JP7744388B2 - hollow stranded wire - Google Patents

Description

This specification discloses hollow stranded wire suitable for medical devices, etc.

Medical devices inserted into body cavities, such as guidewires, require flexibility, responsiveness, torque transmission, pushability, and other characteristics. JP 2019-107326 A discloses a hollow stranded wire suitable for medical devices.

JP 2019-107326 A

In medical devices that use conventional hollow stranded wire, torque transmission is insufficient. The applicant's intention is to provide a hollow stranded wire that can contribute to the torque transmission of various devices, including medical devices.

The hollow stranded wire disclosed in this specification has a first layer formed by twisting three or more first wires, and a second layer formed by twisting three or more second wires and located on the outside or inside of the first layer. The cross-sectional shape of each first wire is non-circular, including a major axis and a minor axis. This major axis is inclined relative to the longitudinal direction of the hollow stranded wire. In the longitudinal direction of the hollow stranded wire, the position of a front first wire overlaps the position of a rear first wire adjacent to this front first wire.

When one end of this hollow stranded wire is rotated, there is little time lag in rotation. Devices using this hollow stranded wire have excellent torque transmission capabilities.

FIG. 1 is a front view showing a part of a hollow stranded wire according to one embodiment. FIG. 2 is a longitudinal cross-sectional view of the hollow stranded wire of FIG. FIG. 3 is an enlarged cross-sectional view taken along line III-III in FIG. 4 is a perspective view showing a part of a first strand of the hollow stranded wire of FIG. 1. FIG. FIG. 5 is an enlarged cross-sectional view showing the first wire of FIG. FIG. 6 is an enlarged view showing a part of the hollow stranded wire of FIG. FIG. 7 is a cross-sectional view showing a part of a hollow stranded wire according to another embodiment. FIG. 8 is a front view showing a part of a hollow stranded wire according to still another embodiment. FIG. 9 is an enlarged cross-sectional view showing a part of the hollow stranded wire of FIG. FIG. 10 is a perspective view showing an apparatus for evaluating the torque transmission property of the hollow stranded wire of FIG. FIG. 11 is a graph showing an example of the measurement results obtained by the apparatus of FIG. FIG. 12 is a front view showing the device for evaluating the pushability of the hollow stranded wire of FIG.

A preferred embodiment will be described in detail below, with appropriate reference to the drawings.

[First embodiment]
1-3 show a hollow stranded wire 2. The hollow stranded wire 2 is made of a metal material. A preferred metal is stainless steel. The hollow stranded wire 2 is long. In FIG. 1, arrow A1 indicates the length direction of the hollow stranded wire 2. In FIG. 1, the right side is the front of the hollow stranded wire 2, and the left side is the rear of the hollow stranded wire 2. The hollow stranded wire 2 can be cut to a predetermined length and used as a component of a medical device. Torque applied to one end of the hollow stranded wire 2 is transmitted to the other end.

This hollow stranded wire 2 has a first layer 4 and a second layer 6. The second layer 6 is located outside the first layer 4. The first layer 4 is formed by twisting multiple first wires 10. The second layer 6 is formed by twisting multiple second wires 12.

As shown in Figures 1 and 2, the first wires 10 are twisted clockwise toward the front, and the second wires 12 are twisted counterclockwise toward the front. In other words, the twist direction of the second wires 12 is opposite to the twist direction of the first wires 10. In this specification, the twist direction of the first wires 10 is referred to as the "Z direction," and the twist direction of the second wires 12 is referred to as the "S direction." The first wires 10 may be twisted in the "S direction," and the second wires 12 may be twisted in the "Z direction." The first wires 10 may be twisted in the "S direction," and the second wires 12 may be twisted in the "S direction." The first wires 10 may be twisted in the "Z direction," and the second wires 12 may be twisted in the "Z direction."

Figures 4 and 5 show the first wire 10. As shown in Figure 4, the first wire 10 is long. As shown in Figure 5, the cross section of the first wire 10 is non-circular. The outline of this cross section is smooth. In other words, this outline has no corners. Preferably, this outline does not have any inwardly convex portions. In this embodiment, the cross-sectional shape of the first wire 10 is elliptical. The outline of an ellipse is an outwardly convex curve at every point. The outline may include outwardly convex curves and straight lines. The second wire 12 also has the shape shown in Figures 4 and 5. In other words, Figures 4 and 5 are also a perspective view and a cross-sectional view, respectively, showing the second wire 12. The cross-sectional shape of the second wire 12 may differ from the cross-sectional shape of the first wire 10.

In Fig. 5, symbol Ma represents the major axis of the contour shape. The major axis Ma is the longest straight line that can be drawn within the contour of the cross section. In Fig. 5, symbol Mi represents the minor axis of the contour shape. The minor axis Mi is the longest straight line that satisfies the following (1) and (2).
(1) A straight line that can be drawn within the outline of the cross section.
(2) A straight line perpendicular to the major axis Ma.
5, arrow La represents the length of the major axis Ma, and arrow Li represents the length of the minor axis Mi. The length Li is shorter than the length La. In other words, the cross section of the first wire 10 has directionality.

6, the right side is the front of the hollow stranded wire 2, the left side is the rear of the hollow stranded wire 2, the upper side is the radially outer side of the hollow stranded wire 2, and the lower side is the radially inner side of the hollow stranded wire 2. Figure 6 shows two first strands 10 belonging to the first layer 4. Specifically, the front first strand 10a and the rear first strand 10b are shown. The distance from the axis CL (see Figures 1 and 2) to the first strand 10b is equal to the distance from the axis CL to the first strand 10a. The major axis Ma (see also Figure 5) of each first strand 10 is inclined with respect to the longitudinal direction A1 of the hollow stranded wire 2. The major axis Ma points inward toward the front. Due to this inclination, the front end 14 of the first strand 10b is located forward of the rear end 16 of the first strand 10a. In other words, the first wires 10a and the first wires 10b overlap in the longitudinal direction A1 of the hollow stranded wire 2. In the radial direction of the hollow stranded wire 2, the forward end 14 of the first wire 10b is located more inward than the rearward end 16 of the first wire 10a. The first wire 10b is in contact with the first wire 10a.

In this first layer 4, when the hollow stranded wire 2 is rotated, force is transmitted sufficiently between the first strands 10 and the adjacent first strands 10. This first layer 4 is less likely to produce a rotational time lag. This hollow stranded wire 2 can contribute to the torque transmission of medical devices. As is clear from Figure 2, the overlap of the first strands 10 is achieved throughout the entire length of the hollow stranded wire 2. The first layer 4 may include areas where there is no overlap due to manufacturing errors, etc.

In Figure 6, arrow L1 indicates the overlap distance between the position of the front first wire 10a and the position of the rear first wire 10b in the longitudinal direction of the hollow stranded wire 2. The ratio of this overlap distance L1 to the length La of the major axis Ma of the first wire 10 (see Figure 5) is preferably 1.0% or more and 20% or less. A first layer 4 with this ratio of 1.0% or more can contribute to torque transmission. From this perspective, this ratio is more preferably 2.0% or more, and particularly preferably 2.5% or more. A hollow stranded wire 2 with this ratio of 20% or less has excellent flexibility. From this perspective, this ratio is more preferably 17% or less, and particularly preferably 15% or less.

In Figure 6, arrow α1 represents the angle of the major axis Ma of the first wire 10 relative to the longitudinal direction A1 of the hollow stranded wire 2. The absolute value of angle α1 is preferably 2° or greater and 30° or less. A first layer 4 with an absolute value of 2° or greater can contribute to torque transmission. From this perspective, the absolute value is more preferably 4° or greater, and particularly preferably 5° or greater. A hollow stranded wire 2 with an absolute value of 30° or less has excellent flexibility. From this perspective, the absolute value is more preferably 17° or less, and particularly preferably 15° or less.

Figure 6 also shows two second strands 12 belonging to the second layer 6. Specifically, a front second strand 12a and a rear second strand 12b are shown. The distance from the axis CL (see Figures 1 and 2) to the second strand 12b is equal to the distance from the axis CL to the second strand 12a. The long axis Ma (see also Figure 5) of each second strand 12 is inclined with respect to the longitudinal direction A1 of the hollow stranded wire 2. The long axis Ma points inward toward the front. Due to this inclination, the forward end 18 of the second strand 12b is located forward of the rear end 20 of the second strand 12a. In other words, the positions of the second strands 12a and 12b overlap in the longitudinal direction A1 of the hollow stranded wire 2. In the radial direction of the hollow stranded wire 2, the forward end 18 of the second strand 12b is located more inward than the rear end 20 of the second strand 12a. The second wire 12b is in contact with the second wire 12a.

In this second layer 6, when the hollow stranded wire 2 is rotated, force is transmitted sufficiently between the second wires 12 adjacent to it. This second layer 6 is less likely to produce a rotational time lag. This hollow stranded wire 2 can contribute to the torque transmission of medical devices. As is clear from Figure 2, the second wires 12 overlap throughout the entire length of the hollow stranded wire 2. The second layer 6 may include areas where there is no overlap due to manufacturing errors, etc.

In Figure 6, arrow L2 indicates the overlap distance between the position of the front second wire 12a and the position of the rear second wire 12b in the longitudinal direction of the hollow stranded wire 2. The ratio of this overlap distance L2 to the length La of the major axis Ma of the second wire 12 (see Figure 5) is preferably 1.0% or more and 20% or less. A second layer 6 with this ratio of 1.0% or more can contribute to torque transmission. From this perspective, this ratio is more preferably 2.0% or more, and particularly preferably 2.5% or more. A hollow stranded wire 2 with this ratio of 20% or less has excellent flexibility. From this perspective, this ratio is more preferably 17% or less, and particularly preferably 15% or less.

In Figure 6, arrow α2 represents the angle of the major axis Ma of the second wire 12 relative to the longitudinal direction A1 of the hollow stranded wire 2. The absolute value of angle α2 is preferably 2° or greater and 30° or less. A second layer 6 with an absolute value of 2° or greater can contribute to torque transmission. From this perspective, the absolute value is more preferably 4° or greater, and particularly preferably 5° or greater. A hollow stranded wire 2 with an absolute value of 30° or less has excellent flexibility. From this perspective, the absolute value is more preferably 17° or less, and particularly preferably 15° or less.

In this embodiment, overlapping strands exist in both the first layer 4 and the second layer 6. Overlapping strands may exist only in the first layer 4. Overlapping strands may exist only in the second layer 6.

In Figure 1, arrow β1 represents the twist angle of the first layer 4. The absolute value of twist angle β1 is preferably 85° or less. A first wire 10 with an absolute value of 85° or less can contribute to torque transmission and pushability. From this perspective, the absolute value is more preferably 82° or less, and particularly preferably 80° or less. The absolute value is preferably 50° or more.

As shown in FIG. 1, the first layer 4 is formed by twisting six first wires 10 (101, 102, 103, 104, 105, 106). In other words, the number of strands in the first layer 4 is six. This number is preferably three or more. In a first layer 4 having three or more strands, an angle β1 with a small absolute value can be achieved. From this perspective, the number of strands is more preferably five or more, and particularly preferably six or more. The number of strands is preferably 16 or less.

In Figure 1, arrow β2 indicates the twist angle of the second layer 6. The absolute value of twist angle β2 is preferably 85° or less. Second wires 12 with an absolute value of 85° or less can contribute to torque transmission and pushability. From this perspective, the absolute value is more preferably 82° or less, and particularly preferably 80° or less. The absolute value is preferably 50° or more.

As shown in FIG. 1, the second layer 6 is formed by twisting six second wires 12 (121, 122, 123, 124, 125, 126). In other words, the number of threads in the second layer 6 is six. This number is preferably three or more. In a second layer 6 having three or more threads, an angle β2 with a small absolute value can be achieved. From this perspective, the number of threads is more preferably five or more, and particularly preferably six or more. The number of threads is preferably 16 or less.

As mentioned above, the twist direction of the second wires 12 is opposite to the twist direction of the first wires 10. When this hollow stranded wire 2 is rotated counterclockwise, there is little rotational time lag in the first layer 4. Therefore, this first layer 4 contributes to torque transmissibility. When this hollow stranded wire 2 is rotated clockwise, there is little rotational time lag in the second layer 6. Therefore, this second layer 6 contributes to torque transmissibility. This hollow stranded wire 2 has excellent torque transmissibility regardless of the rotation direction.

The two-dot chain line designated CC in Figure 3 is the circumscribing circle of the hollow stranded wire 2. The circumscribing circle CC is the smallest circle that can contain the entire cross-sectional contour of the hollow stranded wire 2 within its interior. The arrow Dc indicates the diameter of this circumscribing circle CC. In this specification, this diameter Dc is referred to as the "outer diameter of the hollow stranded wire." From the perspective of facilitating insertion of medical devices using this hollow stranded wire 2 into body cavities, the outer diameter Dc is preferably 5.0 mm or less, more preferably 3.0 mm or less, and particularly preferably 2.0 mm or less.

The two-dot chain line designated IC in Figure 3 is the inscribed circle of the hollow stranded wire 2. The inscribed circle IC is the largest circle that can be drawn inside the cross section of the hollow stranded wire 2. The arrow Di indicates the diameter of this inscribed circle IC. In this specification, this diameter Di is referred to as the "inner diameter of the hollow stranded wire." From the perspective of making it easy to pass other components inside, the inner diameter Di is preferably 0.2 mm or more, more preferably 0.5 mm or more, and particularly preferably 1.0 mm or more.

In the present invention, the average diameter D of the hollow stranded wire 2 is calculated by the following formula.
D = (Dc + Di) / 2
In the present invention, the thickness T of the hollow stranded wire 2 is calculated by the following formula.
T = (Dc - Di) / 2

The ratio (D/T) of the average diameter D to the thickness T is preferably 5 or greater and 20 or less. A hollow stranded wire 2 with a ratio (D/T) of 5 or greater can easily have other components passed through it. From this perspective, a ratio (D/T) of 6 or greater is more preferable, and 8 or greater is particularly preferable. A hollow stranded wire 2 with a ratio (D/T) of 20 or less has excellent pushability. From this perspective, a ratio (D/T) of 18 or less is more preferable, and 16 or less is particularly preferable.

The ratio (La/Li) of the length La of the major axis Ma of the first wire 10 or the second wire 12 (see Figure 5) to the length Li of the minor axis Mi is preferably 1.5 or greater and 10 or less. A hollow stranded wire 2 having a ratio (La/Li) of 1.5 or greater has excellent pushability. From this perspective, the ratio (La/Li) is more preferably 1.8 or greater, and particularly preferably 2.0 or greater. A hollow stranded wire 2 having a ratio (La/Li) of 10 or less is flexible. From this perspective, the ratio (La/Li) is more preferably 8 or less, and particularly preferably 7 or less.

To manufacture this hollow stranded wire 2, a base wire is first rolled or drawn using a profile die to obtain first strands 10 and second strands 12. Next, a core wire is prepared. Multiple first strands 10 are twisted around this core wire to form the first layer 4. Multiple second strands 12 are twisted around this first layer 4 to form the second layer 6. The stranded wire consisting of this first layer 4 and second layer 6 is then subjected to a post-heat treatment. This post-heat treatment stabilizes the shapes of the first layer 4 and second layer 6. After this heat treatment, the stranded wire is cut to a predetermined length. The core wire is then pulled out of the first layer 4 to obtain the hollow stranded wire 2.

A typical application for this hollow stranded wire 2 is a guide wire used in catheter examinations. Other applications include the shafts of catheters for thrombus removal, the shafts of catheters for IVUS (intravascular ultrasound), wires for operating devices inside endoscopes, and industrial operating parts.

[Second embodiment]
7 shows a hollow stranded wire 22 according to another embodiment. The hollow stranded wire 22 has a first layer 24 and a second layer 26. The second layer 26 is located outside the first layer 24. The first layer 24 is formed by twisting a plurality of first strands 28. The second layer 26 is formed by twisting a plurality of second strands 30. The configuration of the first layer 24 is the same as that of the first layer 4 shown in FIGS. 1-6.

Figure 7 shows two second strands 30 belonging to the second layer 26. Specifically, the front second strand 30a and the rear second strand 30b are shown. The distance from the axis CL to the second strand 30b is equal to the distance from the axis CL to the second strand 30a. The long axis Ma of each second strand 30 is inclined with respect to the longitudinal direction A1 of the hollow stranded wire 22. The long axis Ma points outward toward the front. Due to this inclination, the forward end 32 of the second strand 30b is located further forward than the rear end 34 of the second strand 30a. In other words, the positions of the second strands 30a and 30b overlap in the longitudinal direction A1 of the hollow stranded wire 22. In the radial direction of the hollow stranded wire 22, the forward end 32 of the second strand 30b is located further outward than the rear end 34 of the second strand 30a. The second wire 30b is in contact with the second wire 30a.

In this second layer 26, when the hollow stranded wire 22 is rotated, force is transmitted sufficiently between the second strands 30 and adjacent second strands 30. This second layer 26 is less likely to produce a rotational time lag. This hollow stranded wire 22 can contribute to the torque transmission of medical devices. It is preferable that the overlap of the second strands 30 is achieved throughout the entire length of the hollow stranded wire 22. The second layer 26 may include areas where there is no overlap due to manufacturing errors, etc.

In Figure 7, arrow L3 indicates the overlap distance between the position of the front second wire 30a and the position of the rear second wire 30b in the longitudinal direction of the hollow stranded wire 22. The ratio of this overlap distance L3 to the length of the major axis Ma of the second wire 30 is preferably 1.0% or more and 20% or less. A second layer 26 with this ratio of 1.0% or more can contribute to torque transmission. From this perspective, this ratio is more preferably 2.0% or more, and particularly preferably 2.5% or more. A hollow stranded wire 22 with this ratio of 20% or less has excellent flexibility. From this perspective, this ratio is more preferably 17% or less, and particularly preferably 15% or less.

In Figure 7, arrow α3 represents the angle of the major axis Ma of the second wire 30 relative to the longitudinal direction A1 of the hollow stranded wire 22. The absolute value of angle α3 is preferably 2° or greater and 30° or less. A second layer 26 with an absolute value of 2° or greater can contribute to torque transmission. From this perspective, the absolute value is more preferably 4° or greater, and particularly preferably 5° or greater. A hollow stranded wire 22 with an absolute value of 30° or less has excellent flexibility. From this perspective, the absolute value is more preferably 17° or less, and particularly preferably 15° or less.

In this hollow stranded wire 22, the longitudinal axis Ma of the first wires 28 faces inward toward the front, and the longitudinal axis Ma of the second wires 30 faces outward toward the front. The inclination direction of the longitudinal axis Ma of the second wires 30 is opposite to the inclination direction of the longitudinal axis Ma of the first wires 28. This hollow stranded wire 22 has excellent torque transmission properties regardless of the rotation direction.

The twist direction of the first wires 28 may be either the "Z direction" or the "S direction." The twist direction of the second wires 30 may be either the "Z direction" or the "S direction." From the perspective of uniform torque transmission, it is preferable that the twist direction of the second wires 30 be opposite to the twist direction of the first wires 28.

[Third embodiment]
8 shows a hollow stranded wire 36 according to yet another embodiment. The hollow stranded wire 36 has a first layer 38, a second layer 40, and a third layer 42. The second layer 40 is located outside the first layer 38. The third layer 42 is located outside the second layer 40. The first layer 38 is formed by twisting a plurality of first strands 44. The second layer 40 is formed by twisting a plurality of second strands 46. The third layer 42 is formed by twisting a plurality of third strands 48.

Figure 9 shows two first wires 44 belonging to the first layer 38, two second wires 46 belonging to the second layer 40, and two third wires 48 belonging to the third layer 42. The configurations of the first layer 38 and the second layer 40 are the same as those of the first layer 4 and the second layer 6 shown in Figure 6, respectively. The cross-sectional shape of each third wire 48 is the same as that of the first wire 44.

Figure 9 shows the front third wire 48a and the rear third wire 48b. The distance from the axis CL (see Figure 8) to the third wire 48b is equal to the distance from the axis CL to the third wire 48a. The major axis Ma of each third wire 48 is inclined with respect to the longitudinal direction A1 of the hollow stranded wire 36. The major axis Ma points inward toward the front. Due to this inclination, the forward end 50 of the third wire 48b is located further forward than the rear end 52 of the third wire 48a. In other words, the positions of the third wires 48a and 48b overlap in the longitudinal direction A1 of the hollow stranded wire 36. In the radial direction of the hollow stranded wire 36, the forward end 50 of the third wire 48b is located further inward than the rear end 52 of the third wire 48a. The third wire 48b is in contact with the third wire 48a.

In this third layer 42, when the hollow stranded wire 36 is rotated, force is transmitted sufficiently between the third wires 48 and adjacent third wires 48. This third layer 42 is less likely to produce a rotational time lag. This hollow stranded wire 36 can contribute to the torque transmission of medical devices. It is preferable that the overlap of the third wires 48 is achieved throughout the entire length of the hollow stranded wire 36. The third layer 42 may also include areas where there is no overlap due to manufacturing errors, etc.

In Figure 9, arrow L4 indicates the overlap distance between the position of the front third wire 48a and the position of the rear third wire 48b in the longitudinal direction of the hollow stranded wire 36. The ratio of this overlap distance L4 to the length of the major axis Ma of the third wire 48 is preferably 1.0% or more and 20% or less. A third layer 42 with this ratio of 1.0% or more can contribute to torque transmission. From this perspective, this ratio is more preferably 2.0% or more, and particularly preferably 2.5% or more. A hollow stranded wire 36 with this ratio of 20% or less has excellent flexibility. From this perspective, this ratio is more preferably 17% or less, and particularly preferably 15% or less.

In Figure 9, arrow α4 represents the angle of the major axis Ma of the third wire 48 relative to the longitudinal direction A1 of the hollow stranded wire 36. The absolute value of angle α4 is preferably 2° or greater and 30° or less. A third layer 42 with an absolute value of 2° or greater can contribute to torque transmission. From this perspective, the absolute value is more preferably 4° or greater, and particularly preferably 5° or greater. A hollow stranded wire 36 with an absolute value of 30° or less has excellent flexibility. From this perspective, the absolute value is more preferably 17° or less, and particularly preferably 15° or less.

In this embodiment, the inclination direction of the long axis Ma of the second wires 46 is the same as the inclination direction of the long axis Ma of the first wires 44, and the inclination direction of the long axis Ma of the third wires 48 is the same as the inclination direction of the long axis Ma of the first wires 44. The hollow stranded wire 36 may have a layered structure in which the inclination direction of the long axis Ma of the second wires 46 is the same as the inclination direction of the long axis Ma of the first wires 44, and the inclination direction of the long axis Ma of the third wires 48 is opposite to the inclination direction of the long axis Ma of the first wires 44. The hollow stranded wire 36 may have a layered structure in which the inclination direction of the long axis Ma of the second wires 46 is opposite to the inclination direction of the long axis Ma of the first wires 44, and the inclination direction of the long axis Ma of the third wires 48 is the same as the inclination direction of the long axis Ma of the first wires 44. The hollow stranded wire 36 may have a layered structure in which the inclination direction of the long axis Ma of the second wires 46 is opposite to the inclination direction of the long axis Ma of the first wires 44, and the inclination direction of the long axis Ma of the third wires 48 is opposite to the inclination direction of the long axis Ma of the first wires 44.

As shown in FIG. 8, the twist direction of the first wires 44 is the "Z direction," the twist direction of the second wires 46 is the "S direction," and the twist direction of the third wires 48 is the "Z direction." The twist direction of the second wires 46 is opposite to the twist direction of the first wires 44, and the twist direction of the third wires 48 is the same as the twist direction of the first wires 44. This hollow stranded wire 36 has excellent torque transmission properties regardless of the rotation direction. The twist direction of the second wires 46 may be the same as the twist direction of the first wires 44. The twist direction of the third wires 48 may be opposite to the twist direction of the second wires 46.

The effects of the hollow stranded wire according to the examples are explained below, but the scope of the disclosure in this specification should not be interpreted as being limited based on the description of these examples.

[Experiment 1]
[Example 1]
A wire was obtained by drawing and rolling SUS304 steel using a special die. The cross-sectional shape of this wire was elliptical. The short axis length Li of this wire was 0.075 mm, and the long axis length La of this wire was 0.170 mm. Six wires were twisted on top of a core wire to form a first layer. The twist direction of this first layer was the Z-direction. The absolute value of the twist angle of this first layer was 74°. Six wires were twisted on top of this first layer to form a second layer. The twist direction of this second layer was the S-direction. The absolute value of the twist angle of this second layer was 74°. A stranded wire made of these wires was subjected to post-heat treatment. This stranded wire was cut to a predetermined length. The core wire was removed from this stranded wire to obtain a hollow stranded wire of Example 1. The hollow stranded wire had an outer diameter Dc of 1.30 mm and an inner diameter Di of 1.00 mm. This hollow strand had a cross-sectional shape shown in FIG.

[Example 2]
A hollow stranded wire of Example 2 was obtained in the same manner as in Example 1, except that a strand having a major axis length La of 0.180 mm was used.

[Comparative Example 1]
A hollow stranded wire of Comparative Example 1 was obtained in the same manner as in Example 1, except that a wire having a rectangular cross section (i.e., a flat wire) was used.

[Torque transmission]
Torque transmissibility is evaluated by the difference between the rotation angle at the proximal end and the rotation angle at the distal end when the proximal end of the hollow stranded wire is rotated. As shown in FIG. 10 , a rigid pipe 60 having a double spiral portion 54, a first straight portion 56, and a second straight portion 58 is prepared. The diameter of the double spiral portion 54 is 200 mm. A hollow stranded wire 62 is passed through this rigid pipe 60. A rotational force is applied to the proximal end 64 of the hollow stranded wire 62 in the direction indicated by arrow A2 in FIG. 10 . This causes the distal end 66 of the hollow stranded wire 62 to rotate as indicated by arrow A3. The rotation angles at the proximal end 64 and the distal end 66 are measured simultaneously.

Figure 11 is a graph showing the results of rotational tracking measured using the method shown in Figure 10. The two-dot chain line in the graph is a straight line indicating that the difference between the rotation angle of the base end 64 and the rotation angle of the tip end 66 is zero over the entire measurement angle range (input rotation angle range from 0° to approximately 720°). The difference between the rotation angle of the base end 64 and the rotation angle of the tip end 66 of the hollow stranded wire 62 being measured is represented by the difference in the vertical axis between the two-dot chain line and the measurement curve in the graph. The maximum value of the rotational angle difference measured over the input rotation angle range from 0° to 720° is a value that correlates with torque transmissibility. The maximum angle difference of the hollow stranded wire 62 is shown as an index in Table 1 below. A hollow stranded wire with a smaller index has better torque transmissibility.

[Pushability]
As shown in Figure 12, a chuck 72 was used to fix the vicinity of a first end 70 of a hollow stranded wire 68. The distance from this chuck 72 to a second end 74 of the hollow stranded wire 68 was 100 mm. The hollow stranded wire 68 bent under its own weight, and the second end 74 moved downward. This movement distance L was measured. This movement distance L is shown as an index in Table 1 below. A hollow stranded wire 68 with a smaller index has greater rigidity. A hollow stranded wire 68 with a smaller index has excellent pushability.

As shown in Table 1, the hollow stranded wires of each example have excellent rotational followability and pushability. These evaluation results clearly demonstrate the superiority of the present invention.

[Experiment 2]
[Example 3]
A wire was obtained by drawing and rolling SUS304 steel using a special die. The cross-sectional shape of the wire was elliptical. The wire had a minor axis length Li of 0.045 mm and a major axis length La of 0.270 mm. Eight wires were twisted on a core wire to form a first layer. The twist direction of the first layer was the Z-direction. The absolute value of the twist angle of the first layer was 67°. Eight wires were twisted on the first layer to form a second layer. The twist direction of the second layer was the S-direction. The absolute value of the twist angle of the second layer was 67°. Eight wires were twisted on the second layer to form a third layer. The twist direction of the third layer was the Z-direction. The absolute value of the twist angle of the third layer was 67°. A stranded wire made of these wires was subjected to post-heat treatment. The stranded wire was cut to a predetermined length. The core wire was removed from this stranded wire to obtain a hollow stranded wire of Example 3. The hollow stranded wire had an outer diameter Dc of 1.77 mm and an inner diameter Di of 1.50 mm. The hollow stranded wire had a cross-sectional shape shown in Figure 9.

[Comparative Example 2]
A hollow stranded wire of Comparative Example 2 was obtained in the same manner as in Example 3, except that a wire having a rectangular cross section (i.e., a flat wire) was used.

[Torque transmission]
The torque transmission properties of the hollow stranded wire were evaluated in the same manner as in Experiment 1. The results are shown in Table 2 below.

[Pushability]
The pushability of the hollow stranded wire was evaluated in the same manner as in Experiment 1. The results are shown in Table 2 below.

As shown in Table 2, the hollow stranded wire of Example 3 has excellent rotational followability and pushability. These evaluation results clearly demonstrate the superiority of the present invention.

[Disclosure items]
Each of the following sections discloses a preferred embodiment.

[Item 1]
a first layer formed by twisting three or more first wires;
a second layer formed by twisting three or more second wires and positioned on the outside or inside of the first layer,
Each of the first wires has a non-circular cross-sectional shape including a major axis and a minor axis,
the long axis is inclined with respect to the longitudinal direction of the hollow stranded wire,
In the longitudinal direction of the hollow stranded wire, the position of a front first wire overlaps the position of a rear first wire adjacent to the front first wire.

[Item 2]
2. The hollow stranded wire according to item 1, wherein an overlap distance between the position of the front first wire and the position of the rear first wire is 1.0% or more and 20% or less of the length of the major axis.

[Item 3]
Each second wire has a non-circular cross-sectional shape including a major axis and a minor axis,
the long axis is inclined with respect to the longitudinal direction of the hollow stranded wire,
3. The hollow stranded wire according to item 1 or 2, wherein a front second wire and a rear second wire adjacent to the front second wire overlap in the length direction of the hollow stranded wire.

[Item 4]
4. The hollow stranded wire according to item 3, wherein an overlap distance between the position of the front second wire and the position of the rear second wire is 1.0% or more and 20% or less of the length of the major axis.

[Item 5]
5. The hollow stranded wire according to item 3 or 4, wherein the inclination direction of the major axes of the second wires is opposite to the inclination direction of the major axes of the first wires.

[Item 6]
6. The hollow stranded wire according to any one of items 1 to 5, wherein the second wires are twisted in a direction opposite to the direction in which the first wires are twisted.

[Item 7]
7. The hollow stranded wire according to any one of items 1 to 6, wherein the first wires have a twist angle of 85° or less, and the second wires have a twist angle of 85° or less.

[Item 8]
8. The hollow stranded wire according to any one of items 1 to 7, further comprising a third layer formed by twisting three or more third wires and positioned outside or inside the first layer and the second layer.

[Item 9]
Each third wire has a non-circular cross-sectional shape including a major axis and a minor axis,
the long axis is inclined with respect to the longitudinal direction of the hollow stranded wire,
Item 9. The hollow strand according to item 8, wherein a front third wire and a rear third wire adjacent to the front third wire overlap in the length direction of the hollow strand.

[Item 10]
the second layer is positioned outside the first layer,
the third layer is located outside the second layer,
The twisting direction of the second wires is opposite to the twisting direction of the first wires,
Item 10. The hollow stranded wire according to item 8 or 9, wherein the third wires are twisted in the same direction as the first wires.

The hollow stranded wire described above is suitable for a variety of medical devices. This hollow stranded wire is also suitable for applications other than medical devices.

2: Hollow stranded wire 4: First layer 6: Second layer 10: First wire 10a: Front first wire 10b: Rear first wire 12: Second wire 12a: Front second wire 12b: Rear second wire 22: Hollow stranded wire 24: First layer 26: Second layer 28: First wire 30: Second wire 30a: Front second wire 30b: Rear second wire 36: Hollow stranded wire 38: First layer 40: Second layer 42: Third layer 44: First wire 46: Second wire 48: Third wire 48a: Front third wire 48b: Rear third wire

Claims (10)

a first layer formed by twisting three or more first wires;
a second layer formed by twisting three or more second wires and positioned on the outside or inside of the first layer,
a cross-sectional shape of each first wire is non-circular including a major axis and a minor axis, and the outline of this cross-sectional shape is an outwardly convex curve at every point ;
the long axis is inclined with respect to the longitudinal direction of the hollow stranded wire,
In the longitudinal direction of the hollow stranded wire, the position of a front first wire overlaps the position of a rear first wire adjacent to the front first wire. The hollow stranded wire according to claim 1, wherein the overlap distance between the position of the front first wire and the position of the rear first wire is 1.0% or more and 20% or less of the length of the major axis. the cross-sectional shape of each second wire is non-circular including a major axis and a minor axis, and the outline of this cross-sectional shape is an outwardly convex curve at every point ;
the long axis is inclined with respect to the longitudinal direction of the hollow stranded wire,
3. The hollow stranded wire according to claim 1, wherein a front second wire and a rear second wire adjacent to the front second wire overlap in the longitudinal direction of the hollow stranded wire. The hollow stranded wire according to claim 3, wherein the overlap distance between the position of the front second wire and the position of the rear second wire is 1.0% or more and 20% or less of the length of the major axis. The hollow stranded wire according to claim 3, wherein the inclination direction of the long axis of the second strand is opposite to the inclination direction of the long axis of the first strand. The hollow stranded wire according to claim 1 or 2, wherein the second strands are twisted in the opposite direction to the first strands. The hollow stranded wire according to claim 1 or 2, wherein the twist angle of the first strand is 85° or less, and the twist angle of the second strand is 85° or less. The hollow stranded wire according to claim 1 or 2, further comprising a third layer formed by twisting three or more third wires and positioned outside or inside the first layer and the second layer. the cross-sectional shape of each third wire is non-circular including a major axis and a minor axis, and the outline of this cross-sectional shape is an outwardly convex curve at every point ;
the long axis is inclined with respect to the longitudinal direction of the hollow stranded wire,
9. The hollow stranded wire according to claim 8, wherein a front third wire and a rear third wire adjacent to the front third wire overlap in the longitudinal direction of the hollow stranded wire. the second layer is positioned outside the first layer,
the third layer is located outside the second layer,
The twisting direction of the second wires is opposite to the twisting direction of the first wires,
9. The hollow stranded wire according to claim 8, wherein the third wires are twisted in the same direction as the first wires.