| 摘要 |
<p>A pneumatic piston/cylinder unit comprises primary and secondary pistons 11 and 14 operable in first and second cylinder zones respectively. Each of the primary and secondary pistons divide its respective cylinder zone into two chambers, one of the chambers 12 of the first cylinder zone being connected to one of the chambers 15 of the second cylinder zone via passageway 22 which includes at least one control 23, 25 for the flow of hydraulic fluid therethrough. A tertiary piston 33 is provided in the chamber 12 of the first cylinder zone and divides the chamber 12 into two parts 12a and 12b, one 12b of which is between the primary and tertiary piston. In use the passageway 22, the chamber 15 and the part 12a of the chamber 12 are filled with hydraulic fluid. Application of pneumatic pressure to the chamber 13 of the first cylinder zone causes the primary piston 11 to be displaced until it abuts the tertiary piston 33 whereupon movement of the primary piston may be arrested or controlled.</p> |
