Coextrusion head

US4838778A · kind A · utility

Inventors

• Rudolf Becker · Ingolstadt, DE
• Wilhelm Neubauer · Murr, DE
• Hans-Joergen Beyer · Rottenburg am Neckar, DE
• Harald Pohl · Erbach, DE

Key dates

• Filing date: Dec 23, 1987
• Grant date: Jun 13, 1989
• Expiry date: Dec 23, 2007

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B29C48/32
• WIPO field: Other special machines
• WIPO sector: Mechanical engineering

Abstract

A coextrusion head for the continuous production of laminated tubes to be used as parisons in blow molding. The tubes consist of a plurality of layers of synthetic resins. The synthetic resin layers include one or more supporting layers, usually a barrier layer, and adhesive layers as necessary. The layers are brought together by axial, annular feed passageways within the coextrusion head prior to the laminated tube being extruded through a nozzle in the head. Frequently one layer, generally the barrier layer, has different flow characteristics than those of the other layers, whereupon structural defects can arise in the formed tube. The apparatus described forestalls such structural defects by feeding the various layers into confluence in a manner that precludes, or sufficiently minimizes, the time layers having differing flow characteristics have contact with feed passageway walls while in confluence. As a result, shear stresses within or between the individual layers is avoided and the tube so produced is free of structural defects.