Abstract: An extrusion assembly includes a stationary housing section, and an outer die and mandrel for defining an annular passageway centered about an axis. The outer die and mandrel are held stationary against rotational motion about the axis. A rotor is rotationally supported on a shaft projecting into the annular passageway along the axis within the housing, for rotational motion about the axis. The rotor includes a melt channel for rotationally conveying an extrusion to the annular passageway, so as to form a helically-wound conduit that advances linearly through the annular passageway. A gear train is operative between the stationary housing, the rotor and the shaft, to hold the shaft stationary relative to the stationary housing upon rotation of the rotor.

Abstract: A force-transmitting joint formed between two pipe sections is provided that is particularly suited for an extruded, plastic pipe having a variable wall thickness. The joint has a smooth outer surface and a constant gap in which a sealing member is retained. The pipe section has an outer wall including an outer surface and an inner surface with a variable wall thickness defined therebetween. A first end of the pipe section includes a first joint member comprising a first support surface having a constant width. The first joint member further comprises an outwardly extending sealing leg having a variable width. A second end of the pipe includes a second joint member comprising a second support surface having a constant width which is less than the width of the first support surface. The second joint member further comprises a recess having a variable thickness. An annular sealing member is assembled onto the sealing leg.

Abstract: A pipe joint and coupling construction particularly suited for joining large diameter plastic pipe as used in sewer relining. The construction comprises first and second sections of cylindrical pipe having axially aligned opposed end walls with a continuous groove formed in each end wall. The groove in each end wall is axially aligned with the groove in the opposed end wall and cooperates therewith to form a gasket receiving chamber. The coupling member is adapted to be mounted in the gasket receiving chamber for sealingly joining the pipe sections. It comprises a rigid annular core ring for mounting in the chamber to extend axially into each of the axially aligned grooves. A resilient compressible elastomeric covering is positioned over the core ring and carried circumferentially continuous radially extending protrusions which are sized to be sealingly compressed between the core ring and the side walls of the grooves.

Abstract: A method of forming a chamfered and sealed end on a spiral wound plastic pipe of the type including at least a pair of radially spaced circumferential side walls connected by an intermediate wall which joins generally radially between the side walls and extends in a helical path axially of the pipe. The method includes determining the desired axial length of the chamfer and removing the intermediate wall which lies between the side walls axially inwardly of the end of the pipe a distance substantially equal to the desired length to define an outwardly open channel between the side walls. Thereafter one of the side walls is permanently deflected to bring it substantially into engagement with the end of the other of the side walls circumferentially about the pipe to thereby form a chamfer on the end of the pipe.