Abstract: A laser cutting head includes a lens for producing a waist in a laser beam, an internal chamber having an inlet for pressurised gas, an outlet nozzle for both the laser beam and a jet of pressurised gas which communicates with the internal chamber, an inner hollow generally cylindrical lens holder which holds the lens. The lens holder has a body which (i) makes sliding engagement with an outer sleeve, (ii) holds the lens and (iii), in use, is axially displaceable away from the nozzle. A plurality of transverse pins extends through slots in the outer sleeve to engage the body of the lens holder, and an outermost adjustable limit ring the axial position of which is able to be reproducibly set, and which engages the sleeve, the adjustable limit ring defining the axial position of the lens holder.

Abstract: The invention relates to a nozzle (16) for emitting solid carbon dioxide particles. The nozzle (16) comprising an inlet (30) for receiving liquid carbon dioxide, a nozzle aperture (32) from which solid carbon dioxide particles flow from the nozzle (16), a duct extending between the inlet (30) and the nozzle aperture (32), the duct having a convergent section (36) and a divergent section (38), and an axially displaceable valve member (42) located within the duct, the valve member (42) having first and second convergent portions and a substantially cylindrical portion located between the first and second convergent portions. The nozzle (16) finds particular use in apparatus for cooling a heated weld zone in a workpiece.