This invention relates generally to sealing arrangements between rotating and non-rotating components, and in particular, towards a method and apparatus for utilizing micro-channel surface features on at least one of the components to provide improved lubricant sealing between the rotating and non-rotating components.
During the manufacture of a rotating component such as a shaft or bearing member, a surface of the rotating component is commonly machined to a desired diameter via a grinding process. Typically, the grinding process introduces grinding marks or leads along the axial length of the rotating component. If the component is rotating and translating axially during the grinding process, the grinding marks or leads will form a helical pattern on the surface of the rotating component.
An elastomeric component, such as a labyrinth seal, or a seal lip seated against a surface of the rotating component, will not maintain a good seal against a flow of lubricant or the incursion of contaminates if helical or skewed grinding leads are present on the rotating component surface. The helical or skewed grinding leads generate a directional pumping action on the lubricant film between the elastomeric seal lip and the rotating component surface, resulting in lubricant leakage or the introduction of external contaminates into the lubricant reservoir.
Accordingly, when machining the outer diameter of a rotating component in the area in which a circumferential elastomeric seal lip is to be seated, a plunge grinding process is commonly utilized. During the plunge grinding process, the grinding wheel or component is brought into contact with the component surface while the component is held in a fixed longitudinal position and rotated axially, resulting in grinding marks or leads on the component surface in the range of 0.00025 mm (10μ-in.) to 0.0005 mm (20μ-in.) which are generally circumferential, i.e. perpendicular to the component centerline axis.
An ideal “plunge ground” finish avoids the development of any directional pumping action, and allows for a thin film of lubricant to form between the elastomeric seal element lip and the rotating component surface, reducing frictional seal wear, heat generation, and operating torque.
However, some skewed or misaligned secondary grinding marks or leads will generally be present on the surface of the rotating component after a plunge grind process, resulting in undesired directional pumping action for lubricant under the elastomeric seal element lip. These secondary grinding marks or leads may be the result of particulate material trapped between the grinding surface and the rotating component surface during the grinding procedure, or the result of mechanical vibrations occurring during the grinding procedure.
For elastomeric components such as seal lips which contact surfaces between rotating components, the preferred contact width (axial distance) that the elastomeric seal lip covers along the rotating component surface is 0.25 mm (0.01 in.)-1.0 mm (0.04 in.). Any increase in this contact width will prevent a sufficient lubricant film from being maintained, as areas under the elastomeric seal element lip will be insufficiently lubricated and will run dry. Additionally, as the surface wears to a smoother finish, it is less able to maintain a desired lubricant film beneath the elastomeric seal lip.
Previous attempts to provide a better performing wear surface on a rotating component, i.e. one which lowers torque, has reduced heat generation, and which maintains a uniform and stable lubricant film, have employed discrete microstructures on the surface of the rotating component in place of the plunge ground finish, such as shown in prior art
Accordingly, it would be advantageous to provide an elastomeric seal assembly of consistent manufacture, having a long operational life which exerts a reduced amount of torque on the rotating component surface, thereby reducing power consumption and heat generation in a mechanical system, as well as reducing maintenance costs associated with the replacement of worn elastomeric seal components.
Turning to
A set of parallel and uniformly-spaced angular flutes 108 or branches extend from each micro-channel 106. The angular flutes 108 are tapered to a point as they extend from the micro-channel 106, and may have any of a variety of cross-sections, such as semicircular or triangular.
The angular flutes 108 are preferably aligned at an acute angle relative to the micro-channel 106, such that through the rotation of the rotating component 104, a pumping action may be imparted by the angular flutes 108 on either lubricants or contaminates entering the circumferential contact region. The angular orientation of the flutes 108, and their alignment relative to the longitudinal axis A-A of the rotating component 104 determines a resulting longitudinal direction of any pumping action. For example, as shown in
As shown in
Using a combination of micro-channel cross-sectional shapes in a micro-channel seal assembly 100 may provide increased resistance to contaminate penetration while maintaining a desired lubricant film between an elastomeric seal lip and the rotating component 104.
In the preferred embodiment of the micro-channel seal assembly 100 of the present invention, each of the micro-channels 106 and angled flutes 108 has a cross-sectional depth of between 0.001 mm (40μ-inches)-0.002 mm (80μ-inches), and a cross-sectional width of approximately 0.02 mm (0.0008 in.), as shown in
For some seal applications it is desirable to exert a unidirectional pumping action or force on a lubricant film disposed between a surrounding elastomeric seal lip 110 or labyrinth seal (not shown) and the rotating component surface 102. As shown in
Those of ordinary skill in the art will recognize that by incorporating micro-channels 106 having specifically-aligned angular flutes 108 in a micro-channel seal assembly 100, combinations of unidirectional and bi-directional pumping actions or forces may be exerted on a lubricant film disposed in the contact region R between an elastomeric seal lip and a rotating component surface 102, stabilizing the lubricant film or directing lubricant and contaminate flow patterns.
While each of the above embodiments and variations of a micro-channel seal assembly 100 of the present invention has been described in connection with the micro-channels 106 disposed on the outer surface 102 of the rotating component 104, those of ordinary skill in the art will recognize that the micro-channel seal assembly 100 of the present invention may be achieved by disposing the micro-channels 106 with angular flutes 108 on any type of seal surface, such as the inner diametrical surface of the annular elastomeric seal element 110, as shown in
Turning to
Those of ordinary skill in the art will further recognize that a variety of methods may be employed to form the micro-channels 106 and flutes 108 of the present invention on either the rotating component surface 102 or the elastomeric seal surfaces (either directly or by formation in the elastomeric seal mold elements). For example, a LIGA process involving X-ray lithography, electroplating, and plastic molding may be utilized to form the micro-channels 106 or flutes 108 on the surface 102 of the rotating component 104, or alternatively, on a mold surface from which an elastomeric seal element 110 is formed. Alternatively formation methods include laser ablation deposition, electro-discharge machining (EDM), dry etching, ultrasonic machining, ultra-high precision mechanical machining, and electro-less (Ni) plating.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
This application is the US National Phase under 35 U.S.C. §371 of International Application No. PCT/US2005/044026 and which is, related to and claims priority from U.S. Provisional Patent Application No. 60/633,768 filed Dec. 7, 2004 entitled MICRO-CHANNEL SEALS, herein incorporated by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US05/44026 | 12/6/2005 | WO | 5/21/2007 |
Number | Date | Country | |
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60633768 | Dec 2004 | US |