Expandable sheath manufacturing method

Abstract

The application discloses a manufacturing method of an expandable sheath, which comprises the following steps: folding a part of an inner tube main body to form a folded body, and attaching the folded body to the inner tube main body to form a gap; axially cutting a middle layer tube, cutting a necking and tearing opening at a distal end of the middle layer tube, inserting one side of a groove into the gap, and attaching the other side of the groove to the other side of the inner tube main body; aligning the distal end of the necking and tearing opening with the distal end of the gap, so that the distal end of the middle layer tube protrudes out of the distal ends of an inner layer tube and an outer layer tube, thereby forming a middle tube necking end head; axially cutting the outer layer tube, inserting one side of the outer layer tube into the gap, and attaching the other side of the outer layer tube to the folded body; aligning the distal ends of the outer layer tube and the inner layer tube with the proximal end of the middle tube necking end head; sleeving a heat shrink tube; and heating and cooling the heat shrink tube at high temperature to obtain the expandable sheath. The expandable sheath has an exposed necking end head, which is beneficial to protecting the inner wall of a blood vessel and to the delivery device passing through the distal end of the expandable sheath. The manufacturing method is simple and reliable.

Description

Technical Field

[0001] This invention belongs to the field of medical device technology, specifically relating to a method for manufacturing an expandable sheath. Background Technology

[0002] With the continuous development of science, the increasing improvement of medical devices and operating techniques, and the deeper research into related medical mechanisms, transcatheter ablation is being increasingly applied in clinical practice. Examples include transcatheter aortic valve, pulmonary valve, mitral valve, and tricuspid valve repair and replacement, as well as transcatheter cardiac ablation. This method of performing surgery through a catheter into human tissue offers numerous advantages, including short operation time, minimal patient trauma, and rapid recovery. Transcatheter ablation provides a new and superior solution for patient treatment.

[0003] This method of surgery, which involves inserting a catheter into human tissue, requires a delivery sheath to create a channel before the catheter enters the body. During the insertion of the delivery sheath, a dilator is used to provide radial support. The dilator typically has a tapered tip at its distal end to facilitate the insertion of the delivery sheath.

[0004] Introducing sheaths typically have a long sheath that is inserted into the vascular system. Traditional introducing sheaths have a fixed inner and outer diameter, which causes severe dilation of the blood vessels upon entry, resulting in significant damage to the vessels.

[0005] A Chinese patent, "Expandable Sheath for Guiding Intravascular Delivery Devices into the Body" (Publication No.: CN114375212A), provides an expandable sheath. However, this expandable sheath employs a split structural design, specifically, the sheath tube and the soft distal portion (the constricted end of the tube) are designed separately. While this structure allows for the use of a soft distal portion of the sheath, facilitating its passage through blood vessels, when delivering devices such as bulbar valves, the soft distal portion, being the most distal end of the sheath, requires not only radial support for the device but also... In addition to compressive force, sufficient axial force must be maintained to prevent the soft distal portion from detaching from the distal end of the sheath due to friction between the instrument and the soft distal portion as the instrument passes through it. Since the soft distal portion and the sheath are made of different materials, the soft distal portion is very easy to separate from the sheath in actual use. In order to ensure a reliable connection between the soft distal portion and the sheath, a more complex structure and / or process is required. It should also be noted that since this type of medical device needs to enter the human body, the consequences of the soft distal portion detaching from the distal end of the sheath inside the human body are extremely serious.

[0006] Therefore, a new technology is urgently needed to solve the above problems, reduce the damage of the sheath to human blood vessels, and form a safe delivery system that accurately delivers blood and prevents blood from flowing out of the human body or air from flowing into the human body. Summary of the Invention

[0007] This invention addresses the technical problem that the soft distal portion of existing sheaths is prone to detachment and damage to blood vessels. One aspect of this invention provides a method for manufacturing an expandable sheath, comprising the steps of:

[0008] S1. An inner tube with an inner diameter larger than the outer diameter of a core tube is fitted over the core tube. The inner tube is tightly attached to the outer wall of the core tube to form an inner tube body. The portion of the inner tube that extends beyond the inner tube body is folded to form a folded body. The folded body is attached to the side wall of the inner tube body to form a slit.

[0009] S2. A middle layer tube with an inner diameter smaller than the outer diameter of the liner tube is cut axially to form a middle tube groove. A constriction and tearing opening is radially cut on the side of one groove of the middle layer tube near the distal end. The middle layer tube covers the outer wall of the inner tube body. The side of the middle layer tube with the constriction and tearing opening is inserted into the slit of the inner tube. The other side of the middle layer tube is attached to the other side of the inner tube body. After aligning the distal end of the constriction and tearing opening with the distal end of the slit, the distal end of the middle layer tube protrudes beyond the distal ends of the inner tube and the outer tube, thereby forming a constricted end of the middle tube.

[0010] S3. An outer tube with an inner diameter larger than the outer diameter of the core tube is axially cut to form an outer tube groove. A first thinning outer tube opening is cut at the distal end of one groove side of the outer tube. Alternatively, a first thinning outer tube opening is first cut at the distal end of an outer tube, and then the outer tube is axially cut with one axial side of the first thinning outer tube opening as the axial direction to form an outer tube groove. The outer tube covers the outer wall of the middle tube. The outer tube with one groove side of the first thinning outer tube opening is inserted into the slit of the inner tube and located between the middle tube and the folded body. The other groove side of the outer tube fits and covers the outer wall of the folded body. The distal ends of the outer tube and the distal ends of the inner tube are aligned with the proximal end of the constricted end of the middle tube.

[0011] S4. A first heat-shrink tubing is fitted over the outer tube to form a first tubing.

[0012] S5. The first tube is heated at a high temperature, and then cooled to remove the liner tube and the first heat shrink tube, to obtain a semi-finished expandable sheath tube.

[0013] Preferably, the method for manufacturing an expandable sheath further includes the step of:

[0014] S6. Insert a certain core tube into the semi-finished expandable sheath obtained in step S5, wherein the outer diameter of the main body of the core tube is equal to the inner diameter of the semi-finished expandable sheath, the outer diameter of the distal section of the core tube gradually decreases towards the distal end, and the outer diameter of the proximal section of the core tube gradually increases towards the proximal end.

[0015] S7. A certain type of heat shrink tubing is then fitted over the expandable sheath obtained in step S6 to form a second tubing.

[0016] S8. The second tubing is heated at a high temperature, and then cooled to remove the shaped core tube and the shaped heat shrink tube, to obtain the final product, the expandable sheath tube.

[0017] Preferably, one groove side of the middle layer tube in step S2 and / or one groove side of the outer layer tube in step S3 are inserted into the bottom of the slot of the inner layer tube.

[0018] Preferably, in step S3, the size of the first thinning outer tube opening cut from the outer tube is smaller than the size of the constriction and tear opening cut from the middle tube, and the first thinning outer tube opening and the constriction and tear opening are aligned radially.

[0019] Preferably, in step S6, the shaping core tube includes, from the proximal end to the distal end, a flared conical section with an outer diameter that gradually increases from the distal end to the proximal end, a main body section with a constant outer diameter, and a constricted conical section with an outer diameter that gradually decreases from the proximal end to the distal end, wherein the proximal section of the constricted conical section has a marking section.

[0020] Preferably, in step S6, the constricted end of the middle tube is placed in the constricted tapered section of the shaped core tube.

[0021] Preferably, in step S2, a force-reducing notch is further cut at the distal end of the contraction and tear opening near the bottom of the gap, and the force-reducing notch is integrally connected with the contraction and tear opening.

[0022] Preferably, in step S2, the shape of the contraction and tear is rectangular.

[0023] Preferably, in step S6, the constricted end of the distal tube of the semi-finished expandable sheath is placed on the marked section of the shaped core tube.

[0024] Preferably, in step S3, after axially cutting to form the outer tube groove, a second thinning outer tube opening is cut at the distal end of the other groove side of the outer tube; or, a first thinning outer tube opening and a second thinning outer tube opening are first cut at the distal end of the groove side of the outer tube, the axial side of the first thinning outer tube opening and the axial side of the second thinning outer tube opening are interconnected and share an axial connecting line, and then the outer tube is axially cut along the axial connecting line to form the outer tube groove.

[0025] Preferably, the first thinning outer tube opening and the second thinning outer tube opening have the same size.

[0026] Preferably, in step S6, the proximal end of the semi-finished expandable sheath is placed in the flared conical section of the shaped core tube.

[0027] Preferably, in step S5, the heating temperature range is 280℃-300℃ and the heating time is 5-8 minutes; in step S8, the heating temperature range is 280℃-300℃ and the heating time is 4-6 minutes.

[0028] Preferably, in step S1, the inner diameter of the inner tube before folding is 1.4-1.8 times the outer diameter of the core tube, more preferably 1.5-1.7 times, and more preferably 1.6 times; in step S2, the inner diameter of the middle tube before cutting the middle tube groove is 0.8-0.95 times the outer diameter of the core tube, more preferably 0.9 times; in step S3, the inner diameter of the outer tube before cutting the outer tube groove is 1.1-1.3 times the outer diameter of the core tube, more preferably 1.2 times.

[0029] Preferably, before step S1, the proximal and distal ends of the inner tube are sealed, and then the outer surface of the inner tube is etched.

[0030] Preferably, before step S2, an open developing ring is fitted over the inner tube body, one end of the developing ring is inserted into the bottom of the slit, and the other end of the developing ring is attached to the other side of the inner tube body; in step S2, the position of the developing ring is adjusted so that the distal end of the developing ring is aligned with the proximal end of the constricted tear.

[0031] Preferably, in step S7, a layer of the same material as the outer tube is first wrapped around the proximal section of the semi-finished expandable sheath, and then the shaping heat shrink tubing is fitted on.

[0032] The positive and progressive effects of this invention are as follows:

[0033] 1) This invention improves the safety of the expandable sheath by setting an integrated constricted end of the central tube at the far end of the central tube body, thereby preventing the constricted end of the central tube from falling off at the far end. Compared with the split constricted end, it reduces the processing difficulty.

[0034] 2) By setting a certain length-to-diameter ratio at the constricted end of the middle tube, the present invention effectively forms a relatively flexible distal end of the sheath, while also having sufficient retaining force to ensure that the constricted end of the middle tube is tightly attached to the expander.

[0035] 3) This invention creates a contraction and tearing opening at the bottom of the seam of the inner tube, in the distal section of the middle tube. This opening forms a buffer space that can accommodate the material of the middle tube squeezed during sheath manufacturing. The material of the middle tube will not overflow to the contraction end of the middle tube at the distal end of the expandable sheath, thus preventing the contraction end from thickening. When the delivery device passes through, only a small radial support force is needed to break the contraction and tearing area at the contraction end of the middle tube, allowing the delivery device to pass smoothly through the distal end of the expandable sheath.

[0036] 4) By setting a first thinning outer tube opening at the distal end of the outer tube, the distal end of the outer tube forms a non-overlapping circle, which matches the constricted end of the middle tube to form a uniform and consistent distal end of the expandable sheath, making its performance uniform and preventing uneven mechanical properties caused by different structures at the distal end of the expandable sheath, effectively preventing phenomena such as edge warping at the distal end of the expandable sheath.

[0037] 5) The present invention provides a narrowing tear opening at the far end of the middle tube and a first thinning outer tube opening at the far end of the outer tube, with the two positions corresponding to each other. When the folded body of the expandable sheath expands, it is very easy to tear apart, so it will not affect or hinder the expansion of the folded body.

[0038] 6) The present invention uses a constriction and tear opening with a size larger than the size of the first thinning tube opening, so that the outer tube body around the first thinning tube opening can isolate the inner tube body and the folded body at the radial direction of the constriction and tear opening to avoid adhesion.

[0039] 7) The present invention uses the overlapping area and the additional covering area of ​​the outer tube of the expandable sheath to cover the outer wall of the folded body. When the folded body expands, the overlapping area and the additional covering area of ​​the outer tube help the expanded folded body maintain its curvature, and when the diameter of the expandable sheath shrinks, the folded body returns to its folded state.

[0040] 8) The operating handle provided by the present invention, through the design of a planar sealing valve, a centering sealing valve, a support ring, and a proximal end cover, securely presses the valve edge of the planar sealing valve, the support ring, and the proximal edge of the centering sealing valve between the inner wall of the middle section of the handle housing and the proximal end cover by means of the inner ring of the cover.

[0041] 9) The constricted end of the expandable sheath produced by the method of the present invention is integrally formed with the main body, which simplifies the manufacturing method. Attached Figure Description

[0042] Figures 1A-1D This is a schematic diagram of the three-dimensional structure of the expandable sheath of the present invention;

[0043] Figures 2A-2B This is a three-dimensional structural diagram of the inner tube of the expandable sheath of the present invention;

[0044] Figure 3A This is a schematic diagram of the three-dimensional structure of the middle layer tube of the expandable sheath before heat setting according to the present invention;

[0045] Figure 3B This is a diagram showing the middle layer of the expandable sheath of the present invention.

[0046] Figures 3C-3D This is a three-dimensional structural diagram of the middle layer tube of the expandable sheath of the present invention before heat setting;

[0047] Figures 3E-3F This is a schematic diagram of the three-dimensional heat-set structure of the middle layer tube of the expandable sheath of the present invention;

[0048] Figures 4A-4B A schematic diagram showing the positional relationship between the middle layer tube and the imaging ring of the expandable sheath of the present invention;

[0049] Figure 4C A schematic diagram of the three-dimensional structure of the imaging ring of the expandable sheath of the present invention;

[0050] Figure 5A This is a three-dimensional structural diagram of the outer tube of the expandable sheath before heat setting according to the present invention;

[0051] Figure 5B This is a diagram showing the outer tube of the expandable sheath of the present invention.

[0052] Figures 5C-5D This is a three-dimensional structural diagram of the outer tube of the expandable sheath of the present invention before heat setting;

[0053] Figure 5E This is a development diagram of another embodiment of the outer tube of the expandable sheath of the present invention;

[0054] Figure 5F This is a schematic diagram of the three-dimensional structure of the outer tube of the expandable sheath of the present invention after heat setting, according to another embodiment.

[0055] Figure 6 This is a schematic cross-sectional view of the expandable sheath of the present invention before expansion;

[0056] Figure 7A This is a schematic diagram of the structure of the expandable sheath of the present invention after adding an elastic layer;

[0057] Figure 7B A schematic cross-sectional view of the expandable sheath of the present invention after adding an elastic layer;

[0058] Figure 8A This is a schematic diagram of the expanded sheath structure of the present invention after expansion;

[0059] Figure 8B This is a schematic diagram of the expanded outer tube structure of the expandable sheath of the present invention after expansion;

[0060] Figure 8C This is a schematic diagram of the expanded middle layer of the expandable sheath of the present invention after expansion;

[0061] Figure 8D This is a schematic diagram of the cross-section of the expandable sheath of the present invention after expansion;

[0062] Figure 9 This is a schematic diagram of the shaped core tube of the present invention. Detailed Implementation

[0063] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0064] It should be noted that the terms "distal," "proximal," "distal segment," and "proximal segment" used in this invention are directional terms commonly used in the field of interventional medical devices. "Distal" refers to the end furthest from the operator during surgery, "proximal" refers to the end closest to the operator during surgery, "distal segment" refers to a segment furthest from the operator and close to the distal end during surgery, and "proximal segment" refers to a segment close to the operator and close to the proximal end during surgery. "Axial" refers to the direction of the line connecting the distal center and the proximal center; "radial" refers to the direction perpendicular to the aforementioned axial direction.

[0065] In this application, the main parts of the "expandable sheath" are the "expandable sheath tube" and the "operating handle" that cooperates with the "expandable sheath tube". Therefore, when directly describing the "expandable sheath", it is undoubtedly confirmed from the context that the part to be introduced is the expandable sheath tube. Directly describing the expandable sheath only refers to its "expandable sheath tube" part.

[0066] like Figures 1A to 1D as well as Figure 6 As shown, the expandable sheath of the present invention comprises, from the inside out, an inner tube 10, a middle tube 20, and an outer tube 30.

[0067] like Figures 2A-2BAs shown, in this example, the inner tube 10 is a long, generally circular tube structure with a thickness of approximately 0.10 mm, or approximately 0.05 mm to 0.2 mm. Specifically, the thickness of the inner tube 10 can be 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, or 0.19 mm.

[0068] In terms of material, the inner tube 10 can be made of PTFE (polytetrafluoroethylene). PTFE has high lubricity and the lowest coefficient of friction among solid materials, only 1 / 5 that of polyethylene. Therefore, the inner tube 10 should preferably have a low coefficient of friction, such as about 0.01 to 0.5, to facilitate the movement of the delivery device into the expandable sheath. Here, the expandable sheath desires an even lower coefficient of friction for the inner tube 10, as a lower coefficient of friction is more conducive to reducing the frictional force when the delivery device enters; that is, the inner tube 10 can have a coefficient of friction less than 0.01. PTFE material does not adhere to any substances and has the lowest surface tension among solid materials. PTFE inner tubes, when used as artificial blood vessels and organs, have no adverse reactions when implanted in the body for a long time.

[0069] Structurally, the inner tube 10 includes an inner tube body 11 and a folded body 12. The inner tube body 11 and the folded body 12 each have two axial sides. One side edge of the inner tube body 11 and one side edge of the folded body 12, and the other side edge of the inner tube body 11 and the other side edge of the folded body 12 are integrally formed. The folded body 12 is attached to the side wall of the inner tube body 11 and forms a slit 13. The folded body 12 is a multi-layered strip structure. In some embodiments, the folded body 12 has 2N layers (N is a positive integer). Each layer has a first side edge and a second side edge. The first side edge of the first layer is connected to one side edge of the inner tube body 11, the second side edge of the i-th layer is connected to the first side edge of the (i+1)-th layer, and the second side edge of the 2N-th layer is connected to the other side edge of the inner tube body 11, where 1≤i≤2N-1, and i is a positive integer. In a further preferred example, N is 3, meaning the folded body 12 has a three-layer structure. In an even more preferred example, N is 2, meaning the folded body 12 has a two-layer structure.

[0070] The inner tube body 11 can be regarded as a long, curved, coiled sheet with a radial cross-section of arc. The angle before expansion can be any angle, preferably 360° (i.e., the two sides of the inner tube body 11 contact each other to form an openable cylinder), or 359°, or 358°. These angles can achieve the purpose of the present invention. The angle of the inner tube body 11 after expansion can also be any angle, preferably 170° to 300°, more preferably 180° to 260°, more preferably 190° to 220°, etc. The present invention does not impose any particular limitation on the angle. As the name suggests, the folded body 12 is a multi-layered, long, curved sheet with overlapping layers. It also has a certain curvature when viewed in radial section. The folded body 12 can also have any angle of curvature before expansion. The preferred angle is 40° to 140°, more preferably 60° to 120°, and even more preferably 90° to 100°. This invention does not impose any particular limitation on the angle, because the actual size of the inner tube is closely related to the design size of the expandable sheath. The specific angle adjustment can be obtained by those skilled in the art based on actual needs without creative effort. Therefore, the angle range in the above description should be understood to include, but is not limited to, the above angles. For example, the angle of the folded body 12 can also be 170°. Considering that the folded body 12 needs to be opened inside the blood vessel, in principle, the angular radius of the folded body 12 should not exceed 180°, that is, the folded body 12 should cover no more than 1 / 2 of the inner tube body 11. Otherwise, it will be relatively difficult to open the folded body 12 because the expandable sheath is wrapped around the blood vessel. Therefore, the folded body 12 does not move freely during the opening process (i.e., the folded body 12 is turned outward relative to the inner tube body 11). However, under special requirements, the angular radius of the folded body 12 can be greater than 180°, for example, when the diameter difference between the expandable sheath before and after expansion is large. But no matter how the angles of the inner tube body 11 and the folded body 12 are set, the total angle after the inner tube body 11 and the folded body 12 are fully expanded should be 360° (i.e., forming a cylinder).

[0071] A folding body 12 is provided in the inner tube 10 of the expandable sheath, giving the expandable sheath a small outer diameter and the ability to expand. For example... Figures 8A-8DAs shown, when the delivery device enters the expandable sheath, because the outer dimensions of the delivery device are larger than the inner diameter of the unexpanded expandable sheath, the folded body 12 of the expandable sheath expands under the expansion of the delivery device, forming a larger inner diameter with the inner tube body 11, thus providing a passage for the delivery device. The expandable sheath can be fully expanded to allow the delivery device to pass through. After the expandable sheath temporarily expands and the delivery device passes through, the expandable sheath subsequently loses the expansion force exerted on it by the delivery device. Therefore, the expandable sheath can quickly retract to a certain outer diameter, no longer generating a large expansion force on the blood vessel, thus minimizing the damage to the blood vessel and the human body caused by the expansionable sheath's outer diameter remaining excessively large for an extended period.

[0072] like Figures 3A-3F As shown, in this example, the middle layer tube 20 is a long sheet-like structure that is generally curled and bent at an angle of approximately 340° to 358°, with a thickness of approximately 0.15 mm, or approximately 0.05 mm to 0.2 mm. Specifically, the thickness of the middle layer tube 20 can be 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.10 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.16 mm, 0.17 mm, 0.18 mm, or 0.19 mm.

[0073] In terms of materials, the middle layer tube 20, serving as the intermediate layer between the inner layer tube 10 and the outer layer tube 30, effectively bonds the inner layer tube 10 and the outer layer tube 30 together. The middle layer tube 20 is made of LDPE (low-density polyethylene). Because HDPE has fewer molecular chains and LDPE has more molecular chains, after heating to the melting temperature, LDPE has more active molecular chains than HDPE. Therefore, the middle layer tube 20 can bond with the PTFE inner layer tube 10 (which has undergone surface etching treatment). Similarly, since both LDPE and HDPE are polyethylene, they will naturally bond together after melting. If the outer layer tube 30 is connected to the inner layer tube 10, due to the fewer molecular chains of HDPE, even after melting, HDPE remains relatively stable, making it difficult to bond with PTFE.

[0074] Structurally, the middle tube 20, being a long, coiled, sheet-like structure, is tubular and has a central tube groove 23 cut along the axial direction. The middle tube 20 is fitted onto the outer wall of the inner tube body 11. One side of the groove of the middle tube 20 is located in the slot 13 of the inner tube 10 and abuts against the bottom of the slot 13. The other side of the groove of the middle tube 20 is close to the other side edge of the inner tube body 11. It should be noted that "close to" can mean that the two are completely in the same position or that they are close in distance. The middle tube 20 has a middle tube body 20a and a constricted end 21 extending integrally from the distal end of the middle tube body 20. The constricted end 21 of the middle tube protrudes from the far end of the inner tube 10 and the outer tube 30. The middle tube body 20a is sleeved on the outer wall of the inner tube body 11. The constricted end 21 of the middle tube corresponds to the far end of the gap 13 of the inner tube 10 as the constricted tearing area 24. The far end of the middle tube body 20a (i.e. the near end of the constricted end 21 of the middle tube) is provided with a constricted tearing opening 22 that is coaxial with the constricted tearing area 24 and located in the gap 13 of the inner tube 10. That is, the near end of the constricted tearing area 24 and the far end of the constricted tearing opening are on the same edge line.

[0075] The distal ends of the inner tube body 11 and the folded body 12 are flush with the proximal end of the constricted end 21 of the middle tube. The constricted end 21 of the middle tube is a complete circular structure. Although in the unfolded view of the middle tube layer 20 (as shown in the figure) Figure 3B In the process, the constricted end 21 of the middle tube and the proximal end of the middle tube body 20a are separated by the middle tube groove 23. However, the final form of the constricted end 21 of the middle tube is a complete and seamless circular structure (this feature will be further reflected in the subsequent processing steps, but the way to obtain this structural feature is not limited to this process step, because the description of this embodiment focuses on the structural part, so it cannot be claimed that it does not fall within the protection scope of this application because the structural feature is obtained by using different processing methods). The diameter (including the inner diameter and the outer diameter) of the constricted end 21 of the middle tube gradually decreases towards the distal end to form a constriction.

[0076] The constricted end 21 of the tubing is preferably a hollow frustum with a smaller distal end and a larger proximal end. Here, "hollow frustum" refers not only to its conical outer diameter but also to its hollow interior, which also has a conical structure with a smaller distal end and a larger proximal end. The smaller distal end and larger proximal end of the outer diameter allows the sheath to pass through blood vessels more effectively, while the smaller distal end and larger proximal end of the internal conical structure ensures a tighter fit between the constricted end 21 and the dilator, preventing blood from flowing into the dilator sheath through the gap between the dilator and the distal end of the sheath. It should also be noted that the frustum here does not simply refer to a frustum with straight sides; its sides can be smooth arcs or other structures. Therefore, the frustum in this embodiment should be understood as a structure whose cross-sectional diameter gradually decreases from the proximal end to the distal end.

[0077] Because the constricted end 21 of the tubing has a gradually decreasing diameter, it can fit tightly against the dilator during insertion, allowing the expandable sheath to smoothly enter the blood vessel. The taper of the constricted end 21 needs to match the taper of the distal end of the dilator for successful insertion. The choice of the dilator's taper is determined by those skilled in the art without creative effort, based on practical factors such as the diameter of the expandable sheath and the required implantation location. Therefore, the specific taper range of the constricted end 21 is not limited here. However, to ensure better fit of the constricted end 21 against the distal end of the dilator, preferably, the taper of the constricted end 21 is not less than the taper of the distal end of the dilator; more preferably, the taper of the constricted end 21 is greater than the taper of the distal end of the dilator, ensuring better fit and allowing the expandable sheath and dilator to enter the blood vessel more effectively.

[0078] When the expandable sheath is withdrawn from the expander and the delivery device is inserted, the constricted end 21 of the central tube, due to its fixed diameter, will inevitably generate (resistance) to hinder the passage of the delivery device. Therefore, the constricted end 21 of the central tube needs to be broken in order to cooperate with the expansion of the expandable sheath. During the breaking process, the constricted end 21 of the central tube is subjected to forces in two main directions: one is an axial force that pushes from the proximal end to the distal end, and the other is a radial force that expands outwards.

[0079] Here, the axial force will push the constricted end 21 of the middle tube towards the distal end of the expandable sheath, that is, push the constricted end 21 of the middle tube 21 to detach from the distal end of the expandable sheath. However, since the constricted end 21 of the middle tube 20 is an integral structure with the middle tube 20, the constricted end 21 of the middle tube 21 can withstand a large tearing force without detaching, because the constricted end 21 of the middle tube 20 is not only integrated with the middle tube 20, but also the connection area (length) between the constricted end 21 of the middle tube 21 and the middle tube 20 is large enough. Compared with the traditional split constricted end of the middle tube, the integrated constricted end 21 of the middle tube 21 greatly improves the safety of the expandable sheath. Moreover, compared with the traditional split constricted end of the middle tube 21, it does not require assembly of the constricted end 21 of the middle tube 21, which greatly reduces the assembly and processing difficulty of the expandable sheath.

[0080] Here, the radial force will cause the constricted end 21 of the middle tube to break. Since the expandable sheath expands first at the connection between the folded body 12 and the inner tube body 11, the constricted end 21 of the middle tube will also break at this location. Therefore, it is desirable that the constricted end 21 of the middle tube at this location is easier to tear than the constricted end 21 of the middle tube at other locations. Therefore, in the preferred example, a tear-resistant opening 22 for the constricted end 21 of the middle tube is provided at the distal end of the middle tube 20. That is, the constricted tear-resistant opening 22 is provided on the proximal side of the constricted end 21 of the middle tube, and the tube body part on the distal side of the constricted tear-resistant opening 22 is the constricted end 21 of the middle tube. The constricted tear-resistant opening 22 of the middle tube 20 is sandwiched in the gap 13 of the inner tube 10, and the proximal end of the constricted tear-resistant area 24 (i.e., the distal end of the constricted tear-resistant opening 22) is flush with the distal end of the gap 13.

[0081] Here, the axial length of the constricted end 21 of the tube is 0.5mm-4.0mm, preferably 1.0mm-2.0mm, and the length of the constricted end 21 can be 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3.1mm, 3.2mm, 3.3mm, 3.4mm, 3.5mm, 3.6mm, 3.7mm, 3.8mm, or 3.9mm. Because an excessively short constricted end 21 of the mid-tube will not effectively form a relatively flexible distal sheath, thus failing to protect the blood vessel from scratches by the distal sheath. While an excessively long constricted end 21 increases the contact area between the mid-tube constricted end 21 and the distal end of the dilator, it can also cause the flexible mid-tube constricted end 21 to evert during delivery of the dilator sheath into the body due to insufficient adhesion and retention force. Furthermore, an excessively long mid-tube constricted end 21 is also detrimental to its rupture and dilation, which could prevent the delivery device from passing through the distal end of the dilator sheath. Therefore, a preferred length-to-diameter ratio of the mid-tube constricted end 21 is 1:1.2 to 1:6, more preferably 1:1.4 to 1:5, even more preferably 1:2 to 1:4, and even more preferably 1:3 to 1:3.5. At this point, the constricted end 21 of the central tube forms a relatively narrow constriction tearing zone 24 for its fracture expansion to allow the delivery device to pass through.

[0082] Here, the location of the constriction and tear opening 22 needs to be determined by comprehensively considering the relationship between the inner tube 10, the middle tube 20, and the outer tube 30. Ideally, the constriction and tear opening 22 should be located on the side of the middle tube groove 23 and connected to it. The distal edge of the constriction and tear opening 22 is flush with the proximal edge of the constriction end 21 of the middle tube, and the distal edge of the constriction and tear opening 22 is also flush with the distal edge of the inner tube 10. The shape of the opening of the constriction and tear opening 22 is not limited, but a rectangular opening is preferred.

[0083] When the constricted tear 22 mates with the inner tube 10, it needs to be installed within the slot 13 of the inner tube 10. The three layers of the expandable sheath need to be tightly joined and compressed, thus further compressing the space within the slot 13. Since the space at the bottom of the slot 13 is limited, the slot 13 located at the distal end of the middle tube 20 and the proximal end of the constricted end 21 (the connection point between the middle tube body 20a and the constricted end 21) will be analyzed and described here. Similarly, the connection point between the middle tube body 20a and the constricted end 21 also corresponds to the distal end of the inner tube 10. Therefore, during the heating, extrusion, and shaping process of the expandable sheath, the slot 13 of the inner tube 10 is also being extruded and deformed, resulting in a further reduction in the space within the slot 13. Without the constriction and tear opening 22, the middle tube 20 would experience a large amount of material extruded from its distal end to the constriction end 21, causing it to thicken. This is because the distal end of the bottom of the slit 13 is close to the rupture point (or considered to be the same point) of the constriction and tear opening 24, making it difficult for the constriction and tear opening 24 to rupture. The constriction and tear opening 22 creates a buffer space to accommodate the extruded material from the middle tube 20, preventing it from overflowing into the constriction and tear opening 24 at the distal end of the expandable sheath. This prevents the constriction end 21 from thickening, facilitating the passage of the delivery device. Only a small radial support force is needed to rupture the constriction and tear opening 24 at the distal end of the expandable sheath, allowing the delivery device to pass through.

[0084] For example, when the intrathecal delivery device is a balloon-expandable stent, the distal end of the delivered material has a lotus-shaped tip, which is significantly larger than the diameter of the delivery catheter. The distal surface of the lotus-shaped tip is relatively flat. Due to the design of the constriction tear 22, the lotus-shaped tip can easily break through the constriction end 21 of the central tube. This prevents the delivered material from getting stuck at the constriction at the distal end of the expandable sheath due to the difficulty in breaking the constriction end 21. The setting of the constriction tear 22 will not affect the constriction structure of the constriction end 21 of the expandable sheath. Since the constriction end of the middle tube is located on the distal side of the constriction tear 22, the constriction end 21 of the middle tube is still a relatively complete circular structure, which can ensure that the distal end of the expandable sheath forms a relatively flat distal end surface. Moreover, the constriction end 21 of the middle tube (constriction structure) is integrated with the middle tube 20. Utilizing the soft characteristics of the material of the middle tube 20, namely LDPE material, it directly replaces the traditional split soft terminal part. This not only realizes the formation of a soft distal end of the expandable sheath, but also prevents the constriction end 21 of the middle tube (constriction structure) from falling off.

[0085] like Figures 3C-3F As shown, in some embodiments, in order to further reduce the force required for the narrowing tear zone 24 to break, a corner near the bottom of the gap 13 at the proximal end of the narrowing tear zone 24 is a tear initiation angle. The tear initiation angle also has a force-reducing notch 25 that is easy to tear. The force-reducing notch 25 is integrally connected with the narrowing tear opening. The shape of the force-reducing notch 25 is not limited. It can be triangular, rectangular, semi-circular, semi-elliptical, etc. In this way, when forming a complete narrowing structure of the middle tube narrowing end 21, the material is relatively thinner at the place where the force-reducing notch is set, or a corresponding residual notch is formed near the position where the middle tube narrowing end 21 needs to break. This facilitates the fracture expansion of the middle tube narrowing end 21 under the action of the delivery device, so as to realize the passage of the delivery device.

[0086] like Figures 4A-4C As shown, in order to confirm the position of the distal end of the sheath, a radiopaque ring 50 is provided at the distal end of the sheath. The radiopaque ring 50 is made of radiopaque metal and is annular with an opening 51, so that the radiopaque ring 50 can expand with the sheath. One end of the opening 51 of the radiopaque ring 50 is located in the slot 13 of the inner tube 10, and the other end of the opening 51 of the radiopaque ring 50 is located on the other axial side edge of the inner tube body 11.

[0087] To prevent the developing ring 50 from creating excessive resistance to the expansion of the sheath, the thickness of the developing ring 50 is selected to be 0.03 mm to 0.15 mm, preferably 0.04 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.90 mm, 0.10 mm, 0.11 mm, 0.12 mm, 0.13 mm, or 0.14 mm.

[0088] In this embodiment, the developing ring 50 is disposed between the inner layer tube 10 and the middle layer tube 20. Since the inner layer tube 10 is made of PTFE, the middle layer tube 20 is made of LDPE, and the outer layer tube 30 is made of HDPE, the soft point (melting point) temperature of PTFE is higher than that of HDPE. Therefore, the developing ring 50 located between the middle layer tube 20 and the inner layer tube 10 will be more stable during the heat setting of the sheath. If the imaging ring 50 is placed between the middle layer tube 20 and the outer layer tube 30, the material of the outer layer tube 30 may soften or even melt during heat setting, which may cause the imaging ring 50 to puncture the outer layer tube 30 and become exposed. This is because an exposed imaging ring 50 will scratch the inner wall of the blood vessel or even puncture the blood vessel. However, it should be stated that this application does not object to placing the imaging ring 50 between the middle layer tube 20 and the outer layer tube 30. By controlling the temperature and time of heat setting, the imaging ring 50 can be placed between the middle layer tube 20 and the outer layer tube 30. However, in this application, due to the difference in materials between the inner layer tube 10 and the outer layer tube 30, placing the imaging ring 50 between the inner layer tube 10 and the middle layer tube 20 makes it easier to obtain a higher product yield in production.

[0089] To further ensure the developing function of the developing ring 50, such as Figures 4A-4B As shown, the developing ring 50 used in this application is more like a complete circular ring, with a diameter equal to the outer diameter of the inner tube 10 in the compressed state. It is only provided with an opening 51 to correspond to the groove 23 of the middle tube 20, so that the developing ring 50 can expand with the expansion of the middle tube 20. Since the middle tube 20 is provided with a constriction and tearing opening 22, in order to prevent the developing ring 50 from directly contacting the outer tube 30, while ensuring that the developing ring 50 can be close enough to the far end of the sheath, the far end of the developing ring 50 is flush with the proximal end of the constriction and tearing opening 22. This ensures that the developing ring 50 cannot directly contact the outer tube 30, while ensuring that the developing ring 50 can be close enough to the far end of the sheath.

[0090] like Figures 5A-5FAs shown, in this example, the outer tube 30 is also a long, sheet-like structure that is generally bent and rolled into an angle of approximately 360° to 370°, with a thickness of approximately 0.25 mm, or approximately 0.15 mm to 0.35 mm. Specifically, the thickness of the outer tube 30 can be 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.20 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0.30 mm, 0.31 mm, 0.32 mm, 0.33 mm, or 0.34 mm.

[0091] In terms of material, the outer tube 30 can be made of HDPE (high-density polyethylene). HDPE has high rigidity and toughness, good mechanical strength, and good resistance to environmental stress cracking. Its hardness, tensile strength, and creep resistance are superior to LDPE (low-density polyethylene). Therefore, the outer tube 30 can provide support for the entire expandable sheath, thus ensuring that the expandable sheath can conform to the blood vessel and prevent crushing. Moreover, it has good chemical stability, is insoluble in any organic solvent at room temperature, and is resistant to corrosion from acids, alkalis, and various salts.

[0092] Structurally, the outer tube 30 is also a long, coiled, sheet-like structure. As a tube, the outer tube 30 has an outer tube body 30a. The outer tube body 30a has an outer tube groove 32 cut along the axial direction. The diameter of the outer tube 30 is larger than that of the inner tube 10. The outer tube body 30a of the outer tube 30 is sleeved on the outer wall of the middle tube body 20a of the middle tube 20. One side of the groove of the outer tube 30 is located at the bottom of the slit 13 of the inner tube 10 and is located between the middle tube 20 and the folded body 12. The other side of the groove of the outer tube 30 covers the outer wall of the folded body 12.

[0093] The outer tube 30 has an outer tube extension and contraction head 30b integrally extending from the distal end of the outer tube body 30a. The proximal end of the middle tube contraction end 21 is located on the inner wall of the outer tube extension and contraction head 30b, and the distal end of the outer tube extension and contraction head 30b is located on the outer wall of the middle tube contraction end 21. Thus, the distal end of the outer tube extension and contraction head 30b extends beyond the distal end of the contraction tear opening 22 and partially wraps around and fixes the contraction tear opening 24 in the axial direction. The outer diameter of the outer tube extension and contraction head 30b gradually decreases from the proximal end to the distal end, while the inner diameter remains nearly uniform from the proximal end to the distal end (though there is a very slight decrease), meaning its wall thickness gradually decreases, or it is referred to as a necking process. The distal end of the outer tube 30 extends forward to form the outer tube extension and contraction head 30b (this feature will be further demonstrated in subsequent processing steps, but the method of obtaining this structural feature is not limited to this specific process step, as this embodiment focuses on the structural part; therefore, the use of different processing methods to obtain this structural feature cannot be used as grounds for claiming it does not fall within the scope of this application). Therefore, the proximal end of the middle tube necking end 21 of the middle tube 20 will no longer be flush with the distal end of the outer tube 30. Instead, the outer tube extension and contraction head 30b of the outer tube 30 partially overlaps with the middle tube necking end 21, thereby wrapping and fixing the necking tear area 24 of the middle tube necking end 21 to prevent it from falling off.

[0094] Since the expansion portion of the expandable sheath is the folded body 12 of the inner tube 10, or rather, the connection between the folded body 12 and the inner tube body 11, the contraction tearing area 24 of the constricted end 21 of the middle tube is obviously also located at this position. Because the contraction tearing area 24 of the constricted end 21 of the middle tube is a weak position in terms of tensile (tear) force relative to the distal end of the middle tube 20, it is necessary to break it in the contraction tearing area 24 to achieve the expansion of the distal end of the expandable sheath.

[0095] Therefore, in this embodiment, the narrowing and tearing area 24 is obviously located at the seam 13 formed by the folded body 12 and the inner tube body 11. The fracture location of the narrowing and tearing area 24 is also the connection location between the folded body 12 and the inner tube body 11. However, since the outer tube 30 is double-layered in this part, or in other words, the outer tube 30 in this part is in an overlapping section, when the outer tube 30 is narrowed to form the outer tube extension head 30b, the material of the outer tube 30 in this part is twice the volume of the material in other single-layer positions because the outer tube 30 is double-layered. Therefore, during the thermoforming process, more material will extend to the distal end of the outer tube 30 as it is extruded and thinned, resulting in a larger area of ​​adhesion between the outer tube 30 and the narrowed end 21 of the middle tube. This leads to an increase in the tensile (tear) resistance of the narrowed end 21 of the middle tube in this part, making it difficult for the expandable sheath to expand. That is, the place where the narrowed end 21 of the middle tube needs to break is difficult to break, thereby preventing the expansion of the expandable sheath. Therefore, a first thinning outer tube opening 31 is provided at the far end of one groove side of the outer tube body 30a to prevent the outer tube 30 from overlapping. The first thinning outer tube opening 31 is integrally connected with the outer tube groove 32. The groove side of the outer tube body 30a with the first thinning outer tube opening 31 is set in the gap 13 of the inner tube 10 and located between the middle tube body 20a and the folded body 12. The other groove side of the outer tube body 13 covers the outer wall of the folded body 13.

[0096] Here, a first thinning outer tube opening 31 is provided at the portion of the outer tube 30 near the distal end of the slit 13. Because the distal end of the outer tube 30 abuts against the bottom of the slit 13 (the connection position between the folded body 12 and the inner tube body 11), the space at the bottom of the slit 13 is limited during the heating and shaping of the expandable sheath. Here, the slit 13 located at the distal end of the outer tube 30 is analyzed and described. Similarly, the distal end of the outer tube 30 also corresponds to the distal end of the inner tube 10. During the heating, extrusion, and shaping process of the expandable sheath, the slit 13 of the inner tube 10 is also being extruded and deformed, and the space is further reduced. Therefore, the portion of the outer tube 30 located within the slit 13 can only be released in large quantities toward the distal end of the expandable sheath and / or accumulate at the distal end of the slit 13.

[0097] First, a large amount of material at the distal end of the outer tube 30, located within the slit 13, is released distally. This results in a larger bonding area between the outer tube 30 and the constricted end 21 of the middle tube, increasing the tensile (tear) resistance of the constricted end 21 and making it difficult for the expandable sheath to expand. Furthermore, the accumulation of material at the distal end of the outer tube 30 within the slit 13 causes the inner tube's folded body 12 to lift. During the expansion of the sheath into the body, the folded body 12, due to the excessive material between the inner and outer tubes 30 at the distal end of the slit 13, cannot tightly adhere to the expandable sheath (or cannot form a relatively smooth surface; for example, the accumulation of material in the outer tube 30 causes raised points in this area). Therefore, a first thinning outer tube opening 31 is provided at the distal end of the outer tube 30 at the seam 13, so that the distal end of the outer tube 30 forms a non-overlapping circular structure, namely the outer tube extension and contraction head 30b. Here, the circle is a complete circle, that is, the circle formed by the distal end of the outer tube 30, namely the outer tube extension and contraction head 30b, is about 360°. This, in turn, cooperates with the constricted end 21 of the middle tube to form a uniform and consistent structure of the distal end of the expandable sheath, so that its performance is uniform and the mechanical properties of the distal end of the expandable sheath are uneven due to different structures, which would cause the distal end of the expandable sheath to warp or other phenomena.

[0098] Secondly, since the first thinning outer tube opening 31 of the outer tube 30 and the narrowing tear opening 22 of the middle tube 20 are both located at the distal end of the seam 13, and their positions correspond, a void is formed between the distal end of the folded body 12 of the inner tube 10 and the distal end of the inner tube body 11. Therefore, the connection between the distal end of the folded body 12 and the inner tube body 11 will sink to a certain extent. After sinking, the distal end of the folded body 12 will adhere to the narrowing tear opening 24 of the middle tube narrowing end 22 and the distal end of the outer tube 30 to a certain extent. However, the adhesion surface is small, and its force is also small. It is very easy to tear apart when the folded body 12 of the expandable sheath expands. Therefore, it will not affect the expansion of the folded body 12, but it effectively prevents the distal end of the expandable sheath from curling up. Here, after the outer tube 30 is compressed and thinned, it cannot withstand excessive tearing force and is very easy to break. Therefore, if the traditional split-type middle tube constriction end is not integrated with the middle tube 20, the outer tube 30 cannot provide a large force to the middle tube constriction end 21. As a result, the traditional split-type middle tube constriction end is extremely prone to detachment during the breakage process when the delivery system passes through. However, here the middle tube constriction end 21 is integrated with the middle tube 20 and is stably fixed by the middle tube 20. Therefore, the middle tube constriction end 21 will not be at risk of detachment.

[0099] Since the middle layer tube 20 serves to bond the inner layer tube 10 to the outer layer tube 30, it is obvious that the middle layer tube 20 can also bond the inner layer tube 10 to the inner layer tube 10. Therefore, it is necessary to ensure that the outer tube opening 31 for the first thinning is not allowed to make contact between the folded body 12 and the inner tube body 11 through the middle layer tube 20. Therefore, the size of the constriction tear 22 can be larger than the size of the first thinning tube opening 31, so that the outer tube body 30a around the first thinning tube opening 31 can isolate the inner tube body 11 and the folded body 12 at the radial direction of the constriction tear 22 to avoid adhesion. Specifically, the distance from the side of the first thinning outer tube opening 31 to the connection point between the folded body 12 and the inner tube body 11 is not greater than the distance from the side of the narrowing tear opening 22 to the connection point between the folded body 12 and the inner tube body 11, or in other words, the width L2 of the first thinning outer tube opening 31 is not greater than the width L1 of the narrowing tear opening 22, i.e., L2≤L1. Similarly, the distance from the deep edge of the first thinning outer tube opening 31 to the proximal end of the narrowing end 21 of the middle tube is not greater than the distance from the deep edge of the narrowing tear opening 22 to the proximal end of the narrowing end 21 of the middle tube, or in other words, the length H2 of the first thinning outer tube opening 31 is not greater than the length H1 of the narrowing tear opening 22, i.e., H2≤H1.

[0100] The outer tube body 30a has, in the radial direction from one side of the groove to the other side of the groove, a main body region 33, an overlapping region 34, and a covering region 35. One side of the main body region 33 is a groove side of the outer tube body 30a, and the distal end of this side of the main body region 33 has a first thinning outer tube opening 31. This side of the main body region 33 is disposed in the slot 13 of the inner tube 10 and is located between the middle tube body 20a and the folded body 12. One side of the overlapping region 34 is integrally formed on the other side of the main body region 33. The overlapping region 34 overlaps with a portion of the main body region 33 in the radial direction. The overlapping region 34 corresponds to the first thinning outer tube opening 31 in the axial direction. The overlapping region 34 covers the outer wall of the folded body 12. The overlapping area 34 of the outer tube 30 ensures that the folded body 12 of the inner tube 10 fits better with the outer tube 30. Because the outer tube 30 is made of HDPE material, it can better maintain its shape. Therefore, the overlapping area 34 partially covers the folded body 12 of the inner tube 10. Here, as... Figures 5C-5ETo increase the coverage area of ​​the overlapping area 34 over the folded body 12, an additional covering area 35 is added to the groove side of the outer tube 30 where the first thinning outer tube opening 31 is not provided. The additional covering area 35 is integrally formed with the overlapping area 34 of the outer tube 30. One side of the additional covering area 35 is integrally formed on the other side of the overlapping area 34. The other side of the additional covering area 35 is the other groove side of the outer tube body 30a. The additional covering area 35 overlaps radially with a portion of the main body area 33. The additional covering area 35 covers the second partial outer wall of the folded body 12. However, the distal end of the additional covering area 35 is located on the proximal side of the distal end of the overlapping area 34, so that the additional covering area 35 forms a second thinning outer tube opening 36 at the distal end of the overlapping area 34, preventing the additional covering area 35 from causing a double-layer structure at the distal end of the outer tube 30.

[0101] Here, to make the distal end of the expandable sheath more regular and reduce the increased friction between the expandable sheath and the blood vessel wall caused by unevenness at different locations due to the overlapping positions of various tube layers, the length H3 of the second thinning outer tube opening 36 formed by the covering area 35 and the overlapping area 34 is equal to the length H2 of the first thinning outer tube opening 31, i.e., the dimensions are consistent. The width of the covering area 35 here is adjusted and set by those skilled in the art according to the actual width of the folded body 12 without requiring creative work, and will not be elaborated again. However, the overlapping area 34 will not completely cover the folded body 12, that is, the inner surface of the overlapping area 34 will not contact the outer surface of the outer tube. Similarly, after the overlapping area 34 is supplemented with the covering area 35, the covering area 35 will not completely cover the folded body 12, that is, the inner surface of the covering area 35 will not contact the outer surface of the outer tube 30 and the first thinning outer tube opening 31.

[0102] At this time, the overlapping area 34 and / or the additional covering area 35 (one of the two and / or the combination thereof may be referred to as the overlapping covering area) are not bonded to the folded body 12 of the inner tube 10 that they are in contact with. A significant advantage of not bonding here is that, as the delivery device expands and unfolds the folded body 12 of the inner tube 10 when passing through the expandable sheath, the folded body 12 will open against the overlapping covering area of ​​the outer tube 30. Therefore, the overlapping covering area and the folded body 12 are not connected, so no internal stress is generated between them, which increases the resistance when the folded body 12 opens, thereby reducing the difficulty for the delivery device to pass through the interior of the expandable sheath. Here, since the material of the outer tube 12 is HDPE, the HDPE material has good plasticity retention properties and can maintain its shape well, pressing the folded body firmly onto the outer tube.

[0103] Furthermore, even if the side of the folded body 12 that is far from the connection point with the inner tube body 11 is not covered by the overlapping area, the folded body and the outer tube will still adhere to each other to a certain extent during the extrusion heat setting process of the expandable sheath (adhesion here means that the two are tightly attached together, but the force of the attachment is small and they can be separated when subjected to external force). Therefore, the folded body 12 will not separate from the outer tube 30.

[0104] Although the folded body 12 will not separate from the outer tube 30, it is still undesirable to eliminate the overlapping coverage area. This is because the material of the folded body 12 is relatively soft and lacks support, especially since the connection between the folded body 12 and the inner tube body 11 requires bending. Since expandable sheaths generally have a certain length, they need to penetrate a certain distance into the body to achieve their purpose. Without the overlapping coverage area protecting the connection between the folded body 12 and the inner tube body 11, the expandable sheath will rub against the inner wall of the blood vessel when it enters the vessel. This is especially true at the distal end of the expandable sheath, which, as the leading edge, first encounters the blood vessel and needs to dilate it. Furthermore, the distal end of the expandable sheath travels the longest path. Therefore, without the overlapping coverage area protecting the connection between the folded body 12 and the inner tube body 11, the distal end of the connection is highly susceptible to warping due to friction between the expandable sheath and the blood vessel. Thus, the overlapping coverage area effectively ensures a tight fit between the folded body 12 and the outer tube 30. The above describes the advantages of the overlapping coverage area and the advantages of the non-adhesive design between the overlapping coverage area and the folded body 12. However, these descriptions are not limiting, because those skilled in the art can, based on this application, change the structure of the outer tube without the groove side of the first thinning outer tube opening 31 and remove some material, so that the folded body 12 is no longer covered by the overlapping coverage area. Similarly, those skilled in the art can, based on this application, adhere the folded body 12 to the overlapping coverage area without creative effort. Therefore, such a design should also fall within the protection scope of this invention.

[0105] The diameters of the constricted end 21 of the middle tube and the extended constricted end 30b of the outer tube gradually decrease distally, forming a constriction at the distal end of the expandable sheath. When the expandable sheath, together with the dilator, enters the blood vessel, it increases the fit between the distal end of the expandable sheath and the dilator, preventing blood from seeping through the interface between the distal end of the expandable sheath and the dilator. Simultaneously, it creates a relatively smooth surface at the interface between the distal end of the expandable sheath and the dilator, which is more conducive to protecting the inner wall of the blood vessel. The design of the first thinning of the distal end of the expandable sheath using the outer tube opening 31 and the constriction tear opening 22 ensures that the delivery device encounters less resistance and is easier to penetrate; furthermore, the constriction opening will not fall off after being breached.

[0106] like Figures 7A-7BAs shown, in some embodiments, to increase the integrity of the expandable sheath surface (material integrity surface), an elastic layer 40 may be added to the outside of the outer tube 30. The elastic layer 40 has good elasticity and can adapt to the expansion and contraction of the expandable sheath. Here, the material of the elastic layer 40 is an elastic outer sheath, which may include or may be entirely formed of one or more materials such as low-hardness polyurethane, styrene elastomer, latex, or low-hardness PEBAX. Here, in order to make the position of the elastic layer 40 stable relative to the outer tube during the elastic deformation process, the elastic layer 40 is fixedly connected to the outer tube 30 on the side away from the folded body 12 and the inner tube body 11, that is, smoothly, so that the elastic layer 40 will not twist with the outer tube 30 due to uneven elasticity during the deformation process. Secondly, the elastic layer 40 not only increases the integrity of the expandable sheath surface, but its elasticity also helps to compress the expandable sheath to contract rapidly after the delivery device passes through it. Moreover, during the expansion and contraction of the expandable sheath, the outer surface of the expandable sheath is a complete circle, and the expandable sheath will not have gaps due to the expansion and contraction process.

[0107] In some embodiments, in order to reduce the friction between the expandable sheath and the blood vessel, a water-soluble lubricating coating is added to the surface of the expandable sheath. This forms a lubricating layer on the surface of the expandable sheath after it enters the blood vessel, reducing the damage to the blood vessel caused by friction during the process of the expandable sheath entering the blood vessel. It also reduces the force required for the expandable sheath to enter the blood vessel, thus reducing the difficulty of operation.

[0108] A stable polymer solution is applied to the outer surface of the expandable sheath, and the expandable sheath is dried. Then, a hydrophilic polymer that does not react chemically with the stable polymer coating is added (bonded) as a surface layer. The expandable sheath is then dried again, resulting in a solid, water-soluble lubricating expandable sheath coating.

[0109] The polymer solution can be based on cellulose esters with strong adhesion to increase the adhesion between the coating and the surface of the expandable sheath. The choice of hydrophilic polymer is crucial to the quality of the coating's lubrication. Polyvinylpyrrolidone (PVP), as a water-soluble polymer, has good physiological compatibility and solubility, making it suitable as a lubricating layer for expandable sheaths. In a dry state, an expandable sheath coated with a water-soluble lubricating coating is no different from a regular expandable sheath. When the coating comes into contact with an aqueous liquid, PVP molecules rapidly absorb water to form a hydrophilic gel layer that does not detach, providing sufficient lubrication when the expandable sheath enters the blood vessel. Experiments have shown that as the PVP coating content increases, the coefficient of friction on the expandable sheath surface gradually decreases. This is because with increased PVP content, more PVP molecules entangle with the expandable sheath surface, resulting in a thicker hydrogel layer after water absorption. The aggregation of water molecules reduces the frictional area between the expandable sheath and external tissues, thus lowering the coefficient of friction. The selection of the PVP coating content is a matter that can be easily determined by those skilled in the art based on actual conditions without creative effort, and will not be elaborated further here. This method not only minimizes the friction of the expandable sheath against the blood vessel, reduces patient pain, and improves ease of operation, but also significantly enhances safety.

[0110] In this example, the proximal section of the expandable sheath has a flared section whose diameter gradually increases towards the proximal end. Therefore, the proximal sections of the inner tube 10, the middle tube 20, and the outer tube 30 are also flared sections. The flared sections enable the proximal end of the expandable sheath to cooperate with the conical connection of the expander, and also make the proximal end of the sheath expand, which facilitates the entry of the instrument and directly supports the expansion of the sheath, allowing the instrument to enter the human body through the sheath.

[0111] The steps of a preferred embodiment of the method for manufacturing an expandable sheath provided by the present invention are as follows:

[0112] S1. An inner tube 10 with an inner diameter greater than the outer diameter of a core tube is fitted over the core tube. The inner tube 10 is tightly attached to the outer wall of the core tube to form an inner tube body 11. The portion of the inner tube that extends beyond the inner tube body 11 is folded to form a folded body 12. The folded body 12 is attached to the side wall of the inner tube body 11 to form a slit 13.

[0113] S2. A middle layer tube 20 with an inner diameter smaller than the outer diameter of the liner tube is cut axially to form a middle tube groove 23. A constriction and tearing opening 22 is radially cut on one side of the groove of the middle layer tube 23 near the distal end. The middle layer tube 20 covers the outer wall of the inner tube body 11. The side of the groove of the middle layer tube 20 with the constriction and tearing opening 22 is inserted into the gap 13 of the inner tube 10. Preferably, the side of the groove of the middle layer tube 20 is inserted into the bottom of the gap 13 of the inner tube 10, and the other side of the groove of the middle layer tube 20 is attached to the other side of the inner tube body 11. After aligning the distal end of the constriction and tearing opening 22 with the distal end of the gap, the distal end of the middle layer tube 20 is exposed and protrudes from the distal ends of the inner tube 10 and the outer tube 30, thereby forming a constricted end 21 of the middle tube. The side of the groove of the middle layer tube 20 is inserted into the bottom of the gap 13 of the inner tube 10.

[0114] S3. An outer tube 30 with an inner diameter larger than the outer diameter of the liner tube is cut axially to form an outer tube groove 32. A first thinning outer tube opening 31 is cut at the distal end of one side of the groove in the outer tube 30. Alternatively, a first thinning outer tube opening 31 is first cut at the distal end of the outer tube 30, and then the outer tube is cut axially along one side of the first thinning outer tube opening 31 to form an outer tube groove 32. The outer tube 30 covers the outer wall of the middle tube 20. The outer tube 30 has a groove side of a first thinning outer tube opening 31 that is inserted into the slit 13 of the inner tube 10 and is located between the middle tube 20 and the folded body 12. Preferably, one groove side of the outer tube 30 is inserted into the bottom of the slit 13 of the inner tube 10, and the other groove side of the outer tube 30 is attached to and covered on the outer wall of the folded body 12, wherein the distal end of the outer tube 30 and the distal end of the inner tube 10 are aligned with the proximal end of the constricted end 21 of the middle tube.

[0115] S4. A first heat shrink tubing is installed on the outer tube 30 to form the first tube.

[0116] S5. The first tube is heated at a high temperature, such as 280℃-300℃, for 5-8 minutes. The heat-shrink tubing continuously shrinks and compresses the expandable sheath at this high temperature, causing the three layers of the expandable sheath to bond tightly. The outer tube 30 and the middle tube 20 melt at this temperature, bonding tightly together. The middle tube 20, due to its more branched molecular chains, is relatively more active and thus adheres to the unmelted inner tube. Under the compression of the heat-shrink tubing, the three form a complete whole. The outer tube at the distal end of the expandable sheath also adheres to the contraction and tearing area 24 of the contraction end 21 of the middle tube in a molten state, forming a whole. The contraction end 21 of the middle tube, due to the combined effects of melting and compression, also has its position at the groove 23 of the middle tube affected by the contraction end 21. The tube is covered, so the constricted end 21 of the middle tube forms a complete circle. Similarly, the forward-extending part of the outer tube 30 is also evenly covered on the surface of the constricted end 21 of the middle tube under the action of extrusion pressure, and connected with the constricted end 21 of the middle tube (especially the constricted tearing area 24) to form the outer tube extension head 30b. The constricted end 21 of the middle tube and the outer tube extension head 30b form a smooth surface of the distal end of the expandable sheath. After the first shaping is completed, the product is then cooled to remove the first heat shrink tube and the liner tube, and a semi-finished expandable sheath tube is obtained.

[0117] S6. A shaped core tube 60 is inserted into the semi-finished expandable sheath obtained in step S5. The proximal end of the shaped core tube 60 has a flared conical section 61 for forming a flared conical structure for connecting the proximal end of the expandable sheath to the operating handle, while the distal end of the shaped core tube 60 has a constricted conical section 64 for forming a constricted structure at the distal end of the expandable sheath.

[0118] S7. The semi-finished product obtained in step S6 can be expanded by adding a certain type of heat shrink tubing to form a second tubing.

[0119] S8. Heat the second tube at a high temperature, such as 280℃-300℃, for 4-6 minutes. The heat shrink tubing continuously shrinks and compresses the expandable sheath at high temperature, so that the semi-finished expandable sheath fits tightly with the shaping core tube 60 to form the required flared conical structure at the proximal end of the expandable sheath for connection with the operating handle and the required constriction at the distal end of the expandable sheath. After completing the secondary shaping, the shaping core tube 60 and the shaping heat shrink tubing are then cooled and removed to obtain the final expandable sheath tube. After that, it is assembled with the operating handle to complete the entire expandable sheath product.

[0120] Before performing step S1, in order to better bond the middle layer tube 20 with the inner layer tube 10, the inner layer tube 10 can be etched.

[0121] In order to maintain the smoothness of the inner surface of the inner tube 10, the two ends of the inner tube 10 can be sealed when etching the inner tube 10, so only the outer surface of the inner tube 10 is etched.

[0122] In step S1, the inner diameter of the inner tube 10 before folding can be, for example, 1.4-1.8 times the outer diameter of the liner tube. More preferably, the inner diameter of the inner tube 10 before folding can also be 1.5-1.7 times the outer diameter of the liner tube. Preferably, the inner diameter of the inner tube 10 before folding can be 1.6 times the outer diameter of the liner tube.

[0123] Before step S2, a developing ring 50 is selectively added according to the actual needs of the expandable sheath. A developing ring 50 is produced or provided. According to the position and size of the constriction and tear opening 22 of the designed middle tube 20, the distal part of the inner tube 10 is measured to determine the installation position of the developing ring 50. After confirming the installation position of the developing ring 50, one side of the opening 51 of the developing ring 50 is inserted into the bottom of the gap 13 of the inner tube 10. The main body of the developing ring 50 is attached to the inner tube body 11, and the other side of the opening 51 corresponds to the other side of the inner tube body 11, so that the distal end of the developing ring 50 is flush with the proximal end of the constriction and tear opening 22.

[0124] In step S2, the inner diameter of the middle layer tube 20 before cutting the middle tube groove 23 can be 0.95-0.8 times the outer diameter of the liner tube. Preferably, the inner diameter of the middle layer tube 20 before cutting the middle tube groove 23 can be 0.9 times the outer diameter of the liner tube. The cutting shape of the constriction tear 22 is not limited, but it is preferably rectangular. A stress-reducing notch 25 can be further cut at the distal end of the constriction tear 22 near the bottom of the slit 13. The stress-reducing notch 25 is integrally connected with the constriction tear 22.

[0125] In step S3, the inner diameter of the outer tube 30 before cutting the outer tube groove 32 can be 1.1-1.3 times the outer diameter of the core tube. Preferably, the inner diameter of the outer tube 30 before cutting the outer tube groove 32 can be 1.2 times the outer diameter of the core tube. The size of the first thinning outer tube opening 31 cut on the outer tube 30 is smaller than the size of the constriction and tear opening 22 cut on the middle tube 20, and the first thinning outer tube opening 31 and the constriction and tear opening 22 are aligned radially. In step S3, after axially cutting to form the outer tube groove 32, a second thinning outer tube opening 36 can be cut at the distal end of the other groove side of the outer tube 30; or, after cutting a first thinning outer tube opening 31 at the distal end of the outer tube 30, a second thinning outer tube opening 36 can be cut at the distal end of the outer tube 30 close to the axial side of the first thinning outer tube opening 31. Therefore, the axial side of the first thinning outer tube opening 31 and the axial side of the second thinning outer tube opening 36 are interconnected and share an axial connecting line. Then, the outer tube 30 is axially cut along the axial connecting line of the first thinning outer tube opening 31 and the second thinning outer tube opening 36 to form the outer tube groove 32. At this time, the axial connecting line coincides with the distal end of the outer tube groove 32. Preferably, the dimensions of the first thinning outer tube opening 31 and the second thinning outer tube opening 36 are the same.

[0126] In step S6, such as Figure 9 As shown, the shaping core tube 60 comprises, from proximal to distal, a flared conical section 61 with an outer diameter that gradually increases from distal to proximal, a main body section 62 with a constant outer diameter, and a constricted conical section 64 with an outer diameter that gradually decreases from proximal to distal. The proximal section of the constricted conical section 64 has a marking section 63. The outer diameter of the main body section 62 of the shaping core tube 60 is equal to the inner diameter of the semi-finished expandable sheath. The outer diameter of the constricted conical section 64 of the shaping core tube 60 gradually decreases distally, while the outer diameter of the flared conical section 61 of the shaping core tube 60 gradually increases proximally. The constricted end 22 of the semi-finished expandable sheath is placed in the constricted conical section 64 of the shaping core tube 60; the constricted end 22 of the distal end of the semi-finished expandable sheath is placed in the marking section 63 of the shaping core tube 60; and the proximal end of the semi-finished expandable sheath is placed in the flared conical section 61 of the shaping core tube 60. It should be noted here that the specific position of the marking segment 63 should be adjusted according to the actual situation of use, such as the size of the expandable sheath, including the relationship between the length of the expandable sheath and the length of the shaped core tube 60, depending on actual needs, and is not subject to this limitation.

[0127] In step S7, since the proximal end of the expandable sheath has a flared conical structure, if the diameter of the proximal end of the flared conical structure is too large, the outer tube of the proximal end of the expandable sheath tube cannot form a complete circle. This can cause problems such as poor sealing when assembled with the operating handle. Therefore, an extra layer of the same material as the outer tube, such as HDPE, can be added to the proximal section of the semi-finished expandable sheath tube obtained in S6, and then a shaped heat shrink tubing can be added to form a complete flared conical structure made of the outer tube material at the proximal end of the expandable sheath during the heat shrink tubing and heat treatment in S8.

[0128] After step S8, step S9 may be added, in which an elastic layer 40 is wrapped around the outer tube of the expandable sheath, and / or a coating is applied to the outer tube of the expandable sheath.

[0129] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing an expandable sheath, characterized in that, Includes the following steps: S1. An inner tube with an inner diameter larger than the outer diameter of a core tube is fitted over the core tube. The inner tube is tightly attached to the outer wall of the core tube to form an inner tube body. The portion of the inner tube that extends beyond the inner tube body is folded to form a folded body. The folded body is attached to the side wall of the inner tube body to form a slit. S2. A middle layer tube with an inner diameter smaller than the outer diameter of the core tube is cut axially to form a middle tube groove. A constriction and tearing opening is radially cut on the side of one groove of the middle layer tube near the distal end. The middle layer tube covers the outer wall of the inner tube body. The side of the middle layer tube with the constriction and tearing opening is inserted into the slit of the inner tube. The other side of the middle layer tube is attached to the other side of the inner tube body. After aligning the distal end of the constriction and tearing opening with the distal end of the slit, the distal end of the middle layer tube protrudes beyond the distal ends of the inner and outer tubes, thereby forming a constricted end of the middle tube. S3. An outer tube with an inner diameter larger than the outer diameter of the core tube is axially cut to form an outer tube groove. A first thinning outer tube opening is cut at the distal end of one groove side of the outer tube. Alternatively, a first thinning outer tube opening is first cut at the distal end of an outer tube, and then the outer tube is axially cut with one axial side of the first thinning outer tube opening as the axial direction to form an outer tube groove. The outer tube covers the outer wall of the middle tube. The outer tube with one groove side of the first thinning outer tube opening is inserted into the slit of the inner tube and located between the middle tube and the folded body. The other groove side of the outer tube fits and covers the outer wall of the folded body. The distal ends of the outer tube and the distal ends of the inner tube are aligned with the proximal end of the constricted end of the middle tube. S4. A first heat-shrink tubing is fitted over the outer tube to form a first tubing. S5. The first tube is heated at a high temperature, and then cooled to remove the liner tube and the first heat shrink tube, to obtain a semi-finished expandable sheath tube.

2. The method for manufacturing an expandable sheath as described in claim 1, characterized in that, It also includes the following steps: S6. Insert a certain core tube into the semi-finished expandable sheath obtained in step S5, wherein the outer diameter of the main body of the core tube is equal to the inner diameter of the semi-finished expandable sheath, the outer diameter of the distal section of the core tube gradually decreases towards the distal end, and the outer diameter of the proximal section of the core tube gradually increases towards the proximal end. S7. A certain type of heat shrink tubing is then fitted over the expandable sheath obtained in step S6 to form a second tubing. S8. The second tubing is heated at a high temperature, and then cooled to remove the shaped core tube and the shaped heat shrink tube, to obtain the final product, the expandable sheath tube.

3. The method for manufacturing an expandable sheath as described in claim 1 or 2, characterized in that, The groove side of the middle layer tube in step S2 and / or the groove side of the outer layer tube in step S3 are inserted into the bottom of the slot of the inner layer tube.

4. The method for manufacturing an expandable sheath as described in claim 2, characterized in that, In step S3, the size of the first thinning outer tube opening cut from the outer tube is smaller than the size of the constriction and tear opening cut from the middle tube, and the first thinning outer tube opening and the constriction and tear opening are aligned radially.

5. The method for manufacturing an expandable sheath as described in claim 2, characterized in that, In step S6, the shaping core tube includes, from the proximal end to the distal end, the following: The segment comprises a flared conical segment with an outer diameter that gradually increases from the distal end to the proximal end, a main body segment with a constant outer diameter, and a constricted conical segment with an outer diameter that gradually decreases from the proximal end to the distal end, wherein the proximal segment of the constricted conical segment has a marking segment.

6. The method for manufacturing an expandable sheath as described in claim 5, characterized in that, In step S6, the constricted end of the middle tube is placed in the constricted tapered section of the shaped core tube.

7. The method for manufacturing an expandable sheath as described in claim 1, characterized in that, In step S2, a force-reducing notch is further cut at the distal end of the contraction and tear opening near the bottom of the gap, and the force-reducing notch is integrally connected with the contraction and tear opening.

8. The method for manufacturing an expandable sheath as described in claim 1, characterized in that, In step S2, the shape of the contracted tear is rectangular.

9. The method for manufacturing an expandable sheath as described in claim 5, characterized in that, In step S6, the constricted end of the distal tube of the semi-finished expandable sheath is placed on the marked section of the shaped core tube.

10. The method for manufacturing an expandable sheath as described in claim 1, characterized in that, In step S3, After axially cutting to form the outer tube groove, a second thinning outer tube opening is cut at the distal end of the other groove side of the outer tube; or... First, a first thinning outer tube opening and a second thinning outer tube opening are cut at the far end of a groove side of the outer tube. The axial side of the first thinning outer tube opening and the axial side of the second thinning outer tube opening are connected to each other and share an axial connecting line. Then, the outer tube is axially cut along the axial connecting line to form the outer tube groove.

11. The method for manufacturing an expandable sheath as described in claim 10, characterized in that, The first thinning outer tube opening has the same size as the second thinning outer tube opening.

12. The method for manufacturing an expandable sheath as described in claim 5, characterized in that, In step S6, the proximal end of the semi-finished expandable sheath is placed in the flared conical section of the shaped core tube.

13. The method for manufacturing an expandable sheath as described in claim 2, characterized in that, In step S5, the heating temperature range is 280℃-300℃, and the heating time is 5-8 minutes; In step S8, the heating temperature range is 280℃-300℃, and the heating time is 4-6 minutes.

14. The method for manufacturing an expandable sheath as described in claim 1, characterized in that, In step S1, the inner diameter of the inner tube before folding is 1.4-1.8 times the outer diameter of the core tube; In step S2, the inner diameter of the middle layer tube before cutting the middle tube groove is 0.8-0.95 times the outer diameter of the liner tube; In step S3, the inner diameter of the outer tube before cutting the outer tube groove is 1.1-1.3 times the outer diameter of the liner tube.

15. The method for manufacturing an expandable sheath as described in claim 14, characterized in that, In step S1, the inner diameter of the inner tube before folding is 1.5 to 1.7 times the outer diameter of the core tube; In step S2, the inner diameter of the middle layer tube before cutting the middle tube groove is 0.9 times the outer diameter of the liner tube; In step S3, the inner diameter of the outer tube before cutting the outer tube groove is 1.2 times the outer diameter of the liner tube.

16. The method for manufacturing an expandable sheath as described in claim 15, characterized in that, In step S1, the inner diameter of the inner tube before folding is 1.6 times the outer diameter of the liner tube.

17. The method for manufacturing an expandable sheath as described in claim 1, characterized in that, Before step S1, the proximal and distal ends of the inner tube are sealed, and then the outer surface of the inner tube is etched.

18. The method for manufacturing an expandable sheath as described in claim 1, characterized in that, Before step S2, an open developing ring is fitted over the inner tube body, with one end of the developing ring inserted into the bottom of the slit and the other end of the developing ring attached to the other side of the inner tube body. In step S2, the position of the developing ring is adjusted so that the distal end of the developing ring is aligned with the proximal end of the constricted tear.

19. The method for manufacturing an expandable sheath as described in claim 2, characterized in that, In step S7, a layer of the same material as the outer tube is first wrapped around the proximal section of the semi-finished expandable sheath, and then the shaping heat shrink tubing is installed.

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