| 摘要 |
The present invention is an improved drill head unit in which the lower portion of the drill chuck has a lobed shaped cross section which fits into a corresponding lobed shaped opening in a shaft connected to a spiral bevel gear mounted for rotation about a vertical axis. The lobed shaped cross section replaces the spline drive previously used in such units, and the spiral bevel gears replace the bevel gears previously used. An improved and simplified radial elastomeric seal is provided to separate a vacuum pressurized cavity in the housing from a lubricating cavity in the housing, and a locking mechanism locks against the drill steel such that the drill steel can be withdrawn from a drilled hole by lowering the drill head unit.
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