Plastic lockseam tubing and method for making
AssigneeUnited McGill Corporation
InventorsFrederic G. Hunt, Robert D. McVay, deceased
Life of this patent
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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).
Claims20
A plastic lock seam spiral tube assembly comprising:
- a strip made from polyethylene material, formed as an essentially planar elongate strip of constant with, said width being at least several inches, having a thickness greater than 1 mm., having straight edges along its length and with formations along each side edge of said planar strip, disposed essentially normal to the planar aspect of such strip and both formations projecting from the same side of said strip;
- one of said formations constituting a stem strip integral with the planar strip and including an integral substantially circular bead at its terminal edge, said stem strip being inset from the associated edge of said planar strip to define a short planar edge flange substantially the thickness of and on said strip;
- the other of said formations constituting a lateral flange integral and parallel with the planar strip and stepped offset in the direction of said formation's projection a distance substantially equal to the thickness of said planar strip and integral with the end of said step flange, said other formation providing a C-shaped channel with internal channel formation complementing the shape of said bead and with the dimension between the legs of the C-shaped formation substantially equal to the thickness across said bead stem;
- said strip being disposed in a helical spiral configuration so that said projected bead is disposed in said C-shaped channel and the legs of said C-shaped channel encompass said bead and engage said bead stem strip to interlock the edges of said planar strip in a helical tube and said short planar edge flange is disposed in and along the step of said stepped lateral flange on the other of said edge formations;
- whereby one of the inner or outer surfaces of the helical spiral tube is essentially laminar along the length of the tube and the other of said surfaces has a helical projection formation resulting from the channel shaped formation along its length.
A spiral plastic tube made from a strip of plastic material with longitudinal edge constructions providing a bead formation along one edge of the strip and a complementarily shaped groove formation along the opposite edge of the strip, which can enable an interlocked helical seam, in the spiral tube, wherein said strip of plastic material consists solely of high-molecular-weight high density polyethylene.
For use in making thin plastic lock seam spiral tube:
- a strip made from polyethylene material formed as an essentially planar elongate strip of constant width, said width being at least several inches, having a thickness greater than 1 mm., having straight edges along its length and with formations along each side edge of said planar strip, disposed essentially normal to the planar aspect of such strip and both formations projecting from the same side of said strip;
- one of said formations constituting a stem strip integral with the planar strip and including an integral substantially circular bead at its terminal edge, said stem strip being inset from the associated edge of said planar strip to define a short planar edge flange substantially the thickness of and on said strip;
- the other of said formations constituting a lateral flange integral and parallel with the planar strip and stepped offset in the direction of said formation's projection a distance substantially equal to the thickness of said planar strip and integral with the end of said step flange, said other formation providing a C-shaped channel with internal channel formation complementing the shape of said bead and with the dimension between the legs of said C-shaped formation substantially equal to the thickness across said bead stem.
Dependencies are inferred from the claim text.