Combined insulator and conductor assembly for bearings with fixed conductors - Patent Application 20070122997

Abstract

To provide a composite type insulator and a conductor assembly for a bearing, which have a fixed conductor.SOLUTION: A composite type electric insulator and a conductor assembly include an annular insulator that can be disposed around a bearing outside ring and is configured to prevent a current flow between an outside ring and a housing, the annular insulator including projecting portions extending in axial direction along a center line and disposed around the center axis at intervals in a circumferential direction. A conductor includes a conductive disc that has an outside diametrical direction end portion that can be engaged with a housing inside surface, an inside diametrical direction end portion defining a center opening portion for receiving a shaft, and an opening portion receiving each of the plurality of projecting portions of the insulator. The disc is fixed in an axial direction with respect to the insulator. An annular conductive brush sub assembly includes a plurality of electric conductive fibers that are united with the conductive disc, and can contact with a shaft outside surface so as to provide a conductive path between the shaft and the disc.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to bearings, and more particularly to a grounding device for preventing current or charge from passing through the bearing. [Background technology]

[0002] Bearings used in electric machines such as motors, generators, and similar devices can be damaged if an electric current or charge is passed through the bearing, which can have a particularly adverse effect on the bearing raceways. Devices such as grounding brushes have been developed to provide an alternate path for the electric current, thereby preventing such current from passing through the bearing. Summary of the Invention [Problem to be solved by the invention]

[0003] These devices often include a plurality of conductive fibers spaced circumferentially around the entire outer surface of the shaft, forming a relatively solid ring of fibers, such that electrical current passes through the conductive fibers between the shaft and the housing. Other devices or mechanisms are provided to electrically insulate the bearing to prevent electrical current from passing through the bearing, and may include an insulating coating or cover. [Means for solving the problem]

[0004] In one aspect, the present invention is a combined electrical insulator and conductor assembly for a bearing positionable between a shaft and a housing, the bearing having an inner ring, an outer ring having an outer circumferential surface and opposite first and second axial ends, a plurality of rolling elements between the rings, and the housing having an inner circumferential surface. The assembly includes an annular insulator positionable around the outer ring and configured to prevent the flow of electrical current between the outer ring and the housing. An electrical conductor is fixedly coupled to the insulator and has inner and outer radial ends, the conductor outer radial end and / or a portion of the conductor between the inner and outer ends being conductively engageable with the housing, and the conductor inner radial end is engageable with the shaft outer surface to provide an electrically conductive path between the shaft and the housing.

[0005] Preferably, the insulator has a centerline and a plurality of protrusions extending axially along and circumferentially spaced about the centerline. The conductor preferably includes an electrically conductive disk having a plurality of openings each receiving a separate one of the insulator's protrusions to fixedly couple the disk to the insulator. The disk has an outer radial end engageable with the housing inner surface and an inner radial end defining a central opening for receiving a portion of the shaft. Furthermore, the conductor also preferably includes an annular conductive brush subassembly coupled to the conductive disk and having a centerline and a plurality of electrically conductive fibers. The conductive fibers are circumferentially spaced about the centerline and extend radially inward from the inner end of the conductive disk, each having an inner end capable of contacting the outer shaft surface to provide a conductive path between the shaft and the disk.

[0006] The foregoing summary, as well as detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, there are shown in the drawings diagrammatical embodiments which are presently preferred. It being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view of a combined insulator and conductor assembly according to the present invention shown mounted in a bearing. [Figure 2] FIG. 1 is a plan view of a combined insulator and conductor assembly. [Figure 3] FIG. 1 is an axial cross-sectional view of a combined insulator and conductor assembly shown mounted on a shaft and within a housing. [Figure 4] FIG. 2 is an axial cross-sectional view of a combined insulator and conductor assembly. [Figure 5] FIG. 5 is an isolated enlarged view of the top of FIG. [Figure 6] FIG. 6 is a further enlarged view of a portion of FIG. 5. [Figure 7] FIG. 2 is a plan view of a conductive disk and conductive brush subassembly. [Figure 8] This is a view passing through line 8-8 in Figure 7. [Figure 9] This is a view passing through line 9-9 in Figure 7. [Figure 10A] 1 is an isolated axial cross-sectional view of the components of the insulator during assembly. FIG. [Figure 10B] 10A and 10B are isolated axial cross-sectional views of the components of the insulator during assembly, collectively referred to as FIG. 10. [Figure 11A] 10A-10C are separated axial cross-sectional views of the insulator and the conductor during the stage of assembling the conductor onto the insulator. [Figure 11B] 10A-10C are separated axial cross-sectional views of the insulator and the conductor during the stage of assembling the conductor onto the insulator. [Figure 11C] 11A and 11B are axial cross-sectional views of an isolated insulator and a conductor during the stage of assembling the conductor onto the insulator, collectively referred to as FIG. 11. [Figure 12] FIG. 1 is a perspective view of the insulator mounted without the conductor conductive disk and brush subassembly. [Figure 13]FIG. 1 is a perspective view of an attached insulator with a conductor attached. [Figure 14] FIG. 10 is an enlarged, isolated, axial cross-sectional view of the combined insulator and conductor assembly shown mounted on the shaft and within the housing and engaged by the mechanical components. DETAILED DESCRIPTION OF THE INVENTION

[0008] Certain terms are used in the following description for convenience only and are not limiting. The terms "inner," "inwardly," and "outer," "outwardly" refer to directions toward and away from a depicted centerline or the geometric center of the described element, respectively, with the specific meanings being readily apparent from the context of the description. Furthermore, as used herein, the terms "connected" and "coupled" are intended to include, respectively, a direct connection between two elements without any other intervening elements, and an indirect connection between elements via one or more other intervening elements. The term specifically includes the terms mentioned above, their derivatives, and terms with similar meanings.

[0009] Referring now in detail to the drawings, wherein like numerals are used to refer to like elements throughout, a central axis A C A combined electrical insulator and conductor assembly 10 for a bearing 1 positionable between a shaft 2 rotatable about and a housing 3 is shown in Figures 1-14. Bearing 1 has an inner ring 4, an outer ring 5 having opposed first and second axial ends 5a, 5b and an outer surface 5c, and a plurality of rolling elements 6 disposed between the inner ring 4 and the outer ring 5. Shaft 2 has an outer circumferential surface 2a, and housing 3 has an inner circumferential surface 3a defining a bore 7. Preferably, bearing 1, shaft 2, and housing 3 are components of a motor or other electric machine (e.g., a generator) or any other machine having rotating components suitable for storing charge or transmitting current.

[0010] The combined insulator and conductor assembly 10 basically comprises an annular insulator 12 positionable around the bearing outer ring 5 and configured to prevent the flow of electrical current between the bearing outer ring 5 and the housing 3, and thus through the bearing 1, and an electrical conductor 11 fixedly coupled to the insulator 12 and having an inner radial end 11 a and an outer radial end 11 b. Either the conductor outer radial end 11 b and / or a portion of the conductor 11 between the inner and outer ends 11 a, 11 b is conductively engageable with the housing 3, and the conductor inner radial end 11 a is engageable with the shaft outer surface 2 a to provide a conductive path between the shaft 2 and the housing 3. As used herein, the term “conductively engageable” means establishing an electrical conductive path, either through direct contact or contact with one or more intermediate components or members 7 ( FIG. 14 ), to allow electrical current to flow between the engaged members, particularly between the conductor 11 and the housing 3. Preferably, the conductor 11 includes an electrically conductive disk 14 fixedly coupled to the insulator 12 so as to be axially adjacent to the bearing 1, and a brush subassembly 16 coupled to the disk 14 and having a plurality of conductive fibers 18 contactable with the shaft 2, the disk 14 and the brush subassembly 16 forming the conductor 11, as described in detail below.

[0011] More specifically, insulator 12 is configured to prevent the flow of electrical current between bearing outer ring 5 and housing 3, and thus through bearing 1, and has a centerline 13 and a plurality of protrusions 20 extending axially along and spaced circumferentially about centerline 13. Conductive disk 14 has a centerline 15, an outer radial end 14a engageable with housing inner surface 3a and providing a conductor outer radial end 11b, and an inner radial end 14b defining a central opening 17 for receiving a portion of shaft 2. Furthermore, conductive brush subassembly 16 has a centerline 16a, and conductive fibers 18 are spaced circumferentially about centerline 16a and extend radially inward from inner end 14b of conductive disk 14.

[0012] Each conductive fiber 18 is preferably formed of carbon and has an inner end 18a contactable with the shaft outer surface 2a to provide a conductive path between the shaft 2 and the disc 14, which fiber inner ends 18a collectively provide the inner end 11a of the conductor 11. Because the disc 14 is configured to provide a conductive path between the brush subassembly 16 and the housing 3, any current or charge on the shaft 2 is directed to flow through the assembly 10 rather than through the bearing 1. Thus, the combined insulator and conductor assembly 10 functions to protect the bearing 1 by preventing direct current flow through the bearing 1 (i.e., by the insulator 12) and by providing an alternate path for current adjacent the bearing 1 using the brush subassembly 16 and the conductive disc 14 of the conductor 11. Having described their basic structure and function above, these and other components of the assembly are described in detail below.

[0013] 4-6 and 10-12, the insulator 12 preferably includes an insulating ring 30 coupled to the first axial end 5a of the bearing outer ring 5 and providing the axial protrusion 20, and a tubular insulator body 32 disposed around the outer ring 5 and coupled to the insulating ring 30. The insulating ring 30 is formed of an insulating material, preferably glass-filled nylon, most preferably 35% glass-fiber reinforced polyamide 66, but may be formed of any other suitable material. Preferably, the insulating ring 30 is generally circular and has an axial portion 34 disposed around a portion of the outer surface 5c of the bearing outer ring 5, and a radial portion 36 extending inwardly from the axial portion 34.

[0014] More specifically, ring axial portion 34 has an inner circumferential surface 35A disposed about a portion of ring outer surface 5c, an opposing outer circumferential surface 35B, and an annular groove 37. Annular groove 37 extends radially inward from outer surface 35B and circumferentially about insulator centerline 13 and is configured to receive an annular shoulder 40 of tubular body 32, as described below. Preferably, ring axial portion 34 further has an angled lead-in edge 34a to facilitate coupling with tubular body 32, as described below.

[0015] Furthermore, the radial portion 36 of the ring 30 has a first axial end 36a that abuts the first axial end 5a of the bearing outer ring 5 and an opposite second axial end 36b, with a plurality of protrusions 20 extending axially from the second axial end 36b. Preferably, each protrusion 20 is formed as a generally circular cylindrical rod 38 having an inner end 38a that is integrally formed with the ring radial portion 36 and an opposite free outer end 38b that has a head 39 that is circularly shaped similar to a rivet. The protrusion heads 39 collectively securely hold the conductive disk 14 on the protrusion 20, and each head 39 is formed after the disk 14 has been assembled onto the protrusion 20, as described below.

[0016] 4-6 and 10-12, the tubular insulator body 32 is generally cylindrical and has opposite inner and outer circumferential surfaces 33A, 33B and opposite axial ends 32a, 32b. The insulator body 32 is preferably formed of aluminum and has at least one oxide layer formed on one or both of the circumferential surfaces 33A, 33B, preferably formed by anodizing. However, the body 32 may alternatively be formed of other suitable insulating materials (e.g., hard polymers or ceramics) or other anodized metallic materials. The inner circumferential surface 33A of the body 32 is positionable around the outer surface 5c of the bearing outer ring 5, and the outer circumferential surface 33B is engageable with the housing inner surface 3a to axially retain the bearing 5. Additionally, the tubular insulator body 32 preferably has an annular shoulder 40 extending radially inward from the inner surface 33A adjacent the first axial end 32a, and an angled engagement surface 42 adjacent the shoulder 40. Preferably, a flange 44 extends radially inward from the second axial end 32b of the insulator body 32 and is positionable against the second axial end 5b of the bearing 5 to insulate the bearing axial end 5b.

[0017] 5 and 10, in the above construction, the preferred two-piece insulator 12 is mounted around the bearing outer ring 5 in the following manner. The insulator body 32 is mounted around the bearing outer ring 5 by first inserting the bearing second axial end 5b into the first axial end 32a of the tubular body 32 and then sliding the body inner surface 33A around the ring outer surface 5c until the flange 44 abuts the ring second end 5b. Next, as shown in FIG. 10, the insulator ring 30 is mounted onto the bearing outer ring 5 by inserting the bearing first axial end 5a into the free end 34a of the ring axial portion 34. The axial portion 34 is displaced toward the tubular body 32, and the angled lead-in surface 34b of the ring 30 bends the first axial end 32a of the tubular body 32 radially outward until the shoulder 40 rests within the recess 37 of the ring 30. 10B, the angled lead-in surface 34b is positioned against the angled engagement surface 42 of the insulator body 32, and the first axial end 36a of the ring radial portion 36 is positioned against the first axial end 5a of the bearing outer ring 5. The insulator ring 30 is then preferably molded (e.g., by heating) to the bearing outer ring 5 to securely hold the insulator 12 around the bearing 1.

[0018] 5-9, the conductive disk 14 is generally circular and preferably formed of a conductive metallic material, most preferably aluminum, although it may be formed of any other suitable material (e.g., low-carbon steel). The disk 14 also has first and second opposed axial ends 14c, 14d and a plurality of openings 22 extending between the axial ends 14c, 14d and circumferentially spaced about the centerline 15. Each disk opening 22 receives a respective one of the plurality of protrusions 20 of the insulator 12 to fixedly couple the disk 14 thereto, and the disk centerline 15 is generally coaxial with the insulator centerline 13, as described below. Additionally, the conductive disk 14 preferably also has a plurality of arcuate flanges 50, each positioned adjacent a respective opening 22 and extending axially from the outer radial end 14a of the disk 14. Each flange 50 is conductively engagable with the housing inner surface 3 a, thereby increasing the surface area of the disk 14 in conductive contact with the housing 3 .

[0019] Additionally, disc 14 also preferably includes a plurality of mounting tabs 52 spaced circumferentially about centerline 15, each of which engages with brush subassembly 16 to couple brush subassembly 16 to disc 14. Preferably, each mounting tab 52 is formed by cutting (e.g., stamping) disc 14 to form a rectangular tab 52 and a clearance hole 56. Each tab 52 is bent around a retainer 60 (described below) of brush subassembly 16, with each engaged mounting tab 52 being generally C-shaped and fixedly attaching brush subassembly 16 to disc 14. Clearance holes 56 also provide a passageway for fluid (e.g., lubricant, air, etc.) to flow through conductive disc 14 to conduct into and out of bearing 1.

[0020] 11-13, the conductive disk 14 is coupled to the insulator 12 by axially displacing the disk 14 toward the insulator 12 mounted on the bearing 1 until the free ends 38b of each projection rod 38 enter respective ones of the openings 22 from the disk second axial end 14d, as shown in FIG. 11A. Next, the projections 20 pass through the disk openings 22 until the outer portions of the projections 20 extend outward from the disk first axial end 14c, as shown in FIGS. 11B and 12. Finally, as shown in FIGS. 11C and 13, the free ends 38b of the projection rods 38 are formed or deformed into heads 39, preferably using an ultrasonic process, which are placed against the disk first axial end 14c to securely hold the disk 14 on the projections 22, thereby permanently coupling the disk 14 to the insulator 12.

[0021] 2, 5, 8, and 9, the conductive brush subassembly 16 preferably includes an annular retainer 60 connected to the conductive disk 14 as described above and having an open inner axial end 60a and a closed outer end 60b with an annular groove 62 therein. Each one of the plurality of conductive fibers 18 has an outer radial end 18b disposed in the groove 62 and extends radially inward from the retainer 60 toward the shaft 2. More specifically, the retainer 60 has an outer axial base 64 and two opposing radial legs 66, with the retainer 60 having a generally C-shaped axial cross-section. The retainer legs 66 preferably abut and clamp the outer ends 18b of the conductive fibers 18 to retain the fibers 18 within the groove 62.

[0022] Additionally, the brush subassembly 16 preferably includes a circular hoop 68 disposed within the retainer groove 62, with each one of the plurality of conductive fibers 18 bent around the hoop 68. As such, each conductive fiber 18 is preferably generally U- or V-shaped and has two inner ends 18a that can contact the shaft outer surface 2a. However, each one of the conductive fibers 18 may be arranged to extend from an outer radial end 18b to an inner radial end 18a as a generally straight strand (not shown).

[0023] Furthermore, the plurality of conductive fibers 18 of the brush subassembly 16 are generally arranged either in a continuous ring of fibers (not shown) or, preferably, as a plurality of circumferentially spaced sets 19 of individual fibers 18. In the latter preferred case, the sets 19 of fibers 18 are preferably formed by stamping the brush subassembly 16, which includes a continuous ring of fibers 18, with the sets 19 of fibers 18 that are contactable with the shaft 2 being spaced apart by sets 21 of shorter lengths of fibers 18. Furthermore, each conductive fiber 18 is preferably sized to have a diameter within the range of five micrometers or microns (5 μm) to one hundred microns (100 μm). Each conductive fiber 18 is preferably formed of carbon, as described above, although the fibers 18 may alternatively be made of any suitable electrically conductive material, such as a metallic material, a conductive polymer, or the like.

[0024] Although conductor 11 preferably includes conductive disk 14 and brush subassembly 16 as described above and illustrated in the drawings, conductor 11 may alternatively be formed in any other suitable manner capable of being fixedly coupled to insulator 12 and providing one or more conductive paths between shaft 2 and housing 3. For example, instead of brush subassembly 16, conductor 11 may include a solid ring (not shown) of conductive material attached to conductive disk 14 and conductively engageable with shaft 2, the ring having either a continuous inner circumferential contact surface or multiple arcuate contact surface sections provided by radially inwardly extending protrusions. As a further alternative, conductive disk 14 may be formed with an inner end 14b capable of contacting shaft outer surface 2a to provide a direct conductive path between shaft 2 and disk 14. The scope of the present invention encompasses these and all other suitable configurations of conductor 11 capable of generally functioning as described herein.

[0025] The insulator / conductor assembly 10 of the present invention is more effective than known devices in protecting the bearing 1 from damage caused by electrical current. The insulator 12 effectively prevents a potential difference from being established between the shaft 2 and the housing 3 through the bearing 1, preventing electrical current from flowing through the inner and outer rings 4, 5 and the rolling elements 6. To further ensure that electrical current does not pass through the bearing 1, the conductive disk 14 and brush subassembly 16 provide an alternate path for any electrical charge or current on the shaft 2 to pass through the conductive fibers 18 to the retainer 60, through the retainer 60 into the conductive disk 14, and then through the disk outer flange 50 into the housing 3. An additional or alternate electrical conduction path to the housing 3 may be provided by axial contact between a portion of the housing 3 (e.g., a radial shoulder) or a mechanical component 7 disposed within the housing 3, such as a spring or pin, and either the surface of the conductive disk 14 or / and the surface of the annular retainer 60, as shown in FIG. 13 . Thus, any charge or current on shaft 2 in the area of bearing 1 is prevented from passing through bearing 1 by insulator 12 and is diverted to pass through brush subassembly 16 and conductive disc 14 of conductor 11. Furthermore, assembly 10 may be mounted to bearing 1 by a manufacturer or distributor, and bearing 1, along with combined insulator and conductor assembly 10, may be provided to a customer or end user as a whole assembly ready to be mounted on shaft 2 and within housing 3.

[0026] It will be appreciated by those skilled in the art that changes could be made to the above-described embodiments without departing from the broad inventive concept thereof. It is understood, therefore, that the invention is not limited to the particular embodiments disclosed, but that it is intended to cover modifications within the spirit and scope of the invention as generally defined in the appended claims. [Explanation of symbols]

[0027] 1...bearing, 2...shaft, 2a...shaft outer surface, 3...housing, 3a...inner circumferential surface, 4...inner ring, 5...outer ring, 5a...first axial end, 5b...second axial end, 5c...outer circumferential surface, 6...rolling element, 10...combined electrical insulator and conductor assembly, 11...electrical conductor, 11a...inner radial end, 11b...outer radial end, 12...annular insulator, 13...centerline, 14...electrically conductive disk, 14a...outer end, 14b...inner radial end, 15...centerline, 16...annular conductive brush subassembly, 16a...centerline, 1 7...central opening, 18...electrically conductive fibers, 18a...inner end, 18b...outer radial end, 19...set, 20...protrusion, 22...opening, 30...insulating ring, 32...tubular insulator body, 32a...first axial end, 32b...second axial end, 33A...inner circumferential surface, 33B...outer circumferential surface, 34...axial portion, 36...radial portion, 36a...first axial end, 36b...second axial end, 37...annular groove, 38b...outer end, 40...annular protrusion, 52...mounting tab, 60...annular retainer, 60a...inner axial end, 62...annular groove, 68...circular hoop

Claims

1. 1. A combined electrical insulator and conductor assembly for a bearing positionable between a shaft and a housing, the bearing having an inner ring, an outer ring having an outer circumferential surface and opposite first and second axial ends, and a plurality of rolling elements between the outer ring and the inner ring, the housing having an inner circumferential surface, the combined electrical insulator and conductor assembly comprising: an annular insulator positionable around the outer ring and configured to prevent current flow between the outer ring and the housing; an electrical conductor fixedly coupled to the annular insulator, the electrical conductor having an inner radial end and an outer radial end, wherein at least one of the outer radial end of the electrical conductor and a portion of the electrical conductor between the inner radial end and the outer radial end is conductively engageable with the housing, and the inner radial end of the electrical conductor is engageable with an outer surface of the shaft to provide a conductive path between the shaft and the housing.

2. the electrical conductor having a centerline and a plurality of openings circumferentially spaced about the centerline; 2. The assembly of claim 1, wherein the annular insulator has a centerline and a plurality of projections extending axially along and circumferentially spaced about the centerline, each projection extending through a different one of the openings in the electrical conductor and having an outer end attached to the electrical conductor to fixedly couple the electrical conductor to the annular insulator.

3. The annular insulator is an insulating ring coupled to the first axial end of the outer ring of the bearing, the insulating ring being formed of an insulating material and providing the plurality of protrusions; 3. The assembly of claim 2, comprising: a tubular insulator body having an inner circumferential surface positionable about the outer circumferential surface of the outer ring of the bearing and an outer circumferential surface engageable with the inner circumferential surface of the housing, a first axial end coupled to the insulating ring, and an opposite second axial end, the tubular insulator body being formed of an electrically insulating material or at least one of the inner circumferential surface and the outer circumferential surface being provided with an insulating layer.

4. 4. The assembly of claim 3, wherein the insulating ring has an axial portion disposed around a portion of the outer circumferential surface of the outer ring of the bearing and a radial portion extending inward from the axial portion, the radial portion having a first axial end disposed in abutment against the first axial end of the outer ring of the bearing and an opposite second axial end, and the plurality of protrusions extending axially from the second axial end.

5. 5. The assembly of claim 4, wherein the insulating ring has an annular groove, and the first axial end of the tubular insulator body has an annular protrusion disposed within the annular groove to couple the tubular insulator body with the insulating ring.

6. The electrical conductor is an electrically conductive disk having an outer end providing the outer radial ends of the electrical conductors, an inner radial end defining a central opening for receiving a portion of the shaft, and a plurality of through holes each providing a separate one of the openings for the electrical conductors; 3. The assembly of claim 2, further comprising: an annular conductive brush subassembly coupled to the electrically conductive disk and including a centerline and a plurality of electrically conductive fibers, the electrically conductive fibers being circumferentially spaced about the centerline and extending radially inward from the inner radial end of the electrically conductive disk, each electrically conductive fiber having an inner end contactable with the outer surface of the shaft to provide the inner radial end of the electrical conductor.

7. 7. The assembly of claim 6, wherein the electrically conductive disk includes a plurality of mounting tabs spaced circumferentially about the centerline, each of the mounting tabs being engaged with the annular conductive brush subassembly to couple the annular conductive brush subassembly to the electrically conductive disk.

8. 7. The assembly of claim 6, wherein the annular conductive brush subassembly includes an annular retainer connected to the electrically conductive disk and having an inner axial end with an annular groove, each one of the plurality of electrically conductive fibers having an outer radial end disposed within the annular groove and extending radially inward from the annular retainer toward the shaft.

9. 9. The assembly of claim 8, wherein the annular conductive brush subassembly further includes a circular hoop disposed within the annular retainer, each one of the plurality of electrically conductive fibers being bent around the hoop, each electrically conductive fiber having two ends capable of contacting the outer surface of the shaft.

10. 7. The assembly of claim 6, wherein the plurality of electrically conductive fibers of the annular conductive brush subassembly are arranged in a plurality of circumferentially spaced apart sets of fibers.

Images