A stone-blocking catheter and its preparation method

Abstract

This invention discloses a stone retrieval catheter, comprising a hollow outer sheath, the tail end of which is connected to the head end of a handle. The handle has a through-hole penetrating both the head and tail ends and communicating with the outer sheath. The head end of a push rod is located within the through-hole and slides freely within it. The head end of the push rod is connected to the tail end of a core wire, which in turn is connected to the tail end of a shape memory alloy spring. The head end of the core wire, along with the shape memory alloy spring, passes through the through-hole and the outer sheath sequentially, protruding from the head end of the outer sheath. A check valve, disc-shaped, is located at the head end of the outer sheath. The outer ring of the check valve is fixed to the inner wall of the head end of the outer sheath. A central channel hole, with a diameter matching the wire diameter of the core wire and the shape memory alloy spring, is located at the center of the check valve. This invention also discloses a method for preparing the stone retrieval catheter. The check valve effectively prevents leakage during surgery.

Description

Technical Field

[0001] This invention belongs to the field of medical devices, specifically relating to a stone-blocking catheter and a method for preparing the stone-blocking catheter; it is suitable for blocking and removing stone fragments. Background Technology

[0002] In urological surgery, to prevent stone fragments from penetrating deeper into the body, a stone-removing medical device is typically inserted behind the stone to seal it. After the stone fragments are broken up, they are removed. Among these devices, the stone-removing catheter is the most commonly used. However, existing stone-removing medical devices on the market have some drawbacks: For example, a stone-removing catheter produced by a Shanghai company has a relatively large gap in the sealing material after folding. During use, stone fragments may move upwards through this gap, causing secondary contamination of the urinary tract. Another example is a nickel-titanium alloy urinary system stone-removing mesh (occluder) produced in the United States. This product has a threaded structure that opens behind the stone. Because the mesh basket has a fixed opening size, it may not completely seal the ureter when opened behind the stone. Furthermore, during use, the lack of effective sealing of the catheter tip allows fluid to flow back along the catheter, contaminating the endoscope and other instruments, potentially leading to surgical failure. Summary of the Invention

[0003] The purpose of this invention is to overcome the deficiencies of the prior art and provide a stone-blocking catheter, as well as a method for preparing the stone-blocking catheter. The above-mentioned objective of this invention is achieved through the following technical means:

[0004] A stone-blocking catheter includes a hollow outer sheath, the tail end of which is connected to the head end of a handle. The handle has a through hole that passes through the head and tail ends and communicates with the tail end of the outer sheath. The head end of a push rod is located inside the through hole and slides freely within it. The head end of the push rod is connected to the tail end of a core wire, and the head end of the core wire is connected to the tail end of a shape memory alloy spring. The head end of the core wire, together with the shape memory alloy spring, passes through the through hole and the outer sheath in sequence and protrudes from the head end of the outer sheath. A check valve is provided at the head end of the outer sheath. The outer ring of the check valve is fixed to the inner wall of the head end of the outer sheath. A central channel hole is provided in the center of the check valve for the core wire and the shape memory alloy spring to pass through. The diameter of the central channel hole is adapted to the wire diameter of the core wire and the shape memory alloy spring.

[0005] The check valve includes a sealing ring and a buffer ring arranged concentrically. The inner side of the buffer ring is connected to the outer side of the sealing ring. The outer side of the buffer ring is fixed to the inner wall of the outer sheath. The thickness of the buffer ring is less than the thickness of the sealing ring.

[0006] The diameter of the core wire is the same as that of the shape memory alloy spring wire.

[0007] After the shape memory alloy spring is fully extended from the front end of the outer sheath, the diameter of the front end of the shape memory alloy spring is smaller than the diameter of the rear end.

[0008] When the push rod is not moving toward the outer sheath in the initial state, the shape memory alloy spring is completely retracted into the outer sheath.

[0009] The core wire is provided with a hydrophilic coating, and the shape memory alloy spring is provided with a hydrophobic coating.

[0010] The hydrophilic coating is polyvinylpyrrolidone (PVP), and the hydrophobic coating is polytetrafluoroethylene (PTFE).

[0011] A method for preparing a stone-blocking catheter includes the following steps:

[0012] Step 1: Select medical-grade polypropylene and prepare the outer sheath tube using a compression molding process;

[0013] Step 2: Select a nickel-titanium alloy and use a drawing process to make a core wire;

[0014] Step 3: The core wire obtained in Step 2 is laser-cut into a spring shape and the spring is immediately heat-treated to obtain a shape memory alloy spring;

[0015] Step 4: Use injection molding to manufacture the handle and push rod from medical-grade plastic;

[0016] Step 5: Use medical-grade silicone to manufacture a check valve through injection molding;

[0017] Step 6: Apply a hydrophilic coating to the core wire and a hydrophobic coating to the shape memory alloy spring;

[0018] Step 7: Weld the outer side of the check valve to the inner wall of the first end of the outer sheath tube. Insert the tail end of the core wire from the first end of the outer sheath tube, extend it through the check valve, and exit from the tail end of the outer sheath tube. Ensure that the memory alloy spring on the core wire is inside the outer sheath tube. Fix the tail end of the outer sheath tube to the first end of the handle. Fix the tail end of the core wire to the first end of the push rod. Insert the push rod into the handle through hole of the handle. Finally, wrap the anti-slip strip around the handle.

[0019] The application of the hydrophilic coating includes the following steps:

[0020] Step 1: Use ethanol or isopropanol solvent to perform ultrasonic cleaning on the core wire;

[0021] Step 2: Mix polyvinylpyrrolidone (PVP), N,N'-methylenebisacrylamide (BIS), and anhydrous ethanol in a volume ratio of 10:60:10 and stir until homogeneous to obtain a PVP solution.

[0022] Step 3: Apply the prepared PVP solution evenly to the cleaned core wire surface using dip coating or spray coating methods;

[0023] Step 4: Cur the coated core wire at a temperature between 40°C and 90°C for 2–4 hours;

[0024] Step 5: Grind and polish the cured coating.

[0025] The application of the hydrophobic coating includes the following steps:

[0026] Step 1: Clean the surface of the shape memory alloy spring with an organic solvent, and remove dirt and oxide layer from the surface of the shape memory alloy spring with sandpaper or wire brush;

[0027] Step 2: Mix PTFE resin, solvent, and titanate coupling agent in a volume ratio of 100:80:30 and stir until homogeneous to obtain PTFE solution; the solvent is a mixture of N,N-dimethylformamide and N-methyl-2-pyrrolidone in a volume ratio of 1:1.

[0028] Step 3: Apply the PTFE solution evenly to the cleaned shape memory alloy spring by spraying.

[0029] Step 4: Allow the sprayed shape memory alloy spring to dry at room temperature, then heat-cure it at 270°C for 1 hour in a high-temperature drying oven;

[0030] Step 5: Grind and polish the memory alloy spring with PEFE coating after curing.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. By setting up a check valve, when the shape memory alloy spring passes through the check valve and eccentrically squeezes the check valve, the buffer ring will deform first before the sealing ring. The shape memory alloy spring drives the sealing ring to move eccentrically, ensuring that the shape memory alloy spring always passes through the sealing ring, so that the check valve has a better sealing effect and effectively prevents leakage during the operation.

[0033] 2. Both the core wire and the shape memory alloy spring are equipped with a low-friction coating. The low-friction coating reduces damage to the patient's tissues and alleviates the patient's pain. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the shape memory alloy spring of the present invention when it is located outside the outer sheath tube;

[0035] Figure 2 This is a schematic diagram of the structure of the present invention when the shape memory alloy spring is located inside the outer sheath tube;

[0036] Figure 3 A schematic diagram of the first type of stop valve;

[0037] Figure 4 A schematic diagram of the transverse cross-sectional structure of the second type of stop valve;

[0038] Figure 5 A schematic diagram of the longitudinal cross-sectional structure of the second type of stop valve;

[0039] Among them: 1-core wire, 2-memory alloy spring, 3-check valve, 4-outer sheath tube, 5-handle, 6-sealing ring, 7-push rod, 8-buffer ring. Detailed Implementation

[0040] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to embodiments. It should be understood that the embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0041] Example 1:

[0042] like Figures 1-5 As shown, a stone-blocking catheter includes a hollow outer sheath 4, the tail end of which is connected to the head end of a handle 5. The handle 5 has a through-hole that passes through both the head and tail ends and communicates with the tail end of the outer sheath 4. The head end of a push rod 7 is located within the through-hole and slides freely within it. The head end of the push rod 7 is connected to the tail end of a core wire 1, and the head end of the core wire 1 is connected to the tail end of a shape memory alloy spring 2. The head end of the core wire 1, along with the shape memory alloy spring 2, can pass through... The handle has a through hole and an outer sheath 4, with the outer sheath 4 protruding from its head. A check valve 3, disc-shaped, is located at the head of the outer sheath 4. The outer ring of the check valve 3 is fixed to the inner wall of the head of the outer sheath 4. A central channel hole is located at the center of the check valve 3, allowing the core wire 1 and the shape memory alloy spring 2 to pass through. The diameter of the central channel hole matches the wire diameter of the core wire 1 and the shape memory alloy spring 2. The core wire 1 is made of nickel-titanium alloy, and the shape memory alloy spring 2 is obtained by laser cutting and heat treatment of nickel-titanium alloy. In this embodiment, the diameter of the core wire 1 and the wire diameter of the shape memory alloy spring 2 are the same.

[0043] The check valve 3 is made of medical-grade silicone. The check valve 3 can effectively prevent fluid from flowing into the outer sheath 4 during surgery, thus avoiding leakage.

[0044] When the push rod 7 moves relative to the handle 5, it can drive the core wire 1 to move. In this embodiment, when the push rod 7 does not move towards the outer sheath 4 in the initial state, the shape memory alloy spring 2 is completely retracted into the outer sheath 4. When the shape memory alloy spring 2 is fully extended from the head end of the outer sheath 4, the shape memory alloy spring 2 returns to its spring shape, and the shape memory alloy spring 2 constitutes the sealing body.

[0045] In some embodiments, after the shape memory alloy spring 2 is fully extended from the head end of the outer sheath tube 4, the shape memory alloy spring 2 returns to its spring shape, and the diameter of the head end of the shape memory alloy spring 2 is smaller than the diameter of the tail end.

[0046] As a preferred embodiment, the check valve 3 includes a concentrically arranged sealing ring 6 and a buffer ring 8. The inner ring of the buffer ring 8 is connected to the outer ring of the sealing ring 6. The diameter of the inner ring of the sealing ring 6 is adapted to the diameter of the core wire 1 and the wire diameter of the shape memory alloy spring 2 (or the inner ring diameter of the sealing ring 6 is smaller than the diameter of the core wire 1 and the wire diameter of the shape memory alloy spring 2). The outer ring of the buffer ring 8 is fixed to the inner wall of the head end of the outer sheath tube 4, and the thickness of the buffer ring 8 is smaller than the thickness of the sealing ring 6. Existing check valves 3 only have perforations on their disc-shaped valve bodies. When the shape memory alloy spring 2 passes through the check valve 3, because the shape memory alloy spring 2 is bent, it will compress the check valve 3. When the compressive force is too large, the perforation deforms, and a gap will be generated between the shape memory alloy spring 2 and the check valve 3, affecting the sealing effect of the check valve 3.

[0047] In some embodiments, the thickness of the buffer ring 8 is less than the thickness of the sealing ring 6. The buffer ring 8 is more prone to deformation under stress than the sealing ring 6. When the shape memory alloy spring 2 passes through the check valve 3 and eccentrically squeezes the check valve 3, the buffer ring 8 will deform preferentially over the sealing ring 6. The shape memory alloy spring 2 drives the sealing ring 6 to move eccentrically, ensuring that the shape memory alloy spring 2 always seals through the sealing ring 6, so that the check valve 3 has a better sealing effect.

[0048] The handle 5 is provided with an anti-slip strip to improve the stability and comfort of operation. In some embodiments, the anti-slip strip is made of silicone material.

[0049] In some embodiments, the core wire 1 is provided with a low-friction coating. The low-friction coating reduces the frictional resistance of the core wire 1 when it moves within human blood vessels or cavities, thereby improving its pushing and maneuverability. It is typically applied to the outer surface of the core wire 1 to reduce friction during its movement within human blood vessels or cavities.

[0050] The low-friction coating material can be either hydrophilic or hydrophobic. Hydrophilic coating materials typically include polyvinylpyrrolidone (PVP), while hydrophobic coating materials typically include polytetrafluoroethylene (PTFE), which also reduces friction. One or more coating materials are usually used, with different coatings applied to different parts of the stone retrieval catheter. In this embodiment, the core wire 1 is coated with a hydrophilic coating—polyvinylpyrrolidone (PVP).

[0051] The shape memory alloy spring 2 is not conventionally coated with a low-friction coating. However, in order to improve the recovery and rebound performance of the shape memory alloy spring 2, in this embodiment, a polytetrafluoroethylene (PTFE) coating is applied to the surface of the shape memory alloy spring 2 to reduce friction, while also giving the shape memory alloy spring 2 good biocompatibility.

[0052] Example 2:

[0053] The present invention also provides a method for preparing the stone-blocking catheter of Embodiment 1 above, comprising the following steps:

[0054] Step 1: Preparation of the outer sheath 4. Medical-grade polypropylene is selected, and the outer sheath 4 is prepared by compression molding to ensure that its inner diameter is suitable for the movement of the core wire 1.

[0055] Material: Medical-grade polypropylene (brand name: PP-RCT) is selected.

[0056] Equipment: Injection molding machine (Model: ENGELVictory).

[0057] Process parameters:

[0058] Barrel temperature: 220-250℃.

[0059] Mold temperature: 50-80℃.

[0060] Injection pressure: 80-140MPa.

[0061] Holding pressure: 30-60MPa.

[0062] Injection speed: Medium, approximately 1.1 m / s.

[0063] Cooldown time: 20-30 seconds.

[0064] The dimensions of the prepared outer sheath tube are: outer diameter (2-3) mm, inner diameter (1.6-2.4) mm, and length (260-340) mm.

[0065] Step 2: Preparation of core wire 1. Select a suitable metal material, such as copper-zinc alloy, nickel-titanium alloy, or iron-platinum alloy, and make core wire 1 by drawing process. Its outer diameter is smaller than the inner diameter of outer sheath tube 4.

[0066] Materials: The typical representative material selected in this example is nickel-titanium alloy (grade: Nitinol).

[0067] Equipment: Drawing machine.

[0068] Process parameters:

[0069] Drawing temperature: 600-800℃.

[0070] Pulling speed: 10-20m / min.

[0071] Annealing temperature: 450-500℃.

[0072] Annealing time: 30-60 minutes.

[0073] The specifications of the prepared core wire are: outer diameter (0.8-1.2) mm and length (290-370) mm (slightly longer than the outer sheath).

[0074] Step 3: Fabrication of the shape memory alloy spring 2. Using the core wire 1 obtained in Step 2, the shape memory alloy spring 2 is fabricated through laser cutting and heat treatment to ensure its shape memory properties at body temperature. Laser cutting ensures the shape and dimensions of the shape memory alloy spring 2. Heat treatment is performed immediately after laser cutting to reduce the adverse effects of the heat-affected zone and optimize the shape memory properties of the shape memory alloy spring 2.

[0075] Material: Nickel-titanium alloy (grade: Nitinol).

[0076] Equipment: Laser cutting machine (Model: TRUMPF).

[0077] Process parameters:

[0078] Laser power: 100W.

[0079] Cutting speed: 5mm / s.

[0080] Heat treatment temperature: 500℃.

[0081] Heat treatment time: 60 minutes.

[0082] Memory alloy spring 2 specifications: outer diameter (0.8~1.2)mm, length (45~55)mm.

[0083] Step 4: Fabrication of the handle 5 and push rod 7. Medical-grade plastic material is used to manufacture the handle 5 and push rod 7 through injection molding, ensuring structural stability and ease of operation.

[0084] Material: Medical-grade plastic, namely polyetheretherketone (brand name: PEEK).

[0085] Equipment: Injection molding machine (Model: ENGEL Victory).

[0086] Process parameters:

[0087] Barrel temperature: 220-250℃.

[0088] Mold temperature: 50-80℃.

[0089] Injection pressure: 80-140MPa.

[0090] Holding pressure: 30-60MPa.

[0091] Injection speed: Medium speed.

[0092] Cooldown time: 20-30 seconds.

[0093] Specifications of handle 5 and push rod 7: handle length (80~120)mm, push rod diameter (1.3~1.7)mm, length (110~130)mm.

[0094] Step 5: Preparation of check valve 3. Medical-grade silicone was selected as the material due to its excellent biocompatibility and flexibility. LSR (liquid silicone) series was chosen.

[0095] Equipment: Check valve 3 is produced by injection molding of industrial silicone using a high-precision injection molding machine. The injection molding machine model is WITTMANN Group series.

[0096] Processing parameters: Injection molding temperature: generally 150-200℃.

[0097] The check valve 3 and the outer sheath 4 are sized compatible. The check valve 3 is nested inside the outer sheath 4. The outer diameter of the check valve 3 matches the inner diameter of the outer sheath 4, and the diameter of the central channel hole of the check valve 3 matches the diameter of the core wire. The outer diameter of the check valve is fixed to the beginning of the outer sheath.

[0098] Step 6: Apply a low-friction coating to the core wire 1 and the shape memory alloy spring 2;

[0099] The coating process for polytetrafluoroethylene (PTFE) is as follows:

[0100] 1. Pretreatment: Clean the substrate (shape memory alloy spring) with organic solvents such as acetone or ethanol, then use sandpaper or a wire brush to remove surface dirt and oxide layers. This ensures adhesion between the coating and the substrate.

[0101] 2. Preparation of coating solution: Based on specific application requirements and coating performance needs, polytetrafluoroethylene (PTFE) (3M...) is prepared... TM Dyneon TM A PTFE coating solution is prepared by mixing PTFE TF 5070GZ with a solvent (a mixture of N,N-dimethylformamide and N-methyl-2-pyrrolidone in a volume ratio of 1:1) and an additive (titanium ester coupling agent NDZ-311W) in a volume ratio of 100:80:30.

[0102] 3. Coating: Apply the PTFE coating solution evenly to the pretreated substrate surface by spraying.

[0103] 4. Drying and curing: Allow the sprayed substrate to dry at room temperature first, then heat-cure it at 270°C for 1 hour in a high-temperature drying oven.

[0104] 5. Post-treatment: After the coating has cured, the substrate undergoes some post-treatment steps, such as sanding, polishing, and spraying primer, to further improve the appearance and performance of the coating.

[0105] The coating process for polyvinylpyrrolidone (PVP) is as follows:

[0106] 1. Surface pretreatment: Clean the surface of the substrate (core wire) to remove grease and impurities. Ultrasonic cleaning can be performed using solvents such as ethanol and isopropanol.

[0107] 2. Preparation of coating solution:

[0108] Selection of polyvinylpyrrolidone (PVP): PVP K30 (molecular weight approximately 400,000) is typically used.

[0109] Solvents: Commonly used solvents include ethanol, isopropanol, etc. Choosing the appropriate concentration can better control the adhesion and smoothness of the prepared coating.

[0110] Crosslinking agent: N,N'-methylenebisacrylamide (BIS)

[0111] Formulation: Polyvinylpyrrolidone (PVP), crosslinking agent, and anhydrous ethanol are mixed in a volume ratio of 10:60:10 to form a homogeneous solution at room temperature. The specific formulation ratio may need to be adjusted according to the actual application and performance requirements to obtain the PVP solution.

[0112] 3. Coating: The prepared PVP solution is uniformly coated onto the pretreated substrate surface. Coating methods include dip coating and spray coating.

[0113] 4. Curing: Cure the coated substrate at a temperature between 40°C and 90°C for 2 to 4 hours to form a stable coating.

[0114] 5. Post-treatment: The substrate with the cured coating undergoes post-treatment, such as grinding and polishing, to improve the surface quality and performance of the coating.

[0115] Step 7: Assembly of components.

[0116] 1. Check valve 3 is welded and installed; the outer ring of check valve 3 is connected to the inner wall of the head end of the outer sheath tube 4 by fusion welding.

[0117] The fusion welding equipment uses a high-frequency welding machine or an ultrasonic welding machine.

[0118] Melting welding temperature: usually slightly higher than the melting point of silicone material, approximately 180-220℃.

[0119] Pressure: 150MPa~190MPa, ensuring sufficient pressure to ensure a tight connection between the check valve and the outer sheath.

[0120] 2. Assembly of the outer sheath tube 4 and the core wire 1;

[0121] Insert the end of the core wire 1 from the beginning of the outer sheath 4, extend it into the check valve 3 and pass through the end of the outer sheath 4, ensuring that the shape memory alloy spring 2 is inside the outer sheath 4.

[0122] 3. Installation of handle 5 and push rod 7;

[0123] Fix the tail end of the outer sheath tube 4 to the head end of the handle 5 together, which can be done by gluing; then fix the tail end of the core wire 1 to the head end of the push rod 7, and put the push rod 7 into the handle through hole of the handle 5.

[0124] 4. Installation of anti-slip strips:

[0125] Wrap a non-slip strip around handle 5 to improve stability and comfort during operation.

[0126] During the procedure, the doctor first inserts the outer sheath 4 into the patient's body. Using the push rod 7, the doctor controls the movement of the core wire 1, causing the shape memory alloy spring 2 to extend from the tip of the outer sheath 4 and form a suffocation at the target location. After lithotripsy, the doctor simultaneously controls the handle 5 and the push rod 7 to remove the stone.

[0127] To demonstrate the effectiveness of this invention, a clinical trial was conducted, comparing this invention with a traditional catheter as comparative subjects. The following are some key clinical trial results and comparative data: the target number of participants was 20.

[0128] 1. Operation time

[0129] The average operation time of this invention is (35.2±9.5) minutes.

[0130] Traditional catheter: The average operation time was (54.7±14.4) minutes.

[0131] 2. Single-use stone removal rate

[0132] This invention achieves a 95.4% stone removal rate in a single treatment.

[0133] Traditional catheters: 79.6% stone removal rate in a single procedure.

[0134] 3. Postoperative bleeding

[0135] The average postoperative blood loss was (23±6.7) ml.

[0136] Traditional catheter: The average postoperative blood loss was (25±7.1) ml.

[0137] 4. Postoperative fever

[0138] The incidence of postoperative fever was 4 cases in this invention.

[0139] Traditional catheterization: The incidence of postoperative fever was 6 cases.

[0140] 5. Duration of hospital stay

[0141] The average length of hospital stay in this invention is 4.5 days.

[0142] Traditional catheterization: The average hospital stay is 8.6 days.

[0143] 6. Surgical success rate

[0144] This invention boasts a surgical success rate of 97.3%.

[0145] Traditional catheter: The success rate of the procedure is 68.5%.

[0146] Based on the above data, this invention demonstrates significant advantages in clinical trials. Compared to traditional catheters, the novel catheter significantly improves surgical efficiency, reduces patient discomfort, and possesses greater clinical application value and promising prospects for wider adoption.

[0147] All parts not covered in this invention are the same as or can be implemented using existing technologies.

[0148] It should be noted that the embodiments described in this invention are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains can make various modifications or additions to the described embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A stone-blocking catheter, comprising a hollow outer sheath (4), characterized in that, The tail end of the outer sheath (4) is connected to the head end of the handle (5). The handle (5) is provided with a handle through hole that passes through the head and tail ends of the handle (5) and is connected to the tail end of the outer sheath (4). The head end of the push rod (7) is located in the handle through hole. The push rod (7) slides freely in the handle through hole. The head end of the push rod (7) is connected to the tail end of the core wire (1). The head end of the core wire (1) is connected to the tail end of the memory alloy spring (2). The head end of the core wire (1) is connected to the tail end of the shape memory alloy spring (2). The shape memory alloy spring (2) passes through the handle through hole and the outer sheath (4) in sequence and protrudes from the first end of the outer sheath (4). The first end of the outer sheath (4) is provided with a check valve (3). The outer ring side of the check valve (3) is fixed to the inner wall of the first end of the outer sheath (4). The center of the check valve (3) is provided with a central channel hole for the core wire (1) and the shape memory alloy spring (2) to pass through. The diameter of the central channel hole is adapted to the wire diameter of the core wire (1) and the shape memory alloy spring (2). The check valve (3) includes a sealing ring (6) and a buffer ring (8) arranged concentrically. The inner side of the buffer ring (8) is connected to the outer side of the sealing ring (6). The outer side of the buffer ring (8) is fixed to the inner wall of the outer sheath (4). The thickness of the buffer ring (8) is less than the thickness of the sealing ring (6). The buffer ring (8) is more likely to deform under stress than the sealing ring (6). The core wire (1) is provided with a hydrophilic coating, and the memory alloy spring (2) is provided with a hydrophobic coating.

2. The stone-blocking catheter according to claim 1, characterized in that, The diameter of the core wire (1) is the same as that of the shape memory alloy spring (2).

3. The stone-blocking catheter according to claim 1, characterized in that, After the shape memory alloy spring (2) is fully extended from the head end of the outer sheath (4), the diameter of the head end of the shape memory alloy spring (2) is smaller than the diameter of the tail end.

4. The stone-blocking catheter according to claim 3, characterized in that, When the push rod (7) does not move toward the outer sheath (4) in the initial state, the memory alloy spring (2) is completely retracted into the outer sheath (4).

5. A stone-blocking catheter according to claim 4, characterized in that, The hydrophilic coating is polyvinylpyrrolidone (PVP), and the hydrophobic coating is polytetrafluoroethylene (PTFE).

6. A method for preparing the stone-blocking catheter as described in claim 5, characterized in that, Includes the following steps: Step 1: Select medical-grade polypropylene to prepare the outer sheath tube (4) through compression molding process. Step 2: Select nickel-titanium alloy and use a drawing process to make core wire (1). Step 3: The core wire (1) obtained in step 2 is laser-cut into a spring shape and the spring is immediately heat-treated to obtain a shape memory alloy spring (2); Step 4: Use medical-grade plastic to make a handle (5) and a push rod (7) through injection molding. Step 5: Use medical-grade silicone to manufacture a check valve (3) through injection molding. Step 6: Apply a hydrophilic coating to the core wire (1) and a hydrophobic coating to the shape memory alloy spring (2); Step 7: Weld the outside of the check valve (3) to the inner wall of the first end of the outer sheath (4), insert the tail end of the core wire (1) from the first end of the outer sheath (4), extend it through the check valve (3) and out from the tail end of the outer sheath (4), ensure that the memory alloy spring (2) on the core wire (1) is located inside the outer sheath (4), fix the tail end of the outer sheath (4) to the first end of the handle (5), fix the tail end of the core wire (1) to the first end of the push rod (7), and put the push rod (7) into the handle through hole of the handle (5). Finally, wrap the anti-slip strip around the handle (5).

7. The method for preparing a stone-blocking catheter according to claim 6, characterized in that, The application of the hydrophilic coating includes the following steps: Step 1: Use ethanol or isopropanol solvent to ultrasonically clean the core wire (1); Step 2: Mix polyvinylpyrrolidone (PVP), N,N'-methylenebisacrylamide (BIS), and anhydrous ethanol in a volume ratio of 10:60:10 and stir until homogeneous to obtain a uniform solution, which is the PVP solution. Step 3: Apply the prepared PVP solution evenly to the cleaned core wire (1) surface using dip coating or spray coating methods; Step 4: Cur the coated core wire (1) at a temperature between 40°C and 90°C for 2-4 hours; Step 5: Grind and polish the core wire (1) with the cured coating.

8. The method for preparing a stone-blocking catheter according to claim 6, characterized in that, The application of the hydrophobic coating includes the following steps: Step 1: Clean the surface of the memory alloy spring (2) with an organic solvent, and remove the dirt and oxide layer from the surface of the memory alloy spring (2) with sandpaper or wire brush; Step 2: Mix PTFE resin, solvent, and titanate coupling agent in a volume ratio of 100:80:30 and stir until homogeneous to obtain PTFE solution; the solvent is a mixture of N,N-dimethylformamide and N-methyl-2-pyrrolidone in a volume ratio of 1:

1. Step 3: Apply the PTFE solution evenly to the cleaned shape memory alloy spring (2) by spraying. Step 4: Place the sprayed memory alloy spring (2) at room temperature to dry, and then heat-cure it at 270°C for 1 hour in a high-temperature drying oven; Step 5: Grind and polish the shape memory alloy spring (2) with the PEFE coating.

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