Conduit and method of forming

Abstract

A thin ribbon spirally wound polymer conduit and method of forming, wherein a helical reinforcing bead is interposed adjacent overlapping layers of ribbon. Further, a method of continuously forming spirally wound conduit wherein a sacrificial layer, preferably having a different base polymer to that of the conduit, is first applied to the former before the conduit is formed overtop.

1 . A method of continuously forming conduit comprising:
 continuously applying at least one thin film ribbon, each having “leading” and “trailing” lateral edges, spirally around a former rotating and advancing said conduit, with the leading edge of each turn of ribbon overlapping the trailing edge of a previous turn of ribbon on the former and the trailing edge of each turn under lapping the leading edge of a succeeding turn, while,   in advance of said overlapping of said turns, applying a bead of molten plastic, having “leading” and “trailing” edges, adjacent the exposed trailing edge of the most recently applied turn on said former, such that said bead is interposed between the overlapping and under lapping portions, said bead when cooled forming a helical reinforcing bead, and wherein   said overlapping portion is supple, at least laterally, and conforms around the contour of said molten bead as it is applied thereto, such that said overlapping portion continuously contacts said bead and bonds along said conforming portion; and said overlapping portion of said ribbon meets or substantially meets said trailing edge of said under lapping portion of said ribbon, at the trailing edge of said bead.   
     
     
         2 . A method of continuously forming conduit as claimed in  claim 1 , wherein said conduit is reinforced against crushing, and said reinforcement consists of said polymer bead. 
     
     
         3 . A method of continuously forming conduit as claimed in  claim 2 , wherein said leading edge of said over lapping ribbon meets or substantially meets said under lapping ribbon at the leading edge of said bead. 
     
     
         4 . A method of continuously forming conduit as claimed in  claim 2 , wherein said method further comprises the steps of,
 applying one or more heating wires to the exposed trailing edge of the ribbon prior to applying the bead, such that the bead encapsulates the said one or more heating wires onto the said trailing edge.   
     
     
         5 . A method of continuously forming conduit as claimed in  claim 1 , wherein said leading edge of said over lapping ribbon meets or substantially meets said under lapping ribbon at the leading edge of said bead. 
     
     
         6 . A method of continuously forming conduit as claimed in  claim 1 , wherein said thin film ribbon has a thickness of less than 50 microns. 
     
     
         7 . A method of continuously forming conduit as claimed in  claim 1 , wherein said ribbon is a breathable plastic material. 
     
     
         8 . A method of continuously forming conduit as claimed in  claim 7 , wherein said ribbon is a laminate where a layer of breathable plastic material is laminated to a reinforcing layer which also allows the passage of water vapour. 
     
     
         9 . A method of continuously forming conduit as claimed in  claim 1 , wherein said method further comprises the steps of,
 applying one or more heating wires to the exposed trailing edge of the ribbon prior to applying the bead, such that the bead encapsulates the said one or more heating wires onto the said trailing edge.   
     
     
         10 . A method of continuously forming conduit as claimed in  claim 1 , where the former includes a plurality of rotating rods spaced about an axis and acting to support and advance the conduit during forming, further comprising:
 first applying a sacrificial layer of thin plastic directly around said former, before said conduit is formed on said former over top of said sacrificial layer, and   subsequent to forming said conduit, removing said sacrificial layer from inside said thin walled conduit after cooling.   
     
     
         11 . A method of continuously forming conduit as claimed in  claim 10 , wherein said sacrificial layer is a thin ribbon having “leading” and “trailing” lateral edges, and said sacrificial layer is spirally wound around said former in a continuous fashion, with the leading edge of each turn of said sacrificial layer overlapping the trailing edge of a previous turn of said sacrificial layer on the former and the trailing edge of each turn under lapping the leading edge of a succeeding turn. 
     
     
         12 . A method of continuously forming conduit as claimed in  claim 10 , wherein said sacrificial layer is of a material having a different base polymer than that of said conduit, such that no substantial adhesion occurs when adjacent layers of said sacrificial layer and said conduit are heated.