Image Number 2 for United States Patent #5035596.
A coextrusion head for the continuous production of multilayer tubular structures having three to seven-layers. The basic tubular structure produced has a central barrier layer and symmetrically arranged thereabout, layers of adhesive agent, regenerated and/or carrier materials. The upper portion of the coextrusion head contains a multipiece jacket that defines annular passages in which the layers of the structure are formed. The lower portion contains the nozzle from which the tubular structure is extruded. Between the upper and lower portions are placed a core ring and a nozzle ring which together provide the transport channel between the annular passageway in which the layers are joined and the inlet to the nozzle. Each ring has two alternative configurations. One configuration permits movement of the layered material in the annular passageway where the layers are joined and the second configuration precludes such movement. By the proper combination of the jacket in the upper portion of the coextrusion head and core and nozzle rings, tubular structures having a center barrier layer and symmetrical inner and outer layers, an inner barrier layer with outer layers of other materials, or an outer barrier layer with inner layers of other materials may be formed. Additional flexibility in the formation of the tubular structures may be obtained by the manner in which the extruders are attached to the coextrusion head.