| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem in the conventional devices that a control valve for open/close circuits should be formed as separate units for a speed adjustment, but since the control valve is closed upon holding the open/close circuits, an operating pressure in a cylinder is changed, to give rise to the possibility of malfunctions without control, in the event of occurring of a leakage from the control valve. SOLUTION: An open-circuit control valve and a close-circuit control valve are formed as separate units, as well as each control valve being provided with a flow-rate adjustment means for adjusting an opening area. Moreover, a second valve which is opened by a spring and closed by a pressure in a supply side is provided between a return side and the supply side.
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