| 摘要 |
PROBLEM TO BE SOLVED: To provide a main shaft device by which the rusting of an energizing member for energizing a drawing bar in a clamp mechanism can be removed, breakage can be prevented and durability can be increased. SOLUTION: The drawing bar 17 is supported-through at the central portion in a main shaft 15 supported rotatably inside an outer cylinder 13. A coned disc spring 19 is contained for retaining the drawing bar 17 in a clamp state usually between the main shaft 15 and the drawing bar 17. A containing chamber 20 for the spring 19 is partitioned in a hermetic state by providing a seal ring 53 in an outer peripheral face in the side of the front end in the above drawing bar 17 and by providing a seal ring 51 in the outer peripheral face of a movable member 44 fittingly fixed in the rear end of the drawing bar 17. An inert gas is filled into this hermetically containing chamber 20, and also grease is adhered to the coned disc spring 19. The breakage resistance and the durability can be increased since the coned disc spring 19 is prevented from the rusting by the inert gas and the grease.
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