GROUNDING BRUSH ASSEMBLY

A grounding brush assembly includes a brush and a brush mounting plate, the brush being provided with a plurality of conductive fibers and a support inside which the conductive fibers are housed, the mounting plate being secured to the support and provided with at least one radial portion extending radially outwardly with respect to the support. At least one centering portion extends at least axially from the radial portion and is spaced radially apart from and partially surrounding the support. Further, at least one orifice is formed in the centering portion, the orifice being spaced a distance apart from the proximal end of the centering portion and a distance apart from the distal end of the centering portion.

This application claims priority to French patent application no. 2301538 filed on Feb. 20, 2023, the contents of which are fully incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to the field of grounding devices for controlling the shaft current generated in electric motors or machines, and in particular grounding brush assemblies.

In an electric motor or machine, at least one rolling bearing is mounted between a casing of the motor, or other electric machine, and a rotary shaft in order to support the shaft. In operation, when the shaft is rotating, an electrical potential difference can appear between the shaft and the casing of the electric motor or machine, which may generate an electric current between the inner ring of the rolling bearing, which is secured to the rotary shaft, and the outer ring secured to the casing.

The electric current passing through the components of the rolling bearing can damage these components, in particular the rolling elements and the raceways formed on the inner and outer rings. Electrical discharges can also generate vibrations.

To remedy these drawbacks, it is a known practice to “earth” or ground the rotary shaft by using a grounding brush or sliding contact comprising conductive fibers. The grounding brush is generally mounted in the bore of the casing of the electric motor such that the free ends of the fibers are in radial contact with the outer surface of the rotary shaft. Due to the conductivity of the fibers, the brush is maintained at the same electrical potential as the casing of the electric motor. The inner and outer rings of the rolling bearing are also at the same electrical potential, which reduces and preferably even eliminates, the problematic electrical discharges through the rolling bearing.

US Publication No. 2021/0021180A1 discloses a grounding brush assembly comprising a grounding brush, which is provided with a support and a plurality of conductive fibers mounted in this support, and an annular mounting plate provided with a plurality of tongues for radial and axial retention of the support of the grounding brush and an annular outer flange radially surrounding the brush and the tongues. The tongues are formed by plastic deformations of the mounting plate. Such a grounding brush assembly is force-fitted into the bore of the casing, such that the grounding brush assembly is difficult to dismantle.

SUMMARY OF THE INVENTION

The present invention is directed to a grounding brush assembly comprising a grounding brush and a brush mounting plate, the brush being provided with a plurality of conductive fibers and a support inside of which the conductive fibers are housed.

The mounting plate is secured to the support and is provided with at least one radial portion extending radially outwards with respect to the support, and at least one centering portion extending from the radial portion at least axially and radially at least partly surrounding the support by being spaced apart radially from the support, the centering portion being provided with a proximal end connected to the radial portion and a distal end, the proximal and distal ends delimiting the axial dimension of the centering portion.

According to a general feature of the invention, at least one orifice is formed on the centering portion of the mounting plate, the orifice remaining at a distance from the proximal and distal ends of the centering portion.

As used herein, the expression “orifice formed on the centering portion of the mounting plate” is intended to mean that the orifice extends exclusively on the centering portion of the mounting plate. In other words, the orifice does not extend both on the centering portion and on the radial portion of the mounting plate.

When the assembly is mounted radially, at least partly, between a casing and a shaft of an electric motor, the orifice allows the insertion of a tool to readily dismantle the assembly, the tool notably making it possible to axially pull on the mounting plate by exerting an effort on the side opposite the casing.

The orifice can be formed as a blind hole extending from an inner surface or from an outer surface of the centering portion of the mounting plate. Alternatively, the orifice may be formed as a through hole passing right through the thickness of the centering portion of the mounting plate.

The centering portion of the mounting plate can be annular. Alternatively, the centering portion of the mounting plate can be of corrugated form circumferentially, the orifice being formed in a zone of small diameter of the centering portion.

According to another variant, the mounting plate comprises a plurality of centering portions spaced apart from one another circumferentially. The centering portions are thereby formed as lugs.

The grounding brush assembly may comprise a bent-back portion extending radially inwardly from the distal end of the centering portion of the mounting plate.

The mounting plate can further comprise at least one reinforcing folded-down portion extending from the distal end of the centering portion of the mounting plate and coming to bear against the centering portion of the mounting plate to form a ply and locally obtain a double thickness of material.

Advantageously, the longitudinal dimension of the reinforcing folded-down portion is at least three times greater than the thickness of the reinforcing folded-down portion.

Preferably, the reinforcing folded-down portion remains at a distance from the orifice or is flush with the orifice. Alternatively, the reinforcing folded-down portion can cover a part of the orifice.

The invention relates also to an electric machine or motor comprising a casing, a shaft, and a grounding brush assembly as defined previously mounted radially at least partly between the casing and the shaft, the conductive fibers of the assembly being in contact with the shaft.

DETAILED DESCRIPTION OF THE INVENTION

FIG.1represents, in axial cross-section, a part of an electric motor or machine2comprising a fixed casing4, a shaft6rotatable about an axis X-X, and a bearing8radially supporting the shaft6. The bearing8may be formed, for example, as a rolling bearing, preferably as a ball bearing. Alternatively, the bearing8may include another appropriate type of rolling elements, such as cylindrical rollers, tapered rollers, needles, etc. As a further alternative, the bearing8may be formed as a plain bearing.

The motor or machine2further comprises a grounding brush assembly10mounted partly radially between a bore of the casing12and the outer cylindrical surface of the shaft14. The assembly10is, for example, force-fitted into the bore of the casing12.

As better shown inFIGS.2and3, the grounding brush assembly10has a generally annular form. The assembly10basically comprises a grounding brush16and a brush mounting plate18.

The grounding brush16comprises a plurality of conductive fibers20and a support22, the conductive fibers20being housed inside the support22of the brush16. The conductive fibers20are formed, for example, of carbon, stainless steel, conductive plastics, such as acrylic fibers or nylon, etc. The plurality of conductive fibers20are preferably formed as an open ring. In the illustrated example, the conductive fibers20are folded around a link wire (not indicated). The free distal end of each one of the conductive fibers20is in radial contact with the outer surface of the shaft14.

To ensure the mounting and the retaining of the conductive fibers20, the support22of the brush16includes a mounting portion24, a first lateral rim26extending from one axial side of the mounting portion24and a second lateral rim28extending from an opposing axial side of the mounting portion24.

The mounting plate18is secured to the support22of the brush16. The mounting plate18includes a main body30bearing axially against the first lateral rim26of the support22of the brush16, a plurality of tongues32configured for axial and radial retention of the brush16, and an annular radial portion34. The radial portion34is provided with a plurality of through-apertures35formed in the thickness of the radial portion34and spaced circumferentially apart from each other. Preferably, the apertures35are formed when partially cutting the radial portion34to form the retaining tongues32.

The radial portion34of the mounting plate18extends radially outwardly from the main body30of the mounting plate18. The retaining tongues32extend from the main body30of the mounting plate18and are spaced circumferentially apart from each other in the assembly10. Each retaining tongue32extends from the main body30of the mounting plate18such that the retaining tongue32locally radially surrounds the support22of the brush16by being in radial and axial contact with the support22. The support22of the brush16is thus held axially and radially by the retaining tongues32.

In the depicted example, the mounting plate18includes eight retaining tongues32spaced circumferentially apart regularly or evenly. Alternatively, the mounting plate18may include a different number of retaining tongues32and/or have retaining tongues32that are spaced apart irregularly or unevenly.

The mounting portion24of the support22is in radial contact against the retaining tongues32and the second lateral rim28is in axial contact against the retaining tongues32. The mounting portion24extends to the large or outer diameter edge of the first lateral rim26. The mounting portion24here extends substantially or entirely axially, but the mounting portion24may alternatively extend obliquely.

The second lateral rim28of the support22extends radially inwardly from the mounting portion24. The second lateral rim28extends from the mounting portion24on the side or axial end opposite to the first lateral rim26. The mounting portion24and the first and second lateral rims26,28are of annular form and delimit a channel that is radially open on the internal side, an end of each conductive fiber20being located within the channel. The first and second lateral rims26,28axially grip the conductive fibers20such that the conductive fibers20bear axially on either side against the first and second lateral rims26,28.

In the depicted exemplary embodiment, the conductive fibers20bear radially against the mounting portion24and the first and second lateral rims26,28extend obliquely inwardly from the mounting portion24and generally toward each other. In a variant, the first and second lateral rims26,28may extend entirely or substantially radially.

As depicted, the mounting plate18and the support22of the brush16are two distinct or initially separate parts. In a variant, the mounting plate18may be formed as single piece with the support22of the brush16, for example, produced by cutting and stamping. In this case, the main body30of the mounting plate18extends from the small or inner diameter edge of the first lateral rim26.

The mounting plate18and the grounding brush16comprise an electrically conductive material, such as, for example, aluminum, stainless steel, bronze, copper or other material.

The mounting plate18also comprises an annular centering portion36extending at least axially from the large or outer diameter edge of the radial portion34of the mounting plate18. The centering portion36of the mounting plate18radially surrounds and is spaced radially apart from the mounting portion24of the support22. As depicted, the centering portion36of the mounting plate18extends entirely axially, but may alternatively extend both axially and radially, i.e. obliquely, inwardly or outwardly.

Instead of an annular centering portion36, the mounting plate18may alternatively comprise a plurality of centering portions36spaced circumferentially apart from each other. The plurality of centering portions36of the mounting plate18may extend entirely axially or may extend obliquely inwardly or obliquely outwardly.

The assembly10further comprises a plurality of orifices38formed on the centering portion36of the mounting plate18. Preferably, the orifices38are at least substantially identical to each other and are spaced circumferentially apart from each other. Each orifice38is axially at a distance from the radial portion34and from the distal free end of the centering portion36of the mounting plate18, i.e., each orifice38is spaced an axial distance from both the radial portion34and from the free end of the centering portion36. The proximal end of the centering portion36of the mounting plate18connects to the radial portion34of the mounting plate18. The centering portion36of the mounting plate18is delimited axially by a proximal end and by an opposite free, distal end.

Each orifice38may be formed as a through hole extending entirely through the thickness of the centering portion36of the mounting plate18. In other words, each orifice38emerges on an inner surface40of the centering portion36of the mounting plate18and on an outer surface42thereof.

In the depicted example, the mounting plate18comprises eight orifices38spaced apart circumferentially regularly or evenly. Also, the orifices38are shown arranged on a same circle. Alternatively, the mounting plate18may comprises a different number of orifices38and/or of orifices38that are spaced apart irregularly (i.e., staggered) and/or the orifices38may be located at different axial positions on the centering portion36of the mounting plate18, or the mounting plate18may even include only a single orifice38.

In another variant, one or more of the orifices38may each be formed as a blind hole extending outwardly from the inner surface40or inwardly from the outer surface42of the centering portion36of the mounting plate18and having a closed interior end located between the surfaces40,42.

Referring again toFIG.1, the assembly10is mounted radially at least partly between the bore of the casing12and the outer surface of the shaft14, such that the radial portion34of the mounting plate18bears axially against a shoulder of the casing4. The radial portion34of the mounting plate18bears radially against the bore of the casing12and extends protruding radially inwardly with respect to the casing12. Further, the centering portion36of the mounting plate18bears radially against and the bore of the casing12and extends axially with respect to the casing4.

As depicted, the centering portion36of the mounting plate18extends axially outside of the casing4, the orifices38being formed on the centering portion36of the mounting plate18so as to be axially offset outwardly with respect to the casing4, i.e., the orifices38are spaced axially from the casing4. In a variant, only a part of each orifice38could extend axially outside of the casing4, such that the orifices38extend axially across an axial end of the casing4.

The orifices38of the mounting plate18enable the insertion of a tool (not represented) making it possible to dismantle the assembly10relatively easily or readily. That is, the tool makes it possible to pull axially on the mounting plate18by exerting a force on the side opposite to the casing4.

In the depicted example, the orifices38are of rectangular form. Alternatively, the orifices38may have any other shape that enables the insertion of the tool.

The exemplary embodiment illustrated inFIG.4, in which elements that are identical bear the same references, differs from the example depicted inFIGS.1to3in that the mounting plate18of the assembly10further comprises an annular reinforcing folded-down portion44. The folded-down portion44extends from the distal end of the centering portion36of the mounting plate18and comes to bear against an outer side of the centering portion36so as to form a ply and locally provide a double thickness of material. In this exemplary embodiment, the distal end of the centering portion36is not therefore free or unconnected with another part or portion.

Alternatively, the reinforcing folded-down portion44may be folded down to come to bear on the inner side of the centering portion36. In another variant, the mounting plate18may include a plurality of reinforcing folded-down portions44spaced circumferentially apart from each other.

In the depicted example, the free end of the reinforcing folded-down portion44of the mounting plate18is flush with the orifices38. In a variant, the free end of the reinforcing folded-down portion44of the mounting plate18may be spaced a distance from the orifices38.

Preferably, the longitudinal dimension or length of the reinforcing folded-down portion44is at least three times greater than its thickness, notably in order to increase the mechanical strength of the mounting plate18of the assembly10.

The exemplary embodiment illustrated inFIG.5, in which the elements that are identical bear the same references, differs from the first example illustrated in that the mounting plate18of the assembly10comprises at least one bent-back portion46extending radially inwardly from the distal end of the centering portion36of the mounting plate18. In this exemplary embodiment, the distal end of the centering portion36is not therefore free or unconnected with another portion of the assembly10.

The assembly10is mounted radially partly between the bore of the casing12and the outer surface of the shaft14such that the bent-back portion46of the mounting plate18bears axially against a shoulder of the casing4or against an outer ring of the bearing8, in particular when the shaft6is rotary. The bent-back portion46of the mounting plate18is radially bearing against the bore of the casing12. The bent-back portion46of the mounting plate18extends axially protruding outwards with respect to the casing4.

The assembly10is mounted radially partly between the bore of the casing12and the outer surface of the shaft14such that the centering portion36of the mounting plate18bears radially against the bore of the casing12. The centering portion36of the mounting plate18and the bent-back portion46of the mounting plate18extend radially protruding inwardly with respect to the casing4.

The assembly10is mounted radially partly between the bore of the casing12and the outer surface of the shaft14such that the radial portion34of the mounting plate18is offset axially outside of the casing4. The plurality of orifices38are formed on the centering portion36of the mounting plate18such that each orifice38is offset axially from the casing4, each orifice38extending axially, at least partly, outside of the casing4.

The exemplary embodiment illustrated inFIGS.6to10, in which the elements that are identical bear the same references, differs from the first example in that the centering portion36of the mounting plate18is of a circumferentially corrugated form in the assembly10.

More specifically, the centering portion36of the mounting plate18comprises alternating small diameter sections48and large diameter sections50connected to each other by connecting sections52. That is, each one of the small diameter sections48and each one of the large diameter sections50of the centering portion36is extended on either circumferential side by a connecting section52.

In the depicted example, the connecting sections52are oblique. In a variant, the connecting sections52of the centering portion36of the mounting plate18can extend purely or substantially entirely radially.

The assembly10comprises a plurality of orifices38formed in a zone of the small diameter sections28of the centering portion36of the mounting plate18. Specifically, each orifice38is formed on one of the small diameter sections48of the centering portion36of the mounting plate18and extends partly over both of the two connecting sections52directly circumferentially adjacent to the particular small diameter section48. In a variant, each orifice38may be formed only or entirely on a small diameter section48of the centering portion36of the mounting plate18.

In the depicted example, the mounting plate18comprises eight identical orifices38spaced apart regularly circumferentially in the assembly10. The orifices38are preferably arranged on a same circle. In a variant, the mounting plate18comprises a different number of orifices38and/or orifices38spaced apart irregularly and/or orifices38formed at different axial positions of zones of a small diameter section48of the centering portion36of the mounting plate18, or even include only a single orifice38.

Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention.

All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter. The invention is not restricted to the above-described embodiments, and may be varied within the scope of the following claims.