Patent ID: 7404308

Claim:
A pipe manufacturing apparatus, comprising: (a) a decoiler unit for receiving a coil formed by a rolled metal sheet, the decoiler unit permitting the coil to rotate; (b) a corrugating line for drawing the metal sheet off of the coil and placing corrugations in the metal sheet to produce a corrugated metal strip, the corrugating line comprising: (i) a first tooling stand configured to receive flat sheet material and to produce a first wave-shaped cross-sectional profile in the sheet, where upper and lower crests of the first wave-shaped cross-sectional profile are generally curved and lack any flats or small radius bends; (ii) a second tooling stand downstream of the first tooling stand and configured to modify the first wave-shaped cross-sectional profile so as to produce a second wave-shaped cross-sectional profile, where upper and lower crests of the second wave-shaped cross-sectional profile are generally curved and lack any flats or small radius bends, and a height of the second wave-shaped cross-sectional profile is greater than a height of the first wave-shaped cross-sectional profile; and (iii) multiple tooling stands downstream of the second tooling stand for completing formation of multiple box-shaped corrugations in the metal sheet to form a corrugated metal strip in which the spacing between box-shaped corrugations along the width of the strip is substantially greater than the box-shaped corrugation width, each box-shaped corrugation including a generally flat bottom portion and upwardly extending parallel side portions; (c) a forming head positioned to receive the corrugated metal strip and to spiral the corrugated metal strip into a pipe-shape.