Method of making an orbital friction fusion a welded joint in thermoplastic strap with differential pressure

A method for making a welded joint between first and second lengths of a thermoplastic strap which are disposed in an overlapping, face-to-face relationship with respect to each other at a location at which said welded joint is to be formed, comprising the steps of:

• forcing said strap lengths into face-to-face contact with each other under above-ambient pressure conditions along an interface comprising a central region and a peripheral region;
• increasing the temperature of said strap lengths along said interface so as to melt at least a part of the thickness of each one of said strap lengths at said interface whereby said melted parts of said strap lengths can merge with each other so as to define said welded joint when said merged melted parts of said strap lengths resolidify;
• and
• releasing said above-ambient pressure conditions firstly within said peripheral region of said interface and subsequently within said central region of said interface whereby said merged melted parts of said strap lengths along said interface comprising said central and peripheral regions are permitted to resolidify so as to form said welded joint.

A method for making a welded joint between first and second lengths of a thermoplastic strap which are disposed in an overlapping, face-to-face relationship with respect to each other at a location at which said welded joint is to be formed, comprising the steps of:

• forcing said strap lengths into face-to-face contact with each other under above-ambient pressure conditions along an interface comprising a central region and a peripheral region;
• increasing the temperature of said strap lengths along said interface so as to melt at least a part of the thickness of each one of said strap lengths at said interface whereby said melted parts of said strap lengths can merge with each other so as to define said welded joint when said merged melted parts of said strap lengths resolidify;
• and
• releasing said above-ambient pressure conditions firstly within said peripheral region of said interface while maintaining said above-ambient pressure conditions within said central region of said interface, and subsequently releasing said above-ambient pressure conditions within said central region of said interface whereby said merged melted parts of said strap lengths along said interface comprising said central and peripheral regions are permitted to resolidify so as to form said welded joint which is characterized by the inclusion of a plurality of closed cavities within said peripheral region of said welded joint while said central region of said welded joint is substantially free of said cavities.