Grounding brush for mitigating electrical current on motor shafts

• US 20040233592A1
• Filed: 06/25/2004
• Published: 11/25/2004
• Est. Priority Date: 03/17/2003
• Status: Active Grant

• Current Assignee: Illinois Tool Works Inc.
• Original Assignee: Illinois Tool Works Inc.
• Inventors: Oh, Hieyoung W., King, Charles A.
• Granted Patent: US 7,193,836 B2
• Time in Patent Office: Days
• US Class Current: 361/23
• CPC Class Codes: G11B 19/2009 Turntables, hubs and motors for disk drives; Mounting of motors in the drive means for clamping of disk to turntable G11B17/022 and subgroups
• CPC Class Codes: H02K 11/40 Structural association with grounding devices
• CPC Class Codes: H05F 3/02 by means of earthing connections
• CPC Class Codes: H05F 3/04 by means of spark gaps or other discharge devices devices providing for corona discharge per se H01T19/00

Abstract

A grounding brush for mitigating static electric charge on a motor shaft includes a plurality of filaments secured to an annular frame around the shaft, with tips of the filaments disposed in a channel defined by the frame. Conductive powder can be provided in the channel to improve current flow from the shaft to the filaments.

Claims

1. An electric motor comprising:

an electrically grounded motor housing;

a motor shaft disposed in said housing and rotated during operation of said motor; and

a static charge dissipating assembly associated with said shaft and said housing, said dissipating assembly including;

an annular frame secured around said shaft and electrically connected to said housing, said frame defining an annular channel substantially surrounding said shaft; and

a plurality of electrically conductive filaments electrically connected to said annular frame, said filaments being sufficiently small to induce ionization in the presence of an electrical field from static charges on said shaft, said filaments having distal end portions disposed in said channel.

2. The motor of claim 1, said dissipating assembly including an annular plate, and said filaments partially wrapping said plate, with opposite distal end portions of said filaments extending into said annular channel.

3. The motor of claim 1, including electrically conductive powder disposed in said annular channel.

4. The motor of claim 3, said electrically conductive powder being mixed with an oil to form a paste.

5. The motor of claim 3, said dissipating assembly including an annular plate, and said filaments partially wrapping said plate, with opposite distal end portions of said filaments extending into said annular channel.

6. The motor of claim 5, said filaments being of sufficient length that ends of said filaments contact said shaft, at least when said shaft is at rest.

7. The motor of claim 5, said frame including an outer ring and first and second retention rings disposed in said outer ring on opposite sides of said plate and said filaments.

8. The motor of claim 7, said frame further including an inner ring covering said annular channel.

9. The motor of claim 7, said first and second retention rings each having an annular recess facing said shaft, and drain holes for evacuating contaminants from said recess.

11. The motor of claim 1, said filaments being of sufficient length that ends of said filaments contact said shaft, at least when said shaft is at rest.

12. The motor of claim 1, said filaments arranged in bundles.

13. The motor of claim 1, said annular frame including first and second frame members, one said frame member being secured within the other said flame member.

14. The motor of claim 1, said frame including an outer ring and first and second retention rings disposed within said outer ring on opposite sides of said filaments.

10. The motor of claim Shaving a rotor rotating with said shaft, and said filaments arranged substantially parallel to said shaft, with distal ends of said filaments confronting said rotor.

15. A static charge dissipating assembly for association with a shaft of a motor, said dissipating assembly comprising:

an annular flame, said frame including first and second frame members defining an annular channel;

a plurality of electrically conductive filaments electrically connected to said annular frame, said filaments being sufficiently small to induce ionization in the presence of an electrical field, said filaments being retained between said first and second frame members and having distal end portions disposed in said channel.

16. The dissipating assembly of claim 15, including an annular plate, and said filaments partially wrapping said plate, with opposite distal end portions of said filaments extending into said annular channel.

17. The dissipating assembly of claim 15, including electrically conductive powder disposed in said annular channel.

18. The dissipating assembly of claim 17, said electrically conductive powder being mixed with an oil to form a paste.

19. The dissipating assembly of claim 15, said frame including an outer ring and first and second retention rings disposed in said outer ring on opposite sides of said filaments.

20. The dissipating assembly of claim 19, including conductive powder disposed in said channel

21. The dissipating assembly of claim 20, said frame further including an inner ring covering said annular channel.

22. An electric motor comprising:

an electrically grounded motor housing having a face plate;

a motor shaft disposed in said housing and extending through a hole in said faceplate; and

a static charge dissipating assembly disposed around said shaft and secured within said hole of said faceplate, said dissipating assembly including;

an annular frame around said shaft and secured in said hole, said frame including first and second frame members defining an annular channel substantially surrounding said shaft; and

a plurality of electrically conductive filaments held between said frame members, said filaments being sufficiently small to induce ionization in the presence of an electrical field from static charges on said shaft, said filaments having distal end portions disposed in said channel.

23. The electric motor of claim 22, including conductive powder disposed in said channel.