Patent ID: 6840521

Claim:
A seal device for sealing a sealed fluid between a housing having a fitting bore and a shaft fitted thereto, comprising: an elastic seal lip of rubber-like material that extends and declines in an annular form from the press-fitting section that is press fitted in the fitting bore of said housing to said shaft on the sealed fluid side and has a sealing face in close contact with the outer circumference of said shaft; and a support ring of certain material harder than the rubber-like material of said seal lip, that is held at its one end by said press-fitting section, extends cylindrically along the inner surface of said seal lip, and has a support section fitting in the expandable inner surface formed at the vicinity of the root of said sealing face; wherein the inner diameter of the corner face of said sealing face is smaller than the outside diameter of said shaft; and wherein the outside diameter of the support section of said support ring is larger than the inside diameter of said expandable inner surface and when said support ring is inserted to expand said expandable inner surface, the inside diameter of the corner surface of said sealing face is also expanded, thereby to allow the corner face of said sealing face to closely contact with said shaft, even if the seal lip receives pressure from the sealed fluid, wherein the outside diameter of the support section of said support ring is determined in a dimensional relationship that the inside diameter of said sealing face is expanded a range of 0.1 to 2.2 mm; and the inside diameter of the corner face of said sealing face is determined to be a range of 0.6 to 2.2 mm smaller than the outside diameter of said shaft.