Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
1999-09-14
2001-08-07
Mah, Chuck Y. (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C277S634000, C277S654000, C138S141000
Reexamination Certificate
active
06270082
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to valve stem seals. More particularly, the present invention relates to a coextruded valve stem seal that is suitable for use in an internal combustion engine.
BACKGROUND OF THE INVENTION
In a high-temperature, high-wear environment, such as an internal combustion engine, valve stems and guides will scuff and wear excessively if they are not adequately lubricated. Conversely, too much oil produces a heavy build up of deposits that can eventually cause significant engine problems. Valve stem seals are used to control the amount of oil allowed between a valve stem and a valve stem guide.
In the assembly of a valve system for an engine, it is important that the valve stem fit within an allowable tolerance in the valve stem guide. The valve stem seal is typically provided on the upper end of the valve stem to minimize the amount of oil that runs down the valve stem into the cylinder bore. A valve stem seal generally includes a sleeve designed to secure the seal to a valve stem guide. The inside diameter of the sleeve interfaces with and engages the outside diameter of the guide. The sleeve usually includes a sealing element that is centered about the valve stem to meter the oil that lubricates the inner diameter valve stem interface.
To a significant extent, the effectiveness of the valve stem seal depends on the manner to which the seal is secured to the guide. If the sleeve is not properly positioned in relation to the valve guide, the sealing element might not properly seat upon the valve stem, causing non-uniform contact pressure at the valve stem, undesirable wear patterns on the components, and unpredictable oil control for the valve stem.
Two-component valve stem seals having an inner resilient member and an outer rigid member (and, optionally, a reinforcing spring) are known in the industry. Such conventional seals usually consist of an inner rubber material that is covered by a separately formed outer metal or ceramic material. Because the inner and outer components are formed separately in different manufacturing phases, additional processing techniques or steps are often required to durably connect and/or bond the components to one another. There are a number of disadvantages associated with forming a two-component seal in such a manner. In addition to increasing the chance for misalignment and a poor fit between the inner and outer components, such additional processing techniques or steps may involve supplementary manufacturing techniques, production equipment and tooling, thereby increasing the costs associated with the production of an acceptable valve stem seal assembly.
SUMMARY OF THE INVENTION
The present invention recognizes the limitations associated with currently available valve stem seal assemblies and the production thereof. A principal feature of the present invention is the formation of a valve stem seal by means of a coextrusion technique. By coextruding the inner resilient material and the outer more rigid material, the integrity of the resulting article is improved and the associated design and manufacturing processes can be simplified or reduced. By simplifying the production process, the associated machinery, tooling, manufacturing techniques and costs may be reduced—resulting in the production of a less expensive, better-aligned, and more cohesive multi-component valve stem seal.
A further advantage of utilizing a coextrusion process to form the valve stem seal is the ability to easily adjust or vary the thickness of one or both of the layers of the seal along its length using conventional equipment. By adjusting the thickness of the layers of the valve stem seal, more or less material can be positioned as desired to better meet the needs of the intended application.
In accordance with an embodiment of the invention, a valve stem seal is provided which includes a coextruded sleeve having an upper and lower portion, a central vertical axis and a generally concentric aperture. The sleeve includes an inner layer comprised of a resilient sealing material and an outer layer comprised of a plastic material. In a preferred embodiment of the invention, the lower portion of the sleeve includes a flange having a generally planar bottom surface that extends radially outward. Preferably, the resilient sealing material of the inner layer is made of a rubber material and the outer layer is made of a rigid plastic material. If necessary or desirable, the upper portion of the sleeve may include a metal spring reinforcement to help increase the useful life of the part.
A method for making an improved valve stem seal as described above is also disclosed as a further aspect of the present invention. By reducing the number of processing steps needed to manufacture the valve stem seals, the disclosed method provides a number of advantages over present valve stem seal construction techniques.
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Dana Corporation
Mah Chuck Y.
Patel Vishal
Rader & Fishman & Grauer, PLLC
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