| 摘要 |
PURPOSE:To reduce the dislocation of the center of a disk to that of an axis of rotation by providing a circular plate having a cross section circular arc shaped circumferential side plane at the axis of rotation. CONSTITUTION:A circular plate 9 fixed at an axis of rotation 4 has the cross section circular arc shaped circumferential side plane, and also, a circular arc side plane 9a is set so as t protrude in the upper side higher than the upper plane 3a of a turntable 3. By descending an adapter 5, the corner part 2a of the center hole 2 in the disk 1 is placed on the circular arc side plane 9a of the circular plate 9, and when the adapter 5 descends, the corner part 2a of the center hole 2 is guided by the circular arc side plane 9a of the circular plate 9, then being slipped to the downward, and the disk 1 is fallen into the circular plate 9 in a state that a part of the circular arc side plane 9a is brought into contact with the center hole 2 in its middle, and is fixed at the upper plane 3a of the turntable 3 by the adapter 5. In this way, the dislocation of the center 1a of the disk 1 is reduced against the center 4a of the axis 3 of rotation.
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