| 摘要 |
In a rotary drill having a driven rotary table with an axially directed passage through its center of rotation defined by a hollow spindle, a kelly bar extending through the passage, and a chuck mounted on the spindle, plungers are mounted in cylinders in the chuck for radial movement into and out of engagement with shoulders on the kelly bar. A housing surrounds a portion of the chuck. The housing is held against rotation and has a fluid passage through it communicating with an annular manifold channel. Fluid passages in the chuck, associated with each cylinder, communicate at one end with the manifold channel and at another end with the cylinder radially inboard of a piston part of the plunger. Oil under pressure to move the plungers out is caused to leak into bearings positioned axially above and below the manifold, to lubricate, flush and cool them. The plunger has a nose with a depending lip that engages an upper or lower shoulder of the kelly bar when the chuck is forced up or down to drive the kelly bar upwardly or downwardly.
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