| 摘要 |
PROBLEM TO BE SOLVED: To reduce the equipment cost by making a high cost of variable displacement pump unnecessary, as well as to provide a clamp device for machine tool which can reduce an energy loss by using no large pump when the clamping condition is maintained. SOLUTION: In this hydraulic clamp device for machine tool, a hydraulic cylinder 1; and a hydraulic pressure source connected to the hydraulic cylinder 1 through a changeover valve 4; are provided, and an article 2 is held between the piston rod 1c of the hydraulic cylinder 1 and a fixing surface 3, by extending the hydraulic cylinder 1. In such a hydraulic clamp device, the hydraulic pressure source has a main pump P1 with a large capacity constant discharge amount; and a hydraulic pressure source P2 for leak conpensation; and the main pump P1 is driven in the extension and contraction operation time of the hydraulic cylinder 1, while only the hydraulic pressure source P2 for leak compensation is operated when the condition to clamp the article by the piston rod 1c of the hydraulic cylinder 1 is maintained.
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