| 摘要 |
Vibratory drill apparatus is disclosed which is adapted for automatic self-balancing to compensate for variations in hardness of the material being drilled and/or dulling of the cutting blades which occurs during the drilling operation. The apparatus includes a tubular casing adapted to be connected to a rotating shaft and a drill assembly comprising a plurality of coaxially extending pipe members, each being located one within the other, the upper region of the drill assembly being received within the lower region of the casing. A drill head is defined at the lower region of the drill assembly. The pipe members are interconnected such that they are mutually fixed to each other for simultaneous rotation about their axis and such that each pipe member is free to move in the axial direction relative to the other pipe members. Apparatus is provided for periodically applying an impulse torque to the drill assembly which tends to periodically rotate the entire assembly about its axis and for periodically applying to at least one of the pipe members an impulse force in the direction of the axis of the drill assembly. In the preferred embodiment this apparatus includes a pair of rollers adapted to ride over the upper edges of the pipe members, the latter being provided with appropriately shaped cam surfaces. Apparatus for damping vibrations during the drilling operation, for providing forced hydraulic mud circulation and for facilitating the withdrawal of the drill apparatus are also disclosed.
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