Patent ID: 8070400

Claim:
A device using a drill bit for the high-speed drilling of boards for printed circuits comprising: a support; a drill head mounted on the support with (a) an associated mandrel having a core shaft with a free end and a first tang, and a tubular member with facing windows each having a base, and (b) a member for locking and driving in the mandrel a drill bit having a second tang, the member including: (i) a pair of rings each having outer jacket portions received in the tubular member and a planar surface and an opposing surface having a planar section and an inclined planar section and a central hole adapted to receive the second tang of the drill bit, and (ii) a seat for the rings obtained at the free end of the core shaft of the mandrel and comprising two juxtaposed annular formations facing one another and interconnected by respective leveled portions and having respective shoulders projecting in a stepped manner towards one another but offset diametrically, wherein the windows have an axial amplitude such as to contain the axial bulk of the rings when bearing on one another with the respective planar sections, leaving, on the side corresponding to these planar sections, an axial play such that the rings are compressed between the shoulder and the opposing base of the corresponding window; a compressed air turbine having a rotor, actuating the mandrel, and rotating to define the drilling speed; an optical encoder for encoding the speed of rotation of the turbine and generating a signal representing this speed; and a control circuit receiving the signal from the optical encoder and driving a proportional valve, the proportional valve supplying compressed air to the turbine as a function of the speed of rotation encoded by the optical encoder.