Lumen stent

Abstract

The application provides a lumen stent, which comprises a tubular body with a plurality of axial planes and a semi-releasing device connected to the tubular body, wherein the semi-releasing device comprises a limiting rod and a plurality of binding lines arranged on the tubular body, the plurality of binding lines are detachably connected with the limiting rod, when the plurality of binding lines are connected with the limiting rod, the plurality of binding lines constrain the tubular body in the circumferential direction, and the limiting rod extends along a curve between two adjacent binding lines, and the rod bodies of the two adjacent binding lines are located in at least two axial planes. In the lumen stent, the binding lines constrain the lumen stent in the circumferential direction, so that the lumen stent can be in a semi-releasing state, thereby adjusting and positioning the lumen stent, and improving the accuracy of axial and circumferential positioning of the lumen stent.

Description

Technical Field

[0001] This invention relates to the field of interventional medical device technology, and in particular to a lumen stent. Background Technology

[0002] Over the past decade, endovascular aortic stent graft repair has been widely used for lesions such as aneurysms and aortic dissections in the thoracic and abdominal aortas. Its efficacy is definite, minimally invasive, allows for rapid recovery, and has few complications, making it a first-line treatment method. During the procedure, under X-ray fluoroscopic guidance, the stent graft is delivered to the lesion site using a suitable delivery system. The stent graft isolates blood flow from the lesion, eliminating the influence of blood pressure on the lesion and achieving a cure.

[0003] To address the issue of stent placement within the body, radiopaque markers are typically placed at key locations on the stent to determine its axial and circumferential positioning. However, when the stent is compressed within the delivery catheter, it exhibits circumferential compression wrinkles and axial elongation. Using radiopaque markers for positioning under these conditions can result in significant circumferential and axial deviations. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a lumen stent in view of the above-mentioned defects of the prior art.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] An embodiment of the present invention provides a lumen stent, including a tubular body having multiple axial planes and a semi-release device connected to the tubular body. The semi-release device includes a limiting rod and multiple binding lines disposed on the tubular body. The multiple binding lines are detachably connected to the limiting rod. When the multiple binding lines are connected to the limiting rod, the multiple binding lines circumferentially constrain the tubular body, and the limiting rod extends along a curve between two adjacent binding lines. The point of the limiting rod on the rod body between two adjacent binding lines is located in at least two different axial planes.

[0007] The aforementioned lumen stent is equipped with a semi-release device, which includes a limiting rod and binding lines disposed on the tubular body. Multiple binding lines are detachably connected to the limiting rod. When multiple binding lines are connected to the limiting rod, the binding lines circumferentially constrain the lumen stent, allowing the lumen stent to be in a semi-released state for adjustment and positioning, thus improving the accuracy of axial and circumferential positioning of the lumen stent. When the binding lines circumferentially constrain the lumen stent, the limiting rod extends along a curve between two adjacent binding lines. The point on the rod body between two adjacent binding lines is located in at least two different axial planes, which increases the stroke required for the proximal end of the limiting rod to release the connection between the limiting rod and the binding lines, thereby preventing premature release of the semi-release device due to misoperation. Attached Figure Description

[0008] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0009] Figure 1 This is a perspective view of the lumen stent in its natural state according to the first embodiment of the present invention.

[0010] Figure 2 This is a perspective view of the lumen stent in the semi-released state in the first embodiment of the present invention.

[0011] Figure 3 yes Figure 2 A magnified view of A in the middle.

[0012] Figure 4 This is a perspective view of the lumen stent in a semi-released state according to another embodiment of the present invention.

[0013] Figure 5 yes Figure 4 A magnified view of B in the middle.

[0014] Figure 6 This is a partial structural diagram of the lumen support in its natural state according to the first embodiment of the present invention.

[0015] Figure 7 This is a partial structural diagram of the lumen support in the compressed state according to the first embodiment of the present invention.

[0016] Figure 8 This is a perspective view of the lumen stent in its natural state according to the second embodiment of the present invention.

[0017] Figure 9 This is a perspective view of the lumen stent in the semi-released state in the second embodiment of the present invention.

[0018] Figure 10 This is a perspective view of the lumen support in its natural state according to the third embodiment of the present invention.

[0019] Figure 11 This is a perspective view of the lumen stent in the semi-released state in the third embodiment of the present invention. Specific Implementation

[0020] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0021] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] It should be noted that in this application, the end of the stent closer to the heart after deployment is defined as the proximal end, and the end farther from the heart is defined as the distal end; "proximal" refers to the side that is relatively closer to the heart, and "distal" refers to the side that is relatively farther from the heart.

[0024] Please see Figure 1 This embodiment provides a lumen stent 100, including a tubular body 110 and a semi-release device 130 connected to the tubular body 110.

[0025] The tubular body 110 is a tubular structure through which blood can flow, and it has multiple axial planes (not shown). The tubular body 110 is radially compressible to facilitate insertion into a delivery catheter with a small outer diameter for delivery. The tubular body 110 is radially self-expanding. When the delivery catheter releases the radial constraint on the tubular body 110, the tubular body 110 can self-expand and anchor itself in the blood vessel.

[0026] The semi-release device 130 includes a limiting rod 131 and multiple binding lines 133 disposed on the tubular body 110. The limiting rod 131 is movable relative to the tubular body 110.

[0027] Multiple binding lines 133 are detachably connected to the limiting rod 131. Please refer to [link / reference]. Figure 2 When multiple binding lines 133 are connected to the limiting rod 131, the multiple binding lines 133 circumferentially constrain the tubular body 110, so that the lumen stent 100 can be in a semi-released state. At this time, the lumen stent 100 is not attached to the blood vessel wall, and the operator can still adjust the axial and circumferential position of the lumen stent 100. After the positioning is accurate, the constraint of the semi-release device 130 is released, so that the lumen stent 100 unfolds and attaches to the wall.

[0028] Furthermore, when the binding line 133 circumferentially constrains the lumen stent 100 (i.e., when the lumen stent 100 is in a semi-released state), the rod of the limiting rod 131 between two adjacent binding lines 133 is located in only one axial plane, that is, the rod of the limiting rod 131 coincides with a generatrix of the tubular body 110, and the shortest distance between two adjacent binding lines 133 is the distance along the generatrix of the tubular body 110. In this embodiment, when the multiple binding lines 133 circumferentially constrain the lumen support 100, the limiting rod 131 extends along a curve between two adjacent binding lines 133. The point of the limiting rod 131 on the rod body between two adjacent binding lines 133 is located in at least two different axial planes. Compared with the limiting rod 131 being located in only one axial plane between two adjacent binding lines 133, this embodiment can increase the stroke required at the proximal end of the limiting rod 131 when the limiting rod 131 moves relative to the tubular body 110 to release the connection with the binding line 133, thereby preventing the premature release of the semi-release device 130 due to misoperation.

[0029] Furthermore, when the stent 100 is located in a tortuous blood vessel, such as in the aortic arch, the stent 100 needs to bend to adapt to the curvature of the aortic arch. During the bending deformation of the tubular body 110, the portion on the greater curvature side will be elongated. The length of the limiting rod 131 does not change during bending. If the limiting rod 131 is located on the greater curvature side, the proximal end of the limiting rod 131 may move distally to the tubular body 110, potentially leading to premature release of the restraint line 133.

[0030] Please see Figure 1 The tubular body 110 includes a first region and a second region distributed along the circumference. The limiting rod 131 extends within the first region, and the center angle of the first region is 180°.

[0031] The tubular body 110 is provided with a branch opening 125. When the lumen stent 100 is implanted, the branch opening 125 is aligned with the branch vessel opening.

[0032] In this embodiment, the central angle of the first region is 90°. If the stent has a branch opening, the 90° central angle of the first region prevents the limiting rod 131 from getting too close to the branch opening 125. If the limiting rod 131 is close to or passes through the branch opening 125, the branch guidewire may pass through the gap between the limiting rod 131 and the tubular body when establishing the delivery path of the branch stent with the branch guidewire. This would prevent the branch guidewire from entering the branch blood vessel. Therefore, the 90° central angle of the first region can increase the probability of the branch guidewire entering the branch blood vessel.

[0033] The binding thread 133 can be a flexible thread with high tensile strength, such as polyester suture thread. The binding thread 133 can be composed of a single flexible thread or multiple flexible threads. The binding thread 133 is arranged along the circumference of the tubular body 110.

[0034] In this embodiment, the binding thread 133 can be a flexible thread with strong tensile strength, such as PTFE thread or polyester suture thread.

[0035] Please see Figure 2 The binding line 133 includes a fixed part 135, a binding part 137 and a locking part 139 connected together. The fixed part 135 is fixedly connected to the tubular body 110.

[0036] The fixing part 135 can be fixed to the tubular body 110 by knotting or sewing. The binding part 137 of the binding line 133 can be composed of a single flexible line or multiple flexible lines.

[0037] Please see Figure 3 The locking part 139 is detachably connected to the limiting rod 131. The locking part 139 can be selected, but is not limited to, a binding wire 133 loop, a metal ring, etc. In this embodiment, the locking part 139 is a ring structure formed by the binding wire 133. The limiting rod 131 can pass through the ring structure or the semi-circular ring structure, thereby achieving a detachable connection with the limiting rod 131.

[0038] Please refer to the following: Figure 2 and Figure 3 When the locking part 139 is connected to the limiting rod 131, and the limiting rod 131 passes through the gap between the binding part 137 and the tubular body 110, the binding line 133 circumferentially restrains the tubular body 110.

[0039] When the binding line 133 binds the tubular body 110, the locking part 139 is located near or far from the fixing part 135. In this embodiment, the locking part 139 is located near the fixing part 135. From the far end to the near end, the fixing part 135 and the binding part 137 connected to the fixing part 135 can limit the locking and prevent the locking part 139 from sliding near the near end. The rod of the limiting rod 131 extends obliquely. If the locking part 139 slides along the limiting rod 131 to the far end of the tubular body 110, the radial constraint force generated by the binding line 133 on the tubular body 110 increases. Since the tubular support has a self-expansion force, under no external force, the self-expansion force of the tubular support can prevent the locking part 139 from sliding far from the far end along the rod of the limiting rod 131, thereby achieving self-locking.

[0040] Please see Figure 4 and Figure 5As shown, in other embodiments, when the locking part 139 is located far from the fixing part 135, if the locking part 139 slides along the limiting rod 131 toward the proximal side of the tubular body 110, the radial constraint force generated by the binding line 133 on the tubular body 110 increases, thereby achieving the above-mentioned self-locking.

[0041] The limiting rod 131 can be made of a metal guide wire with good elastic memory and low surface roughness, such as nickel-titanium wire, which meets the physical requirements and has good biocompatibility with the human body. The diameter of the limiting rod 131 can be selected from 0.2mm to 0.6mm to ensure that the diameter of the limiting rod 131 is appropriate. This avoids increasing the overall profile (outer contour dimension) of the lumen support 100 if the diameter of the limiting rod 131 is too large, while insufficient support force if the diameter of the limiting rod 131 is too small, affecting the constraint effect on the locking part 139.

[0042] In this embodiment, the surface roughness of the limiting rod 131 is less than or equal to 0.2 μm, so that the limiting rod 131 can be smoothly pulled out from the locking part 139, thereby releasing the constraint on the locking part 139.

[0043] In this embodiment, a guide head (not shown) is provided at the proximal end of the limiting rod 131. The guide head is used to guide the limiting rod 131 and the restraint line 133 to be detachably connected, and the guide head is used to reduce the damage to blood vessels caused by the limiting rod 131.

[0044] The guide head is a soft tip located proximal to the limiting rod 131; thus, the soft tip prevents damage to the blood vessel from the proximal end of the limiting rod 131. Specifically, the length of the soft tip is set to 10mm to 20mm. This setting maintains the constraint of the limiting rod 131 on the locking part 139 while preventing damage to the blood vessel from the limiting rod 131. If the soft tip is too long, part of the soft tip may be in the position where the limiting rod 131 constrains the restraint line 133, which may cause the locking part 139 to loosen from the limiting rod 131 due to insufficient support. If the soft tip is too short, the soft tip lacks flexibility and is prone to damaging the blood vessel.

[0045] In other embodiments, the guide head is a ball head formed at the proximal end of the limiting rod 131. For example, when the limiting rod 131 is made of metal guide wire, the ball head can be formed at the proximal end of the limiting rod 131 by spot welding.

[0046] The diameter of the ball head can be 100% to 150% of the diameter of the limiting rod 131. Guide wires with poor elastic memory are prone to bending after being subjected to force, which will lead to increased resistance when withdrawing the guide wire; the diameter of the ball head is 0.3mm to 0.6mm.

[0047] The guidewire diameter should not be too large or too small. If it is too large, it will increase the overall profile (outer contour size) of the stent; if it is too small, the support will be insufficient to restrain the ends of the long cord. If the diameter of the proximal bulb of the guidewire is less than 0.3 mm, it is easy to puncture blood vessels. If the diameter is more than 150% larger than the guidewire diameter, it will cause the guidewire to get stuck between the bulb and the long cord when it is withdrawn, making it difficult to release smoothly.

[0048] Please refer to it again. Figure 1 The semi-release device 130 also includes a limiting ring 141, which is disposed on the surface of the tubular body 110. In this embodiment, the binding line 133 and the limiting ring 141 are disposed on the outer surface of the tubular body 110. In other embodiments, the binding line 133 and the limiting ring 141 are disposed on the inner surface of the tubular body 110.

[0049] The restraint line 133 passes through the limiting ring 141, which allows the restraint line 133 to uniformly compress the tubular body 110, improving the overall positioning accuracy of the stent. Furthermore, when the lumen stent 100 is compressed inside the delivery conduit or when the restraint line 133 releases its constraint on the lumen stent 100, the limiting ring 141 can also prevent the restraint line 133 from axially shifting.

[0050] The size of the limiting ring 141 is 100% to 200% of the maximum cross-sectional area of ​​the binding line 133. If the size of the limiting ring 141 is too large, the axial movement range of the binding line 133 will be large, which will affect the radial compression effect of the support. If the size of the limiting ring 141 is too small, it will increase the friction between the limiting ring 141 and the binding line 133, which will affect the relative movement of the binding line 133 and the limiting ring 141 along the circumference of the tubular body 110, which is not conducive to the smooth deployment of the lumen support 100.

[0051] The number of limiting rings 141 can be multiple. Multiple limiting rings 141 are evenly distributed on the tubular body 110 along the circumference of the tubular body 110, thereby using multiple limiting rings 141 to hang the binding line 133 on the surface of the tubular body 110, which has a good limiting effect on the binding line 133, thereby improving the stability and accuracy of the binding line 133 in the circumferential constraint of the tubular body 110.

[0052] Please see Figure 6In this embodiment, the tubular body 110 includes multiple wave-shaped rings 111. Each wave-shaped ring 111 includes multiple peaks 113, multiple troughs 115, and multiple connecting rods 117 that connect adjacent peaks 113 and troughs 115 respectively. The multiple wave-shaped rings 111 are arranged sequentially from the proximal end to the distal end, preferably in parallel and spaced order. The wave-shaped rings 111 are closed cylindrical structures. The multiple wave-shaped rings 111 can have the same or similar waveform shapes. It is understood that this embodiment does not limit the specific structure of the wave-shaped rings 111. The waveform of the wave-shaped rings 111 can be set as needed, and the number of waveforms and the waveform height in each wave-shaped ring 111 can also be set as needed.

[0053] A membrane 119 is attached to the multi-turn wavy ring 111. The multi-turn wavy ring 111 is made of a biocompatible material, such as nickel-titanium or stainless steel. The membrane 119 is made of a biocompatible polymer material, such as PET or PTFE.

[0054] If the distance between the two limiting rings 141 (i.e., the arc length along the circumference of the tubular body 110 is m) is too long, when the lumen stent 100 is in a completely radially compressed state within the delivery conduit, the binding line 133 will be loose. The binding line 133 between the two limiting rings 141 will shift axially, even crossing the trough 115 of the corrugated annulus 111 and hooking onto it. When the lumen stent 100 is completely released from the delivery conduit, the binding line 133 hooking onto the corrugated annulus 111 will prevent the lumen stent 100 from deploying normally.

[0055] Please see Figure 6 and Figure 7 In the natural state (i.e. when the lumen stent 100 is fully released), the arc length of two adjacent limiting rings 141 along the circumferential direction of the tubular body 110 is m, and the vertical distance between the fixing point of the limiting ring 141 and the trough 115 located below the limiting ring 141 and closest to the limiting ring 141 is n, where m and n satisfy m≤2n, so as to prevent the binding line 133 from crossing the trough 115 of the wave-shaped ring 111 when the lumen stent 100 is in a radially compressed state.

[0056] Second Embodiment

[0057] Please see Figure 8 and Figure 9The difference between this embodiment and the first embodiment is that the binding line 233 includes a fixed part 235, a binding part 237, and two locking parts 239 connected together. The two locking parts 239 are respectively connected to both ends of the binding part 237. The fixed part 235 is located between the two locking parts 239 and is fixedly connected to the tubular body 210. Both locking parts 239 are detachably connected to the limiting rod 231. When both locking parts 239 are connected to the limiting rod 231, the binding line 233 provides circumferential restraint to the tubular body 210.

[0058] The fixing part 235 is located between the two locking parts 239, so that the binding part 237 includes two parts located on both sides of the fixing part 235. When the limiting rod 231 separates from the two locking parts 235, the two parts of the binding part 237 can simultaneously release the binding on the tubular body 210, allowing the lumen support 200 to unfold and adhere to the wall more quickly. At the same time, since the two parts of the binding part 237 are located on both sides of the fixing part 235, when the two parts of the binding part 237 release the binding on the tubular body 210, the tubular body 210 unfolds towards the fixing part 235, that is, the lumen support 200 unfolds in two opposite directions along the circumference, thereby counteracting the circumferential force generated by the lumen support 200 itself during the unfolding process, thereby improving the release stability of the lumen support 200 and making the positioning more accurate.

[0059] In this embodiment, the fixing part 235 is connected to the middle part of the binding part 237. That is, the fixing part 235 is located in the middle part of the binding part 237.

[0060] The two parts of the restraining portion 237 are of equal length, and the distances from the two locking portions 239 to the fixing portion 235 are equal along the circumference of the tubular body 210. With this structural arrangement, the two parts of the restraining portion 237 exert a similar degree of circumferential constraint on the tubular body 210. Therefore, when the limiting rod 231 separates from the locking portion 239, the two parts of the restraining portion 237 simultaneously release the circumferential constraint on the tubular body 210, and the restrained part of the tubular body 210 unfolds in two opposite directions. The circumferential force during unfolding can be well canceled out, making the release of the lumen support 200 more stable and the positioning more accurate.

[0061] Third Embodiment

[0062] Please see Figure 10 and Figure 11 In this embodiment, the limiting rod 331 is divided into multiple connected segments 331a by multiple binding lines 333.

[0063] Among the multiple binding lines 333, the one closest to the proximal end of the tubular body 310 is the proximal binding line 333, and among the multiple binding lines 333, the one closest to the distal end of the tubular body 310 is the distal binding line 333.

[0064] The difference between this embodiment and the above embodiment is that, in the region between the proximal restraint line 333 and the distal restraint line 333, the two adjacent segments 331a extend in opposite directions around the tubular body 310, which allows the limiting rod 331 to extend only in a small area, thereby preventing the rod of the limiting rod 331 from getting too close to the branch opening 325, and thus increasing the probability that the branch guidewire can smoothly enter the branch blood vessel.

[0065] If two adjacent segments 331a extend in the same circumferential direction in the tubular body 310, in order to limit the area of ​​the limiting rod 331 on the tubular body 310 (i.e., reduce the central angle corresponding to the first area), the rod body of the limiting rod 331 will tend to coincide with a generatrix of the tubular body 310. This will reduce the stroke required at the proximal end of the limiting rod 331 when releasing the connection between the limiting rod 331 and the restraint line 333, thus failing to prevent premature release of the semi-release device due to misoperation. In other words, this embodiment can both increase the probability of the branch guidewire successfully entering the branch blood vessel and prevent premature release of the semi-release device due to misoperation.

[0066] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0067] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A lumen stent, comprising a tubular body having a plurality of axial planes, and a semi-release device connected to the tubular body, characterized in that, The semi-release device includes a limiting rod and multiple binding lines disposed on the tubular body. The multiple binding lines are detachably connected to the limiting rod. When the multiple binding lines are connected to the limiting rod, the multiple binding lines circumferentially constrain the tubular body. The limiting rod extends along a curve between two adjacent binding lines. The point on the rod body between two adjacent binding lines is located in at least two different axial planes. The point on the rod body at the connection point between the limiting rod and two adjacent binding lines is located in two different axial planes.

2. The lumen stent as described in claim 1, characterized in that, The binding line includes a fixed part, a binding part, and a locking part connected together. The fixed part is fixedly connected to the tubular body, and the locking part is detachably connected to the limiting rod. When the locking part is connected to the limiting rod, and the limiting rod passes through the gap between the binding part and the tubular body, the binding line provides circumferential restraint to the tubular body.

3. The lumen stent as described in claim 2, characterized in that, When the binding line binds the tubular body, the locking part is located near or far from the fixing part. When the locking part is near the fixing part, if the locking part slides along the limiting rod toward the far side of the tubular body, the radial constraint force generated by the binding line on the tubular body increases. When the locking part is far from the fixing part, if the locking part slides along the limiting rod toward the near side of the tubular body, the radial constraint force generated by the binding line on the tubular body increases.

4. The lumen stent as described in claim 1, characterized in that, The binding line includes a fixed part, a binding part, and two locking parts connected together. The two locking parts are respectively connected to the two ends of the binding part. The fixed part is located between the two locking parts and is fixedly connected to the tubular body. Both locking parts are detachably connected to the limiting rod. When both locking parts are connected to the limiting rod, the binding line provides circumferential restraint to the tubular body.

5. The lumen stent as described in claim 4, characterized in that, The fixing part is connected to the middle part of the binding part.

6. The lumen stent as described in claim 1, characterized in that, The limiting rod is divided into multiple connected segments by multiple binding lines; Among the multiple binding lines, the one closest to the proximal end of the tubular body is the proximal binding line, and among the multiple binding lines, the one closest to the distal end of the tubular body is the distal binding line. In the region between the proximal binding line and the distal binding line, in the direction from the distal end to the proximal end, the two adjacent sections extend in opposite directions in the circumferential direction of the tubular body.

7. The lumen stent as described in claim 1, characterized in that, The tubular body includes a first region and a second region distributed along the circumference, and the limiting rod extends within the first region, with the center angle of the first region being 180°.

8. The lumen stent as described in claim 7, characterized in that, The center angle of the first region is 90°.

9. The lumen stent according to any one of claims 1 to 8, characterized in that, The tubular body is provided with a limiting ring, and the binding line passes through the limiting ring.

10. The lumen stent according to claim 9, characterized in that, The tubular body includes multiple wave-shaped rings, each wave-shaped ring including multiple peaks, multiple troughs, and multiple connecting rods that connect adjacent peaks and troughs. The number of limiting rings is multiple. In the natural state, the arc length of two adjacent limiting rings along the circumference of the tubular body is m. The vertical distance between the fixing point of the limiting ring and the trough located below the limiting ring and closest to the limiting ring is n. m and n satisfy m≤2n.

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