A gastrointestinal tube and a method of making the same

Abstract

The present application belongs to the technical field of medical manufacturing, and particularly relates to a gastrointestinal integrated tube and a preparation method thereof. The tube body comprises a gastric tube segment and an intestinal tube segment. The gastric tube segment is of a single-cavity structure, and the intestinal tube segment is of a three-cavity structure. The preparation method comprises the following steps: (1) raw material preparation: mixing a polyurethane base material with an antistatic agent and an antibacterial agent; (2) gradient extrusion molding: feeding the functionalized polyurethane raw material into a double-screw extruder, and realizing the molding of the tube body of the integrated tube by means of a multi-stage hydraulic die; (3) dynamic cavity number regulation: in the extrusion process, the core mold switching system is controlled by a mechanical arm; and (4) post-processing: water cooling and sizing and surface coating treatment are performed on the tube body of the integrated tube. The core mold of the present application can quickly switch and adjust the cavity number, meet different clinical functional requirements, improve the functional expandability and operation convenience, and has high product size precision and good mechanical properties, can withstand external force and is durable, and at the same time has good antistatic, antibacterial, lubricating and biocompatibility, and is particularly suitable for fine treatment scenes such as pediatrics.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of medical manufacturing, and particularly relates to a gastrointestinal integrated tube and a preparation method thereof. BACKGROUND

[0002] In the field of medical devices, polyurethane gastrointestinal integrated tubes, as commonly used devices in the treatment of gastrointestinal diseases and the process of nutritional support, are widely used in gastrointestinal drainage, drug delivery and nutritional delivery. However, the current traditional polyurethane gastrointestinal integrated tube and its preparation method have many problems to be solved.

[0003] The physiological structure of the human gastrointestinal tract varies significantly from individual to individual due to factors such as age, body size, and illness. For example, the gastrointestinal tract of children is more delicate than that of adults, and requires a smaller and more accurate tube diameter. In actual use, if the tube diameter of a fixed-diameter gastrointestinal integrated tube is too large, it may cause damage to the mucosa of the patient's gastrointestinal tract during insertion, increasing the patient's pain and possibly causing complications such as inflammation. If the tube diameter is too small, it cannot guarantee sufficient drainage, drug delivery, or nutritional delivery flow, seriously affecting the treatment effect. The tube diameter of the existing polyurethane gastrointestinal integrated tube is usually fixed and cannot meet the diverse needs of different patients.

[0004] The lumen number of the gastrointestinal integrated tube on the market is mostly fixed. In actual medical treatment, multiple operations often need to be performed simultaneously, such as for some gastrointestinal diseases, gastric juice drainage, drug infusion, and nutritional material delivery may need to be performed simultaneously. A single-lumen tube obviously cannot achieve the simultaneous performance of these functions. Even some multi-lumen tubes, the number of lumens is pre-set and cannot be changed, and cannot be flexibly adjusted according to the actual situation during treatment. For example, in the intensive care unit, for patients with complex and variable conditions, a single-lumen tube may only be needed for simple drainage at the initial stage of treatment, but as the condition develops, the number of lumens may need to be increased to achieve multiple functions. The fixed-lumen gastrointestinal integrated tube cannot meet the needs of such dynamic changes, limiting its effectiveness and adaptability in clinical applications.

[0005] The traditional preparation process of polyurethane gastrointestinal integrated tube mainly relies on fixed mold. Once the mold is determined, the diameter and the number of cavities of the produced gastrointestinal tube are fixed. If different diameter or number of cavities products are to be produced, the entire set of mold must be replaced, which not only greatly increases the production cost and prolongs the production cycle, but also cannot realize the change of diameter and the number of cavities on the same tube. Taking the extrusion molding process as an example, the polyurethane material is extruded through the fixed mold to form the tube. If the tube diameter is to be changed, the mold with different diameter needs to be replaced. Each time the mold is replaced, debugging and calibration need to be carried out, which consumes a lot of manpower, material resources and time. The method of changing the diameter of the gastrointestinal tube by secondary processing often causes damage to the original structure of the tube, resulting in uneven wall thickness of the tube. For example, when the formed gastrointestinal tube is subjected to mechanical expanding or reducing treatment, the tube wall is easily locally thinned or thickened, thereby affecting the strength and flexibility of the tube. In the use process, the tube with uneven wall thickness may be broken or twisted and deformed, thereby reducing the reliability and safety of the product. The change of the number of cavities by secondary processing is more difficult, it is difficult to accurately form multiple uniform, independent and functional cavities on the tube, and it may also cause liquid leakage between the cavities, so that the liquids with different functions interfere with each other, which seriously affects the normal use of the gastrointestinal tube.

[0006] In summary, the existing polyurethane gastrointestinal integrated tube and its preparation process have many drawbacks and cannot meet the increasingly complex and diversified clinical needs. It is of great clinical significance and market demand to develop a new preparation method which can realize variable diameter and variable number of cavities and ensure stable and reliable performance of the tube. SUMMARY

[0007] The purpose of the present application is to provide a gastrointestinal integrated tube and a preparation method thereof.

[0008] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0009] A gastrointestinal integrated tube, the outer diameter of the gastric tube segment is 8mm, the gastric tube segment has a single cavity structure, the outer diameter of the intestinal tube segment is 4mm, the intestinal tube segment has a three-cavity structure, and the outer diameter of the tube body and the number of cavities are transitioned through a gradual change segment with a length ratio of ≥60%; the wall thickness of the gradual change segment linearly decreases from 1.0mm±0.1mm to 0.5mm±0.1mm, and the wall thickness gradient change rate is ≤0.1mm / cm; the three cavities include a drainage cavity, a drug delivery cavity and a nutrition cavity, and the cross-sectional area ratio of the three cavities is drainage cavity:drug delivery cavity:nutrition cavity=1:(0.6-0.8):(1.2-1.5), and the cavity wall thickness is 0.3mm±0.05mm; the dynamic friction coefficient of the tube body surface is ≤0.1.

[0010] Further, the tube surface of the gradual change section is provided with a spiral micro-protrusion structure, the protrusion height is 50 μm-100 μm, the spiral pitch is 1 mm-2 mm, the micro-protrusion surface is covered with a heparin-silicone oil composite coating, and the coating thickness is 10%-15% of the protrusion height.

[0011] Further, the spiral angle of the spiral micro-protrusion is 30°-45°, and the spiral direction is consistent with the axial stretching direction of the tube body of the integrated tube.

[0012] A preparation method of a gastrointestinal integrated tube, comprising the following steps:

[0013] (1) Raw material preparation: mixing polyurethane base material with antistatic agent and antibacterial agent; wherein the antistatic agent accounts for 0.5%-3% of the total weight of the functionalized polyurethane raw material, and the antibacterial agent accounts for 1%-3% of the total weight of the functionalized polyurethane raw material; mixing at a stirring speed of 1200 rpm-1800 rpm and a temperature of 25°C-40°C for not less than 30 minutes to obtain a functionalized polyurethane raw material;

[0014] (2) Gradient extrusion molding: putting the functionalized polyurethane raw material obtained in step (1) into a double screw extruder, and realizing the molding of the tube body of the integrated tube by means of a multi-section hydraulic die, wherein the multi-section hydraulic die adjusts the inner diameter in real time, so that the diameter of the tube body of the integrated tube can be continuously changed from 8 mm to 4 mm, and a transition section with a taper angle in the range of 15°-30° is arranged between adjacent hydraulic die sections, and the length of the transition section is 1.5 times-3 times the diameter variation of the tube body of the integrated tube;

[0015] (3) Dynamic cavity number control: during the extrusion process, the core mold switching system is controlled by a mechanical arm, so that the switching operation of single-cavity, double-cavity, triple-cavity or four-cavity core mold can be completed within 0.5 seconds according to the diameter variation of the tube body of the integrated tube, and the cavity spacing tolerance is ≤0.1 mm after the switching is completed;

[0016] (4) Post-processing: water cooling and surface coating treatment are performed on the tube body of the integrated tube, the water cooling process is gradient cooling from 25°C to 10°C at a rate of 2°C / min, the surface coating adopts a heparin-silicone oil composite layer applied by plasma spraying technology, the spraying pressure is 0.2 MPa-0.5 MPa, and the coating thickness is 5 μm-15 μm.

[0017] Further, the antistatic agent in step (1) is a quaternary ammonium salt compound, and the antibacterial agent is a silver ion nanoparticle coated with polyethylene glycol, and the particle size is 20 nm-50 nm.

[0018] Further, the core mold switching system rule in step (3) is that when the integrated tube body diameter is greater than or equal to 6 mm, it is switched to single cavity, when the integrated tube body diameter is 4 mm to 6 mm, it is switched to double cavity or triple cavity, and when the integrated tube body diameter is less than or equal to 4 mm, it is switched to triple cavity or quadruple cavity; the cavity cross section is an oval shape, and the ratio of the long axis to the short axis is 1.2:1 to 1.5:1.

[0019] Further, in the water cooling shaping process in step (4), the cooling water circulation flow rate is 10 L / min to 15 L / min, and the ratio of the axial stretching rate of the integrated tube body to the cooling rate is 1: (0.8-1.2), and when the ratio is 1:1, the axial shrinkage rate of the tube body is less than or equal to 2%.

[0020] Further, the gradual change rate of the cavity number switching is 0.8 cavities / mm to 1.2 cavities / mm, and is synchronized with the change rate of the integrated tube body diameter.

[0021] The beneficial effects of the present application are:

[0022] (1) Material performance improvement: by adding specific antistatic agents and antibacterial agents to the polyurethane base material and optimizing the mixing conditions, the tube body is given stable antistatic and efficient antibacterial properties, enhancing hygiene safety and durability.

[0023] (2) Strong structural adaptability: the multi-section hydraulic mold realizes smooth and gradual change of the tube diameter, avoids structural defects, and better adapts to the physiological structure of the gastrointestinal tract; the core mold quickly switches to adjust the number of cavities, accurately meets different clinical functional requirements, and improves functional expandability and operation convenience.

[0024] (3) Good post-processing effect: gradient water cooling shaping eliminates internal stress, improves physical properties and dimensional stability; heparin-silicone oil composite coating is sprayed by plasma, which enhances lubricity and biocompatibility, reduces insertion damage and rejection reaction.

[0025] (4) Excellent product performance: the product has high size precision and good mechanical properties, can withstand external force and is durable, and also has good antistatic, antibacterial, lubricating and biocompatibility, especially suitable for pediatric and other delicate treatment scenarios, providing high-quality treatment solutions. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A schematic view of a gastrointestinal integrated tube structure. DETAILED DESCRIPTION

[0027] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely; obviously, the described embodiments are only a part of the embodiments of the present application, and not all the embodiments; based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application. Embodiment one

[0028] (I) Preparation of raw materials

[0029] 1. Select polyurethane base material as the basic material. The antistatic agent is selected to be hexadecyl trimethyl ammonium bromide, accounting for 3% of the total weight of the functionalized polyurethane raw material. The antibacterial agent is a silver ion nanoparticle coated with polyethylene glycol, with a particle size of 30 nm, accounting for 2% of the total weight of the functionalized polyurethane raw material.

[0030] 2. Put the polyurethane base material, antistatic agent and antibacterial agent into a stirring device, mix at a stirring speed of 1500 rpm at a temperature of 30°C for 40 minutes, and fully mix to obtain the functionalized polyurethane raw material, ensuring that each component is uniformly dispersed.

[0031] (II) Gradient extrusion molding

[0032] 1. Put the prepared functionalized polyurethane raw material into a double screw extruder. An integrated tube body is formed by means of a multi-stage hydraulic die, which adjusts the inner diameter in real time, so that the diameter of the integrated tube body continuously changes from 8 mm to 4 mm.

[0033] 2. A transition section with a taper angle of 25° is provided between adjacent hydraulic die sections, and the length of the transition section is 8 mm.

[0034] (III) Dynamic cavity number control

[0035] 1. During the extrusion process, the core mold switching system is controlled by a mechanical arm. The core mold switching system rule is: when the diameter of the integrated tube body is ≥6 mm, switch to single cavity; when the diameter of the tube body is 4-6 mm, switch to three cavities; the gradual change rate of the cavity number is 1.0 cavity / mm, and it is synchronized with the change rate of the diameter of the integrated tube body, and the core mold switching operation can be completed within 0.5 seconds, and the cavity spacing tolerance after switching is 0.08 mm.

[0036] 2. The cross section of the cavity is an oval shape, and the ratio of the long axis to the short axis is 1.3:1.

[0037] (IV) Post-processing

[0038] 1. Water-cooling shaping of the integrated tube body, the water-cooling process is gradiently cooled from 25℃ to 10℃ at a rate of 2℃ / min. The circulation flow rate of the cooling water is set to 12 L / min, the ratio of the axial stretching rate of the integrated tube body to the cooling rate is 1:1, and the axial shrinkage rate of the tube body under this condition is 1.8%.

[0039] 2. Surface coating treatment: a heparin-silicone oil composite layer is applied to the surface coating by plasma spraying technology, the spraying pressure is 0.3 MPa, and the coating thickness is 12 μm. The surface of the tube body of the gradual change section is provided with a spiral micro-protrusion structure, the protrusion height is 80 μm, the spiral pitch is 1.5 mm, the micro-protrusion surface is covered with a heparin-silicone oil composite coating, and the coating thickness is 15% of the protrusion height. The spiral angle of the spiral micro-protrusion is 40°, and the spiral direction is consistent with the axial stretching direction of the integrated tube body.

[0040] (Five) Performance index

[0041] 1. Dynamic friction coefficient: the dynamic friction coefficient is 0.08 measured by the standard test method of ASTM D1894, indicating that the surface of the tube body is extremely smooth and has small friction to the tissue when moving in the body.

[0042] 2. Antibacterial rate: the standard antibacterial test method is used, and the antibacterial rate of 24 hours to Escherichia coli is 99.3%, effectively inhibiting the growth of bacteria and reducing the risk of infection.

[0043] 3. Tensile strength: the gradual change section tensile strength is 28 MPa measured by using a material tensile testing machine, indicating that the tube body has high strength at the diameter gradual change part and is not easy to break.

[0044] 4. Drainage flow rate: the intestinal tube section drainage flow rate is 82 mL / min measured by simulating the clinical drainage scene, which can meet the normal drainage demand.

[0045] 5. Lumen spacing tolerance: the lumen spacing tolerance is 0.08 mm detected by high-precision measuring instruments, which ensures the positional accuracy between the lumens and is beneficial to the normal realization of each function. Example two

[0046] (I) Raw material preparation

[0047] 1. The antistatic agent is selected as dodecyl dimethyl benzyl ammonium chloride, accounting for 0.5% of the total weight of the functionalized polyurethane raw material, and the antibacterial agent is still the silver ion nanoparticles coated with polyethylene glycol, with a particle size of 30 nm and an accounting ratio of 2%.

[0048] 2. The functionalized polyurethane raw material is prepared by mixing at a stirring speed of 1200 rpm at 25℃ for 30 minutes.

[0049] (II) Gradient extrusion molding

[0050] 1. The multi-stage hydraulic mold continuously and gradually changes the diameter of the integrated tube body from 8 mm to 4 mm.

[0051] 2. The transition section between adjacent hydraulic mold sections has a 15° taper angle, and the length of the transition section is 12 mm.

[0052] (Three) Dynamic cavity number control

[0053] 1. The core mold switching system is the same as in Example 1, the cavity number switching gradient is 0.8 cavities / mm, synchronized with the tube body diameter change rate, and the switching is completed within 0.5 seconds, with a cavity spacing tolerance of ≤0.1 mm.

[0054] 2. The cavity cross-section is an oval shape, with a long axis to short axis ratio of 1.2:1.

[0055] (Four) Post-processing

[0056] 1. Water cooling and shaping: cooling from 25°C to 10°C at a rate of 2°C / min, cooling water circulation flow rate is 10 L / min, the ratio of tube body axial stretching rate to cooling rate is 1:0.8, and the tube body axial shrinkage rate is 2.1%.

[0057] 2. Surface coating treatment: plasma spraying of heparin-silicone oil composite layer, spraying pressure 0.2 MPa, coating thickness 5 μm. The tube body surface of the gradual change section has a spiral micro-protrusion structure with a protrusion height of 50 μm, a spiral pitch of 1 mm, a micro-protrusion surface coating thickness of 10% of the protrusion height, a spiral angle of 30°, and a spiral direction consistent with the axial stretching direction.

[0058] (Five) Performance indicators

[0059] 1. Dynamic friction coefficient: 0.09, the surface still maintains good lubricity.

[0060] 2. Antibacterial rate: 98.5%, good antibacterial performance.

[0061] 3. Tensile strength: 25 MPa, meeting the tube body strength requirements.

[0062] 4. Drainage flow rate: 78 mL / min, meeting the basic drainage function.

[0063] Comparative Example 1

[0064] (I) Raw material preparation

[0065] 1. The antistatic agent is tetrabutylammonium bromide, a quaternary ammonium salt compound, accounting for 4% of the total weight of the functionalized polyurethane raw material, and no antibacterial agent is added.

[0066] 2. Mix at a stirring speed of 1800 rpm for 30 minutes at 40°C.

[0067] (ii) Gradient extrusion molding

[0068] The same as example 1, the multi-stage hydraulic die makes the integrated tube body diameter continuously and gradually change from 8 mm to 4 mm, the transition section angle between adjacent hydraulic die sections is 25°, and the length is 8 mm.

[0069] (iii) Dynamic cavity number control

[0070] The same as example 1, the core mold switching system is regular, the cavity number switching gradient rate is 1.0 cavity / mm, the switching is completed within 0.5 seconds, the cavity spacing tolerance is 0.08 mm, and the cavity cross section is oval-shaped with a long axis to short axis ratio of 1.3:1.

[0071] (iv) Post-processing

[0072] The same as example 1, the water cooling shaping is cooled from 25°C to 10°C at a rate of 2°C / min, the cooling water circulation flow rate is 12 L / min, the ratio of the axial stretching rate of the integrated tube body to the cooling rate is 1:1, and the surface coating treatment parameters are the same.

[0073] (v) Performance indicators

[0074] 1. Dynamic friction coefficient: 0.15, due to the over-range of the antistatic agent, leading to the adsorption of particles by static electricity, causing the friction coefficient to rise.

[0075] 2. Antibacterial rate: 72.0%, due to the absence of an antibacterial agent, the antibacterial performance is greatly reduced.

[0076] 3. Tensile strength: 22 MPa, which is lower than that of example 1.

[0077] 4. Drainage flow rate: 50 mL / min, the drainage function is affected.

[0078] Comparative example 2

[0079] (i) Raw material preparation

[0080] The same as example 1, the antistatic agent hexadecyl trimethyl ammonium bromide accounts for 3%, and the antibacterial agent silver ion nanoparticles (particle size 30 nm) coated with polyethylene glycol accounts for 2%, and the mixing is carried out at a stirring speed of 1500 rpm at 30°C for 40 minutes.

[0081] (ii) Gradient extrusion molding

[0082] 1. The multi-stage hydraulic die makes the integrated tube body diameter continuously and gradually change from 8 mm to 4 mm.

[0083] 2. The transition section angle between adjacent hydraulic die sections is 40°, and the length is 4 mm.

[0084] (iii) Dynamic cavity number control

[0085] The number of unsynchronized switching cavities, single cavity throughout.

[0086] (4) Post-processing

[0087] The same as example 1, the water cooling setting and surface coating treatment parameters are consistent.

[0088] (5) Performance index

[0089] 1. Dynamic friction coefficient: 0.12, slightly higher than example 1.

[0090] 2. Antibacterial rate: 97.0%, the antibacterial performance is less affected.

[0091] 3. Tensile strength: 18 MPa, cracks appear due to the excessively large transition section cone angle, and the strength decreases.

[0092] 4. Drainage flow rate: 45 mL / min, the drainage efficiency is low.

[0093] The performance indexes of the examples and the comparative examples are shown in table 1.

[0094] Table 1

[0095]

[0096] The above description is only the preferred specific implementation of the present application; however, the protection scope of the present application is not limited to this. Any skilled person in the art, according to the technical solution and the improved concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method of producing a gastrointestinal unit, characterized by, The method comprises the following steps: (1) raw material preparation: mixing polyurethane base material with antistatic agent and antibacterial agent; wherein the antistatic agent accounts for 0.5%-3% of the total weight of the functionalized polyurethane raw material, and the antibacterial agent accounts for 1%-3% of the total weight of the functionalized polyurethane raw material; the functionalized polyurethane raw material is prepared by mixing at a stirring speed of 1200 rpm-1800 rpm and a temperature of 25℃-40℃ for not less than 30 minutes; (2) gradient extrusion molding: the functionalized polyurethane raw material obtained in step (1) is put into a double screw extruder, and the molding of the integrated tube body is realized by means of a multi-stage hydraulic die; the multi-stage hydraulic die adjusts the inner diameter in real time, so that the diameter of the integrated tube body can be continuously changed from 8 mm to 4 mm; a transition section with a taper angle in the range of 15°-30° is arranged between adjacent hydraulic die sections, and the length of the transition section is 1.5 times-3 times the diameter variation of the integrated tube body; (3) dynamic cavity number control: during the extrusion process, the core mold switching system is controlled by a mechanical arm to complete the switching operation of single-cavity, double-cavity, triple-cavity or four-cavity core molds within 0.5 seconds according to the diameter variation of the integrated tube body; after the switching is completed, the cavity spacing tolerance is ≤0.1 mm; (4) post-processing: the integrated tube body is subjected to water cooling and surface coating treatment; the water cooling process is gradient cooling from 25℃ to 10℃ at a rate of 2℃ / min; the surface coating adopts plasma spraying technology to apply a heparin-silicone oil composite layer; the spraying pressure is 0.2MPa-0.5MPa, and the coating thickness is 5μm-15μm. The core mold switching system rule in step (3) is: when the diameter of the integrated tube body is ≥6mm, switch to single-cavity; when the diameter of the integrated tube body is 4mm-6mm, switch to double-cavity or triple-cavity; when the diameter of the integrated tube body is ≤4mm, switch to triple-cavity or four-cavity; the cavity cross section is oval, and the ratio of the long axis to the short axis is 1.2:1-1.5:

1. The prepared gastrointestinal integrated tube comprises a gastric tube segment and an intestinal tube segment; the gastric tube segment has a single-cavity structure with an outer diameter of 8mm; the intestinal tube segment has a triple-cavity structure with an outer diameter of 4mm; the tube body outer diameter and the number of cavities are transitioned through a gradual change section with a length ratio ≥60%; the gradual change section wall thickness linearly decreases from 1.0mm±0.1mm to 0.5mm±0.1mm, and the wall thickness gradient change rate is ≤0.1mm / cm; the triple-cavity includes a drainage cavity, a drug delivery cavity and a nutrition cavity; the triple-cavity cross-sectional area ratio is drainage cavity: drug delivery cavity: nutrition cavity = 1:(0.6-0.8):(1.2-1.5), and the cavity wall thickness is 0.3mm±0.05mm; the tube body surface dynamic friction coefficient is ≤0.

1.

2. The method for preparing an integrated gastrointestinal tube according to claim 1, characterized in that: The tube body surface of the gradual change section is provided with a spiral micro-protrusion structure; the protrusion height is 50μm-100μm, and the spiral pitch is 1mm-2mm; the micro-protrusion surface is covered with a heparin-silicone oil composite coating; the coating thickness is 10%-15% of the protrusion height.

3. The method for preparing an integrated gastrointestinal tube according to claim 2, characterized in that: The spiral angle of the spiral micro-protrusion is 30°-45°, and the spiral direction is consistent with the axial stretching direction of the integrated tube body.

4. The method of claim 1, wherein the gastroenteral unit is prepared by the steps of: The antistatic agent in step (1) is a quaternary ammonium salt compound, and the antibacterial agent is a polyethylene glycol coated silver ion nanoparticle with a particle size of 20nm-50nm.

5. The method of claim 1, wherein the gastroenteral unit is prepared by the steps of: In the water cooling and shaping process of step (4), the circulation flow rate of the cooling water is 10 L / min-15 L / min, and the ratio of the axial stretching rate of the pipe body of the integrated pipe to the cooling rate is 1:(0.8-1.2), and when the ratio is 1:1, the axial shrinkage rate of the pipe body is ≤2%.

6. The method of claim 1, wherein the gastroenteral unit is prepared by the steps of: The gradual change rate of the cavity number switching is 0.8 cavities / mm-1.2 cavities / mm, and is synchronous with the change rate of the diameter of the pipe body of the integrated pipe.

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