| 摘要 |
Cylinder (1) with non-return system (21, 22) preventing pressure drop in a chamber (2, 3) of the piston when the supply pressure drops. A distributor device controlled by an auxiliary fluid enables a bypass to the non-return valve to be opened as required to modify the cylinder actuating pressure without the supply to the cylinder having to be cut. The cylinder is preferably a rotary cylinder for use, for example, on a machine tool to hold a workpiece (8), and a rotating seal is placed between the pressurized fluid source or sources (9) and switch unit (14, 24) on the one hand, and cylinder (1) and non-return system (21, 22) on the other.
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