Wound and themoformed element and method of manufacturing same

Abstract

A heating element for heating a flexible intravenous tube includes a resistance heating wire having a pair of terminal ends encapsulated within an electrically insulating polymeric layer. The polymeric layer and the resistance heating wire are formed into a plurality of turns defining a coil having a central axis. Each turn of the coil is independently elastically expandable to surround a portion of the flexible intravenous tube when the intravenous tube is disposed axially through the coil such that the coil conforms to the shape of the flexible intravenous tube.

What is claimed:  
     
         1 . A heating element for heating a flexible intravenous tube, said heating element comprising: 
 a resistance heating wire having a pair of terminal ends, said resistance heating wire encapsulated within an electrically insulating polymeric layer, said polymeric layer and said resistance heating wire being formed into a plurality of turns defining a coil having a central axis, wherein each of said turns is independently elastically expandable to surround a portion of said intravenous tube when said intravenous tube is disposed axially through said coil such that said coil conforms to the shape of said flexible intravenous tube.    
     
     
         2 . The heating element of  claim 1 , wherein said coil includes at least two sets of interconnected parallel turns.  
     
     
         3 . The heating element of  claim 2 , wherein said coil includes two sets of interconnected parallel turns, each of said sets terminating at a different one of said terminal ends.  
     
     
         4 . The heating element of  claim 1 , wherein said polymeric layer is a tubular thermoplastic sheath and said resistance heating wire is disposed axially through said tubular thermoplastic sheath.  
     
     
         5 . The heating element of  claim 1 , wherein said polymeric layer is extruded over said resistance heating wire.  
     
     
         6 . The heating element of  claim 5 , wherein said heating element includes a plurality of resistance heating wires connected in series.  
     
     
         7 . The heating element of  claim 5 , wherein said heating element includes a plurality of resistance heating wires connected in parallel.  
     
     
         8 . The heating element of  claim 1 , further comprising a flexible intravenous tube disposed axially through said coil.  
     
     
         9 . A method of manufacturing a heating element for a flexible intravenous tube, comprising the steps of: 
 providing a resistance heating wire having a pair of terminal ends;    surrounding said resistance heating wire with an insulating polymeric layer; and    forming said polymeric layer and said resistance heating wire into a plurality of turns defining a coil having a central axis, wherein each of said turns is independently elastically expandable to surround a portion of said intravenous tube when said intravenous tube is disposed axially through said coil such that said coil conforms to the shape of said flexible intravenous tube.    
     
     
         10 . The method of  claim 9 , wherein the step of forming said polymeric layer and said resistance heating wire into a plurality of turns includes the steps of wrapping said polymeric layer and said resistance heating wire around a mandrel, heating said polymeric layer and said resistance heating wire, and allowing said thermoplastic sheath to cool to maintain said coil shape.  
     
     
         11 . The method of  claim 9 , wherein said polymeric layer is a tubular thermoplastic sheath and the step of surrounding said resistance heating wire includes the step of disposing said resistance heating wire axially through said tubular thermoplastic sheath.  
     
     
         12 . The method of  claim 9 , wherein the step of surrounding said resistance heating wire includes the step of extruding said polymeric layer over said resistance heating wire.  
     
     
         13 . The method of  claim 12 , wherein the step of surrounding said resistance heating wire includes the step of extruding said polymeric layer over a plurality of resistance heating wires.  
     
     
         14 . The method of  claim 13 , further comprising the step of connecting said plurality of resistance heating wires in parallel.  
     
     
         15 . The method of  claim 13 , further comprising the step of connecting said plurality of resistance heating wires in series.  
     
     
         16 . The method of  claim 9 , where in the step of forming said polymeric layer and said resistance heating wire into a plurality of turns includes the step of forming said polymeric layer and said resistance heating wire into at least two sets of interconnected parallel turns.  
     
     
         17 . An expandable heating element, comprising: 
 a resistance heating material surrounded by an electrically insulating polymeric layer, said polymeric layer and said resistance heating material being formed into a plurality of turns defining a coil having an original diameter and a central axis, wherein a plurality of said turns are independently elastically expandable to a diameter greater than the original diameter of said coil to surround a cylindrical body disposed axially through said coil, at least a portion of said cylindrical body having a diameter greater than the original diameter of said coil.    
     
     
         18 . The heating element of  claim 17 , wherein said resistance heating material includes a resistance heating wire having a pair of terminal ends.  
     
     
         19 . The heating element of  claim 18 , wherein said resistance heating wire is laminated between two sheets of thermoplastic.  
     
     
         20 . The heating element of  claim 18 , wherein said polymeric layer is extruded over said resistance heating wire.  
     
     
         21 . The heating element of  claim 20 , wherein said polymeric layer comprises a PTFE film.  
     
     
         22 . The heating element of  claim 17 , wherein said resistance heating material includes a resistance heating wire sewn to a supporting substrate.  
     
     
         23 . The heating element of  claim 17 , wherein said electrically insulating polymeric layer includes a thermoplastic elastomer material, the heating element further comprising a reinforcing substrate fused with said electrically insulating polymeric layer.  
     
     
         24 . A method of manufacturing a flexible heating element, comprising the steps of: 
 providing a resistance heating material;    surrounding said resistance heating material with an electrically insulating polymeric layer; and    forming said polymeric layer and said resistance heating material into a plurality of turns defining a coil having a central axis and an original diameter, wherein a plurality of said turns are independently elastically expandable to a diameter greater than the original diameter of said coil.    
     
     
         25 . The method of  claim 24 , wherein the steps of surrounding said resistance heating material includes the steps of providing a first and second thermoplastic sheets and laminating said resistance heating material between said first and second thermoplastic sheets.  
     
     
         26 . The method of  claim 25 , wherein said forming step includes the steps of wrapping said polymeric layer and said resistance heating material around a mandrel, heating said polymeric layer and said resistance heating material, and allowing said polymeric layer and said resistance heating material to cool to maintain said coil shape.  
     
     
         27 . The method of  claim 26 , wherein said resistance heating material includes a resistance heating wire having a pair of terminal ends.  
     
     
         28 . The method of  claim 27 , wherein said resistance heating wire is sewn to a supporting substrate.  
     
     
         29 . The method of  claim 24 , wherein the step of surrounding said resistance heating material includes the step of extruding said polymeric layer over said resistance heating material.  
     
     
         30 . The method of  claim 29 , wherein the step of forming said polymeric layer and said resistance heating material into a plurality of turns includes the steps of wrapping said polymeric layer and said resistance heating material around a mandrel, heating said polymeric layer and said resistance heating material, and allowing said polymeric layer and said resistance heating material to cool to maintain said coil shape.  
     
     
         31 . The method of claim  30 , wherein said resistance heating material includes at least one resistance heating wire.  
     
     
         32 . The method of  claim 24 , wherein the step of forming said polymeric layer and said resistance heating material into a plurality of turns includes the steps of wrapping said polymeric layer and said resistance heating material around a mandrel, heating said polymeric layer and said resistance heating material, and allowing said polymeric layer and said resistance heating material to cool to maintain said coil shape.