Patent ID: 8347984

Claim:
A sonic drill head, comprising: a housing; an oscillator assembly positioned within the housing, the oscillator assembly comprising: a first eccentrically weighted rotor having a first eccentric weight configured to rotate about an axis; a second eccentrically weighted rotor having a second eccentric weight configured to rotate about the axis, the second eccentric weight being spaced a fixed distance from the first eccentric weight along the axis; a coupling shaft extending along the axis, the coupling shaft coupling the first eccentrically weighted rotor to the second eccentrically weighted rotor such that rotation of the first eccentrically weighted rotor effects a corresponding rotation of the second eccentrically weighted rotor, the coupling shaft having a straight-splined portion configured for direct engagement with the first eccentrically weighted rotor and a helically-splined portion configured for direct engagement with the second eccentrically weighted rotor, and an actuator operatively associated with the coupling shaft such that movement of the actuator along the axis effects a corresponding axial movement of the coupling shaft along the axis; wherein movement of the coupling shaft along the axis varies the angular separation between the first eccentric weight and the second eccentric weight relative to the axis, and wherein rotation of the first and second eccentric weights about the axis transmits a vibratory force to the housing of the sonic drill head.