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

A thin-walled, flexible and collapse-resistant plastic tubing having a wall with a substantially smooth bore for communicating fluid, and a helical radially outwardly extending support bead carried upon said wall, the tubing including an electrical resistance conductor embedded within said support bead, which resistance conductor has a comparatively conductive heat transfer relationship to fluid within said bore and a less conductive and more insulative heat transfer relationship with ambient conditions outside of said tubing wall, said tubing comprising:

• a flexible tubing wall formed of elongate thermoplastic ribbon having opposite side edges, said ribbon being helically wrapped on itself to overlap said opposite side edges a certain amount forming a helical lap joint whereat opposite side edge portions of said ribbon are heat-bonded to one another forming a thin-walled elongate tubular body;
• an elongate electrical resistance heating conductor disposed helically around and along the length of said flexible tubing wall atop said elongate thermoplastic ribbon and adjacent to an outer one of said opposite side edges;
• and
• an elongate thermoplastic support bead having a thickness in the radial direction of said tubing which is substantially greater than said ribbon and being disposed helically around and along said flexible tubing wall atop both said helical lap joint and said electrical resistance heating conductor and being heatbonded to said tubing wall to form a unitary body therewith and encapsulating said electrical resistance heating conductor;
• whereby said electrical resistance heating conductor is insulated from said fluid by only the single thickness of said elongate thermoplastic ribbon forming said tubing wall but is insulated from ambient conditions by said support bead, and said support bead provides collapse-resistance to said tubing wall.