Abstract: A hydrodynamic shaft seal formed with a spiral hydrodynamic channel in which successive turns of the channel are of progressively diminishing volume toward an air side of the seal. The channel is made by forming a spirally extending first cut in a surface of the seal, and forming a spirally extending second cut in the surface of the seal adjacent to the first cut such that the first and second cuts intersect below the surface of the seal to produce a spiral channel. The spiral of the first cut has a lead different from the lead of the second cut such that the channel is of progressively diminishing volume along its length. Alternatively, the second cut may have the same lead as the first cut for the first few turns, after which the lead of the second cut may be reduced, to provide a channel of constant volume for the first few turns, followed by a channel portion of reduced volume.

Abstract: A hydrodynamic shaft seal formed with a spiral hydrodynamic channel in which successive turns of the channel are of progressively diminishing volume toward an air side of the seal. The channel is made by forming a spirally extending first cut in a surface of the seal, and forming a spirally extending second cut in the surface of the seal adjacent to the first cut such that the first and second cuts intersect below the surface of the seal to produce a spiral channel. The spiral of the first cut has a lead different from the lead of the second cut such that the channel is of progressively diminishing volume along its length. Alternatively, the second cut may have the same lead as the first cut for the first few turns, after which the lead of the second cut may be reduced, to provide a channel of constant volume for the first few turns, followed by a channel portion of reduced volume.

Abstract: A bidirectional hydrodynamic shaft seal includes an annular plastic disk having a sealing surface or lip provided with two connected spiral grooves extending around the disk axis. One of the spiral grooves spirals outwardly in a clockwise direction, and the other spiral groove spirals outwardly in a counterclockwise direction so that the spiral grooves have multiple intersection points. The shaft seal is designed for operation in either or both directions of shaft rotation.