Patent ID: 7388896

Claim:
A cold-crucible-induction melter, comprising: a crucible; a cooling structure disposed about the crucible; a first inductor disposed at a radial position greater than the radial position of the walls of the crucible and corresponding to a first longitudinal region, wherein the first inductor comprises a first induction coil positioned along a longitudinally upper region of the crucible and a second induction coil positioned along a longitudinally intermediate region of the crucible; a second inductor disposed at a radial position greater than the radial position of the walls of the crucible and corresponding to a second longitudinal region, wherein the second inductor comprises the second induction coil positioned along the longitudinally intermediate region of the crucible and a third induction coil positioned along a longitudinally lower region of the crucible; a single power supply having an electrical output suitable for induction heating; wherein an electrical relay or switch is configured to electrically connect the electrical output of the power supply and either the first inductor or the second inductor, and a head assembly positioned longitudinally above the crucible comprising: an inner shell; an outer intermediate shell; an inner intermediate shell; and an outer shell; wherein the inner intermediate shell is disposed between the inner shell and the outer intermediate shell and the outer intermediate shell is disposed between the outer shell and the inner intermediate shell; wherein an inner annulus is formed between the inner shell and the inner intermediate shell, an intermediate annulus is formed between the inner intermediate shell and the outer intermediate shell, and an outer annulus is formed between the outer intermediate shell and the outer shell; and wherein at least two of the inner annulus, the intermediate annulus, and the outer annulus are configured to be gas-cooled.