This sealing mechanism is provided with a cap in an overall sectional configuration of a cramp iron which is made from a synthetic resin, and a resilient sealing body in an overall sectional configuration of a cramp iron. An inner surface of the cap is formed with an inserting groove in which the resilient sealing body is fitted. When the resilient sealing body is fitted in the inserting groove in the cap, this sealing body is partially protruded from inner surface of the cap. The cap is also formed with longitudinal lubricating slots on the outer surface thereof. Moreover, both side surfaces of the cap are provided with a plurality of notches at predetermined regular intervals of place which extend from the outer surface of the cap to the inner surface thereof.