| 摘要 |
PROBLEM TO BE SOLVED: To high accurately position a workpiece of piston or the like with an inner side plane part serving as the reference, by preventing a load from acting in a peripheral equipment of loader or the like. SOLUTION: A clamp pawl 13 holding a piston 1, pawl opening/closing member 14 opening/closing the clamp pawl 13, and a device 12 positioning the piston 1 around a chuck axial line with an inner side plane part 4 serving as the reference are provided in a chuck main unit 11. The positioning device 12 is provided with a base 22 seating the piston 1, pair of rollers 23 coming into line contact with the plane part 4, linear elastic body 24 supporting the roller 23 capable of approaching/separating relating to the plane part 4 in both sides of the chuck axial line, and a wedge member 25 opening/closing the roller 23 by wedge action. The wedge member 25 is supported by a plunger 26, it is energized in an opening direction of the roller 23 by a coil spring 31, the pawl opening/closing member 14 and the wedge member 25 are driven by a drive member 33.
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