Thermally energising flowing powder - by interacting laser beam undergoing multiple reflections during descent in waveguide

摘要

A stream of powder from a stirred hopper (52) is fed by a worm to the head of an optical wave guide (80) forming part of a unit delivering energy to the powder to cause melting and energy enrichment before the molten material emerges from the wave-guide foot (24) as a cone (40) for application to a substrate (84) or for reaction. Energy is applied to the descending powder from a laser beam (36) taken down the wave-guide after initial focussing by a lens (34). The wave guide is formed with parallel flat surfaces or a curved zone to cause multiple internal reflections of the beam, enhancing the heating effect. The quite channel wave guide is coated with adhesion-resisting medium. An aperture (62) directing the laser beam may allow passage of a stream (70) of protective medium. In a variation the wave-guide narrows in its downward direction.