WO2024090368A1

WO2024090368A1 - Medical shaft and method for producing medical shaft

Info

Publication number: WO2024090368A1
Application number: PCT/JP2023/038138
Authority: WO
Inventors: 健後藤; 浩二亀岡
Original assignee: ニプロ株式会社
Priority date: 2022-10-24
Filing date: 2023-10-23
Publication date: 2024-05-02

Abstract

The present invention provides a medical shaft which has a novel structure and which makes it possible to fit, to a fixed position, a resin tube that covers a region of a shaft body from a small-diameter portion to a large-diameter portion, while suppressing the occurrence of problems caused by an increase in diameter.　Provided is a medical shaft 10 wherein: a shaft body 12 is provided with a change part 37 in which the outer diameter dimension changes between a small-diameter portion 34 and a large-diameter portion 36; a region of the shaft body 12 which is from the small-diameter portion 34, through the change part 37, and to the large-diameter portion 36 is continuously covered in the lengthwise direction by a resin tube 14; the resin tube 14 has a structure in which a small-diameter side heat-shrink tube 48 that covers the small-diameter portion 34 and a large-diameter side heat-shrink tube 50 that covers the large-diameter portion 36 are joined; and a joining part 46, which has a larger thickness dimension than one of the small-diameter side heat-shrink tube 48 and the large-diameter side heat-shrink tube 50, is positioned further to the small-diameter portion 34 side at which the change part 37 is positioned than an end part of the large-diameter portion 36 of the shaft body 12.

Description

Medical shaft and manufacturing method thereof

The present invention relates to a medical shaft that is used to perform treatment inside a patient's body by operating it from outside the body, and a method for manufacturing the medical shaft.

In the medical field, various longitudinal medical shafts are used to operate from outside the patient's body to perform treatment inside the patient's body. For example, a tubular medical device (puncture rod) that delivers electrical energy to specific tissues inside the body, as disclosed in International Publication No. 2013/179103 (Patent Document 1), and a therapeutic catheter are known.

Incidentally, such medical shafts may have a resin layer covering the outer surface of the shaft body for some purpose, such as protecting biological tissue, preventing energy loss, and ensuring durability.

In addition, medical shafts are sometimes inserted into a specific location inside the body through a dilator, sheath, catheter, etc., and are required to be stably held in place by the resin layer coating, without peeling off or shifting, even when in sliding contact with the dilator, etc.

For these reasons, when realizing a resin layer covering the outer periphery of the shaft body, it is possible to form the resin layer by, for example, applying a resin material to the outer periphery of the shaft body, but this makes it difficult to form a resin layer of a uniform and sufficient thickness. On the other hand, it is also possible to insert a resin tube formed separately to a uniform thickness onto the shaft body and fix it with an adhesive, but in addition to the troublesome bonding process, there are concerns about the adverse effects of the adhesive on biological tissue.

International Publication No. 2013/179103

The inventor therefore considered fitting a heat shrink tube onto the outer circumferential surface of the shaft body to fix the resin layer in position relative to the shaft body.

However, it was found that when the outer diameter of the shaft body varies along its length, such as when the tip of the shaft body is small in diameter, a new problem exists in that it is difficult to stably attach the heat shrink tube to the shaft body in a fitted state over its entire length. In other words, when a heat shrink tube that can be fitted onto the large diameter part of the shaft body is used, the heat shrink tube does not shrink sufficiently in the small diameter part of the shaft body, creating gaps and making it difficult to exert its fixing force. On the other hand, when a heat shrink tube is fitted onto the small diameter part of the shaft body, a large diameter heat shrink tube with a large heat shrink rate is used, which not only significantly limits the freedom of choice of material for the heat shrink tube, but also creates problems such as the thickness dimension of the resin layer after heat shrinkage becoming large, making it difficult to avoid impeding the insertion performance due to the large diameter of the medical shaft.

The problem to be solved by this invention is to provide a medical shaft with a shaft body whose outer diameter varies along its length, and which has a novel structure that allows a plastic tube that covers the area of the shaft body from the small diameter section to the large diameter section to be attached in a fixed position over the entire length of the shaft body while minimizing problems caused by the large diameter.

The present invention also aims to provide a new method for manufacturing medical shafts, which is targeted at medical shafts having a shaft body whose outer diameter dimensions vary along the length, and which allows a resin tube that covers the area of the shaft body from the small diameter portion to the large diameter portion to be attached in a fixed position over the entire length of the shaft body while minimizing problems caused by increasing the diameter.

Below, preferred embodiments for understanding the present invention are described, but each embodiment described below is described as an example, and not only can they be used in combination with each other as appropriate, but the multiple components described in each embodiment can also be recognized and used independently as far as possible, and can also be used in combination with any of the components described in another embodiment as appropriate. As a result, the present invention is not limited to the embodiments described below, and various alternative embodiments can be realized.

The first aspect is a medical shaft that is inserted into the body of an animal during treatment, and the shaft body has a small diameter portion and a large diameter portion with different outer diameter dimensions in the length direction, and a transition portion where the outer diameter dimension changes is provided between the small diameter portion and the large diameter portion, while the shaft body is continuously covered in the length direction with a resin tube in the area from the small diameter portion through the transition portion to the large diameter portion, and the resin tube is a joint structure in which a small diameter side heat shrink tube covering the small diameter portion and a large diameter side heat shrink tube covering the large diameter portion are joined, and a joint portion that is provided in the arrangement area of the heat shrink tube with the smaller thickness between the small diameter side heat shrink tube and the large diameter side heat shrink tube and has a thickness dimension larger than that of the heat shrink tube with the smaller thickness is positioned on the small diameter portion side where the transition portion is located, rather than the end of the large diameter portion of the shaft body.

In a medical shaft constructed according to this embodiment, the resin tube covering the shaft body having a small diameter portion and a large diameter portion is composed of a small diameter side heat shrink tube that covers the small diameter portion of the shaft body and a large diameter side heat shrink tube that covers the large diameter portion of the shaft body. As a result, for example, by making the diameter of the small diameter side heat shrink tube before heat shrinking smaller than the diameter of the large diameter side heat shrink tube before heat shrinking, it is possible to fit the small diameter side heat shrink tube into the small diameter portion of the shaft body while fitting the large diameter side heat shrink tube into the large diameter portion of the shaft body, and the resin tube is attached in a state of being aligned with the shaft body over its entire length.

In addition, because the resin tube is a joint structure between the small diameter heat shrink tube and the large diameter heat shrink tube, the joint between the small diameter heat shrink tube and the large diameter heat shrink tube is thicker than the heat shrink tube with the smaller thickness dimension, but the thick joint is located closer to the small diameter portion where the transition portion is located than the end of the large diameter portion of the shaft body. In this way, by adopting a joint structure between the small diameter heat shrink tube and the large diameter heat shrink tube, the thick joint is located on the small diameter portion side of the shaft body that is smaller in diameter than the large diameter portion, so that the increase in diameter of the medical shaft due to the thick joint is less likely to be a problem.

The second aspect is the medical shaft described in the first aspect, in which the transition portion in the shaft body has a tapered portion in which the outer diameter dimension changes in the length direction between the small diameter portion and the large diameter portion, and the joint portion in the resin tube is positioned in a portion that covers the tapered portion.

In a medical shaft constructed according to this embodiment, a tapered portion is provided between the small diameter portion and the large diameter portion, so that the change in the outer diameter dimension between the small diameter portion and the large diameter portion is relatively gradual, and even when the shaft body is covered with a resin tube, the change in the outer diameter dimension of the resin tube at the portion covering the tapered portion is relatively gradual, and local thinning of the resin tube is easily avoided. In particular, by providing a joint having a thickness larger than that of the small diameter side heat shrink tube and the large diameter side heat shrink tube in a tapered portion having a smaller diameter than the large diameter portion, excessive increase in diameter at the position where the joint is formed is suppressed, and for example, even when the medical shaft according to this embodiment is inserted into a dilator or the like, the risk of the medical shaft getting caught on the dilator or the like can be reduced.

The third aspect is the medical shaft described in the first aspect, in which the transition portion in the shaft body has a stepped portion where the outer diameter dimension changes in a stepped manner between the small diameter portion and the large diameter portion, and the joint portion in the resin tube is positioned at a portion that covers the end portion of the small diameter portion in the shaft body on the stepped portion side.

With the medical shaft constructed according to this embodiment, even if the outer diameter changes stepwise between the small diameter portion and the large diameter portion, the joint in the resin tube is provided at the portion covering the end of the small diameter portion on the step-like portion side, so that the thickness of the resin tube at this portion is increased, and the step-like change in the outer diameter can be reduced or eliminated by the thick-walled resin tube. As a result, a sudden change in the outer diameter between the portion of the resin tube covering the small diameter portion of the shaft body (small diameter side heat shrink tube) and the portion of the resin tube covering the large diameter portion of the shaft body (large diameter side heat shrink tube) is suppressed, and the small diameter side heat shrink tube and the large diameter side heat shrink tube can be connected with a relatively gently curved surface shape on the outer circumferential surface of the resin tube. As a result, even if the outer diameter of the shaft body changes stepwise, angular protrusions on the outer circumferential surface of the medical shaft can be easily avoided, and for example, even when the medical shaft according to this embodiment is inserted into a dilator or the like, the risk of the medical shaft getting caught on the dilator or the like can be reduced.

The fourth aspect is a medical shaft that is inserted into the body of an animal during treatment, the shaft body having a small diameter portion and a large diameter portion with different outer diameter dimensions in the length direction, a transition portion where the outer diameter dimension changes is provided between the small diameter portion and the large diameter portion, the shaft body is covered with a resin tube continuously in the length direction in the region from the small diameter portion through the transition portion to the large diameter portion, and the resin tube is a joint structure in which a small diameter side heat shrink tube covering the small diameter portion and a large diameter side heat shrink tube covering the large diameter portion are joined, and the small diameter side heat shrink tube and the large diameter side heat shrink tube are overlapped and joined to each other at a position closer to the small diameter portion side where the transition portion is located than the end of the large diameter portion of the shaft body.

In a medical shaft constructed according to this embodiment, as in the first embodiment, the small diameter heat shrink tube can be fitted to the small diameter portion of the shaft body while the large diameter heat shrink tube can be fitted to the large diameter portion of the shaft body, and the plastic tube is attached in a state where it is aligned with the shaft body over its entire length.

In addition, the joint, which becomes thicker when the small diameter heat shrink tube and the large diameter heat shrink tube are joined together in an overlapping state, is located on the small diameter side where the transition is located, rather than on the end of the large diameter part of the shaft body, so the increase in diameter of the medical shaft caused by the thickening of the joint is less likely to be a problem.

The fifth aspect is the medical shaft described in the fourth aspect, in which the transition section in the shaft body has a tapered section in which the outer diameter dimension changes in the longitudinal direction between the small diameter section and the large diameter section, and the small diameter side heat shrink tube and the large diameter side heat shrink tube are overlapped and joined to each other at a portion of the shaft body that covers the tapered section.

In a medical shaft constructed according to this embodiment, as in the second embodiment, the change in the outer diameter of the resin tube at the portion covering the tapered portion is relatively gradual, and excessive enlargement of the diameter at the joint position (the position where the joint is formed) between the small diameter side heat shrink tube and the large diameter side heat shrink tube can be suppressed.

The sixth aspect is a medical shaft as described in the fourth aspect, in which the transition portion in the shaft body has a stepped portion where the outer diameter dimension changes in a stepped manner between the small diameter portion and the large diameter portion, and the small diameter side heat shrink tube and the large diameter side heat shrink tube are overlapped and joined to each other at a portion covering the end of the small diameter portion of the shaft body on the stepped portion side.

In a medical shaft constructed according to this embodiment, as in the third embodiment, the small diameter heat shrink tube and the large diameter heat shrink tube can be connected on the outer circumferential surface of the resin tube in a curved shape that is connected relatively gently in the length direction, eliminating abrupt changes in outer diameter in the stepped portion of the shaft body.

The seventh aspect is a medical shaft according to the third or sixth aspect, in which the outer circumferential corner of the end of the large diameter portion of the shaft body on the stepped portion side is chamfered.

In a medical shaft constructed according to this embodiment, the outer corners of the end of the large diameter portion on the stepped portion side are chamfered, so that the thickness dimension of the portion of the plastic tube that covers the outer corners can be easily and stably ensured, and exterior processing of the plastic tube can also be easily performed.

The eighth aspect is a medical shaft according to the third or sixth aspect, in which an intermediate ring having an outer diameter smaller than that of the large diameter portion is attached in an externally inserted state to the end of the small diameter portion of the shaft body on the stepped portion side, and the shaft body including the intermediate ring is covered with the resin tube.

In a medical shaft constructed according to this embodiment, the provision of an intermediate ring allows the change in outer diameter dimension in the small diameter portion and the large diameter portion to be gradual, dispersing the size of the step and making it substantially smaller. Therefore, even in the resin tube that covers the area between the small diameter portion and the large diameter portion, a large change in outer diameter dimension at once is avoided. Therefore, even if the difference in outer diameter dimension between the small diameter portion and the large diameter portion is relatively large, for example, by providing a resin tube that spans between the small diameter portion and the large diameter portion in the length direction across the intermediate ring, the small diameter side heat shrink tube and the large diameter side heat shrink tube can be connected with an outer circumferential surface that is relatively gently inclined.

The ninth aspect is a medical shaft according to any one of the first to eighth aspects, in which the resin tube is fixed to the shaft body in an overlapping state without using adhesive.

In a medical shaft constructed according to this embodiment, the plastic tube is fitted and fixed to the shaft body without the use of adhesives, making it possible to effectively position the plastic tube relative to the shaft body while avoiding the use of adhesives that can have adverse effects on biological tissue.

The tenth aspect is a medical shaft according to any one of the first to ninth aspects, in which the shaft body is made of metal.

In a medical shaft constructed according to this embodiment, the shaft body is covered with a resin tube, and the flexible resin tube prevents the hard metal shaft body from coming into direct contact with biological tissue, a dilator, etc. In addition, because the shaft body is made of metal, electricity and heat can be easily transferred from the base end to the tip end of the shaft body, and in such cases, for example, an electrical or thermal insulating layer can be formed on the surface of the shaft body using the resin tube.

The eleventh aspect is the medical shaft described in the tenth aspect, in which the surface of the shaft body is roughened.

In a medical shaft constructed according to this embodiment, the surface of the metal shaft body is roughened, making it easier to position the plastic tube in the axial direction relative to the shaft body and preventing the plastic tube from shifting.

The twelfth aspect is a medical shaft according to the second or fifth aspect, in which the thickness dimension of the resin tube is within the range of 0.03 to 0.50 mm at the portion covering the small diameter portion and the large diameter portion of the shaft body, and the maximum thickness dimension at the joint covering the tapered portion is 1.00 mm or less.

A medical shaft constructed according to this embodiment can effectively achieve the various desired properties, such as cushioning, insulation, and durability, achieved by covering the shaft body with a resin tube, while preventing excessive increase in diameter.

The thirteenth aspect is a medical shaft according to any one of the first to twelfth aspects, in which the difference in radial dimension between the small diameter portion and the large diameter portion of the shaft body is within the range of 0.1 to 0.8 mm.

In a medical shaft constructed according to this embodiment, the difference in radius between the small diameter portion and the large diameter portion of the shaft body is so large that it is difficult to cover them with a single tube, and the difference in radius between the small diameter portion and the large diameter portion is suppressed to a degree that can prevent the joint from becoming excessively thick or the shape of the joint from becoming distorted. Therefore, by using a resin tube that serves as a joint structure between a small diameter side heat shrink tube and a large diameter side heat shrink tube, the shaft body can be effectively covered by the resin tube.

The fourteenth aspect is a medical shaft according to any one of the first to thirteenth aspects, in which the small diameter side heat shrink tube and the large diameter side heat shrink tube are fused together and integrated at the joint of the resin tube.

In a medical shaft constructed according to this embodiment, the small diameter heat shrink tube and the large diameter heat shrink tube are fused and integrated at the joint, so that the small diameter heat shrink tube and the large diameter heat shrink tube are unlikely to separate even if concentrated stress occurs at the joint. For example, when the large diameter heat shrink tube is inserted toward the tip while sliding against a dilator or the like, concentrated tensile stress is likely to occur at the joint covering the change section, but even when such concentrated tensile stress acts, it is possible to prevent the small diameter heat shrink tube and the large diameter heat shrink tube from separating.

The fifteenth aspect is a medical shaft according to any one of the first to fourteenth aspects, in which the small diameter side heat shrink tube and the large diameter side heat shrink tube are made of the same material.

With a medical shaft constructed according to this embodiment, the small diameter heat shrink tube and the large diameter heat shrink tube can be easily fused together at the joint, making it easier to obtain high joint strength at the joint. Also, compared to when the small diameter heat shrink tube and the large diameter heat shrink tube are made of different materials, it is easier to achieve the desired performance over the entire length of the resin tube.

The sixteenth aspect is a method for manufacturing a medical shaft that is inserted into the body of an animal during treatment, comprising the steps of: preparing a shaft body having a small diameter portion and a large diameter portion with different outer diameter dimensions in the length direction, and having a transition portion between the small diameter portion and the large diameter portion, where the outer diameter dimension changes; extrapolating a small diameter side heat shrink tube to the small diameter portion of the shaft body, and extrapolating a large diameter side heat shrink tube to the large diameter portion of the shaft body, and extending the large diameter side heat shrink tube from the large diameter portion of the shaft body toward the transition portion, and attaching the small diameter side heat shrink tube to the small diameter side heat shrink tube on the transition portion side of the large diameter portion of the shaft body; The method includes a step of placing the small diameter heat shrink tube in a burlap manner, a step of covering the outer periphery of the overlapping portion of the small diameter heat shrink tube and the large diameter heat shrink tube that are fitted onto the shaft body with a molding heat shrink tube, a step of heat shrinking the molding heat shrink tube by a heat treatment to bring the tube into contact with the outer periphery of the overlapping portion of the small diameter heat shrink tube and the large diameter heat shrink tube, thereby maintaining the shape of the overlapping portion, and a step of heat shrinking the small diameter heat shrink tube and the large diameter heat shrink tube by a heat treatment to bring them into close contact with the shaft body, and a step of removing the molding heat shrink tube after the heat treatment is completed.

In the manufacturing method of medical shafts according to this embodiment, when covering a shaft body in which the small diameter portion and the large diameter portion are connected by a transition portion and the outer diameter dimension changes in the length direction with a resin tube, the small diameter heat shrink tube and the large diameter heat shrink tube are placed on the shaft body in a state where they overlap on the transition portion side of the large diameter portion, and are thermally shrunk by a heat treatment. In this way, both the small diameter portion and the large diameter portion of the shaft body are covered with the resin tube without any gaps and without becoming excessively thick.

In addition, the overlapping portion of the small diameter heat shrink tube and the large diameter heat shrink tube is heated together with the molding heat shrink tube while covered with the molding heat shrink tube, and the shrunk molding heat shrink tube adheres closely to the overlapping portion of the small diameter heat shrink tube and the large diameter heat shrink tube. As a result, the outer periphery of the overlapping portion of the small diameter heat shrink tube and the large diameter heat shrink tube is shaped by the molding heat shrink tube, making it less likely to become distorted.

The seventeenth aspect is the method for manufacturing a medical shaft described in the sixteenth aspect, in which the transition portion in the shaft body has a tapered portion in which the outer diameter dimension changes in the length direction between the small diameter portion and the large diameter portion, and during the heat treatment, the small diameter side heat shrink tube and the large diameter side heat shrink tube are arranged so as to overlap each other at the tapered portion of the shaft body.

In the manufacturing method for medical shafts according to this embodiment, the small diameter side heat shrink tube and the large diameter side heat shrink tube are arranged so that they overlap each other at the tapered portion, and by thermally shrinking the molding heat shrink tube by heating treatment, the overlapping portion of the small diameter side heat shrink tube and the large diameter side heat shrink tube can be stably and closely attached to the tapered portion of the shaft body.

The eighteenth aspect is a method for manufacturing a medical shaft as described in the sixteenth aspect, in which the transition portion in the shaft body has a stepped portion in which the outer diameter dimension changes in a stepped manner between the small diameter portion and the large diameter portion, and during the heat treatment, the large diameter side heat shrink tube is extended beyond the stepped portion from the large diameter portion of the shaft body and is positioned so as to overlap the small diameter side heat shrink tube in the small diameter portion.

In the manufacturing method for medical shafts according to this embodiment, the large diameter side heat shrink tube extends beyond the step-like portion from the large diameter portion and is positioned so as to overlap the small diameter side heat shrink tube in the small diameter portion. By thermally shrinking the molding heat shrink tube by heating, the overlapping portion of the small diameter side heat shrink tube and the large diameter side heat shrink tube can be stably and closely attached to the end of the small diameter portion of the shaft body on the step-like portion side.

The 19th aspect is a method for manufacturing a medical shaft according to any one of the 16th to 18th aspects, in which the small diameter side heat shrink tube and the large diameter side heat shrink tube are made of materials that melt with each other by the heat treatment, and the molding heat shrink tube is made of a material that does not melt with respect to the small diameter side heat shrink tube and the large diameter side heat shrink tube by the heat treatment.

In the manufacturing method for medical shafts according to this embodiment, the heat-treated small-diameter heat-shrinkable tube and the large-diameter heat-shrinkable tube melt together to form an integrated resin tube, so that the shaft body is smoothly covered with the resin tube. In addition, because the molding heat-shrinkable tube does not melt relative to the small-diameter heat-shrinkable tube and the large-diameter heat-shrinkable tube, the molding heat-shrinkable tube can be easily removed after the heating process is completed.

The twentieth aspect is the method for manufacturing a medical shaft described in the seventeenth aspect, in which the inclination angle of the tapered portion of the shaft body is within the range of 3 to 60 degrees.

In the manufacturing method for medical shafts according to this embodiment, even if the inclination angle of the tapered portion is 3 degrees or more, the use of molding heat shrink tubing makes it possible to prevent the small-diameter and large-diameter heat shrink tubing covering the tapered portion from becoming distorted by heat treatment. By making the inclination angle of the tapered portion 60 degrees or less, the entire shaft body including the tapered portion can be covered with the small-diameter heat shrink tubing and the large-diameter heat shrink tubing.

The 21st aspect is a method for manufacturing a medical shaft according to any one of the 16th to 20th aspects, in which the molding heat shrink tube extends from the transition portion of the shaft body to the small diameter portion and the large diameter portion in the longitudinal direction of the shaft body.

With this method of manufacturing a medical shaft, it is possible to cover the entire overlapping portion between the small diameter heat shrink tube and the large diameter heat shrink tube with a molding heat shrink tube, and it is also possible to stabilize the shape of the entire overlapping portion.

The 22nd aspect is a method for manufacturing a medical shaft according to any one of the 16th to 21st aspects, in which the small diameter side heat shrink tube and the large diameter side heat shrink tube are fixed in an overlapping state without being glued or welded to the outer circumferential surface of the shaft body over their entire length.

In the manufacturing method of the medical shaft according to this embodiment, the small diameter heat shrink tube and the large diameter heat shrink tube are both fixed to the outer circumferential surface of the shaft body by fitting without being glued or the like. This avoids the adverse effects on the human body caused by the use of adhesives, and also avoids the adverse effects on the shaft body caused by welding.

According to the present invention, in a medical shaft, the area of the shaft body that extends from the small diameter portion through the transition portion to the large diameter portion can be covered with a resin tube that is fixed in position relative to the shaft body, while preventing problems caused by the large diameter.

FIG. 1 is a cross-sectional view showing a medical shaft according to a first embodiment of the present invention. FIG. 2 is a diagram showing the manufacturing process of the medical shaft shown in FIG. 1, illustrating the state before the first heat treatment. FIG. 2 is a diagram showing the manufacturing process of the medical shaft shown in FIG. 1, illustrating the state after the completion of the first heating process and before the second heating process. FIG. 2 is a diagram showing the manufacturing process of the medical shaft shown in FIG. 1, illustrating the completion state of the secondary heating treatment. FIG. 3 is a cross-sectional view showing a medical shaft according to a second embodiment of the present invention. FIG. 4 is a diagram showing the manufacturing process of the medical shaft shown in FIG. 3, illustrating the state before the first heat treatment. FIG. 4 is a diagram showing the manufacturing process of the medical shaft shown in FIG. 3, illustrating the state after the first heating process and before the second heating process. FIG. 4 is a diagram showing the manufacturing process of the medical shaft shown in FIG. 3, illustrating the completed state of the secondary heating treatment. FIG. 11 is a cross-sectional view showing a medical shaft according to a third embodiment of the present invention. FIG. 6 is a diagram showing the manufacturing process of the medical shaft shown in FIG. 5, illustrating the state before the first heat treatment. FIG. 6 is a diagram showing the manufacturing process of the medical shaft shown in FIG. 5, illustrating the state after the first heating process and before the second heating process. FIG. 6 is a diagram showing the manufacturing process of the medical shaft shown in FIG. 5, illustrating the completion state of the secondary heating treatment. FIG. 11 is a cross-sectional view showing a medical shaft according to a fourth embodiment of the present invention. FIG. 13 is a cross-sectional view showing a medical shaft according to a fifth embodiment of the present invention. FIG. 13 is a cross-sectional view showing a medical shaft according to a sixth embodiment of the present invention.

Below, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a high-frequency needle 10 as a first embodiment of a medical shaft according to the present invention. The high-frequency needle 10 is a medical instrument that is inserted into the body during treatment of a patient, and is used, for example, to perforate the fossa ovalis of the atrial septum. The high-frequency needle 10 has a structure in which the outer surface of the shaft body 12 is covered with a resin tube 14. In the following explanation, the proximal end (left side in FIG. 1) that is on the practitioner side when in use is referred to as the base end of the high-frequency needle 10, and the distal end (right side in FIG. 1) that is on the patient side is referred to as the tip of the high-frequency needle 10.

The shaft body 12 is a hollow, longitudinal member made of a metal such as stainless steel, and has a lumen 16 extending in the axial direction. It is desirable for the shaft body 12 to have a certain degree of flexibility, and it is preferably capable of being plastically deformed into a curved shape, for example, by the practitioner applying force with his or her hand. The shaft body 12 is composed of a small diameter pipe 18 and a large diameter pipe 20.

The small diameter pipe 18 extends with a generally constant cross-sectional shape, and has generally constant inner and outer diameter dimensions over its entire length. The inner cavity that penetrates the small diameter pipe 18 in the axial direction forms the lumen 16 of the shaft body 12. At the tip of the small diameter pipe 18, a side hole 22 is formed that penetrates part of the peripheral wall at a position a predetermined distance from the tip, and the side hole 22 is connected to the lumen 16.

A tip tip 24 is provided at the tip of the small diameter pipe 18. The tip tip 24 in this embodiment is equipped with a drilling head 26. The drilling head 26 has an outer circumferential surface that protrudes from the distal end of the small diameter pipe 18 and is exposed to the outside. The drilling head 26 has a function of forming a patent hole in body tissue by supplying energy from the outside, and can form a patent hole in the body tissue by cauterizing the body tissue with supplied high-frequency energy, for example. The power for heating the drilling head 26 may be supplied by the small diameter pipe 18 by making the small diameter pipe 18 a conductor, or may be supplied by electrical wiring inserted into the inner cavity of the small diameter pipe 18. In addition, for example, when the small diameter pipe 18 does not reach the base end of the large diameter pipe 20, the small diameter pipe 18 and the large diameter pipe 20 can both be conductors, and power can be supplied to the drilling head 26 by the small diameter pipe 18 and the large diameter pipe 20.

The drilling head 26 is preferably less permeable to X-rays (has high X-ray opacity) than the shaft body 12. The drilling head 26 of this embodiment is made of a metal material such as gold, platinum, platinum iridium, tungsten, or stainless steel, which has excellent visibility under X-ray fluoroscopy, and also functions as a tip marker. A coating of X-ray opaque material can be formed on the surface of the drilling head 26 to ensure or improve visibility under X-ray fluoroscopy.

The outer periphery of the drilling head 26 has a gradually smaller diameter toward the tip. The shape of the drilling head 26 is not particularly limited, but it is desirable for the distal surface to be a curved surface without corners so that it is less likely to get caught when moving through the lumen. For example, it is shaped like a roughly semi-elliptical body of revolution that is convex toward the distal end, and the overall shape is roughly that of a round-nosed bullet.

The drilling head 26 is provided with a cylindrical connection part 28 that extends axially from the base end, and the connection part 28 is inserted and fixed to the tip of the small diameter pipe 18, so that the drilling head 26 is fixedly provided to the tip of the small diameter pipe 18. That is, in this embodiment, the tip tip 24 integrally includes the drilling head 26 and the connection part 28.

The tip tip 24 has a generally cylindrical shape with a through hole 30 extending continuously on the central axis between the drilling head 26 and the connecting portion 28. The inner diameter of the through hole 30 is smaller than the inner diameter of the small diameter pipe 18, and the outer diameter of the connecting portion 28 is smaller than the outer diameter of the base end of the drilling head 26 and is generally the same as the inner diameter of the shaft body 12. It is desirable that the axial length of the connecting portion 28 is longer than the axial length of the drilling head 26, thereby improving the fixing strength of the drilling head 26 to the small diameter pipe 18 and improving the transmission efficiency of the sensation transmitted from the drilling head 26 to the practitioner's hand.

The large diameter pipe 20 has an outer diameter larger than that of the small diameter pipe 18, and an inner diameter that is approximately the same as or slightly larger than that of the small diameter pipe 18. The large diameter pipe 20 has a tapered portion 32 at its tip, where the outer diameter gradually decreases toward the tip. The inner diameter of the large diameter pipe 20 is approximately constant over its entire length, and the tapered portion 32 becomes thinner toward the tip.

The shaft body 12 is formed by inserting the small diameter pipe 18 with the tip 24 attached into the large diameter pipe 20 and fixing the small diameter pipe 18 and the large diameter pipe 20 to each other. The small diameter pipe 18 and the large diameter pipe 20 in the shaft body 12 may be bonded with an adhesive by inserting the small diameter pipe 18 into the inner cavity of the large diameter pipe 20, or may be laser welded. For example, the small diameter pipe 18 is inserted into the inner cavity of the large diameter pipe 20, and the tip of the large diameter pipe 20 is laser welded to the small diameter pipe 18, thereby fixing the small diameter pipe 18 and the large diameter pipe 20 to each other. In addition, a tapered portion 32 is formed at the tip of the large diameter pipe 20 by laser welding the small diameter pipe 18 and the large diameter pipe 20.

The shaft body 12 has a lumen 16 that runs from the proximal end to the distal end. In the shaft body 12, the base end of the small diameter pipe 18 does not reach the base end of the large diameter pipe 20. Therefore, the lumen 16 of the shaft body 12 is composed of the inner cavity of the small diameter pipe 18 and the inner cavity of the large diameter pipe 20. In this way, by arranging the small diameter pipe 18 on the tip side without reaching the base end of the large diameter pipe 20, it is possible to prevent the shaft body 12 from becoming excessively hard, which would reduce bending followability, or the inner diameter of the lumen 16 in the shaft body 12 from becoming small over the entire length.

In the shaft body 12, the small diameter pipe 18 protrudes further toward the tip side than the large diameter pipe 20. In other words, the tip of the large diameter pipe 20 is located closer to the base end than the tip of the small diameter pipe 18. The tip portion of the shaft body 12 composed of the small diameter pipe 18 is the small diameter portion 34, and the base portion of the shaft body 12 composed including the large diameter pipe 20 is the large diameter portion 36.

Between the small diameter portion 34 and the large diameter portion 36, there is a transition portion 37 in which the outer diameter dimension changes. In this embodiment, the axial intermediate portion where the tapered portion 32 of the large diameter pipe 20 in the shaft body 12 is located is a tapered portion 38 in which the outer diameter dimension gradually decreases toward the tip, and the transition portion 37 has a tapered portion 38. In particular, in this embodiment, the tapered portion 38 is provided over the entire axial length between the small diameter portion 34 and the large diameter portion 36, and the entire transition portion 37 is composed of the tapered portion 38. Therefore, in the shaft body 12, the small diameter portion 34 formed by the small diameter pipe 18 has a smaller outer diameter dimension than the large diameter portion 36 formed by the large diameter pipe 20, and the tapered portion 38 is provided between the small diameter portion 34 and the large diameter portion 36. Due to the tapered portion 38, the outer diameter dimension of the shaft body 12 is continuously increased from the small diameter portion 34 to the large diameter portion 36. The side hole 22 of the small diameter pipe 18 is located closer to the tip than the large diameter pipe 20 and is not covered by the large diameter pipe 20.

The difference Δr in the radial dimension between the small diameter portion 34 and the large diameter portion 36 in the shaft body 12 is preferably within the range of 0.1 to 0.8 mm, and more preferably within the range of 0.2 to 0.3 mm. In this embodiment, the difference Δr in the radial dimension between the small diameter portion 34 and the large diameter portion 36 is set by the radial thickness dimension of the large diameter pipe 20.

The inclination angle θ of the tapered portion 38 in the shaft body 12 with respect to the length direction (left-right direction in FIG. 1) is preferably 3°≦θ≦60°. In this embodiment, the inclination angle of the tapered portion 38 is substantially constant throughout the entire length direction. However, the inclination angle of the tapered portion 38 may vary along the length direction, in which case it is preferable that the minimum value of the inclination angle is equal to or greater than the minimum value of the above range, and the maximum value of the inclination angle is equal to or less than the maximum value of the above range.

The outer peripheral surface of the shaft body 12 is covered with a resin tube 14. The resin tube 14 is fitted and fixed to the outer peripheral surface of the shaft body 12, thereby being fixed in position relative to the shaft body 12. The resin tube 14 is provided in the area extending from the small diameter portion 34 of the shaft body 12 through the tapered portion 38 to the large diameter portion 36, and in this embodiment, is provided continuously over substantially the entire length of the shaft body 12 from the tip of the small diameter portion 34 to the base end of the large diameter portion 36. The drilling head 26 of the distal tip 24 is not covered by the resin tube 14 and is exposed further distal than the resin tube 14.

The resin tube 14 is formed from a resin material having heat shrinkability, which means that the resin tube 14 shrinks when heated. The specific material from which the resin tube 14 is formed is not particularly limited, but it may be formed from a fluororesin such as fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF).

The resin tube 14 has a first portion 40 covering the small diameter portion 34 and a second portion 42 covering the large diameter portion 36, which have approximately the same thickness. The resin tube 14 has a third portion 44 covering the tapered portion 38, which has a joint 46 that is thicker than the first portion 40 and/or the second portion 42. In this embodiment, the entire third portion 44 is the joint 46. In other words, the joint 46 is located on the small diameter portion 34 side where the transition portion 37 is located, rather than the end of the large diameter portion 36 in the shaft body 12. The thickness dimension t of the first portion 40 and the second portion 42 is preferably within a range of 0.03 to 0.50 mm, and more preferably within a range of 0.04 to 0.08 mm, taking into account electrical insulation and the like. The maximum thickness dimension T of the third portion 44 is preferably 1.00 mm or less, and more preferably 0.15 mm or less. In addition, the resin tube 14 may have a first portion 40 covering the small diameter portion 34 and a second portion 42 covering the large diameter portion 36 that are different in thickness, in which case either portion may be thicker.

The resin tube 14 is fixed in an overlapping state to the outer circumferential surface of the shaft body 12 at the first portion 40, the second portion 42, and the third portion 44 without using adhesive. The resin tube 14 in this embodiment is fitted and fixed in a tight contact state to the outer circumferential surface of the shaft body 12. As described below, the resin tube 14 is fitted to the outer circumferential surface of the shaft body 12 by thermal shrinkage.

The portion of the outer circumferential surface of the shaft body 12 where the plastic tube 14 is fitted and fixed is preferably roughened. The surface of the shaft body 12 can be suitably roughened by roughening processing such as sand blasting or shot blasting. By carrying out such roughening processing, the resistance of the fitting surface between the shaft body 12 and the plastic tube 14 increases, and the plastic tube 14 is more firmly positioned in the longitudinal direction relative to the shaft body 12.

The high-frequency needle 10, in which the surface of the shaft body 12 is covered with a resin tube 14, can be manufactured, for example, by a manufacturing method including the following steps.

First, a process is carried out to prepare the shaft body 12 having a small diameter portion 34, a large diameter portion 36, and a tapered portion 38. In this embodiment, the small diameter pipe 18 and the large diameter pipe 20 are prepared by drawing, pressing, or the like, and the small diameter pipe 18 is fitted into the large diameter pipe 20 to form the shaft body 12. As described above, the tapered portion 32 of the large diameter pipe 20 can be formed, for example, when laser welding to the small diameter pipe 18.

Next, a process is carried out in which the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are fitted onto the prepared shaft body 12. The small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are both made of resin with heat shrinkability that shrinks when heated, and are independent of each other. In this embodiment, the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are made of the same material. It is desirable that the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are made of a material that can be melted and fused together by a secondary heating process described later. The resin material forming the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 is not particularly limited, but is formed of a fluororesin such as fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.

The inner diameter of the small diameter side heat shrink tube 48 is smaller than the outer diameter of the large diameter portion 36 of the shaft body 12 and larger than the outer diameter of the small diameter portion 34 of the shaft body 12, so that it can be fitted around the small diameter portion 34. The inner diameter of the large diameter side heat shrink tube 50 is larger than the outer diameter of the large diameter portion 36 of the shaft body 12, so that it can be fitted around the large diameter portion 36. In this way, the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 have different diameters before heat shrinking, and the small diameter side heat shrink tube 48 is smaller in diameter than the large diameter side heat shrink tube 50. In this embodiment, the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 have approximately the same thickness in their initial shapes before heat shrinking.

The thickness dimension t1 of the small diameter side heat shrink tube 48 is preferably within the range of 0.03 to 0.50 mm. The thickness dimension t2 of the large diameter side heat shrink tube 50 is preferably within the range of 0.03 to 0.50 mm. In this embodiment, the thickness dimension t1 of the small diameter side heat shrink tube 48 and the thickness dimension t2 of the large diameter side heat shrink tube 50 are approximately the same, but they may be different from each other, in which case either one may be thicker.

Then, the small diameter side heat shrink tube 48 is fitted onto the small diameter portion 34 of the shaft body 12, and the large diameter side heat shrink tube 50 is fitted onto the large diameter portion 36 of the shaft body 12. This large diameter side heat shrink tube 50 extends from the large diameter portion 36 of the shaft body 12 toward the transition portion 37 (tapered portion 38) side, and is arranged so as to overlap the small diameter side heat shrink tube 48 on the transition portion 37 side of the large diameter portion 36 of the shaft body 12. Specifically, the small diameter side heat shrink tube 48 is fitted onto the shaft body 12 from the small diameter portion 34 to the middle of the tapered portion 38, and the large diameter side heat shrink tube 50 is fitted onto the shaft body 12 from the large diameter portion 36 to the middle of the tapered portion 38.

2A, the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 inserted on the shaft body 12 are in an overlapping state in which they overlap in radial projection on the outer periphery of the tapered portion 38. That is, the base end of the small diameter side heat shrink tube 48 is located on the base end side of the tip end of the large diameter side heat shrink tube 50, and the base end of the small diameter side heat shrink tube 48 inserted on the tapered portion 38 is inserted into the inner periphery of the tip end of the large diameter side heat shrink tube 50 inserted on the tapered portion 38, providing an overlapping portion 52. In this embodiment, the overlapping portion 52 of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 is set continuously over almost the entire tapered portion 38.

Next, a primary heating process is performed to shrink the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 by heating. For example, a heating device 54 is disposed on the outer periphery of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 that are fitted onto the shaft body 12, and heated air is blown from the heating device 54 toward the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50. The heating device 54 is movable in the axial direction relative to the shaft body 12 while blowing heated air toward the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50, whereby the entire small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are heated and thermally shrunk.

Then, the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50, which have been warmed by the heated air, are thermally shrunk to a small diameter, and approach the surface of the shaft body 12, as shown in FIG. 2B. For example, the small diameter side heat shrink tube 48 is brought into close contact with the small diameter portion 34 of the shaft body 12, and the large diameter side heat shrink tube 50 is brought into close contact with the large diameter portion 36, by the primary heating process, and the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are positioned relative to the shaft body 12. The small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are independent and do not fuse with each other, and do not have to be in close contact with the tapered portion 38.

After the primary heat treatment is completed, a process is carried out in which a molding heat shrink tube 56 is placed in an externally inserted state around the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 that cover the shaft body 12, as shown in FIG. 2B.

The molding heat shrink tube 56 is a resin tube that has heat shrinkability, that is, shrinkage caused by heating. The molding heat shrink tube 56 is preferably made of a material different from the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50. The molding heat shrink tube 56 is preferably made of a material that does not melt at the heating temperature of the secondary heating process described below. As a result, the molding heat shrink tube 56 does not fuse and integrate with the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 in the secondary heating process described below. The molding heat shrink tube 56 is preferably made of a material that has a higher shrinkage rate due to heating than the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50. For example, polyolefin is used as the material for forming the molding heat shrink tube 56. The molding heat shrink tube 56 is made thicker than the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50, and has improved shape stability during heat shrinkage. The molding heat shrink tube 56, which is inserted around the small diameter heat shrink tube 48 and the large diameter heat shrink tube 50, is positioned in a position where it can be heated by the heating device 54.

The molding heat shrink tube 56 is longer in the longitudinal direction than the tapered portion 38 of the shaft body 12. The molding heat shrink tube 56 is fitted onto the tapered portion 38 of the shaft body 12, and extends beyond the transition portion 37 (tapered portion 38) to both the tip side (small diameter portion 34 side) and the base end side (large diameter portion 36 side), and is also fitted onto the base end of the small diameter portion 34 and the tip end of the large diameter portion 36. Therefore, the entire outer periphery of the overlap portion 52 fitted onto the tapered portion 38 is covered by the molding heat shrink tube 56.

Next, a secondary heating process is performed in which the small diameter side heat shrink tube 48, the large diameter side heat shrink tube 50, and the molding heat shrink tube 56 are heated to a temperature higher than that of the primary heating process by a heating device 54. As a result of the secondary heating process, as shown in FIG. 2C, the overlapping portion 52 of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 melts and fuses together to form a joint 46, and the joint 46 adheres closely to the surface of the tapered portion 38 of the shaft body 12. As a result, the resin tube 14 covering the surface of the shaft body 12 is composed of the integrated small diameter side heat shrink tube 48 and large diameter side heat shrink tube 50. In short, the resin tube 14 is a joint structure in which the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are fused together and joined at the joint 46. After the secondary heat treatment, it is desirable for the small diameter heat shrink tube 48 and the large diameter heat shrink tube 50 to form the resin tube 14 as a single unit without a clear boundary, but for example, the boundary of the molten portion may be visible.

By forming the resin tube 14 using a small diameter heat shrink tube 48 and a large diameter heat shrink tube 50 that have different diameters before heat shrinking, the resin tube 14 can be tightly attached to the outer circumferential surface of the shaft body 12 over its entire length in accordance with the difference in outer diameter dimension between the small diameter portion 34 and the large diameter portion 36 of the shaft body 12. Therefore, the resin tube 14 is fitted into the shaft body 12 over its entire length, covering the surface of the shaft body 12 and fixing its position. In this embodiment, since the surface of the shaft body 12 is roughened, the resin tube 14 is more firmly positioned by being tightly attached to the shaft body 12.

It is desirable that the resin tube 14 (small diameter side heat shrink tube 48 and large diameter side heat shrink tube 50 after the secondary heating process) is not glued or welded to the surface of the shaft body 12, but is fitted and fixed. This avoids adverse effects on the patient caused by the use of adhesives, and allows the small diameter side heat shrink tube 48 and large diameter side heat shrink tube 50 to be fixed to the shaft body 12 without heating them to the point of melting them all the way to their inner surfaces.

The third portion 44 of the resin tube 14 is formed by fusing together the overlapping small-diameter heat-shrinkable tube 48 and large-diameter heat-shrinkable tube 50, and is thicker than the first portion 40 made up of the small-diameter heat-shrinkable tube 48 alone and/or the second portion 42 made up of the large-diameter heat-shrinkable tube 50 alone, and the entire third portion 44 is the joint portion 46. The joint portion 46 is thicker than either the small-diameter heat-shrinkable tube 48 or the large-diameter heat-shrinkable tube 50 before the heat treatment, and in this embodiment, the thickness of the joint portion 46 is thicker than either the small-diameter heat-shrinkable tube 48 or the large-diameter heat-shrinkable tube 50, which have approximately the same thickness. The thick joint portion 46 is located on the outer circumferential surface of the tapered portion 38 of the shaft body 12, and the entire surface of the tapered portion 38 is covered with the joint portion 46.

The thickness dimension of the first portion 40 of the resin tube 14 is less than or equal to the thickness dimension of the small diameter side heat shrink tube 48 before heat shrinkage. The thickness dimension of the second portion 42 of the resin tube 14 is less than or equal to the thickness dimension of the large diameter side heat shrink tube 50 before heat shrinkage. Furthermore, the thickness dimension of the third portion 44 of the resin tube 14 is less than the sum of the thickness dimensions of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 before heat shrinkage.

The molding heat shrink tube 56, which has been heat-shrunk by the secondary heating process, is pressed against the overlapping portion 52 of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50, which are in close contact with the surface of the tapered portion 38, from the outer periphery, as shown in FIG. 2C. The molding heat shrink tube 56 extends beyond the transition portion 37 (tapered portion 38) to the tip and base ends, and is in close contact with the area including both ends of the tapered portion 38, so as to cover the base end of the small diameter portion 34 connected to the tapered portion 38 and the tip end of the large diameter portion 36. Therefore, the entire overlapping portion 52 of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50, which are superimposed on the tapered portion 38, are fused and integrated while maintaining their shape by the contact of the molding heat shrink tube 56, and are molded into a predetermined shape. In this way, by using the molding heat shrink tube 56 that is pressed against the outer circumferential surface of the third portion 44 of the resin tube 14 during the secondary heat treatment, the third portion 44 of the resin tube 14, which is prone to becoming distorted, such as locally convex, due to the overlap between the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50, can be given a smooth surface shape.

After the secondary heat treatment is completed, a process is performed to remove the molding heat shrink tube 56 from the surface of the resin tube 14. This makes it possible to obtain a high-frequency needle 10 in which the surface of the shaft body 12 is covered with the resin tube 14. The molding heat shrink tube 56 is made of a material different from the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 that constitute the resin tube 14, so that it can be easily removed from the resin tube 14 after the secondary heat treatment without being melted and integrated with the resin tube 14 during the secondary heat treatment. The molding heat shrink tube 56 is preferably made of a resin material with a melting point different from that of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50. In addition, the process of removing the molding heat shrink tube 56 from the resin tube 14 is desirably performed after cooling the resin tube 14 and the molding heat shrink tube 56 as necessary.

Since the molding heat shrink tube 56 is removed after molding the resin tube 14, there is greater freedom in selecting the thickness and material than with the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50, and it can be made of a material that has excellent shape stability during heat shrinking, for example. Therefore, by using the molding heat shrink tube 56, the outer peripheral surface shape of the third portion 44 of the resin tube 14 can be stably molded into a smooth, predetermined shape during the secondary heat treatment.

The high-frequency needle 10 obtained in this manner is used, for example, to perforate the fossa ovalis in the atrial septum. That is, the perforation head 26 of the high-frequency needle 10 inserted into the right atrium is pressed against the blocked portion of the foramen ovale (fossa ovalis) in the atrial septum that separates the right and left atria, and the perforation head 26 generates heat due to the supply of high-frequency power, cauterizing the fossa ovalis and forming a specified patent foramen.

In this embodiment, the shaft body 12 is made of a conductive metal, and electricity is passed through the shaft body 12 to the drilling head 26. The outer circumferential surface of the shaft body 12 is covered over substantially the entire length from the base end side of the drilling head 26 with an electrically insulating resin tube 14, preventing loss of electrical energy and the risk of electric shock.

The high-frequency needle 10 is guided to the right atrium by being inserted into a dilator (not shown) that is inserted into the right atrium. The high-frequency needle 10 has a joint 46 at which the resin tube 14 becomes thick, located in the tapered portion 38 of the shaft body 12, so that partial thickening of the resin tube 14 is unlikely to be a problem when inserting the high-frequency needle 10 into the dilator. In particular, because the joint 46 is located in the tapered portion 38, even if the joint 46 is made thick, it is unlikely to lead to an increase in the maximum outer diameter of the high-frequency needle 10, and the thick joint 46 does not form a tip portion that is likely to affect insertability.

In addition, the thick joint 46 is molded into a smooth shape with minimal localized unevenness by the heat shrink tube 56, so there are few problems with it getting caught when inserted into the dilator.

In addition, an operating handle (not shown) may be attached to the proximal end of the shaft body 12. The operating handle is held and operated by the practitioner, and can be used to insert and remove the shaft body 12, to control its circumferential orientation, and to control the degree of bending and deformation. The operating handle may also function as a hub that opens the lumen 16 of the shaft body 12 proximally.

FIG. 3 shows a high-frequency needle 60 as a second embodiment of a medical shaft according to the present invention. The high-frequency needle 60 has a structure in which the outer circumferential surface of the shaft body 12 is covered with a resin tube 62. In the following explanation, the same reference numerals are used in the figure to denote components and parts that are substantially the same as those in the first embodiment, and explanations thereof will be omitted.

The resin tube 62 has a third section 44 that covers the transition section 37 (tapered section 38) of the shaft body 12, and the thickness of the third section 44 changes in the longitudinal direction (left-right direction in FIG. 3), and the portion of the third section 44 that covers the tip side of the tapered section 38 is a joint 64 that is thicker than the portion that covers the base end side of the tapered section 38. In short, in this embodiment, the third section 44 of the resin tube 62 is partially provided with the joint 64 in the longitudinal direction. The longitudinal position of the joint 64 is set on the tip side of the third section 44. The length of the joint 64 is preferably less than half the length of the third section 44 and greater than or equal to ¼ of the length of the third section 44.

The high-frequency needle 60 of this embodiment can be manufactured, for example, through the steps shown in Figures 4A to 4C. That is, in this embodiment as well, first, the small diameter side heat shrink tube 48 is fitted onto the small diameter portion 34 of the shaft body 12, and the large diameter side heat shrink tube 50 is fitted onto the large diameter portion 36 of the shaft body 12. Then, the large diameter side heat shrink tube 50 is extended from the large diameter portion 36 of the shaft body 12 toward the transition portion 37 (tapered portion 38) side, and is arranged so as to overlap the small diameter side heat shrink tube 48 on the transition portion 37 side of the large diameter portion 36 of the shaft body 12. Specifically, as shown in Figure 4A, the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are fitted onto the shaft body 12 prepared in advance. The base end of the small diameter side heat shrink tube 48 is inserted into the inner circumference of the tip portion of the large diameter side heat shrink tube 50. The overlapping portion 66 of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50, which are arranged in an internally and externally inserted state, is arranged on the outer periphery side of the tip portion of the tapered portion 38 of the shaft body 12, and the small diameter side heat shrink tube 48 is not arranged on the outer periphery side of the base end portion of the tapered portion 38.

Next, a primary heat treatment is performed to shrink the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 by heating. The heated small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are thermally shrunk to a small diameter, and approach the surface of the shaft body 12, as shown in FIG. 4B. The primary heat treatment causes the small diameter side heat shrink tube 48 to adhere closely to the small diameter portion 34 of the shaft body 12, and the large diameter side heat shrink tube 50 to adhere closely to the large diameter portion 36, so that the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are positioned relative to the shaft body 12. In the primary heat treatment of this embodiment, the overlapping portions 66 of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 are in independent adhesion without being fused to each other.

After the primary heat treatment is completed, as shown in FIG. 4B, the molding heat shrink tube 56 is placed in an externally inserted state on the shaft body 12 covered with the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50, and a process of performing a secondary heat treatment is performed. The molding heat shrink tube 56 is externally inserted on the tapered portion 38 of the shaft body 12, protrudes beyond the transition portion 37 (tapered portion 38) on both the tip and base ends, and is also externally inserted on the base end of the small diameter portion 34 and the tip end of the large diameter portion 36. Therefore, the overlap portion 66 of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 is located on the inner periphery side of the molding heat shrink tube 56.

The overlapping portion 66 of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 adheres to the surface of the tapered portion 38 of the shaft body 12 by the secondary heat treatment as shown in FIG. 4C, and melts and fuses together to form a thick joint 64. As a result, the resin tube 62 covering the surface of the shaft body 12 is composed of the integrated small diameter side heat shrink tube 48 and large diameter side heat shrink tube 50.

In this embodiment, the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 overlap only at the tip of the tapered portion 38 of the shaft body 12, so the joint 64 of the resin tube 62 is formed only in the area that covers the tip of the tapered portion 38.

As shown in this embodiment, the overlapping portion of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 does not necessarily have to be set over the entire tapered portion 38 of the shaft body 12, but may be set partially in the length direction. According to this embodiment, the range of the joint 64 in the third portion 44 of the resin tube 62 can be limited to the tip side, and the third portion 44 of the resin tube 62 covering the tapered portion 38 can be made thin-walled on the base end side where the diameter is large.

The lengthwise proportion of the joint 64 in the third portion 44 is not particularly limited. For example, the length dimension of the joint 64 may be greater than half the length dimension of the third portion 44, or less than 1/4 the length dimension of the third portion 44.

Next, FIG. 5 shows a high-frequency needle 70 as a third embodiment of a medical shaft according to the present invention. In this embodiment, the high-frequency needle 70 also has a structure in which the outer circumferential surface of the shaft body 72 is covered with a resin tube 74.

The shaft body 72 of this embodiment is a hollow or solid rod-shaped member made of a metal such as stainless steel, and is configured to include a small diameter rod portion 78 constituting the small diameter portion 76 and a large diameter rod portion 82 constituting the large diameter portion 80. Although not shown, the tip tip 24 is fixed to the tip of the small diameter rod portion 78 (the right end in FIG. 5), and the shaft body 72 (the small diameter rod portion 78 and the large diameter rod portion 82) are made conductive, and power is supplied to the tip tip 24 (the drilling head portion 26), making it possible to cauterize body tissue. It is preferable that the shaft body 72 has a certain degree of flexibility, for example, by setting the outer diameter dimensions of the small diameter rod portion 78 and/or the large diameter rod portion 82 to be somewhat small. In addition, in the drawings shown in the following description, the shaft body 72 is shown in its external shape.

The large diameter rod portion 82 and the small diameter rod portion 78 each have, for example, an annular or circular cross section and have a substantially constant outer diameter dimension over the entire length. The outer diameter dimension of the large diameter rod portion 82 is larger than the outer diameter dimension of the small diameter rod portion 78. Such a shaft body 72 can be formed, for example, by fixing the small diameter rod portion 78 to the end of the large diameter rod portion 82 by laser welding or the like. Note that, for example, when the shaft body is a pipe having a lumen (inner cavity) as in the above embodiment, the large diameter portion (large diameter pipe) and the small diameter portion (small diameter pipe) may be formed in a mutually connected state by performing a crimping process (diameter reduction process) in the radial direction on one axial side of a metal raw tube having a substantially constant outer diameter dimension and inner diameter dimension.

A transition portion 84 in which the outer diameter dimension changes is provided between the small diameter portion 76 and the large diameter portion 80. In this embodiment, the small diameter rod portion 78 is directly connected to the end face of the large diameter rod portion 82, and an annular stepped surface 86 that extends in a direction perpendicular to the axial direction is formed around the small diameter rod portion 78 at the end face of the large diameter rod portion 82. Therefore, including the stepped surface 86, a stepped portion 88 in which the outer diameter dimension changes in a step shape is formed between the small diameter portion 76 and the large diameter portion 80, and the transition portion 84 has the stepped portion 88.

As in the first and second embodiments, the resin tube 74 covering the outer peripheral surface of the shaft body 72 has a first portion 90 covering the small diameter portion 76 and a second portion 92 covering the large diameter portion 80 that are approximately the same thickness. The resin tube 74 also has a joint portion 96 in which a third portion 94 covering the stepped portion 88, which is the transition portion 84, is thicker than the first portion 90 and/or the second portion 92. That is, the joint portion 96, which has a thickness dimension greater than either the small diameter side heat shrink tube 98 or the large diameter side heat shrink tube 100, is located on the small diameter portion 76 side where the transition portion 84 is located, rather than the end of the large diameter portion 80 of the shaft body 72. In this embodiment, the thickness dimension of the third portion 94 (joint 96) is greater than the thickness dimension of either the small diameter side heat shrink tube 98 or the large diameter side heat shrink tube 100, which are both approximately the same thickness dimension, and the joint 96 is located in a position that covers the end of the small diameter portion 76 on the stepped portion 88 side of the shaft body 72.

The high-frequency needle 70, in which the surface of the shaft body 72 is covered with a resin tube 74, can be manufactured, for example, by a manufacturing method including the following steps.

First, a process is carried out to prepare the shaft body 72 having a small diameter portion 76, a large diameter portion 80, and a transition portion 84 (step portion 88). Note that the method for forming the shaft body 72 is not limited.

Next, a process is carried out in which the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 are fitted around the prepared shaft body 72. That is, the small diameter side heat shrink tube 98 is fitted around the small diameter portion 76 of the shaft body 72, and the large diameter side heat shrink tube 100 is fitted around the large diameter portion 80 of the shaft body 72. The large diameter side heat shrink tube 100 is extended from the large diameter portion 80 of the shaft body 72 toward the change portion 84 side, and is arranged so as to overlap the small diameter side heat shrink tube 98 on the change portion 84 side of the large diameter portion 80 of the shaft body 72. In other words, the large diameter side heat shrink tube 100 is extended from the large diameter portion 80 of the shaft body 72 beyond the stepped portion 88, and is arranged so as to overlap the small diameter side heat shrink tube 98 at the small diameter portion 76. For example, the inner diameter of the small diameter heat shrink tube 98 is smaller than the outer diameter of the large diameter portion 80 of the shaft body 72, and the small diameter heat shrink tube 98 can be inserted onto the small diameter portion 76 so that its end abuts against the stepped surface 86 of the shaft body 72.

Specifically, as shown in FIG. 6A, the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 fitted onto the shaft body 72 are overlapped in radial projection on the outer periphery of the small diameter portion 76 side where the transition portion 84 is located, rather than the end of the large diameter portion 80 of the shaft body 72. That is, the base end of the small diameter side heat shrink tube 98 is located on the base end side of the tip of the large diameter side heat shrink tube 100, and the base end of the small diameter side heat shrink tube 98 is inserted into the inner circumference of the tip of the large diameter side heat shrink tube 100 to provide an overlap portion 102. In this embodiment, the overlap portion 102 of the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 is set continuously with a certain axial dimension from the transition portion 84 (step portion 88) toward the tip.

Next, a step of performing a primary heating process is performed to shrink the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 by heating. The small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 can be heated by the heating device 54, as in the first and second embodiments. The small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 heated by the heating device 54 are thermally shrunk to a small diameter, and approach the surface of the shaft body 72, as shown in FIG. 6B. For example, the small diameter side heat shrink tube 98 is in close contact with the small diameter portion 76 of the shaft body 72 by the primary heating process, and the large diameter side heat shrink tube 100 is in close contact with the large diameter portion 80 of the shaft body 72, so that the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 are positioned relative to the shaft body 72. The small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 are radially separated from each other at the overlap portion 102.

After the first heat treatment is completed, as shown in FIG. 6B, a process is performed in which a molding heat shrink tube 104 is placed in an externally inserted state on the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 covering the shaft body 72. This molding heat shrink tube 104 is externally inserted on the transition portion 84 (step portion 88) of the shaft body 72, and extends beyond the transition portion 84 (step portion 88) to both the tip side and the base end side, and is also externally inserted on the base end of the small diameter portion 76 and the tip end of the large diameter portion 80. In this embodiment, the molding heat shrink tube 104 has an axial dimension larger than the overlap portion 102 between the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100, and the entire overlap portion 102 is covered by the molding heat shrink tube 104.

Next, a secondary heating process is carried out in which the small diameter side heat shrink tube 98, the large diameter side heat shrink tube 100, and the molding heat shrink tube 104 are heated to a temperature higher than that of the primary heating process by the heating device 54. As a result of the secondary heating process, as shown in FIG. 6C, the overlapping portion 102 of the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 melts and fuses together to form a joint 96, and the joint 96 covers and adheres to the surface of the end of the stepped portion 88 side of the small diameter portion 76 in the shaft main body 72. As a result, the resin tube 74 covering the surface of the shaft main body 72 is composed of the integrated small diameter side heat shrink tube 98 and large diameter side heat shrink tube 100.

The molding heat shrink tube 104, which has been heat shrunk by the secondary heating process, is pressed against the overlapping portion 102 of the small diameter heat shrink tube 98 and the large diameter heat shrink tube 100 from the outer periphery, as shown in FIG. 6C. The molding heat shrink tube 104 extends beyond the transition portion 84 (stepped portion 88) to the tip and base ends, and is in close contact with the shaft body 72 so as to cover the base end of the small diameter portion 76 and the tip end of the large diameter portion 80. In this embodiment, the molding heat shrink tube 104 is provided to cover the entire overlapping portion 102, so that the entire overlapping portion 102 is fused and integrated while maintaining its shape by the contact of the molding heat shrink tube 104, and is molded into a predetermined shape.

After the secondary heating process is completed, a process is carried out in which the molding heat shrink tube 104 is removed from the surface of the resin tube 74. This makes it possible to obtain a high-frequency needle 70 in which the surface of the shaft body 72 is covered with the resin tube 74.

Even in the high-frequency needle 70 of this embodiment having the above structure, the joint 96 formed by overlapping and joining the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 is provided on the small diameter part 76 side where the change part 84 is located, rather than the end of the large diameter part 80 of the shaft body 72, so that the increase in diameter due to the formation of the joint 96 is suppressed, and the same effect as in the first and second embodiments can be achieved. In particular, even when a stepped change part 84 (stepped part 88) is provided between the small diameter part 76 and the large diameter part 80 as in this embodiment, the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 are smoothly connected on the outer circumferential surface of the resin tube 74. As a result, even when the high-frequency needle 70 is inserted into a dilator or the like, the risk of the high-frequency needle 70 getting caught can be reduced.

Next, FIG. 7 shows a high-frequency needle 110 as a fourth embodiment of a medical shaft according to the present invention. Also, FIG. 8 shows a high-frequency needle 112 as a fifth embodiment of a medical shaft according to the present invention. Both of these are the third embodiment of the medical shaft (high-frequency needle 70) in which the outer circumferential corners of the end of the large diameter portion 80 of the shaft body 72 on the stepped portion 88 side are chamfered. In the high-frequency needle 110 shown in FIG. 7, the outer circumferential corners are chamfered in a C-shape, and in the high-frequency needle 112 shown in FIG. 8, the outer circumferential corners are chamfered in an R-shape.

Therefore, in the high-frequency needle 110 of the fourth embodiment, an annular tapered surface 114 that gradually becomes smaller in diameter toward the tip side (small diameter portion 76 side) is provided at the outer circumferential end of the end portion of the large diameter portion 80 on the stepped portion 113 side, and the tapered surface 114 is provided continuously from the outer circumferential end of the stepped surface 86 to the base end side. In this case, the transition portion 116 (stepped portion 113) is formed by including the tapered surface 114 in addition to the stepped surface 86, and the base end of the tapered surface 114 (the outer circumferential end of the tapered surface 114, point P1 in Figure 7) can be understood as the end portion of the large diameter portion 80 in the shaft body 72. A joint 118 having a thickness greater than both the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 is provided to cover the transition portion 116 (tapered surface 114 and stepped surface 86), and the joint 118 is located closer to the small diameter portion 76 where the transition portion 116 is located than the end (P1) of the large diameter portion 80 of the shaft body 72.

Similarly, in the high-frequency needle 112 of the fifth embodiment, an annular curved surface 120 that gradually becomes smaller in diameter toward the tip side (small diameter portion 76 side) is provided at the outer circumferential end of the end portion of the large diameter portion 80 on the stepped portion 119 side, and the curved surface 120 is provided continuously from the outer circumferential end of the stepped surface 86 to the base end side. In this case, the transition portion 122 (stepped portion 119) is formed by including the curved surface 120 in addition to the stepped surface 86, and the base end of the curved surface 120 (the outer circumferential end of the curved surface 120, point P2 in Figure 8) can be understood as the end portion of the large diameter portion 80 in the shaft body 72. A joint 124 having a thickness greater than both the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 is provided to cover the transition portion 122 (the curved surface 120 and the stepped surface 86), and the joint 124 is located closer to the small diameter portion 76 where the transition portion 122 is located than the end (P2) of the large diameter portion 80 of the shaft body 72.

The high-frequency needle 110 in the fourth embodiment and the high-frequency needle 112 in the fifth embodiment, which are constructed as described above, are simply the high-frequency needle 70 in the third embodiment, in which the outer circumferential corners of the end of the large diameter portion 80 on the stepped portion 88 side are chamfered, and therefore can exhibit the same effect as the high-frequency needle 70 in the third embodiment. In particular, by chamfering the outer circumferential corners of the end of the large diameter portion 80 on the stepped portion 88 side, the angularity of the outer circumferential corners can be eliminated, and the

joints

118, 124 can be made thicker, which can reduce the risk that, for example, the angularity of the outer circumferential corners will get caught when a dilator or the like is inserted, or that the outer circumferential corners will break through the resin tube 74 and protrude when the high-

frequency needles

110, 112 are bent. The high-frequency needle 110 in the fourth embodiment and the high-frequency needle 112 in the fifth embodiment can be manufactured by the same manufacturing method as the high-frequency needle 70 in the third embodiment.

Next, FIG. 9 shows a high-frequency needle 130 as a sixth embodiment of the medical shaft according to the present invention. In this high-frequency needle 130, an intermediate ring 132 having an outer diameter smaller than that of the large diameter portion 80 is attached in an extrapolated state to the end of the small diameter portion 76 of the shaft body 72 on the stepped portion 88 side in the medical shaft (high-frequency needle 70) of the third embodiment. That is, in this embodiment, the change portion 134 in which the outer diameter dimension changes between the small diameter portion 76 and the large diameter portion 80 is configured to include the intermediate ring 132 in addition to the stepped surface 86, and has a stepped portion 136 in which the outer diameter dimension changes in multiple steps between the small diameter portion 76 and the large diameter portion 80. In particular, in this embodiment, the base end side end face of the intermediate ring 132 abuts against the stepped surface 86, so that no gap is provided between the large diameter portion 80 and the intermediate ring 132 in the axial direction.

A joint 138 having a thickness greater than either the small diameter side heat shrink tube 98 or the large diameter side heat shrink tube 100 is provided to cover the transition portion 134 (step portion 136). In this embodiment, the thickness of the joint 138 is greater than either the small diameter side heat shrink tube 98 or the large diameter side heat shrink tube 100, which have approximately the same thickness. The joint 138 is located closer to the small diameter portion 76, where the transition portion 134 is located, than the end of the large diameter portion 80 of the shaft body 72. As a result, the shaft body 72, including the intermediate ring 132, is covered with the resin tube 74.

Therefore, the high-frequency needle 130 in this embodiment can also achieve the same effect as the high-frequency needle 70 described in the third embodiment. In particular, even if the difference between the outer diameter dimension of the small diameter portion 76 and the outer diameter dimension of the large diameter portion 80 is relatively large, by providing an intermediate ring 132 having an outer diameter dimension intermediate between the small diameter portion 76 and the large diameter portion 80 as in this embodiment, a stepped portion 136 in which the outer diameter dimension changes in multiple steps can be formed as the changing portion 134. This prevents the outer diameter dimension of the resin tube 74 from suddenly changing between the small diameter portion 76 and the large diameter portion 80, and allows the small diameter side heat shrink tube 98 and the large diameter side heat shrink tube 100 to be connected relatively gently on the outer circumferential surface of the resin tube 74, and prevents the thickness dimension of the resin tube 74 from becoming locally small. As a result, even when the high-frequency needle 130 is inserted into a dilator or the like, the stepped portion 136 can prevent the high-frequency needle 130 from getting caught on the dilator or the like.

The high-frequency needle 130 of this embodiment can be basically manufactured by the same manufacturing method as the high-frequency needle 70 of the third embodiment. For example, when the small-diameter heat shrink tube 98 is inserted around the small-diameter portion 76, the small-diameter heat shrink tube 98 may be inserted around the intermediate ring 132 in addition to the small-diameter portion 76. Alternatively, the small-diameter heat shrink tube 98 may be inserted around the small-diameter portion 76 on the tip side of the intermediate ring 132, so that the base end face of the small-diameter heat shrink tube 98 abuts on the tip end face of the intermediate ring 132. In either case, when the large-diameter heat shrink tube 100 is inserted around the large-diameter portion 80, it is extended from the large-diameter portion 80 to the change portion 134 side, and is arranged in an overlapping state with the base end portion of the small-diameter heat shrink tube 98 on the change portion 134 side of the large-diameter portion 80 (for example, inserted around the outer circumferential surface of the intermediate ring 132 or at the tip side of the intermediate ring 132).

Although the embodiments of the present invention have been described above in detail, the present invention is not limited to those specific descriptions. For example, in the above embodiment, a high-frequency needle is shown as an example of a medical shaft, and a resin tube is provided as an insulating coating layer when electricity is applied, but the resin tube is not necessarily limited to one that constitutes the insulating coating layer. The resin tube can also be used, for example, as a protective layer that protects the surface of the shaft body. In addition, the medical shaft is not limited to one used in treatment of the human body, and may be one used, for example, in treatment of animals other than humans.

The shaft body is not limited to a structure that combines a small diameter pipe 18 and a large diameter pipe 20, such as the shaft body 12 shown in the first and second embodiments, and may be constructed as a single member, for example. The shaft body may be a solid rod, and the material is not limited. The shaft body is not limited to a structure that includes a tip 24.

In the first and second embodiments, an example was shown in which the tapered portion 38 of the shaft body 12 is formed by melting when the tip portion of the large diameter pipe 20 is laser welded to the small diameter pipe 18. However, the tapered portion 38 of the shaft body 12 can also be formed from a brazing material separate from the large diameter pipe 20, for example, when the small diameter pipe 18 and the tip side of the large diameter pipe 20 are fixed by brazing.

In the first embodiment, the joint 46 of the resin tube 14 formed by the overlap portion 52 of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 may cover the entire tapered portion 38 including both longitudinal ends of the tapered portion 38 of the shaft body 12, or may cover only one longitudinal end of the tapered portion 38. The overlap portion 52 may be positioned in an extrapolated state in an intermediate portion away from both longitudinal ends of the tapered portion 38, and the joint 46 of the resin tube 14 may be provided to cover the intermediate portion of the tapered portion 38. By providing the joint 46 of the resin tube 14 away from the large diameter end of the tapered portion 38 of the shaft body 12, it is possible to avoid the large diameter portion 36 from becoming large near the tip. In addition, by locating the joint 46 of the resin tube 14 away from the small diameter end of the tapered portion 38 of the shaft body 12, it is possible to prevent the small diameter portion 34 from becoming large near the base end.

In the above embodiment, a manufacturing method was described in which the

resin tubes

14, 74 that cover the

shaft bodies

12, 72 are formed by a primary heat treatment and a secondary heat treatment. However, for example, the small diameter side heat shrink

tube

48, 98, the large diameter side heat shrink

tube

50, 100, and the molding heat shrink

tube

56, 104 may be placed in an externally inserted state on the

shaft bodies

12, 72, respectively, and the

resin tubes

14, 74 may be formed by a single heat treatment. The

resin tubes

14, 74 may also be formed by three or more heat treatments.

In the above embodiment, the small diameter side heat shrink

tube

48, 98 and the large diameter side heat shrink

tube

50, 100 are fitted and fixed without being bonded or welded to the outer circumferential surface of the

shaft body

12, 72, but at least one of the small diameter side heat shrink

tube

48, 98 and the large diameter side heat shrink

tube

50, 100 may be bonded or welded to the outer circumferential surface of the

shaft body

12, 72. For example, in the first embodiment, when the tip portion of the shaft body 12 is curved, at least one of the small diameter side heat shrink tube 48 and the large diameter side heat shrink tube 50 is bonded or welded to the shaft body 12 in the small diameter portion 34 and/or the tapered portion 38 and its vicinity. This makes it possible to more advantageously prevent the heat shrink tube 48 (50) from shifting relative to the shaft body 12 when the tip portion of the shaft body 12 is curved.

In the first embodiment, the heat shrink tube 56 for molding is used to control the shape of the overlapping portion 52 of the heat shrink

tubes

48, 50 that cover the tapered portion 38, and therefore the heat shrink tube 56 for molding does not need to be sufficiently heat shrunk at the portion where it is inserted into the small diameter portion 34 or the large diameter portion 36 of the shaft body 12. Depending on the material and heating conditions of the heat shrink

tubes

48, 50, and the inclination angle of the tapered portion 38 of the shaft body 12, it is also possible to heat shrink mold the joint 46 without using the heat shrink tube for molding 56. Alternatively, when heat shrink molding the joint 46, it is also possible to use a diameter-reducing drawing mold instead of the heat shrink tube for molding. This is the same in the second to sixth embodiments.

Furthermore, the specific shape of the change part of the shaft body is not limited to the above-mentioned embodiments. For example, in the fourth and fifth embodiments, the convex corner part on the outer circumferential side (large diameter side) of the stepped surface 86 of the shaft body 72 is chamfered (tapered surface 114 or curved surface 120), but in addition to or instead of that, the concave corner part on the inner circumferential side (small diameter side) of the stepped surface 86 may be chamfered. That is, at the base end of the small diameter part, it is also possible to provide a tapered surface or curved surface that widens toward the outer circumferential side as it approaches the base end side (stepped surface 86 side). Furthermore, in addition to the chamfered shape (tapered surface 114 or curved surface 120) in the fourth and fifth embodiments, it is also possible to adopt the intermediate ring 132 of the sixth embodiment, and it is also possible to adopt an intermediate ring whose outer diameter dimension changes in multiple stages or a single or multiple intermediate ring whose outer diameter dimension changes in a tapered manner. In the sixth embodiment, the intermediate ring 132 was attached in an externally inserted state to the end of the small diameter portion 76 on the stepped portion 88 side, but the intermediate ring may be provided at a position slightly spaced axially from the large diameter portion, and the base end face of the intermediate ring and the stepped surface may not be in contact.

Furthermore, for example, in the first embodiment, before the primary heat treatment, the small diameter side heat shrink tube 48 is fitted from the small diameter portion 34 to the tapered portion 38, and the large diameter side heat shrink tube 50 is fitted from the large diameter portion 36 to the tapered portion 38, and these small diameter side heat shrink tube 48 and large diameter side heat shrink tube 50 are overlapped at the tapered portion 38, but this is not limited to the above embodiment. For example, before the primary heat treatment, an intermediate tube having a diameter dimension intermediate between the small diameter side heat shrink tube and the large diameter side heat shrink tube may be used, and the small diameter side heat shrink tube or the large diameter side heat shrink tube may be configured including the intermediate tube. Such an intermediate tube is disposed in the tapered portion 38, overlapping and heat-welding the large-diameter heat-shrinkable tube at one axial end, and overlapping and heat-welding the small-diameter heat-shrinkable tube at the other axial end. This type of configuration makes it possible to advantageously deal with cases where the diameter change in the tapered portion 38 is large or the axial length is long.

In other words, the small diameter side heat shrink tube and/or the large diameter side heat shrink tube of the present invention do not each need to be a single tube, but may each be comprised of two or more tubes with different diameter dimensions, a tube covering the small diameter portion or the large diameter portion, and a tube covering the transition portion.

Furthermore, in the above embodiment, the thickness dimension of the

joints

46, 64, 96, 118, 124, 138 was larger than the thickness dimension of each of the small diameter side heat shrink

tube

48, 98 and the large diameter side heat shrink

tube

50, 100, but this is not limited to this embodiment. For example, the small diameter side heat shrink tube and the large diameter side heat shrink tube may have different thickness dimensions. In particular, when the transition portion is configured by a stepped portion as shown in FIG. 6A, and the large diameter side heat shrink tube (e.g., the large diameter side heat shrink tube 100 in FIG. 6A) has a larger thickness dimension than the small diameter side heat shrink tube (e.g., the small diameter side heat shrink tube 98 in FIG. 6A), depending on the step height of the stepped portion, the thickness dimension of the joint (e.g., the joint 96 in FIG. 6C) is larger than the thickness dimension of the small diameter side heat shrink tube, but it is also assumed that the thickness dimension of the joint (e.g., the joint 96 in FIG. 6C) may become smaller than the thickness dimension of the large diameter side heat shrink tube due to melting and flowing of the large diameter side heat shrink tube.

10 High-frequency needle (medical shaft, first embodiment)
12 Shaft body 14 Resin tube 16 Lumen 18 Small diameter pipe 20 Large diameter pipe 22 Side hole 24 Distal tip 26 Drilling head 28 Connection portion 30 Through hole 32 Tapered portion 34 Small diameter portion 36 Large diameter portion 37 Transition portion 38 Tapered portion 40 First portion 42 Second portion 44 Third portion 46 Joint portion 48 Small diameter side heat shrink tube 50 Large diameter side heat shrink tube 52 Overlap portion 54 Heating device 56 Molding heat shrink tube 60 High frequency needle (medical shaft, second embodiment)
62 Resin tube 64 Joint portion 66 Overlap portion 70 High-frequency needle (medical shaft, third embodiment)
72 Shaft body 74 Resin tube 76 Small diameter portion 78 Small diameter rod portion 80 Large diameter portion 82 Large diameter rod portion 84 Transition portion 86 Step surface 88 Step portion 90 First portion 92 Second portion 94 Third portion 96 Joint portion 98 Small diameter side heat shrink tube 100 Large diameter side heat shrink tube 102 Overlap portion 104 Molding heat shrink tube 110 High frequency needle (medical shaft, fourth embodiment)
112 High frequency needle (medical shaft, fifth embodiment)
113 Stepped portion 114 Tapered surface 116 Changed portion 118 Joint portion 119 Stepped portion 120 Curved surface 122 Changed portion 124 Joint portion 130 High-frequency needle (medical shaft, sixth embodiment)
132 Intermediate ring 134 Transition portion 136 Step portion 138 Joint portion

Claims

A medical shaft that is inserted into the body of an animal during treatment,
The shaft body has a small diameter portion and a large diameter portion whose outer diameter dimension varies in the length direction, and a transition portion in which the outer diameter dimension varies is provided between the small diameter portion and the large diameter portion.
The shaft body is covered in a longitudinal direction from the small diameter portion through the transition portion to the large diameter portion with a resin tube,
the resin tube is a joint structure in which a small diameter side heat shrinkable tube covering the small diameter portion and a large diameter side heat shrinkable tube covering the large diameter portion are joined together,
A medical shaft in which a joint is provided in an area where the smaller thickness heat shrink tube of the small diameter side heat shrink tube and the large diameter side heat shrink tube is arranged, and has a thickness dimension larger than that of the smaller thickness heat shrink tube, and is positioned on the small diameter portion side where the change portion is located, rather than the end of the large diameter portion of the shaft body.
the transition portion of the shaft body has a tapered portion in which an outer diameter dimension changes in a longitudinal direction between the small diameter portion and the large diameter portion,
2. The medical shaft according to claim 1, wherein the joint portion of the resin tube is positioned at a portion covering the tapered portion.
the transition portion of the shaft body has a step portion in which an outer diameter dimension changes stepwise between the small diameter portion and the large diameter portion,
2. The medical shaft according to claim 1, wherein the joint portion of the resin tube is located at a portion covering the end portion of the small diameter portion of the shaft body on the stepped portion side.
A medical shaft that is inserted into the body of an animal during treatment,
The shaft body has a small diameter portion and a large diameter portion whose outer diameter dimension varies in the length direction, and a transition portion in which the outer diameter dimension varies is provided between the small diameter portion and the large diameter portion.
The shaft body is covered in a longitudinal direction from the small diameter portion through the transition portion to the large diameter portion with a resin tube,
the resin tube is a joint structure in which a small diameter side heat shrinkable tube covering the small diameter portion and a large diameter side heat shrinkable tube covering the large diameter portion are joined together,
A medical shaft in which the small diameter side heat shrink tube and the large diameter side heat shrink tube are overlapped and joined to each other, located on the small diameter side of the shaft body, closer to the small diameter portion where the transition portion is located, than the end of the large diameter portion.
the transition portion of the shaft body has a tapered portion in which an outer diameter dimension changes in a longitudinal direction between the small diameter portion and the large diameter portion,
5. The medical shaft according to claim 4, wherein the small diameter heat shrinkable tube and the large diameter heat shrinkable tube are overlapped and joined to each other at a portion covering the tapered portion of the shaft body.
the transition portion of the shaft body has a step portion in which an outer diameter dimension changes stepwise between the small diameter portion and the large diameter portion,
5. The medical shaft according to claim 4, wherein the small diameter side heat shrink tube and the large diameter side heat shrink tube are overlapped and joined to each other at a portion covering the end of the small diameter portion of the shaft body on the stepped portion side.
The medical shaft according to claim 3 or 6, wherein the outer circumferential corner of the end of the large diameter portion of the shaft body on the stepped portion side is chamfered.
The medical shaft according to claim 3 or 6, in which an intermediate ring having an outer diameter smaller than that of the large diameter portion is attached in an externally inserted state to the end of the small diameter portion of the shaft body on the stepped portion side, and the shaft body including the intermediate ring is covered with the resin tube.
The medical shaft according to any one of claims 1 to 6, wherein the resin tube is fixed to the shaft body in an overlapping state without using adhesive.
The medical shaft according to any one of claims 1 to 6, wherein the shaft body is made of metal.
The medical shaft according to claim 10, wherein the surface of the shaft body is roughened.
The medical shaft according to claim 2 or 5, wherein the thickness dimension of the resin tube is within the range of 0.03 to 0.50 mm at the portion covering the small diameter portion and the large diameter portion of the shaft body, and the maximum thickness dimension at the joint covering the tapered portion is 1.00 mm or less.
The medical shaft according to any one of claims 1 to 6, wherein the difference in radius between the small diameter portion and the large diameter portion of the shaft body is within the range of 0.1 to 0.8 mm.
The medical shaft according to any one of claims 1 to 6, wherein the small diameter heat shrink tube and the large diameter heat shrink tube are fused together and joined together in an integrated state in the resin tube.
The medical shaft according to any one of claims 1 to 6, in which the small diameter side heat shrink tube and the large diameter side heat shrink tube are made of the same material.
A method for manufacturing a medical shaft to be inserted into the body of an animal during treatment, comprising the steps of:
A step of preparing a shaft body having a small diameter portion and a large diameter portion whose outer diameter dimension varies in a length direction, and a transition portion between the small diameter portion and the large diameter portion where the outer diameter dimension varies;
a step of fitting a small diameter side heat shrink tube onto the small diameter portion of the shaft body, fitting a large diameter side heat shrink tube onto the large diameter portion of the shaft body, and extending the large diameter side heat shrink tube from the large diameter portion of the shaft body toward the transition portion and overlapping the small diameter side heat shrink tube on the transition portion side of the large diameter portion of the shaft body;
a step of covering an outer periphery of an overlapping portion between the small diameter side heat shrink tube and the large diameter side heat shrink tube that are fitted onto the shaft body with a molding heat shrink tube;
a step of thermally shrinking the molding heat shrink tube by a heating process to bring the tube into contact with the outer peripheral surfaces of the overlapping portions of the small diameter side heat shrink tube and the large diameter side heat shrink tube, thereby maintaining the shape of the overlapping portions, and thermally shrinking the small diameter side heat shrink tube and the large diameter side heat shrink tube by the heating process to bring them into close contact with the shaft main body;
and removing the heat shrinkable tube after the heat treatment is completed.
the transition portion of the shaft body has a tapered portion in which an outer diameter dimension changes in a longitudinal direction between the small diameter portion and the large diameter portion,
The method for manufacturing a medical shaft according to claim 16, wherein, during the heat treatment, the small diameter side heat shrink tube and the large diameter side heat shrink tube are arranged to overlap each other at the tapered portion of the shaft body.
the transition portion of the shaft body has a step portion in which an outer diameter dimension changes stepwise between the small diameter portion and the large diameter portion,
17. The method for manufacturing a medical shaft according to claim 16, wherein during the heat treatment, the large diameter side heat shrink tube is extended from the large diameter portion of the shaft body beyond the stepped portion and is positioned so as to overlap the small diameter side heat shrink tube in the small diameter portion.
The small diameter side heat shrinkable tube and the large diameter side heat shrinkable tube are made of materials that melt with each other by the heat treatment,
The method for manufacturing a medical shaft according to any one of claims 16 to 18, wherein the molding heat shrink tube is made of a material that does not melt against the small diameter side heat shrink tube and the large diameter side heat shrink tube by the heat treatment.
The method for manufacturing a medical shaft according to claim 17, wherein the inclination angle of the tapered portion of the shaft body is within the range of 3 to 60 degrees.
The method for manufacturing a medical shaft according to any one of claims 16 to 18, wherein the molding heat shrink tube extends from the transition portion of the shaft body to the small diameter portion and the large diameter portion in the longitudinal direction of the shaft body.
The method for manufacturing a medical shaft according to any one of claims 16 to 18, wherein the small diameter heat shrink tube and the large diameter heat shrink tube are fixed in an overlapping state to the outer circumferential surface of the shaft body without being glued or welded over the entire length.