Apparatus and method for making flexible tubing with helically wound heating conductor

A method for making a helically wound, flexible and collapse resistant seamless plastic tubing comprising the steps of:

• forming an elongate ribbon of molten thermoplastic having opposite side edges, helically wrapping said elongate ribbon so that said opposite side edges overlap a certain distance to form a helical lap joint at which one of said opposite side edges is outwardly disposed, and simultaneously heat-bonding said ribbon to itself to form an elongate tubular body, using a single thickness of said elongate ribbon to define a wall for said tubing extending substantially between said helical lap joints;
• laying an elongate, electrical heating conductor helically around and along said tubular body adjacent to said outwardly disposed one of said opposite side edges and atop said wall which is only a single thickness of said ribbon;
• forming an elongate support bead of thermoplastic material having a thickness and insulating value which is substantially greater than said ribbon;
• helically wrapping said support bead around and along said tubular body atop both said helical lap joint and said electrical conductor and simultaneously heat-bonding said support bead with said ribbon to form a unitary body including said ribbon and said bead with said electrical conductor embedded therebetween;
• and
• using said support bead to both support said tubular body against collapse and to insulate said electrical heating conductor from ambient while conducting heat from said electrical heating conductor inwardly of said tubing adjacent to said helical lap joint through said wall thereof which is only a single thickness of said ribbon.