MANUFACTURE OF HELICALLY CORRUGATED CONDUIT

摘要

This invention concerns the manufacture of helically corrugated conduit havi ng at least a portion of its length corrugated in the form of at least one helix. The method includes the driving of a smoo th 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 form- ing wheels form the helical spiral as part of a cold rolled forming process. More than one helical spiral can be formed simultane- ously using a multiplicity of forming wheels.