| 摘要 |
Arrangement in a pressing tool for sheet metal forming in order to shut off or retard an oil flow in a hydraulic system at an arbitrarily chosen time in coordination with the closing and opening movements of the said tool. When the tool closes, a non-return valve (6) permits a flow in one direction from a primary hydraulic cylinder/piston unit (7), which is thereby compressed, to an accumulator (8). A first valve (9) selectively permits a flow between the accumulator (8) and a secondary hydraulic cylinder/piston unit (10) which, in the event of such a flow, passes from a compressed basic position to an expanded position. Parallel with the non-return valve (6) is a second valve (11) which, when the primary hydraulic cylinder/piston unit (7) has been relieved by opening of the tool, will selectively permit a return flow to the primary hydraulic cylinder/piston unit (7) from the accumulator (8) or, if the first valve (9) is also opened, from the secondary hydraulic cylinder/piston unit (10), which is designed to be then returned to the compressed basic position.
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