Gas Nozzle Having a Displaceable Valve Sleeve

1 . A gas nozzle for a laser machining head, the gas nozzle comprising:

an exit opening for passage of a laser beam onto a workpiece;

an annular gap surrounding the exit opening; and

a sleeve disposed and guided displaceably within the annular gap for axial displacement between a rearward and a forward position,

wherein the sleeve projects beyond the exit opening at least in the forward position,

wherein the sleeve is tiltably mounted in the annular gap, and

wherein a surface part of the sleeve on which a gas pressure acts in a forward direction is larger than a surface part of the sleeve on which the gas pressure acts in a reverse direction.

2 . The gas nozzle of claim 1 , wherein the sleeve has an externally encircling pointed or spherical centering bead that is displaceably guided and tiltably mounted on an external wall of the annular gap.

3 . The gas nozzle of claim 1 , wherein (i) an external wall of the annular gap tapers in a conical manner in a forward direction or (ii) a sleeve wall on an external side tapers in a conical manner in a rearwards direction, or both (i) and (ii).

4 . The gas nozzle of claim 1 , wherein the exit opening is formed by a nozzle exit opening of an inner nozzle for directing a core gas flow onto the workpiece.

5 . The gas nozzle of claim 4 , wherein the annular gap is formed in an outer nozzle for directing an annular gas flow onto the workpiece and the sleeve in the rearward and forward positions opens a nozzle cross-sectional area of the outer nozzle to a different degree.

6 . The gas nozzle of claim 5 , wherein the inner nozzle and the outer nozzle are formed in a nozzle body, and a nozzle bore of the inner nozzle and the annular gap of the outer nozzle are interconnected by at least one connection opening.

7 . The gas nozzle of claim 6 , wherein in the rearward position of the sleeve, an annular space, which is connected to the environment by a guide gap between the nozzle body and the sleeve, remains between a rear end face of the sleeve and the nozzle body, and the at least one connection opening extends from the nozzle bore into the annular space.

8 . The gas nozzle of claim 5 , wherein the inner nozzle and the outer nozzle are formed in a nozzle body, wherein a nozzle bore of the inner nozzle and the annular gap of the outer nozzle are not interconnected, and an annular space between a rear end face of the sleeve and the nozzle body is connected to the environment by a guide gap between the nozzle body and the sleeve.

9 . The gas nozzle of claim 1 , wherein an internal wall of the annular gap is formed by the wall of the exit opening.

10 . The gas nozzle of claim 1 , wherein the sleeve is displaceably guided on an external wall of the annular gap.

11 . The gas nozzle of claim 1 , wherein a front end face of the sleeve has a run-up slant on an internal or an external side of the front end face, or on both an internal and an external side of the front end face.

12 . The gas nozzle of claim 1 , wherein the sleeve comprises a ceramic material, a comparable temperature-resistant and electrically non-conducting material, or a plastic that is temperature resistant up to at least 100° C.

13 . The gas nozzle of claim 1 , wherein the sleeve has a front end face with at least one groove that runs obliquely to the radial direction, or the sleeve has a sleeve wall that has at least one bore that runs obliquely to the radial direction.

14 . The gas nozzle of claim 1 , wherein the sleeve has a sleeve wall which has an external side with at least one groove that runs obliquely to the axial direction.

15 . The gas nozzle of claim 1 , wherein the sleeve has a sleeve wall with at least one bore.