| 摘要 |
PROBLEM TO BE SOLVED: To provide a kelly-bar of an earth drill, which has a mounting structure capable of positively holding a cushioning material arranged at an upper edge of a split kelly-bar, and preventing deformation, slipout, and breakage of the cushioning material. SOLUTION: According to the structure of the kelly-bar, a plurality of split kelly-bars 15a to 15d different in horizontal cross-sectional size are fitted to each other with inhibiting relative rotation and permitting vertical relative movement. Then two ring plates 33, 34 are welded to the upper ends of at least one of the split kelly-bars 15b, 15c of the split kelly-bars 15b, 15c, 15d other than the outermost split kelly-bar 15a, in a manner spacing a vertical interval away from each other. Further the cushioning material 32 is fitted into a space between the two ring plates 33, 34 such that its periphery protrudes from peripheral portions of the ring plates 33, 34, and fixed to the ring plates by bolts 35. COPYRIGHT: (C)2008,JPO&INPIT
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