The successful performance of a standard hydrodynamic radial-lip seal requires stringent production controls to maintain the configuration, height, and angle of the hydrodynamic ribs or aids which contact the shaft to create the small hydrodynamic pumps. These minute pumps, if their configuration is maintained, create a pressure differential across the sealing lip which aids in sealing.
However, because of production variations, so-called “hydrodynamic” seals are produced which are not hydrodynamic. Therefore, a need exists for a hydrodynamic seal without complicated hydrodynamic aids. To meet this need, a simple hydrodynamic seal was conceived that enhances the viscous shear pump action of a standard sharp lip radial seal by the application of wave sealing theory principles to the seal contact path. A low modulus, easily deformable material was added to the lip contact to enhance and control the deformation of the waves which are inherent in the lip. These seals were then tested by placing a helical mark on the shaft which would tend to pump oil through the seal.
The bi-modulus seals performed satisfactorily for 400 hours on these pumping shafts which caused standard sharp lip seals to fail immediately. These results show that the bi-modulus seal develops a counteracting sealing pressure and demonstrate that the wave sealing theory defines a viable sealing mechanism.