| 摘要 |
A hydraulic jack comprising a cylinder, a piston slidable relative to the cylinder, pump means to supply pressurized fluid to the base of the piston, a seal between the piston and the cylinder, means for limiting the stroke of the piston in the cylinder, said means comprising a ring carried by the piston and arranged to expand into a groove in the cylinder wall when the piston reaches the end of its permitted travel, and means for selectively de-activating said stroke limiting means, in order to allow removal of the piston from the cylinder to renew the seal.
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