Helical pipe lock seam

Abstract

A pipe formed by a helically coiled strip of ductile sheet metal of uniform width connected along its longitudinally extending edges by a seam, which seam is formed by the marginal portions of the strip along said edges. Said marginal portions are formed with parallel return bends extending longitudinally of said edges, which bends are in adjacent opposed relation and which marginal portions include flattened loops extending to the same side of said pipe from approximately one of said bends to the other with one of said loops enclosed within the other, and the said marginal portions are bent along a line spaced from and parallel with said bends to generally V-shape in cross sectional contour transversely of said marginal portions, whereby said bends are positioned in one of the sides of said V spaced from its apex with flattened portions of said loops extending across and to opposite sides of said apex.

Dependencies are inferred from the claim text.