A microcatheter

Abstract

The application relates to a micro catheter belonging to the technical field of medical instruments. The micro catheter comprises a main body part arranged at a proximal end and a tip part arranged at a distal end; the outer diameter of the tip part is smaller than that of the main body part; the micro catheter further comprises an inner layer, a reinforcing layer and an outer layer which are sequentially sleeved from inside to outside; the inner layer extends from the main body part to the distal end of the tip part, and the inner layer has a first transition section with a gradually reduced inner diameter from the proximal end to the distal end direction; the reinforcing layer is wound on the outer wall of the inner layer, and the reinforcing layer comprises a braided layer and a spring layer arranged in the radial direction of the inner layer; and the outer layer is wrapped on the outer sides of the reinforcing layer and the inner layer. The micro catheter has good pushability and bending resistance.

Description

Technical Field

[0001] This application relates to the field of medical device technology, and more specifically, to a microcatheter. Background Technology

[0002] Chronic total occlusion (CTO) of the coronary arteries is a major challenge in current coronary interventional treatment. Typically, during CTO intervention, a microcatheter and guidewire are used alternately to support the guidewire in reaching the CTO lesion. Therefore, the microcatheter needs to have a certain degree of maneuverability and bend resistance. Summary of the Invention

[0003] This application provides a microcatheter with good pushability and bending resistance.

[0004] This application is implemented as follows: An example of this application provides a microcatheter including a body portion disposed proximally and a tip portion disposed distally. The outer diameter of the tip portion is smaller than the outer diameter of the body portion. The microcatheter also includes an inner layer, a reinforcing layer, and an outer layer sequentially disposed from the inside out. The inner layer extends from the body portion to the distal end of the tip portion, and has a first transition section in which the inner diameter gradually decreases from the proximal end toward the distal end. The reinforcing layer is wound around the outer wall of the inner layer, and the reinforcing layer includes a braided layer and a spring layer arranged radially along the inner layer; the outer layer covers the outside of the reinforcing layer and the inner layer.

[0005] In the above implementation process, the inner layer has a first transition section with a gradually decreasing inner diameter from the proximal end to the distal end, which helps to reduce the size of the tip and improve the delivery capability of the microcatheter. Typically, during the delivery of a microcatheter, due to the size and flexibility differences between the main body and the tip, stress concentration easily occurs at the junction of the main body and the tip, resulting in weak bending resistance of the microcatheter. Therefore, in the microcatheter provided in this application, the inner layer extends from the main body to the distal end of the tip, and the inner layers of the main body and the tip are an integral structure, which can reduce the stress at the junction of the main body and the tip. Simultaneously, a reinforcing layer is wound around the outer wall of the inner layer. The braided layer and spring layer in the reinforcing layer enable the microcatheter to have good rigidity and flexibility, and the outer layer wraps around the outside of the reinforcing layer and the inner layer, thereby improving the delivery capability and bending resistance of the microcatheter. Attached Figure Description

[0006] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0007] Figure 1 This is a planar schematic diagram of the microcatheter provided in the embodiments of this application; Figure 2for Figure 1 A partial perspective view; Figure 3 A partial cross-sectional view of the body and tip of a microcatheter provided in an embodiment of this application; Figure 4 This is a schematic diagram of the cutoff grid. Figure 5A This is a planar schematic diagram of the first type of braided layer provided in the embodiments of this application; Figure 5B for Figure 5A A schematic diagram of the formation of solder joints; Figure 6A This is a planar schematic diagram of the second type of braided layer provided in the embodiments of this application; Figure 6B for Figure 6A A schematic diagram of the formation of solder joints; Figure 7A This is a planar schematic diagram of the third type of braided layer provided in the embodiments of this application; Figure 7B for Figure 7A A schematic diagram of the formation of solder joints; Figure 8A This is a planar schematic diagram of the fourth type of braided layer provided in the embodiments of this application; Figure 8B for Figure 8A A schematic diagram of the formation of solder joints; Figure 9A This is a planar schematic diagram of the fifth type of braided layer provided in the embodiments of this application; Figure 9B for Figure 9A A schematic diagram of the formation of solder joints; Figure 10A This is a planar schematic diagram of the sixth type of braided layer provided in the embodiments of this application; Figure 10B for Figure 10A A schematic diagram of the formation of solder joints; Figure 11A This is a planar schematic diagram of the seventh type of braided layer provided in the embodiments of this application; Figure 11B for Figure 11A A schematic diagram of the formation of solder joints; Figure 12A A planar schematic diagram of the eighth type of braided layer provided in the embodiments of this application; Figure 12B for Figure 12A A schematic diagram of the formation of solder joints; Figure 13A This is a planar schematic diagram of the first type of spring layer provided in the embodiments of this application; Figure 13BThis is a planar schematic diagram of a second type of spring layer provided in an embodiment of this application.

[0008] Reference numerals: 100-Microcatheter; 1-Main body; 2-Tip; 3-Inner layer; 31-First transition section; 4-Reinforcing layer; 41-Spring layer; 411-Hollowed structure; 42-Braided layer; 421-First filament bundle; 422-Second filament bundle; 423-First intersection point; 424-Second intersection point; 425-Third intersection point; 426-Fourth intersection point; 5-Outer layer; 51-Second transition section; 52-Third transition section; 53-First tube segment; 54-Second tube segment; 55-Third tube segment; 56-Fourth tube segment; 57-Fifth tube segment; 58-Equal outer diameter section; 6-Grid; 60-Stop grid; 61-First grid group; 62-Second grid group; 63-Third grid group; 64-Fourth grid group; 7-Weld point; L1-First spacing; L2-Second spacing. Detailed Implementation

[0009] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0010] Please combine Figure 1 , Figure 2 and Figure 3 This application provides a microcatheter 100, including a main body 1 disposed at a proximal end and a tip 2 disposed at a distal end. The outer diameter of the tip 2 is smaller than the outer diameter of the main body 1. The microcatheter 100 also includes an inner layer 3, a reinforcing layer 4, and an outer layer 5 sequentially disposed from the inside to the outside. The inner layer 3 extends from the main body 1 to the distal end of the tip 2, and has a first transition section 31 in which the inner diameter gradually decreases from the proximal end to the distal end. The reinforcing layer 4 is wound around the outer wall of the inner layer 3, and the reinforcing layer 4 includes a braided layer 42 and a spring layer 41 arranged in the radial direction of the inner layer 3; the outer layer 5 covers the outer side of the reinforcing layer 4 and the inner layer 3.

[0011] In this embodiment of the microcatheter 100, a first transition section 31 is provided in the inner layer 3, with the inner diameter gradually decreasing from the proximal end to the distal end. This helps to reduce the size of the tip 2 and improve the pushability of the microcatheter 100. In this embodiment of the application, the inner layer 3 extends from the main body 1 to the distal end of the tip 2, making the inner layer 3 of the main body 1 and the tip 2 an integral structure, thereby improving the stress concentration problem at the junction of the main body 1 and the tip 2. At the same time, a reinforcing layer 4 is wound around the outer wall of the inner layer 3. The braided layer 42 and the spring layer 41 in the reinforcing layer 4 enable the microcatheter 100 to have good rigidity and flexibility, and the outer layer 5 is wrapped around the outside of the reinforcing layer 4 and the inner layer 3, thereby improving the pushability and bending resistance of the microcatheter 100.

[0012] In this application, "proximal" refers to the end closest to the operator. The "proximal" end is usually outside the body and is the end that the doctor holds and manipulates. "Distal" refers to the end furthest from the operator. The "distal" end is usually deep inside the patient's body and is the end that ultimately reaches the site of the lesion (such as a coronary artery blockage).

[0013] It is understandable that, such as Figure 3 As shown, the inner layer 3 has a guidewire lumen formed inside for the guidewire to pass through. The specific material of the inner layer 3 in this application can be selected according to conventional materials in the field of microcatheter 100. As an example, the inner layer 3 can be made of at least one of polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxyalkylene (PFA), polyethylene terephthalate (PET), or polyether ether ketone (PEEK).

[0014] Typically, the inner layer 3 has a relatively uniform wall thickness. In other embodiments, the thickness of the inner layer 3 may vary at different locations along its axial direction. The inner layer 3 has a first transition section 31 whose inner diameter gradually decreases from the proximal end to the distal end, resulting in a relatively small outer diameter at the first transition section 31. This helps to reduce the outer diameter of the tip 2 and improve the pushability of the microcatheter 100.

[0015] This application does not limit the specific location of the first transition section 31, and the first transition section 31 may be located in at least one of the main body 1 and the tip 2.

[0016] In one optional embodiment, the first transition section 31 is located at the tip 2; in another optional embodiment, the first transition section 31 is located in both the body 1 and the tip 2, i.e., the first transition section 31 extends from the body 1 to the tip 2; the location of the first transition section 31 at the tip 2 helps to reduce the size of the tip 2 and improve the pushability of the microcatheter 100. In yet another optional embodiment, such as Figure 3 As shown, the first transition section 31 is located in the main body 1. Before the inner layer 3 extends from the main body 1 to the tip 2, the first transition section 31 with a gradually decreasing inner diameter is formed in advance. This can reduce the outer diameter of the inner layer 3 at the tip 2, while also making the inner layer 3 at the tip 2 relatively flat. This reduces the probability of bending at the tip 2 due to stress concentration caused by the shrinkage of the inner layer 3, thereby improving the pushability of the microcatheter 100 while ensuring its bending resistance.

[0017] Furthermore, in some embodiments, the first transition segment 31 is located in the main body 1, and the first transition segment 31 is spaced apart from the junction of the main body 1 and the tip 2 by a first distance. In this embodiment, the first transition segment 31 extends from the maximum inner diameter of the inner layer 3 to the minimum inner diameter of the inner layer 3. The first transition segment 31 is spaced apart from the junction of the main body 1 and the tip 2 by a first distance at the minimum inner diameter, which avoids the formation of a diameter-reducing structure at the junction of the main body 1 and the tip 2. This can further reduce and improve the stress concentration caused by the junction, reduce the probability of the microcatheter 100 bending, and further improve the bending resistance of the microcatheter 100.

[0018] For example, the first distance is 0.5 to 1.5 times the projected length of the first transition segment 31 along the axial direction. This application does not limit the taper of the first transition segment 31, and it can be adjusted accordingly as needed. As an example, the taper of the first transition segment 31 is 1° to 10°. Furthermore, this application does not limit the inner layer 3 to only having one first transition segment 31, and multiple first transition segments 31 can be provided as needed. The length, taper, and distribution position of the multiple first transition segments 31 can be adjusted accordingly as needed.

[0019] In some embodiments, please continue reading Figure 3 The spring layer 41 is located within the main body 1, and the distal end of the spring layer 41 does not extend beyond the junction of the main body 1 and the tip 2. In an optional embodiment, such as... Figure 3 As shown, the distal end of the spring layer 41 is located at the junction of the main body 1 and the tip 2. That is, the distal end of the spring layer 41 is taken as the junction of the main body 1 and the tip 2. In other embodiments, there is a gap between the distal end of the spring layer 41 and the junction of the main body 1 and the tip 2. This application does not make specific limitations.

[0020] In some embodiments, please continue reading Figure 2 and Figure 3 The braided layer 42 extends from the main body 1 into the tip 2, with the proximal end of the braided layer 42 located in the main body 1 and the distal end of the braided layer 42 located in the tip 2. In an optional embodiment, the length of the braided layer 42 extending beyond the junction of the main body 1 and the tip 2 is a second distance, which accounts for 20% to 80% of the axial length of the tip 2.

[0021] This application reduces stress at the junction of the main body 1 and the tip 2 by differentially distributing the spring layer 41 and the braided layer 42 on the main body 1 and the tip 2, thereby improving the bending resistance of the microcatheter 100. Furthermore, in one optional embodiment, the braided layer 42 is located outside the spring layer 41; in another optional embodiment, the braided layer 42 is located inside the spring layer 41.

[0022] In some embodiments, please continue reading Figure 3 The outer layer 5 has a second transition section 51 and a third transition section 52 whose outer diameter gradually decreases from the proximal end to the distal end. The second transition section 51 is located in the main body 1 and the third transition section 52 is located in the tip 2.

[0023] In the above technical solution, a second transition section 51 with an outer diameter that gradually decreases toward the distal end is formed at a position of the outer layer 5 corresponding to the main body 1, and a third transition section 52 with an outer diameter that gradually decreases toward the distal end is formed at a position of the outer layer 5 corresponding to the tip 2. This helps to gradually reduce the outer diameter of the microcatheter 100 and improve the stress concentration problem caused by the sudden change in outer diameter.

[0024] Furthermore, in some embodiments, the taper of the second transition segment 51 is greater than the taper of the third transition segment 52.

[0025] In the above technical solution, the outer layer 5 has a relatively large taper corresponding to the second transition section 51 of the main body 1. Before the outer layer 5 extends to the tip 2, the outer diameter of the microcatheter 100 is reduced in advance, so that the taper of the outer layer 5 at the third transition section 52 of the tip 2 is relatively slowed down, which can meet the outer diameter requirements of the tip 2. The large taper of the main body 1 completes most of the radial dimension transition of the catheter, which creates a basis for the tip 2 to slowly thin its outer diameter with a constant inner diameter and a smaller taper. This not only ensures that the tip 2 has a wider and constant effective inner cavity, but also makes the tip thin-wall forming process smoother and more controllable, improving the tip size accuracy and manufacturing yield.

[0026] Furthermore, in some embodiments, please continue to refer to Figure 3 The outer layer 5 also has an equal outer diameter section 58 located between the second transition section 51 and the third transition section 52, which extends from the main body 1 to the tip 2.

[0027] In the above technical solution, an equal outer diameter section 58 is provided between the two transition sections of the outer layer 5, and the equal outer diameter section extends from the main body 1 to the tip 2, so that the outer diameter near the junction of the main body 1 and the tip 2 is equal. Combined with the first transition section 31 of the inner layer 3 being spaced a first distance from the junction of the main body 1 and the tip 2, the inner diameter near the junction of the main body 1 and the tip 2 is equal. The inner and outer diameters near the junction of the main body 1 and the tip 2 are both equal, which can further improve the stress concentration problem caused by the size change at the junction, and thus further improve the bending resistance of the microcatheter 100 while ensuring the pushability of the microcatheter 100.

[0028] Furthermore, the length of the equal outer diameter segment 58 is not fixed in this application. In some embodiments, the length of the equal outer diameter segment is 0.5 to 2 times the length of the tip 2.

[0029] Furthermore, the taper of the second transition segment 51 is the same as that of the first transition segment 31, and the start and end positions of the second transition segment 51 are the same as those of the first transition segment 31, so that the inner and outer diameters of the main body 1 of the microcatheter 100 change simultaneously, thereby improving the stress concentration problem caused by the inconsistent change in the inner and outer diameters of the main body 1. In some embodiments, the distal end of the third transition segment 52 extends to the distal end of the tip 2.

[0030] In this embodiment, the first transition section 31 of the inner layer 3 is disposed in the main body 1. The reduction in the inner diameter of the catheter is limited to the main body 1, while the inner diameter of the tip 2 does not participate in further reduction. Under the premise of ensuring flexibility, the inner lumen of the tip 2 maintains a stable and relatively large diameter, which is conducive to the passage of the microcatheter. At the same time, the outer layer 5 includes a second transition section 51 disposed in the main body 1 and a third transition section 52 disposed in the tip 2. This application disperses the two outer diameter transition intervals in the main body 1 and the tip 2, which has stronger resistance to bending and lumen collapse compared to continuous shrinkage. In addition, this embodiment provides a constant outer diameter section 58 between the second transition section 51 and the third transition section 52. A buffer zone with stable stiffness is provided in the two transition sections with tapered changes. This constant outer diameter section provides uniform bending stiffness, so that when the microcatheter 100 passes through tortuous blood vessels, the transition area does not experience excessive local bending, avoiding stress concentration points formed by continuous shrinkage of the outer diameter, and greatly reducing the risk of lumen collapse or kinking.

[0031] The structural design of the braided layer in this application is described below with reference to the accompanying drawings: like Figure 4 As shown, the braided layer 42 includes a closed, polygonal mesh 6 formed by interlacing multiple strands of yarn. The shape of this polygonal mesh 6 includes one of triangles, quadrilaterals, pentagons, or hexagons. As shown in the embodiment of this application, the polygonal mesh is quadrilateral, specifically a rhombus. Specifically, the braided layer 42 includes first yarns 421 with a first tilt angle and second yarns 422 with a second tilt angle. Multiple first yarns 421 and multiple second yarns 422 intersect to form a rhombus mesh. Each rhombus mesh includes four intersection points: a first intersection point 423 near the proximal end, a second intersection point 424 near the distal end, and a third intersection point 425 and a fourth intersection point 426 located in the same circumferential direction.

[0032] The material of the filaments in the braided layer 42 in this application includes metals, such as stainless steel or nickel-titanium alloy; the filaments can be flat, cylindrical or other shapes, and this application does not limit them.

[0033] See you again Figure 4Mesh 6 includes a cutoff mesh 60 located near the far end of the braided layer 42, exposing at least one side. The far end of the braided layer 42 terminates at the location of the cutoff mesh. In this application, the cutoff mesh 60 is located at the end position near the farthest end of the braided layer 42. In this embodiment, the cutoff mesh 60 is rhomboid with four sides. The cutoff mesh 60 exposes at least one of the four sides, meaning that the cutoff mesh 60 has at least one side that is not shared with other meshes, and that side is exposed. For example, please refer to... Figure 4 Mesh 6 includes a cutoff mesh 60 (the two cutoff meshes in the figure are labeled 60-1 and 60-1 respectively) with two exposed edges near the far end (for ease of display, the exposed edges of the cutoff mesh are thickened in the figure). These two edges are not shared with other meshes. Mesh 6 (labeled 6-1) has four edges shared with other meshes, so it is not a cutoff mesh.

[0034] In this embodiment of the application, the plurality of grids 6 include a plurality of cut-off grids 60 located at the end of the braided layer 42, and the plurality of cut-off grids are located at at least one circumferential position axially upward of the microcatheter 100.

[0035] In one alternative embodiment, such as Figure 5A As shown, the braided layer 42 includes multiple meshes 6, each mesh 6 including multiple stop meshes 60 located at its end (the edges of the stop meshes 60 are thickened in the figure for clarity). All stop meshes 60 are located at the same axial position along the microcatheter 100. In this embodiment, the fact that multiple stop meshes 60 are located at the same circumferential position along the microcatheter 100 indicates that the multiple stop meshes 60 are at the same axial position along the microcatheter 100 and are distributed circumferentially along the microcatheter 100 at this same axial position. That is, the multiple stop meshes 60 are at the same axial position along the microcatheter 100, but their circumferential positions are different.

[0036] In another optional embodiment, the plurality of stop grids 60 are located at at least two different circumferential positions along the axial direction of the microcatheter 100. Optionally, a portion of the stop grids 60 are located at a first axial position of the microcatheter 100, and this portion of the stop grids 60 is distributed circumferentially along the microcatheter 100 at the first axial position; another portion of the stop grids 60 are located at a second axial position of the microcatheter 100, and this portion of the stop grids 60 is distributed circumferentially along the microcatheter 100 at the second axial position. It is understood that at a certain axial position, there may be one stop grid 60, or at least two stop grids 60 distributed circumferentially.

[0037] like Figure 6AAs shown, a first grid group 61 near the far end and a second grid group 62 near the near end are provided at at least two different circumferential positions. The first grid group 61 and the second grid group 62 each include a plurality of grids 6 distributed circumferentially. At least a portion of the grids 6 included in the first grid group 61 and the second grid group 62 are cutoff grids 60. The grid density in the second grid group 62 is greater than the grid density in the first grid group 61. Figure 6A The diagram shows that the grids in the first grid group 61 and the second grid group 62 are both cutoff grids 60. Each cutoff grid 60 in the first grid group 61 exposes two edges, while each cutoff grid 60 in the second grid group 62 exposes one edge. For ease of illustration, the following... Figures 6A to 11A The grid edges of the first grid group 61 are thickened with solid lines, and the grid edges of the second grid group 62 are thickened with dashed lines.

[0038] In the above technical solution, this application disperses the cutoff grid 60 at different circumferential positions in the axial direction, and limits the grid density in the second grid group 62 near the proximal end to be greater than the grid density in the first grid group 61 near the distal end. Since the higher the grid density in the grid group, the stronger the stiffness, the stiffness of the braided layer 42 can be gradually changed towards the distal end. Compared with the braided layer 42 being flush-cut at the same circumferential position, which easily leads to uneven axial mechanical properties of the microcatheter 100 and problems such as abrupt diameter change, sudden increase in local stiffness, and stress concentration at the end, the embodiment of this application does not change the inclination angle of the braided filaments. Under the condition that the grid size is completely consistent, by making the ends of the braided filaments have an uneven cutoff state in the axial direction, a gradual transition of density with a denser proximal end and a sparser distal end is formed, thereby eliminating the abrupt stress change at the tip of the microcatheter 100, and making the microcatheter 100 maintain more uniform flexibility, torque transmission, and bending resistance.

[0039] like Figure 6A As shown, because the mesh size is uniform in this embodiment, the number of meshes in the second mesh group 62 is greater than the number of meshes in the first mesh group 61. This results in a higher mesh density in the second mesh group 62 near the end than in the first mesh group 61 near the far end. By controlling the number of meshes in the mesh group containing the cutoff mesh 60, this embodiment can achieve a gradual change in stiffness at the far end of the braided layer 42, thus improving the problem of sudden stress change at the tip 2.

[0040] It should be noted that the number of grids in the first grid group 61 and the second grid group 62 in this application can be achieved by controlling the cutting of the corresponding filament bundles. Specifically, after the multiple filament bundles in the braided layer 42 are cross-woven on the outer wall of the inner layer 3, the braided layer is shaped by an annealing process. Since the inner layer 3 has a reduced diameter structure at the tip 2 and the thickness of the inner layer 3 remains approximately uniform, the outer diameter of the inner layer 3 also has a reduced diameter structure. At this time, the braided layer 42 is wrapped around the outer wall of the inner layer 3 with a reduced diameter and annealed to shape it, so that the braided layer 42 can be stably fixed on the outer wall of the inner layer 3. Finally, the filament bundles are cut by laser to form the structure shown in the embodiment of this application.

[0041] The first grid group 61 and the second grid group 62 in the embodiments of this application are described in detail below with multiple implementations.

[0042] like Figures 6A-11A As shown, the first grid group 61 includes multiple spaced first grid cells, each first grid cell comprising N1 adjacent grids; the spacing between two adjacent first grid cells is a first spacing L1, which is M1 times the length of the grid along the circumferential direction of the microcatheter 100, where N1 and M1 are both non-zero natural numbers. Specifically, N1 is at least one of 1, 2, 3, 4, or 5; and M1 is at least one of 1, 2, or 3.

[0043] The second grid group 62 includes multiple second grid cells, each comprising N2 adjacent grid cells. The spacing between two adjacent second grid cells is a second spacing L2, which is M2 times the length of the grid along the circumferential direction of the microcatheter 100. N2 is a positive integer, and M2 is an integer greater than or equal to 0. Specifically, N2 is at least one of 1, 2, 3, or 4; and M2 is at least one of 0, 1, or 2.

[0044] In one alternative embodiment, such as Figure 6A As shown, the first grid group 61 includes multiple spaced first grid cells (such as k11, k12, k13), each first grid cell including one grid, where N1 is 1. A rhombus-shaped grid is spaced between two adjacent first grid cells, therefore the first spacing L1 is equal to the length of the rhombus-shaped grid along the circumferential direction of the microcatheter 100, where M1 is 1.

[0045] Continue reading Figure 6A In the second grid group 62, the grids (such as k21 and k22) are not interrupted by laser to form intervals. The second grid cell can be defined to include N2 adjacent grids. At this time, N2 can take the value of positive integers such as 1, 2, and 3. At the same time, since there is no laser interruption, the interval between two adjacent second grid cells is zero. At this time, M2 takes the value of 0.

[0046] In another alternative embodiment, such as Figure 7A As shown, the first grid group 61 includes multiple spaced first grid units (e.g., k11 and k12 form one first grid unit, and k13 and k14 form another first grid unit). Each first grid unit includes two grids, and N1 is 2. A diamond-shaped grid is spaced between two adjacent first grid units. Therefore, the first spacing L1 is equal to the length of the diamond-shaped grid along the circumferential direction of the microcatheter 100, and M1 is 1.

[0047] Continue reading Figure 7A In the second grid group 62, the grids (such as marked k21, k22, k23) are not interrupted by laser to form intervals. The second grid unit can be defined to include N2 adjacent grids. At this time, N2 can take the value of positive integers such as 1, 2, 3. At the same time, since there is no laser interruption, the interval between two adjacent second grid units is zero. At this time, M2 takes the value of 0.

[0048] In another alternative embodiment, such as Figure 8A As shown, the first grid group 61 includes multiple spaced first grid units (e.g., k11, k12, and k13 form one first grid unit, and k14, k15, and the undrawn rhombus grid form another first grid unit). Each first grid unit includes three rhombus grids, and N1 is 3 in this case. Two adjacent first grid units are separated by one rhombus grid, therefore the first spacing L1 is equal to the length of the rhombus grid along the circumferential direction of the microcatheter 100, and M1 is 1 in this case.

[0049] Continue reading Figure 8A In the second grid group 62, the grids (such as marked k21 and k22) are not interrupted by laser to form intervals. The second grid cell can be defined to include N2 adjacent grids. At this time, N2 can take the value of positive integers such as 1, 2, and 3. At the same time, since there is no laser interruption, the interval between two adjacent second grid cells is zero. At this time, M2 takes the value of 0.

[0050] In another alternative embodiment, such as Figure 9A As shown, the first grid group 61 includes multiple spaced first grid cells (as labeled k11, k12), each first grid cell including a rhombus grid, where N1 is 1. Two adjacent first grid cells are spaced two rhombus grids apart, therefore the first spacing L1 is equal to the sum of the lengths of the two rhombus grids along the circumferential direction of the microcatheter 100, where M1 is 2.

[0051] Continue reading Figure 9AThe second grid group 62 includes multiple spaced second grid units (e.g., k21 and k22 form one second grid unit, and k23 and k24 form another second grid unit). Each second grid unit includes two rhombic grids, and N2 is 2. A rhombic grid separates two adjacent second grid units, so the second spacing L2 is equal to the length of the rhombic grid along the circumferential direction of the microcatheter 100, and M2 is 1.

[0052] In another alternative embodiment, such as Figure 10A As shown, the first grid group 61 includes multiple spaced first grid cells (e.g., labeled k11, k12, k13), each first grid cell including a rhombus grid, where N1 is 1. In some cases, two adjacent first grid cells are separated by a gap of two rhombus grids (e.g., two rhombus grids between k11 and k12), where the first gap L1 is equal to the sum of the lengths of the two rhombus grids along the circumferential direction of the microcatheter 100; in other cases, two adjacent first grid cells are separated by a gap of one rhombus grid (e.g., one rhombus grid between k12 and k13), where the first gap L1 is equal to the length of one rhombus grid along the circumferential direction of the microcatheter 100. In these cases, M1 is 1 and 2 respectively.

[0053] Continue reading Figure 10A The second grid group 62 includes multiple spaced second grid units (e.g., k22, k23, k24, and k25 form one second grid unit, and k21 and three other undrawn grids form another second grid unit). Each second grid unit includes four rhombus grids, and N2 is set to 4. Two adjacent second grid units are separated by a rhombus grid; therefore, the second spacing L2 is equal to the length of the rhombus grid along the circumferential direction of the microcatheter 100, and M2 is set to 1.

[0054] In another alternative embodiment, such as Figure 11A As shown, the first grid group 61 includes multiple spaced first grid units (e.g., k12 and k13 form one first grid unit, k14 and an undrawn rhombus grid form one first grid unit, and k11 and an undrawn rhombus grid form another first grid unit). Each first grid unit includes two rhombus grids, and N1 is 2 in this case. Two rhombus grids separate two adjacent first grid units, so the first spacing L1 is equal to the sum of the lengths of the two rhombus grids along the circumferential direction of the microcatheter 100, and M1 is 2 in this case.

[0055] Continue reading Figure 11AThe second grid group 62 includes multiple spaced second grid units (e.g., k21, k22, and k23 form one second grid unit, and k24 and the two undrawn rhombus grids form another second grid unit). Each second grid unit includes three rhombus grids, and N2 is set to 3. Adjacent second grid units are separated by one rhombus grid; therefore, the second spacing L2 is equal to the length of the rhombus grid along the circumferential direction of the microcatheter 100, and M2 is set to 1.

[0056] In another optional embodiment of this application, such as Figure 12A As shown, multiple cutoff grids are located at the same circumferential position along the axis of the microcatheter 100. A third grid group 63 is provided at the same circumferential position, and the third grid group 63 includes at least some cutoff grids (such as those marked k11, k12, and k13). A fourth grid group 64 (with grids in the fourth grid group such as those marked k21, k22, and k23) is provided on the side of the third grid group 63 near the proximal end. For ease of display, the grid edges in the third grid group 63 are thickened with solid lines, and the grid edges in the fourth grid group 64 are thickened with dashed lines. Figure 12A In the above-mentioned third grid group 63, the grids can be obtained by laser cutting the filament bundles that share a common intersection point in the four small rhomboid grids, without changing the tilt angle of the braided filament bundles. It can be considered that the size of one grid in the third grid group 63 is equal to the sum of the sizes of the four grids in the fourth grid group 64.

[0057] therefore, Figure 12A In this process, the number of grids in the fourth grid group 64 is greater than or equal to the number of grids in the third grid group 63, and the size of the grids in the fourth grid group 64 is smaller than the size of the grids in the third grid group 63. This achieves a greater grid density in the fourth grid group 64 than in the third grid group 63, thereby enabling a gradual change in stiffness at the far end of the braided layer 42 and improving the problem of sudden stress change at the tip.

[0058] This application adjusts the number of grids, grid spacing, or grid size in two adjacent grid groups at the far end of the braided layer 42 by laser cutting the filament bundle without changing the tilt angle of the braided filament bundle. This creates a grid distribution with gradually changing density at the end of the braided layer 42, thus achieving a gradual change in stiffness of the braided layer 42 towards the far end.

[0059] In the manufacturing process of the microcatheter 100 of this application, a braided layer 42 is first wound around the outer wall of the inner layer 3, and then a spring layer 41 is wound around the outer wall of the braided layer 42. The spring layer 41 is pre-shaped into a prefabricated shape that can be nested in the outer wall of the braided layer 42. Since the prefabricated spring layer 41 is nested from the distal end of the tip 2 of the microcatheter 100, it will inevitably scrape off the cut-off grid 60 at the end of the braided layer 42, causing the grid at the tip of the braided layer 42 to become loose and fail.

[0060] To further stabilize the structure of the braided layer 42 in the microcatheter 100, this application fixes the cutoff grid 60 in the braided layer 42 with solder joints in the above embodiments, as follows: like Figures 5B to 12B Each cutoff grid 60 includes a first intersection point 423 near the proximal end, a second intersection point 424 near the distal end, and a third intersection point 425 and a fourth intersection point 426 along the same circumferential direction of the microcatheter 100; along the axial direction, the third intersection point 425 and the fourth intersection point 426 are located between the first intersection point 423 and the second intersection point 424, wherein the multiple strands of filaments at the second intersection point 424 are fixed to each other to form a solder joint 7.

[0061] In this application, "weld point" refers to the connection structure formed by fixing multiple strands of wire at the second intersection 424 to each other. The weld point 7 can be formed by adhesive bonding, hot melt connection, ultrasonic welding, or laser welding. After the multiple strands of wire at the second intersection 424 are fixed to each other to form the weld point 7, there may be a rough edge outside the weld point 7 that does not form another closed grid with other strands of wire.

[0062] In one alternative embodiment, for Figure 5A The distribution of multiple cutoff grids 60 at the same circumferential position along the axis of the microcatheter 100, and the arrangement of solder joints 7 are as follows: Figure 5B As shown. Figure 5B In the middle, a weld point 7 is formed at the second intersection point 424 of each cutoff grid 60, and multiple weld points 7 are located in the same axial position. Figure 5B In this embodiment, a weld point 7 is formed at the second intersection point 424 of each cutoff grid. This improves the structural stability of the braided layer 42 without requiring a developing ring to reinforce the cutoff grid 60. Furthermore, compared to reinforcement with a developing ring, this embodiment, by forming weld points 7 at the second intersection point 424 of the cutoff grid 60, also helps to reduce the outer diameter of the tip 2. In addition, the multiple weld points 7 are diffusely distributed along the circumference of the microcatheter 100, which also prevents the failure of a single weld point 7 from spreading to adjacent weld points 7.

[0063] In another optional embodiment, for the distribution of multiple cutoff grids 60 at at least two different circumferential positions along the axial direction of the microcatheter 100, a weld point 7 is formed at the second intersection 424 of each cutoff grid 60. Multiple weld points 7 are located at at least two different axial positions. It can be understood that in this application, the same circumferential position along the axial direction of the microcatheter means that the circumferential direction is perpendicular to the axial direction. Multiple weld points located at the same circumferential position are located at the same axial position. Multiple weld points located at different circumferential positions must be set at at least two different axial positions.

[0064] like Figures 6B to 8B As shown, for Figures 6A to 8A The distribution of multiple cutoff grids 60 is such that each cutoff grid 60 has a solder joint 7 formed at its second intersection 424. Some solder joints 7 are located at a first position along the axial direction of the microcatheter 100 (e.g., solder joints at k12 and k13), while others are located at a second position along the axial direction of the microcatheter 100 (e.g., solder joints at k21 and k22). The second position is located on the side of the first position closer to the proximal end. Therefore... Figures 6B to 8B In the process, multiple solder points 7 are located at two positions along the axial direction of the microcatheter 100. Furthermore, Figure 6B In the first position, there are three diamond-shaped grids between two adjacent solder points 7, and one diamond-shaped grid between two adjacent solder points 7 at the second position, which can make multiple solder points 7 at the far end of the braided layer 42 form a gradient distribution.

[0065] like Figures 9B to 11B As shown, for Figures 9A to 11A The distribution of multiple cutoff grids 60 in the middle, with each cutoff grid 60 having a weld point 7 formed at its second intersection 424. Because... Figures 9A to 11A In the process, besides being distributed in the first grid group 61 and the second grid group 62, some cutoff grids 60 are also distributed in the grid group on the side of the second grid group furthest from the first grid group. Therefore, Figures 9B to 11B In the microcatheter 100, the first part of the solder joint 7 is located at a first position near the distal end along the axial direction (e.g., solder joints at k11 and k12), the second part of the solder joint 7 is located at a second position near the proximal end of the first position (e.g., solder joints at k22 and k23), and the third part of the solder joint 7 is located at a third position near the proximal end of the second position (e.g., solder joints at k31 and k32). Therefore... Figures 9B to 11B In the middle, multiple solder points 7 are located at three positions along the axial direction of the microcatheter.

[0066] The above Figures 6B to 11B In the process, a weld point 7 is formed at the second intersection 424 of each cutoff grid 60, which can reinforce the cutoff end of the braided layer 42. Moreover, multiple weld points 7 are located at at least two different positions in the axial direction of the microcatheter 100. The weld points 7 are set in a non-flush manner at the far end of the braided layer 42, which can also improve the stress concentration caused by the concentrated distribution of weld points 7, and further improve the stability of the microcatheter 100 in use.

[0067] In another alternative embodiment, for Figure 12A The distribution of multiple cutoff grids 60 is such that, since the grids in the third grid group 63 (such as k11, k12, k13, and k14) are all cutoff grids with two exposed edges, therefore... Figure 12BIn the third grid group 63, each cutoff grid 60 has a weld point 7 formed at its second intersection 424. In addition, Figure 12A In the fourth grid group 64, each edge of the grids (such as k21, k22, and k23) is shared with adjacent grids, and no edges are exposed. Therefore, the grids in the fourth grid group 64 are not the cutoff grids defined in this application. Some strands of the grids in the fourth grid group 64 terminate at intersections, and these strands do not continue to be woven into another grid. For example, the first strand 421 of k23 in the fourth grid group 64 terminates at the third intersection 425, and the second strand 422 terminates at the fourth intersection 426. Therefore, to improve the structural stability of the grids in the fourth grid group 64, such as... Figure 12B As shown, in the fourth grid group 64, the third intersection point 425 and the fourth intersection point 426 of the grid also form the weld point 7.

[0068] The structural design of the spring layer 41 in this application will be described below with reference to the accompanying drawings: Typically, the spring layer 41 is formed by winding spring wire in a helical manner. Exemplarily, the spring wire of the spring layer 41 can be a metal wire. For example, the spring wire of the spring layer 41 may include stainless steel wire or nickel-titanium alloy wire.

[0069] In one optional embodiment, the distal end of the spring layer 41 includes a plurality of hollow structures 411 formed by breaking the spring wire, and the distribution density of the plurality of hollow structures 411 gradually increases from the proximal end toward the distal end, such as... Figure 13A As shown, the length of the hollow structure 411 along the extension direction of the spring wire is consistent. From the proximal end to the distal end, the spacing between two adjacent hollow structures 411 along the axial direction of the microcatheter 100 gradually decreases. For example, three equal-length spring wires are cut and removed from the spring layer 41 to form three hollow structures 411; along the direction from the distal end to the proximal end, they are named the first hollow structure, the second hollow structure, and the third hollow structure, respectively; the spacing between the first hollow structure and the second hollow structure is the third distance D1, and the spacing between the second hollow structure and the third hollow structure is the fourth distance D2, where D1 < D2. Thus, the distribution density of the multiple hollow structures 411 gradually increases along the direction from the main body 1 to the tip 2.

[0070] In another alternative embodiment, such as Figure 13BAs shown, the spacing between two adjacent hollow structures 411 along the axial direction of the microcatheter 100 is equal. From the proximal end to the distal end, the length of multiple hollow structures 411 gradually increases along the extension direction of the spring wire. For example, three sections of spring wire are cut and removed at equal intervals on the spring layer 41 to form three hollow structures; along the direction from the distal end to the proximal end, they are named the first hollow structure, the second hollow structure, and the third hollow structure, respectively; the spacing between the first hollow structure and the second hollow structure is the third distance D1, and the spacing between the second hollow structure and the third hollow structure is the fourth distance D2, where D1=D2; the length of the first hollow structure > the length of the second hollow structure > the length of the third hollow structure. Thus, the distribution density of multiple hollow structures 411 gradually increases along the direction from the main body 1 to the tip 2.

[0071] In the above Figure 13A and Figure 13B In the technical solution, multiple hollow structures 411 are formed at the distal end of the spring layer 41, and the distribution density of the multiple hollow structures 411 gradually increases along the direction from the main body 1 toward the tip 2. The greater the distribution density of the hollow structures 411, the lower the rigidity, which in turn causes the distal end of the spring layer 41 to form a gradual change in rigidity along the direction from the main body 1 toward the tip 2, further reducing the stress concentration at the junction of the main body 1 and the tip 2, and improving the bending resistance of the microcatheter 100.

[0072] The structural design of the outer layer in this application is described below with reference to the accompanying drawings: In one optional embodiment, the outer layer 5 of the main body 1 includes a plurality of sub-segments distributed along the axial direction of the microcatheter 100, wherein the hardness of the sub-segments near the proximal end is greater than that of the sub-segments near the distal end, and the length of the sub-segments near the proximal end is less than that of the sub-segments near the distal end.

[0073] like Figure 1 As shown, multiple sub-segments include a first segment 53, a second segment 54, a third segment 55, a fourth segment 56, and a fifth segment 57, which are distributed axially from the proximal end to the distal end of the microcatheter 100. The hardness of the first segment 53, the second segment 54, the third segment 55, the fourth segment 56, and the fifth segment 57 decreases sequentially. The lengths of the first segment 53, the second segment 54, the third segment 55, and the fifth segment 57 decrease sequentially. The length of the fourth segment 56 is greater than the lengths of the third segment 55 and the fifth segment 57, and less than the length of the second segment 54.

[0074] For example, the first pipe section 53 has a hardness of 78D~85D and a length of 700mm~1000mm, the second pipe section 54 has a hardness of 70D~75D and a length of 300mm~400mm, the third pipe section 55 has a hardness of 50D~60D and a length of 80mm~120mm, the fourth pipe section 56 has a hardness of 40D~45D and a length of 120mm~200mm, and the fifth pipe section 57 has a hardness of 30D~35D and a length of 50mm~90mm.

[0075] In the above technical solution, the proximal first segment 53 has high rigidity and a long length (e.g., a 900mm long 80D high-rigidity segment), which can provide sufficient axial pushing force and torque transmission for the microcatheter 100, facilitating the rapid advancement of the microcatheter 100 in large blood vessels such as the aorta and iliac arteries. A second segment 54 is provided distal to the first segment 53. The second segment 54 has lower rigidity and length than the first segment 53, creating a gradual change in rigidity. A third segment 55 is provided distal to the second segment 54. The third segment 55 has further reduced rigidity and a shorter length (e.g., a 90mm long 55D hardness segment), which can quickly reduce the bending stiffness of the catheter at the beginning of a sharp bend in the blood vessel, allowing the catheter to conform to the direction of the blood vessel. A fourth segment 56 is positioned distal to the third segment 55. The fourth segment 56 has a lower hardness than the third segment 55, but its length is longer (e.g., a 150mm long 40D hardness segment). This longer, lower-hardness segment provides a gentler flexibility gradient, allowing the catheter to smoothly deform gradually as it passes through multiple bends in the blood vessel, reducing irritation to the vessel wall. Subsequently, a fifth segment 57, with even lower hardness and shorter length, is positioned distal to the fourth segment 56. The fifth segment 57 is close to the tip 2, creating a hardness gradient between the main body 1 and the tip 2, thus mitigating stress concentration.

[0076] In summary, the embodiments of this application control the hardness of the third segment 55 near the proximal end to be greater than the hardness of the fourth segment 56 near the distal end, and the length of the third segment 55 near the proximal end to be less than the length of the fourth segment 56 near the distal end. This allows the transition of hardness from 50D~60D to 40D~45D to be achieved smoothly over a longer axial distance. This enables the catheter to maintain efficient proximal pushing force while improving the progressive compliance of the catheter in tortuous blood vessels and reducing the risk of stress concentration and kinking.

[0077] The materials of the different pipe sections can be adjusted according to the hardness requirements, and this application does not impose any limitations. For example, the material of the outer layer 5 includes nylon, Pebax, TPU, etc.

[0078] Furthermore, in an optional embodiment, the material forming the outer layer 5 also contains a developer, such as barium sulfate, tungsten powder, etc., to obtain development tracking capability. Exemplarily, the portion of the outer layer 5 corresponding to the main body 1 contains barium sulfate, and the portion of the outer layer 5 corresponding to the tip 2 contains tungsten powder.

[0079] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A microcatheter, characterized in that, include: The main body portion is disposed at the proximal end and the tip portion is disposed at the distal end, wherein the outer diameter of the tip portion is smaller than the outer diameter of the main body portion; The microcatheter also includes an inner layer, a reinforcing layer, and an outer layer, which are sequentially arranged from the inside out; The inner layer extends from the main body to the distal end of the tip, and the inner layer has a first transition section in which the inner diameter gradually decreases from the proximal end toward the distal end; The reinforcing layer is wound around the outer wall of the inner layer, and the reinforcing layer includes a braided layer and a spring layer arranged in the radial direction of the inner layer; The outer layer covers the outside of the reinforcing layer and the inner layer.

2. The microcatheter according to claim 1, characterized in that, The spring layer is located in the main body portion, and the distal end of the spring layer does not extend beyond the boundary between the main body portion and the tip portion; and / or, The woven layer extends from the main body portion to the tip portion; And / or, The first transition segment is located at at least one of the main body portion and the tip portion; optionally, the first transition segment is located in the main body portion; and / or, The outer layer has a second transition section and a third transition section whose outer diameter gradually decreases from the proximal end to the distal end. The second transition section is located in the main body portion, and the third transition section is located in the tip portion. Optionally, the outer layer further has a constant outer diameter section located between the second transition section and the third transition section, the constant outer diameter section extending from the body portion to the tip portion; Optionally, the taper of the second transition section is greater than the taper of the third transition section.

3. The microcatheter according to claim 1, characterized in that, The woven layer comprises a closed, polygonal mesh formed by multiple strands of yarn intersecting. The mesh includes a cut-off mesh located on the far end side of the braided layer and exposing at least one side, wherein the far end of the braided layer terminates at the location of the cut-off mesh; The plurality of cutoff grids are located at at least one circumferential position axially above the microcatheter; Optionally, the shape of the grid is one of triangle, quadrilateral, pentagon or hexagon; Optionally, the grid is rhomboid in shape.

4. The microcatheter according to claim 3, characterized in that, The plurality of said cutoff grids are located at at least two different circumferential positions along the axial direction of the microcatheter; A first grid group near the far end and a second grid group near the near end are provided at at least two different circumferential positions. The first grid group and the second grid group each include a plurality of grids distributed circumferentially. At least a portion of the grids included in the first grid group and the second grid group are cut-off grids. The density of the grid in the second grid group is greater than the density of the grid in the first grid group; Optionally, the number of grids in the second grid group is greater than the number of grids in the first grid group.

5. The microcatheter according to claim 4, characterized in that, The first grid group includes a plurality of spaced first grid cells, and the first grid cell includes N1 adjacent grids; The spacing between two adjacent first grid cells is the first spacing, which is M1 times the length of the grid along the circumferential direction of the microcatheter, where N1 and M1 are both non-zero natural numbers. Optionally, N1 is at least one of 1, 2, 3, 4 or 5; Optionally, M1 is at least one of 1, 2, or 3.

6. The microcatheter according to claim 5, characterized in that, The second grid group includes a plurality of second grid cells, and the second grid cell includes N2 adjacent grids; The spacing between two adjacent second grid cells is the second spacing, which is M2 times the length of the grid along the circumferential direction of the microcatheter, where N2 is a positive integer and M2 is an integer greater than or equal to 0; Optionally, N2 is at least one of 1, 2, 3 or 4; M2 is at least one of 0, 1 or 2.

7. The microcatheter according to claim 3, characterized in that, Multiple cutoff grids are located at the same circumferential position along the axis of the microcatheter, a third grid group is provided at the same circumferential position, the third grid group includes at least a portion of the cutoff grids, and a fourth grid group is provided on the side of the third grid group near the proximal end; The grid density of the fourth grid group is greater than the grid density of the third grid group; Optionally, the number of grids in the fourth grid group is greater than or equal to the number of grids in the third grid group, and the size of the grids in the fourth grid group is smaller than the size of the grids in the third grid group.

8. The microcatheter according to any one of claims 3 to 7, characterized in that, Each of the cutoff grids includes a first intersection point near the proximal end, a second intersection point near the distal end, and a third and fourth intersection points distributed along the same circumferential direction of the microcatheter. At the second intersection, multiple strands of wire are fixed together to form a solder joint.

9. The microcatheter according to claim 8, characterized in that, Multiple cutoff grids are located at the same circumferential position along the axis of the microcatheter, and the solder joints are located at the same axial position; Alternatively, the plurality of said cutoff grids are located at at least two different circumferential positions along the axis of the microcatheter, and the solder joints are located at at least two different axial positions.

10. The microcatheter according to claim 1, characterized in that, The distal end of the spring layer includes multiple hollow structures formed by breaking the spring wire, and the distribution density of the multiple hollow structures gradually increases along the direction from the main body to the tip. Optionally, the length of the hollow structure along the extension direction of the spring wire is consistent, and the spacing between two adjacent hollow structures gradually decreases along the axial direction of the microcatheter from the proximal end to the distal end. Optionally, the spacing between two adjacent hollow structures along the axial direction of the microcatheter is equal, and the length of the plurality of hollow structures gradually increases along the extension direction of the spring wire from the proximal end to the distal end.

11. The microcatheter according to claim 1, characterized in that, The outer layer located in the main body includes a plurality of sub-segments distributed along the axial direction of the microcatheter. The sub-segments near the proximal end have a higher hardness than the sub-segments near the distal end, and the length of the sub-segments near the proximal end is shorter than the length of the sub-segments near the distal end. Optionally, the plurality of sub-segments include a first segment, a second segment, a third segment, a fourth segment, and a fifth segment distributed axially from the proximal end of the microcatheter toward the distal end, wherein the hardness of the first segment, the second segment, the third segment, the fourth segment, and the fifth segment decreases sequentially; the lengths of the first segment, the second segment, the third segment, and the fifth segment decrease sequentially, and the length of the fourth segment is greater than the lengths of the third segment and the fifth segment, and less than the length of the second segment; Optionally, the first pipe segment has a hardness of 78D~85D and a length of 700mm~1000mm, the second pipe segment has a hardness of 70D~75D and a length of 300mm~400mm, the third pipe segment has a hardness of 50D~60D and a length of 80mm~120mm, the fourth pipe segment has a hardness of 40D~45D and a length of 120mm~200mm, and the fifth pipe segment has a hardness of 30D~35D and a length of 50mm~90mm.

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