Spindle for drilling head

1 . A spindle for a drilling head, having a substantially tubular or annular shape, and a clearance arranged to be coaxial with a drilling axis, comprising:

gripping members or gripping jaws configured to grip a drilling rod;

an actuator for selectively opening and closing said gripping members or jaws, wherein said actuator rotates around said drilling axis integrally with said gripping members or jaws, so that there is no bearing between said actuator and said gripping members or jaws;

a rotating part, comprising a flange configured to connect said rotating part to rotating components of the drilling head, said gripping members or jaws, and said actuator; and

a revolving joint comprising a rotary annular element and a collar mounted on said rotary element, wherein the rotary annular element is integral with said rotating part, said collar comprising a constraint configured to prevent a rotation of said collar with respect to said drilling axis,

wherein said revolving joint is in fluid communication with said actuator through a hydraulic circuit that is in fluid communication with the actuator and a locking valve, wherein the hydraulic circuit is configured to rotate integrally with said actuator, and

wherein said revolving joint is mounted on a free end of said spindle, on an opposite end with respect to said flange configured to connect said revolving joint to the rotating components of the drilling head.

2 . The spindle according to claim 1 , wherein said locking valve is mounted in a radially outward position with respect to said actuator.

3 . The spindle according to claim 1 , further comprising one or more mechanical elements mounted between said collar and said rotary annular element to allow an idle rotation of said rotating part of the spindle with respect to said collar of the revolving joint.

4 . The spindle according to claim 3 , wherein said collar of said revolving joint comprises a first supply point for introduction of a fluid into a first delivery duct of the hydraulic circuit fluidically coupled to the actuator through said rotary annular element, and wherein said first delivery duct conveys the fluid through said locking valve to maintain pressure inside the at least one actuator to allow for radially inwardly extending said actuator.

5 . The spindle according to claim 4 , wherein said collar of said revolving joint comprises a second supply point for introduction of the fluid into a second delivery duct of the hydraulic circuit of the actuator through said rotary annular element, and wherein said second delivery duct conveys the fluid through said locking valve in such a way as to release the fluid and feed a return circuit fluidically coupled to said actuator where said actuator is a double-acting actuator.

6 . The spindle according to claim 5 , wherein said locking valve is configured in such a way that said locking valve selectively opens at a first pressure value corresponding to a chamber of said actuator, and selectively closes at a second pressure value corresponding to the chamber of said actuator.

7 . The spindle according to claim 3 , wherein said revolving joint comprises a cooling circuit, said cooling circuit comprising a channel which is obtained within said collar and in which a fluid suited to cool rotating parts and said one or more mechanical elements circulates.

8 . The spindle according to claim 1 , wherein said gripping members or jaws comprises inserts arranged circumferentially around said drilling axis and configured to move away from and towards the drilling axis in order to open or close on said drilling rod, wherein each of said inserts comprises an inclined part with wedges sliding axially thereon, and wherein the actuator acts on said wedges.

9 . The spindle according to claim 1 , wherein said actuator comprises at least one extendable cylinder or two or more independent hydraulic jacks distributed circumferentially around said drilling axis or another device configured to be extended in an axial direction, parallel to said drilling axis.