EXTRUSION HEAD FOR EXPANDED PLASTIC TUBES

摘要

The invention concerns an extrusion head for making tubes comprising at least an plastic layer expanded by extruding a flow of melted plastic material comprising an expansion agent through an annular passage section provided in the extrusion head and wherein the melted plastic material flow comprising the expansion agent is circumferentially distributed and is welded on itself by recombination of the two fronts of the flow, said extrusion head being provided with a specific heat regulating device enabling to heat or cool the melted plastic material comprising the expansion agent after the flow fronts have been recombined.