| 摘要 |
Hydraulic reciprocating drive with a double-acting cylinder (3), the cylinder spaces (1, 2) of which can be alternately connected to a hydraulic pump (8) or a return line (10) via lines (4, 5) which are connected to a 2/2-way directional valve (6). A shut-off valve (170, 180) lies in each of the actuating lines (11, 110; 12, 120) leading to the servo pistons, acting in opposite directions, of the directional valve (6). The shut-off valve (170, 180) is held in the closed position by a spring (21, 22) and is opened by the piston (25) in its stroke end position. For this purpose, the piston (25) is provided with control surfaces (26, 27) which interact with plungers (23, 24), projecting laterally into the cylinder spaces (1, 2), of the shut-off valves (170, 180). Each actuating line (11, 110; 12, 120) is connected to the return line (10) via a choke point (130, 140). When a shut-off valve (170, 180) is opened, the downstream actuating-line section (110, 120) leading to a servo piston of the directional valve (6) receives hydraulic oil, as a result of which the directional valve (6) is changed over, since the allocated choke point (130, 140) produces a pressure rise sufficient for this change-over. The directional valve (6) is actuated by the system pressure so that a quick and reliable change-over is guaranteed even in low-pressure systems. <IMAGE>
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