Method of making a double-walled flexible tubing product with helical support bead and heating conductor

A continuous single-process method of making a double-walled flexible and collapse-resistant, electrically-heated, insulative plastic tubing having a substantially smooth bore provided by an inner one of two radially spaced apart integral walls trapping a dead-air space therebetween, and an integral helical support bead disposed between the two walls, said method comprising steps of:

• providing a first melt-extrudate in the form of an elongate thermoplastic first ribbon having opposite marginal side edge portions;
• simultaneously forming an elongate tubular body by winding said first ribbon on itself with said opposite marginal side edge portions thereof overlapped and interbonding to form a helical lap joint;
• simultaneously providing at least one elongate electrical resistance heating conductor;
• simultaneously wrapping said electrical resistance conductor helically around and along said elongate tubular body at said lap joint;
• simultaneously providing a second melt-extrudate in the form of a thermoplastic support bead;
• simultaneously winding said support bead helically around and along said elongate tubular body atop said helical lap joint while heat-bonding to said elongate tubular body and encapsulating said electrical resistance heating conductor;
• simultaneously providing a third melt-extrudate in the form of an elongate thermoplastic second ribbon, and winding said second ribbon helically around and along said elongate tubular body spanning from one wrap of said helical support bead to the next, while bowing radially outwardly, and with opposite marginal side edge portions thereof overlapping and inter-bonding to both one another and said support bead so that said first ribbon, said second ribbon, said helical support bead, and said electrical resistance heating conductor all define a common helix angle relative to said tubing;
• and
• cooling said tubing;
• whereby upon the tubing being bent, the flexibility of the tubing is improved by a radially outward bowing of the second ribbon at the inside of such bend.

A method of making a double-walled flexible and collapse-resistant insulative plastic tubing, said method comprising steps of:

• providing an elongate thermoplastic first ribbon and an elongate thermoplastic second ribbon each having respective opposite marginal side edge portions;
• forming an elongate tubular body by winding said first ribbon on itself with opposite marginal side edge portions thereof overlapping and interbonding to form a helical lap joint;
• providing a thermoplastic support bead and winding said support bead helically around and along said elongate tubular body atop said helical lap joint while simultaneously heat-bonding said support bead to said elongate tubular body;
• winding said second ribbon helically around and along said elongate tubular body while spanning said second ribbon from one wrap of said helical support bead to the next, bowing said second ribbon radially outwardly, and heat-bonding said second ribbon at overlapped opposite marginal side edge portions thereof both to itself and to said support bead;
• and cooling said tubing while retaining said outward bow of said second ribbon in said span thereof between wraps of said support bead.

A method of making a double-walled flexible and collapse-resistant, electrically-heated, insulative plastic tubing having a substantially smooth bore provided by an inner one of two radially spaced apart integral walls trapping a dead-air space therebetween, and an integral helical support bead disposed between said two walls, said method comprising steps of:

• providing an elongate molten thermoplastic first ribbon having opposite marginal side edge portions;
• forming an elongate tubular body by winding said first ribbon on itself with said opposite marginal side edge portions thereof overlapping and interbonding to form a helical lap joint;
• providing at least one elongate electrical resistance heating conductor;
• wrapping said at least one electrical resistance conductor helically around and along said elongate tubular body at said lap joint;
• providing an elongate molten thermoplastic support bead;
• winding said support bead helically around and along said elongate tubular body atop said helical lap joint while said support bead heat-bonds to said elongate tubular body and encapsulates said electrical resistance heating conductor;
• providing an elongate molten thermoplastic second ribbon, and winding said second ribbon helically around and along said elongate tubular body while spanning said second ribbon from one wrap of said helical support bead to the next, bowing said second ribbon radially outwardly, and interbonding opposite marginal side edge portions of said second ribbon to one another and to said support bead;
• and cooling said tubing while retaining said bowing of said second ribbon in the span thereof between adjacent wraps of said support bead.