Method of making a catheter

A continuous method of making a finished reinforced catheter from a thermoplastic material having an inner diameter and an outer diameter with a single extrusion step and without application of pressure from an external source to said inner diameter comprising the steps of:

• continuously extruding a mandrelized catheter body as in interim structure having an outer diameter about equal to the outer diameter of said finished reinforced catheter;
• heating said mandrelized catheter body to a temperature to cause said thermoplastic material to exhibit a predetermined degree of viscosity;
• continuously applying a tensioned length of a reinforcing member to an outer surface of said heated interim catheter body by a guide rotating in a plane approximately normal to movement of the catheter body to define a helix angle determined by the ratio of the length through which the tube advances for each complete rotation of the guide;
• the step of applying being carried out while said catheter body is sufficiently viscous to permit deformation at a surface contour of said catheter body by an amount at least equal to the volume of said reinforcing material embedded and penetration of said reinforcing member through a wall of said catheter body to locate said reinforcing member entirely therein at a location determined by said viscosity and tension on said reinforcing member while the length of reinforcing member is applied thereto;
• and
• smoothing the outer surface of said catheter body with said helically wrapped reinforcing member applied thereto to form said finished catheter product, while eliminating a second step of extruding an outer wall portion of a finished catheter product.

A method of continuously making catheter tubing having an internal bore of accurate dimensions in a single extrusion step without applying pressure from an external source through said internal bore, comprising the steps of:

• applying a reinforcing material to a mandrelized tube travelling at a relatively fixed linear rate and having an external diameter about equal to the desired external diameter of catheter tubing, said tube defining an external wall surface and an internal wall surface, to locate said reinforcing material within said tube at any location intermediate said external and said internal wall surfaces, the applying step being carried out while said tube is sufficiently heated to exhibit a viscosity at said linear rate sufficient to permit said reinforcement material to travel under tension from a location external to said exterior wall surface to said predetermined location within said tube, the temperature of said tube and the tension on said reinforcing material being selected to cooperate to carry out effectively said applying step for the material of said tube when traveling at said linear rate,
• causing said tube with said reinforcement embedded therein to cool sufficiently to solidify, thus to embed said reinforcement therein;
• and
• smoothing the exterior surface of said tube while traveling at said linear rate with said reinforcement therein to a smooth surface finish with a tolerance such as .+-.0.0005 inches which is suitable for use in catheters, said smoothing step following said cooling step without an interventing step of extruding another layer of tubing on said reinforcement tubing, thereby to form reinforced catheters, said smoothing step following said cooling step without an intervening step of extruding another layer of tubing on said reinforcement tubing thereto to form reinforced catheter stock.