| 摘要 |
In a power unit as a working member, e.g. for presses for shaping and compacting, for rams, etc., with a working piston (8) movable in a cylinder (7) and having a transmission member (9), the primary cylinder space (7a) delivering the working power is continuously under the pressure of an energy accumulator (18), while the secondary cylinder space (7b) is filled with pressure medium bringing about the equilibrium of forces before the start of work. A first auxiliary piston (33) of large area, to which a second auxiliary piston (24) defining a working space (23a) and projecting with a piston rod (27) into the first auxiliary piston (33) is allocated, subdivides a further cylinder space (23) into a secondary space (23b), receiving the expansion volume of the secondary cylinder space (7b) in a restrictor-free manner, and into a restoring space (23a) and separates a control space (38), which can be pressure-relieved, at the end face, from the secondary space (23b). Via a valve arrangement (3, 4), the control space (38) and the working space (23a) can be relieved and can be loaded with pressure, and the two auxiliary pistons (24, 33) assume their basic position. To obtain a short overall length of the auxiliary-piston unit, to avoid energy losses from the first auxiliary piston (33) and to ensure reliable sealing of the same at the end face, the second auxiliary piston (24) is guided in the cylinder space (23) of the first auxiliary piston (33) and its piston rod (27) projects in a sealing manner through the first auxiliary piston (33) and the control space (38) into a hollow space (29) which can be loaded and relieved via the valve arrangement (3, 4). <IMAGE>
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