Extruder for coating a conductor with an insulating layer - has multiway valve with bypass mounted between barrel and extruder head

摘要

In an extruder for applying a heat-shapable insulating layer onto an electrical conductor, wire or cable core, the insulating material is heated in the extruder barrel and forced by the screw in the direction of the orifice of the extruder head. Between the barrel and the extruder head is a multiway valve to which a line that bypasses the extruder head is connected. Used for the extrusion coating e.g. of electrical wires esp. with foamable polyethylene compsns. Extruder may also be used for coating other types of substrates e.g. films, pipes and other profiles. Waste is substantially reduced (e.g. prodn. of defectively or only partly coated wire). Cellular coatings are consistenly uniform, and the multiway valve enables the stream of polymer melt from barrel to extruder head to be interrupted and discharged via the bypass.