Corrugated pipe and injection molding method thereof

Abstract

The invention discloses a corrugated pipe and an injection molding method thereof.According to the method, polyethylene and a preset formula additive are accurately controlled, the polyethylene and the preset formula additive are evenly heated through a feeding structure to form a polymer fluid in a molten state, it is ensured that materials are evenly distributed in a nozzle and a mold assembly, and in the injection molding process, the injection molding efficiency is improved; the polymer fluid is injected into the mold cavity around the mold core, the phenomenon of uneven flowing is avoided, and therefore materials in the corrugated pipe blank are distributed more evenly, and the structure is more compact. Through circulating liquid cooling treatment at the preset low temperature, the cooling speed and temperature distribution are effectively controlled in the cooling process, it is ensured that residual stress in the corrugated pipe is fully released, and therefore the ring stiffness and structural stability of the corrugated pipe are improved; and a method of heating to a preset high temperature at a preset temperature rise rate and keeping the temperature for a preset time is adopted for heat treatment and then cooling, so that the fatigue-resistant corrugated pipe with higher fatigue resistance is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of bellows, and in particular to a bellows and an injection molding method thereof. Background Art

[0002] With the increasing demand for pipes in the fields of construction, industry and agriculture, corrugated pipes are widely used in drainage, ventilation and cable protection due to their good flexibility, lightweight characteristics and ability to withstand certain pressures. The corrugated structure of the corrugated pipe enables it to withstand certain mechanical loads while maintaining its lightweight. However, with the complexity of the use environment, especially under conditions of frequent bending and vibration, the mechanical properties and service life of traditional corrugated pipes are often difficult to meet higher requirements. Therefore, improving the performance of corrugated pipes has become a key direction for the development of industry technology. In the prior art, the production of bellows mostly adopts the injection molding process, but after the bellows are made by injection molding, most of them only adopt natural cooling or a single liquid cooling treatment, lacking precise control over the cooling rate and temperature distribution, which can easily lead to insufficient release of residual stress inside the bellows, resulting in poor structural stability of the bellows, and thus prone to fatigue damage when repeatedly bent or vibrated and compressed.

[0003] Therefore, it is necessary to provide an injection molding method for a bellows to solve the problem that the bellows is prone to fatigue failure when repeatedly bent or vibrated and compressed. Summary of the invention

[0004] The main purpose of the present invention is to provide a bellows and an injection molding method thereof, aiming to solve the technical problems mentioned in the above background technology.

[0005] The present invention adopts the following technical solutions: A method for injection molding a corrugated pipe, comprising: S100: providing an injection molding device, the injection molding device comprising a feeding structure, a nozzle and a mold assembly, the nozzle being in communication with the feeding structure and the mold assembly, the mold assembly comprising a plurality of mold cavities, mold cores being connected to two opposite sides of the mold cavities, and the nozzle being disposed between two of the mold cores; S200: heating polyethylene and a preset formula additive through the feeding structure to form a polymer fluid in a molten state; S300: injecting the polymer fluid into the mold cavity through the nozzle, so that the polymer fluid surrounds the mold core to form a bellows blank; S400: cooling the bellows blank, continuously cooling the bellows blank by circulating liquid cooling at a preset low temperature to obtain a bellows with high ring stiffness; S500: heating the high ring stiffness bellows to a preset high temperature at a preset temperature rise rate and keeping the temperature for a preset time, and slowly cooling the high ring stiffness bellows to room temperature by thermal inertia to obtain a fatigue-resistant bellows with high ring stiffness; S600: performing a fatigue strength test on the fatigue-resistant bellows to obtain a fatigue life curve, and judging whether the fatigue-resistant bellows meets a preset target. When the fatigue-resistant bellows does not meet the preset target, segmenting the fatigue-resistant bellows to obtain a plurality of tube rings; S700: Obtain the ring stiffness of the plurality of tube rings and calculate the ring stiffness variance according to the plurality of ring stiffnesses, determine whether the fatigue-resistant bellows meets the preset ring stiffness, if so, increase the preset high temperature, if not, reduce the preset low temperature.

[0006] Furthermore, the preset formula additives include antioxidants, anti-ultraviolet agents and plasticizers; The antioxidant is a mixture of one or more of 2,6-di-tert-butyl-p-cresol, tris(2,4-di-tert-butylphenyl)phosphite or dilauryl dioctylthiodipropionate; The anti-ultraviolet agent is a mixture of one or more of 2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole, dibenzoylmethane or diphenyl (2,4,6-trichlorophenyl) dithiophosphate; The plasticizer is a mixture of one or more of dibutyl phthalate, diisooctyl phthalate or dioctyl terephthalate; Among them, in the polymer fluid, calculated by mass percentage, the antioxidant accounts for 0.4-0.6%, the anti-ultraviolet agent accounts for 0.9-1.1%, the plasticizer accounts for 1.8-2.1%, and the balance is the polyethylene.

[0007] Furthermore, the step of heating the polyethylene and the preset formula additives through the feeding structure to form a polymer fluid in a molten state specifically includes: S210: uniformly mixing the polyethylene, antioxidant, anti-ultraviolet agent and plasticizer and drying them to obtain a mixed base material; S220: adding the mixed base material into the feeding structure, wherein the feeding structure is provided with a heating unit and a degassing unit, dynamically heating the mixed base material to 140° C. to 180° C. by the heating unit to melt the mixed base material, and performing vacuum degassing treatment on the melted mixed base material by the degassing unit based on a preset negative pressure value; S230: stirring the vacuum degassed melt at a preset rotation speed and a preset frequency to disperse the antioxidant, anti-ultraviolet agent and plasticizer in the polyethylene, and eliminate the temperature difference between the melts to form a uniform polymer fluid; S240: finely filter the uniform polymer fluid to remove impurities and particles in the polymer fluid.

[0008] Furthermore, the step of injecting the polymer fluid into the mold cavity through the nozzle so that the polymer fluid surrounds the mold core to form the corrugated tube blank specifically includes: S310: dividing the polymer fluid from the nozzle into a plurality of uniform fluid branches, distributing the fluid branches according to the mold cavity, and obtaining a polymer fluid distribution path matching the mold cavity; S320: According to the geometric structure of the mold cavity, the polymer fluid distribution path is introduced into the mold cavity, and the polymer fluid is guided based on the gradient guide groove to control the flow rate and direction of the polymer fluid to obtain a uniformly distributed polymer fluid flow field; S330: adjusting the pressure distribution of the polymer fluid based on the polymer fluid flow field and according to the structure of the mold core to obtain a polymer fluid coating layer that evenly fits the mold core; S340: applying extrusion force to the polymer fluid in the mold cavity, and allowing the polymer fluid coating layer to completely wrap the mold core to obtain a corrugated tube blank.

[0009] Furthermore, the injection molding device also includes a demolding structure, which includes a bracket, a plurality of mold cores are symmetrically arranged on opposite sides of the bracket, and the bracket is detachably connected to the plurality of mold cores, an extrusion groove is arranged in the middle of the bracket, and a push rod is connected to one end of the mold core facing the extrusion groove, a cylinder is arranged above the push rod, and a plurality of extrusion tapered columns are connected to the output shaft of the cylinder, and the extrusion tapered columns are arranged corresponding to the push rod.

[0010] Furthermore, after the step of injecting the polymer fluid into the mold cavity through the nozzle so that the polymer fluid surrounds the mold core to form the corrugated tube blank, the method further includes: S350: placing the mold core wrapped with the corrugated tube blank on the support; S360: starting the cylinder to drive the extrusion tapered column to descend toward the extrusion groove, the extrusion tapered column contacts the push rod and applies a gradually increasing extrusion force to the push rod; S370: the push rod is forced to push the mold core to move in a direction away from the extrusion groove, and the mold core gradually separates from the bracket and is pushed out to a predetermined position; S380: Separating the corrugated tube blank from the mold core to complete demolding of the corrugated tube blank.

[0011] Furthermore, the step of cooling the bellows blank and continuously cooling the bellows blank by circulating liquid cooling at a preset low temperature to obtain a high ring stiffness bellows specifically includes: S410: placing the corrugated tube blank in a cooling treatment system for precooling treatment, so that the surface of the corrugated tube blank drops to a preset initial cooling temperature, thereby obtaining a precooled corrugated tube blank; S420: adjusting the cooling treatment system to a preset low temperature, and placing the pre-cooled corrugated tube blank into a cooling tank for uniform liquid cooling treatment to obtain a preliminarily cooled corrugated tube blank, wherein the cooling tank includes a plurality of circulating cooling nozzles and a temperature control unit, and the temperature control unit controls the temperature of the circulating cooling nozzles; S430: moving the preliminarily cooled bellows blank to a preset low-temperature air cooling area, and uniformly spraying cold air on the inner surface and outer surface of the bellows blank; S440: placing the bellows blank after the cold air is sprayed in a preset static area for stabilization treatment, so that the bellows blank gradually reaches a thermal equilibrium state, and obtaining a high ring stiffness bellows.

[0012] Furthermore, the step of heating the high ring stiffness bellows to a preset high temperature at a preset temperature rise rate and keeping the temperature for a preset time, and slowly cooling the high ring stiffness bellows to room temperature by thermal inertia to obtain a fatigue-resistant bellows with high ring stiffness specifically includes: S510: placing the high ring stiffness bellows in a constant temperature heating furnace to obtain actual temperature change data during the heating process; S520: According to the actual temperature change data, the heating furnace is controlled to a preset temperature rise rate, so that the bellows is evenly heated to a preset high temperature, and the heating is continued at the preset high temperature for a preset time; S530: During the continuous heating process, monitoring the internal pressure change of the high ring stiffness bellows, and calculating the expansion rate of the high ring stiffness bellows; S540: determining whether the expansion rate satisfies a preset change value, and if the expansion rate does not satisfy the preset change value, changing the heating variable until the expansion rate satisfies the preset change value; S550: slowly cooling the high ring stiffness bellows to room temperature by thermal inertia to obtain a fatigue-resistant bellows with high ring stiffness.

[0013] Furthermore, the step of obtaining the ring stiffness of the plurality of tube rings and calculating the ring stiffness variance according to the plurality of ring stiffnesses to determine whether the fatigue-resistant bellows meets the preset ring stiffness specifically includes: S710: measuring the ring stiffness of each segmented tube ring, compressing the tube ring by a preset compression load, measuring the deformation of each tube ring, and obtaining the ring stiffness data of each tube ring; S720: calculating the ring stiffness variance of multiple pipe rings according to the ring stiffness data of each pipe ring, and comparing the ring stiffness variance with the preset ring stiffness to determine whether the ring stiffness variance meets the preset ring stiffness, and obtaining a first determination result; S730: Compare the ring stiffness data of each pipe ring with the preset ring stiffness respectively, determine whether the number of all the ring stiffness data that meet the preset ring stiffness is greater than a preset threshold, and obtain a second determination result; S740: If both the first judgment result and the second judgment result are yes, the fatigue-resistant bellows meets the preset ring stiffness; if either of the first judgment result and the second judgment result is no, the fatigue-resistant bellows does not meet the preset ring stiffness.

[0014] The present invention also provides a bellows, which is realized by the injection molding method of the bellows as described in any of the above items, and the bellows includes a bellows body and two connecting ports, the two connecting ports are respectively arranged at the opposite ends of the bellows body, and the same side of the bellows body and the two connecting ports are provided with a stripping groove.

[0015] Beneficial effects: In the present invention, polyethylene and preset formula additives are precisely controlled to be uniformly heated through the feeding structure to form a polymer fluid in a molten state, ensuring uniform distribution of the material in the nozzle and the mold assembly. During the injection molding process, the polymer fluid is injected into the mold cavity around the mold core, avoiding the occurrence of uneven flow, thereby making the distribution of the material inside the bellows blank more uniform and the structure more compact. Through the circulating liquid cooling treatment at a preset low temperature, the cooling rate and temperature distribution are effectively controlled during the cooling process to ensure the full release of the residual stress inside the bellows, thereby improving the ring stiffness and structural stability of the bellows, and the method of heating to a preset high temperature at a preset temperature rise rate and keeping it warm for a preset time is used for heat treatment and then cooling, thereby obtaining a fatigue-resistant bellows with stronger fatigue resistance. In addition, a detection method for fatigue-resistant bellows is also used to further correct and ensure the quality of the injection molded product, effectively avoiding the problem of fatigue damage of the bellows when it is repeatedly bent or vibrated and compressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic flow chart of an injection molding method of a corrugated pipe of the present invention; Figure 2 It is a flow chart of another embodiment of the present invention.

[0017] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0018] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0019] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0020] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0022] Reference Figure 1 The present invention provides a method for injection molding a corrugated pipe, comprising: S100: providing an injection molding device, the injection molding device comprising a feeding structure, a nozzle and a mold assembly, the nozzle being in communication with the feeding structure and the mold assembly, the mold assembly comprising a plurality of mold cavities, mold cores being connected to two opposite sides of the mold cavities, and the nozzle being disposed between two of the mold cores; In step S100, the injection molding device includes a feeding structure, a nozzle and a mold assembly. The function of the feeding structure is to accurately deliver polyethylene and preset formula additives to the nozzle part. The structure can be composed of a hopper, a screw, a heater and a control system. The hopper is responsible for storing the mixed material, and the screw pushes the material from the hopper to the heater by rotation to heat it to a molten state. The nozzle is connected to the feeding structure and the mold assembly, and is used to inject the molten polymer fluid into the mold cavity. The mold assembly is configured with multiple mold cavities, and a mold core is connected to the opposite sides of each mold cavity. The mold core is designed to form the inner and outer shapes of the bellows to ensure the precision and consistency of the final bellows. In this embodiment, the mold cavity is preferably set to 8, then the mold core is 16, and the injection cavity formed is also 16. The nozzle is set between the two mold cores, and the number of the mold cavities is the same as 8, so that the polymer fluid can be injected into the mold cavity from the middle, ensuring that the plastic flows evenly and is filled with components, and avoiding the formation of irregular flow or cooling areas. In specific operations, the feeding structure needs to be heated to maintain it within a suitable temperature range, and the mold assembly needs to be adjusted to ensure that its connection with the nozzle is unobstructed for normal injection molding operations.

[0023] S200: heating polyethylene and a preset formula additive through the feeding structure to form a polymer fluid in a molten state; In step S200, polyethylene and preset formula additives are heated through the feeding structure to form a polymer fluid in a molten state. Specifically, the calculated polyethylene and preset formula additives are added to the feeding hopper in proportion, and then the feeding structure is started, and the heating and screw rotation devices are turned on. A control system can be set so that the heater heats the material to a range of 140°C to 180°C for melting, and at the same time, the screw gradually pushes the mixture into the heating zone to achieve melting by continuously heating the material. During the whole process, the temperature control system monitors the temperature changes in real time to ensure that the molten material maintains a uniform and consistent melting state, and finally forms a stable and uniform polymer fluid so that it can enter the mold assembly through the nozzle. During this process, it is necessary to pay attention to controlling the heating speed and material flow rate to avoid quality problems caused by overheating or insufficient heating.

[0024] S300: injecting the polymer fluid into the mold cavity through the nozzle, so that the polymer fluid surrounds the mold core to form a bellows blank; In step S300, ensure that the polymer fluid is injected into the mold cavity through the nozzle so that it evenly surrounds the mold core to form a bellows blank. The molten polymer fluid entering from the feeding structure is rapidly distributed to each mold cavity under the pressure in the nozzle. Set the injection speed and pressure of the nozzle to ensure that all mold cavities are filled with liquid material in a short time. Each mold core in the mold is evenly distributed to ensure that the material is formed around the mold core to avoid uneven flow problems. After the injection is completed, maintain a certain pressure to ensure that the material completely fills every corner of the mold cavity to prevent deformation or gaps. At the same time, monitor the temperature of the mold and the nozzle to maintain a stable molding state, and finally obtain a bellows blank with uniform size and dense texture.

[0025] S400: cooling the bellows blank, continuously cooling the bellows blank by circulating liquid cooling at a preset low temperature to obtain a bellows with high ring stiffness; In step S400, the bellows blank after injection molding is removed from the mold cavity and cooled. During the cooling process, a preset low-temperature circulating liquid cooling technology is used to continuously cool the bellows blank. The specific operation steps include: first, the bellows blank is placed in the cooling treatment area, the cooling system is started, and appropriate low-temperature parameters are set. The coolant is introduced from the liquid storage tank into the cooling pipe through a circulating pump, and then evenly sprayed onto the surface of the bellows blank to evenly cool the entire blank. During this process, the temperature and flow of the coolant are precisely controlled by the temperature control system to ensure that the temperature of the blank drops evenly from the inside to the outside, and to minimize the generation of internal stress. During the entire cooling cycle, the temperature change of the bellows blank is continuously monitored to ensure that it reaches a stable temperature in the cooling chamber, and finally a bellows with high ring stiffness is obtained.

[0026] S500: heating the high ring stiffness bellows to a preset high temperature at a preset temperature rise rate and keeping the temperature for a preset time, and slowly cooling the high ring stiffness bellows to room temperature by thermal inertia to obtain a fatigue-resistant bellows with high ring stiffness; In step S500, the cooled high-ring stiffness bellows is gradually heated to a preset high temperature at a preset temperature rise rate, and maintained for a certain period of time, so that the bellows is evenly heated and residual stress is eliminated as much as possible. The specific setting of the gradual heating rate can be controlled at about 5°C per minute, so that the temperature of the bellows blank gradually rises to the range of 110°C to 130°C. After reaching the preset high temperature, the constant temperature is maintained for a certain period of time to ensure that the temperature inside and outside the bellows blank is consistent, evenly heated, and fully released. After the insulation stage is over, the heating system is gradually turned off, and the thermal inertia is used to slowly cool the bellows to room temperature to avoid the rebound of internal stress caused by sudden cooling, and finally a fatigue-resistant bellows with high ring stiffness is obtained.

[0027] S600: performing a fatigue strength test on the fatigue-resistant bellows to obtain a fatigue life curve, and judging whether the fatigue-resistant bellows meets a preset target. When the fatigue-resistant bellows does not meet the preset target, segmenting the fatigue-resistant bellows to obtain a plurality of tube rings; In step S600, the fatigue-resistant bellows that have undergone heat treatment need to undergo fatigue strength testing to obtain their fatigue life curve and determine whether their performance meets the standards. First, fix the bellows sample on a fatigue testing machine, set the parameters of the periodic alternating load, and start the testing machine for vibration loading. During the loading process, the material deformation and stress-strain of the bellows are monitored in real time, and the test data of each cycle is recorded until the sample fails or the preset number of test cycles is reached. A fatigue life curve is generated based on the test results, and compared with the preset standards to determine whether the bellows meets the required fatigue performance requirements. If the fatigue life does not meet the standards, the bellows needs to be divided into multiple tube rings for subsequent detailed ring stiffness testing to determine the specific fatigue damage location and cause.

[0028] S700: Obtain the ring stiffness of the plurality of tube rings and calculate the ring stiffness variance according to the plurality of ring stiffnesses, determine whether the fatigue-resistant bellows meets the preset ring stiffness, if so, increase the preset high temperature, if not, reduce the preset low temperature.

[0029] In step S700, the ring stiffness data of each ring is obtained by measuring the ring stiffness of the segmented ring ring, and the ring stiffness variance is calculated to determine the overall performance of the fatigue-resistant bellows. The segmented ring rings are placed one by one in the ring stiffness testing device, and pressure is applied to them through a preset compression load. The deformation of the ring ring is recorded during the measurement process to obtain the ring stiffness value of each ring ring. After completing the test of all ring rings, the ring stiffness data is calculated, and the ring stiffness variance of each ring ring is comprehensively calculated by the data processing system, and these data are compared with the preset ring stiffness standard. If the calculation result shows that the ring stiffness variance is within the preset standard range, the preset high temperature is increased. If it is not within the range, the preset low temperature is reduced, and the adjustment parameters are recorded for subsequent production. In this way, the consistency and reliability of the injection molding process and the cooling process are finally ensured, and the overall quality and life of the bellows are improved.

[0030] In summary, polyethylene and preset formula additives are precisely controlled to be uniformly heated through the feeding structure to form a polymer fluid in a molten state, ensuring the uniform distribution of the material in the nozzle and mold assembly. During the injection molding process, the polymer fluid is injected into the mold cavity around the mold core to avoid the occurrence of uneven flow, thereby making the distribution of the material inside the bellows blank more uniform and the structure more compact. Through the circulating liquid cooling treatment at a preset low temperature, the cooling rate and temperature distribution are effectively controlled during the cooling process to ensure the full release of the residual stress inside the bellows, thereby improving the ring stiffness and structural stability of the bellows. The method of heating to a preset high temperature at a preset temperature rise rate and keeping it warm for a preset time is used for heat treatment and then cooling, thereby obtaining a fatigue-resistant bellows with stronger fatigue resistance. In addition, the detection method for fatigue-resistant bellows is also used to further correct and ensure the quality of the injection molded products, effectively avoiding the problem of fatigue damage of the bellows when repeatedly bent or vibrated and compressed.

[0031] In one embodiment, the preset formula additives include antioxidants, UV inhibitors and plasticizers; The antioxidant is a mixture of one or more of 2,6-di-tert-butyl-p-cresol, tris(2,4-di-tert-butylphenyl)phosphite or dilauryl dioctylthiodipropionate; The anti-ultraviolet agent is a mixture of one or more of 2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole, dibenzoylmethane or diphenyl (2,4,6-trichlorophenyl) dithiophosphate; The plasticizer is a mixture of one or more of dibutyl phthalate, diisooctyl phthalate or dioctyl terephthalate; Among them, in the polymer fluid, calculated by mass percentage, the antioxidant accounts for 0.4-0.6%, the anti-ultraviolet agent accounts for 0.9-1.1%, the plasticizer accounts for 1.8-2.1%, and the balance is the polyethylene.

[0032] In this embodiment, the antioxidant can effectively prevent the polyethylene material from being degraded due to oxidation during processing and use, thereby extending the service life of the bellows. 2,6-di-tert-butyl-p-cresol has good thermal stability and antioxidant properties; tris(2,4-di-tert-butylphenyl)phosphite has higher antioxidant efficiency and is particularly suitable for applications in high temperature environments; dioctyl dilaurate thiodipropionate is a highly efficient thioester antioxidant that can significantly improve the weather resistance of the material.

[0033] The function of the UV inhibitor is to absorb or reflect UV rays, prevent UV rays from damaging polyethylene materials, and thus maintain the color and performance of the corrugated pipe. 2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole is a highly effective benzotriazole UV inhibitor with a wide absorption range and good light stability; dibenzoylmethane is an organic compound that absorbs UV rays and can be used in the production of outdoor products; diphenyl (2,4,6-trichlorophenyl) dithiophosphate has excellent hydrolysis resistance and is suitable for applications in humid environments.

[0034] Plasticizers are used to improve the processing properties and flexibility of polyethylene materials, making them easier to injection mold. Dibutyl phthalate has good compatibility and low-temperature performance; diisooctyl phthalate has higher heat resistance and migration resistance, and is suitable for high-temperature and long-term use; dioctyl terephthalate is an environmentally friendly plasticizer with low toxicity and good biodegradability.

[0035] Specifically, antioxidants, UV inhibitors and plasticizers are added to the polymer fluid in a certain proportion and processed by an injection molding machine. Among them, the antioxidant accounts for 0.4~0.6%, which can effectively prevent the oxidation and degradation of the material; the UV inhibitor accounts for 0.9~1.1%, which can significantly improve the weather resistance and anti-aging properties of the material; the plasticizer accounts for 1.8~2.1%, which can improve the processing performance and flexibility of the material. The balance is polyethylene, which is the main component of the corrugated pipe and provides good mechanical properties and chemical stability.

[0036] In one embodiment, the step of heating the polyethylene and the preset formula additives through the feeding structure to form a polymer fluid in a molten state specifically includes: S210: uniformly mixing the polyethylene, antioxidant, anti-ultraviolet agent and plasticizer and drying them to obtain a mixed base material; S220: adding the mixed base material into the feeding structure, wherein the feeding structure is provided with a heating unit and a degassing unit, dynamically heating the mixed base material to 140° C. to 180° C. by the heating unit to melt the mixed base material, and performing vacuum degassing treatment on the melted mixed base material by the degassing unit based on a preset negative pressure value; S230: stirring the vacuum degassed melt at a preset rotation speed and a preset frequency to disperse the antioxidant, anti-ultraviolet agent and plasticizer in the polyethylene, and eliminate the temperature difference between the melts to form a uniform polymer fluid; S240: finely filter the uniform polymer fluid to remove impurities and particles in the polymer fluid.

[0037] In this embodiment, polyethylene, antioxidant, anti-ultraviolet agent and plasticizer are mixed evenly in S210, which ensures that the components can be evenly distributed in the subsequent processing. The mixed materials also need to be dried to remove moisture therein to avoid bubbles generated during the injection molding process, which affects the quality of the corrugated pipe.

[0038] In S220, the dried mixed base material is added to the feeding structure. The feeding structure is provided with a heating unit and a degassing unit. The heating unit heats the mixed base material to a molten state of 140°C to 180°C by dynamically increasing the temperature. At the same time, the degassing unit performs vacuum degassing on the molten mixed base material under a preset negative pressure value to remove the gas and volatile substances therein to ensure the purity of the melt.

[0039] In S230, the molten material after vacuum degassing is stirred at a preset rotation speed and a preset frequency. The purpose of this step is to make the antioxidant, anti-ultraviolet agent and plasticizer more evenly dispersed in the polyethylene, and to eliminate the temperature difference between the molten materials to form a uniform polymer fluid.

[0040] In S240, the uniform polymer fluid is precisely filtered, and the impurities and particles in the polymer fluid are removed through the fine screening effect of the filter, ensuring that the final injection-molded bellows has excellent performance and appearance. These steps are closely linked and together constitute the key links in the bellows injection molding process.

[0041] In one embodiment, the step of injecting the polymer fluid into the mold cavity through the nozzle so that the polymer fluid surrounds the mold core to form the corrugated tube blank specifically includes: S310: dividing the polymer fluid from the nozzle into a plurality of uniform fluid branches, distributing the fluid branches according to the mold cavity, and obtaining a polymer fluid distribution path matching the mold cavity; S320: According to the geometric structure of the mold cavity, the polymer fluid distribution path is introduced into the mold cavity, and the polymer fluid is guided based on the gradient guide groove to control the flow rate and direction of the polymer fluid to obtain a uniformly distributed polymer fluid flow field; S330: adjusting the pressure distribution of the polymer fluid based on the polymer fluid flow field and according to the structure of the mold core to obtain a polymer fluid coating layer that evenly fits the mold core; S340: applying extrusion force to the polymer fluid in the mold cavity, and allowing the polymer fluid coating layer to completely wrap the mold core to obtain a corrugated tube blank.

[0042] In this embodiment, step S310 involves dividing the polymer fluid output from the nozzle into a plurality of uniform fluid branches, thereby ensuring that the fluid can be evenly and effectively distributed to various parts of the mold cavity and avoiding local accumulation or loss of the fluid in the mold cavity.

[0043] In step S320, these fluid branches are introduced into the mold cavity according to the geometric structure of the mold cavity. In this process, the gradient guide groove plays a key role, which not only controls the flow rate of the polymer fluid, but also ensures the correct direction of the fluid in the mold cavity, thereby forming a uniformly distributed polymer fluid flow field.

[0044] The S330 focuses on adjusting the pressure distribution of the polymer fluid so that it can fit the mold core evenly. This step is critical because it directly affects the quality of the bellows blank. By precisely adjusting the pressure of the polymer fluid, it can be ensured that the fluid forms a uniform coating around the mold core.

[0045] In S340, an extrusion force is applied to the polymer fluid in the mold cavity to completely wrap the mold core. This step is the key to the formation of the bellows blank, which ensures that the polymer fluid can fit tightly on the mold core and form a bellows blank with a uniform corrugated structure after cooling and solidification, ensuring the high quality and consistency of the bellows.

[0046] In one embodiment, the injection molding device also includes a demolding structure, which includes a bracket, a plurality of mold cores are symmetrically arranged on opposite sides of the bracket, and the bracket is detachably connected to the plurality of mold cores, an extrusion groove is arranged in the middle of the bracket, and a push rod is connected to one end of the mold core facing the extrusion groove, a cylinder is arranged above the push rod, and a plurality of extrusion tapered columns are connected to the output shaft of the cylinder, and the extrusion tapered columns are arranged corresponding to the push rod.

[0047] In this embodiment, the injection molding device also includes a demolding structure, which is intended to efficiently and accurately complete the demolding process of the corrugated pipe. The bracket serves as a supporting component during demolding, and multiple mold cores are symmetrically arranged on both sides of the bracket, and the mold cores are embedded in specific holes of the bracket. An extrusion groove is reserved in the middle of the bracket to provide necessary space for the demolding operation of pressing down the extrusion taper column.

[0048] Each mold core is connected to a push rod at one end facing the extrusion groove, that is, the push rod is located in the extrusion groove, and the push rod plays a key role in demoulding. A cylinder is installed above the push rod, and the output shaft of the cylinder is connected to multiple extrusion taper columns, and the extrusion taper columns correspond to the push rods one by one. When the demoulding process starts, the cylinder drives the extrusion taper column to move downward, and the mold core and the corrugated tube blank on it are pushed out of the extrusion groove smoothly through the push rod.

[0049] In one embodiment, after the step of injecting the polymer fluid into the mold cavity through the nozzle so that the polymer fluid surrounds the mold core to form the corrugated tube blank, the method further includes: S350: placing the mold core wrapped with the corrugated tube blank on the support; S360: starting the cylinder to drive the extrusion tapered column to descend toward the extrusion groove, the extrusion tapered column contacts the push rod and applies a gradually increasing extrusion force to the push rod; S370: the push rod is forced to push the mold core to move in a direction away from the extrusion groove, and the mold core gradually separates from the bracket and is pushed out to a predetermined position; S380: Separating the corrugated tube blank from the mold core to complete demolding of the corrugated tube blank.

[0050] In this embodiment, in S350, the mold core wrapped with the corrugated tube blank is placed on the bracket to ensure that the mold core is positioned accurately so that the subsequent demolding operation can proceed smoothly.

[0051] Step S360 starts the cylinder to drive the extrusion taper column to descend toward the extrusion groove. During this process, the extrusion taper column gradually contacts the push rod and begins to exert a gradually increasing extrusion force on the push rod. The extrusion force is the key to the demoulding process, ensuring that the corrugated tube blank can be smoothly separated from the mold core.

[0052] In S370, the push rod gradually pushes the mold core to move away from the extrusion groove after being subjected to the extrusion force. As the mold core moves, it gradually separates from the bracket and falls to a predetermined position, which can be set to facilitate the collection of the mold core or to facilitate the subsequent separation operation of the corrugated tube blank and the mold core.

[0053] In S380, the corrugated tube blank is separated from the mold core. At this point, the corrugated tube blank has completed the demoulding process and can be taken out for subsequent processing or testing.

[0054] In one embodiment, the step of cooling the bellows blank and continuously cooling the bellows blank by circulating liquid cooling at a preset low temperature to obtain a high ring stiffness bellows specifically includes: S410: placing the corrugated tube blank in a cooling treatment system for precooling treatment, so that the surface of the corrugated tube blank drops to a preset initial cooling temperature, thereby obtaining a precooled corrugated tube blank; S420: adjusting the cooling treatment system to a preset low temperature, and placing the pre-cooled corrugated tube blank into a cooling tank for uniform liquid cooling treatment to obtain a preliminarily cooled corrugated tube blank, wherein the cooling tank includes a plurality of circulating cooling nozzles and a temperature control unit, and the temperature control unit controls the temperature of the circulating cooling nozzles; S430: moving the preliminarily cooled bellows blank to a preset low-temperature air cooling area, and uniformly spraying cold air on the inner surface and outer surface of the bellows blank; S440: placing the bellows blank after the cold air is sprayed in a preset static area for stabilization treatment, so that the bellows blank gradually reaches a thermal equilibrium state, and obtaining a high ring stiffness bellows.

[0055] In this embodiment, in S410, the corrugated tube blank is placed in a cooling treatment system for pre-cooling treatment. This process rapidly reduces the surface temperature of the blank. In step S420, the temperature of the cooling treatment system is adjusted to a preset low temperature state. The pre-cooled corrugated tube blank is placed in a cooling tank. Through the coordinated action of a number of circulating cooling nozzles and a temperature control unit, uniform liquid cooling treatment of the blank is achieved, thereby ensuring the uniformity of the overall cooling effect of the corrugated tube.

[0056] In S430, the bellows blank after preliminary cooling is moved to the low-temperature air cooling area, and the inner and outer surfaces of the blank are further cooled by uniformly spraying cold air, which helps to eliminate the residual stress in the cooling process and improve the overall performance of the bellows. Finally, in S440, the bellows blank treated with cold air spraying is placed in a preset static area for stabilization treatment. When the temperature of the bellows returns to room temperature, the blank gradually reaches a thermal equilibrium state, thereby obtaining a bellows with high ring stiffness characteristics.

[0057] In one embodiment, the step of heating the high ring stiffness bellows to a preset high temperature at a preset temperature rise rate and keeping the temperature for a preset time, and slowly cooling the high ring stiffness bellows to room temperature by thermal inertia to obtain a fatigue-resistant bellows with high ring stiffness specifically includes: S510: placing the high ring stiffness bellows in a constant temperature heating furnace to obtain actual temperature change data during the heating process; S520: According to the actual temperature change data, the heating furnace is controlled to a preset temperature rise rate, so that the bellows is evenly heated to a preset high temperature, and the heating is continued at the preset high temperature for a preset time; S530: During the continuous heating process, monitoring the internal pressure change of the high ring stiffness bellows, and calculating the expansion rate of the high ring stiffness bellows; S540: determining whether the expansion rate satisfies a preset change value, and if the expansion rate does not satisfy the preset change value, changing the heating variable until the expansion rate satisfies the preset change value; S550: slowly cooling the high ring stiffness bellows to room temperature by thermal inertia to obtain a fatigue-resistant bellows with high ring stiffness.

[0058] In this embodiment, in step S510, the high ring stiffness bellows is first placed in a constant temperature heating furnace. In step S520, the system will accurately control the heating rate of the heating furnace according to the actual temperature change data, so that it gradually heats up to the preset high temperature according to the preset temperature rise rate. This process ensures that the bellows can be heated evenly and avoids the degradation of material properties due to rapid temperature rise. The specific temperature values ​​of the preset temperature rise rate and the preset high temperature can be determined according to the material properties and required performance of the high ring stiffness bellows. Preferably, the bellows with polyethylene as the base material in this embodiment has a preset temperature rise rate set to 5 degrees Celsius per minute, and the preset high temperature is set to 100 degrees Celsius.

[0059] In step S530, the system will continuously monitor the internal pressure changes of the bellows and calculate the expansion rate of the bellows accordingly, which plays an important role in evaluating the thermal stability and fatigue resistance of the bellows. If it is determined in step S540 that the expansion rate does not meet the preset change value, it means that the thermal expansion performance of the bellows has not yet met expectations. At this time, it is necessary to adjust the heating variables, such as heating time, temperature, etc., until the expansion rate meets the preset change value. Finally, in step S550, the bellows is slowly cooled to room temperature through the principle of thermal inertia. This process helps to eliminate the residual stress inside the bellows, thereby improving fatigue resistance while ensuring its ring stiffness.

[0060] In one embodiment, the step of obtaining the ring stiffness of the plurality of tube rings and calculating the ring stiffness variance according to the plurality of ring stiffnesses to determine whether the fatigue-resistant bellows meets the preset ring stiffness specifically includes: S710: measuring the ring stiffness of each segmented tube ring, compressing the tube ring by a preset compression load, measuring the deformation of each tube ring, and obtaining the ring stiffness data of each tube ring; S720: calculating the ring stiffness variance of multiple pipe rings according to the ring stiffness data of each pipe ring, and comparing the ring stiffness variance with the preset ring stiffness to determine whether the ring stiffness variance meets the preset ring stiffness, and obtaining a first determination result; S730: Compare the ring stiffness data of each pipe ring with the preset ring stiffness respectively, determine whether the number of all the ring stiffness data that meet the preset ring stiffness is greater than a preset threshold, and obtain a second determination result; S740: If both the first judgment result and the second judgment result are yes, the fatigue-resistant bellows meets the preset ring stiffness; if either of the first judgment result and the second judgment result is no, the fatigue-resistant bellows does not meet the preset ring stiffness.

[0061] In this embodiment, the ring stiffness data of each pipe ring is obtained in S71, and the deformation of the pipe ring is observed and recorded by applying a preset compression load, thereby calculating the ring stiffness data. S720 performs statistical analysis on the ring stiffness data, calculates the total ring stiffness variance of all pipe rings, and compares it with the preset ring stiffness to determine whether the ring stiffness variance meets the preset ring stiffness, and obtains a first judgment result. It is possible to determine the discreteness of the data, that is, whether the ring stiffness of each pipe ring is stable and whether it can meet the preset requirements.

[0062] S730 further performs individual judgment on the ring stiffness data of each pipe ring to see whether they all meet the preset ring stiffness, and further counts the number of pipe rings that meet the preset ring stiffness to see whether it is greater than a preset threshold, thereby obtaining a second judgment result.

[0063] In step S740, the judgment results of the first two steps are summarized and judged. If both the first judgment result and the second judgment result are yes, that is, when the ring stiffness data of all pipe rings are stable and meet the preset requirements, it can be judged that the fatigue-resistant bellows meets the preset ring stiffness. If either the first judgment result or the second judgment result is no, or both are no, it can be judged that the fatigue-resistant bellows cannot meet the preset ring stiffness requirements.

[0064] Furthermore, under the premise that the fatigue-resistant bellows cannot meet the preset target of fatigue strength, if the fatigue-resistant bellows meets the preset ring stiffness, the preset high temperature in the heat treatment process of the bellows in S500 is increased, and if the fatigue-resistant bellows cannot meet the preset ring stiffness, the preset low temperature in the cooling treatment in S400 is reduced. The manufacturing process is adjusted through multi-level judgment conditions and feedback of multi-level judgment results to optimize the performance of the bellows, ensuring that even if deviations occur in the manufacturing process, they can be corrected by adjusting the process parameters, thereby ensuring the quality and performance of the final product and ensuring that the problem of fatigue damage of the bellows when repeatedly bent or vibrated and compressed is solved.

[0065] The present invention also provides a bellows, which is realized by the injection molding method of the bellows as described in any of the above items, and includes a bellows body and two connecting ports, the two connecting ports are respectively arranged at the opposite ends of the bellows body, and the same side of the bellows body and the two connecting ports are provided with a stripping groove.

[0066] In the above embodiment, the bellows body in the bellows in the embodiment is the core part of the bellows, responsible for bearing pressure, transmitting fluid and other functions, and the two connection ports are respectively arranged at both ends of the bellows body for connecting with other pipes or equipment. One side of the whole bellows is a stripping groove, which simplifies the production process. The design of the stripping groove of the bellows in the present invention allows the burrs after production to be directly removed as part of the stripping groove, and also saves the process of cutting the water outlet of the bellows, thereby improving production efficiency.

[0067] On the other hand, the design of the stripping groove also reflects the consideration of the adaptability of the mold. Since the bellows are usually used to transport fluids, the glue position is often thin, and the mold core may also be thin, which places high requirements on the mold precision and injection molding process. By using the inevitable burrs as the stripping groove, the mold can better adapt to the characteristics of thin glue position and thin mold core during the injection molding process, thereby ensuring the quality and performance of the product.

[0068] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for injection molding a corrugated pipe, characterized in that: include: S100: providing an injection molding device, the injection molding device comprising a feeding structure, a nozzle and a mold assembly, the nozzle being in communication with the feeding structure and the mold assembly, the mold assembly comprising a plurality of mold cavities, mold cores being connected to two opposite sides of the mold cavities, and the nozzle being disposed between two of the mold cores; S200: heating polyethylene and a preset formula additive through the feeding structure to form a polymer fluid in a molten state; S300: injecting the polymer fluid into the mold cavity through the nozzle, so that the polymer fluid surrounds the mold core to form a bellows blank; S400: cooling the bellows blank, continuously cooling the bellows blank by circulating liquid cooling at a preset low temperature to obtain a bellows with high ring stiffness; S500: heating the high ring stiffness bellows to a preset high temperature at a preset temperature rise rate and keeping the temperature for a preset time, and slowly cooling the high ring stiffness bellows to room temperature by thermal inertia to obtain a fatigue-resistant bellows with high ring stiffness; S600: performing a fatigue strength test on the fatigue-resistant bellows to obtain a fatigue life curve, and judging whether the fatigue-resistant bellows meets a preset target. When the fatigue-resistant bellows does not meet the preset target, segmenting the fatigue-resistant bellows to obtain a plurality of tube rings; S700: Obtain the ring stiffness of the plurality of tube rings and calculate the ring stiffness variance according to the plurality of ring stiffnesses, determine whether the fatigue-resistant bellows meets the preset ring stiffness, if so, increase the preset high temperature, if not, reduce the preset low temperature.

2. The method for injection molding a corrugated pipe according to claim 1, characterized in that: The preset formula additives include antioxidants, UV inhibitors and plasticizers; The antioxidant is a mixture of one or more of 2,6-di-tert-butyl-p-cresol, tris(2,4-di-tert-butylphenyl)phosphite or dilauryl dioctylthiodipropionate; The anti-ultraviolet agent is a mixture of one or more of 2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole, dibenzoylmethane or diphenyl (2,4,6-trichlorophenyl) dithiophosphate; The plasticizer is a mixture of one or more of dibutyl phthalate, diisooctyl phthalate or dioctyl terephthalate; Among them, in the polymer fluid, calculated by mass percentage, the antioxidant accounts for 0.4-0.6%, the anti-ultraviolet agent accounts for 0.9-1.1%, the plasticizer accounts for 1.8-2.1%, and the balance is the polyethylene.

3. The method for injection molding a corrugated pipe according to claim 2, characterized in that: The step of heating the polyethylene and the preset formula additives through the feeding structure to form a polymer fluid in a molten state specifically includes: S210: uniformly mixing the polyethylene, antioxidant, anti-ultraviolet agent and plasticizer and drying them to obtain a mixed base material; S220: adding the mixed base material into the feeding structure, wherein the feeding structure is provided with a heating unit and a degassing unit, dynamically heating the mixed base material to 140° C. to 180° C. by the heating unit to melt the mixed base material, and performing vacuum degassing treatment on the melted mixed base material by the degassing unit based on a preset negative pressure value; S230: stirring the vacuum degassed melt at a preset rotation speed and a preset frequency to disperse the antioxidant, anti-ultraviolet agent and plasticizer in the polyethylene, and eliminate the temperature difference between the melts to form a uniform polymer fluid; S240: finely filter the uniform polymer fluid to remove impurities and particles in the polymer fluid.

4. The method for injection molding a corrugated pipe according to claim 1, characterized in that: The step of injecting the polymer fluid into the mold cavity through the nozzle so that the polymer fluid surrounds the mold core to form a corrugated tube blank specifically includes: S310: dividing the polymer fluid from the nozzle into a plurality of uniform fluid branches, distributing the fluid branches according to the mold cavity, and obtaining a polymer fluid distribution path matching the mold cavity; S320: According to the geometric structure of the mold cavity, the polymer fluid distribution path is introduced into the mold cavity, and the polymer fluid is guided based on the gradient guide groove to control the flow rate and direction of the polymer fluid to obtain a uniformly distributed polymer fluid flow field; S330: adjusting the pressure distribution of the polymer fluid based on the polymer fluid flow field and according to the structure of the mold core to obtain a polymer fluid coating layer that evenly fits the mold core; S340: applying extrusion force to the polymer fluid in the mold cavity, and allowing the polymer fluid coating layer to completely wrap the mold core to obtain a corrugated tube blank.

5. The method for injection molding a corrugated pipe according to claim 1, characterized in that: The injection molding device also includes a demolding structure, which includes a bracket, a plurality of mold cores are symmetrically arranged on opposite sides of the bracket, and the bracket is detachably connected to the plurality of mold cores, an extrusion groove is arranged in the middle of the bracket, a push rod is connected to one end of the mold core facing the extrusion groove, a cylinder is arranged above the push rod, and a plurality of extrusion tapered columns are connected to the output shaft of the cylinder, and the extrusion tapered columns are arranged corresponding to the push rod.

6. The method for injection molding of a corrugated pipe according to claim 5, characterized in that: After the step of injecting the polymer fluid into the mold cavity through the nozzle so that the polymer fluid surrounds the mold core to form a corrugated tube blank, the method further includes: S350: placing the mold core wrapped with the corrugated tube blank on the support; S360: starting the cylinder to drive the extrusion tapered column to descend toward the extrusion groove, the extrusion tapered column contacts the push rod and applies a gradually increasing extrusion force to the push rod; S370: the push rod is forced to push the mold core to move in a direction away from the extrusion groove, and the mold core gradually separates from the bracket and is pushed out to a predetermined position; S380: Separating the corrugated tube blank from the mold core to complete demolding of the corrugated tube blank.

7. The method for injection molding a corrugated pipe according to claim 1, characterized in that: The step of cooling the bellows blank and continuously cooling the bellows blank by circulating liquid cooling at a preset low temperature to obtain a high ring stiffness bellows specifically includes: S410: placing the corrugated tube blank in a cooling treatment system for precooling treatment, so that the surface of the corrugated tube blank drops to a preset initial cooling temperature, thereby obtaining a precooled corrugated tube blank; S420: adjusting the cooling treatment system to a preset low temperature, and placing the pre-cooled corrugated tube blank into a cooling tank for uniform liquid cooling treatment to obtain a preliminarily cooled corrugated tube blank, wherein the cooling tank includes a plurality of circulating cooling nozzles and a temperature control unit, and the temperature control unit controls the temperature of the circulating cooling nozzles; S430: moving the preliminarily cooled bellows blank to a preset low-temperature air cooling area, and uniformly spraying cold air on the inner surface and outer surface of the bellows blank; S440: placing the bellows blank after the cold air is sprayed in a preset static area for stabilization treatment, so that the bellows blank gradually reaches a thermal equilibrium state, and obtaining a high ring stiffness bellows.

8. The method for injection molding a corrugated pipe according to claim 1, characterized in that: The step of heating the high ring stiffness corrugated pipe to a preset high temperature at a preset temperature rise rate and keeping the temperature for a preset time, and slowly cooling the high ring stiffness corrugated pipe to room temperature by thermal inertia to obtain a fatigue-resistant corrugated pipe with high ring stiffness specifically includes: S510: placing the high ring stiffness bellows in a constant temperature heating furnace to obtain actual temperature change data during the heating process; S520: According to the actual temperature change data, the heating furnace is controlled to a preset temperature rise rate, so that the bellows is evenly heated to a preset high temperature, and the heating is continued at the preset high temperature for a preset time; S530: During the continuous heating process, monitoring the internal pressure change of the high ring stiffness bellows, and calculating the expansion rate of the high ring stiffness bellows; S540: determining whether the expansion rate satisfies a preset change value, and if the expansion rate does not satisfy the preset change value, changing the heating variable until the expansion rate satisfies the preset change value; S550: slowly cooling the high ring stiffness bellows to room temperature by thermal inertia to obtain a fatigue-resistant bellows with high ring stiffness.

9. The method for injection molding a corrugated pipe according to claim 1, characterized in that: The step of obtaining the ring stiffness of the plurality of tube rings and calculating the ring stiffness variance according to the plurality of ring stiffnesses to determine whether the fatigue-resistant bellows meets the preset ring stiffness specifically includes: S710: measuring the ring stiffness of each segmented tube ring, compressing the tube ring by a preset compression load, measuring the deformation of each tube ring, and obtaining the ring stiffness data of each tube ring; S720: calculating the ring stiffness variance of multiple pipe rings according to the ring stiffness data of each pipe ring, and comparing the ring stiffness variance with the preset ring stiffness to determine whether the ring stiffness variance meets the preset ring stiffness, and obtaining a first determination result; S730: Compare the ring stiffness data of each pipe ring with the preset ring stiffness respectively, determine whether the number of all the ring stiffness data that meet the preset ring stiffness is greater than a preset threshold, and obtain a second determination result; S740: If both the first judgment result and the second judgment result are yes, the fatigue-resistant bellows meets the preset ring stiffness; if either of the first judgment result and the second judgment result is no, the fatigue-resistant bellows does not meet the preset ring stiffness.

10. A corrugated pipe, characterized in that: The method is implemented by the injection molding method of the bellows as described in any one of claims 1 to 9, wherein the bellows comprises a bellows body and two connecting ports, the two connecting ports are respectively arranged at opposite ends of the bellows body, and the same side of the bellows body and the two connecting ports are provided with a stripping groove.

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