| 摘要 |
PROBLEM TO BE SOLVED: To provide a damping means for kelly-bar for preventing generation of an impact sound by the collision of a kelly-bar with a kelly-drive. SOLUTION: The kelly-drive 4 gives a rotation to the kelly-bar 2 through a key groove and a key by fitting the key protrusively provided in the axial direction of the kelly-bar 2 to the key groove formed in the drive shaft 13 of the kelly drive 4, and rotating the drive shaft 13. In the kelly-drive 4, the damping means for kelly-bar 20 having an annular damping member 22 having a space with the kelly-bar 2 set smaller than that between the drive shaft 13 and the kelly-bar 2 extended through it is directly or indirectly mounted on the upper and lower ends of the drive shaft 13. COPYRIGHT: (C)2004,JPO
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