Motor ground seal

• US 20070138748A1
• Filed: 03/17/2006
• Published: 06/21/2007
• Est. Priority Date: 06/25/2005
• Status: Active Grant

• Current Assignee: Inpro/Seal LLC (Waukesha Bearings Corporation)
• Original Assignee: Isotech of Illinois
• Inventors: Orlowski, David, Coe, Thomas
• Granted Patent: US 7,521,827 B2
• Time in Patent Office: Days
• US Class Current: 277/412
• CPC Class Codes: F16C 33/80 Labyrinth sealings F16C33/761 takes precedence
• CPC Class Codes: F16J 15/4478 Pre-assembled packings
• CPC Class Codes: H02K 11/40 Structural association with grounding devices
• CPC Class Codes: H02K 5/10 with arrangements for protection from ingress, e.g. water or fingers
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

A shaft seal assembly is disclosed having a stator including a main body and axial and radial projections therefrom. The rotor is radially extended and encompasses the axial and radial projections from said stator. A passageway formed between the radial projection of stator and rotor results in an axial passageway having its opening facing rearwardly from the rotor and away from the source of impinging coolant and/or contaminant. A concentric circumferential receptor groove in the stator facing the housing allows insertion of conductive means for transmission of electrostatic charge away from the shaft through the shaft seal assembly to the housing and ground. The receptor groove is opposite the axial passageway and provides for both a substantially lower contaminant environment and improved engagement with conductive means. The dimension of interface gap between the rotor and the radial projection from the stator, which the access to the shaft of any impinging material is fixed at a predetermined value and does not vary with the relative movement between the rotor and the stator. The shaft seal assembly provides improved rejection or warding off of contaminants from ingress into the labyrinths and ultimately restrains attack of the bearing environment as well as substantial elimination of bearing current and attendant bearing fluting or frosting.

Claims

1. A labyrinth type seal for sealing a rotatable shaft entering a grounded housing comprising:

a) a housing;

b) a stator surrounding a shaft and affixed to the housing, said stator having a main body and projections extending both axially and radially beyond said main body, said radial projections being greater than said axial projection;

c) a rotor surrounding said shaft and rotatively connected to said shaft;

said rotor having a main body and projections extending both radially and axially;

d) a circular circumferential receptor groove placed within the rotor and facing said shaft;

e) a circumferential conductive means, said conductive means placed within said receptor groove and engaged with said shaft to conduct electrical currents away from said shaft to said grounded housing; and

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f) said rotor and said stator abutted and intermeshed with each other on said shaft, said rotor radial projections extending radially outwardly farther than any radial projections of said stator.

2. A seal accordance to claim 1 wherein the radial space between said radial rotor projections and said radial stator projections forms a first axial passage.

3. A seal in accordance with claim 2, wherein said first passageway includes a first axial passage opening to a space in said stator and facing the body of the stator between said housing and the radial extensions of the rotor and stator.

4. A seal in accordance with claim 3, wherein said dimension of said axial passage is constant.

5. A seal in accordance with claim 4, wherein the dimension of said axial passage is predetermined.

6. A seal in accordance with claim 3, wherein said opening of said axial passage faces away from injected coolant, said rotor projection and towards said housing.

7. A seal accordance with claim 2, wherein said main body of said stator surrounds a portion of said rotor.

8. A seal in accordance with claim 2, wherein the radius of the radial internal surface of the rotor radial projection encompassing said stator is greater than the radius of the exterior surface of said radial projection of said stator.

9. A seal in accordance with claim 1, wherein there is at least one labyrinth formed between the main body of said stator and the main body of said rotor.

10. A seal in accordance with claim 1, wherein said rotor and said stator are restrained from relative axial movement between each other.

11. A seal in accordance with claim 1, wherein a groove is formed in said main body of said stator, said groove augmenting the radial extension of said radial projection from said stator.

12. A shaft seal assembly as described in claim 1 wherein the conductive means promotes conduction of shaft voltage and is selected from the group consisting of fibrous conductive brushes, a metallic insert with solid conductor ring, a conductive insert ring having a metallic base and a solid conductive ring and combinations thereof.

76. A labyrinth type seal for sealing a rotatable shaft entering a grounded housing according to claim 1 wherein said stator and rotor are comprised of a low resistivity material selected from the group consisting of aluminum, bronze, copper, gold and combinations thereof.

13. A labyrinth type seal for sealing a rotatable shaft entering a grounded housing comprising:

a. a grounded housing;

b. a stator surrounding a shaft and affixed to the housing, said stator having a main body and projections extending both axially and radially beyond said main body, said radial projections being greater than said axial projection;

c. a rotor surrounding said shaft and rotatively connected to said shaft;

said rotor having a main body and projections extending both radially and axially;

d. a circular circumferential receptor groove placed within the rotor and facing said shaft;

e. a circumferential brush ring having an annular frame, said frame including;

i. first and second frame members defining an annular channel;

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

f. wherein said electrical charges produced through ionization are collected for conduction through said filament brushes to and through said annular frame, to and through said stator and to said grounded housing, away from said shaft; and

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g. said rotor and said stator are abutted and intermeshed with each other on said shaft, said rotor radial projections extending radially outwardly farther than any radial projections of said stator.

14. A seal in accordance with claim 13 wherein the radial space between said radial rotor projections and said radial stator projections forms a first axial passage.

15. A seal in accordance with claim 14, wherein said first passageway includes a first axial passage opening to a space in said stator and facing the body of the stator between said housing and the radial extensions of said rotor and said stator.

16. A seal in accordance with claim 15, wherein said dimension of said axial passage is constant.

17. A seal in accordance with claim 16, wherein the dimension of said axial passage is predetermined.

18. A seal in accordance with claim 15, wherein said opening of said axial passage faces away from injected coolant, said rotor projection and towards said housing.

19. A seal accordance with claim 14, wherein said main body of said stator surrounds a portion of said rotor.

20. A seal in accordance with claim 14, wherein the radius of the radial internal surface of the rotor radial projection encompassing said stator is greater than the radius of the exterior surface of said radial projection of said stator.

21. A seal in accordance with claim 13, wherein there is at least one labyrinth formed between the main body of said stator and the main body of said rotor.

22. A seal in accordance with claim 13, wherein said rotor and said stator are restrained from relative axial movement between each other.

23. A seal in accordance with claim 13, wherein a groove is formed in said main body of said stator, said groove augmenting the radial extension of said radial projection from said stator.

24. A seal in accordance with claim 13, wherein said receptor groove has a tapered bore allowing said circumferential brush ring, having an outer diameter slightly greater than the inside diameter of said receptor groove, thereby force fitting said circumferential brush ring into said receptor groove.

25. A seal in accordance with claim 22, wherein the difference between said receptor groove inside diameter and said circumferential brush ring does not exceed 0.005 inches (0.127 mm).

26. A seal in accordance with claim 22, wherein said stator to be inserted in and affixed to said housing has an outside diameter, said stator outside diameter is slightly greater than the inside diameter of said housing, thereby requiring a force fit between said stator and said housing.

27. A seal in accordance with claim 24, wherein the difference between said housing inside diameter and said stator outside diameter does not exceed 0.005 inches (0.127 mm).

28. A seal assembly in accordance with claim 24 wherein engagement of said seal assembly within and to said grounded motor housing forms a concentric directly seated sealing system having the rotating shaft at its center for enhanced transmission of shaft voltage away from said shaft.

29. A seal in accordance with claim 14, wherein said receptor groove has a tapered bore allowing said circumferential brush ring, having an outer diameter slightly greater than the inside diameter of said receptor groove, thereby force fitting said circumferential brush ring into said receptor groove.

30. A seal in accordance with claim 27, wherein the difference between said receptor groove inside diameter and said circumferential brush ring does not exceed 0.005 inches (0.127 mm).

31. A seal in accordance with claim 28, wherein said stator to be inserted in and affixed to said housing has an outside diameter, said stator outside diameter is slightly greater than the inside diameter of said housing, thereby requiring a force fit between said stator and said housing.

32. A seal in accordance with claim 29, wherein the difference between said housing inside diameter and said stator outside diameter does not exceed 0.005 inches (0.127 mm).

33. A seal assembly in accordance with claim 29 wherein engagement of said seal assembly within and to said grounded motor housing forms a concentric directly seated sealing system having the rotating shaft at its center for enhanced transmission of shaft voltage away from said shaft.

34. A seal in accordance with claim 15, wherein said receptor groove has a tapered bore allowing said circumferential brush ring, having an outer diameter slightly greater than the inside diameter of said receptor groove, thereby force fitting said circumferential brush ring into said receptor groove.

35. A seal in accordance with claim 32, wherein the difference between said receptor groove inside diameter and said circumferential brush ring does not exceed 0.005 inches (0.127 mm).

36. A seal in accordance with claim 33, wherein said stator to be inserted in and affixed to said housing has an outside diameter, said stator outside diameter is slightly greater than the inside diameter of said housing, thereby requiring a force fit between said stator and said housing.

37. A seal in accordance with claim 34, wherein the difference between said housing inside diameter and said stator outside diameter does not exceed 0.005 inches (0.127 mm).

38. A seal assembly in accordance with claim 34 wherein engagement of said seal assembly within and to said grounded motor housing forms a concentric directly seated sealing system having the rotating shaft at its center for enhanced transmission of shaft voltage away from said shaft.

39. A seal in accordance with claim 16, wherein said receptor groove has a tapered bore allowing said circumferential brush ring, having an outer diameter slightly greater than the inside diameter of said receptor groove, thereby force fitting said circumferential brush ring into said receptor groove.

40. A seal in accordance with claim 37, wherein the difference between said receptor groove inside diameter and said circumferential brush ring does not exceed 0.005 inches (0.127 mm).

41. A seal in accordance with claim 38, wherein said stator to be inserted in and affixed to said housing has an outside diameter, said stator outside diameter is slightly greater than the inside diameter of said housing, thereby requiring a force fit between said stator and said housing.

42. A seal in accordance with claim 39, wherein the difference between said housing inside diameter and said stator outside diameter does not exceed 0.005 inches (0.127 mm).

43. A seal assembly in accordance with claim 39 wherein engagement of said seal assembly within and to said grounded motor housing forms a concentric directly seated sealing system having the rotating shaft at its center for enhanced transmission of shaft voltage away from said shaft.

44. A seal in accordance with claim 16, wherein said receptor groove has a tapered bore allowing said circumferential brush ring, having an outer diameter slightly greater than the inside diameter of said receptor groove, thereby force fitting said circumferential brush ring into said receptor groove.

45. A seal in accordance with claim 42, wherein the difference between said receptor groove inside diameter and said circumferential brush ring does not exceed 0.005 inches (0.127 mm).

46. A seal in accordance with claim 42, wherein said stator to be inserted in and affixed to said housing has an outside diameter, said stator outside diameter is slightly greater than the inside diameter of said housing, thereby requiring a force fit between said stator and said housing.

47. A seal in accordance with claim 44, wherein the difference between said housing inside diameter and said stator outside diameter does not exceed 0.005 inches (0.127 mm).

48. A seal assembly in accordance with claim 44 wherein engagement of said seal assembly within and to said grounded motor housing forms a concentric directly seated sealing system having the rotating shaft at its center for enhanced transmission of shaft voltage away from said shaft.

49. A seal in accordance with claim 17, wherein said receptor groove has a tapered bore allowing said circumferential brush ring, having an outer diameter slightly greater than the inside diameter of said receptor groove, thereby force fitting said circumferential brush ring into said receptor groove.

50. A seal in accordance with claim 47, wherein the difference between said receptor groove inside diameter and said circumferential brush ring does not exceed 0.005 inches (0.127 mm).

51. A seal in accordance with claim 47, wherein said stator to be inserted in and affixed to said housing has an outside diameter, said stator outside diameter is slightly greater than the inside diameter of said housing, thereby requiring a force fit between said stator and said housing.

52. A seal in accordance with claim 49, wherein the difference between said housing inside diameter and said stator outside diameter does not exceed 0.005 inches (0.127 mm).

53. A seal assembly in accordance with claim 49 wherein engagement of said seal assembly within and to said grounded motor housing forms a concentric directly seated sealing system having the rotating shaft at its center for enhanced transmission of shaft voltage away from said shaft.

54. A seal in accordance with claim 18, wherein said receptor groove has a tapered bore allowing said circumferential brush ring, having an outer diameter slightly greater than the inside diameter of said receptor groove, thereby force fitting said circumferential brush ring into said receptor groove.

55. A seal in accordance with claim 52, wherein the difference between said receptor groove inside diameter and said circumferential brush ring does not exceed 0.005 inches (0.127 mm).

56. A seal in accordance with claim 52, wherein said stator to be inserted in and affixed to said housing has an outside diameter, said stator outside diameter is slightly greater than the inside diameter of said housing, thereby requiring a force fit between said stator and said housing.

57. A seal in accordance with claim 54, wherein the difference between said housing inside diameter and said stator outside diameter does not exceed 0.005 inches (0.127 mm).

58. A seal assembly in accordance with claim 52 wherein engagement of said seal assembly within and to said grounded motor housing forms a concentric directly seated sealing system having the rotating shaft at its center for enhanced transmission of shaft voltage away from said shaft.

60. The method of claim 57 including at least one labyrinth between the rotor and main body of the stator.

61. The method of claim 58 including the steps of connecting the stator to the rotor to prevent relative axial movement between the stator and the rotor.

62. A method of sealing a shaft exiting a housing and conducting electrostatic charge in accordance with claim 57 wherein the conductive means is a fibrous brush.

65. A seal accordance to claim 62 wherein the radial space between said radial rotor projections and said radial stator projections forms a first axial passage.

68. A seal in accordance with claim 65, wherein the dimension of said axial passage is predetermined.

72. A seal in accordance with claim 62, wherein there is at least one labyrinth formed between the main body of said stator and the main body of said rotor.

73. A seal in accordance with claim 62, wherein said rotor and said stator are restrained from relative axial movement between each other.

74. A seal in accordance with claim 62, wherein a groove is formed in said main body of said stator, said groove augmenting the radial extension of said radial projection from said stator.

75. A labyrinth type seal assembly for reducing common mode as described in claim 62 wherein the conductive means promotes conduction of shaft voltage and is selected from the group consisting of fibrous conductive brushes, a metallic insert with solid conductor ring, a conductive insert ring having a metallic base and a solid conductive ring and combinations thereof.

77. A labyrinth type seal for sealing a rotatable shaft entering a grounded housing according to claim 13 wherein said stator and rotor are comprised of a low resistivity material selected from the group consisting of aluminum, bronze, copper, gold and combinations thereof.

78. A seal assembly in accordance with claim 26 wherein said stator and rotor are comprised of a low resistivity material selected from the group consisting of aluminum, bronze, copper, gold and combinations thereof.

79. A seal assembly in accordance with claim 31 wherein said stator and rotor are comprised of a low resistivity material selected from the group consisting of aluminum, bronze, copper, gold and combinations thereof.

80. A seal assembly in accordance with claim 36 wherein said stator and rotor are comprised of a low resistivity material selected from the group consisting of aluminum, bronze, copper, gold and combinations thereof.

81. A seal assembly in accordance with claim 41 wherein said stator and rotor are comprised of a low resistivity material selected from the group consisting of aluminum, bronze, copper, gold and combinations thereof.

82. A seal assembly in accordance with claim 46 wherein said stator and rotor are comprised of a low resistivity material selected from the group consisting of aluminum, bronze, copper, gold and combinations thereof.

83. A seal assembly in accordance with claim 51 wherein said stator and rotor are comprised of a low resistivity material selected from the group consisting of aluminum, bronze, copper, gold and combinations thereof.

84. A seal assembly in accordance with claim 56 wherein said stator and rotor are comprised of a low resistivity material selected from the group consisting of aluminum, bronze, copper, gold and combinations thereof.

59. A method of sealing a shaft exiting a grounded housing and conducting electrostatic charge away from said shaft to the grounded housing, the method comprising:

a) fixing a stator having a main body and a projection extending both radially and axially beyond the main body of said stator concentrically about the shaft wherein the radial projections are greater than the axial projection;

b) mounting a rotor sealed on the shaft in close relation to the housing for rotation with the shaft and providing the rotor with radial projections extending radially outwardly farther than any radial projections of said stator and said rotor encompassing the radial extremity of the radial projection of the stator and having overlapping radially spaced surfaces forming an axial passage between the surfaces of the rotor and the stator projections, wherein said opening of said axial passage faces away from said rotor and toward the body of said stator;

c) mounting a conductive means within said rotor to engage said shaft and promote transmission of shaft voltage bearing currents; and

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d) transmitting said shaft voltage from said shaft through said conductive means, said rotor and said grounded housing.

63. An improved electric motor comprising:

a) an electrically grounded motor housing;

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

c) a motor ground seal assembly further comprising;

i. a stator surrounding a shaft and affixed to the housing, said stator having a main body and projections extending both axially and radially beyond said main body, said radial projections being greater than said axial projection;

ii. a rotor surrounding said shaft and rotatively connected to said shaft;

iii. a circular receptor groove placed within said rotor and facing said shaft;

iv. a circular conductive means;

v. wherein said rotor and said stator abutted and intermeshed with each other on said shaft, said rotor radial projections extending radially outwardly farther than any radial projections of said stator; and

,

vi. said rotor having a main body and projections extending both radially and axially; and

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d) said circular conductive means is placed within said circular receptor groove and engaged with said shaft to conduct electrical currents away from said shaft to said grounded housing.

66. A seal in accordance with claim 63, wherein said first passageway includes a first axial passage opening to a space in said stator and facing the body of the stator between said housing and the radial extensions of the rotor and stator.

69. A seal in accordance with claim 66, wherein said opening of said axial passage faces away from injected coolant, said rotor projection and towards said housing.

71. A seal in accordance with claim 63, wherein the radius of the radial internal surface of the rotor radial projection encompassing said stator is greater than the radius of the exterior surface of said radial projection of said stator.

64. A labyrinth type seal system for reducing common mode voltage comprising:

a) a variable frequency drive using a pulse width modulated inverter producing a common mode voltage;

b) a motor having;

i. a housing;

ii. a shaft;

c) a motor ground seal assembly having;

i. a rotor surrounding said shaft and rotatively connected to said shaft;

ii. a stator circumferentially surrounding said shaft and affixed to said housing, wherein said rotor and said stator are abutted and intermeshed with each other on said shaft;

iii. a circumferential receptor groove formed in said stator to face said shaft and positioned within said housing;

iv. a circumferential conductive means, said conductive means placed within said receptor groove to promote conduction of electrical currents away from said shaft through said motor ground seal assembly to said grounded housing; and

,

d) said rotor and said stator of said motor ground seal assembly abutted and intermeshed with each other on said shaft, said rotor radial projections extending radially outwardly farther than any radial projections of said stator.

67. A seal in accordance with claim 64, wherein said dimension of said axial passage is constant.

70. A seal accordance with claim 67, wherein said main body of said stator surrounds a portion of said rotor.