| 摘要 |
PURPOSE:To enable large rigidity of a tightening cylinder to be obtained for its torsional force, by forming plural grooves on the internal peripheral surface of the tightening cylinder respectively to a shallow depth so that a large thickness is left existing between the bottom of the groove and the peripheral surface of the tightening cylinder. CONSTITUTION:Grooves 10, formed on an internal peripheral surface 5, are formed respectively with their section into a circular arc shape while in parallel with the axial line of a tightening cylinder 3 further in a large length in the axial line direction. While the groove shallowly forms its depth so that a large thickness is left existing between the bottom of the groove and a peripheral surface 7 of the tightening cylinder 3. Annular reinforcing parts 12, 13, respectively provided in sides of an opening part and a deep part from the groove 10, are formed rospectively in a uniform thickness over the whole periphery. The groove 10 shallowly forms its depth to an extent such that the left existing large thickness part below the bottom of the groove supports a forced contact part 11 with both the annular reinforcing parts 12, 13 enabling the forced contact part 11 to be prevented from being deformed in the direction of torsional force when its large amount is transmitted to a held object for the tightening cylinder 3 in a condition that each forced contact part 11 is forced to come into contact with the held object. |
