Balanced flow extrusion crosshead and die assembly

Abstract

The apparatus includes a crosshead and die assembly for the extrusion of polymeric resins and the like into tubular shapes, for example, of single or multiple layers. A crosshead body has a side fed resin inlet orifice which communicates with a first resin distribution channel extending 180.degree. around an inner mandrel, the first channels having gate orifices at the ends thereof. The gate orifices feed heated resin to a second resin distribution channel which extends 360.degree. around the mandrel and communicates with a first restrictive annular opening which also extends 360.degree. around the mandrel. The first restrictive annular opening feeds resin to a third resin distribution channel which also is formed 360.degree. around the mandrel. A second restrictive annular opening communicates with the third resin distribution channel 360.degree. around its circumference and feeds the molten resin or the like to an annular opening formed between the inner mandrel and the crosshead body. The resin then moves to a die land and is extruded therethrough. The plurality of ring-shaped resin distribution channels and restrictive annular openings provide balanced resin pressure and laminar flow around the inner mandrel. One or more abutting pairs of intermediate distribution plates having the above-described ring-shaped resin distribution channels and restrictive annular openings machined therein may be added to the crosshead body tooling in order to provide one or more additional uniform layers of resin or the like to the extruded product.