Patent ID: 6119887
Filing Date: 2000-09-19
Classification: B29C,B29D,B29K,B29L,B65D

Abstract:
A method for making a double wall tank for the storage of liquids comprising the steps of:providing a generally rigid, cylindrical inner tank having elongated cylindrical sidewall portion, two generally opposed closed end portions generally transverse to said sidewall portion, and a central axis extending longitudinally through said end portions, with each said inner tank end portion having a perimeter edge and a predetermined outer diameter;attaching a first outer end portion of a generally rigid synthetic resin material to one of said inner tank end portions, said first outer end portion having a predetermined diameter at least generally equal to said diameter of said one end portion of said inner tank, and said first outer end portion having a perimeter edge positioned adjacent said perimeter edge of said one end portion of said inner tank to define a first shoulder;helically extruding an outer sheath of a plurality of layers of a first molten thermoplastic synthetic resin material around said inner tank sidewall portion while preventing bonding between a substantial portion of said first synthetic resin material layers and said inner tank, with a first additional plurality of layers of said first molten synthetic resin material being extruded around said inner tank proximal said first shoulder, such that at least a portion of said first molten synthetic resin material fuses to said first outer end portion proximal said first shoulder, whereby a seal is formed between the outer sheath and the first outer end portion proximal the first outer end portion perimeter edge.