Manufacture of helically corrugated conduit

摘要

This invention concerns the manufacture of helically corrugated conduit having at least a portion of its length corrugated in the form of at least one helix. The method includes the driving of a smooth walled tube into a forming head having forming wheels which engage the outside of the tube and the wheels are at an angle relative to the longitudinal axis of the tube. The forming wheels form the helical spiral as part of a cold rolled forming process. More than one helical spiral can be formed simultaneously using a multiplicity of forming wheels.