Laser welding head and process

1. A laser welding head comprising at least:

a first nozzle to inject a protective gas, the first nozzle being annular and arranged around an unobstructed optical axis passing through the laser welding head;

a protective chamber with a transverse flow of air, the chamber having an air admission and an air exhaust in a register with the air admission in a plane that is substantially perpendicular to said optical axis;

an air deflector downstream from said air exhaust, the air deflector being outwardly inclined away from the first nozzle; and

a second nozzle to inject protective gas, the second nozzle being arranged behind the first nozzle relative to a direction of advance of the laser welding head.

2. The laser welding head according to claim 1 , defining at least one lateral opening between the protective chamber and the first nozzle.

3. The laser welding head according to claim 1 , wherein said air exhaust is oriented in a direction opposite from the direction of advance of the laser welding head.

4. The laser welding head according to claim 1 , wherein said protective chamber is defined in an axial direction by at least one annular washer situated around said optical axis.

5. The laser welding head according to claim 1 , wherein said first nozzle includes a plenum chamber upstream from an annular outlet.

6. The laser welding head according to claim 5 , wherein said first nozzle includes a bent passage between the plenum chamber and the annular outlet.

7. The laser welding head according to claim 1 , including an element made of insulating material interposed between the protective chamber and the first nozzle.

8. The laser welding head according to claim 1 , wherein a distance between an outlet from the first nozzle and the protective chamber is adjustable.

9. The laser welding head according to claim 1 , wherein the second nozzle is incorporated in a traveler fastened behind the laser welding head.

10. The laser welding head according to claim 9 , wherein the traveler comprises a plate with lateral skirts, and the second nozzle is configured to inject protective gas in a space between the plate and the lateral skirts.

11. A laser welding method using a laser welding head including at least: a first nozzle to inject a protective gas, the first nozzle being annular and arranged around an unobstructed optical axis passing through the laser welding head, a protective chamber with a transverse flow of air, the chamber having an air admission and an air exhaust in a register with the air admission in a plane that is substantially perpendicular to said optical axis, an air deflector downstream from said air exhaust, the air deflector being outwardly inclined away from the first nozzle, and a second nozzle to inject protective gas, the second nozzle being arranged behind the first nozzle relative to a direction of advance of the laser welding head, said method comprising:

focusing a laser beam along the optical axis on a focal point situated under the first nozzle;

injecting protective gas around the focal point through the first nozzle;

flowing the transverse flow of air in said protective chamber and deflecting the transverse flow of air away from the focal point by the air deflector;

advancing the laser welding head along a direction of advance perpendicular to the optical axis; and

injecting protective gas, behind the first nozzle relative to the direction of advance of the laser welding head, through the second nozzle.