Radial shaft seal, radial shaft seal assembly and method of installation

A radial shaft seal assembly, comprising:

• a shaft extending along a central axis and providing a running surface with a predetermined diameter;
• and
• a radial shaft seal configured for receipt in a housing and about said shaft to sealingly isolate an air-side of the radial shaft seal from an oil-side of the radial shaft seal, comprising:
• an annular mounting portion;
• a seal lip having an annular inner sealing surface extending between an oil-side end and a free air-side end, said inner sealing surface being configured to extend axially along said running surface of said shaft in sealed engagement therewith;
• an annular bridge connected to said oil-side end of said seal lip and to said mounting portion, said bridge extending in radially overlying relation to said seal lip;
• and
• a rigid, substantially planar annular disc extending radially inwardly from an outermost periphery that is fixed to said mounting portion to an innermost periphery that faces said shaft on the air-side of said seal lip, said inner most periphery having an inner diameter greater than the inner diameter of said inner sealing surface to remain out of contact with the shaft, said disc being spaced axially from said seal lip and entirely out of contact with said seal lip when said seal lip is in an unbiased, relaxed state and upon being installed on said shaft, said seal lip initially contacting said disc when said seal lip is moved axially toward the air-side of said radial shaft seal assembly during installation to prevent said seal lip from being rolled and inverted axially toward the air-side of said radial shaft seal assembly.

A method of installing a radial shaft seal onto a shaft, comprising:

• providing a shaft having a running surface;
• providing the radial shaft seal with a seal lip having an annular sealing surface converging from an oil side end to a free air side end while in a free state with an annular bridge attached to the oil side end by a first hinge and diverging to a second hinge while in the free state, the second hinge being attached to an outer annular mounting portion such that the bridge extends in radially overlying relation with the seal lip, the seal further including an annular, substantially planar disc extending radially inwardly from the mounting portion in axially spaced relation from the seal lip, the disc having an oil side facing the seal lip in spaced relation therefrom;
• moving the shaft and the radial shaft seal axially toward one another;
• bringing the oil side end of the seal lip into abutment with an end of the shaft and causing the air-side end of the seal lip to move into abutment with the oil side of the disc;
• and
• bringing the sealing surface into sealing engagement with the running surface and simultaneously causing the air side end of the seal lip to move out of abutment with the projection.