Abstract: A thin-walled large diameter spiral plastic tube with interlocking helical seams made from a strip of polyethylene material. The strip of plastic has a thin configuration with edge constructions providing a bead formation along one edge and a groove formation along the opposite edge, which can enable an interlocked helical seam, in the spiral tube. The strip is fed into a special spiral pipe making machine for plastics which winds and interlocks the edges of the strip. Such tubing is used for ducts and pipes and, filled with expanded polystyrene beads can be used very advantageously as flotation devices. The plastic used in the strips is polyethylene, including medium and high density polyethylenes with high molecular weight (HMW).

Abstract: A method and tooling for making angle ring flanges from relatively light gauge sheet metal. The method starts with a flat strip of sheet metal from which two angle ring flanges are formed. The strip is rolled and butt welded into a band, the butt weld is broached on both surfaces at the weld line to the thickness of the sheet metal band. The band is placed in a roll forming machine between a set of two forming rolls which rotate and merge to rotate the band and form it into a ring of channel section with outward facing channel legs at 90.degree. to the channel base. One roll is male and pushes the center half of the band down into the female roll and the outer quarters of the band are forced into the clearance between the male and female forming rolls to form the standing legs or flanges of the finished channel section. The male roll has an annular central groove and the female roll includes a shearing cutter disc which is complementary to the annular groove.