Assembly of internally branched grounding brushes comprising axially extending conductive fibers

Abstract

An internally bypassed grounding brush assembly with axially extending conductive fibers. This grounding brush assembly is for an electrical machine comprising a rotating shaft, an outer casing, one or more bearings coupling the shaft to the casing, and a fixed shaft extending through the rotating shaft and electrically grounded. The grounding brush assembly includes an inner conductive base with a bore sized to receive a portion of the fixed shaft and a radial surface. An outer conductor can mesh with the inner circumferential surface of the rotating shaft and has a radial contact surface.A conductive brush is coupled to the base element and comprises a plurality of conductive fibers extending axially from the radial surface of the base element and circumferentially around the centerline, each conductive fiber having a first axial end coupled to the base element and a second opposite axial end meshed with the radial surface of the outer conductor to produce a conductive path or conductive paths. Reference: Figure 1.

Description

Title of the invention: Assembly of internally bypassed grounding brushes comprising axially extending conductive fibers Cross-reference

[0001] This application claims priority from Italian patent application number 102024000016096 filed on July 11, 2024, the contents of which are incorporated herein in full by reference. Technical field of the invention

[0002] The present invention relates to grounding devices for bearings, and more particularly to assemblies of grounding brushes for diverting currents away from bearings. Prior art

[0003] In electrical machines, such as an electric motor, a generator, etc., the machine usually comprises a shaft that can rotate about a central axis, an outer casing, and at least one bearing connecting the shaft to the casing. Such bearings generally comprise an inner ring mounted on the rotating shaft, an outer ring disposed around the inner ring and meshed with the casing, and a plurality of rolling elements arranged between the inner and outer rings. During operation, an electrical charge can accumulate on the shaft, which can generate an electric current that flows from the shaft, through the bearing, and into the outer casing. These currents can cause damage to the raceways of the inner and outer rings as well as to the rolling elements.

[0004] To prevent damage to the bearings, it is known to provide a grounding brush assembly that provides a conductive path between the shaft and the housing to divert the current away from the bearing(s). Such a grounding brush assembly usually comprises a support or retaining device connected to the housing and a brush attached to the support / retaining device and having a plurality of conductive fibers extending radially inward from the retaining device and in contact with the outer surface of the shaft, or a sleeve or other component mounted on the shaft. Alternatively, the retaining device may be mounted on the shaft and have a plurality of fibers oriented radially outward in contact with an inner circumferential surface of the housing. Summary of the invention

[0005] In one aspect, the present invention is an assembly of grounding brushes for an electrical machine, the electrical machine comprising a rotating shaft that can The rotating shaft rotates about a central axis and has an inner circumferential surface defining a hollow bore, an outer housing, at least one bearing rotatingly coupling the shaft to the housing, and a fixed shaft extending through the bore of the rotating shaft and electrically grounded. The grounding brush assembly comprises an annular inner conductive base element having a bore dimensioned to receive a portion of the fixed shaft and a centerline that can be aligned coaxially with the central axis. An annular outer conductor can mesh with the inner circumferential surface of the rotating shaft, and a conductive brush is coupled to the conductive base element and has a plurality of conductive fibers extending axially along the centerline and circumferentially around it.Each conductive fiber has a first axial end coupled to the basic element and a second opposite axial end meshed with the outer conductor such that at least one conductive path extends from the rotating shaft, through the outer conductor, the brush and the basic element, and to the stationary shaft.

[0006] Preferably, the basic conductive element comprises an annular hub having an inner circumferential surface providing the bore of the basic element and a radial rim extending radially outwards from the hub, the conductive brush being fixed to the radial rim of the basic element. The outer conductor preferably comprises an axial portion that can mesh with the rotating shaft so as to couple the outer conductor to the rotating shaft and a radial rim extending radially inwards from the axial portion, the second axial end of each fiber among the plurality of conductive fibers of the conductive brush being meshed with the radial rim of the outer conductor.

[0007] Furthermore, the conductive brush preferably comprises an annular retaining element having a circumferential channel, the first axial end of each fiber among the plurality of conductive fibers being disposed inside the circumferential channel, and the radial edge of the conductive base member having at least one and preferably a plurality of retaining tabs, each engaging with the annular retaining element of the conductive brush to couple the brush to the base member. Moreover, the grounding brush assembly preferably further comprises at least one centering bearing having an inner ring that can be disposed around the fixed shaft and an outer ring that engages with the inner circumferential surface of the rotating shaft, the at least one centering bearing being disposed against the base member or axially spaced from it. Brief description of the figures

[0008] The above summary, as well as the detailed description of preferred embodiments of the present invention, are best understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, currently preferred embodiments are shown in the drawings, which are schematic. It should be understood, however, that the present invention is not limited to the specific arrangements and instruments shown. In the drawings:

[0009] [Fig.1] is an axial cross-sectional view of an electrical machine comprising a set of grounding brushes according to the present invention;

[0010] [Fig.2] is an axial cross-sectional view of a first construction of the grounding brush assembly, shown installed between an external rotating shaft and an internal fixed shaft;

[0011] [Fig. 3] is a perspective view of a basic organ and a brush of the first construction of the [Fig.2];

[0012] [Fig.4] is an exploded perspective view of the basic organ and the brush of [Fig.3];

[0013] [Fig. 5] is an axial cross-sectional view of a second construction of the grounding brush assembly, shown installed between an outer rotating shaft and an inner fixed shaft; and

[0014] [Fig. 6] is an axial cross-sectional view of a third construction of the grounding brush assembly, shown installed between an outer rotating shaft and an inner fixed shaft. Detailed description of the invention

[0015] Certain terminology is used in the following description solely for convenience and is not exhaustive. The words "inside," "inward," and "outside," "outward," refer to directions toward and away from, respectively, a designated centerline or geometric center of an element being described, the particular meanings being clear from the context of the description. Furthermore, as used here, the words "connected" and "coupled" are each understood to involve direct connections between two organs without any other organ interposed between them and indirect connections between organs in which one or more other organs are interposed between them. The terminology includes the words specifically mentioned above, their derivatives, and words of similar meaning.

[0016] Referring now to the detailed drawings, where similar numbers are used to indicate similar elements throughout, Figures 1 to 6 show an assembly of grounding brushes 10 for an electrical machine 1. The electrical machine 1 has a rotating shaft 2 that can rotate about an axis central Ac and having an inner circumferential surface 2a defining a hollow bore 3, an outer housing 4, at least one bearing 5 rotatingly coupling the shaft 2 to the housing 4, and a fixed shaft 6 extending through the bore 3 of the rotating shaft 2 and electrically grounded. The grounding brush assembly 10 essentially comprises an inner conductive base element 12 disposed around the fixed shaft 6, an outer conductor 14 that can be coupled to the rotating shaft 2, and a conductive brush 16 coupled to the base element 12 and meshed with the outer conductor 14, and preferably further comprises at least one centering bearing 18 enabling the centering of the rotating shaft 2 around the fixed shaft 6.

[0017] More particularly, the basic conductive member 12 has a bore 13 dimensioned to receive a portion of the fixed shaft 6 so as to couple the grounding brush assembly 10 to the fixed shaft 6 and a central line Lc extending through the bore 13 and able to be aligned coaxially with the central axis Ac. The outer annular conductor 14 can be meshed with the inner circumferential surface 2a of the rotating shaft 2 so as to couple the conductor 14 to the shaft 2. The conductive brush 16 is coupled to the basic member 12 and has a plurality of conductive fibers 20 extending axially from the radial surface 15 of the basic member 12 and circumferentially around the central line Lc. Each conductive fiber 20 has a first axial end 20a coupled to the basic element 12 and a second opposite axial end 20b engaged with the external conductor 14.

[0018] Thus, at least one conductive path extends from the rotating shaft 2, through the outer conductor 14, the brush 16, and the base element 12, to the stationary shaft 6. Thanks to this grounding brush assembly 10, any electrical charge accumulating on the rotating shaft 2 flows as an electric current through the assembly 10 rather than through the bearing(s) 5 of the electric machine 1. Therefore, damage to the rolling elements and raceways (neither of which is shown) of the bearing(s) 5 is avoided. The basic elements and functions having been described above, these and other components of this grounding brush assembly 10 are described in more detail below.

[0019] Referring now to Figures 4 to 6, the basic member 12 preferably comprises an annular hub 22 and a radial flange 24 extending radially outward from the hub 22. More particularly, the annular hub 22 has an inner circumferential surface 23A providing the bore 13 of the basic member 12, an opposing outer circumferential surface 23B, a first axial end 22a, and a second opposing axial end 20b. The radial flange 24 extends radially outward from the outer circumferential surface 23B of the hub 22 and has an inner radial end 24a formed as one piece with the hub 22, an opposite outer radial end 24b, a first radial surface 25A providing a mounting surface 15 for the conductive brush 16, and a second opposite radial surface 25B. Preferably, the radial rim 24 has at least one and preferably a plurality of retaining tabs 26 spaced circumferentially around the centerline Lc of the base member 12, each tab 26 being engaged with the brush 16 so as to couple or fix the brush 16 to the base member 12, as shown in more detail below.

[0020] Furthermore, each retaining tab 26 is preferably produced or formed by a cut and bent portion of the radial rim 24, which is preferably bent so as to engage with the brush 16 as shown below. Preferably, the conductive base member 12 further comprises an annular cover portion 28 extending axially from the outer radial end 24b of the radial rim 24 so as to surround a portion of the conductive brush 16. Preferably, the base member 12 is formed from an electrically conductive material, such as steel, aluminum, a conductive polymer, or any other suitable conductive material, but alternatively may be formed from a non-conductive material that has been coated or treated with an electrically conductive coating.

[0021] With reference to Figures 3 and 4, the conductive brush 16 preferably comprises an annular retaining element 30 having a circumferential channel 31 ([Fig.4]), each first axial end 20a of the plurality of conductive fibers 20 being disposed inside the circumferential channel 31. More particularly, the retaining element 30 preferably comprises an annular base wall 32 having an inner radial end 32a and an outer radial end 32b, an annular inner side wall 34 extending axially from the inner radial end 32a of the base wall 32 and an annular outer side wall 36 extending axially from the outer radial end 32b of the base wall 32 and spaced radially outwards from the inner side wall 34.Thanks to such a retaining element structure, the retaining tab(s) 26 of the radial rim 24 of the base member 12 are engaged with the outer side wall 36 of the brush retaining element 30 so as to couple the brush 16 to the base member 12.

[0022] Furthermore, the plurality of conductive fibers 20 are arranged between and in contact with the inner and outer side walls 34, 36, respectively, of the retaining element 30 so as to retain the conductive fibers 20 within the annular channel 31. Preferably, the retaining element 30 is formed from an electrically conductive material, such as steel, aluminum, a conductive polymer, etc., and each conductive fiber 20 is a strand of electrically conductive material, preferably of carbon, but can be formed from steel, aluminum, a conductive polymer, etc. However, the conductive brush 14 can alternatively be formed as a single solid annular conductor or a plurality of arcuate conductive segments circumferentially spaced from each other, formed in both cases from a suitable conductive material such as steel, a conductive polymer, etc.

[0023] Referring now to Figures 2, 5 and 6, the outer conductor 14 preferably comprises an axial portion 40 that can mesh with the rotating shaft 2 and a radial flange 42 extending radially inwards from the axial portion 40. More particularly, the axial portion 40 has an outer circumferential surface 41A that can mesh by friction with the inner circumferential surface 2a of the rotating shaft 2, so as to couple the outer conductor 14 to the shaft 2, and an opposing inner circumferential surface 41B. The radial flange 42 has a first radial surface 44A providing a radial contact surface 17 with which the conductive fibers 20 of the conductive brush 16 can mesh and an opposing radial surface 44B.Being able to be connected to the rotating shaft 2, the annular conductor 14 can rotate around the central axis Ac in such a way that the second axial ends 20b of the plurality of conductive fibers 20 slide against the radial surface 17 of the conductor 14.

[0024] Referring to Figures 5 and 6, as mentioned above, the grounding brush assembly 10 preferably comprises at least one centering bearing 18 having an inner ring 50 disposed around the fixed shaft 6 and an outer ring 52 meshing with the inner circumferential surface 2a of the rotating shaft 2. Preferably, each centering bearing 18 comprises a plurality of rolling elements 54 disposed between the inner and outer rings 50, 52, but alternatively may be formed as a plain bearing (not shown). The at least one centering bearing 18 is disposed against, or around, the basic conductive element 12 and the outer conductor 14, and is axially spaced from them, as shown below.In all cases, the centering bearing(s) 18 function to couple the rotating shaft 2 to the fixed shaft 6 in such a way as to stiffen and prevent vibrations of the fixed shaft 6, and do not primarily serve to support any load between the two shafts 2, 6.

[0025] Referring now to Figures 2 to 6, in some constructions, the basic conductive element 12 is generally C-shaped and has a radial flange 24 extending radially outwards from the first axial end 22a of the hub 22, and a cover portion 28 spaced radially outwards from the hub 22, as shown in Figures 2 to 4. In such a construction, the conductive brush 16 is generally clamped between the hub 22 and the cover portion 28. In other constructions, the basic element 12 is generally S-shaped. and is provided with the radial rim 24 extending radially outwards from the second axial end 22b of the hub 22, the hub 22 extending axially from the second radial surface 25B of the rim 24 and the cover portion 28 extending axially from the first radial surface 25A, as shown in Figures 5 and 6.

[0026] Preferably, with a set of grounding brushes 10 having an S-shaped conductive base element 12, either the inner ring 50 of at least one centering bearing 18 is disposed around the outer circumferential surface 23B of the hub 22 so as to couple the bearing 18 to the fixed shaft 6, as shown in [Fig. 5], or a portion of the hub 22 is disposed inside an annular groove 56 extending radially outwards from an inner circumferential surface 51 of the inner ring 50, as shown in [Fig. 6]. However, when the base element 12 is C-shaped as shown in Figures 2 to 4, the inner rings 50 of each of the one or more centering bearings 18 are spaced away from or abut against the base element 12.In addition, the axial part 40 of the outer conductor 14 may be axially spaced from the outer ring 52 of at least one centering bearing 18, as shown in [Fig.6], abut against the outer ring 52 (not shown), or have at least one section 40a arranged around at least a part of the outer ring 52, as illustrated in [Fig.5].

[0027] Representative, but not limiting, examples of the present invention have been described in detail above with reference to the accompanying drawings. This detailed description is intended merely to teach a person skilled in the art further details for implementing preferred aspects of the present teachings and is not intended to limit the scope of the invention.

[0028] Furthermore, combinations of features and steps disclosed in the detailed description above may not be necessary to implement the invention in the broadest sense, and are instead taught simply to describe particularly representative examples of the invention. In addition, various features of the representative examples described above, as well as the various independent and dependent claims below, may be combined in ways not specifically and explicitly listed in order to provide further useful embodiments of the teachings.

[0029] All features disclosed in the description and / or claims are deemed to be disclosed separately and independently of each other for the purposes of original written disclosure, as well as for the purpose of limiting the claimed subject matter, regardless of the compositions of the features in the embodiments and / or claims. Furthermore, all ranges of values ​​or Indications of entity groups are intended to disclose any possible intermediate value or entity for the purposes of original written disclosure, as well as for the purpose of limiting the claimed subject matter. The invention is not limited to the embodiments described above and may be modified within the scope of the following claims.

Claims

Demands

1. Grounding brush assembly for an electrical machine, the electrical machine comprising a rotating shaft capable of rotating about a central axis and having an inner circumferential surface defining a hollow bore, an outer casing, at least one bearing rotatingly coupling the shaft to the casing, and a fixed shaft extending through the bore of the rotating shaft and being electrically grounded, the grounding brush assembly comprising: an inner annular conductor base having a bore dimensioned to receive a portion of the fixed shaft and a central line capable of being aligned coaxially with the central axis; an outer annular conductor capable of meshing with the inner circumferential surface of the rotating shaft;and a conductive brush coupled to the conductive base member and comprising a plurality of conductive fibers extending axially along the central line and circumferentially around it, each conductive fiber having a first axial end coupled to the base member and a second opposite axial end meshed with the outer conductor such that at least one conductive path extends from the rotating shaft, through the outer conductor, the brush and the base member, and to the stationary shaft.

2. Grounding brush assembly according to claim 1, wherein the conductive basic member comprises an annular hub having an inner circumferential surface providing the bore of the basic member and a radial rim extending radially outwards from the hub, the conductive brush being fixed to the radial rim of the basic member.

3. Grounding brush assembly according to claim 2, wherein the outer conductor has an axial portion that can be engaged with the rotating shaft so as to couple the outer conductor to the rotating shaft and a radial rim extending radially inwards from the axial portion, the second axial end of each fiber among the plurality of conductive fibers of the conducting brush being engaged with the radial rim of the outer conductor.

4. Grounding brush assembly according to claim 2, wherein: the conductive brush comprises an annular retaining element having a circumferential channel, the first axial end of each fiber among the plurality of conductive fibers being disposed inside the circumferential channel; and the radial rim of the conductive base member comprises at least one retaining tab engaged with the annular retaining element of the conductive brush to couple the brush to the base member.

5. Grounding brush assembly according to claim 4, wherein the retaining element of the conductive brush comprises an annular base wall having an inner radial end and an outer radial end, an annular inner side wall extending axially from the inner radial end of the base wall and an annular outer side wall extending axially from the outer radial end of the base wall and spaced radially outwards from the inner side wall, the plurality of conductive fibers being arranged between and interlocking with the inner and outer side walls so as to retain the conductive fibers within the annular channel.

6. Grounding brush assembly according to claim 5, wherein at least one retaining tab of the radial rim of the base member comprises a plurality of retaining tabs spaced circumferentially around the centerline of the base member, each retaining tab being engaged with the outer side wall of the retaining element of the conductive brush.

7. Grounding brush assembly according to claim 4, wherein the conductive base member comprises a plurality of retaining tabs spaced circumferentially around the centerline of the base member, each retaining tab being produced by a cut and bent portion of the radial rim.

8. Grounding brush assembly according to claim 2, wherein the radial rim of the conductive base member has an external radial end and the base member further comprises an annular cover portion extending axially from the external radial end of the radial rim.

9. Grounding brush assembly according to claim 1, wherein the outer conductor has an axial portion that can be engaged with the rotating shaft so as to couple the outer conductor to the rotating shaft and a radial rim extending radially inwards from the axial portion, the second axial end of each fiber among the plurality of conductive fibers of the conducting brush being engaged with the radial rim of the outer conductor.

10. Grounding brush assembly according to claim 1, further comprising at least one centering bearing having an inner ring that can be disposed around the fixed shaft and an outer ring that engages with the inner circumferential surface of the rotating shaft, the at least one centering bearing being disposed against the conductive base member or axially spaced from it.

11. Grounding brush assembly according to claim 10, wherein the basic conductive element comprises an annular hub having an inner circumferential surface providing the bore of the basic element and being able to be disposed around the fixed shaft, the inner ring of the centering bearing being disposed around a part of the annular hub so as to couple the centering bearing to the fixed shaft.

12. Grounding brush assembly according to claim 10, wherein the outer conductor has an axial part that can be engaged with the rotating shaft so as to couple the outer conductor to the rotating shaft, at least a section of the axial part being arranged around at least a part of the outer ring of the centering bearing.

13. Grounding brush assembly for an electrical machine, the electrical machine comprising a rotating shaft capable of rotating about a central axis and having an inner circumferential surface defining a hollow bore, an outer casing, at least one bearing rotationally coupling the shaft to the casing, and a fixed shaft extending through the bore of the rotating shaft and electrically grounded, the grounding brush assembly comprising: an annular inner conductive base element having an annular hub, the hub having a bore dimensioned to receive a portion of the fixed shaft and a central line capable be aligned coaxially with the central axis, and a radial rim extending radially outwards from the annular hub; an annular outer conductor having an axial portion capable of engaging with the inner circumferential surface of the rotating shaft so as to couple the outer conductor to the rotating shaft and a radial rim extending radially inwards from the axial portion;and a conductive brush coupled to the conductive base member and comprising a plurality of conductive fibers extending axially along the central line and circumferentially around it, each conductive fiber having a first axial end coupled to the radial edge of the base member and a second opposite axial end engaged with the radial edge of the outer conductor such that at least one conductive path extends from the rotating shaft, through the outer conductor, the brush and the base member, and to the stationary shaft.

14. Grounding brush assembly according to claim 13, wherein: the conductive brush comprises an annular retaining element having a circumferential channel, the first axial end of each fiber among the plurality of conductive fibers being disposed inside the circumferential channel; and the radial rim of the conductive base member comprises at least one retaining tab engaged with the annular retaining element of the conductive brush to couple the brush to the base member.

15. Grounding brush assembly according to claim 14, wherein the retaining element of the conductive brush comprises an annular base wall having an inner radial end and an outer radial end, an annular inner side wall extending axially from the inner radial end of the base wall and an annular outer side wall extending axially from the outer radial end of the base wall and spaced radially outwards from the inner side wall, the plurality of conductive fibers being arranged between and interlocking with the inner and outer side walls so as to retain the conductive fibers within the annular channel.

16. Grounding brush assembly according to claim 15, wherein at least one retaining tab of the radial rim of the base member comprises a plurality of retaining tabs spaced circumferentially around the centerline of the base member, each retaining tab being engaged with the outer side wall of the retaining element of the conductive brush.

17. Grounding brush assembly according to claim 14, wherein at least one retaining tab of the conductive base member comprises a plurality of retaining tabs spaced circumferentially around the centerline of the base member, each retaining tab being produced by a cut and bent portion of the radial rim.

18. Grounding brush assembly according to claim 13, wherein the radial rim of the conductive base member has an external radial end and the base member further comprises a cover portion extending axially from the external radial end of the radial rim.

19. Grounding brush assembly according to claim 13, further comprising at least one centering bearing having an inner ring that can be disposed around the fixed shaft and an outer ring that engages with the inner circumferential surface of the rotating shaft, the at least one centering bearing being disposed against the conductive base member or axially spaced from it.

20. Grounding brush assembly according to claim 19, wherein: the inner ring of the centering bearing is arranged around a portion of the annular hub so as to couple the centering bearing to the fixed shaft; and / or at least a section of the axial portion of the outer conductor is arranged around at least a portion of the outer ring of the centering bearing.

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