Patent ID: 6299803
Filing Date: 2001-10-09
Classification: B29C,B29K,F16L

Abstract:
A method for producing a temporarily deformed pipe liner from extruded thermoplastic round pipe of tubular cross-section with an inner and outer surface for insertion into a conduit with an inner and outer surface and reformation of the deformed pipe liner to said extruded tubular cross-section without inducing heat transfer stresses, comprised of the following steps:a) Annealing existing axial and radial stresses in the extruded thermoplastic round pipe induced during the extrusion process and induced during butt-fuse bonding of segments of said round pipe to obtain the desired length of pipe liner;b) After annealing, collapsing the round pipe at ambient temperature into a flattened ribbon shape with top and bottom sides by means of localized internal vacuum;c) After collapsing the round pipe into a flattened ribbon shape, folding the bottom side of the flattened ribbon shape along a plane of bilateral symmetry thereby creating an inner fold within the top side of the flattened ribbon shape, and reducing the cross-sectional configuration of the flattened ribbon shape into a deformed ""U"" section, while maintaining an internal vacuum to lock the pipe in a deformed configuration;d) Injecting a bead of hydrophilic material into the inner fold of the deformed ""U"" cross-section;e) Maintaining the internal vacuum throughout deformation of the round pipe including packaging, thereby further reducing the cross-section;f) Coiling the deformed pipe liner while maintaining the internal vacuum to axially pre-stress the deformed section to obtain a smaller bending radius without buckling the deformed pipe liner for shipping to a job site;g) At the job site, drawing the deformed pipe liner through a conduit to be repaired;h) unfolding the deformed pipe liner in the conduit by releasing the internal vacuum.