Grounding brush assembly

Abstract

[Grounding brush assembly] This method of assembling an assembly (2) comprising a brush (16) having a support (22) including a mounting portion (24), and a mounting plate (18) having a main body (30) and tabs (40) each having an axial portion (42) in radial contact with said support (22), comprises: - positioning the support (22) against the main body (30), the mounting portion (24) having in the free state an outside diameter (D1); - forming the tabs (40) by partially cutting the mounting plate (18); and - assembling the tabs (40) against the mounting portion (24), the mounting portion (24) having in the area of ​​the axial portion (42) of each tab (40) an outside diameter (D2) strictly less than its outside diameter (D1) in the free state. Figure for the abridged version: Fig 1.

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 method of assembling 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 rim extending the mounting portion on the one hand, and a second lateral rim extending the mounting portion on the other hand, the first and second lateral rims axially enclosing said conductive fibers.

[0011] The mounting plate is provided with a main body and a plurality of brush holder retaining tabs, each retaining tab being provided with an axial portion extending axially from the main body, locally radially surrounding the brush holder and being in radial contact with said holder, and a radially inwardly bent portion which is located at the free end of the axial portion.

[0012] According to a general characteristic, the method comprises the following steps:

[0013] - a positioning step in which the support of the brush in axial contact against the main body of the mounting plate, the mounting portion of the support having in the free state an outside diameter;

[0014] - a step of forming the retaining tabs of the mounting plate by partial cutting of the mounting plate and by folding; and

[0015] - an assembly step in which the retaining tabs of the mounting plate in radial contact against the mounting portion of the brush support, the mounting portion of the support having, in the assembled state and in the area of ​​the axial portion of each retaining tab, an outside diameter strictly less than its outside diameter in the free state.

[0016] Thus, the axial and radial connection of the brush and the mounting plate is achieved in a simple and economical manner by means of the retaining tabs of the brush support. The circumferential connection of the brush and the mounting plate is also achieved in a simple and economical manner by means of the retaining tabs of the brush support which locally deform the mounting portion to an outside diameter which is less than its initial diameter in the free state.

[0017] The retaining tabs may be brought into contact with the mounting plate of the brush holder such that axial clearance remains between the folded portion of each of said tabs and the second lateral edge of the holder.

[0018] The retaining tabs may be brought into contact with the mounting plate of the brush holder so that the outer diameters of the mounting portion of the holder are equal to each other.

[0019] The present invention also relates to a grounding brush assembly comprising a grounding brush and a brush mounting plate, said brush being provided with a plurality of conductive fibers and a support within which the conductive fibers are housed.

[0020] The support comprises a mounting portion, a first lateral rim extending the mounting portion on the one hand, and a second lateral rim extending the mounting portion on the other hand, the first and second lateral rims axially enclosing said conductive fibers.

[0021] The mounting plate is provided with a main body and a plurality of brush holder retaining tabs, each retaining tab being provided with an axial portion extending axially from the main body, locally radially surrounding the brush holder and being in radial contact with said holder, and a radially inwardly bent portion which is located at the free end of the axial portion.

[0022] Such a set can be obtained by implementing a method as defined previously.

[0023] According to a general characteristic, the mounting portion of the support undulates in the circumferential direction, the mounting portion of the support comprising an alternation of sections of small external diameter and sections of large external diameter, the axial portion of each retaining tab being in radial contact with a section of small external diameter of the mounting portion.

[0024] An axial clearance may remain between the folded portion of each tab and the second lateral edge of the support.

[0025] The mounting plate may comprise at least one centering portion extending at least axially the main body of the mounting plate, offset radially outwardly relative to the support and provided with an outer surface defining the outer diameter of the mounting plate.

[0026] 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. Brief description of the figures

[0027] The present invention will be better understood upon studying the detailed description of embodiments, taken as non-limiting examples and illustrated by the attached drawings on which:

[0028] [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;

[0029] [Fig.2] is a front view of the grounding brush assembly of [Fig.l];

[0030] [Fig.3] is a sectional view of the whole of [Fig.2] along the axis III-III;

[0031] [Fig.4] schematically illustrates a method of assembling a grounding brush assembly according to the invention;

[0032] [Fig.5] schematically illustrates a positioning step of the method of [Fig.4];

[0033] [Fig.6] schematically illustrates a formation step of the method of [Fig.4]; and

[0034] [Fig.7] schematically illustrates an assembly step of the method of [Fig.4]. Detailed description of the invention

[0035] [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 radially by a bearing 8. The bearing 8 is for example a rolling bearing of the ball type. As a variant, it is possible to provide other rolling elements, for example rollers. In another variant, it is also possible to provide a plain bearing.

[0036] 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.

[0037] As illustrated more visibly in Figures 2 and 3, the assembly 10 has a generally annular shape.

[0038] 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.

[0039] 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.

[0040] The mounting portion 24 extends the large diameter edge of the first flange lateral 26. The first lateral flange 26 extends the mounting portion 24 radially inwards.

[0041] 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.

[0042] The mounting portion 24 here extends axially. Alternatively, the mounting portion 24 extends obliquely.

[0043] 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.

[0044] 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 inwards from the mounting portion 24. Alternatively, the first and second lateral edges 26, 28 could extend radially.

[0045] The mounting plate 18 comprises an annular main body 30 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 main body 30 of the mounting plate 18 comprises two opposite front faces 34, 36 which delimit the axial thickness of the main body 30 of the mounting plate 18. The first lateral edge 26 of the brush support is axially supported against the front face 36 of the main body 30.

[0047] 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 38 in the circumferential direction between two directly successive centering portions 32.

[0048] 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.

[0049] Each centering portion 32 here extends obliquely outwards, at least locally surrounding the mounting portion 24 of the brush 16 and remaining radially away from the mounting portion 24 and the support 22 of the brush 16. Alternatively, each centering portion 32 may extend purely axially. In another variant, each centering portion 32 may extend at least axially opposite the support 22 of the brush 16.

[0050] The mounting plate 18 also comprises a plurality of retaining tabs 40 to ensure axial attachment of the support 22 of the brush 16 relative to the mounting plate 18.

[0051] Each tab 40 is provided with an axial portion 42 extending axially from the main body 30 of the mounting plate 18, locally radially surrounding the support 22 of the brush 16 and being in radial contact with the support 22 of the brush 16. More precisely, each tab 40 is in radial contact with the mounting portion 24 of the support 22. The tabs 40 of the mounting plate 18 cooperate by radial contact with the support 22 of the brush 16 for the axial retention of the support 22 of the brush 16 relative to the mounting plate 18.

[0052] The axial portion 42 of each tab 40 remains radially spaced from the centering portions 32 of the mounting plate 18.

[0053] Each tongue 40 is also provided with a radially inwardly folded portion 44 which is located at the free end of the axial portion 42 of the tongue 40.

[0054] The folded portion 44 of each tab 40 remains axially at a distance from the second lateral edge 28 of the support 22 of the brush 16 so that an axial clearance 46 remains between said folded portion 44 and the second lateral edge 28 of the support 22.

[0055] The tabs 40 are offset relative to each other in the circumferential direction of the assembly 10, here in a regular manner. In the illustrated embodiment, there are eight tabs 40. Alternatively, it is of course possible to provide a different number of tabs 40, for example fewer or more.

[0056] The mounting portion 24 of the support 22 of the brush 16 is corrugated in the circumferential direction of the assembly 10. The mounting portion 24 of the support 22 comprises an alternation of sections of small external diameter and sections of large external diameter.

[0057] The axial portion 42 of each tab 40 of the mounting plate 18 is in radial contact with a small outer diameter section of the mounting portion 24 of the support 22.

[0058] In the illustrated embodiment, the mounting plate 18 comprises an alternation in the circumferential direction of the set 10 of tabs 40 and centering portions 32. Each tab 40 remains spaced in the circumferential direction from the set 10 of the two centering portions 32 which are directly adjacent to it. Alternatively, the mounting plate 18 could comprise a different quantity of tabs 40 and centering portions 32. Alternatively, the tabs 40 could be in contact in the circumferential direction of the assembly 10 with one or both of the centering portions 32 which are directly adjacent to it.

[0059] The mounting plate 18 and the support 22 of the brush 16 are two separate parts.

[0060] The mounting plate 18 and the grounding brush 16 comprise a material electrically conductive, such as aluminum, stainless steel, bronze, copper or other material.

[0061] In the example shown, 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.

[0062] In another variant, the mounting plate 18 may comprise a single annular centering portion 32 forming a flange.

[0063] In the example shown, the mounting plate 18 comprises a plurality of tabs 40 spaced regularly in the circumferential direction of the assembly 10. Alternatively, the mounting plate 18 may comprise a plurality of tabs 40 spaced irregularly in the circumferential direction of the assembly 10.

[0064] [Fig.4] schematically illustrates a method of assembling the assembly 10.

[0065] We begin with a positioning step 48 illustrated in [Fig. 5] in which the support 22 of the brush 16 is brought axially into axial contact against the main body 30 of the mounting plate 18, the first lateral edge 26 of the support being in axial support against the main body 30 of the mounting plate 18. In the free state, the mounting portion 24 of the support 22 has an external diameter DI of constant value. In other words, in the unassembled state, the mounting portion 24 of the support has a single external diameter DI.

[0066] The support 22 of the brush 16 is not yet secured to the mounting plate 18 at the positioning step 48.

[0067] Then, a step 50 of forming the tabs 40 is carried out in which the mounting plate 18 is cut and folded to form the tabs 40. This step is illustrated in [Fig. 6]. Alternatively, the forming step 50 can be carried out before the positioning step 48.

[0068] The centering portions 32 and the notches 38 are also formed during step 50.

[0069] Finally, an assembly step 52 is carried out in which the tabs 40 of the mounting plate 18 are brought into radial contact against the mounting portion 24 of the support 22 of the brush 16 so as to locally deform the support 22 of the brush 16.

[0070] During this step illustrated in [Fig.7], the tabs 40 of the mounting plate 18 are brought into radial contact against the mounting portion 24 of the support so that the latter has locally in the support zone of each tab 40 an outside diameter D2 strictly smaller than the outside diameter D1. Thus, the sections of small outside diameter D2 of the mounting portion 24 of the support 22 are formed. After assembly, the mounting portion 24 of the support 22 has its shape corrugated in the circumferential direction with alternating sections or zones of small outside diameter D2 in the zone of the tabs 40, and sections or zones of large outside diameter D1 outside the zone of the tabs 40.

[0071] Advantageously, the sections of small external diameter D2 of the mounting portion 24 of the support 22 are formed so as to leave the axial clearance 46 between the portion 44 folded radially inwards of the tabs 40 of the mounting plate 18 and the second lateral edge 28 of the support 22.

[0072] In the example shown, the tabs 40 of the mounting plate 18 are brought into radial contact against the mounting portion 24 of the support 22 so that the outer diameters D2 thereof are equal to each other. Alternatively, it could be possible to provide different outer diameters D2 for the mounting portion 24 of the support 22 which remain strictly less than the outer diameter D1 of the mounting portion 24 of the support 22 in the free state.

Claims

Claims

1. A method of assembling a grounding brush assembly (2) 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), the mounting plate (18) being provided with a main body (30) and a plurality of tabs (40) for retaining the support (22) of the brush (16), each retaining tab (40) being provided with an axial portion (42) extending axially from the main body (30),locally radially surrounding the support (22) of the brush (16) and being in radial contact with said support (22), and a portion (44) folded radially inwards which is located at the free end of the axial portion (42), characterized in that the method comprises the following steps:, - a positioning step (48) in which the support (22) of the brush (16) is brought axially into axial contact against the main body (30) of the mounting plate (18), the mounting portion (24) of the support (22) having an outside diameter (Dl) in the free state; - a step (50) of forming the tabs (40) for retaining the mounting plate (18) by partially cutting the mounting plate (18) and by folding; and - an assembly step (52) in which the retaining tabs (40) of the mounting plate (18) are brought into radial contact against the mounting portion (24) of the support (22) of the brush (16), the mounting portion (24) of the support (22) having, in the assembled state and in the area of ​​the axial portion (42) of each retaining tab (40), an outside diameter (D2) strictly less than its outside diameter (D1) in the free state.

2. A method according to claim 1, wherein the retaining tabs (40) are brought into contact with the mounting plate (18) of the support (22) of the brush (16) so that an axial clearance (46) remains between the folded portion (44) of each of said tabs (40) and the second lateral edge (28) of the support (22).

3. Method according to one of claims 1 and 2, in which the retaining tabs (40) are brought into contact with the mounting plate (18) of the support (22) of the brush (16) so that the external diameters (D2) of the mounting portion (24) of the support are equal to each other.

4. Grounding brush assembly (2) comprising a grounding brush (16) and a brush mounting plate (18), said 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), the mounting plate (18) being provided with a main body (30) and a plurality of tabs (40) for retaining the support (22) of the brush (16), each retaining tab (40) being provided with an axial portion (42) extending axially from the main body (30),locally radially surrounding the support (22) of the brush (16) and being in radial contact with said support (22), and a radially inwardly folded portion (44) which is located at the free end of the axial portion (42), characterized in that the mounting portion (24) of the support (22) undulates in the circumferential direction, the mounting portion (24) of the support (22) comprising an alternation of sections of small external diameter (D2) and sections of large external diameter (D1), the axial portion (42) of each retaining tab (40) being in radial contact with a section of small external diameter (D2) of the mounting portion (24).,

5. Assembly (2) according to claim 4, in which an axial clearance (46) remains between the folded portion (44) of each tab (40) and the second lateral edge (28) of the support (22).

6. Assembly (2) according to one of claims 4 and 5, in which the mounting plate (18) comprises at least one centering portion (32) extending at least axially the main body (30) of the mounting plate (18), offset radially outwards relative to the support (22) and provided with an outer surface defining the outer diameter of the mounting plate (18).

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

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