| 摘要 |
Apparatus for underground drilling includes a housing having a bottomed opening in its top and a hole extending downwardly through the housing from the opening. A rotatable chuck is received in the opening and has a vertical bore therethrough with non-circular upper portion for receiving a hollow drill rod, an intermediate portion and an enlarged lower portion having a shoulder at the top thereof. A compressible plug is closely received in the vertical bore and has an enlarged bottom portion with its top bearing against the shoulder and its bottom bearing against the bottom of the chuck bore. The plug has a frusto-conical upper portion which is compressed by the bottom of the hollow drill rod. A hollow adapter is received in the hole in the housing in spaced relationship with the chuck and has sealing engagement with the hole wall. Water is fed into the hollow adapter and passes therethrough into an axial hole in the plug and then through the hollow drill rod where it is discharged to lubricate the drill and pick up the dust. |
