Freeze-resistant plastic pipe and method for its manufacture
OwnerNorman L. Francisinventor
Life of this patent
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Abstract
A plastic pipe with a hard outer shell lined with an inner shell of soft resilient plastic foam with a smooth central axial passageway adapted to be a conduit for liquid. A method of manufacturing this pipe which comprises simultaneously extruding the material for the outer shell and the foamable material for the inner shell into a pipe forming die.
Claims11
A pipe having a smooth, rigid hard outer shell, a smooth flexible inner shell spaced inwardly from said outer shell, and a flexible closed-cell foam material filling the space between said outer and inner shells;
- said flexible inner shell being sufficiently elastic to expand the internal volume of said pipe about 10% while maintaining a smooth continuous surface.
A pipe consisting of a hard outer shell of polyvinyl chloride and bonded thereto a soft flexible inner core of foamed polyethylene having a smooth central passageway substantially free of surface irregularities adapted to conduct liquid with a minimum of frictional losses, said core being capable of expanding to provide about 10% increased volume in said passageway without substantially modifying the smoothness of said passageway.
A process for preparing a pipe having a smooth hard outer shell spaced apart from a smooth flexible elastic, expandable, continuous inner shell and separated therefrom by a mass of foam material, said process comprising extruding a first tubular structure of polyvinyl chloride and simultaneously extruding inside of said first tubular structure, and in contact therewith, a second tubular structure of a foamed polyolefin having a smooth continuous interior cylindrical hydrodynamically acceptable surface.
Dependencies are inferred from the claim text.