APPARATUS FOR PRODUCING DOUBLE-WALLED HELICALLY WOUND THERMOPLASTIC PIPE

摘要

Helically wound thermoplastic pipe is produced by extruding a band of thermoplastic. The extruded band is formed into corrugations and helically wound into a tube. A second extruder extends through a first extruder and has its die (32) located downstream from the first extruder die to extrude the second band of thermoplastics inside of the corrugated tube. The second band forms a non-corrugated tube fused to the inside of the corrugated tube.