US Patent 7597328 Seal assembly for reciprocating shaft

A seal assembly for a reciprocating shaft includes a body having a bore and a shaft adapted to move reciprocally within the body between an extended position extending from the body and a retracted position retracted within the body. The shaft has a first seal travel area which is in contact with a first seal during axial reciprocating movement of the shaft. The shaft has a second seal travel area which is in contact with a second seal during axial reciprocating movement of the shaft. The first seal travel area and the second seal travel area are axially spaced separate and distinct areas on the shaft. Damage to the exposed portion of the first seal travel area leading to a failure of the first circumferential seal, does not lead to failure of the second circumferential seal.