| 摘要 |
A device for accelerating the initial stroke of hydraulic jacks, comprising a cylinder, a piston provided with sealing-rings, said cylinder fluid feed-orifices and orifices for exhausting fluid through a plurality of calibrated ports arranged in rows in the cylinder periphery at both ends thereof, characterized in that at least one piston-ring (S2, S4) at one end of piston (P) is mounted in its respective groove (R1) with a certain amount of axial and lateral clearance, said groove communicating with the bottom of the piston through at least one port (B1).
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