Surgery – Instruments
Reexamination Certificate
1998-01-09
2001-10-02
Thaler, Michael H. (Department: 3731)
Surgery
Instruments
C606S108000
Reexamination Certificate
active
06296633
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a ductile metal tube and tubing assembly and a method of making the same, more particularly, a medical device assembly or stent delivery system handle assembly.
A stent delivery device is used in various medical procedures to deliver a prosthesis or treatment to a body vessel. Such devices require superior mechanical characteristics because they are often pushed a significant distance from the body access site to the treatment site.
Various stent delivery devices are known and disclosed in U.S. Pat. Nos. 5,026,377; 5,484,444; 5,591,172; 5,628,755; and 5,662,703.
All references cited herein, including the foregoing, are incorporated herein in their entireties for all purposes.
SUMMARY OF THE INVENTION
The invention relates generally to a swaged ductile metal tubing over a plastic or polymer tubing and a method of making a medical device assembly.
The invention advantageously connects a ductile metal such as stainless steel in the form of a tube with a second member without using adhesives. For additional strength, the proximal end of the second member is mechanically rolled over forming a rollover member adjacent the end of the ductile metal tube. These procedures mechanically lock the assembly together. The handle assembly also serves as a structural portion which the valve body slides over during stent deployment and reconstrainment. A hub may be disposed over the proximal end of the assembly over the rollover member and ductile metal tube.
Generally, a stainless steel tube is bonded to the interior tube using a cyanoacrylate adhesive. In the present invention, swaging the stainless steel tube to the interior tube advantageously eliminates the need for an adhesive bond or adhesive curing with UV light and therefore reduces manufacturing time. The swaged assembly provides generally superior visual inspection as compared to an adhesively bonded tube assembly that has been through, for example, a UV cure cycle.
Swaging is a process of reducing a ductile metal tube to a smaller predetermined diameter. Properly shaped dies rotate around the work and strike blows at suitable intervals and overlapping areas to produce a generally smooth surface and smaller diameter. Reducing the outer diameter causes a similar reduction in the inside diameter in the swaged tube. Swaging equipment is available from Torrington Swager and Vaill End Forming Machinery Inc. in Waterbury, Conn.
In the present invention, a stainless steel tube is placed over the plastic or polymer interior tube. Preferably, a mandrel is inserted into the plastic tube beneath the area where swaging occurs to support the tubing during the impact forces on the outside of the tube. After swaging, the inside diameter of the interior tube is generally not reduced in diameter due to a properly sized mandrel in the interior tube during the swaging process. Generally, a mandrel about 0.002 inches in diameter less than the inside diameter of the interior tube is desired during swaging. Use of the mandrel is necessary to prevent the lumen from reducing in size or the interior tube being damaged during the swaging process. With proper die selection, it is unlikely that a mandrel would be captured by the assembly. Generally, swaging does not displace tubing material sufficiently to prevent removal of the mandrel.
The assembly is fed into the swaging machine and the outer ductile metal tube is deformed to a predetermined smaller diameter over approximately a one inch length. After swaging, a portion of the length of the metal tube is reduced in diameter. A generally corresponding reduction in the inside diameter of the stainless steel tube will cause the inside surface of the metal tube to contact and become embedded in the plastic or polymer interior tube and form a mechanical bond. With properly sized swaging dies, the metal material is formed down onto the interior tubing and makes intimate contact therewith.
A Rockwell hardness of 85B is the maximum preferred hardness for carbon steels to be used for swaging. Austenitic stainless steels such as the AISI 304 series are preferred for swaging. Other metals with similar ductile properties may also be used.
The preferred die design is a standard single taper. Other designs such as double taper, double extension, or single extension may also be used. Die size is determined by the amount of material that must be moved to form the swaged bond between the metal tube and the polymer tube. Generally, a maximum diameter reduction of 0.002 inches to 0.004 inches in the metal tube is preferred in order to prevent excessive cracking or folding of the material.
The interior tube is preferably made of polyetheretherketone such as a PEEK material which is a high temperature, semi-crystalline material with generally high temperature and strength properties. During the swaging process, the swaged steel tube embeds into the surface of the interior tube. PEEK material lends itself to swaging as it does not spring back appreciably. PEEK material is commercially available and has a flexural modulus ranging from about 440,000 psi to about 2,400,000 psi. PELLETHANE material is a thermoplastic polyurethane elastomer with a Shore A hardness ranging from about 55 to 95 and a Shore D hardness ranging from about 45 to 85. Other plastics, polymers and metal tubes are envisioned to be interior members disposed in the ductile metal tube and a component of the swaged assembly in the present invention.
In addition to the swaging process, a portion of the plastic tubing extending proximal of the metal tube may be rolled over to substantially lock the metal tube into position. Rolling over the interior tube is accomplished by pushing the tube onto a heated forming pin against a stop. When the end of the tube hits the stop it rolls back on itself forming a radially extending member. Heating the tool facilitates the forming of the member. Swaging and the rollover member form mechanical lock occurs between the tubes. The rollover member helps resist the ductile metal tube from being pulled off the interior tube.
In sum, the invention relates to a swaged medical device assembly including a first tubing with a proximal end, a distal end, a length, and an outside diameter and a ductile metal tubing. The ductile metal tubing has a proximal end, a distal end, a length, a lumen, and a first outside diameter. The ductile metal tubing is disposed over at least a portion of the length of the first tubing. A portion of the length of the ductile metal tubing has a smaller second outside diameter displacing a portion of the first tubing and a mechanical bond is formed therebetween. The proximal end of the first tubing may extend proximal of the proximal end of the ductile metal tubing and the proximal end of the first tubing may have at least one member extending in an outward radial direction from the longitudinal axis. The member provides one or more structural surfaces to cooperate with the ductile metal tubing and limit movement therebetween. At least one member may cooperate with the ductile metal tubing to resist torque and tensile forces. The assembly may withstand a tensile force of less than about 8 pounds. The first tubing may be made of PEEK or PELLETHANE. The first tubing may have one or more lumens. The assembly may further include one or more additional elements of a stent delivery device. The first tubing may be a medical grade tubing. The assembly may be used in an implantable device or a medical device. The smaller second outside diameter have a length ranging from about one-half inch to about one and one-half inches. The assembly may cooperate with a valve body during stent deployment and reconstrainment. The ductile metal tubing may be made of a stainless steel. The stainless steel may be AISI 304. The stainless steel may be austenitic. The ductile metal tubing may be made of a carbon steel having a maximum Rockwell hardness of about 85B. The mechanical bond may be at least partially formed by resistance to displacement of the first tubing after a portion of the d
Messal Todd P.
Schneider (USA) Inc.
Thaler Michael H.
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