Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
2001-04-12
2004-02-03
Knight, Anthony (Department: 3676)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C277S560000
Reexamination Certificate
active
06685194
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to seals that interact with lubricant during rotation of a relatively rotatable surface to wedge a film of lubricant into the interface between the seal and the relatively rotatable surface to reduce wear. More specifically, the present invention concerns the provision of a unique dynamic sealing lip geometry in a hydrodynamic seal that enhances lubrication and environmental exclusion of the seal and controls interfacial contact pressure within the dynamic sealing interface for efficient hydrodynamic lubrication and environmental exclusion while permitting relatively high initial compression and relatively low torque.
FIG. 1
of this specification represents a commercial embodiment of the prior art of U.S. Pat. No. 4,610,319, and
FIG. 1A
represents a commercial embodiment of the prior art of U.S. Pat. No. 5,678,829. These figures are discussed herein to enhance the readers' understanding of the distinction between prior art hydrodynamic seals and the present invention. The lubrication and exclusion principles of
FIG. 1
are also used in the prior art seals of U.S. Pat. Nos. 5,230,520, 5,738,358, 5,873,576, 6,036,192, 6,109,618 and 6,120,036, which are commonly assigned herewith. The aforementioned patents pertain to various seal products of Kalsi Engineering, Inc. of Sugar Land, Tex. that are known in the industry by the registered trademark “Kalsi Seals”, and are employed in diverse rotary applications to provide lubricant retention and contaminant exclusion in harsh environments.
Referring now to
FIG. 1
, the seal incorporates a seal body
18
that is solid and generally ring-like, and defines a lubricant end
20
and an environment end
22
. The seal incorporates a dynamic sealing lip
24
defining a dynamic sealing surface
26
and also defining a circular exclusionary geometry
28
which may be abrupt, and which is for providing environmental exclusion.
The dynamic sealing lip
24
has an angulated flank
30
having intersection with the seal body at lip termination point
32
. Angulated flank
30
is non-circular, and forms a wave pattern about the circumference of the seal, causing dynamic sealing surface
26
to vary in width.
Hydrodynamic inlet radius
38
is a longitudinally oriented radius that is the same size everywhere around the circumference of the seal, and is tangent to dynamic sealing surface
26
and angulated flank
30
. Since hydrodynamic inlet radius
38
is tangent to angulated flank
30
, it also varies in position about the circumference of the seal in a wavy manner. Angulated flank
30
defines a flank angle
40
that remains constant about the circumference of the seal.
When installed, the seal is located within a housing groove and compressed against a relatively rotatable surface to establish sealing contact therewith, and is used to retain a lubricant and to exclude an environment. When relative rotation occurs, the seal remains in stationary sealing contact with the housing groove, while the interface between the dynamic sealing lip
24
and the mating relatively rotatable surface becomes a dynamic sealing interface. The lubricant side of dynamic sealing lip
24
develops a converging relationship with the relatively rotatable surface a result of the compressed shape of hydrodynamic inlet radius
38
.
In response to relative rotation between the seal and the relatively rotatable surface, the dynamic sealing lip
24
generates a hydrodynamic wedging action that introduces a lubricant film between dynamic sealing surface
26
and the relatively rotatable surface.
The compression of the seal against a relatively rotatable surface results in compressive interfacial contact pressure that is determined primarily by the modulus of the material the seal is made from, the amount of compression, and the shape of the seal. The magnitude and distribution of the interfacial contact pressure is one of the most important factors relating to hydrodynamic and exclusionary performance of the seal.
The prior art seals are best suited for applications where the pressure of the lubricant is higher than the pressure of the environment. In the absence of lubricant pressure, the compressed shape of the environment end
22
becomes increasingly concave with increasing compression because the compression is concentrated at one end of the seal. This reduces interfacial contact pressure near circular exclusionary geometry
28
and detracts from its exclusionary performance. In the presence of differential pressure acting from the lubricant side of the seal, the environment end
22
is pressed flat against the wall of the housing groove, which increases the interfacial contact pressure near circular exclusionary geometry
28
and improves exclusionary performance.
Although such seals perform well in many applications, there are others where increased lubricant film thickness is desired to provide lower torque and heat generation and permit the use of higher speeds and thinner lubricants. U.S. Pat. No. 6,109,618 is directed at providing a thicker film and lower torque, but the preferred, commercially successful embodiments only work in one direction of rotation, and are not suitable for applications having long periods of reversing rotation.
Interfacial contact pressure near hydrodynamic inlet radius
38
tends to be relatively high, which is not optimum from a hydrodynamic lubrication standpoint, and therefore from a running torque and heat generation standpoint. Hydrodynamic inlet radius
38
is relatively small, and therefore the effective hydrodynamic wedging angle developed with the relatively rotatable surface is relatively steep and inefficient.
Running torque is related to lubricant shearing action and asperity contact in the dynamic sealing interface. Although the prior art hydrodynamic seals run much cooler than non-hydrodynamic seals, torque-related heat generation is still a critical consideration. The prior art seals are typically made from elastomers, which are subject to accelerated degradation at elevated temperature. For example, media resistance problems, gas permeation problems, swelling, compression set, and pressure related extrusion damage all become worse at elevated temperature. The prior art seals cannot be used in some high speed or high-pressure applications simply because the heat generated by the seals exceeds the useful temperature range of the seal material.
In many of the prior art seals, interfacial contact pressure decreases toward circular exclusionary geometry
28
, and varies in time with variations in the width of the interfacial contact footprint. Neither effect is considered optimum for exclusion purposes. When environmental contaminant matter enters the dynamic sealing interface, wear occurs to the seal and the relatively rotatable surface.
Seal life is ultimately limited by susceptibility to compression set and abrasion. Many applications would benefit from a hydrodynamic seal having the ability to operate with greater initial compression, to enable the seal to tolerate greater misalignment, tolerances, abrasion, and compression set without loosing sealing contact with the relatively rotatable surface.
Prior art seals can be subject to twisting within the housing groove. Such seals are relatively stable against clockwise twisting, and significantly less stable against counterclockwise twisting, with the twist direction being visualized with respect to FIG.
1
. Commonly assigned U.S. Pat. Nos. 5,230,520, 5,873,576 and 6,036,192 are directed at helping to minimize such counter-clockwise twisting.
When counter-clockwise twisting occurs, interfacial contact pressure increases near hydrodynamic inlet radius
38
and decreases near circular exclusionary geometry
28
, which reduces exclusionary performance. Such twisting can also make the seal more prone to skewing within the housing groove.
As described in U.S. Pat. No. 5,873,576, the static sealing surface
27
at the outer diameter of the seal is of larger diameter than the diameter of the mating counter-surf
Dietle Lannie
Gobeli Jeffrey D.
Kalsi Manmohan S.
Andrews & Kurth LLP
Jackson James L.
Knight Anthony
Patel Vishal
LandOfFree
Hydrodynamic rotary seal with varying slope does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydrodynamic rotary seal with varying slope, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydrodynamic rotary seal with varying slope will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3342703