Seal with bi-modulus lip

Abstract

A seal for separating a viscous lubricant, such as grease, from contaminants in the surrounding environment, includes case having axial and radial walls, a shield located in the case and also having axial and radial walls, a primary seal element attached to the radial wall of the case and establishing two fluid barriers along the axial wall of the shield, and a secondary seal element attached to the radial wall of the shield and establishing another fluid barrier along the axial wall of the case. The primary seal element includes a labyrinth which is spaced slightly away from the axial wall of the shield and contains pumping cavities which drive the lubricant away from the primary seal element when relative rotation exists between the primary seal element and the shield. The primary seal element also has a contact lip provided with inside and outside beveled surfaces which converge toward a band along which the contact lip bears against the axial wall of the shield. The primary seal element is for the most part molded from an elastomer, but it contains an insert having a higher modulus of elasticity than that of the elastomer. The inside beveled surface, which is presented toward the labyrinth, lies along the insert as does the adjoining region of the band. The outside beveled surface lies along the elastomer as does the adjoining region of the band. The seal is particularly effective under frigid conditions when grease may not migrate to the band on the contact lip to lubricate it.