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(11) | EP 0 106 702 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Drill bit assembly having improved operational life |
| (57) A drill bit assembly has an elongated housing in which a drill is provided with a
generally cylindrical shape for receiving an enlarged tool end with somewhat greater
diameter, the tool having cutting cones for cutting a drill hole in material to be
drilled. Air is fed to a plenum chamber within the housing out of which are fed two
air flows. The first flow is directed to the region of the cutting cones and is of
reduced magnitude sufficient only for removing dust and cuttings away from the bit
assembly up along the sides of the bit. A plurality of vanes are provided on the housing
to direct the first flow into a helical path the general pitch of the vanes. The vanes
are caused to overlap one another in the direction of flow. A plurality of jet nozzles
are provided from the plenum chamber at the side of the housing intermediate each
pair of vanes and aligned so that the second flow will be in line with the first flow
and generally parallel to the vanes in the general direction of the drill end and
away from the cutting cones. Centrifugal force thus imparted keeps particles away
from the drill bit and the pipe extensions and thereby reduces wear. |