FR2514208A1 - MULTIPLE BRUSH HOLDER FOR ELECTRIC MACHINES - Google Patents

Abstract

The invention relates to a carbon-brush holder for electrical machines having large dimensions, which carbon-brush holder (as a modification from the metallic construction, consisting especially of cast brass, which was previously regarded as being necessary) consists of a plastic having the necessary mechanical, electrical and thermal properties, and only suitable metallic profiles, which are pressed into the plastic body, are provided as guides for the carbon brushes. In consequence, considerable savings can be made both in terms of material and in terms of production, and, above all, the carbon-brush holder is considerably lighter than a metallic carbon-brush holder.

Description

 The present invention relates to a multiple brush holder, of the type used in electric machines for mounting the carbon brushes which cooperate with the rotary elements thereof. These multiple brush holders are generally constituted by a body of cast brass, the individual guides of the brushes can be formed with the cars mating directly in this body during molding, although it has also been imagined to mold only the body. of brass in a single piece and to form the individual guides of the brushes by means of brass sheets introduced into this body. A molded part of this type is heavy and expensive and requires retouching. The same is true when the multiple brush holder is, as in certain known constructions, formed of various pieces of brass, whether they are parts molded or sheet metal sides. We also know brush holders made of plastic, which are intended for small electric motors. Thus the patent application in FRG DE-OS NO 17 63 023 describes a brush holder for an electric motor, which comprises a support in the form of a crown surrounding the whole machine and made of plastic material, on which are formed protrusions to receive the metal housings of the coals. Such an arrangement cannot be used on large machines, which operate only with brush holders on which several brushes, of which the number may be large, are arranged in a row. The same observations apply to the brush holder described in British patent 440,030.

In it, individual hats. made of plastic, each containing a brush and the associated pressure spring, are fixed to the motor housing. These brush holders cannot however be used on large motors due to the stresses which occur there.
Sent. The guidance of the brushes, in particular, does not meet, in these plastic brush holders, the conditions imposed. No provision has been made for ventilation, which is essential in large electrical machines.

 The object of the invention is therefore to produce a multiple brush holder, suitable for use on large electrical machines and to withstand the high stresses which occur therein, without having to use molded parts or other similar constructions in brass. , in order to save on weight and reduce the manufacturing cost.

 To this end, in the multiple brush holder according to the invention, intended for large electrical machines and comprising a plurality of guides arranged in a row and as many pressure brackets each associated with a respective guide, subjected to the force return of a tension spring and pivotally mounted in the brush holder body, the latter is made of a plastic material of an appropriate nature and, as guides of the brushes, profiles made of a metallic material are mounted by pressure in the openings which present and at least partially fill the walls thereof.

 The metal "rules" hitherto used as a support element for multiple brush holders of this type are replaced by the plastic body according to the invention. It is perfectly possible to produce in one operation the ventilation lights of the guides, which are essential on large machines for which these brush holders are specifically intended. The plastic body has the advantage of very well absorbing vibrations. The possibility of adjustment and interchangeability of this new brush holder is as perfectly guaranteed as with known metal brush holders of the same type.

 Epoxy resins or polyesters based on diallyl phthalate, containing glass fibers as filler, have been found to be particularly suitable plastics. They meet all the requirements in terms of mechanical resistance, as well as dielectric and thermal properties.

 It suffices to provide profiles which fill the areas of the edges of the guides. In this case, it has been found that the sections, the cross section of which is essentially I-shaped, are particularly suitable.

However, it is possible to use profiles which completely cover the walls of the guides.

 To obtain a perfect adjustment of the brush holder on the support collar, a metal plate can be embedded in the molding in its face turned towards the latter.

 The pressing elements can be mounted in this brush holder of plastic material in an identical or similar manner to that of which they are mounted in the known brush holder in molded brass. There are advantageously provided in the plastic body with recesses for mounting the metal pins on which the pressing elements can be mounted.

 It is particularly advantageous that the plastic brush holder body does not first establish any electrical connection between the brushes or their guides, on the one hand, and the pressure calipers, on the other hand, if the latter are also fitted with a cap that does not conduct electricity. By providing for the establishment of an electrical contact between the brush, or its guide, and the caliper from a certain degree of wear, there is then the possibility of triggering a warning signal. It is then advantageous to provide on each pressure caliper a leaf spring which, for example, when the brush has reached the complete degree of wear, bears against the guide with a low initial tension, the axis to which is attached the tension spring associated with the stirrup being also electrically connected to the outside.

In any case, the invention will be clearly understood with the aid of the description which follows, with reference to the appended schematic drawing, representing, by way of nonlimiting example, an embodiment of this brush holder:
Fig. 1 is a top view of the multiple brush holder according to the invention;
Fig. 2 is a side view of the brush holder of FIG.

1;
Fig. 3 is a bottom view of the brush holder of FIG. i;
Fig. 4 is a cross-sectional view of the brush holder in the region of a guide and a pressure yoke.

 The multiple brush holder shown in the figures essentially comprises a body 1, which is fixed in the usual way to a support collar 2. One of the fixing screws 3 used for this purpose is shown in broken lines in FIG. 3.

In the embodiment shown, the body
1 pressente three openings 4, 5 and 6, intended for the introduction of the brushes. Depending on the use for which the brush holder is intended, any other number of openings can obviously be provided. The latter are defined, on the one hand, by the body 1 itself, and, on the other hand, by guides 7, 8, 9 and 10. These guides are in this case constituted by sections of sections of brass obtained by spinning, but they can just as easily be made by assembling pieces of sheet metal or consist of small molded parts.

In addition, any other metallic material can be used in place of brass.

In the embodiment described here, the guides have an I-profile, with a wing 12 at each free end of the transverse branches II of the I, wing- which extends outwards, perpendicular to the respective branch. Between each of the transverse branches
11 of the I-profile of each guide and the internal face placed opposite the plastic body 1 there remains a ventilation lumen 13 and the same is true between the core of the I-profile of the extreme guides 7 and 10 and the face internal of the body 1 placed opposite this core.

 The body 1 of the brush holder according to the invention is provided in addition to the usual means for mounting the pressure brackets 14, of which only the one which is on the right is shown in Figures 1 to 3. For this purpose, the body 1 of plastic material has projections 15, 16, 17 and 18, with in each of them a recess for the pivot axis 19 of the respective stirrup. Between the projections 15, 16, 17 and i8 are defined housings 20, 21 and 22, in which the stirrups are engaged 14. A bar 23 extends transversely in front of the housings 20, 21 and 22 and serves as a stop for the stirrups 14, so that these, by pivoting, do not sink beyond a certain point in the openings 4, 5 and 6.

 The upper face of the body 1 of the brush holder is, in known manner, provided with a metallic conductive bridge 24 and associated connection screws 25, as well as a main connection screw 26. On its edge 27 turned towards the support collar 2, the body 1 is provided with a metal adjustment plate 28, which penetrates into corresponding recesses 29 in the collar 2.

 As shown in particular in FIG. 2, the guides 7, 8, 9 and 10 protrude slightly on the underside 30, facing the electric machine, of the body i, in order to protect the latter against "spitting on the brushes, when the machine is in operation. One can also clearly see in FIG. 2 the recesses 31 for receiving the heads 32 of the connection screws 25. I1 is also provided in the body 1 of the recesses 33 and for the nuts 35 - of the screws fixing 3.

 The body 1 finally has a longitudinal slot 36 for mounting the axis 37 to which the loop 38 is hooked from one of the ends of the tension spring 39 associated with each pressure bracket 14, a spring of which the other end is also provided a loop 40 passed around a transverse axis 41 fixed on the stirrup.

 The production of the body 1 with a material which does not conduct electricity makes it possible to provide it with the possibility of indicating the position of the brushes in which the wear thereof is such that their replacement becomes essential. We can see in Figure 4 the body 1 in cross section at a guide 9, and the pressure caliper 14 associated. This stirrup pivots on the axis 19 in the body 1; it is metallic, as well as the tension spring 39 and the pin 37 for hooking this spring.

 The stirrup 14 is provided with an electrically insulating cap 43, by means of which it exerts its pressure on the brush 42. Between the latter and the guide 9 which surrounds it, on the one hand, and the stirrup 14 , on the other hand, there is therefore no electrical contact. The stirrup 14 is also provided with a leaf spring 44, visible in FIG. 4, which can be fixed on the stirrup at the same time as the cap 43, by a common connecting member 45.

 When the stirrup 14, as a result of the wear of the brush 42, reaches the position 14 'shown in broken lines, the leaf spring 44 comes into electrical contact with the guide 9 with a slight initial tension. It then suffices to provide on the axis 37 for hooking the tension spring an electrical connection 46 shown diagrammatically, to obtain an indication that the brush has reached the position in which its wear requires its replacement.

 The plastic body 1, with the guides and the adjustment plate, can be produced in a single die-casting operation. there are suitable plastics on the market, which perfectly meet the required conditions, in particular from the point of view of mechanical strength and electrical and thermal properties. Among them, thermosetting materials reinforced with glass fibers, give excellent results. The body according to the invention allows a saving of material, a reduction in the manufacturing cost and above all a saving in weight.

Claims (7)

- CLAIMS  1.- Multiple brush holder for large electrical machines and comprising a plurality of guides arranged in a row, and as many pressure calipers each associated with a respective guide, subjected to the return force of a spring tension and pivotally mounted in the body of the brush holder, characterized in that said body (1) is made of a plastic material of an appropriate nature and in that, as guides of the brushes, profiles (7,8 , 9,10) made of a metallic material are mounted with pressure in the openings (4,5,6) which it presents and garnish, at least in part, the walls.  2. A brush holder according to claim 1, characterized in that its body (1) is made of a thermosetting resin, such as an epoxy resin or based on diallyl phthalate, containing glass fibers as filler.  3. A brush holder according to claim 1 or claim 2, characterized in that the profiled guides (7,8,9,10) of the brushes (42) have a profile which, essentially, has the form d 'an I and are made of a metallic material.  4. Brush holder according to any one of claims 1 to 3, characterized in that the profiled guides (7,8,9,10) cover the walls of the openings (4,5,6) only in the area edges of these.  5.- Brush holder according to any one of claims i to 4, characterized in that a metal adjustment plate (28) is embedded in the edge of the body (1) which is turned towards the support collar (2) of the brush holder.  6.- Brush holder according to any one of claims 1 to 5, characterized in that the body (1) has recesses for mounting metal pivot pins (-19) on which the pressing members are mounted .  7. A brush holder according to any one of claims 1 to 6, characterized in that the pressure members (14) shaped as stirrups are each provided with a cap (43) which isolates them from the associated brush (42) , as well as a leaf spring (44). subjected to an initial tension, which electrically connects them to the respective guide when they have reached an extreme position, and in that the axis (37) to which is attached the tension spring (39) of each pressure bracket (14 ) has an electrical connection with the outside (46).