Assembly of internally bypassed grounding brushes comprising axial brushes and centering bearings

Abstract

An internally bypassed grounding brush assembly comprising axial brushes and centering bearings. A grounding brush assembly is intended for an electrical machine comprising a rotating shaft having a bore, an outer housing, one or more bearings rotating the shaft to the housing, and a stationary, electrically grounded shaft extending through the bore of the rotating shaft. A conductive base receives the stationary shaft and has a main body portion and at least one end body portion having an outside diameter smaller than the outside diameter of the main body portion. A centering bearing is disposed around the end body portion. A conductive brush coupled to the main body portion has conductive fibers extending radially outward from the main body portion and axially along a centerline.Each conductive fiber has an inner radial end coupled to the base element and an outer radial end that can be meshed with the inner circumferential surface of the rotating shaft such that at least one conductive path extends from the rotating shaft to the stationary shaft. Reference: Figure 1.

Description

Title of the invention: Assembly of internally bypassed grounding brushes comprising axial brushes and centering bearings. Cross reference

[0001] This application claims priority from Italian patent application number 102024000016090 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 rotating about a central axis and having an inner circumferential surface defining a hollow bore, an outer housing, at least one bearing rotating 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 a conductive basic element having a cylindrical body with a bore dimensioned to receive a portion of the fixed shaft and a central line that can be aligned coaxially with the central axis, the cylindrical body having a main body portion with an outer circumferential surface and a first outer diameter and at least an end body portion with a second outer diameter, the second outer diameter having a value smaller than a value of the first outer diameter.At least one centering bearing comprises an inner ring disposed around at least one end body portion of the cylindrical body of the base member and an outer ring capable of engaging with the inner circumferential surface of the rotating shaft so as to center the rotating shaft around the fixed shaft.At least one conductive brush is coupled to the conductive base member and comprises a plurality of conductive fibers extending radially outwards from the outer surface of the main body part of the base member and axially along the centerline, each conductive fiber having an inner radial end coupled to the base member and an outer radial end capable of meshing with the inner circumferential surface of the rotating shaft such that at least one conductive path extends from the rotating shaft, through the brush and the base member, and to the stationary shaft.

[0006] Preferably, the main body portion of the cylindrical body has a first axial end and a second opposing axial end, and at least one end body portion of the cylindrical body comprises a first end body portion extending axially from the first axial end of the main body portion and a second end body portion extending axially from the second axial end of the main body portion. Thanks to this structure, at least one centering bearing comprises a first centering bearing disposed around the first end body portion of the cylindrical body of the base element and a second centering bearing disposed around the second end body portion of the cylindrical body of the base element.

[0007] Furthermore, the main body part of the cylindrical body of the basic member preferably has at least one axial groove extending radially inward from the outer circumferential surface of the main body part and axially between the first and second axial ends of the main body part, the inner end of each fiber among the plurality of fibers conductive fibers being arranged within at least one axial groove, and the plurality of conductive fibers being axially spaced along at least one axial groove. Preferably, the at least one conductive brush comprises a plurality of conductive brushes, each brush among the plurality of brushes being arranged within a distinct groove among a plurality of axial grooves in the main body portion of the cylindrical body. 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 an assembly of grounding brushes comprising a basic element having two end body parts and two centering bearings;

[0011] [Fig. 3] is an axial cross-sectional view of an assembly of grounding brushes comprising a basic element having a single end body portion and a centering bearing; and

[0012] [Fig.4] is a perspective view of a basic organ comprising a single end body part. Detailed description of the invention

[0013] 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 meaning 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.

[0014] If we now refer to the detailed drawings, where similar numbers are used to indicate similar elements throughout, it is shown in the figures 1 to 4, a set of grounding brushes 10 for an electrical machine 1. The electrical machine 1 comprises a shaft 2 that can rotate about a central axis Ac and has an inner circumferential surface 2a defining a hollow bore 3, an outer casing 4, at least one bearing 5 rotationally coupling the shaft 2 to the casing 4, and a fixed shaft 6 that extends through the bore 3 of the rotating shaft 2 and is electrically grounded. The set of grounding brushes 10 essentially comprises a conductive base element 12, at least one conductive brush 14 coupled to the base element 12 and having a plurality of conductive fibers 40, and at least one centering bearing 18 disposed around an end portion 28 of the base element 12.

[0015] More particularly, the basic element 12 comprises a cylindrical body 22 having an inner circumferential surface 24 defining a bore 25 dimensioned to receive a portion of the fixed shaft 6 and a central line Lc that can be aligned coaxially with the central axis Ac. Preferably, the grounding brush assembly 10 is mounted on the fixed shaft 6 by a friction fit between the inner surface 24 of the cylindrical body 22 and the outer circumferential surface (not shown) of the shaft 6. In addition, the cylindrical body 22 comprises a main body portion 26 having an outer circumferential surface 27 and a first outer diameter DI and at least one end body portion 28 having a second outer diameter D2, the second outer diameter D2 having a value less than a value of the first outer diameter D1, as shown in [Fig.2].Thus, at least one end body part 28 is stepped inwards relative to the main body part 26. In addition, the cylindrical body 22 is formed from an electrically conductive material, such as steel, aluminum, a conductive polymer or any other suitable conductive material.

[0016] The at least one centering bearing 18 comprises an inner ring 30 disposed around at least one end body portion 28 of the cylindrical body 22 of the base member 12 and an outer ring 32 capable of meshing with the inner circumferential surface 2a of the rotating shaft 2, and preferably comprises a plurality of rolling elements 34 disposed between the inner and outer rings 30, 32. The at least one centering bearing 18 functions so as to couple the rotating shaft 2 to the fixed shaft 6, such that the centering bearing(s) 18 stiffen and prevent vibrations of the fixed shaft 6, and are not intended to support a load between the two shafts 2, 6.

[0017] Furthermore, the at least one conductive brush 14 comprises a plurality of conductive fibers 40 extending radially outwards from the outer surface 27 of the main body part 26 of the basic member 12 and axially along of the central line Lc, and can alternatively extend both axially along the central line Lc and circumferentially around it. Each conductive fiber 40 has an inner radial end 40a coupled to the main body part 26 of the basic member 12 and an outer radial end 40b that can mesh with the inner circumferential surface 2a of the rotating shaft 2.

[0018] Thus, at least one electrically conductive path extends from the rotating shaft 2, through the brush 14 and the base member 12, to the stationary shaft 6. Thanks to this grounding brush assembly 10, any charge accumulating on the rotating shaft 2 flows as a current through the assembly 10 rather than through the bearing(s) 5 of the electric machine 1. Consequently, damage to the rolling elements and raceways (neither being specified) of the bearing(s) 5 is avoided, while the centering bearing(s) 18 stiffen and prevent vibrations of the stationary shaft 6. 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 to Figures 2 to 4, the main body part 26 has a first axial end 26a and a second opposing axial end 26b and preferably includes at least one axial groove 50 extending radially inwards from the outer surface 27 of the main body part 26. The at least one groove 50 extends axially between the first and second axial ends 26a, 26b of the main body part 26. In addition, the inner end 40a of each conductive fiber among the plurality of conductive fibers 40 is disposed inside the at least one axial groove 50 and the plurality of conductive fibers 40 are spaced along the at least one axial groove 40.Preferably, at least one axial groove 50 comprises a plurality of axial grooves 50, each extending axially between the first and second ends 26a, 26b of the main body part 26 and circumferentially spaced from each other around the central line Lc. Alternatively, the main body part 26 may comprise only a single spiral groove (not shown) formed in the outer surface 27 of the main body part 26 and extending axially between the first and second axial ends 26a, 26b and circumferentially around the central line Lc.

[0020] As illustrated in [Fig. 2], the cylindrical body 22 preferably comprises two end body parts 28, specifically a first end body part 29A extending axially from the first axial end 26a of the main body part 26a and a second end body part 29B extending axially from the second axial end 26b of the main body part 26. Thanks to this body structure, at least one centering bearing 18 comprises a first centering bearing 19A arranged around the first end body part 29A of the cylindrical body 22 and a second centering bearing 19B arranged around the second end body part 19A of the cylindrical body 22.

[0021] With particular reference to [Fig. 4], at least one conductive brush 14 preferably comprises a plurality of conductive brushes 14, each brush among the plurality of brushes 14 being arranged inside a distinct axial groove among the axial grooves 50 of the main body portion 26 of the cylindrical body 22. Each brush 14 preferably comprises a retaining element 60 having a base wall 62 and two lateral walls 64, 66 spaced apart, extending from the base wall 62 so as to define an axial channel 61. The plurality of conductive fibers 40 of each brush 14 are arranged between the two lateral walls 64, 66, and meshed with them, so as to retain the conductive fibers 40 inside the axial channel 41. Preferably, the retaining element 40 is formed at starting from an electrically conductive material, such as steel, aluminum, a conductive polymer, etc., and each 40 conductive fiber is a strand of an electrically conductive material, preferably carbon, but can be formed from steel, aluminum, a conductive polymer, etc.

[0022] In the preferred cylindrical body 22 having two end body portions 29A, 29B and two centering bearings 19A, 19B, each brush 14 is retained inside the associated axial groove 50 of the main body portion 26 by the two bearings 19A, 19B. However, as illustrated in [Fig. 3], the cylindrical body 22 may be provided with only one end body portion 28 extending from the first axial end 26a of the main body portion 26, in which case the basic conducting member 12 further comprises an annular retaining clip 70 engaged with the second axial end 26b of the main body portion 26. The retaining clip 70 is configured to retain each brush 14 arranged inside the associated axial groove 50 of the main body portion 26 of the cylindrical body 22.Preferably, the cylindrical body 22 has an annular groove 72 situated adjacent to the second axial end 26b of the main body part 26 and the retaining clip 70 is a C-clip disposed inside the annular groove 72 and positioned against an axial end (not shown) of each brush 14.

[0023] Thanks to the grounding brush assembly 10 of the present invention, the conductive fibers 40 are in contact with the inner surface 2a of the rotating shaft 2, which has a linear velocity (i.e., tangent to the surface 2a) with a magnitude that is less than the magnitude of the linear velocity at the outer surface 2b of the shaft 2. Thus, both the friction and the wear of the conductive fibers 40 are reduced. by comparison with known assemblies of grounding brushes having conductive fibers in contact with an outer surface of a rotating shaft.

[0024] 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.

[0025] 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.

[0026] All features disclosed in the description and / or claims are intended to be disclosed separately and independently of one another 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 intermediate 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

1.

2. Demands A set of grounding brushes 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 electrically grounded, the set of grounding brushes comprising: a conductive basic element having a cylindrical body with a bore dimensioned to receive a portion of the fixed shaft and a central line capable of being aligned coaxially with the central axis, the cylindrical body having a main body portion having an outer circumferential surface and a first outer diameter and at least an end body portion having a second outer diameter,the second outer diameter having a value less than a value of the first outer diameter; at least one centering bearing comprising an inner ring disposed around at least one end portion of the cylindrical body of the base component and an outer ring capable of engaging with the inner circumferential surface of the rotating shaft so as to center the rotating shaft around the fixed shaft; and at least one conductive brush coupled to the conductive base member and comprising a plurality of conductive fibers extending radially outward from the outer surface of the main body portion of the base member and axially along the centerline, each conductive fiber having an inner radial end coupled to the base member and an outer radial end capable of meshing with the inner circumferential surface of the rotating shaft such that at least one conductive path extends from the rotating shaft, through the brush and the base member, and to the stationary shaft. Grounding brush assembly according to claim 1, wherein: The main body part of the cylindrical body has a first axial end and a second opposite axial end and at least one end body part of the cylindrical body comprises a first end body part extending axially from the first axial end of the main body part and a second end body part extending axially from the second axial end of the main body part; and at least one centering bearing comprises a first centering bearing disposed around the first end body part of the cylindrical body of the base member and a second centering bearing disposed around the second end body part of the cylindrical body of the base member.

3. Grounding brush assembly according to claim 1, wherein the main body part of the cylindrical body of the base member has at least one axial groove extending radially inwards from the outer circumferential surface of the main body part and axially between the first and second axial ends of the main body part, the inner end of each fiber among the plurality of conductive fibers being disposed inside at least one axial groove and the plurality of conductive fibers being axially spaced along at least one axial groove.

4. Grounding brush assembly according to claim 3, wherein: at least one axial groove of the main body part of the cylindrical body comprises a plurality of axial grooves each extending axially between the first and second ends of the main body part and circumferentially spaced from each other around the centerline of the base member; and at least one conductive brush comprises a plurality of conductive brushes, each brush among the plurality of brushes being disposed within a separate groove among the axial grooves of the main body part of the cylindrical body.

5. An assembly of grounding brushes according to claim 3, wherein at least one conductive brush comprises a retaining element having a base wall and two lateral walls spaced apart, extending from the base wall so as to define an axial channel, the plurality of conductive fibers being arranged between the two lateral walls, and in contact with them, so as to retain the conducting fibers inside the axial canal.

6. Grounding brush assembly according to claim 3, wherein: the main body part of the cylindrical body of the conductive base member has a first axial end and a second opposite axial end, at least one end body part extending axially from the first axial end; and the conductive base member further comprises a retaining clip engaged with the second axial end of the main body part and configured to retain at least one conductive brush disposed within the axial groove of the main body part of the cylindrical body.

7. Grounding brush assembly according to claim 6, wherein the cylindrical body has an annular groove situated adjacent to the second axial end of the main body part and the retaining clip is a C-clip disposed inside the annular groove and can be disposed against an axial end of at least one conductive brush.

8. 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 being electrically grounded, the grounding brush assembly comprising: a conductive basic element having a cylindrical body 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, the cylindrical body having a main body portion having an outer circumferential surface and a first outer diameter and at least an end body portion having a second outer diameter,the second outer diameter having a value less than a value of the first outer diameter; at least one centering bearing comprising an inner ring disposed around at least one end body portion of the cylindrical body of the base element and an outer ring, that can be engaged with the inner circumferential surface of the rotating shaft so as to center the rotating shaft around the fixed shaft; and a plurality of conductive brushes each coupled to the main body part of the conductive base member and circumferentially spaced from each other around the centerline, each conductive brush among the plurality of conductive brushes having a plurality of conductive fibers extending radially outwards from the outer surface of the main body part of the base member and axially along the centerline, each conductive fiber having an inner radial end coupled to the cylindrical body of the base member and an outer radial end able to mesh with the inner circumferential surface of the rotating shaft such that at least one conductive path extends from the rotating shaft, through each brush among the plurality of brushes and the base member, and to the stationary shaft.

9. A set of grounding brushes according to claim 8, wherein: The main body portion of the cylindrical body has a first axial end and a second opposing axial end, and at least one end body portion of the cylindrical body comprises a first end body portion extending axially from the first axial end of the main body portion and a second end body portion extending axially from the second axial end of the main body portion; and at least one centering bearing comprises a first centering bearing disposed around the first end body part of the cylindrical body of the base element and a second centering bearing disposed around the second end body part of the cylindrical body of the base element.

10. A grounding brush assembly according to claim 8, wherein the main body portion of the cylindrical body of the basic member has a plurality of axial grooves spaced circumferentially around the centerline, each axial groove extending radially inward from the outer circumferential surface of the main body portion and axially between the first and second axial extremities of the main body part, the inner radial extremities of the plurality of conductive fibers of each brush among the plurality of brushes being arranged inside a distinct axial groove among the axial grooves and axially spaced along it.

11. A set of grounding brushes according to claim 8, wherein each conductive brush among the plurality of conductive brushes comprises a retaining element having a base wall and two side walls spaced apart, extending from the base wall so as to define an axial channel, the plurality of conductive fibers being arranged between the two side walls, and in contact with them, so as to retain the conductive fibers inside the axial channel.

12. Grounding brush assembly according to claim 8, wherein: the main body part of the cylindrical body of the conductive base member has a first axial end and a second opposite axial end, at least one end body part extending axially from the first axial end; and the conductive base member further comprises a retaining clip engaged with the second axial end of the main body part and configured to retain at least one conductive brush disposed within the axial groove of the main body part of the cylindrical body.

13. Grounding brush assembly according to claim 12, wherein the cylindrical body has an annular groove situated adjacent to the second axial end of the main body part and the retaining clip is a C-clip disposed inside the annular groove and can be disposed against an axial end of at least one conductive brush.

Images