Flexible metal conduit and method of making the same

Abstract From the Canadian patent

A flexible metal conduit and fabrication method where a thin metal ribbon is arranged in a helix about a central axis. The ribbon defines helically extending corrugated inwardly and outwardly facing conduit surfaces formed by alternating ridges and valleys extending parallel to the ribbon edges. Ribbon edge locking structure secures abutting ribbon convolutions together and comprises first and second confronting parallel ribbon edge flanges extending at least a substantiallength of the ribbon. The flanges are lapped and tightly rolled together to form a two ply spirally curved wall defining a tube whose central core has a generally circular cross sectional shape. The tube is disposed …