Method for manufacturing electric wire having wire-enamel-type insulation

Claim 1

Method of manufacturing electric insulated wires for use in magnetic windings for motors, transformers, and the like, which wires comprise a metal core covered with an insulation sheath having a predetermined diameter of a magnitude 10 to 100 micrometers greater than the diameter of the core for a core diameter of 0.1 to 4 mm, comprising the steps of processing a synthetic resin having a melting point of at least 250° C. through a screw extruder with simultaneous heating of the resin to a temperature at least 30° C. higher than said melting point to obtain said resin in a hydrostatic liquid state, forwarding said resin from said screw extruder into an extrusion head for feeding said head with said resin in said hydrostatic liquid state and in a pressure comprised between 10 and 1000 bars, said head having at least one inlet opening for receiving the metal core therein, at least one outlet opening for delivering the insulated wire with the said sheath thereon, and a distribution chamber of a fixed size with static compression means, for bringing said resin onto said core, regulating said pressure to keep it at a constant value, and travelling said core through said extrusion head at a speed such that the resin is pulled along by the core.