Spring supported dual element face seal with a run surface sleeve

The invention provides a seal for a rotatable shaft. The seal includes an inner case mountable to the shaft and having a body and first and second flanges extending radially outward from the body. The seal includes first and second sealing discs operable to seal against the first and second flanges of the inner case. The sealing discs are immovably associated with a housing spaced from the shaft. A spring encircles the shaft and inner case to urge the sealing discs against the flanges. The spring rate of the spring is controlled to enhance sealing, reduce turning torque, and extend life of the seal.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates to a seal disposed between two relatively moveable parts wherein the seal has a relatively moveable relationship to at least one of the parts and, more specifically, the invention relates to a seal for a rotatable shaft.

2. Related Prior Art

Seals are used in a variety of applications to provide a fluid-tight connection between two parts, such as a rotating shaft and a relatively stationary housing. A first portion of the seal usually encircles the rotating shaft and a second portion is mounted to the housing. The first portion includes a rotating face that cooperates with a non-rotating face associated with the second portion.

It has been observed that providing a fully floating mechanical shaft seal free of clamping distortions and free to align itself perpendicularly to the shaft is desirable. U.S. Pat. No. 3,972,536 discloses a rotating shaft seal assembly including a first ring portion affixed to a shaft with set screws. The rotating shaft seal assembly also includes a second ring portion affixed to a housing and a seal provided between the second ring portion and the first ring portion.

SUMMARY OF THE INVENTION

The present invention provides a seal assembly for relatively moveable parts having an inner case operable to encircle a rotatable shaft. The case includes a body and first and second flanges extending radially outward from the body. The assembly also includes first and second sealing discs encircling the inner case between the first and second flanges. The discs provide respective surfaces that sealingly engage the first and second flanges. A spring also encircles the inner case between the first and second sealing discs and urges the first and second sealing discs against the first and second flanges. In a presently preferred embodiment of the invention, the spring is a wave spring.

The seal assembly according to the present invention can maintain a seal in an environment where a fluid pressure drop can occur. The spring exerts a relatively constant axial force on the sealing disc against the flanges of the inner case. Also, the sealing discs include inner apertures that are sized to permit transverse movement of the shaft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now toFIGS. 1 and 2, the present invention provides a seal assembly10for providing a seal between relatively moveable parts, such as a housing12and a shaft14. The shaft14is rotatable about an axis16relative to the housing12. The housing12and shaft14can be assembled to a vehicle. In alternative embodiments of the invention, the seal can be disposed in any environment having a rotating shaft and a stationary structure.

The assembly10includes an inner case18disposable in axially and rotatably fixed relation about the rotatable shaft14for rotation therewith. The inner case18rotates in response to rotation of the shaft14about the axis16. The inner case18includes a body20and first and second flanges22,24extending from opposite ends26,28of the body20. A length of the body20is defined between the first and second ends26,28. The body20includes an inner surface30facing the shaft14and an outer surface32facing away from the shaft14. The first and second flanges22,24extend radially outward with respect to the axis16from the outer surface32of the body20. The first and second flanges22,24define inwardly facing sealing surfaces34,36, respectively.

The seal assembly10also includes first and second sealing discs38,40that encircle the body20adjacent the first and second flanges22,24. The sealing discs38,40extend substantially perpendicular to the axis16. The discs38,40define surfaces42,44, respectively, that sealingly engage the surfaces34,36, respectively. In alternative embodiments of the invention, the sealing discs38,40could be frusto-conical or any desired shape between the sealing surfaces34,36and the outer case46. It is preferred that the discs38,40be disc-shaped for sealing engagement with the sealing surfaces34,36.

The sealing discs38,40are substantially fixed to the housing12. For example, the flanges22,24move relative to the discs38,40when the shaft14is rotating. In the exemplary embodiment of the invention, the discs38,40are fixedly associated with an outer case46which is mounted to the housing12. The outer case includes first and second flanges48,50. The discs38,40are pressed against the flanges48,50with a spacer element52.

The assembly10also includes a spring54for constantly urging the first and second sealing discs38,40against the first and second flanges22,24, respectively. The spring54encircles the body20between the first and second sealing discs38,40. In a presently preferred embodiment of the invention, the spring54is a wave spring. The spring rate of the spring54is controlled to control the sealing force between the surfaces34,42and the surfaces36,44. The rate of wear of the assembly can be controlled by controlling the sealing force. For example, the greater the spring force, the greater the sealing force and the shorter the life of the assembly.

The spacer element52cooperates with the spring54such that the radially outermost ends of the discs38,40are substantially fixed relative to one another whereas the radially innermost ends of the discs38,40are moveable relative to one another. As a result, the portion of the seal assembly10closest to the moving shaft14is relatively more robust while the portion of the seal assembly10furthest to the moving shaft14is relatively more rigid. The portion of the seal assembly10closest to the moving shaft14can accommodate slight movement of the shaft14along the axis16. The spacer element52can be integral with the outer case46.

Also, the rate of turning torque required to overcome frictional force between the discs38,40and the flanges22,24can be controlled by controlling the spring rate of the spring54. For example, the greater the spring rate, the greater the turning torque required to overcome friction forces. In a presently preferred embodiment of the invention, the assembly10includes first and second washers56,58, to enhance engagement of the spring54with the first and second sealing discs38,40. The washer56is positioned between the spring54and the sealing disc38. The washer56is positioned between the spring54and the sealing disc40.

The spring54enhances the robustness of the seal between the sealing discs38,40and the flanges22,24. For example, in an operating environment where the fluid sealed off by the assembly10is subjected to pressure drops, the spring54can compensate for pressure drops by providing a relatively constant sealing force. The spring54acts concurrently on the sealing cooperation between the surfaces34,42and between the surfaces36,44.

The first and second sealing discs38,40define apertures60,62facing the outer surface32of the body20. The aperture60,62are sized larger than the outside diameter of the outer surface32and a gap is defined between the apertures60,62and the outer surface32. The gap accommodates movement of the shaft14transverse to the axis16.

The radial or transverse overlap between the flanges22,24with respect to the sealing discs38,40is determined in view of the extent of transverse movement of the shaft14. For example, the flange22and the first sealing disc38radially overlap between the aperture60and a surface64defined by the flange22. The extent of this radial overlap is selected such that when the shaft14is offset from the axis16a maximum possible distance, the radial distance between the aperture60and the surface64is sufficient to seal the surface34with the surface42.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the invention may be practiced otherwise than as specifically described. The invention is defined by the claims.