Method for introducing an internal helical formation into a flexible tubular material

Abstract

There is disclosed a method for introducing a helical formation ( 11 ) into a flexible tubular material ( 12 ). The material ( 12 ) is supported together with a surrounding helical former ( 13 ) so as to deform the material ( 12 ) to have a helical indentation ( 11 ) corresponding to the shape of the former ( 13 ). The material ( 12 ) is then set in that configuration and the former ( 13 ) is removed.

We claim:  
     
         1 . A method for introducing an internal helical formation into a flexible tubular material, the method comprising supporting the material on a mandrel having a groove, placing a helical former corresponding to the groove around the material so as to deform the material to have an internal helical formation corresponding to the shape of the groove, setting the material in that configuration, and removing the former and the mandrel.  
     
     
         2 . A method according to  claim 1 , in which the material is supported in a surrounding structure together with the former.  
     
     
         3 . A method according to  claim 1  or  claim 2 , in which the material is thermoplastic or thermosetting and the material is set by heat setting.  
     
     
         4 . A method according to  claim 1 , wherein the material is woven.  
     
     
         5 . A method according to  claim 1 , wherein the material is knitted.  
     
     
         6 . A method according to  claim 1 , in which the material is pre-tensioned during the introduction of the helical formation.  
     
     
         7 . A method according to  claim 6 , in which the material is pre-tensioned to 10% of its maximum extensibility.  
     
     
         8 . A method according to  claim 1 , in which a second material is applied to the material after the setting operation.  
     
     
         9 . A method according to  claim 8 , wherein the former creates an indentation in the external side wall of the material and the second material is applied to the indentation.  
     
     
         10 . A method according to  claim 9 , wherein the second material overflows the indentation.  
     
     
         11 . A method according to  claim 8 , wherein the coating is a polyurethane dispersion.  
     
     
         12 . A method according to  claim 8 , wherein the second material is pressed into the tubular material.  
     
     
         13 . A method according to  claim 12 , wherein the second material does not penetrate the material to the internal side wall.  
     
     
         14 . A method according to  claim 13 , wherein the second material penetrates at least 50% but less than 100% into the side wall of the material.  
     
     
         15 . A method according to  claim 14 , wherein the second material penetrates 80% to 90% into the side wall.  
     
     
         16 . A method according to  claim 1 , in which a strand of a third material having a different modulus of elasticity to the tubular material is introduced into and secured in the helical formation after the setting operation.  
     
     
         17 . A method according to  claim 16 , in which the strand material comprises a monofilament.  
     
     
         18 . A method according to  claim 16 , in which the strand material comprises a multifilament strand.  
     
     
         19 . A method according to  claim 16 , in which the strand is secured by applying a coating to the tubular material.  
     
     
         20 . A method according to  claim 1 , further comprising forming a concertinaed formation in the tubular material.  
     
     
         21 . A tube for a human or animal body, the tube comprising a flexible tubular material, a side wall of the tube being deformed to form a helical formation in the internal surface of the side wall of the tube.  
     
     
         22 . A tube according to  claim 21 , the tube comprising an indentation in the external surface of the side wall, and a coating applied to the indentation.  
     
     
         23 . A tube according to  claim 22 , wherein the coating penetrates the side wall of the tube.  
     
     
         24 . A tube according to  claim 23 , wherein the coating only partially penetrates the side wall.  
     
     
         25 . A tube according to  claim 22 , wherein the coating comprises a polymeric material.  
     
     
         26 . A tube according to  claim 25 , wherein the polymeric material comprises polyurethane.  
     
     
         27 . A tube according to  claim 20 , wherein the flexible tubular material is a woven material.  
     
     
         28 . A tube according to  claim 20 , wherein the flexible tubular material comprises polyester.  
     
     
         29 . A tube according to  claim 20 , wherein the tube is blood flow tubing.  
     
     
         30 . A tube according to  claim 29 , wherein the blood flow tubing is a graft.  
     
     
         31 . A tube according to  claim 30 , wherein the graft is a vascular graft.