Method of making a metallic thin wire for a medical tool
In a method of making a metallic thin wire 1, one single metallic thin wire 2 is prepared to have a predetermined length with a middle portion of the one single metallic thin wire 2 as a fixed portion. Front and rear half portions of the one single metallic thin wire 2 are twisted with a tensile weight W applied to the front and rear half portions in the lengthwise direction. The one single metallic thin wire 2 is processed with a heat treatment to remove a residual stress. This provides the metallic thin wire 1 with a high rotation-following capability and high torque transmissibility, thus enabling artisans to usefully apply the metallic thin wire 1 to a main wire component 25 of a medical tool and equipment.
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1. Filed of the Invention
The invention relates to a method of making a metallic thin wire in the form of a flexible wire configuration used as a main wire component of a medical tool such as a catheter, a catheter guide wire, an endscope treating instrument or the like.
2. Description of Prior Art
In a catheter and a catheter guide wire which introduces a leading distal end into a diseased area through a sinuous vascular system, the leading distal end of the catheter or the catheter guide wire is inserted into the blood vessel or the somatic cavity by a “push-pull and turn” manipulation at a hand access portion located outside a subject patient upon treating the diseased area. In an endscope treating instrument which is inserted through a somatic cavity to reach the diseased area, a leading end of the endscope treating instrument is manipulated in the same manner as mentioned above.
In order to achieve a smooth manipulation when inserting the leading distal end into the somatic cavity and the blood vessel, it is required for these medical devices to have multi-mechanical properties. The multi-mechanical properties include a high flexibility, a good straightness and restitutivity in an unrestricted free state against bending deformation. The medical devices of these types are required at its leading distal end portion to have a high flexibility, while at the same time, required at its rear portion to have an appropriate rigidity as a functionally gradient property. It is also indispensable for the leading distal end to have a good maneuverability in which the leading distal end properly responds to the hand operation conducted outside the subject patient.
The following publications disclose flexible linear wires used as a main component of the medical devices with an aim to achieving the above indispensable multi-mechanical properties.
In the references of Laid-open Japanese Patent Application No. 7-148267 and Domestic Publication No. 2000-512691 (referred in turn to as “first and second reference” hereinafter), the first reference shows a method of making a metallic thin wire in which a metallic wire is mechanically rolled straight through a correction roller, and then thermally treated to remove a residual stress so as to produce a medical guide wire superior in linearity and straightness.
The second reference also shows a method of making a metallic thin wire in which a thin wire is made of a shape-memory alloy, and twisted under a tensile force applied to the thin wire, and then thermally treated to remove a residual stress so as to produce a catheter guide wire.
The medical guide wire produced by the first reference is superior in a lengthwisely directed straightness. It is, however, poor in torsional characteristics. This leads to a shortage of the torque transmissibility and rotational maneuverability so as to reduce a good steerability.
The catheter guide wire produced by the second reference specifies the shape-memory alloy, and only one metallic thin wire is prepared each time the method is used upon producing the catheter guide wire. This makes the catheter guide wire costly and disadvantageous especially when brought to the mass production. In addition, the metallic thin wire is twisted only in one direction, and thus making the torsional characteristics uneven in the lengthwise direction. Because the metallic thin wire is twisted only in one direction, and not twisted further in another direction, the metallic thin wire becomes to lose the torque transmissibility and rotation-following capability so as to reduce the steerability when applied to the medical guide wire, and maneuvered to swivel the guide wire in the right and left directions upon inserting the guide wire into the vascular vessel.
Therefore, it is an object of the invention to overcome the above drawbacks so as to provide a method of making a metallic thin wire for a medical tool which are capable of improving a rotation-following capability and torque transmissiblity so as to enhance a steerability.
SUMMARY OF THE INVENTIONAccording to other aspect of the present invention, one single metallic thin wire is prepared to have a predetermined length or a bifold extension of the predetermined length. A middle portion of the one single metallic thin wire is fixedly supported at a fixed portion. Front and rear half portions of the one single metallic thin wire is twisted (in one direction) with the front and rear half portions symmetrically located at both sides of the fixed portion. At the time of twising the front and rear half portions, a tensile weight is concurrently applied to the front and rear half portions. This produces two metallic thin wires simultaneously in a dual-way fashion to maintain the product quality uniform, while at the same time, improving the productivity.
The one single metallic thin wire is divided into a plurality of zones in the lengthwise direction, each of which is twisted in different number of turns, or processed with the heat treatment in varying degrees so as to enhance the performance when the one single metallic thin wire is applied to a medical tool or equipment. From the same viewpoint, an outer surface of the one single metallic thin wire is treated with an electrolytic polishing procedure. Alternatively, the one single metallic thin wire is made of an austenitic stainless steel.
With the one single metallic thin wire processed with the heat treatment to remove the residual stress, it is possible to imparts the metallic thin wire with a highly improved linearity and straightness.
This enables a user to produce the metallic thin wire highly superior in the rotation-following capability (torsional rigidity and torque transmissibility) in both the right and left directions while securing a high flexibility and linearity in the one single metallic thin wire.
For a medical tool and equipment into which the metallic thin wire is incorporated as the main wire component, the present method enables the main wire component to a highly superior rotation-following capability (torsional rigidity and torque transmissibility) so as to enhance the performance depending on its usage.
The metallic thin wire thus produced is applied to a main wire element, a shaft, a stylus, a pull-wire, a stent and a needle in the medical tools such as, for example, a catheter, a balloon catheter and a medical endscope.
A preferred form of the present invention is illustrated in the accompanying drawings in which:
In the following description of the depicted embodiments, the same reference numerals are used for features of the same type.
Referring to
The thin wire 2 has a predetermined length (e.g., 1.000-1.500 mm), one end of which is firmly clamped by a rotary chuck 11. The other end of the thin wire 2 is clamped by a slidable chuck 12 which is provided slidably in a lengthwise direction. The slidable chuck 12 has a tensile weight W which hangs down a static load 13 to apply a tensile weight W to the thin wire 2 in its stretchy direction. This brings the thin wire 2 straight to the stretch between the rotary chuck 11 and the slidable chuck 12 with the tensile weight W as a torsion-resistant load. Across the rotary chuck 11 and the slidable chuck 12, an electrically conductive line 18 is connected to be energized by a current generator 17. With the energization of the current generator 17, the electric current flows through the thin wire 2 to thermally treat the thin wire 2 by its electric resistance.
With the thin wire 2 thermally treatable under the tensile weight W, the thin wire 2 is primarily twisted about its axis in the direction as shown at an arrow M in
Concurrently with the secondarily twisting the thin wire 2 or after the secondarily twisting the thin wire 2, the thin wire 2 is processed with the heat treatment due to the electric resistance to remove the residual stress from the thin wire 2. This process enables the metallic thin wire 1 to a highly superior rotation-following capability and linearity as shown in
After the end of the heat treatment, the metallic thin wire 1 is treated at its outer surface with an electrolytic polishing procedure so as to be consecutively produced as the main wire component 25 of the medical guide wire 20 for the purpose of mass production.
By way of example, an outer diameter of the main wire component 25 measures 0.342 mm, the primarily twisting numbers of turns is 125-185, the secondarily twisting numbers of turns is 18-280, the electric current employed herein is for 3-5 minutes at 2.0-2.3 ampere, and the tensile weight W measures 4-6 kg as the torsion-resistant load.
The primarily twisted thin wire 2 progressively decreases its twisted numbers of turns from one side 3 of the rotary chuck 11 to the other side 4 of the slidable chuck 12 as shown at an initial metamorphous stage 2A in
Based on the composite metamorphosis of the thin wire 2 primarily and secondarily twisted and a total sum of the primarily and secondarily twisted numbers of turns, the thin wire 2 comes to be equally twisted substantially through the entire length of the thin wire 2. By primarily and secondarily twisting the thin wire 2 alternately, a torsional rigidity is induced on the thin wire 2 equally in its lengthwise direction to impart the thin wire 2 with a uniform rotation-following capability and linearity substantially through the entire length of the thin wire 2. Wavy curves depicted on the metallic thin wire 1, the thin wire 2 and the main wire component 25 in
More particularly, during primarily twisting the thin wire 2, a torsional surface appears on the thin wire 2 as shown at stage one 2C in
In the second embodiment of the invention, an intermediary clamp device 14 is slidably placed between the rotary chuck 11 and the slidable chuck 12 in the twisting device 10 as shown in
The thin wire 2 thus provided has a mechanical property in which a bending characteristics differs hard and soft depending on the zones X, Y and Z as shown in
Namely, the most rigid portion of the medical tools is a place in which the hand access portion 27 positions to be grasped and maneuvered outside the subject patient. The most flexible portion of the medical tools is a leading head portion to be inserted into the blood vessel and somatic body.
In this instance, any of the metallic thin wire 1 can be used which represents the first and second embodiment of the invention.
In this instance, the thin wire 2 symmetrically locates its right (front) half portion and left (rear) half portion in a dual fashion. Thereafter, the right and left half portions are primarily and secondarily twisted in the same manner as done in the first embodiment of the invention. With the use of the dual rotary chuck 11 A, two metallic thin wires can be produced concurrently, thus reducing the manufacturing cost with a high productivity. The two metallic thin wires are produced under the same conditions, thus contributing to equalizing the quality of the product.
This results in the guide wire 20, 20A and the balloon catheter 21 having a transmissible elongation made of the thin metallic wire 1 to transmit a manipulation from the hand access portion 27 to the leading head portion 28. This enables the hand access portion 27 to transmit its push-pull and rotational movement in quick response to the leading head portion 28 with a high accuracy. This ensures a good maneuverability of the guide wire 20, 20A and the balloon catheter 21 so as to secure a quicker remedial treatment against the diseased area.
When the metallic thin wire 1 is wrought out to have the functionally gradient characteristics as done in the second and third embodiments of the invention, and the metallic thin wire 1 is applied to the main wire component 25 of the guide wire 20, 20A, the functionally gradient characteristics makes the hand access section 27 flexible, while at the same time, making the rigid leading head portion 28 hard, thus significantly improving the mechanical property as required for the guide wire 20, 20A.
In addition, the metallic thin wire 1 made of the austenitic stainless steel as described from the fifth to seventh embodiments of the invention has the following advantages as the guide wire 20, 20A.
When a martensitic stainless steel is used to the main wire component 25 as shown in
On the other hand, a ferritic stainless steel has the property referred to as “475° C. fragility” and having the property called as “sigma fragility” occurred when heated to approx. 600-800° C. for an extended period of time. Especially, the ferritic stainless steel makes the crystallized particles grow to reveal “high temperature frailty” when heated to 950° C. or more, thereby deteriorating the quality as the medical guide wire due to the thermal influence brought by thermally bonding the bulge head portion 29.
However, since the austenitic stainless steel is less subjected to the textural metamorphosis when heated, it is less affected by the heat generated at the time of thermally bonding the bulge head portion 29. The austenitic stainless steel further has a relatively small thermal conductivity and a greater coefficient of thermal expansion which is approx. 1.5-1.6 times as large as that of the general stainless steel. This means that the thermal expansion and the thermal stress produced on the main wire component 25 by thermally bonding the bulge head portion 29 are absorbed by a limited area of the main wire component 25 in the neighborhood of the bulge head portion 29. This alleviates the residual stress produced by thermally bonding the bulge portion 29, and thereby maintaining the good linearity and favorable flexibility even in the restricted portion of the main wire component 25 near the bulge head portion 29.
The thin wire 2 contracts and stretches in the lengthwise direction when primarily and secondarily twisted alternately and then processed with the heat treatment. Due to the greater coefficient of thermal expansion of the austenitic stainless steel, a stroke appeared when the thin wire 2 contracts and stretches becomes longer to work out the outer surface of the thin wire 2 to help it form a closely packed structure.
While on the other hand, the martensitic stainless steel has a quench hardening property by which a tensile strength is reinforced, the austenitic stainless steel increases its strength when drawn (work hardening) so as to be well-suited to the medical guide wire 20, 20A. Since an electric resistance of the austenitic stainless steel is approx. five times as great as that of the carbon steel, and is approx. 1.6 times as great as that of the martensitic stainless steel. This alleviates an intensity of the electric current necessary to thermally bond the bulge head portion 29, whereby limiting the thermally bonding heat to a necessary minimum so as to lessen a bending and torsional deformation under the influence of the heat generated by thermally bonding the bulge head portion 29.
With the thin wire 2 specified by the austenitic stainless steel, the thin wire 2 is magnetized and mirror-finished at its outer surface when drawn by a dice tool. This attracts ferric particles to the outer surface of the thin wire 2 and collects foreign matters on the thin wire 2 with the help of the Van del Waals' force based on the intermolecular affinity. When the foreign matters are collected, the passive rust corrosion and the crevice corrosion would occur between the outer surface of the thin wire 2 and the foreign matters so as to likely reduce a corrosion-resistant property.
On the contrary, with the outer surface of the thin wire 2 electrolytically polished, oxidized scales are removed from the thin wire 2 to restore an original concentration of chromium component of the thin wire 2 so as to resultantly improve the corrosion-resistant property.
As apparent from the foregoing description, the subject method of making a metallic thin wire enables the artisans to mass produce one single metallic thin wire with a high rotation-following capability and high linearity (straightness) provided. The one single metallic thin wire has such good properties as to be appropriately applicable to main constituents of high quality medical tools. This effectively enhances the quality and the performance of the medical tools depending on their usage so as to improve remedial skills and an efficiency of the medical treatment.
It is to be noted that the primarily and secondarily twisting procedures are combined to form a unitary set, and the unitary set is repeatedly applied to the one single metallic thin wire in a plurality of turns.
Only the primarily twisting procedure may be applied to the one single metallic thin wire without the secondarily twisting procedure.
Metallic object to be primarily and secondarily twisted is not merely confined to the one single metallic thin wire but also a wire-stranded hollow tube in which the secondarily twisting turns is one time the primarily twisting turns or less than that. In this instance, the wire-stranded hollow tube is primarily twisted in the same direction in which the wire-stranded hollow tube was stranded.
Not only the austenitic stainless steel but other metallic material may be applied to the one single metallic thin wire. After the end of the heat treatment, the electrolytic polishing procedure may be omitted.
The metallic thin wire may be used to not only the guide wire and balloon catheter but also an endscope treating tool, flexible type endscope and the like. The metallic thin wire may be used to an actuation thin wire which requires the superior rotation-following capability in the case except for the medical tool.
Claims
1. A method of making a metallic thin wire comprising steps of:
- preparing one single metallic thin wire having a predetermined length with a middle portion of said one single metallic thin wire as a fixed portion;
- twisting front and rear half portions of said one single metallic thin wire, while at the same time, applying a tensile weight to said front and rear half portions, said front and rear half portions being symmetrically located at both sides of said fixed portion; and
- processing said one single metallic thin wire with a heat treatment to remove a residual stress from said one single metallic thin wire.
2. The method of making a metallic thin wire according to claim 1, wherein said one single metallic thin wire is divided into a plurality of zones in the lengthwise direction, each of which is twisted in different numbers of turns.
3. The method of making a metallic thin wire according to claim 1, wherein said one single metallic thin wire is divided into a plurality of zones in the lengthwise direction, each of which is processed with said heat treatment in varying degrees.
4. The method of making a metallic thin wire according to claim 1, wherein an outer surface of said one single metallic thin wire is treated with an electrolytic polishing procedure after processed with said heat treatment.
Type: Application
Filed: Feb 21, 2008
Publication Date: Oct 2, 2008
Applicant:
Inventors: Tomihisa Kato (Aichi-ken), Kenji Miyata (Aichi-ken)
Application Number: 12/071,496
International Classification: B21D 11/14 (20060101);