FR2609217A1 - CARBON BRUSH FOR COLLECTOR OF ELECTRIC MACHINES - Google Patents

Abstract

THE INVENTION CONCERNS A CARBON BRUSH, FOR A MANIFOLD OF ELECTRIC MACHINES, CHARACTERIZED IN THAT THE TANGENTIAL DIMENSION T, WITH RESPECT TO THE COLLECTOR OF THE RUBBING FACE 4 IS REDUCED TO A VALUE T OVER AT LEAST TWO THIRDS OF THE WIDTH A OF THE BRUSH IN RELATION TO THIS DIMENSION T, ON THE EDGES OF THE SAID RUBBER FACE 4. THIS REDUCTION OF THE DIMENSION R MAY BE SYMMETRICALLY ON BOTH SIDES OF THE BROOM, OR ONLY ON THE FACE WHICH WEARS ON THE MANIFOLD.

Description

CARBON BRUSH FOR COLLECTOR OF ELECTRIC MACHINES

TECHNICAL DOEINE OF THE INVENTION

  The invention relates to a carbon brush intended to be used as a

  collector of electrical machines.

STATE OF THE ART

  Carbon brushes for electrical machine collectors exist in multiple sizes and geometries. The dimension "r" is the length of the brush radially relative to the collector, as dimension "t" the tangential dimension with respect to the collector,

  and as dimension "a" the axial dimension with respect to the collector.

  A large dimension "t" is favorable for the stability of the blade during operation. The dimension "t" must be much greater than the width of the collector blades in order to avoid instabilities

  when moving from one blade to another.

  When shearing blades, an unwanted switching current passes between these blades. In order to maintain this current at a low level, so-called glued brushes, or multi-layer brushes, consist of two parts which are connected by an insulating layer, each layer having a thickness substantially equal to t / 2. This arrangement can lead to a decrease in the heating of the collector, because the

  Short circuit currents are partially removed.

  Another way to improve the switching and reduce the heating of the collector consists of a reduction of the dimension "t". But this can lead to other problems, for example a mechanical instability of the brushes, source of spark, the impossibility of fixing the cables, the remaining thickness of the material being insufficient because with a small dimension "t" at the head of the broom, that is to say the part of the brush opposite the rubbing face, and with a soft material constituting

  the broom, its mechanical stability is no longer sufficient.

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OBJECT OF THE INVENTION

  The broom model, object of the invention, solves this problem by the fact that the tangential dimension "t" (with respect to the collector) of the friction face of the blade is reduced, but it remains unchanged on

the edges of the broom.

  Figures 1 and 2 illustrate the invention.

  FIG. 1 is a perspective view of a broom according to the invention

  whose dimension "t" has been reduced over the entire radial length "r".

  FIG. 2 is a perspective view of a broom according to the invention, whose dimension "t" has been reduced on only a part of the

  radial dimension "r" from the friction face.

  In these two figures, the blade 1 is shown with the rubbing face (on the manifold, not shown) of the side of the observer. According to the invention, the broom is provided with shapes such as shoulders 2 which guide it in the housing of the brush holder, which results, because of the dimension "t" of these shoulders, a good mechanical stability on the collector. The realization is, of

preferably symmetrical.

  Preferably, the reduction in dimension "t" is performed on at least two thirds of the width "a" of the broom. This reduction can be effected symmetrically on the two faces 4 and 5 of the brush (c8te collector and opposite side), or it can be performed in a limited way (Figure 2) on a part only r 'of the length r, but

  at least up to the maximum wear length expected for the broom.

  According to the example illustrated in FIG. 2, the reduced dimension t 'is equal to approximately 1/3 of the initial value t. This example is given

  for illustrative and not limiting.

  If the broom is small, the tangential grooves 3 may not go to the head 5 of the broom in the case o

  a sealed contact of the connecting cable is provided.

  For a subsequent lowering of its temperature the broom may be made in the form of a sticked broom or multilayer broom, as has been

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indicated previously.

  The implementation of the invention substantially improves the stability

  brooms and reduces the heating of the collectors.

Claims (4)

  1 - Carbon brush, for collector of electrical machines, characterized in that the tangential dimension t, with respect to the collector, of the friction face 4 is reduced to a value t 'over at least two thirds of the width a of the brush by ratio to this dimension t, on the edges of said friction face 4. 2 - Broom according to claim 1, characterized in that the reduction of the tangential dimension t relates to the two faces 3 and 4 of the broom 1, symmetrically.   3 - Broom according to claim 1, characterized in that the reduction of the tangential dimension relates to a limited length of the   total length (radial dimension r) of the blade 1.   4 - Broom according to any one of claims 1 to 3 characterized   in that it is multilayer or consists of glued lamellae.