating body and fitted in corresponding notches of the different bars and extending around the lateral projections on the different bars.

The bars or strips of molded and reinforced commutators in motors and the like rotary electric machines are generally fitted round a central sleeve by means of metal rings housed in pairs in one or more notches having a T-shaped outline and which are provided in the inner central section of each bar, the insulation between the bars and their carrier rings being obtained by molded or injected insulating material.

The collar provided at one end of certain commutators for the electric connection between the windings and the bars produces in registry with the location of the collar a considerable increase in the centrifugal force, which has a tendency to tear the bars'out of their housings.

In order to eliminate this drawback, the bars have been provided at said end with a terminal notch adapted to be engaged b a further ring.

However, the reduction in the thickness of the metal between said terminal notch and the above mentioned T-shaped notch reduces considerably the clamping action on each bar so that the increase in the rotary speed allowed by said further ring is quite inconsiderable.

My invention has for its object to remove this drawback and, to this end, it improves the commutators of the above-mentioned type for all rotary electric machines. According to my invention, each bar includes in its radially inner surface one or more notches having a T- shaped or bayonet outline and adapted to engage one or more bar-retaining rings while said bar is also provided in said radially inner surface with a projection extending laterally beyond the connection-carrying collar and adapted to be engaged outwardly by a retaining ring of a larger diameter than the first mentioned rings, the bar being provided finally at its end facing away from said collar with a notch formed endwise and adapted to engage a further bar-retaining ringj Thus, the difference in diameter between the outer ring engaging the lateral projection and the nearest of the firstmentioned rings at a point in registry with the connectioncarrying collar allows maintaining a large cross-section for the retaining lugs formed on the bar between the notches formed in it in the area which is subjected to the maximum tearing out stresses and wherein the bars are held in position b a double engagement with retaining rings,

In an advantageous embodiment, the notch formed endwise in each bar on the side facing away from the collar is given the same outline as the projection provided on the side facing the collar. I obtain thus a substantial economy in metal since the metal obtained by the cutting out of the endwise notch in one bar may form the projection of a bar produced in immediate sequence.

The electrical insulation of the bars with reference to the metal rings is ensured by molded or injected insulated material introduced after the rings have been precedingly centered by means of insulating plates fitted between the bars and of which the outlines project beyond the outlines of the bars into the notches of the latter adapted to engage the retaining rings.

In order to obtain a good electrical insulation between the bars and the rings, the notches adapted to house the rings are given a large size with reference to the crosssection of the rings. Consequently the maximum crosssection of the retaining lugs cut out of the bars between the notches is very limited, which limits all the more the maximum rotary speed allowed for operation of the motor or the like machine.

In a particularly advantageous embodiment, the barretaining rings are made of an insulating material having a large mechanical resistance, such as a mass of glass fibres embedded in synthetic resin.

Thus, not only is it possible to reduce the size of the notches provided for the housing of the rings since the contact between the rings and the bars has no electrical action, but furthermore the problem of centering and holding in position the rings before injecting insulating material is avoided, said rings forming in fact binding hoops.

Preferably, the shoulder constituted by the outer ring engaging the lateral flange or its bed of insulating material is flush with the bottom of the central notches and serves as a support for the external connecting bars which may consequently be clamped in position by an outer hoop Without any risk of deformation.

My invention will be clearly understood from a reading of the following description, reference being made to the accompanying diagrammatic drawing illustrating by way of example and by no means in a limiting sense two embodiments of a commutator incorporating my improved arrangement. In said drawing:

FIG. 1 is a perspective view of a first embodiment of said commutator.

FIG. 2 is a plan view of a bar of the commutator according to FIG. 1.

FIG. 3 is a part sectional view extending axially through line 33 of FIG. 1.

FIG. 4 is a perspective view of a second embodiment of said commutator.

FIG. 5 is a part sectional view along the axis of the commutator illustrated in FIG. 4.

The commutator illustrated in FIGS. 1 to 3 is constituted in a conventional manner by bars 2 fitted around a central sleeve 12 while insulating plates 3 are fitted between the bars.

The bars 2 are assembled in the example illustrated by three metal rings 4, 5 and 6 (FIG. 3).

FIG. 2 shows the outline of a bar 2 along the inner surface of which are formed two notches 7 and 8 and a lateral projection 9 adapted to cooperate with the rings 4, 5 and 6 respectively so that the latter may be held in their assembled position.

The central notch 8 is given the shape of a bayonet slot and serves for housing the ring 5, the opening of said bayonet slot facing away from the radial outer extension 2a at one end of the bar 2, which extension is adapted to form part of a collar 11 holding in position the connections with the convolutions of the rotor windings.

The lateral projection 9 is provided at the end of the bar 2 located on the same side as said extension 2a, said projection 9 being adapted to form part of an annular shoulder over which is fitted outwardly the ring 6 of which the bore is larger than that of the other rings 4 and 5.

The outer notch 7 is provided at the end of the blade 2 facing away from the projection 9. It is adapted to engage the retaining ring 4. The outline of said notch 7 is advantageously the same as that of the projection 9 so that the cutting of a projection 9 in one bar may form the notch 7 in another bar cut out of a same blank; this provides the advantage of a substantial economy in the metal out of which the bars 2 are cut.

In order to prevent any contact between the bars 2 of the commutator and the rings 4, 5 and 6, the latter are held fast at a distance from the edges of the notches in which they are housed before the injection or molding of an insulating material adapted to secure them finally in position.

During said injection, the setting in position and the centering of the rings 4, 5 and 6 are advantageously ensured as well-known in the art by portions of the insulating plates 3 projecting beyond the outlines of the bars 2 into the notches 7 and 8 thereof and around the projections 9 as clearly shown in interrupted lines in FIG. 3.

As also clearly shown in said FIG. 3, the end of each bar 2 carrying the extension 2a, which end is subjected to the highest centrifugal forces and consequently to the highest stresses is held in position by the rings 5 and 6, without the presence of the latter leading to any reduction in the cross-section of the inner section 13 of the bar 2, which section 13 serves for anchoring purposes and must therefore resist efiiciently centrifugal force.

This is ascribable to the fact that the ring 5 is fitted inside the notch 8 while the ring 6 is fitted outside the projection 9 and furthermore the bore of said ring 6 is clearly larger than that of the ring 5.

In the example illustrated in FIGS. 4 and 5, the system of bars 14, between any two successive bars of which is inserted an insulating plate 15, is assembled by means of rings 16, 17, 18 and 19 made of insulating material with sufiicient mechanical properties, as is the case for instance for glass fibres embedded in synthetic resin.

The use of such rings has the advantage that their contact with the bars 14 has no detrimental electric effect.

In said embodiment illustrated in FIGS. 4 and 5, the central rings 17 and 18 are housed in radially inner central notches 21 and 22 having a T-shaped outline. The

outer ring 16 is housed inside a notch 23 formed endwise in the bars 14 at the end thereof facing away from their radial extension 14a adapted to carry the electrical connections of the rotor and lastly the ring 19 is fitted with a force fit around the projections 24 provided at the ends of the bars carrying the extensions 14a.

The arrangement is secured in a conventional manner by means of an insulating material 25 introduced through injection or molded andrigidly securing the commutator coaxially over the sleeve 26.

The assembly of such a commutator is a very easy matter when compared with the assembly of commutators of a known type wherein the retaining rings are made of metal. As a matter of fact, no special care is to be taken when fitting the rings in position to hold them away from the bars and, in contradistinction they may be fitted with .4 a force fit over the projections or into the notches of the bars.

A further advantage in the use of such rings consists in that the notches may be given a size which matches exactly the cross-section of the rings and, consequently, the cross-section of the retaining lugs formed in the bars between their notches may be increased.

Obviously, my invention is by no means limited to the embodiments of a commutator which have been described hereinabove by way of example and in a non-limiting sense and it covers in contradistinction all the modifications thereof falling within the scope of the accompanying claims. In particular, the number and the outline of the notches 8 (or 21 and 22) provided between the notches 7 (or 23) and the lateral projections 9 (or 24) are irrelevant, said number being obviously a function of the length of the commutator and furthermore the outline of the cross-section of the retaining rings and the nature of the material or materials forming them may be chosen as desired.

What I claim is:

1. In a commutator for rotary electrical machines, the provision of a plurality of similar radially distributed conductive elongated bars each having an inner edge with at least one notch extending at least at one end within the body of the bar to form a tongue therein along said edge, each bar having opposite ends and including at one end, and in its plane, a radial outwardly directed extension and a lateral projection, each bar being provided at its other end with a further notch extending into the transverse edge of the bar, radially distribtuted insulating plates separating successive bars and rings fitted in corresponding notches of the different bars and extending around the lateral projections on the different bars, the lateral projection of each bar having an outline matching the outline of said further notch therein and being disposed at the same level thereof in said bar.

2. A commutator as claimed in claim 1 comprising a sleeve supporting said bars and plates, and an insulat ing body secured to said sleeve and filling said notches and enclosing said projections of said bars, said rings being embedded in said insulating body.

3. A commutator as claimed in claim 1 wherein the rings are made of an insulating material having relatively high mechanical strength.

4. A commuttor as claimed in claim 1 wherein the rings are made of glass fibres embedded in synthetic resin.

5. A commutator as claimed in claim 1 wherein the outer surfaces of the lateral projections on the bars are substantially flush with the bottom surfaces of the first mentioned notches and are adapted to carry connecting bars.

6. A commutator as claimed in claim 4 wherein said rings are in direct contact with said bars.

References Cited UNITED STATES PATENTS 2,565,120 8/1951 Carter et al 310-236 2,600,312 6/1952 Meier 310236 3,290,527 12/ 1966 Habermann 3 l0-235 3,079,520 2/1963 Schafer et al 310-235 FOREIGN PATENTS 853,608 10/1952 Germany.

WARREN R. RAY, Primary Examiner.

R. SKUDY, Assistant Examiner.

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