Catheters and method of manufacture

Claim 1

A method of forming a catheter from thermoplastic materials, the catheter being of a selected length and extending axially between proximal and distal ends, the catheter having a main body extending from the proximal end and being of a first cross-section, a tip section extending towards the main body from the distal end and having a constant cross-section smaller than said first cross-section, and a transition portion between the main body and the tip section and which blends smoothly into both the main body and the tip section, the method comprising the steps: providing a die having an opening extending about a die axis, the opening having an entry portion extending inwardly from an entrance and having a cross-section corresponding to that of the main body of the catheter, a convergent intermediate portion blending into the entry portion, and an exit portion having said smaller cross-section and also blending smoothly into the intermediate portion, the exit portion terminating at an exit; providing heating means coupled to the die to elevate the die temperature to a temperature selected to cause plastic flow of the catheter material; providing a heat resistant mandrel having a leading part, a converging part leading smoothly from the tip section and a main part extending smoothly from the converging part; providing a tubular blank of catheter material having an outside shape corresponding to that of said main body and an internal shape corresponding to the shape of the main part of the mandrel so that the mandrel will slide into the blank, the blank having an entry end and a tip end having a length less than said selected length; entering the leading part of the mandrel into the blank from said entry end and moving the mandrel through the blank until some of the leading part projects beyond said tip end of the blank; operating the heating means to maintain the die at said selected temperature; retaining the mandrel and blank together as a combination and causing relative movement axially between this combination and the die so that the tip end is first through said entrance of the die; continuing said relative movement thereby causing the entry end of the blank to pass through the exit portion and to project beyond said exit causing the material of the blank to flow axially to create said tip section and thereby lengthen the blank, said relative motion continuing until the converging part of the mandrel and the intermediate portion of the die are separated by an amount to define the transition portion of the catheter; removing the catheter from the die and removing the mandrel from the catheter whereby a catheter is formed having a length greater than that of the blank and including said tip section, transitional portion, and main body.

Claim 2

A method of forming a catheter from thermoplastic materials, the catheter being of a selected length and extending axially between proximal and distal ends, the catheter having a main body extending from the proximal end and being of a first cross-section, a tip section extending towards the main body from the distal end and having a constant cross-section smaller than said first cross-section, and a transition portion between the main body and the tip section and which blends smoothly into both the main body and the tip section, the method comprising the steps: providing a die having an opening extending about a die axis, the opening having an entry portion extending inwardly from an entrance and having a cross-section corresponding to that of the main body of the catheter, a convergent intermediate portion blending into the entry portion, and an exit portion having said smaller cross-section and also blending smoothly into the intermediate portion, the exit portion terminating at an exit; providing heating means coupled to the die to elevate the die temperature to a temperature selected to cause plastic flow of the catheter material; providing a heat resistant mandrel having a leading part, a converging part leading smoothly from the tip section and a main part extending smoothly from the converging part; providing a tubular blank of catheter material having an outside shape corresponding to that of said main body and an internal shape corresponding to the shape of the main part of the mandrel so that the mandrel will slide into the blank, the blank having an entry end and a tip end having a length less than said selected length; entering the leading part of the mandrel into the blank from said entry end and moving the mandrel through the blank until some of the leading part projects beyond said tip end of the blank; operating the heating means to maintain the die at said selected temperature; retaining the mandrel and blank together as a combination and causing relative movement axially between this combination and the die so that the tip end is first through said entrance of the die; continuing said relative movement thereby causing the entry end of the blank to pass through the exit portion and to project beyond said exit causing the material of the blank to flow axially to create said tip section and thereby lengthen the blank, said relative motion continuing until the converging part of the mandrel and the intermediate portion of the die are separated by an amount to define the transition portion of the catheter; removing the catheter from the die and removing the mandrel from the catheter whereby a catheter is formed having a length greater than that of the blank and including said tip section, transitional portion, and main body.