Method for continuous production of a composite pipe with socket and apparatus for carrying out the method

摘要

An outer pipe(37) is extruded and expanded to form transverse ribs(38) while a smooth inner pipe(39) is extruded inside the outer pipe and welded to the bases of the ribs(37). At specific points along the continuous extrudate, the outer and inner melt streams are formed into a cylindrical pipe socket(41), the flow rates in each stream being varied independently from each other to compensate for the different lengths of plastic used compared to the production of corrugated pipe. An Independent claim is made for the process equipment which includes circulating split molds(12) at least one of which has a cut-out for forming a socket(41), a first extruder feeding an inner nozzle(21) and a second extruder feeding an outer nozzle(22). The extrusion speed of one or both extruders is varied by switches(50,51,56,57) operated as the socket cut-out moves over one of the nozzles.