| 摘要 |
PROBLEM TO BE SOLVED: To hold an article through proper holding pressure by interposing a hydraulic jack between a clamping body and a clamp arm, converting this holding pressure into a hydraulic pressure and transmitting it to a pressure switch, and stopping an on-off driving means of the clamp arm at the time when a fact that the hydraulic pressure goes up beyond the specified pressure is detected. SOLUTION: A clamping body 12 is connected to a clamp arm via a hydraulic jack 13 being attached to this arm. A flowing hole 17 connects a pressure switch 21 as a pressure detecting means to a mouthpiece 18 communicating to this flowing hole 17 via two connecting members 19 and 20 in a state that oil 15 is poured into a cylinder chamber 13A. This pressure switch 21 is set up so as to output a detecting signal whenever the oil 15 in the cylinder chamber 13A is reached to the specified pressure. Subsequently, when this detecting signal is outputted, a motor driving the clamp arm where the hydraulic jack 13 is installed, is stopped.
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