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 holder 32 inside which the conductive fibers are mounted, and a brush mounting plate 40 which is integral with the brush holder 32. The grounding brush 30 is in the form of an open ring and is provided with a first end 30a and a second end 30b spaced apart and circumferentially facing each other. The mounting plate comprises at least one anti-rotation tab 50 extending into the circumferential space separating the first and second ends 30a, 30b of the grounding brush. Reference: Figure 3

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 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] With such a grounding brush assembly, there may occur in operation when the shaft of the associated electrical machine is rotating, a loss contact between the mounting plate and the bracket, which limits the flow of electrical current through the assembly.

[0009] The present invention aims to remedy this drawback. Summary of the invention

[0010] 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.

[0011] The grounding brush is in the form of an open ring and is provided with a first end and a second end spaced from the first end, said ends being circumferentially opposite each other.

[0012] The first and second ends define the circumferential length of the brush.

[0013] According to a general characteristic, the mounting plate comprises at least one anti-rotation tab extending into the circumferential space separating the first and second ends of the grounding brush.

[0014] Said tab of the mounting plate forms a means for locking the brush in rotation in the event of circumferential movement of the brush relative to the mounting plate. Said tab makes it possible to lock the brush in rotation by contact in the circumferential direction with one of the ends of the brush.

[0015] This avoids the risk of frictional wear and heating between the mounting plate and the support for the conductive fibers. This prevents heating and the occurrence of electroerosion which can lead to a loss of contact between the mounting plate and the support. The passage of electric current through the assembly is thus carried out safely during operation.

[0016] No additional means on the mounting plate and / or on the brush are provided to ensure this anti-rotation function by axial interference.

[0017] The mounting plate may comprise a plurality of brush holder retaining tabs. Preferably, said anti-rotation tab of the mounting plate is distinct from the retaining tabs.

[0018] The mounting plate may comprise an annular radial portion against which the grounding brush axially bears. In this case, the brush support may axially bear against the radial portion of the mounting plate.

[0019] In a particular embodiment, the retaining tabs of the mounting plate extend from the radial portion of the mounting plate. Alternatively, the retaining tabs of the mounting plate may extend from another portion of the mounting plate.

[0020] 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.

[0021] According to one design, said anti-rotation tab extends from the radial portion of the mounting plate.

[0022] Alternatively, said anti-rotation tab may extend from another portion of the mounting plate, for example retaining tabs or the centering portion.

[0023] Preferably, the mounting plate is made in one piece.

[0024] Advantageously, said anti-rotation tab of the mounting plate is formed at less by plastic deformation of said mounting plate. Said anti-rotation tab may be formed by cutting and plastic deformation of the mounting plate.

[0025] Alternatively, the mounting plate could be obtained by other manufacturing processes, for example by additive manufacturing, i.e. by any manufacturing process based on the construction of the mounting plate layer by layer by addition of material. In this case, the anti-rotation tab(s) are obtained during the manufacture of the mounting plate.

[0026] 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

[0027] 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:

[0028] [Fig-1] is an axial sectional view of a grounding brush assembly mounted radially between a rotating shaft and an electric motor housing,

[0029] [Fig.2]

[0030] [Fig.3] are perspective views of a grounding brush assembly according to a first exemplary embodiment of the invention,

[0031] [Fig.4] is a front view of the grounding brush assembly of Figures 2 and 3,

[0032] [Fig.5] is a sectional view along the VV axis of [Fig.4],

[0033] [Fig.6] is a perspective view of a grounding brush assembly according to a second example of embodiment of the invention,

[0034] [Fig.7] is a front view of the grounding brush assembly of [Fig.6],

[0035] [Fig.8] is a perspective view of a grounding brush assembly according to a third example of embodiment of the invention,

[0036] [Fig.9] is a front view of the grounding brush assembly of [Fig.8],

[0037] [Fig. 10]

[0038] [Fig. 11] are perspective views of a grounding brush assembly according to a third exemplary embodiment of the invention,

[0039] [Fig. 12] is a front view of the grounding brush assembly of Figures 10 and 11. Detailed description of the invention

[0040] In [Fig. 1] 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.

[0041] 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.

[0042] 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.

[0043] With reference to Figures 2 to 5, a grounding brush assembly 20 according to a first example will now be described.

[0044] 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 axially and radially retain said brush 30.

[0045] As will be described in more detail later, the brush mounting plate 40 is also configured to rotationally lock the brush 30.

[0046] 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.

[0047] 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 material electrically non-conductive with a conductive coating or conductive paint.

[0048] As illustrated more visibly in [Fig.5], 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.

[0049] The mounting portion 34 and the two lateral flanks 36, 38 delimit a channel open radially on the inner side and inside which the conductive fibers 31 are partly located.

[0050] 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.

[0051] 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.

[0052] As indicated previously, the brush 30 is in the form of an open ring and is provided with a first end 30a and a second end 30b opposite each other which is circumferentially spaced from the first end, as can be seen in particular in FIGS. 3 and 4. The first and second ends 30a, 30b are circumferentially spaced from each other. Such circumferential spacing between two ends of the brush 30 allows the brush to adapt to different diameters of the motor shaft.

[0053] Generally, the first end 30a of the brush and the second end 30b are not fixed to each other. Alternatively, it remains possible to fix the first end and the second end of the brush 30 to each other.

[0054] In the illustrated embodiment, each of the first and second ends 30a, 30b is formed both by the conductive fibers 31 and by the support 32. Alternatively, each of the first and second ends 30a, 30b may be formed solely by the conductive fibers 31 or by the support 32, if the conductive fibers 31 extend circumferentially projecting relative to the support 32 or vice versa.

[0055] The brush mounting plate 40 includes an annular radial portion 42, and a plurality of axially and radially retaining tabs 44 for the brush 30 extending from the radial portion 42.

[0056] 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.

[0057] 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.

[0058] The tabs 44 are spaced from one another 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.

[0059] 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 support 32 is held axially in abutment against the radial portion 42 of the mounting plate by the tabs 44. The tabs 44 make it possible to retain the earthing brush 30 axially and radially. The lateral flank 36 of the support bears against the radial portion 42 of the mounting plate and the lateral flank 38 bears against the tabs 44. The tabs 44 are here identical to each other.

[0060] As illustrated more visibly in [Fig.5], each tab 44 comprises an axial portion 44a extending axially from the radial portion 42, locally radially surrounding the support 32 and is in radial contact therewith, and a radially inwardly folded portion 44b which is provided at the free end of the axial portion. The folded portion 44b of each tab makes it possible to axially retain the support 32 of the earthing brush 30. The folded portion 44b of each tab is in axial contact against the lateral flank 38 of the support.

[0061] 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 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.

[0062] 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.

[0063] 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.

[0064] As illustrated in Figures 2 to 4, 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.

[0065] As previously indicated, the brush mounting plate 40 is also configured to rotationally lock the brush 30.

[0066] For this purpose, the mounting plate 40 comprises an anti-rotation tab 50 extending into the circumferential space separating the first and second ends 30a, 30b of the brush. The tab 50 extends from the radial portion 42. The tab 50 extends axially projecting relative to the radial portion 42. The tab 50 extends circumferentially into the space separating the first and second ends 30a, 30b of the brush.

[0067] The lug 50 is circumferentially opposite the first and second ends 30a, 30b of the brush. A circumferential clearance is provided on the one hand between the lug 50 and the first end 30a of the brush, and on the other hand between the lug 50 and the second end 30b of the brush. This allows the brush 30 to retain its ability to adapt to different diameters of the motor shaft.

[0068] The tab 50 is distinct from the tongues 44. The tab 50 is located in the circumferential direction between two successive tongues 44.

[0069] The tab 50 is formed by cutting and folding the radial portion 42. A window 52 is formed on the radial portion 42 during this cutting to allow the tab to remain. 50. The window 52 is here a through window. The window 52 axially crosses the thickness of the radial portion 42. The window 52 opens radially inwards.

[0070] In the illustrated embodiment, the tab 50 comprises a radially inwardly folded portion 50a which extends from the radial portion 42, and an axial portion 50b extending the folded portion 50a and extending into the circumferential space separating the first and second ends 30a, 30b of the brush.

[0071] In the illustrated embodiment, one of the tabs 46 locally radially surrounds the tab 50. In the illustrated embodiment, the root of the tab 50 is located radially at the periphery of the radial portion 42 of the mounting plate. In other words, the root of the tab 50 is located radially on the side of the large diameter edge of the window 52. Alternatively, the tab 50 could be formed on the radial portion 42 so that its root is located radially on the inner side of the radial portion 42. In this case, the root of the tab 50 would extend from the small diameter edge of the window 52 and the window would not open radially inwards.

[0072] In the event of circumferential movement of the brush 30 relative to the mounting plate 40, the tab 50 thereof makes it possible to lock the brush in rotation by contact in the circumferential direction against the first or second end 30a, 30b of the brush.

[0073] The embodiment illustrated in Figures 6 and 7, in which identical elements bear the same references, differs from the first example illustrated in that the mounting plate 40 comprises an anti-rotation tab 60 extending from one of the two lateral edges of the window 52. The root of the tab 60 thus extends here from said lateral edge of the window 52.

[0074] The tab 60 extends axially projecting relative to the radial portion 42. The tab 60 extends into the circumferential space separating the first and second ends 30a, 30b of the brush. The tab 60 comprises an axially folded portion 60a which extends from the lateral edge of the window 52, ​​and an axial portion 60b extending the folded portion 60a and extending into the circumferential space separating the first and second ends 30a, 30b of the brush.

[0075] The tab 60 is circumferentially opposite the first and second ends 30a, 30b of the brush. A circumferential clearance is also provided on the one hand between the tab 60 and the first end 30a of the brush, and on the other hand between the tab 60 and the second end 30b of the brush, the values ​​of the clearances being different here. Alternatively, the values ​​of the clearances could be equal.

[0076] The embodiment illustrated in Figures 8 and 9, in which identical elements bear the same references, differs from the previous embodiment in that the mounting plate 40 comprises an additional anti-rotation tab 62. extending from the lateral edge of the window 52 opposite that from which the tab 60 extends. The tab 62 also extends into the circumferential space separating the first and second ends 30a, 30b of the brush.

[0077] The tab 62 extends axially projecting relative to the radial portion 42. The tab 62 comprises an axially folded portion 62a which extends from the lateral edge of the window 52 opposite the tab 60, and an axial portion 62b extending the folded portion 62a and extending into the circumferential space separating the first and second ends 30a, 30b of the brush.

[0078] The tab 60 is circumferentially opposite the first end 30a of the brush and the tab 62 is circumferentially opposite the second end 30b of the brush while remaining at a distance from them.

[0079] The embodiment illustrated in Figures 10 to 12, in which identical elements bear the same references, differs from the first example illustrated in that the mounting plate 40 comprises an anti-rotation tab 70 extending from the radial portion 42, and folded back on itself and on the radial portion 42 to locally form a double thickness of material.

[0080] The tab 70 extends into the circumferential space separating the first and second ends 30a, 30b of the brush. The tab 70 extends axially projecting relative to the radial portion 42. The tab 70 extends circumferentially into the circumferential space separating the first and second ends 30a, 30b of the brush. The tab 70 comprises a radial portion 70a extending radially outward from the radial portion 42 and a folded portion 70b extending the radial portion 70a and folded axially against said radial portion. Alternatively, the radial portion 70a of the tab could extend radially inward.

[0081] The folded portion 70b of the tab extends into the circumferential space separating the first and second ends 30a, 30b of the brush. The tab 70 is circumferentially opposite the first and second ends 30a, 30b of the brush. A circumferential clearance is provided on the one hand between the tab 70 and the first end 30a of the brush, and on the other hand between the tab 70 and the second end 30b of the brush. In this exemplary embodiment, the tab 70 is situated circumferentially between two of the successive tabs 46.

[0082] In the illustrated embodiments, the anti-rotation tab(s) of the mounting plate remain circumferentially spaced from the first and second ends 30a, 30b of the grounding brush. Alternatively, it could be possible to provide contact of the anti-rotation tab(s) of the mounting plate with one of the ends 30a, 30b of the grounding brush, or even with both ends 30a, 30b.

[0083] In the illustrated embodiments, each leg of the mounting plate 40 extends axially projecting relative to the lateral flank 36 of the support but remains axially set back relative to the lateral flank 38. Alternatively, the tab could also extend axially projecting relative to the lateral flank 38 of the support.

[0084] 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. A grounding brush assembly (20) comprising a grounding brush (30) provided with a plurality of conductive fibers (31) and a holder (32) within which the conductive fibers are mounted, and a brush mounting plate (40) which is integral with the brush holder (32), the grounding brush (30) being in the form of an open ring and being provided with a first end (30a) and a second end (30b) spaced apart and circumferentially facing each other, characterized in that the mounting plate (40) comprises at least one anti-rotation tab (50; 60; 60, 62; 70) extending into the circumferential space separating the first and second ends (30a, 30b) of the grounding brush.

2. An assembly according to claim 1, wherein the mounting plate (40) comprises a plurality of tabs (44) for retaining the brush holder (32).

3. An assembly according to claim 2, wherein said anti-rotation tab (50; 60; 60, 62; 70) of the mounting plate is distinct from the retaining tabs (44).

4. 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.

5. An assembly according to claim 4, wherein said anti-rotation tab (50; 60; 60, 62; 70) extends from the radial portion (42) of the mounting plate.

6. An assembly according to claim 4 or 5 dependent on claim 2, wherein the mounting plate retaining tabs (44) extend from the radial portion (42) of the mounting plate.

7. An assembly according to any one of claims 4 to 6, wherein the brush support (32) bears axially against the radial portion (42) of the mounting plate.

8. An assembly according to any one of claims 4 to 7, wherein the mounting plate (40) comprises at least one centering portion (32) extending at least axially the radial portion (42), offset radially outwards relative to the support (22) and provided with an outer surface defining the outer diameter of the mounting plate (40). assembly (18).

9. An assembly according to any preceding claim, wherein said anti-rotation tab (50; 60; 60, 62; 70) is formed at least by plastic deformation 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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