Patent ID: 7926171

Claim:
Apparatus for formation of an insulated microwire comprising a conductive metallic central filament within an insulative polymer resin sheath, comprising: generally tubular elongated inner and outer crucibles, for receiving said metal and resin respectively, devices for heating the metal and polymer resin in said crucibles to respective desired temperatures, said inner and outer crucibles being mounted vertically with said inner crucible being mounted within said outer crucible, said outer crucible having a resin inlet opening at its upper end and a cylindrical resin discharge passage at its lower end, wherein the lower end of the outer crucible defines a frustoconical inner surface, having the cylindrical resin discharge passage disposed at the lowest central portion thereof, said cylindrical resin discharge passage terminating at a resin discharge aperture, wherein said generally tubular elongate inner crucible comprises a upper body and a tip affixed to the lower end of the upper body, said upper body having a metal inlet opening at its upper end, wherein said tip defines an outer surface and an inner surface, the outer surface thereof comprising a upper portion of a first larger diameter conforming generally to the outer diameter of said upper body portion of said inner crucible, an intermediate portion, and a elongated lower nipple of a second smaller diameter having a metal discharge aperture therein, an adjustment device for controllably varying the relative axial positions of the inner and outer crucibles, and wherein the length of the elongated lower nipple is longer than the cylindrical resin discharge passage, so that the relative axial positions of said inner and outer crucibles can be adjusted, so as to define the relative location of the resin discharge aperture of the outer crucible with respect to the metal discharge aperture in the lower end of said nipple, without variation in the cross-sectional area of the resin flow passage formed therebetween, whereby a fiber comprising a central filament of said metal surrounded by a sheath of said resin can be drawn from the lower apertures of said inner and outer crucibles.