| 摘要 |
A housing ( 3 ) has an upper end wall ( 3 a) which supports an upper slide portion ( 11 ) of a clamp rod ( 5 ) vertically movably. The housing ( 3 ) has a lower end wall ( 3 b), a support cylinder ( 13 ) of which supports a lower slide portion ( 12 ) of the rod ( 5 ) vertically movably. The rod ( 5 ) is provided with an input portion ( 14 ) between the upper slide portion ( 11 ) and the lower slide portion ( 12 ). A clamp spring ( 20 ) connected to the input portion ( 14 ) drives the rod ( 5 ) downwards for clamping. The lower slide portion ( 12 ) has an outer periphery provided with a helical rotary groove ( 27 ) and a straight groove ( 28 ) which is in upward continuity with the rotary groove ( 27 ). A ball ( 29 ) engages with the rotary groove ( 27 ) and the straight groove ( 28 ). The ball ( 29 ) is supported by an inner wall ( 13 a) of the support cylinder ( 13 ).
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