Drilling head with axial vibrations

A drilling head, comprising:

• a drive motor with an axis of rotation;
• a mount with a longitudinal axis and opposite first and second ends, the second end of the mount being coupled to the drive motor so that the longitudinal axis of the mount coincides with the axis of rotation of the motor, wherein the mount is hollow and includes a central recess;
• a tool holder that holds a drill bit coaxial with the longitudinal axis of rotation of the mount;
• a bearing located above the upper surface of the annular element and around the longitudinal axis of the mount,
• wherein the tool holder further comprises a shank extending up from the upper face of the tool holder and interior to the bearing such that the shank is guided with axial slide in the bearing;
• a controlled generator of reciprocating movements contained with the recess, the controlled generator comprising a piezoelectric actuator which generates oscillations directed along the longitudinal axis of the mount;
• and
• suspension elements interposed between the mount and the tool holder, the suspension elements suspending said tool holder from the mount and comprising
• i) a longitudinal coupling member that connects a lower vibrating end of the controlled generator to the tool holder, wherein longitudinal coupling member is sufficiently axially elastic to allow axial oscillation of the tool holder induced by the controlled generator, and wherein said longitudinal coupling member has a torsional stiffness high enough to transmit torsion moment resulting from cutting forces;
• and
• ii) an annular element interposed between the controlled generator and the tool holder, said annular element being of an axial stiffness to transmit axial oscillations, said annular element having a flexural stiffness low enough to reduce bending stresses transmitted to said controlled generator.