Shaft seal having lip supports

A shaft seal includes an elastomeric annular body having an outwardly protruding annular lip. An annular outer case is embedded into the body. An annular insert is positioned adjacent the outer case. An annular inner case is embedded into the body adjacent the insert. The outer case, the insert, and the inner case support the lip.

BACKGROUND OF THE INVENTION

This invention relates in general to seals for use in sealing a lubricant about a rotating element, such as a shaft. More specifically, this invention relates to a shaft seal of the type having a flexible lip that contacts the rotating shaft.

A flexible lip protrudes outwardly from an elastomeric body to form a lip seal for sealing about a rotating shaft. A lip seal retains lubricant on an oil side of the seal and prevents the entry of contaminants from an air side of the seal.

A lip of such a shaft seal is subjected to bending loads and stresses, which reduce the life of the lip. Oftentimes, the lip is integrally molded with the body from an elastomeric material such as rubber.

BRIEF SUMMARY OF THE INVENTION

The present invention includes a shaft seal having a lip. A plurality of supports are provided to support the lip and increase its effective life. An outer case, an insert, and an inner case are embedded in a body to provide lip supports.

In a preferred embodiment, a shaft seal includes an elastomeric annular body having an outwardly protruding annular lip. An annular outer case is embedded into the body. An annular insert is positioned adjacent the outer case. An annular inner case is embedded into the body adjacent the insert. The outer case, the insert, and the inner case support the lip.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A shaft seal10according to this invention is illustrated inFIGS. 1 and 2. The shaft seal10retains lubricant about a rotating shaft100, illustrated only inFIG. 2. The shaft seal10includes multiple lip support elements to prevent catastrophic failure and subsequent loss of lubricant about the shaft100.

The shaft100is mounted in or through a bore of a housing102. A bearing104and a bearing race106can be provided about the shaft100on the side of the shaft seal10. An excluder seal108can be provided about the shaft100on an opposite side of the shaft seal10.

The shaft seal10includes an elastomeric annular body12having an outwardly protruding annular lip14that terminates in an end surface16having a sealing edge17. The lip14engages the shaft100and retains a desired lubricant. Preferably, a plurality of raised or extended areas or pads18are formed on an inner surface of the lip14. The pads18form textured areas that trap lubricant, which aids in the prevention of wear of the lip14. Preferably, the pads18are spaced axially away from the sealing edge17to provide a smooth, annular contact surface20that engages the shaft100. The contact surface20provides a continuous positive contact with the shaft100to eliminate leaks about the shaft100.

Preferably, the body12is molded from a desired material, including rubber. If desired, a plurality of raised portions or bumps22can be formed on the body12. These anti-stick bumps22prevent seals10from sticking to one another during handling, packaging, shipping, and storage. If desired, the bumps22and the pads18can be molded into the body12.

A ring-like outer case30is embedded into the body12. The outer case30includes a radial portion32and an axial portion34. The radial portion32terminates in an end surface36facing the shaft100. Preferably, the end surface36is spaced relatively close to the shaft100, but does not contact the shaft100. The radial portion32provides support for insert40to reduce and/or eliminate extrusion of the lip14during a molding process. In this manner, the radial portion32provides a first lip support.

A ring-like insert40provides a second lip support to reduce and/or eliminate extrusion of the lip14. Preferably, the insert40is formed from a low-friction material such as polytetrafluoroethylene (PTFE). The insert40includes a first radial surface41spaced from a second radial surface42. The insert40also includes a first axial or circumferential surface43that engages the shaft100spaced from a second axial or circumferential surface44. Preferably, the second radial surface42is adjacent to and is supported by the radial portion32of the outer case30.

A ring-like inner case50is embedded into the body and provides a third lip support. The inner case50includes a radial portion52and an axial portion54. The radial portion52terminates in an end surface56, which forms an inner diameter of the case50, facing the shaft100. Preferably, the end surface56is spaced radially outwardly from the first circumferential surface43of the insert40to prevent contact between the inner case50and the shaft100and to minimize pressure concentration at this point. Additionally, the end surface56is spaced radially outwardly from the shaft100to provide a hinge area for the lip14that enhances the lip contact loading. This enhanced lip contact loading provides a load that is concentrated at the sealing edge17and at the continuous contact surface20to provide an effective seal about the shaft100.

The radial portion52extends over a majority of a radial length of the insert40. The axial portion54extends over a majority of an axial length of the insert40. In this manner, the inner case50insulates the insert40from forces and pressures of an application. The inner case50also evenly distributes axial forces to the insert40.

Preferably, the outer case30, the insert40, and the inner case50are molded into the body12. In this manner, assembly tolerances from prior art techniques of high-pressure shaft seals are eliminated.

The outer case30and the inner case50can be formed from any desired load bearing material, including metal and metal alloys.

The shaft seal10can be used in an application with little or no pressure, and in high-pressure applications beyond 1000 psi and more than approximately 3000 psi. The outer case30, the insert40, and the inner case50provide three separate lip supports that prevent catastrophic failure of the shaft seal10.