MANUFACTURE OF INSULATED ELECTRIC CABLES

摘要

In the manufacture of an extruded covering on a continuously advancing core by passing the core through the core tube of an extrusion machine which applies a continuous covering on to the core and effecting continuous treatment of the covering by passing the covered core through a chamber sealed to the extrusion machine and containing a fluid medium at super-atmospheric pressure, fluid under pressure is injected into the interior of the core tube of the extrusion machine. The injected fluid is maintained at a pressure which is less than that of the fluid medium by an amount such that the pressure difference across the extruded covering at the extrusion orifice is sufficient to cause the extruded covering to collapse firmly on to the core as it emerges from the extrusion machine but is insufficient to force the extruded covering back along the core tube. The pressure difference is preferably automatically maintained constant by a differential pressure control device associated with the chamber and with the core tube.