Grounding brush assembly

Abstract

[Grounding Brush Assembly] The grounding brush assembly (10) comprising a grounding brush (16) having a plurality of conductive fibers (20) and a brush mounting plate (18), the mounting plate (18) comprising a main body (22) and a centering means (24) extending from the main body (22) and surrounding at least locally the grounding brush (16) while remaining radially at a distance from said brush (16). The mounting plate (18) is provided with a mounting portion (26) within which the conductive fibers (20) of the grounding brush (16) are housed, and with first and second opposing lateral rims (28, 30) axially enclosing said conductive fibers (20), the first lateral rim (28) extending from the main body (22). Figure for the abbreviation: Fig 4.

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 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 said brush and the tabs. The tabs are formed by plastic deformation of the mounting plate.

[0008] Such a grounding brush assembly requires many steps of assembly.

[0009] Indeed, with the design of this document, it is necessary to crimp the support onto the plurality of conductive fibers, then to form the tabs which ensure the retention of the support.

[0010] It is understood that there is a need to provide a grounding assembly of simplified design making it possible to reduce the costs associated with manufacturing and assembly operations. Summary of the invention

[0011] A grounding brush assembly includes a grounding brush having a plurality of conductive fibers and a brush mounting plate.

[0012] The mounting plate comprises a main body and a centering means extending from the main body and at least locally surrounding the grounding brush while remaining radially spaced from said brush.

[0013] The mounting plate is provided with a mounting portion within which the conductive fibers of the grounding brush are housed, and first and second opposite lateral flanges axially enclosing said conductive fibers, the first lateral flange extending from the main body.

[0014] Thus, the mounting plate fulfills a dual function, namely a function of mounting and centering the assembly inside the bore of the associated electric motor housing, but also a function of retaining support for the conductive fibers.

[0015] Thus, compared to conventional assemblies, a single part performs this dual function, which reduces the number of parts to be manufactured and assembled.

[0016] In addition, the number of steps required to mount the grounding brush assembly is also reduced.

[0017] The mounting plate grips one end of the conductive fibers and holds that end of the conductive fibers in contact with the mounting plate.

[0018] In one embodiment, the mounting portion of the mounting plate extends axially. Alternatively, the mounting portion may extend both axially and radially, i.e., obliquely.

[0019] Preferably, the first and second side flanges of the mounting plate extend obliquely inwardly toward the conductive fibers of the grounding brush.

[0020] In one embodiment, the conductive fibers bear radially against the mounting portion of the mounting plate. Alternatively, it could be possible to leave a radial space between the conductive fibers and the portion disassembly.

[0021] In one embodiment, the first lateral edge of the mounting plate bears against said main body to form a fold and locally obtain a double thickness of material.

[0022] This makes it possible to improve the mechanical strength of the mounting plate.

[0023] Advantageously, the second lateral edge of the mounting plate has a reduced thickness compared to that of the first lateral edge and the mounting portion. Alternatively, or in combination, the brush mounting plate comprises a groove, located in the connection area of ​​the second edge with the mounting portion, so as to facilitate the folding of the second edge. The second edge is for example crimped onto the conductive fibers.

[0024] In one embodiment, the first and second side flanges have a substantially equal length. Alternatively, the first and second side flanges may be of different lengths.

[0025] Preferably, the mounting plate is made in one piece, in particular by stamping. This facilitates the manufacture of the mounting plate.

[0026] Advantageously, the centering means of the mounting plate is offset radially outwards relative to the mounting portion.

[0027] According to a particular design, the centering means of the mounting plate comprises an annular outer flange, said flange comprising an annular connecting portion extending outwardly the main body, and an annular centering portion extending at least axially the annular connecting portion and surrounding the mounting portion while remaining radially at a distance from said mounting portion.

[0028] In another embodiment, the centering means of the mounting plate comprises a plurality of centering tabs extending from the main body and spaced apart from each other in the circumferential direction, each centering tab being provided with a connecting portion extending the main body outwardly, and a centering portion extending at least axially the connecting portion and locally surrounding the mounting portion while remaining radially at a distance from said mounting portion, said centering portion being delimited in the circumferential direction by free front faces.

[0029] The centering portions of the tabs define the outer diameter of the mounting plate. Furthermore, the design of the mounting plate with centering tabs makes it possible to simplify mounting in the bore of the associated electric motor housing given the more flexible nature of the tabs compared to the annular outer flange.

[0030] Preferably, the main body, the first and second side flanges as well as the mounting portion are each in the form of a complete ring. Alternatively, the main body, the first and second side flanges and the mounting portion may each be in the form of an open ring and only be present at the locations of the open ring formed by the conductive fibers.

[0031] The mounting plate is for example made of electrically conductive material.

[0032] The invention also relates to an electric machine or motor comprising a casing, a shaft and at least one grounding brush assembly as defined above mounted radially between the casing and the shaft, and in radial contact with said shaft, in particular by the free end of the conductive fibers.

[0033] The invention also relates to a method of assembling a grounding brush assembly as defined above comprising:

[0034] - An assembly step in which the fibers are brought axially into support conductive against the first flange inside the mounting portion of the mounting plate, the second flange axially extending the mounting portion on the side opposite the first flange in this mounting step; and

[0035] - An assembly step in which the second edge and said second edge is brought into contact against the conductive fibers. Brief description of the figures

[0036] 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:

[0037] [Fig-1] is an axial sectional view of a grounding brush assembly mounted radially between a rotating shaft and an electric motor housing;

[0038] [Fig.2] is a perspective view of a grounding brush assembly according to a first example of embodiment of the invention,

[0039] [Fig.3] is a front view of the grounding brush assembly of [Fig.2];

[0040] [Fig.4] is a sectional view along axis IV-IV of [Fig.3];

[0041] [Fig.5] is a sectional view along the VV axis of [Fig.3];

[0042] [Fig.6] is a sectional view corresponding to [Fig.4] during the assembly of the grounding brush assembly;

[0043] [Fig.7] is a perspective view of a grounding brush assembly according to a second example of embodiment of the invention;

[0044] [Fig.8] is a front view of the grounding brush assembly shown in [Fig.7];

[0045] [Fig.9] is a sectional view along the axis IX-IX of [Fig.8];

[0046] [Fig. 10] is a sectional view corresponding to [Fig.9] during assembly of the grounding brush assembly; Detailed description of the invention

[0047] In [Fig. 1] is shown, in axial section, a part of a motor 2 or electric machine comprising a fixed casing 4, a rotating shaft 6, of axis XX, supported radially by a rolling bearing 8. The bearing 8 is here of the ball type. Alternatively, it is possible to provide other rolling elements, or even a plain bearing.

[0048] The motor 2 further comprises a grounding brush assembly 10 mounted radially between the bore 12 of the casing 4 and the external cylindrical surface 14 of the rotating shaft 6.

[0049] The grounding brush assembly 10 makes it possible to continuously dissipate the electrical charges which accumulate on the shaft 6 of the motor 2 during operation of the motor 2 by transferring them to the casing 4.

[0050] As illustrated in Figures 2 and 3, the grounding brush assembly 10 has a generally annular shape. The assembly 10 includes a grounding brush 16 and a brush mounting plate 18 configured to axially and radially retain said brush 16.

[0051] The brush 16 comprises a plurality of individual conductive fibers 20 intended to come around the rotating shaft 6 of the motor 2. The conductive fibers 20 are for example made of carbon, stainless steel, conductive plastic, such as acrylic fibers or nylon. The plurality of conductive fibers 20 is in the form of an open ring. In the example illustrated, the conductive fibers 20 are folded around a connecting wire 21. The free distal end of the conductive fibers 20 is intended to come into radial contact with the outer surface 14 of the rotating shaft 6 of the motor 2.

[0052] The brush mounting plate 18 comprises a main body 22 and a centering means 24 extending from the main body 22.

[0053] As will be described in more detail later, the mounting plate 18 also includes a mounting portion 26, a first lateral flange 28 extending the main body 22 and a second lateral flange 30 for mounting and retaining the conductive fibers 20.

[0054] The main body 22 has an annular shape and comprises two opposite front faces 32, 34 which delimit the axial thickness of said main body 22. The main body 22 also comprises a cylindrical outer surface 36. The main body 22 extends substantially radially.

[0055] The centering means 24 of the mounting plate 18 is offset radially towards the outside relative to the mounting portion 26. The centering means 24 of the mounting plate 18 here comprises a plurality of centering tabs 38. Each centering tab 38 extends from the cylindrical outer surface 36 of the main body 22.

[0056] The centering tabs 38 are spaced from each other in the circumferential direction, here in a regular manner. Alternatively, it is possible to provide an irregular circumferential space. In the illustrated embodiment, the number of centering tabs 38 is eight. Alternatively, it is possible to provide a different number of centering tabs 38.

[0057] Each centering lug 38 is provided with a connection portion 40 extending the main body 22 outwards, and with a centering portion 42 extending at least axially the connection portion 40 and locally surrounding the mounting portion 26 while remaining radially at a distance from said mounting portion 26.

[0058] The centering portions 42 of the centering tabs 38 define the outer diameter of the mounting plate 18. The connecting portion 40 of each centering tab 38 connects the associated centering portion 42 to the main body 22 and extends radially outwardly the cylindrical outer surface 36 of the main body 22.

[0059] The centering portion 42 of each centering lug 38 axially extends a large diameter edge of the associated connecting portion 40. The centering portion 42 of each centering lug 38 is in the form of a cylindrical portion. The bore of the centering portion 42 of each centering lug 38 is radially spaced from the mounting portion 26 by a non-zero radial distance. In this exemplary embodiment, the centering portions 42 of the centering lugs 38 of the mounting plate 18 extend obliquely outward. Alternatively, the centering portions 42 may extend purely axially.

[0060] The centering portion 42 of each centering lug 38 comprises two opposite end faces 44, 46 which delimit said centering portion 42 in the circumferential direction. The centering portion 42 of each centering lug 38 extends continuously in the circumferential direction between its two end faces 44, 46. The end faces 44, 46 of each centering portion 42 are free.

[0061] As indicated previously, the first lateral edge 28 of the mounting plate 18 extends the main body 22 radially outwardly. The lateral edge 28 extends a small diameter edge of the main body 22. The lateral edge 28 is folded and comes to bear against the main body 22 to form a fold and locally obtain a double thickness of material. The lateral edge 28 comes to bear against the front face 34.

[0062] The mounting portion 26 of the mounting plate 18 extends the lateral flange 28. The mounting portion 26 extends the lateral flange 28 axially on the side opposite the main body 22. The mounting portion 26 extends a large diameter edge of the lateral flange 28. The mounting portion 26 here extends axially. Alternatively, the mounting portion 26 could extend obliquely.

[0063] The second lateral flange 30 of the mounting plate 18 extends the mounting portion 26 radially inward. The lateral flange 30 extends the mounting portion 26 on the side opposite the lateral flange 28.

[0064] The mounting portion 26 and the lateral flanges 28, 30 are annular in shape. The mounting portion 26 and the lateral flanges 28, 30 delimit a channel open radially on the inner side and inside which one end of the conductive fibers 20 is located. The lateral flanges 28, 30 axially enclose the conductive fibers 20. The conductive fibers 20 are axially supported on either side against the lateral flanges 28, 30.

[0065] In the illustrated embodiment, the conductive fibers 20 come to bear radially against the mounting portion 26.

[0066] In the illustrated example, the lateral flanges 28, 30 extend obliquely inwards from the mounting portion 26. Alternatively, the lateral flanges 28, 30 could extend radially.

[0067] In the illustrated embodiment, the lateral rim 30 has a reduced thickness compared to that of the first lateral rim 28 and that of the mounting portion 26. This reduced thickness makes it easier to fold the rim 30 to bring it into contact with the conductive fibers 20 as is described in more detail below.

[0068] The main body 22, the centering means 24, the first lateral rim 28, the mounting portion 26 and the second lateral rim 30 are made in one piece. The mounting plate 18 can for example be advantageously made by cutting and stamping. The mounting plate 18 is made of conductive material, such as for example aluminum, stainless steel, bronze, copper or other material.

[0069] The method of assembling the grounding brush assembly 10 is understood by observing, for example, Figures 4 and 6.

[0070] During a first mounting step, the plurality of conductive fibers 20 is placed inside the mounting portion 26 so that the plurality of conductive fibers 20 is in contact with the first lateral rim 28. During this first mounting step, the second lateral rim 30 axially extends the mounting portion 26.

[0071] The assembly method continues with a second assembly step in which the second lateral edge 30 is folded radially inwards to bringing it into contact with the conductive fibers 20 so as to keep the conductive fibers 20 axially sandwiched between the first and second lateral edges 28, 30. The second lateral edge 30 is for example crimped onto the plurality of conductive fibers 20. The reduced thickness of the second lateral edge 30 facilitates this folding step.

[0072] The embodiment illustrated in Figures 7 to 10, in which identical elements bear the same references, differs from the previous example in that the centering means 24 of the mounting plate 18 comprises an annular outer flange 50.

[0073] The annular outer flange 50 comprises an annular connecting portion 52 extending the main body 22 outwards, and an annular centering portion 54 extending at least axially the annular connecting portion 52 and surrounding the mounting portion 26 while remaining radially at a distance from said mounting portion 26.

[0074] The assembly of the grounding brush assembly 10 according to the second embodiment is done in two steps in a manner similar to the assembly of the grounding brush assembly 10 according to the first embodiment.

Claims

Claims

1. A grounding brush assembly (10) comprising a grounding brush (16) provided with a plurality of conductive fibers (20) and a brush mounting plate (18), the mounting plate (18) comprising a main body (22) and centering means (24) extending from the main body (22) and at least locally surrounding the grounding brush (16) while remaining radially spaced from said brush (16), characterized in that the mounting plate (18) is provided with a mounting portion (26) inside which the conductive fibers (20) of the grounding brush (16) are housed, and first and second opposite lateral flanges (28, 30) delimit a channel open radially on the inner side and inside which one end of the conductive fibers (20) is located, the flanges (28, 30) lateral axially enclosing said conductive fibers (20),the conductive fibers (20) being axially supported on either side against the lateral edges (28, 30), the first lateral edge (28) extending from the main body (22).,

2. An assembly (10) according to claim 1, wherein the first and second lateral flanges (28, 30) of the mounting plate (18) extend obliquely inwardly towards the conductive fibers (20) of the grounding brush (16).

3. An assembly (10) according to claim 1 or 2, wherein the conductive fibers (20) radially bear against the mounting portion (26) of the mounting plate (18).

4. Assembly (10) according to any one of the preceding claims, in which the first lateral edge (28) of the mounting plate (18) comes to bear against said main body (22) to form a fold and locally obtain a double thickness of material.

5. An assembly (10) according to any preceding claim, wherein the second lateral flange (30) of the mounting plate (18) has a reduced thickness relative to that of the first lateral flange (28) and the mounting portion (26).

6. Assembly (10) according to any one of the preceding claims, in which the mounting plate (18) is produced in one piece, in particular by stamping.

7. An assembly (10) according to any preceding claim, wherein the centering means (24) of the mounting plate (18)

8.

9.

10. comprises an annular outer flange (50), said flange (50) comprising an annular connecting portion (52) extending outwardly the main body (22), and an annular centering portion (54) extending at least axially the annular connecting portion (52) and surrounding the mounting portion (26) while remaining radially at a distance from said mounting portion (26).Assembly (10) according to any one of claims 1 to 6, wherein the centering means (24) of the mounting plate (18) comprises a plurality of centering tabs (38) extending from the main body (22) and spaced apart from each other in the circumferential direction, each centering tab (38) being provided with a connecting portion (40) extending outwardly the main body (22), and a centering portion (42) extending at least axially the connecting portion (40) and locally surrounding the mounting portion (26) while remaining radially at a distance from said mounting portion (26), said centering portion (42) being delimited in the circumferential direction by free front faces (44, 46).Electric motor (2) comprising a housing (4), a shaft (6) and at least one grounding brush assembly (10) according to any one of the preceding claims mounted radially between the housing (4) and the shaft (6), and in radial contact with said shaft (6). Method of assembling a grounding brush assembly (10) according to any one of the preceding claims, characterized in that it comprises: - a mounting step in which the conductive fibers (20) are brought axially into contact with the first rim (28) inside the mounting portion (26) of the mounting plate (18), the second rim (30) axially extending the mounting portion (26) on the side opposite the first rim (28) in this mounting step; and - an assembly step in which the second rim (30) is folded radially inwards and said second rim (30) is brought into contact with the conductive fibers (20).

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