Valve stem seal assembly with changeable cap

A valve stem seal assembly includes a changeable cap. The cap is made of a flexible material, such as plastic or the like. A sealing element with sealing lips for sealing the valve stem is integrally bonded to the cap. The cap includes one or more tabs with a gripping member that cooperates with a corresponding gripping member on the retainer to snap-fit the cap onto the retainer. The retainer can also be made of plastic material. Once fitted onto the retainer, the cap can be easily removed by constructively destroying the one or more tabs using a tool, such as a screwdriver. A cap with a new sealing element can then be snap-fit on the retainer. The changeable cap allows for replacement of the sealing element without replacing the retainer or other components of the valve stem seal assembly.

TECHNICAL FIELD

The present invention relates to a valve stem seal assembly, and in particular to a seal for a valve stem seal assembly found in overhead valve internal combustion engines.

BACKGROUND OF THE INVENTION

Those skilled in the art will appreciate the manner in which intake and exhaust valves are employed in cylinder heads of internal combustion engines. In conventional overhead valve internal combustion engines, a pair of valves reciprocates in timed alternation to provide intermittent communication between the intake and exhaust manifolds and a combustion chamber. As is well known, the intake port of a combustion chamber is opened and closed by the reciprocating motion of at least one intake valve. The intake valve permits fuel mixed with air to flow into the combustion chamber. In addition, an internal combustion engine has at least one exhaust valve and associated exhaust port for releasing expended combustion gases into the atmosphere. Lubrication is provided to the upper portions of the valves. Because temperatures in the combustion chamber may approach or exceed 1000 degrees Centigrade, any lubricating oil exposed to these temperatures will vaporize or burn leaving behind deposits that may interfere with the proper sealing of the valves and cause rapid deterioration. Valve stem seal assemblies are used to seal against leakage of oil between each valve guide and its associated valve stem.

It is therefore necessary to provide seals around the upper region of the valve stems and along the valve guide down to the manifolds and combustion chamber. A typical valve stem seal takes the form of a cylinder partially closed at one end by the valve seal. The cylindrical region seats about the valve guide to maintain the valve seal stationary. An upper region of the valve stem is surrounded by the valve seal when the valve stem is fully inserted into the valve seal assembly.

Conventional valve seal assemblies comprise individual body and seal components that typically must be assembled into the valve seal assembly. In addition, the valve seal assembly, valve spring and spring retainer must be assembled individually by the end user. Further, the manufacturer must keep an inventory of the valve seal assembly, valve spring and spring retainer. The inventory of such multiple components and associated assembly increases the cost of the assembled valve seal assembly.

SUMMARY OF THE INVENTION

The inventor of the present invention has recognized these and other problems associated with valve stem seal assemblies. To this end, the inventor has developed a valve stem seal assembly with a changeable cap comprising a retainer having an outer surface with a first gripping member, and a cap made of a flexible material and having a tab with a second gripping member for engaging the first gripping member on the retainer to snap-fit the cap on the retainer. The cap is capable of being snap-fit onto the retainer by moving the retainer relative to the cap such that the first gripping member engages the first gripping member. The cap is capable of being removed from the retainer by bending the tab such that the second gripping member on the cap no longer engages the first gripping member on the retainer.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now toFIGS. 1-4, a valve stem seal assembly10includes a retainer12defined by a straight walled cross-section, and a changeable cap13adapted to be snap-fit onto the retainer12. Preferably, the retainer12and cap13are made of a flexible material, such as a plastic material, or the like. The valve stem seal assembly10is adapted to sealingly engage a valve stem22supported in an annular valve guide24for reciprocal movement of the stem in the guide along a longitudinal axis a—a, as will be appreciated by those skilled in the art. The valve guide24extends from an upper surface26of a cylinder head deck28. For this purpose, the guide24may be machined from a cylinder head deck casting that includes the guide. Alternatively, the cylindrical guide24may be press fit into an aperture (not shown) formed in the cylinder head deck.

The cap13is generally annular in shape defining an upper portion17and a lower portion19. As shown inFIG. 3, the cap13includes one or more break-away tabs29extending from the upper portion17to the lower portion19. An interior surface21of each break-away tab29includes one or more gripping members or ribs23adapted to engage one or more gripping members or ribs25extending outwardly from the retainer12. In the illustrated embodiment, the cap13includes four break-away tabs29positioned approximately ninety degrees from each other. However, it will be appreciated that the invention is not limited by the number of break-away tabs29, and that the invention can be practiced with any desired number of tabs to properly snap-fit the cap13onto the retainer12.

Bonded to an interior surface15of the upper portion17of the cap13is an elastomeric sealing material, commonly referred to as a rubber jacket14. The jacket14can be bonded to the plastic cap13by chemical bonding, or the like. An elastomeric upper body portion18and a contiguous elastomeric lower body portion20together define the jacket14. An exterior surface27of the jacket14is spaced from the ribs23approximately equal to a thickness, t, of the retainer12. In addition, the retainer12is spaced from the guide24by a distance, d, such that the retainer12can be received between the jacket12and the cap13, and the jacket12can be received between the guide24and the retainer12, as shown in FIG.2.

The upper body portion18of the rubber jacket14contains an oil sealing lip30adapted for contact with the cylindrical surface of the valve stem22. A gas sealing lip32may be longitudinally spaced from the lip30and positioned proximally to the interface between the valve stem22and the valve guide24. Those skilled in the art will appreciate that the gas sealing lip32is not required in all applications. Whether or not present, however, those skilled in the art will also appreciate that the lip30(and gas sealing lip32) are sized to assure proper lubrication and consequent avoidance of premature damage to the lip30(and gas sealing lip32) due to friction, as well as any frictional scouring of the valve stem22.

For this purpose, the space between the upper body portion18and the valve stem22characterizes a sealing interface34by which the oil sealing lip30and (the gas sealing lip32) are effective for metering oil between the assembly10and the valve stem22, and for assuring appropriate lubrication of a guide interface35between the valve stem and the valve guide24.

The lower body portion20of the rubber jacket14is characterized by a plurality of gripping ribs36. There are a pair of such ribs36in the described embodiment that are adapted to frictionally retain the valve assembly10on a reduced diameter portion38of the guide24. Obviously, the ribs36are sized relative to the outside diameter of the reduced diameter portion38to provide a valve stem seal retention force capable of resisting mechanical pressures attempting to remove or dislodge the seal10from the guide24during engine operation. Although only two such ribs36are displayed in the described embodiment, the number of ribs can be varied, commensurate with retention force requirements for any given application.

As will be apparent fromFIG. 1, the reduced diameter portion38of the valve guide24creates an annular step44that is formed by the distinct diameters of the lower and upper, longitudinally and symmetrically aligned, portions24and38of the guide. The retainer12has an upper extremity40, and a lower extremity42; the lower extremity42bears against a step44, and hence the step44acts as a positive insertion stop for the valve stem seal assembly10during installation. It will be appreciated that the upper extremity50of the guide portion38is vertically spaced from the bottom52of the upper body portion18to optimize sealing effectiveness.

One aspect of the invention is that the cap13with the jacket14bonded thereto can be snap-fit onto the retainer12. To snap-fit the cap13with the jacket14onto the retainer12, the lower body portion20of the jacket14is positioned between an interior surface16of the retainer12and the guide24. At the same time, the retainer12is positioned between the interior surface21of the cap13and the exterior surface27of the jacket14, as shown in FIG.1. Once positioned properly, the cap13and jacket14can be moved relative to the retainer12to form an interference fit between the jacket14and the retainer12and the guide24such that exterior surface27of the jacket14sealingly engages the interior surface16of the retainer12and the sealing lips36of the jacket14sealingly engage the guide24. In addition, the ribs23of the cap13engage the ribs25of the retainer12to removably retain the cap13with the jacket14to the retainer12, as shown in FIG.2.

Another aspect of the invention is that the cap13with the jacket14bonded thereto once snap-fit onto the retainer12can be constructively removed from the retainer12, thereby providing a changeable cap feature of the invention. To constructively remove the cap13with the jacket14from the retainer12, a tool31, such as a screwdriver, or the like, can be positioned underneath the one or more break-away tabs29on the lower portion19of the cap13, as shown in FIG.5. Once positioned underneath the break-away tabs29, the tabs29are bent in an upward direction away from the retainer12such that the ribs23on the cap13no longer engage the ribs25on the retainer12. After the tabs29are bent, the cap13with the jacket14can be easily removed from the retainer12.

In summary, this invention is characterized by a valve stem seal assembly10comprising a retainer12and a changeable cap13with an elastomeric sealing element14chemically bonded to the cap13. The cap13with sealing element14can be snap-fit onto the retainer12, and constructively removed from the retainer12such that a new cap with sealing element can be snap-fit onto the retainer12. The retainer12and the cap13can be made of a flexible material, such as plastic, or the like. The new cap can be the same design or a different design from the original cap. Thus, the present invention allows for the sealing element14to be replaced without the need for replacing the entire valve stem seal assembly, thereby reducing the costs associated therewith.

It should be understood that the aforementioned and other various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby.