Grounding Brush Set

The grounding brush assembly addresses the challenge of secure attachment by using tabs on the brush support that extend through openings in the mounting plate, ensuring effective reduction of electrical discharges and shaft currents.

FR3150660B1Active Publication Date: 2025-05-23AB SKF SKF PATENT DEPARTMENT
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Patent Information

Application Number
FR2023006925
Authority / Receiving Office
FR · FR
Patent Type
Patents
Current Assignee / Owner
Filing Date
2023-06-30
Publication Date
2025-05-23
Estimated Expiration
2043-06-30

AI Technical Summary

Technical Problem

Existing grounding brush assemblies for electric motors or machines face challenges in securely attaching the grounding brush to the mounting plate, which can lead to instability and inefficiency in reducing electrical discharges and shaft currents.

Method used

The proposed grounding brush assembly features a brush support with tabs that extend through openings in the mounting plate, with folded free ends that axially retain the brush support, providing a simple and economical method for secure attachment.

Benefits of technology

This solution effectively secures the grounding brush to the mounting plate, ensuring reliable reduction of electrical discharges and shaft currents, thereby protecting the rolling bearing components and maintaining motor efficiency.

✦ Generated by Eureka AI based on patent content.

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Abstract

[Grounding brush assembly] This grounding brush assembly (10) comprises a brush (16), a mounting plate (18), the brush (16) being provided with a plurality of conductive fibers (20) and a support (22) inside which the fibers (20) are housed, the support (22) comprising a mounting portion (24), first and second lateral flanges (26, 28) axially enclosing said conductive fibers (20), at least one through opening (46) being formed in the thickness of the mounting plate (18), the support (22) comprising at least one tab (48) extending through said opening (46) and being provided with a folded free end adapted to cooperate with the mounting plate (18) for axially retaining the support (22) relative to the mounting plate (18), said folded free end being located axially on the opposite side to the support (22) with respect to the mounting plate (18). Figure for abstract: Fig 1.
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Description

Title of invention: Grounding brush assembly Technical field of the invention

[0001] 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. State of the prior art

[0002] In an electric motor or machine, at least one rolling bearing is mounted between the housing of the electric motor or machine and the rotating shaft in order to support this shaft.

[0003] In operation when the shaft is rotating, an electrical potential difference may appear between it and the casing of the motor or the electric machine, which generates an electric current between the inner ring of the rolling bearing which is integral with the rotating shaft, and the outer ring integral with the casing.

[0004] Electric current passing through rolling bearing components can damage these components, including rolling elements and raceways on the inner and outer rings. Electrical discharges can also generate vibrations.

[0005] To overcome these drawbacks, it is known to ground or earth the rotating shaft using a grounding brush or broom comprising conductive fibers. The grounding brush is generally mounted in the bore of the electric motor housing such that the free ends of the fibers are in radial contact with the outer surface of the rotating shaft.

[0006] Due to the conductivity of the fibers, the brush is maintained at the same electrical potential as the electric motor housing. The inner and outer rings of the rolling bearing are also at the same electrical potential, which reduces or even eliminates problematic electrical discharges through the rolling bearing.

[0007] Document US-A1-2021 / 0021180 discloses a grounding brush assembly comprising a grounding brush provided with a support and a plurality of conductive fibers mounted in this support, and an annular mounting plate provided with a plurality of radial and axial retaining tabs for the support of the grounding brush, and an annular outer flange radially surrounding the brush and the tabs. The tabs are formed by plastic deformation of the mounting plate.

[0008] The present invention aims to provide an alternative attachment for a grounding brush. ground to a mounting plate. Summary of the invention

[0009] 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 holder within which the conductive fibers are housed.

[0010] The support comprises a mounting portion, a first lateral edge extending on the one hand the mounting portion, and a second lateral edge extending on the other hand the mounting portion, the first and second lateral edges axially enclosing said conductive fibers.

[0011] According to a general characteristic, at least one through opening is formed in the thickness of the mounting plate, the brush support comprising at least one tab extending through said opening, said tab being provided with a folded free end and capable of cooperating with the mounting plate for axial retention of the brush support relative to the mounting plate, said folded free end being located axially on the side opposite the support relative to the mounting plate.

[0012] Thus, the axial connection of the brush is achieved in a simple and economical manner. and the mounting plate using the tab(s) on the brush holder.

[0013] The mounting plate may be provided with a main body.

[0014] The mounting plate may be provided with at least one pro centering portion extending at least axially from the main body, radially offset outwardly relative to the support and having an outer surface defining the outer diameter of the mounting plate.

[0015] Said through opening may be formed in the thickness of the main body of the mounting plate.

[0016] Said tongue may be adapted to cooperate with the main body of the mounting plate.

[0017] Said tongue of the brush support may extend from the mounting portion of the brush support.

[0018] Said tongue may be formed by partial cutting of the brush support.

[0019] The first lateral edge of the support may be in axial contact with the mounting plate.

[0020] According to a particular design, a plurality of through openings are formed in the thickness of the mounting plate, said openings being offset from each other in the circumferential direction, the brush holder comprising a plurality of tabs, each tab of the brush holder extending through a of said openings, each tab being provided with a folded free end and capable of cooperating with the mounting plate for the axial retention of the brush support relative to the mounting plate, said folded free ends being located axially on the side opposite the brush support relative to the mounting plate.

[0021] The present invention also relates to an electric motor comprising a casing, a shaft and a grounding brush assembly as defined above and mounted radially between the casing and the shaft, the conductive fibers of said assembly being in contact with the shaft, the mounting plate being in radial contact with the bore of the casing.

[0022] The invention also relates to a method of assembling a grounding brush assembly as defined above comprising the following steps:

[0023] - a positioning step in which the setting brush is brought axially to the ground against the mounting plate and said tab is axially introduced through said opening so that the free end of said tab is located axially on the side opposite the support relative to the mounting plate; and

[0024] - an assembly step during which the free end of said brush holder tab.

[0025] The method may also comprise a prior step of partially cutting the first lateral edge of the brush support to form said tab. Brief description of the figures

[0026] The present invention will be better understood upon studying the detailed description of embodiments, taken as non-limiting examples and illustrated by the appended drawings in which:

[0027] [Fig-1] is an axial sectional view of a grounding brush assembly mounted radially between a rotating shaft and an electric motor housing according to an exemplary embodiment of the invention;

[0028] [Fig.2] is a front view of the grounding brush assembly of [Fig.l];

[0029] [Fig.3] is a sectional view of the whole of [Fig.2] along the axis III-III;

[0030] [Fig.4] is a sectional view of the whole of [Fig.2] along axis IV-IV;

[0031] [Fig.5] schematically illustrates a method of assembling a brush assembly grounding according to the invention;

[0032] [Fig.6] illustrates a positioning step of the method of [Fig.5]; and

[0033] [Fig.7] illustrates an assembly step of the method of [Fig.5]. Detailed description of the invention

[0034] [Fig.l] represents, in axial section, a part of an electric motor or machine 2 comprising a fixed casing 4, a shaft 6 in particular rotating, of axis XX, supported ra- dially by a bearing 8. The bearing 8 is for example a rolling bearing of the ball type. Alternatively, it is possible to provide other rolling elements, for example rollers. In another variant, it is also possible to provide a plain bearing.

[0035] The motor 2 comprises a grounding brush assembly 10 mounted radially between the bore of the casing 12 and the external cylindrical surface of the shaft 14. The assembly 10 is, for example, force-fitted into the bore of the casing 12.

[0036] As illustrated more visibly in Figures 2 to 4, the assembly 10 has a generally annular shape.

[0037] The assembly 10 comprises a grounding brush 16 and a brush mounting plate 18. The brush 16 comprises a plurality of conductive fibers 20 and a support 22, the conductive fibers 20 being housed inside the support 22 of the brush 16. The conductive fibers 20 are for example made of carbon, stainless steel, conductive plastics, such as acrylic fibers or nylon. The plurality of conductive fibers 20 is in the form of an open ring. In the illustrated example, the conductive fibers 20 are folded around a connecting wire. The free distal end of the conductive fibers 20 is in radial contact with the external cylindrical surface of the shaft 14.

[0038] To ensure the mounting and retention of the conductive fibers 20, the support 22 of the brush 16 comprises a mounting portion 24, a first lateral rim 26 extending the mounting portion 24 on the one hand and a second lateral rim 28 extending the mounting portion 24 on the other hand.

[0039] The mounting portion 24 extends the large diameter edge of the first lateral flange 26. The first lateral flange 26 extends the mounting portion 24 radially inward.

[0040] The mounting portion 24 extends the large diameter edge of the second lateral flange 28. The second lateral flange 28 extends the mounting portion 24 radially inward. The second lateral flange 28 extends the mounting portion 24 on the side opposite the first lateral flange 26.

[0041] The mounting portion 24 here extends axially. Alternatively, the mounting portion 24 may extend obliquely.

[0042] The mounting portion 24 and the first and second lateral edges 26, 28 are generally annular in shape and delimit a channel open radially on the inner side inside which one end of the conductive fibers 20 is located. The first and second lateral edges 26, 28 axially enclose the conductive fibers 20. The conductive fibers 20 are axially supported on either side against the first and second lateral edges 26, 28.

[0043] In the illustrated embodiment, the conductive fibers 20 come to bear radially against the mounting portion 24, the first and second lateral edges 26, 28 extending obliquely inwardly from the mounting portion 24. Alternatively, the first and second side flanges 26, 28 could extend radially.

[0044] As will be described in more detail below, the brush support 22 also comprises a plurality of retaining tabs 48 to ensure the axial securing of said support relative to the mounting plate 18.

[0045] The mounting plate 18 comprises a main body 30 of generally annular shape axially bearing against the first lateral edge 26 of the support 22 of the brush 16, and a plurality of centering portions 32 extending obliquely outwards the large diameter edge of the main body 30.

[0046] The centering portions 32 of the mounting plate 18 are spaced apart from each other in the circumferential direction of the assembly 10, leaving a notch 34 in the circumferential direction between two directly successive centering portions 32. The centering portions 32 are, for example, formed by cutting out an annular portion so as to form the notches 34.

[0047] The centering portions 32 define the outer diameter of the mounting plate 18. The outer surfaces of the centering portions 32 define the outer diameter of the mounting plate 18. The centering portions 32 allow the centering of the mounting plate after mounting in the bore of the casing 12 of the associated electric motor 2.

[0048] Each centering portion 32 here extends obliquely outwards, at least locally surrounding the mounting portion 24 of the brush 16 and remaining radially at a distance from the mounting portion 24 and the support 22 of the brush 16. As a variant, each centering portion 32 may extend purely axially. In another variant, each centering portion 32 may extend at least axially opposite the mounting portion 24 of the support 22 of the brush 16.

[0049] The mounting plate 18 and the brush holder 22 are two separate parts.

[0050] The mounting plate 18 and the grounding brush 16 comprise a material electrically conductive, such as aluminum, stainless steel, bronze, copper or other material.

[0051] The main body 30 of the mounting plate 18 comprises two opposite front faces 38, 40 which delimit the axial thickness of the main body 30 of the mounting plate 18. The first lateral edge 26 of the support 22 of the brush comes to bear axially against the front face 40 of the main body.

[0052] A plurality of through openings 46 are formed in the thickness of the mounting plate 18. More precisely, each opening 46 is formed in the axial thickness of the main body 30 of the mounting plate 18, extending from the front face 38 to the front face 40. The openings 46 open onto the front faces 38, 40. The or openings 46 are located radially at a distance from the bore of the main body 30. The openings 46 are identical to each other.

[0053] The openings 46 here extend axially. Alternatively, the openings 46 could extend obliquely. The openings 46 are offset from each other in the circumferential direction of the assembly 10, here in a regular manner. In the illustrated embodiment, there are eight openings 46. Alternatively, it is of course possible to provide a different number of openings 46, for example a smaller or larger number.

[0054] As indicated previously, the support 22 of the brush 16 comprises a plurality of retaining tabs 48 to ensure the axial attachment of said support 22 relative to the mounting plate 18. The tabs 48 are identical to each other.

[0055] Each tab 48 axially extends the mounting portion 24 of the brush holder opposite the second lateral flange 28 of the brush holder. Each tab 48 extends axially through one of the openings 46 formed in the thickness of the mounting plate 18.

[0056] Each tab 48 of the support 22 of the brush 16 is provided with a free end 48a located axially on the side opposite the support 22 of the brush 16 relative to the mounting plate 18 and folded to extend projecting relative to the main body 30 of the mounting plate 18.

[0057] The folded free end 48a of each tab 48 cooperates by axial contact with the mounting plate 18 for the axial retention of the support 22 of the brush 16 relative to the mounting plate 18. The folded free end 48a of each tab 48 cooperates by axial contact with the front face 38 of the mounting plate.

[0058] In the example shown, each folded free end 48a of the tabs 48 extends radially outwards while being in axial contact with the front face 38 of the main body 30 of the mounting plate 18. Alternatively, all or part of the folded free ends of the tabs 48 may extend radially inwards and / or while remaining axially spaced from the front face 38 of the main body 30 of the mounting plate 18. Alternatively, the folded free ends 48a of the tabs 48 could extend obliquely.

[0059] In the exemplary embodiment, the tabs 48 extend from the mounting portion 24 of the support 22 of the brush 16. Alternatively, the tabs 48 could extend from the rounded portion connecting the mounting portion 24 of the support 22 to the first lateral edge 26. As a variant, the tabs 48 could extend from the first lateral edge 26 of the support 22.

[0060] In the illustrated embodiment, the support 22 of the brush 16 is made in a single piece. Alternatively, the tabs 48 could be separate pieces formed separately and fixed to the support 22 by any suitable means, for example by welding or gluing.

[0061] In the example shown, the second lateral rim 28, the mounting portion 24 and the first lateral rim 26 are in the shape of an open ring and extend along an angular sector greater than 300°, in particular along an angular sector greater than 350°.

[0062] In the example shown, the support 22 of the brush 16 comprises a plurality of retaining tabs 48. Alternatively, the support 22 of the brush 16 may comprise a single retaining tab 48, the mounting plate 18 then being able to comprise a single through opening 46.

[0063] In the exemplary embodiment, the mounting plate 18 comprises a plurality of centering portions 32 spaced regularly in the circumferential direction of the assembly 10. Alternatively, the mounting plate 18 may comprise a plurality of centering portions 32 spaced irregularly in the circumferential direction of the assembly 10.

[0064] In another variant, the mounting plate 18 may comprise a single annular centering portion 32 forming a flange.

[0065] [Fig.5] schematically illustrates a method of assembling the assembly 10.

[0066] We begin with a step of partial cutting 58 of the first lateral edge 26 of the support 22 of the brush 16 to form the tabs 48.

[0067] Then, a positioning step 60 is carried out in which the support 22 of the brush 16 is brought axially against the mounting plate 18, the first lateral edge 26 of the support 22 of the brush 16 being in axial support against the main body 30 of the mounting plate 18.

[0068] During this step, each tab 48 of the support 22 of the brush 16 is also axially introduced through one of the openings 46 formed in the thickness of the mounting plate 18 so that the free end of each tab 48 of the support 22 of the brush 16 is located axially on the side opposite the support 22 of the brush 16 relative to the mounting plate 18 and extends projecting. This step is illustrated in [Fig.6].

[0069] Finally, an assembly step 62 is carried out in which the free end of each tab 48 of the support 22 of the brush 16 is folded against the mounting plate 18. This step is illustrated in [Fig.7]. Thus, the axial connection of the brush 16 and the mounting plate 18 is achieved.

Claims

Claims

1. Grounding brush assembly (10) comprising a grounding brush (16) and a brush mounting plate (18), the brush (16) being provided with a plurality of conductive fibers (20) and a support (22) inside which the conductive fibers (20) are housed, the support (22) comprising a mounting portion (24), a first lateral flange (26) extending on the one hand the mounting portion (24), and a second lateral flange (28) extending on the other hand the mounting portion (24), the first and second lateral flanges (26, 28) axially enclosing said conductive fibers (20), characterized in that at least one through opening (46) is formed in the thickness of the mounting plate (18), the support (22) of the brush (16) comprising at least one tab (48) extending through said opening (46),said tab (48) being provided with a folded free end (48a) and capable of cooperating with the mounting plate (18) for the axial retention of the support (22) of the brush (16) relative to the mounting plate (18), said folded free end (48a) being located axially on the side opposite the support (22) relative to the mounting plate (18).,

2. Assembly (10) according to claim 1, wherein the mounting plate (18) is provided with a main body (30) and at least one centering portion (32) extending at least axially the main body (30), offset radially outwards relative to the support (22) and provided with an outer surface defining the outer diameter of the mounting plate (18), said through opening (46) being formed in the thickness of the main body (30), said tab (48) being able to cooperate with the main body (30) of the mounting plate (18)

3. An assembly (10) according to one of claims 1 and 2, wherein said tab (48) of the brush holder extends from the mounting portion (24) of the holder (22) of the brush (16).

4. Assembly (10) according to any one of the preceding claims, in which said tab (48) is produced by partially cutting the support (22) of the brush (16).

5. An assembly (10) according to any preceding claim, wherein the first lateral flange (26) of the support (22) is in axial contact with the mounting plate (18).

6. An assembly (10) according to any one of the preceding claims, wherein a plurality of through-openings (46) is formed in the thickness of the mounting plate (18), said openings (46) being offset from each other in the circumferential direction, the support (22) of the brush (16) comprising a plurality of tabs (48), each tab (48) of the support (22) of the brush (16) extending through one of said openings (46), each tab (48) being provided with a folded free end (48a) and capable of cooperating with the mounting plate (18) for axially retaining the support (22) of the brush (16) relative to the mounting plate (18), said folded free ends (48a) being located axially on the side opposite the support (22) of the brush (16) relative to the mounting plate (18).

7. An electric motor (2) comprising a housing (4), a shaft (6) and a grounding brush assembly (10) according to any preceding claim mounted radially between the housing (4) and the shaft (6), the conductive fibers (20) of said assembly (10) being in contact with the shaft (6), the mounting plate (18) being in radial contact with the bore of the housing (12).

8. A method of assembling a grounding brush assembly (10) according to any one of claims 1 to 6, characterized in that it comprises the following steps: - a positioning step (60) in which the grounding brush (16) is brought axially against the mounting plate (18) and said tab (48) is axially introduced through said opening (46) so that the free end of said tab (48) is located axially on the side opposite the support (22) relative to the mounting plate (18); and - an assembly step (62) during which the free end of said tab (48) of the brush support is folded.

9. Method according to claim 8, comprising a prior step of partially cutting the first lateral edge (26) of the brush support to form said tab (48).