Two special valves used after decay of surgical mitral valve and tricuspid valve

Abstract

The invention discloses two special valves for surgical mitral valves and tricuspid valves after decay, which belong to the technical field of medical instruments and comprise a middle cylindrical section, two ends of the middle cylindrical section are respectively connected with an upper-end horn mouth and a lower-end horn mouth, and transition sections with smooth inner walls are formed between the horn mouths at two ends and the middle cylindrical section through gradually changing diameters. The edge of the upper-end horn mouth and the edge of the lower-end horn mouth are each formed by arranging a plurality of rhombus units in the circumferential direction, a plurality of contact points are arranged on the upper-end horn mouth, the contact points are distributed in a high-low alternating mode in the circumferential direction, each contact point is located between every two adjacent rhombus units, and the device is simple in structure, capable of being recycled and repositioned and small in minimally invasive implantation trauma.

Description

Technical Field

[0001] This invention belongs to the field of medical device technology, and in particular relates to two examples of special valves for surgical mitral and tricuspid valve failure. Background Technology

[0002] Heart valve disease is a common heart disease in my country. Due to concerns about the risks of bleeding and thrombosis associated with lifelong warfarin anticoagulation of mechanical valves, and the continuous advancements in bioprosthetic valve anti-calcification technology, an increasing number of surgical patients are choosing prosthetic bioprosthetic valves. Although the incidence of rheumatic valvular heart disease has gradually decreased in recent years, mitral valve replacement remains the most common cardiac valve replacement surgery, and the proportion of bioprosthetic valves chosen for artificial valves is increasing.

[0003] All bioprosthetic valve replacements face durability issues, requiring secondary surgery upon failure. However, secondary open-heart valve replacement surgery for bioprosthetic valve failure is highly invasive for elderly patients with weakened constitutions, and the mortality and complication rates are significantly higher than the initial valve replacement surgery. In recent years, interventional valve techniques such as transcatheter aortic valve implantation / replacement (TAVI / TAVR) have developed rapidly. When a bioprosthetic valve fails, interventional valve treatment within the bioprosthetic valve can be performed, a technique known as valve-in-valve.

[0004] Mitral valve bioprosthetic valve destruction is more complex than similar aortic valve surgeries due to the more intricate localization and the more complex anatomy of the surrounding coronary arteries, chordae tendineae, aortic valve, and left atrial appendage. In 2009, Cheung et al. in Canada first reported the successful use of transcatheter valve-in-valve (TCV-IN) technology for mitral valve bioprosthetic valve destruction. In 2012, Elmariah et al. first reported the use of the TCV-IN technique in the United States, and in 2015, Tada et al. in Japan first reported its application. In 2017, the U.S. Food and Drug Administration (FDA) officially approved interventional valves for the treatment of aortic and mitral valve bioprosthetic valve destruction. In 2019, the team at Beijing Anzhen Hospital successfully performed a mitral valve-IN procedure using a short-stent positioning key interventional valve and successfully promoted its application in multiple centers. In the following years, several centers in China successively used short-stent balloon dilation valves to successfully complete a series of mitral valve-IN procedures.

[0005] The TMVR multicenter registry study included 322 patients undergoing mitral valve-to-valve replacement therapy. The mean STS score was 9.2% ± 7.2%, NYHA functional class IV was 32.3%, and the left ventricular ejection fraction (LVEF) was 53.3% ± 11.5%. Of these, 59.9% underwent the procedure via the transapical approach, and 38.8% via the septal approach. The immediate success rate was 94.4%. Reasons for failure included valve displacement, the need for a second valve implantation, and left ventricular outflow tract obstruction. At 30 days post-procedure, the all-cause mortality rate was only 6.2%, the incidence of stroke and fatal hemorrhage was 2.3% each, and the vascular complication rate was only 1.6%.

[0006] For mitral valve bioprosthetic valve damage, interventional valve-in-valve technique is currently an important method to avoid re-open-heart surgery, but it also faces a series of challenges related to technical complexity and long-term uncertainties. Regarding anatomical complexity and key technical risks, left ventricular outflow tract obstruction (LVOTO) occurs in approximately 7.1% of cases, reaching up to 40% in specific situations, making it a primary contraindication for screening, with reported in-hospital mortality rates as high as 54%. Valve embolism and displacement are more common in cases of annular calcification (ViMAC) or angioplasty (ViR), with an incidence of approximately 0.8%, of which ViMAC reaches 3%. Paravalvular leak is more common in angioplasty treatment, with an incidence of 7.8%, associated with irregular anchoring zones. Regarding instrument and operational limitations, most balloon-dilatated valves currently used in these procedures (such as SAPIEN 3) were originally designed for the aortic valve and cannot be repositioned or retrieved at the mitral valve location, increasing the difficulty of the procedure. Although the mainstream approach is transapical or transseptal, the transapical approach requires access to the left ventricular ostium, resulting in relatively greater trauma. Regarding the uncertainty of long-term effects, implanting a new valve within an existing, smaller bioprosthetic valve may result in insufficient effective orifice area, leading to a higher transvalvular pressure gradient postoperatively. Furthermore, there is a lack of long-term follow-up data exceeding 5 years to confirm the long-term durability of valve-in-valve valves. In terms of the rigor of patient selection, precise evaluation using methods such as cardiac CTA is required, resulting in a high preoperative screening failure rate. Some patients are ineligible for the procedure due to unsuitable anatomical structures. Postoperatively, standardized anticoagulation therapy is necessary to reduce the risk of valvular thrombosis, but this may increase the risk of bleeding complications.

[0007] Therefore, developing a minimally invasive valve specifically designed for the anatomical features of the residual ring after mitral bioprosthetic valve failure, capable of intraoperative repositioning and retrieval, is of significant clinical value in improving surgical safety and reducing the incidence of complications. Summary of the Invention

[0008] In view of the above-mentioned problems in the prior art, the purpose of the invention is to provide a special valve for surgical mitral and tricuspid valve failure in two cases, so as to solve the technical problems of existing interventional valves being unable to be repositioned or retrieved at the mitral valve position, having poor compatibility with residual annulus, and having poor fixation effect.

[0009] To achieve the above objectives, the invention adopts the following technical solution: A special valve for surgical mitral and tricuspid valve failure, comprising a central cylindrical segment, an upper flared end connected to the upper end of the central cylindrical segment, and a lower flared end connected to the lower end of the central cylindrical segment. Both the upper and lower flared ends are connected to the central cylindrical segment via a gradually changing diameter transition section, the inner wall of which is smooth and stepless. The edge of the upper flared end is composed of several rhomboid units arranged circumferentially, as is the edge of the lower flared end. Several contact points are provided on the upper flared end, with these contact points distributed alternately at different heights along the circumference, each contact point located between two adjacent rhomboid units.

[0010] Furthermore, the apex of several rhomboid units at the upper flared end extends away from the central cylindrical section, and the sides of adjacent rhomboid units connect to form a continuous serrated unfolded edge.

[0011] Furthermore, the apex angles of several rhomboid units at the lower flared end extend away from the central cylindrical section, and the sides of adjacent rhomboid units connect to form a continuous serrated unfolded edge.

[0012] Furthermore, among the several contact points, the top of the higher contact point is higher than the apex of the rhombus element, while the top of the lower contact point is either level with or lower than the apex of the rhombus element.

[0013] Furthermore, the middle cylindrical section, the upper flared end, and the lower flared end are all composed of a mesh-like support woven from nickel-titanium shape memory alloy wires.

[0014] Furthermore, the grid density of the middle cylindrical section is greater than that of the upper and lower flared ends.

[0015] Furthermore, the mesh-like stent can be compressed to the compression state corresponding to the inner diameter of the delivery conduit under low temperature conditions, and can automatically return to the preset unfolded state under human body temperature conditions. Moreover, the mesh-like stent can be retracted to the compression state through the contact point when it is unfolded.

[0016] Furthermore, the inner wall of the middle cylindrical section is sutured and fixed with bio-valve leaflets.

[0017] Furthermore, the wall thickness of the upper and lower flared ends is less than the wall thickness of the middle cylindrical section.

[0018] Furthermore, the inner diameter of the middle cylindrical section is 25-31mm, the expansion diameter of the upper flared mouth is larger than the inner diameter of the middle cylindrical section, and the expansion diameter of the lower flared mouth is larger than the inner diameter of the middle cylindrical section.

[0019] Compared with the prior art, the invention has the following advantages:

[0020] Firstly, the upper and lower flared ends of the invention are each formed by a number of rhomboid units arranged circumferentially to form a continuous serrated unfolded edge. After the rhomboid units unfold, each apex can be embedded into the fibrous tissue of the residual ring edge like barbs. The multi-point anchoring effect generated by the even distribution of several rhomboid apex is far superior to the simple radial compression of the traditional smooth circular edge, which greatly reduces the risk of valve displacement and paravalvular leakage.

[0021] Secondly, the invention employs a mesh-like stent made of nickel-titanium shape memory alloy, which can be delivered into the heart through a narrow-diameter delivery catheter under cryogenic compression and automatically unfolds to a preset shape at body temperature. More importantly, if the valve is not in the ideal position after deployment, the operator can use several contact points in conjunction with the delivery device to retract the deployed valve back to the compressed state, adjust its position, and then release it again. This retrievable and repositionable function effectively solves the core defect of existing balloon-expanded valves that cannot be retrieved once deployed at the mitral valve location, significantly improving the safety and controllability of the surgery.

[0022] Thirdly, the invention employs an alternating high and low distribution of several contact points between adjacent diamond-shaped units at the upper flared end. This alternating high and low layout allows the delivery device to apply recovery force simultaneously from contact points at different heights. During the recovery process, the valve experiences more uniform force, making it less prone to skewing or local deformation, thus ensuring that the valve can be completely and smoothly returned to the delivery catheter.

[0023] Fourth, the invention smoothly connects the upper flared end, the middle cylindrical section, and the lower flared end through a gradually changing diameter. The inner wall of the transition section is smooth and stepless, preventing local turbulence and eddies when blood flows through the valve, resulting in excellent hemodynamic performance. The differentiated design, where the middle cylindrical section has a higher grid density than the upper and lower flared ends, provides sufficient radial support to maintain a tight fit with the residual annulus. At the same time, the thinner wall thickness and lower grid density of the upper and lower flared ends ensure a smooth unfolding adaptability, allowing them to conform to the edge contours of residual annulus with varying shapes, effectively reducing paravalvular leakage. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of the invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1A three-dimensional structural diagram of the invention in its unfolded state;

[0026] Figure 2 A schematic diagram of the three-dimensional structure of the invention in a fully reclaimed and compressed state;

[0027] Reference numerals: 1. Middle cylindrical section; 2. Upper flared end; 3. Lower flared end; 4. Contact point. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the invention clearer, the technical solutions of the invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] Reference Figure 1 and Figure 2 As shown, the invention provides two examples of a special valve for surgical mitral and tricuspid valve failure, employing a three-segment structure design. The middle section of the valve is a central cylindrical segment 1, with an upper bell-shaped opening 2 integrally connected to its upper end, and a lower bell-shaped opening 3 integrally connected to its lower end. The upper bell-shaped opening 2 is located on the side facing the atrium after valve implantation, and the lower bell-shaped opening 3 is located on the side facing the ventricle after valve implantation. Transition segments with gradually changing diameters are formed between the upper bell-shaped opening 2 and the central cylindrical segment 1, and between the lower bell-shaped opening 3 and the central cylindrical segment 1. The diameter of each transition segment gradually increases axially from the constant diameter section of the central cylindrical segment 1 towards both ends, forming a continuous and smooth bell-shaped unfolding profile. Furthermore, the inner wall of the transition segment has no steps or abrupt changes in cross-section, ensuring a continuous change in the flow channel cross-section as blood flows through the valve, avoiding local turbulence or eddies caused by abrupt changes in cross-section.

[0030] The central cylindrical section 1, the upper flared end 2, and the lower flared end 3 are all constructed from a mesh-like support woven from nickel-titanium shape memory alloy wires. Nickel-titanium shape memory alloy possesses excellent superelasticity and shape memory effect. Under low-temperature conditions, the alloy is in the martensitic phase and exhibits good plastic deformation capacity, allowing the entire valve to be compressed to an extremely small diameter comparable to the inner diameter of the delivery catheter. When the valve is inserted into the body via the catheter, the alloy automatically undergoes a reverse phase transformation under the influence of body temperature, restoring to the austenitic phase and driving the mesh-like support to automatically unfold from its compressed state to a pre-set three-dimensional shape. This temperature-driven self-expansion characteristic allows the valve to be released without balloon dilation, simplifying the surgical procedure.

[0031] The mesh weave density of the intermediate cylindrical segment 1 is greater than that of the upper flared end 2 and the lower flared end 3. This differentiated mesh density design has a clear functional purpose. The higher mesh density gives the intermediate cylindrical segment 1 stronger radial support stiffness, allowing it to form a tight radial fit with the inner wall of the residual ring after unfolding and maintain a stable tubular shape over a long period. This provides a stable support framework for the bioprosthetic leaflet sutured to the inner wall of the intermediate cylindrical segment 1. The inner wall of the intermediate cylindrical segment 1 is sutured and fixed with a bioprosthetic leaflet, which is cut from porcine or bovine pericardium that has been cross-linked with glutaraldehyde. During ventricular diastole, the leaflet opens to allow blood to flow smoothly from the atrium into the ventricle, and during ventricular systole, the leaflet closes to prevent blood from flowing back into the atrium. The inner diameter of the intermediate cylindrical segment 1 is designed to be 25-31 mm. This size range matches the mainstream bioprosthetic valve models implanted during the initial surgical replacement, ensuring sufficient effective blood flow area after secondary interventional treatment. The upper flared end 2 and the lower flared end 3 adopt a relatively low grid density and a thinner wall thickness, which gives them good flexibility and deformation adaptability. They can automatically fit the edge contour of the residual ring with different shapes during the unfolding process, effectively filling the irregular gaps at the edge of the residual ring to reduce the risk of perivalvular leakage.

[0032] Reference Figure 1 As shown, the unfolding edge of the upper funnel 2 is composed of several rhomboid units arranged sequentially along the circumference. The apex of each rhomboid unit extends outward toward the atrium, away from the central cylindrical segment 1. The sides of adjacent rhomboid units connect to form a continuous serrated unfolding edge. Similarly, the unfolding edge of the lower funnel 3 is composed of several rhomboid units arranged sequentially along the circumference. The apex of each rhomboid unit extends outward toward the ventricle, away from the central cylindrical segment 1. The sides of adjacent rhomboid units also connect to form a continuous serrated unfolding edge. After the valve unfolds, the rhomboid units of both the upper and lower funnels 2 and 3 radiate outward from both ends of the central cylindrical segment 1, forming two symmetrical rings of serrated anchoring structures. After the valve unfolds, the apex of each rhomboid unit embeds into the natural tissue space between the edge of the residual ring and the atrial or ventricular wall. The multi-point anchoring effect produced by several rhomboid apexes evenly distributed on the circumference can evenly disperse the force exerted by the valve on the surrounding tissue, avoiding tissue damage caused by local stress concentration. At the same time, the embedding depth of each rhomboid apex increases with the increase of the axial blood flow impact force on the valve, producing a self-reinforcing effect of the greater the impact force and the tighter the anchoring. The unfolding diameter of the upper funnel 2 is larger than the inner diameter of the middle cylindrical segment 1, and the unfolding diameter of the lower funnel 3 is also larger than the inner diameter of the middle cylindrical segment 1. The upper and lower serrated unfolding edges open outward on the atrial and ventricular sides of the residual ring respectively and apply radial adhesion force. The two work together to firmly clamp and lock the valve onto the residual ring.

[0033] The upper flared opening 2 has several contact points 4 located at the unfolded edge of the upper flared opening 2. Each contact point 4 is positioned at the connection node between two adjacent rhomboid units. The contact points 4 are divided into two groups: one group consists of higher contact points 4, and the other group consists of lower contact points 4. The two groups of contact points 4 are alternately distributed along the circumference of the upper flared opening 2, meaning that a higher contact point 4 and a lower contact point 4 are arranged alternately. The top of the higher contact point 4 is higher than the apex of the rhomboid unit, while the top of the lower contact point 4 is level with or slightly lower than the apex of the rhomboid unit. This alternating high and low layout design creates a three-dimensional distribution of contact points 4 in space, offering two functional advantages.

[0034] In terms of valve release, several contact points 4 are used for detachable connection with the release mechanism of the delivery device. After the valve is delivered to the heart through the delivery catheter in a compressed state, the release mechanism of the delivery device is fixed to several contact points 4 by clamping or snapping. The operator uses the control handle at the end of the catheter to control the release mechanism to release each contact point 4 in sequence to complete the gradual release of the valve. The alternating high and low contact point layout allows the release mechanism to release the valve in two stages: first, the lower contact points 4 are released to partially open the corresponding area of ​​the upper bellows 2, and then the higher contact points 4 are released to fully open the upper bellows 2. This step-by-step release method allows the operator to fine-tune the valve position through the still unreleased higher contact points 4 after the first stage of release, improving the accuracy and controllability of the release process.

[0035] In terms of valve retrieval, several contact points 4 simultaneously perform the retrieval function. If, after valve release, the operator detects an undesirable valve position through imaging such as transesophageal ultrasound, they can manipulate the retrieval mechanism of the delivery device to re-grasp several contact points 4. By simultaneously applying a centripetal retrieval force to these contact points 4, the deployed mesh-like stent is recompressed and pulled back into the delivery catheter. The varying spatial distribution allows the retrieval mechanism to apply force simultaneously from different heights during the grasping process. The retrieval force is evenly distributed along the circumference and axis across several contact points 4, preventing valve skewing, twisting, or localized collapse due to uneven force during retrieval. After retrieval, the operator can readjust the catheter position based on imaging guidance and re-release the valve to the correct position. This retrieval and repositioning function effectively solves the core defect of existing balloon-dilated valves that cannot be retrieved once released.

[0036] Reference Figure 2The diagram shows the structural form of the valve in its fully compressed state. In this state, the central cylindrical segment 1 is compressed into a narrow-diameter tubular body. Several rhomboid units at the upper flared end 2 and the lower flared end 3 fold inward to form two thin disc-shaped structures, which are respectively attached to the upper and lower ends of the central cylindrical segment 1. After full compression, the entire valve forms a spool-like appearance with the upper and lower thin discs clamping the central narrow-diameter tube. The overall outer diameter matches the inner diameter of the delivery catheter, facilitating delivery to the heart via the femoral vein through the interatrial septum or through the apex of the heart. The contact point 4 protrudes from the top surface of the upper thin disc in the compressed state, serving to maintain connection with the delivery device release mechanism.

[0037] It is important to note that although the leaflet function of the initially implanted mitral bioprosthetic valve has failed after deterioration, the valve annulus and the original human tissue have achieved stable fusion through years of fibrotic healing. The remaining valve annulus structure, i.e., the residual annulus, still retains a complete annular skeleton, with a diameter typically in the range of 25-31 mm. The invention utilizes this residual annulus as a natural fixation base. Several rhomboid units at the upper funnel 2 and lower funnel 3 are embedded into the edge tissue of the residual annulus from the atrial and ventricular sides, respectively. Combined with the radial tight fit between the middle cylindrical segment 1 and the inner wall of the residual annulus, a stable three-dimensional locking of the valve on the residual annulus is achieved without the need for additional drilling or sutures.

[0038] The intraoperative application of the invention is as follows: Preoperatively, a comprehensive assessment of the diameter, wall thickness, degree of calcification, and surrounding anatomical structures of the residual ring is conducted using transthoracic echocardiography or transesophageal echocardiography combined with cardiac CT, based on which an appropriate valve size and access method are selected. Intraoperatively, under general anesthesia and real-time monitoring via transesophageal echocardiography, the compressed valve is loaded into the delivery catheter system, and the delivery catheter is advanced to the residual ring location via a femoral vein puncture approach through the interatrial septum or a small apical incision approach. Under the dual image guidance of digital subtraction angiography and transesophageal echocardiography, the catheter position is precisely adjusted so that the central cylindrical segment 1 of the valve is aligned with the central axis of the residual ring before release. First, the lower funnel 3 is released, causing several rhomboid units to unfold on the ventricular side and embed into the ventricular edge of the residual ring. Then, the upper funnel 2 and several contact points 4 are released in stages. During the release process, the operator can observe the valve deployment in real time via ultrasound. If a positional shift is detected, fine-tuning can be performed using the incompletely released contact point 4. If necessary, the valve can be completely retrieved and repositioned using several contact points 4. After the valve is fully released, the nickel-titanium alloy stent automatically unfolds to the preset shape under body temperature. The central cylindrical segment 1 fits tightly against the inner wall of the residual ring, and the apexes of several rhomboid units at the top and bottom are embedded in the edge tissue on both sides of the residual ring to form multi-point anchoring. Finally, after confirming that the valve is in good position, opens and closes normally, and has no obvious paravalvular leakage via transesophageal ultrasound, the connection between the delivery device and contact point 4 is released, the delivery catheter system is withdrawn, and the surgery is completed.

[0039] The above description is merely a preferred embodiment of the invention and is not intended to limit the invention. Various modifications and variations can be made by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of the claims.

Claims

1. A two case of surgical mitral valve, tricuspid valve failure dedicated valve, characterized in that, The system includes a central cylindrical section (1), with an upper flared mouth (2) connected to the upper end of the central cylindrical section (1) and a lower flared mouth (3) connected to the lower end of the central cylindrical section (1). The upper flared mouth (2) and the lower flared mouth (3) are connected to the central cylindrical section (1) by a transition section with a gradually changing diameter. The inner wall of the transition section is smooth and without steps. The edge of the upper flared mouth (2) is composed of several rhomboid units arranged along the circumference. The edge of the lower flared mouth (3) is composed of several rhomboid units arranged along the circumference. The upper flared mouth (2) is provided with several contact points (4). The contact points (4) are distributed alternately at different heights along the circumference. Each contact point (4) is located between two adjacent rhomboid units.

2. Two cases of a special valve for surgical mitral and tricuspid valve failure as described in claim 1, characterized in that: The apex of several rhomboid units of the upper flared mouth (2) extends away from the middle cylindrical section (1), and the sides of adjacent rhomboid units are connected to form a continuous serrated unfolded edge.

3. Two cases of a special valve for surgical mitral and tricuspid valve failure as described in claim 1, characterized in that: The apex of several rhomboid units of the lower flared mouth (3) extends away from the middle cylindrical section (1), and the sides of adjacent rhomboid units are connected to form a continuous serrated unfolded edge.

4. Two cases of a special valve for surgical mitral and tricuspid valve failure as described in claim 1, characterized in that: Among the several contact points (4), the top of the contact point (4) with the higher position is higher than the apex of the rhombus unit, and the top of the contact point (4) with the lower position is level with or lower than the apex of the rhombus unit.

5. Two cases of a special valve for surgical mitral and tricuspid valve failure as described in claim 1, characterized in that: The middle cylindrical section (1), the upper flared end (2), and the lower flared end (3) are all composed of a mesh-like support woven from nickel-titanium shape memory alloy wires.

6. Two examples of a special valve for surgical mitral and tricuspid valve failure according to claim 5, characterized in that: The grid density of the middle cylindrical section (1) is greater than that of the upper flared end (2) and the lower flared end (3).

7. Two examples of a special valve for surgical mitral and tricuspid valve failure according to claim 5, characterized in that: The mesh-like support can be compressed to the compression state corresponding to the inner diameter of the delivery conduit under low temperature conditions, and can automatically return to the preset unfolded state under human body temperature conditions. Furthermore, the mesh-like support can be retracted to the compression state through the contact point (4) when it is unfolded.

8. Two cases of a special valve for surgical mitral and tricuspid valve failure according to claim 1, characterized in that: The inner wall of the intermediate cylindrical section (1) is sutured and fixed with a bio-valve leaflet.

9. Two examples of a special valve for surgical mitral and tricuspid valve failure according to claim 1, characterized in that: The wall thickness of the upper flared end (2) and the lower flared end (3) is less than the wall thickness of the middle cylindrical section (1).

10. Two examples of a special valve for surgical mitral and tricuspid valve failure according to claim 1, characterized in that: The inner diameter of the middle cylindrical section (1) is 25-31mm, the unfolded diameter of the upper flared mouth (2) is greater than the inner diameter of the middle cylindrical section (1), and the unfolded diameter of the lower flared mouth (3) is greater than the inner diameter of the middle cylindrical section (1).

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