TELESCOPIC KELLY BAR

摘要

PROBLEM TO BE SOLVED: To obtain a telescopic Kelly bar easy to exchange buffer members. SOLUTION: The telescopic Kelly bar is formed so that the upper end of an inner Kelly bar 2 is axially more projected than the upper end of a second Kelly bar 4 when most contracting the Kelly bar. A buffer member 42 being in contact with the inner periphery of the second Kelly bar 4 is formed detachably at the outer periphery of the upper end side of the inner Kelly bar 2. The buffer member 42 is installed so that a part of the member is projected to the axial outer side than the upper end of the second Kelly bar 4. Buffer members 44, 46 are also provided likewise in a third Kelly bar 6 and an outer Kelly bar 8. COPYRIGHT: (C)2004,JPO