Low torque hydrodynamic lip geometry for bi-directional rotation seals
A hydrodynamically lubricating geometry for the generally circular dynamic sealing lip of rotary seals that are employed to partition a lubricant from an environment. The dynamic sealing lip is provided for establishing compressed sealing engagement with a relatively rotatable surface, and for wedging a film of lubricating fluid into the interface between the dynamic sealing lip and the relatively rotatable surface in response to relative rotation that may occur in the clockwise or the counter-clockwise direction. A wave form incorporating an elongated dimple provides the gradual convergence, efficient impingement angle, and gradual interfacial contact pressure rise that are conducive to efficient hydrodynamic wedging. Skewed elevated contact pressure zones produced by compression edge effects provide for controlled lubricant movement within the dynamic sealing interface between the seal and the relatively rotatable surface, producing enhanced lubrication and low running torque.
1. A hydrodynamic rotary seal for location by a machine component for dynamic sealing engagement with a relatively rotatable surface and serving as a partition between a first fluid of a lubricant supply and a second fluid, comprising:
a static sealing surface adapted to form a sealing interface with the machine component;
a generally circular dynamic lip comprising:
a first wave having a first multi-function edge, at least a portion of said first multi-function edge forming a first ramp section;
a second wave having a second multi-function edge, at least a portion of said second multi-function edge forming a second ramp section,
wherein said first and second ramp sections are adapted to curve toward the relatively rotatable surface;
an elongated dimple including a dimple flank having a generally convex curve-like profile when viewed in longitudinal transverse cross-section, said elongated dimple having a first side formed in part by said first ramp section and a second side formed in part by said second ramp section; and
first and second dimple fillets, said dimple fillets having a generally concave curve-like profile when viewed in longitudinal transverse cross-section and having a sloping profile in the circumferential direction, said dimple fillets being substantially tangent to said dimple flank.
2. The rotary seal of claim 1 , wherein said dimple flank has a variable curvature.
3. The rotary seal of claim 1 , wherein at least one of said first and second dimple fillets has a variable curvature.
4. The rotary seal of claim 1 , wherein each said ramp section partially controls the installed convergence of said elongated dimple with the relatively rotatable surface.
5. The rotary seal of claim 2 , wherein the rate of variation in said variable curvature of said dimple flank partially controls the installed convergence of said dimple flank with the relatively rotatable surface.
6. The rotary seal of claim 3 , wherein the rate and extent of variation in said variable curvature of said at least one dimple fillet partially controls the installed convergence of said dimple fillet with the relatively rotatable surface.
7. The rotary seal of claim 1 , wherein at least a part of each said ramp section is maintained in a compressed, contacting relation with the relatively rotatable surface and at least a part of each said ramp section slopes away from the relatively rotatable surface to form a hydrodynamic wedging geometry.
8. The rotary seal of claim 1 , wherein:
said dynamic lip establishes a first reentrant footprint edge produced by compression of said dimple flank and said first dimple fillet against the relatively rotatable surface, and a second reentrant footprint edge produced by compression of said dimple flank and said second dimple fillet against the relatively rotatable surface.
9. The rotary seal of claim 1 , wherein said first and second waves are substantially mirror images of each other.
10. The rotary seal of claim 1 , wherein said dynamic lip comprises a first lip side adapted to face the first fluid and a second lip side adapted to face the second fluid, wherein said first wave is a clockwise wave and said second wave is a counter-clockwise wave, said clockwise wave is adapted to divert a film of the first fluid toward said second lip side in response to clockwise relative rotation and said counter-clockwise wave is adapted to divert a film of the first fluid toward said second lip side in response to counter-clockwise relative rotation.
11. The rotary seal of claim 1 , wherein substantially all of said first and second multi-function edges are skewed with respect to the direction of relative rotation.
12. The rotary seal of claim 1 , wherein said multi-function edges are curved when viewed in longitudinal transverse cross-section and the curvature of at least some of said multi-function edges varies along at least part of the length of said multi-function edges.
13. The rotary seal of claim 1 , wherein said multi-function edges have a curvature which varies sinusoidally.
14. The rotary seal of claim 1 , wherein said static sealing surface is part of a projecting static sealing lip.
15. The rotary seal of claim 1 , wherein said static sealing surface is a sloped surface.