Coating processes – Medical or dental purpose product; parts; subcombinations;...
Reexamination Certificate
1998-08-26
2001-08-28
Seidel, Richard K. (Department: 3763)
Coating processes
Medical or dental purpose product; parts; subcombinations;...
C427S430100, C604S524000, C604S264000
Reexamination Certificate
active
06280788
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a method and a system for manufacturing a catheter and to a catheter manufactured by that method.
Known methods of manufacturing catheter tubing are extrusion and dipping. Advantages of the extrusion process are that it is well-controlled and provides a catheter tubing with a smooth thin wall of a very constant thickness. However, extrusion requires relatively expensive machinery end tools. Therefore, it is mainly suitable for the production of substantial lengths of catheter tubing having a uniform cross-section, To manufacture a catheter, the catheter tubing has to be cut to the required length(s) and fittings have to be connected to the tubing. To avoid blood damage when the catheter is brought in contact with a pationt's blood in-vivo, special adhesives have to be used and smooth transitions at the fittings are required. Furthermore, catheters generally comprise reinforcement material which is uncovered when the catheter is cut to the required length. Special measures are required to cover the reinforcement material to avoid contact between a patient's blood and the reinforcement material.
In UK patent application 2 187 670 it is described to manufacture a catheter having a funnel portion of rubber or other suitable material by placing the funnel over a former and dipping the catheter with the former one or more times in a latex solution.
However, dipping has been found difficult to control and did not provide satisfactory results, as is described in “Transarterial Blood Pumps, Feasibility Phase, Final Report”; Authors: H. Duffor at al.; Ed.: Dr Or G. J. Verkerke and Dr G. Rakhorst—Groningen ISBN 90-74280-02-1.
Furthermore, a particular requirement of catheters to be brought in direct contact with a patient's blood is that the ends and transitions at fittings are as smooth as possible and that all surfaces to be contacted with blood consist exclusively of biocompatible materials which cause as little damage as possible to the blood.
SUMMARY OF THE INVENTION
One object of the invention is to provide a method of manufacturing a catheter efficiently on a small scale without expensive machinery or tools, so that catheters can efficiently be manufactured in a great variety, and with which catheters with smooth, thin walls of uniform thickness can be obtained.
Another object of the invention is to provide a low-cost system with which catheters can be manufactured efficiently at small scale in a great variety of lengths and shapes, and with which catheters with smooth, thin walls of uniform thickness can be manufactured.
Yet another object of the invention is to provide catheters which are particularly smooth at the ends or in the area of fittings to reduce blood damage to a minimum.
According to the present invention, catheters having smooth thin walls of constant thickness can efficiently be manufactured on a small scale without expensive machinery or tooling by a method in which use is made of a container with at least one passage in a lower part thereof, a mandrel sealing off this passage when inserted therein and a solution containing a plastic in the container, a cycle of inserting the mandrel into the passage and moving at least a section of the mandrel through the passage and the solution in an upward direction is repeatedly carried out to form a catheter tubing on said section of the mandrel, and the catheter tubing formed on the mandrel is removed from the mandrel.
As in a dipping method, the thickness and the distribution of the plastic material over the mandrel depends on the viscosity of the solution, the gravity and the velocity at which the mandrel is pulled out of the solution. However, since consecutive sections of the mandrel enter the solution from below and leave the solution in upward direction, a uniform residence time in the solution of at least a substantial part of the mandrel during each cycle can easily be obtained by passing that part of the mandrel through the solution with a constant velocity. Thus, the extent to which plastic adhered to the mandrel is affected by the solvent during immersion in the solution is uniformly distributed over the part of the mandrel passed through the solution at a constant velocity. This results in a well-controlled uniform thickness of each layer. A multitude of these layers applied consecutively forms a catheter tubing constituted by a plurality of very thin layers and having a uniform thickness. Since the mandrel may be held vertically, no particular measures for avoiding bending of the mandrel are required.
If a predetermined variation of the residence time over the length of the mandrel is desired, the velocity of the mandrel can be varied accordingly.
In accordance with a further aspect of the invention, a system specifically adapted for carrying out the method according to the invention is provided, which system includes a container with a cavity for holding a solution containing a dissolved plastic material, which container is provided with at least one passage in a lower part of the cavity, a mandrel sealing off that passage when inserted into that passage, and means for passing at least a section of said mandrel through said passage in an upward direction.
The invention can further be embodied in a catheter which can specifically be obtained by a particular mode of carrying out the method according to the invention. Such a catheter according to the present invention includes a tubing and a fitting, the fitting being encapsulated by wall material of the tubing extending along the inside and the outside of said fitting.
Such a catheter can for example be manufactured by positioning the fitting over a wall coating previously applied to the mandrel and by subsequently applying the further layer or layers of wall material.
When the catheter is finished, a continuation of the wall material of the tubing of the catheter encapsulates at least parts of the fitting, so that a very smooth seamless outer surface is obtained in the area of the fitting. Any adhesive between the wall material and the fitting is shielded from blood and tissue of the patient, when the catheter extends into a patient.
Further details and advantages of the method, the system and the catheter according to the present invention appear from the following description, the drawings and the claims.
REFERENCES:
patent: 610224 (1898-09-01), Braddock
patent: 813618 (1906-02-01), Chapman et al.
patent: 2127413 (1938-08-01), Leguillon
patent: 3557749 (1971-01-01), Farago
patent: 3638919 (1972-02-01), Phipps
patent: 3842799 (1974-10-01), Podkletnov
patent: 3930462 (1976-01-01), Day
patent: 4024046 (1977-05-01), Lupinski et al.
patent: 4259379 (1981-03-01), Britton et al.
patent: 4993354 (1991-02-01), Makita et al.
patent: 5009933 (1991-04-01), Matsuda et al.
patent: 5217533 (1993-06-01), Hay et al.
Brinckmann Günter
Rakhorst Gerhard
Verkerke Gijsbertus Jacob
Fink Edward M.
Michaelson Peter L.
Michaelson & Wallace
Rijksuniversiteit Groningen
Seidel Richard K.
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