Grounding Brush Set

Abstract

[Grounding brush assembly] The grounding brush assembly 20 comprises a grounding brush 30 provided with a plurality of conductive fibers 31 and a support 32 inside which the conductive fibers are mounted, and a brush mounting plate 40 which is integral with the support 32 of the brush. The mounting plate 40 comprises a plurality of tabs 44 for centering the support 32 of the brush, and a plurality of means 50 for securing said centering tabs with the support 32, said securing means 50 being distinct from the support 32 and the centering tabs 44. Reference: Figure 4

Description

Title of the invention: Grounding brush set 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 to grounding brush sets. State of the prior art

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

[0003] During operation when the shaft is rotating, an electrical potential difference can appear between it and the housing of the motor or machine, which generates an electric current between the inner ring of the rolling bearing which is fixed to the shaft, and the outer ring fixed to the housing.

[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 plurality of conductive fibers, a support inside which the conductive fibers are mounted, and an annular mounting plate comprising a plurality of radial and axial retaining tabs of the support and an annular outer flange radially surrounding said brush and the tabs.

[0008] The tabs providing axial and radial retention of the support are formed by cutting and folding a radial portion of the mounting plate which is axially in support with the support.

[0009] In order to be able to create these retaining tabs, it is necessary to make large cutouts in the radial portion of the mounting plate. This reduces the mechanical resistance of the mounting plate to the forces exerted during its assembly in the bore of the associated electric motor housing.

[0010] Furthermore, given the folded length of the retaining tabs, stress concentration phenomena appear during this folding of the tabs on the brush support.

[0011] The present invention aims to remedy these drawbacks. Summary of the invention

[0012] A grounding brush assembly includes a grounding brush having a plurality of conductive fibers and a holder within which the conductive fibers are mounted. The assembly also includes a brush mounting plate that is secured to the brush holder.

[0013] According to a general characteristic, the mounting plate comprises a plurality of tabs for centering the brush support.

[0014] According to another general characteristic, the assembly further comprises a plurality of means for securing said centering tabs to the support. Said securing means are separate from the support and the centering tabs.

[0015] With this design, the folded length of the tongues can be reduced inasmuch as they only fulfill a radial centering function and not an axial retaining function, which limits the stress concentration phenomena on the mounting plate. In addition, the dimension of the cutouts provided on the mounting plate for the formation of the tongues is also reduced.

[0016] Preferably, said securing means can be made of an electrically conductive material. This further helps to promote the dissipation of electric charges.

[0017] Said securing means can include glue and / or an adhesive and / or a weld and / or a brazing.

[0018] According to a first design, each securing means at least partly covers the free end of the associated centering tongue and the adjacent area of the support.

[0019] According to a second alternative design, each securing means is interposed radially between the associated centering tab and the support.

[0020] According to a third design, each securing means covers the free end of the associated centering tab and the adjacent area of ​​the support, and is interposed radially between the associated centering tab and the support.

[0021] In one embodiment, the brush support comprises a mounting portion and two lateral flanks extending the mounting portion and axially enclosing the conductive fibers. One of the lateral flanks of the support may be axially supported against the mounting plate.

[0022] Preferably, the centering tabs of the mounting plate remain axially set back from the other lateral flank of the support. This further facilitates obtaining a short tab length.

[0023] The mounting plate may comprise an annular radial portion against which the grounding brush axially bears. In this case, said lateral flank of the brush support may axially bear against the radial portion of the mounting plate.

[0024] In a particular embodiment, the centering tabs extend from the radial portion of the mounting plate. Alternatively, the centering tabs may extend from another portion of the mounting plate.

[0025] In one embodiment, the mounting plate comprises at least one centering portion extending at least axially the radial portion, offset radially outwardly relative to the support and provided with an outer surface defining the outer diameter of the mounting plate.

[0026] Preferably, the mounting plate is made in one piece.

[0027] The invention also relates to an electric motor comprising a casing, a shaft and at least one grounding brush assembly as defined previously and mounted radially between the casing and the shaft, the conductive fibers of the brush of said assembly being in contact with the shaft. Brief description of the figures

[0028] 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:

[0029] [Fig-1] is an axial sectional view of a grounding brush assembly mounted radially between a rotating shaft and an electric motor housing,

[0030] [Fig.2] is a perspective view of a grounding brush assembly according to a first exemplary embodiment of the invention,

[0031] [Fig.3] is a front view of the grounding brush assembly of [Fig.2],

[0032] [Fig.4] is a sectional view along axis IV-IV of [Fig.3],

[0033] [Fig.5] is a sectional view of a grounding brush assembly according to a second example of embodiment of the invention, and

[0034] [Fig.6] is a perspective view of the grounding brush assembly of [Fig.5]. Detailed description of the invention

[0035] In [Fig.l] is shown, in axial section, a part of a motor 10 or electric machine comprising a fixed casing 12, a rotating shaft 14, of axis XX, supported radially by a rolling bearing 16. The bearing here is of the ball type. Alternatively, it is possible to provide other rolling elements, or even a plain bearing.

[0036] The motor 10 further comprises a grounding brush assembly 20 mounted radially between the bore 12a of the housing 12 and the outer cylindrical surface 14a of the rotating shaft 14.

[0037] The grounding brush assembly 20 allows for the continuous dissipation of electrical charges that accumulate on the motor shaft 14 during operation of the motor by transferring them to the housing 12.

[0038] With reference to Figures 2 to 4, a grounding brush assembly 20 according to a first example will now be described.

[0039] The grounding brush assembly 20 has a generally annular shape. The assembly 20 includes a grounding brush 30 and a brush mounting plate 40 configured to radially center said brush 30.

[0040] As will be described in more detail later, the brush mounting plate 40 is secured to the brush 30 by attached means.

[0041] The brush 30 comprises a plurality of individual conductive fibers 31 intended to come around the rotating shaft of the motor. The conductive fibers 31 can be made of carbon, stainless steel, conductive plastics, such as acrylic fibers or nylon.

[0042] The brush 30 further comprises a holding member or support 32 inside which the conductive fibers 31 are mounted. In the illustrated embodiment, the support 32 is in the form of an open ring. The support 32 can be made by cutting and stamping. The support 32 is made of electrically conductive material, such as for example aluminum, stainless steel, bronze, copper or other material. Alternatively, the support 32 can be made of electrically non-conductive material with a conductive coating or conductive paint.

[0043] As illustrated more visibly in [Fig. 4], the support 32 comprises an axial mounting portion 34 and two opposite lateral flanks 36, 38 extending from the mounting portion 34 inwards and axially enclosing the conductive fibers 31. The conductive fibers 31 are axially supported on either side against the lateral flanks 36, 38. The conductive fibers 31 are axially supported on either side against the internal faces of the lateral flanks 36, 38.

[0044] The mounting portion 34 and the two lateral flanks 36, 38 delimit a channel radially open on the inner side and inside which the conductive fibers 31 are partly located.

[0045] In the illustrated example, the conductive fibers 31 are folded around a connecting wire 39 of the support 32. The free distal end of the conductive fibers 31 is intended to come into radial contact with the outer surface of the rotating shaft of the motor. The proximal end of the conductive fibers 31 is in radial contact with the mounting portion 34 of the support.

[0046] The lateral flank 36 extends one end of the mounting portion 34 and the lateral flank 38 extends the opposite end thereof. The lateral flanks 36, 38 extend obliquely inwardly from the mounting portion 34. The lateral flanks 36, 38 are symmetrical to each other with respect to a median radial plane of the support 32. The mounting portion 34 here extends axially. Alternatively, the mounting portion 34 could extend obliquely. Alternatively, the lateral flanks 36, 38 could not be symmetrical.

[0047] As indicated previously, the brush 30 is in the form of an open ring, as seen in particular in FIGS. 2 and 3. This allows the brush to adapt to different diameters of the motor shaft. Generally, the ends of the brush are not fixed to each other. Alternatively, it remains possible to fix these ends of the brush 30 to each other.

[0048] The mounting plate 40 is made by cutting and stamping. The mounting plate 40 is made of a conductive material, such as, for example, aluminum, stainless steel, bronze, copper, or other material. Alternatively, the mounting plate 40 may be made of an electrically non-conductive material with a conductive coating or a conductive paint.

[0049] Referring to Figures 2 and 4, the brush mounting plate 40 includes an annular radial portion 42, and a plurality of centering tabs 44 extending from the radial portion 42.

[0050] The radial portion 42 of the mounting plate is axially supported against the support 32 of the brush 30. More precisely, the radial portion 42 is axially supported against the lateral flank 36 of the support.

[0051] The tabs 44 are spaced from each other in the circumferential direction, here in a regular manner. Alternatively, it could be possible to provide an irregular circumferential spacing. In the illustrated embodiment, there are eight tabs 44. Alternatively, it is possible to provide a greater or even smaller number of tabs 44. It is possible to provide two tabs 44, or at least four tabs. Preferably, the number of tabs 44 is at least two.

[0052] Each tab 44 extends axially projecting relative to the radial portion 42. Each tab 44 locally radially surrounds the support 32 of the brush 30 and is in radial contact with the mounting portion 34 of said support. The tabs 44 are here identical to each other.

[0053] As illustrated more visibly in [Fig. 4], each tab 44 consists of an axial portion extending axially from the radial portion 42, locally radially surrounding the support 32 and is in radial contact with the latter. Each tab 44 is devoid of a folded portion at the free end of the axial portion. In the illustrated embodiment, each tab 44 remains axially set back relative to the lateral flank 38 of the supports

[0054] The brush mounting plate 40 also includes a plurality of centering tabs 46 extending from the radial portion 42 and spaced apart from each other in the circumferential direction. A notch 48 ([Fig.2]) is formed on the radial portion 42 between each immediately successive pair of tabs 46. The tabs 46 are formed by cutting and bending the radial portion 42.

[0055] Each tab 46 axially extends the radial portion 42. The tabs 46 extend obliquely from a large diameter edge of the radial portion 42. The tabs 46 here extend axially on the same side as the tabs 44. Alternatively, the tabs 46 could extend axially on the opposite side.

[0056] Each tab 46 locally radially surrounds the support 32 of the brush 30 while remaining at a distance from the latter. The tabs 46 are offset radially outwards in part relative to the tabs 44. The tabs 46 are here identical to each other. The tabs 46 define the outer diameter of the mounting plate 40. Each tab 46 extends here obliquely. Alternatively, the tabs 46 could extend axially. Each tab 46 is in the form of a portion of a cylinder. The bore of each tab 46 is radially spaced from the support 32 by a non-zero radial distance. The outer surfaces of the tabs 46 define the outer diameter of the mounting plate 40. The tabs 46 allow the mounting plate to be centered after mounting in the bore of the housing of the associated electric motor.

[0057] As illustrated in Figures 2 and 3, the tabs 46 are spaced from each other in the circumferential direction, here in a regular manner. Alternatively, it could be possible to provide an irregular circumferential spacing. Each tab 46 is located in the circumferential direction between two immediately successive tabs 44. Each tab 46 is spaced in the circumferential direction from the two immediately adjacent tabs 44. Each tab 46 here has a circumferential dimension greater than that of the tabs 44.

[0058] As previously indicated, the brush mounting plate 40 is integral with the brush 30.

[0059] For this purpose, the assembly 20 comprises securing means 50 (figures 2 to 4) each associated with one of the tabs 44 of the mounting plate and with the support 32. The number of securing means 50 is therefore equal to the number of tabs 44.

[0060] The securing means 50 are elements distinct from the tabs 44 and the support 32, and are attached to them.

[0061] In the illustrated embodiment, each securing means 50 is provided between the free end of the associated tab 44 of the mounting plate and the adjacent area of ​​the support 32. More specifically, each securing means 50 is provided between the free end of the associated tab 44 and the adjacent area of ​​the outer surface of the mounting portion 34 of the support. Each securing means 50 covers the free end of the associated tab 44 and locally covers the outer surface of the mounting portion 34 of the support. Each securing means 50 here comprises a weld. Each tab 44 of the mounting plate is in direct radial contact with the mounting portion 34 of the support by being welded thereto. Alternatively, the securing means 50 could comprise at least one of: a glue, an adhesive or a solder.

[0062] The support 32 is held axially against the radial portion 42 of the mounting plate by the securing means 50. The tabs 44 only allow the radial centering of the brush 30.

[0063] Advantageously, each securing means 50 is made of electrically conductive material to promote the dissipation of electrical charges. Thus, the electrical charges which accumulate on the shaft 6 during operation of the electric machine 2 are dissipated towards the casing 4 through the conductive fibers 20, the support 32 of the brush 16, the securing means 50 and the mounting plate 18. It remains possible, however, to provide for the securing means 50 to be made of a non-electrically conductive material.

[0064] The embodiment illustrated in Figures 5 and 6, in which identical elements bear the same references, differs mainly from the first example illustrated in that the assembly 20 comprises a securing means 52 interposed radially between each of the tabs 44 of the mounting plate and the support 32. Each securing means 52 is interposed radially between the inner surface of the associated tab 44 and the outer surface of the mounting portion 34 of the support. Each tab 44 is in indirect radial contact with the mounting portion 34 of said support, the associated securing means 52 being interposed radially between them.

[0065] In this exemplary embodiment, the tabs 44 of the mounting plate have an increased axial dimension. The tabs 44 extend to the vicinity of the lateral flank 38 of the support while remaining axially set back relative to the latter. Each securing means 52 may comprise glue and / or an adhesive. preferably, each securing means 52 is made of electrically conductive material to promote the dissipation of electrical charges. Alternatively, the securing means 52 may be made of a non-electrically conductive material.

[0066] In the illustrated embodiments, the tabs 44 of the mounting plate remain axially set back relative to the lateral flank 38 of the brush support. Alternatively, the tabs 44 could extend axially projecting relative to the lateral flank 38 of the support. In this case, it may be possible to provide that the securing means associated with each tab is provided between the inner surface thereof, and the outer surface of the mounting portion 34 of the support and / or the outer face of the lateral flank 38.

[0067] In the described embodiments, the tabs 44 of the mounting plate are fixed to the support 32 solely by means of the securing means 50 or 52. Alternatively, it could be possible to provide, in combination with the securing means, radial interference of the tabs 44 of the mounting plate against the support 32 so that the mounting portion 34 of the support has, in the assembled state in the area of ​​each retaining tab 44, an outside diameter strictly less than its outside diameter in the free, i.e. unassembled, state.

[0068] In the illustrated embodiments, the mounting plate 40 of the grounding brush assembly includes a plurality of centering tabs 46. Alternatively, the tabs could be replaced by an annular flange forming an annular centering portion.

Claims

Claims

1. Grounding brush assembly (20) comprising a grounding brush (30) provided with a plurality of conductive fibers (31) and a support (32) inside which the conductive fibers are mounted, and a brush mounting plate (40) which is integral with the support (32) of the brush, characterized in that the mounting plate (40) comprises a plurality of tabs (44) for centering the support (32) of the brush, and in that said assembly comprises a plurality of securing means (50; 52) of said centering tabs with the support (32), said securing means (50; 52) being distinct from the support (32) and the centering tabs (44).

2. Assembly according to claim 1, in which said securing means (50; 52) are made of electrically conductive material.

3. An assembly according to claim 1 or 2, wherein said securing means (50; 52) comprise glue and / or an adhesive and / or a weld and / or a brazing.

4. Assembly according to any one of the preceding claims, in which each securing means (50) at least partially covers the free end of the associated centering tab (44) and the adjacent zone of the support (32).

5. Assembly according to any one of claims 1 to 3, in which each securing means (52) is interposed radially between the associated centering tab (44) and the support (32).

6. Assembly according to any one of the preceding claims, in which the support (32) of the brush comprises a mounting portion (34) and two lateral flanks (36, 38) extending the mounting portion and axially enclosing the conductive fibers (31), one of the lateral flanks (36, 38) of the support being axially in abutment against the mounting plate.

7. An assembly according to claim 6, wherein the centering tabs (44) of the mounting plate remain axially set back from the other lateral flank (38) of the support.

8. An assembly according to any one of the preceding claims, wherein the mounting plate (40) comprises an annular radial portion (42) against which the earthing brush (30) axially bears.

9. An assembly according to claim 8, wherein the tabs (44) of centering extend from the radial portion (42) of the mounting plate.

10. An electric motor comprising a housing (12), a shaft (14) and at least one grounding brush assembly (20) according to any preceding claim mounted radially between the housing (12) and the shaft (14), the conductive fibers of the brush of said assembly being in contact with the shaft.

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