Patent ID: 6840545
Filing Date: 2005-01-11
Classification: B29C,F16L,Y10T

Abstract:
1. A method for producing a thermowelded connection between two pipe members, said pipe members including opposed flanges comprised of a melt processable thermoplastic material, comprising: positioning an annular weld insert between the plastic flanges of each of two opposing pipe sections, such that the weld insert is positioned between and against abutting surfaces of the flanges of the two opposed pipe members, said weld insert formed of a rigid material chemically compatible with the thermoplastic material of said flanges and having an inner and an outer circumference; urging the plastic flanges of the pipe sections into contact with each other and with the weld insert in between by applying and tightening a coupling about the abutting flanges of the opposed pipe members; passing electrical current through a resistance heating element symmetrically disposed about the inner circumference of the weld insert to produce sufficient heat to raise the temperature of the thermoplastic material of the opposed flanges adjacent and radially inwardly of the heating element to at least the melting point of the thermoplastic material; maintaining pressure longitudinally along the axes of the two opposed pipe members while heating the weld insert until the insert becomes embedded into the melting thermoplastic material; removing the electrical current once the weld insert is bonded with the thermoplastic material; and allowing the thermoplastic material to cool below its melting temperature in order to form a thermowelded flange connection.