Ball-type anti-friction device

摘要

A ball-type anti-friction device which has a housing, a ball cage mounted within the housing for movement relative to the housing between a lower inactive position and an upper active position. The ball cage contains a relatively large ball mounted on relatively small bearing balls so that when the ball cage is in the lower or inactive position, the large ball is below the top surface of the housing and when the ball cage is in the upper or active position, the ball extends above the top surface of the housing. In a first embodiment, the housing contains a double acting fluid drive system. The fluid drive system includes two fluid chambers and a piston connected to the ball cage. The piston is selectively actuated by selective pressurization of the two fluid chambers. In a second embodiment, the ball cage is actuated by a single acting fluid drive system. A piston is connected to the ball cage and is biased downwardly to normally maintain the ball cage and large ball in the lower or inactive position. The housing contains a single fluid chamber which, when pressurized, causes the ball cage and large ball to move to the active or upper position in opposition to the biasing means.