| 摘要 |
In an earth drill rig having a drive with a drive stud projecting from it, a Kelly bar, connected to drive a rotary table, and a coupling device associated with the Kelly bar and drive stud for selectively connecting the drive stud to a lower end of the Kelly bar, and a mast carrying the Kelly bar and adapted to be rotated about a pivot axis offset from the long axis of the Kelly bar from an erected position to a folded position, during which the Kelly bar is arcuately translated away from the drive stud, and to be rotated from the folded position to the erected position, during which the lower end of the Kelly bar is arcuately translated toward the drive stud, the Kelly bar is moved axially in a direction away from the drive stud and moved axially in a direction toward the drive stud to permit the coupling and uncoupling of the Kelly bar and the drive stud.
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