PVC plastic cable protection layer and preparation method thereof

Abstract

The invention discloses a PVC plastic cable protection layer and a preparation method thereof.The preparation method comprises the steps that a PVC plastic base pipe is obtained through extrusion molding, and the extruded PVC plastic base pipe is heated to enable the PVC plastic base pipe to enter a high-elastic state; then the PVC base pipe in the high-elastic state is arranged in the metal pipe in a penetrating mode, two-way stretching and flaring operation are carried out, a tight physical embedded structure is formed between the PVC base pipe and the metal pipe, the deformation characteristic of an end pipe opening is optimized through the flaring technology, and therefore the stress concentration phenomenon of a connecting area in long-term use is effectively reduced; on the basis, the embedded metal ring and the metal pipe are not continuous and are suitable for a long-term insertion and extraction use scene, meanwhile, the PVC material between the metal pipe and the metal ring is allowed to freely expand and contract when the temperature changes, internal stress accumulation caused by inconsistent thermal expansion is reduced, and the connector can be suitable for a scene with high local load. Therefore, the scheme can adapt to a scene with relatively high local load, and has the advantage of relatively long service life.

Description

Technical Field

[0001] The invention relates to the technical field of pipe injection molding, and in particular to a PVC plastic cable protective layer and a preparation method thereof. Background Art

[0002] With the rapid development of the power communication industry, the performance requirements for cable protective layers are getting higher and higher. Although the traditional PVC protective layer has excellent chemical corrosion resistance and insulation performance, it has limitations in structural strength. In particular, the single-layer PVC protective layer is prone to deformation or cracking due to mechanical stress during long-term working, resulting in a decrease in protection effect. In addition, the junction between the PVC protective layer and the metal joint is often the weakest point, which is prone to sealing failure due to thermal expansion and contraction or long-term use, thus affecting the overall reliability of the cable.

[0003] Currently, the industry is trying to improve the structural strength of the PVC protective layer by compounding other materials. For example, reinforcing particles are mixed into the raw materials during the melting stage to obtain an extruded blank with higher strength. After cooling, additional protective layers are injected or other materials are added to the outside of the extruded blank to increase the strength. However, in fact, changing the raw materials can only improve the overall strength, but it is difficult to improve the performance of the weak parts. The combination of additional protective layers or other materials is usually relatively simple, and it is difficult to achieve a close fit between the two. The overall performance is still insufficient. In the scenario of long-term operation and obvious local load, it cannot meet the performance requirements of the PVC protective layer. Summary of the invention

[0004] The object of the present invention is to provide a PVC plastic cable protective layer and a preparation method thereof, so as to solve the problem that the conventional PVC protective layer has insufficient performance in the scenario of long-term operation and obvious local load.

[0005] To achieve this object, the present invention adopts the following technical solutions: A method for preparing a PVC plastic cable protective layer, comprising: A PVC plastic base tube is obtained by extrusion molding, and the extruded PVC plastic base tube is heated to make the PVC plastic base tube enter a high elastic state; A highly elastic PVC plastic base tube is inserted into a metal tube, and the highly elastic PVC plastic base tube is subjected to axial and radial biaxial stretching and expansion, and then cooled to obtain a first tube body; the first tube body comprises a middle tube and end tube openings at both ends, and the size of the end tube openings is larger than the size of the middle tube; A metal ring is embedded in the end of the first tube body, wherein the inner diameter of the metal ring is larger than the inner diameter of the middle pipe of the first tube body, so as to obtain a second tube body; The second tube body is placed in a two-color injection molding machine, and the PVC inner layer is injected at the end pipe opening by inner layer injection molding, and the PVC outer layer is injected on the outside of the middle pipe by outer layer injection molding. The PVC inner layer is wrapped with a metal ring, and the PVC outer layer is wrapped with a metal pipe, and the PVC plastic cable protective layer is obtained by cooling.

[0006] Optionally, the step of obtaining the PVC plastic base tube by extrusion molding and heating the extruded PVC plastic base tube to make the PVC plastic base tube enter a highly elastic state comprises: Extruding the PVC raw material through an extruder to form a PVC plastic base tube of a preset length; The PVC plastic base pipe is pulled to the heating device by a pulling device; The heating device provides hot air at 100°~120°, so that the hot air circulates inside and outside the PVC plastic base tube, making the PVC plastic base tube evenly enter a high elastic state.

[0007] Optionally, the step of inserting a highly elastic PVC plastic base tube into the metal tube, biaxially stretching and expanding the highly elastic PVC plastic base tube in the axial and radial directions, and cooling the tube to obtain the first tube body comprises: The PVC plastic base tube is continuously pulled to the first feeding device by the pulling device, so that the highly elastic PVC plastic base tube passes through the metal tube; Apply axial tension to the PVC plastic base pipe through an axial stretching device to stretch it along the length direction; The PVC plastic base pipe is radially expanded by the expansion device, so that the middle pipe is fitted with the inner wall of the metal pipe, and the end pipe openings at both ends are first expanded; Performing a second expansion on the end pipe opening by using an expansion die device, so that the size of the end pipe opening is larger than the size of the middle pipe; The PVC plastic base pipe is cooled to obtain a first pipe body.

[0008] Optionally, a metal ring is embedded at the end of the first tube body, and the inner diameter of the metal ring is larger than the inner diameter of the middle pipe of the first tube body, so as to obtain the second tube body, comprising: Continue to pull the PVC plastic base pipe to the second feeding device through the pulling device; The end pipe opening is heated, and a metal ring is placed in the end pipe opening through a second feeding device; The end pipe opening is cooled so that the inner wall of the end pipe opening fits with the metal ring to obtain a second pipe body.

[0009] Optionally, the second pipe body is placed in a two-color injection molding machine, an inner PVC layer is molded at the end pipe opening by inner layer injection molding, and an outer PVC layer is molded on the outside of the middle pipe by outer layer injection molding, comprising: Pass the preset insert through the middle pipe of the second tube body, and put the second tube body into the mold cavity of the two-color injection molding machine; The first injection molding part of the two-color injection molding machine performs inner layer injection molding at the end pipe mouth, so that the PVC inner layer wraps the metal ring and fits tightly with the inner wall of the end pipe mouth; The PVC outer layer is injected on the outer side of the middle pipe by the second injection molding part of the two-color injection molding machine, so that the PVC outer layer wraps the metal pipe and fits tightly with the outer wall of the middle pipe; The entire pipe body is evenly cooled by the cooling device, so that the injection molding materials of the PVC inner layer and the PVC outer layer are solidified and form a stable interlocking structure with the metal ring and the metal pipe respectively; Take out and remove the insert to get the PVC plastic cable protection.

[0010] Optionally, the PVC plastic base pipe is cooled to obtain a first pipe body, and then the method further comprises: Measure and obtain the first diameter D1 of the end of the first tube body, the diameter D2 of the metal ring, and the preset front chamfer length L c and a preset front chamfer angle θ1; According to the product of the thermal expansion coefficient of the first tube body and the first diameter D1, the expansion diameter D3 is calculated, and the expansion diameter difference Δ D ; Expansion diameter difference Δ D is a negative value; According to the expansion diameter difference Δ D And the correction angle formula, calculate the correction angle θ0; The correction angle formula is: ; The front chamfer angle θ1 and the correction angle θ0 are summed to obtain a corrected first correction angle θ2, and the corrected first correction angle θ2 is used as a new preset front chamfer angle θ1.

[0011] Optionally, the PVC plastic base pipe is cooled to obtain a first pipe body, and then the method further comprises: According to the corrected front chamfer angle θ2 and the expansion diameter difference Δ D And the correction length formula, calculate the correction length L0; The correction length formula is: ; Subtract the correction length L0 from the front chamfer length Lc to obtain the corrected first chamfer length L1, and use the corrected first chamfer length L1 as the new preset front chamfer length Lc; The chamfered metal ring model is constructed with the corrected first chamfer length L1 and the corrected first correction angle θ2, and the end nozzle model is constructed with the first diameter D1. The metal ring model and the end nozzle model are imported into the finite element analysis software to analyze the stress conditions of the metal ring model and the end nozzle model in the heating environment; Determine whether the maximum contact stress between the metal ring model and the end nozzle model exceeds the preset safety value. If not, return to perform calculation to obtain the correction angle θ0; if yes, increase the correction length L0 by the new preset front chamfer length Lc, and increase the correction angle θ0 by the new preset front chamfer angle θ1; The metal ring is front chamfered with a new preset front chamfer length Lc and a new preset front chamfer angle θ1.

[0012] Optionally, after the end pipe opening is cooled so that the inner wall of the end pipe opening fits with the metal ring to obtain the second pipe body, the method further includes: The inner wall of the end pipe opening and the inner wall of the metal ring are ultrasonically cleaned, and a polytetrafluoroethylene coating is sprayed on the inner wall of the end pipe opening and the inner wall of the metal ring by a spraying method; The polytetrafluoroethylene coating on the end pipe opening and the metal ring is heated so that the polytetrafluoroethylene coating is solidified on the end pipe opening and the metal ring.

[0013] A PVC plastic cable protective layer adopts the preparation method of the PVC plastic cable protective layer as described above, comprising: specifically comprising a base pipe, a metal pipe and a metal ring; the base pipe comprises a middle pipe and end pipe openings at both ends; the metal pipe sleeve is arranged outside the middle pipe, and the metal ring sleeve is arranged inside the end pipe openings; a PVC outer layer portion is injection-molded outside the middle pipe, and a PVC inner layer portion is injection-molded inside the end pipe openings.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The PVC plastic cable protective layer and its preparation method provided by the present invention, which inserts the highly elastic PVC base tube into the metal tube and performs bidirectional stretching and expansion operations, so that a tight physical interlocking structure is formed between the PVC base tube and the metal tube, which not only enables the metal tube to provide additional support in the middle area, enhances the compressive performance of the pipe, but also optimizes the deformation characteristics of the end pipe mouth through the expansion process, thereby effectively reducing the stress concentration phenomenon in the connection area during long-term use; on this basis, the embedded metal ring is not continuous with the metal tube, retains a certain degree of flexibility, and adapts to long-term plug-in and pull-out use scenarios, while allowing the PVC material between the metal tube and the metal ring to expand and contract freely when the temperature changes, reducing the internal stress accumulation caused by inconsistent thermal expansion, and can adapt to scenes with higher local loads. Therefore, the present PVC plastic cable protective layer and its preparation method can adapt to scenes with higher local loads and have the advantage of a longer service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0016] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical contents disclosed by the present invention.

[0017] Figure 1 A schematic diagram of a PVC plastic cable protective layer and a preparation method thereof provided in an embodiment of the present invention; Figure 2 A schematic diagram of the cross-sectional structure of a PVC plastic cable protective layer provided by an embodiment of the present invention; Illustration: 100, base pipe; 200, metal pipe; 300, metal ring; 110, middle pipe; 120, end pipe opening; 130, PVC outer layer; 140, PVC inner layer. DETAILED DESCRIPTION

[0018] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In the description of the present invention, it should be understood that the terms "upper", "lower", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the 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 a limitation of the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally arranged component at the same time.

[0020] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0021] Embodiment 1 The method for preparing the PVC plastic cable protective layer provided in this embodiment specifically includes: S100, obtaining a PVC plastic base tube by extrusion molding, and heating the extruded PVC plastic base tube to make the PVC plastic base tube enter a highly elastic state; S200, inserting a highly elastic PVC plastic base tube into the metal tube 200, and biaxially stretching and expanding the highly elastic PVC plastic base tube in the axial and radial directions, and cooling to obtain a first tube body; the first tube body includes a middle pipe 110 and end pipe openings 120 at both ends, and the size of the end pipe openings 120 is larger than the size of the middle pipe 110; S300, embedding a metal ring 300 at the end pipe opening 120 of the first pipe body, wherein the inner diameter of the metal ring 300 is larger than the inner diameter of the middle pipe 110 of the first pipe body, thereby obtaining a second pipe body; S400, putting the second tube body into a two-color injection molding machine, injecting a PVC inner layer part 140 at the end pipe opening 120 by inner layer injection molding, and injecting a PVC outer layer part 130 on the outer side of the middle pipe 110 by outer layer injection molding, the PVC inner layer part 140 wraps the metal ring 300, and the PVC outer layer part 130 wraps the metal pipe 200, and cooling to obtain a PVC plastic cable protective layer.

[0022] Specifically, the preparation method of the PVC plastic cable protective layer in this embodiment inserts the highly elastic PVC base tube into the metal tube 200 and performs bidirectional stretching and expansion operations, so that a tight physical interlocking structure is formed between the PVC base tube and the metal tube 200, which not only enables the metal tube 200 to provide additional support in the middle area and enhances the compressive performance of the pipe, but also optimizes the deformation characteristics of the end pipe mouth 120 through the expansion process, thereby effectively reducing the stress concentration phenomenon in the connection area during long-term use; on this basis, the embedded metal ring 300 is not continuous with the metal tube 200, retains a certain degree of flexibility, and adapts to long-term plug-in and pull-out use scenarios, while allowing the PVC material between the metal tube 200 and the metal ring 300 to expand and contract freely when the temperature changes, reducing the internal stress accumulation caused by inconsistent thermal expansion, and can adapt to scenes with higher local loads. Therefore, the present PVC plastic cable protective layer and its preparation method can adapt to scenes with higher local loads and have the advantage of a longer service life.

[0023] Specifically, step S100: obtaining a PVC plastic base tube by extrusion molding, and heating the extruded PVC plastic base tube to make the PVC plastic base tube enter a highly elastic state, including: S110, extruding the PVC raw material through an extruder to form a PVC plastic base tube of a preset length; S120, pulling the PVC plastic base pipe to the heating device through a pulling device; S130, providing hot air at 100°~120° through a heating device, so that the hot air circulates inside and outside the PVC plastic base tube, so that the PVC plastic base tube evenly enters a high elastic state.

[0024] Among them, the traction device can transport the cooled PVC plastic base tube from the extruder outlet to the subsequent heating device, which can be a manipulator equipped with a linear motor moving module, a vacuum adsorption traction device equipped with a linear motor moving module and other structures, which can transfer the PVC plastic base tube from the previous device to the next device; in subsequent embodiments, the equipment flow involving the PVC plastic base tube, the first tube body, and the second tube body can all be moved by the above-mentioned traction device, which is not limited in this embodiment. The heating device can achieve a higher degree of flexibility of the molecular chain inside the PVC plastic base tube by uniform heating, providing conditions for subsequent deformation processing, including but not limited to a hot air circulation furnace, a far-infrared heating device, etc. The subsequent heating method can also be heated by a similar heating structure.

[0025] Specifically, step S200: inserting a highly elastic PVC plastic base tube into the metal tube 200, biaxially stretching and expanding the highly elastic PVC plastic base tube in the axial and radial directions, and cooling to obtain a first tube body, specifically includes: S210, continue to pull the PVC plastic base tube to the first feeding device through the pulling device, so that the highly elastic PVC plastic base tube passes through the metal tube 200; Exemplarily, the first feeding device includes a positioning mold, a silo and a transfer structure, the cavity of the positioning mold matches the metal tube 200, after the positioning mold is opened, the metal tube 200 can be placed into the positioning mold from the silo through the transfer structure, and then the positioning mold is closed to position the metal tube 200; wherein, the positioning mold is provided with an avoidance hole corresponding to the PVC plastic base tube, so that the traction device can pass the PVC plastic base tube through the metal tube 200; in addition, the first feeding device may also include a manipulator for clamping the metal tube 200, the manipulator moves the metal tube 200 to a first preset position, so that the traction device can pass the PVC plastic base tube through the metal tube 200, which is not limited in this embodiment; S220, applying axial tension to the PVC plastic base pipe by an axial stretching device to stretch it along the length direction; the axial stretching device has a stretching fixture for clamping both ends of the PVC plastic base pipe, and can perform axial deformation at a preset tension and speed; S230, radially expand the PVC plastic base pipe by using an expansion device, so that the middle pipe 110 is fitted with the inner wall of the metal pipe 200, and the end pipe openings 120 at both ends are first expanded; the expansion device at least includes an expansion bag or a hydraulic expansion device that can be inserted into the PVC plastic base pipe, and uniform expansion is achieved by controlling pressure and time; S240, performing a second expansion on the end pipe opening 120 by using an expansion die device, so that the size of the end pipe opening 120 is larger than the size of the middle pipe 110, specifically, the inner diameter of the end pipe opening 120 is larger than the inner diameter of the middle pipe 110, and the outer diameter of the end pipe opening 120 is larger than the outer diameter of the middle pipe 110; the expansion die is not limited, and is well known to those skilled in the art, and is not limited in this embodiment; S250, cooling the PVC plastic base tube to obtain a first tube body; Among them, the PVC plastic base pipe is radially expanded by an expansion device to ensure a tight physical fit between the base pipe and the metal pipe 200. This interlocking structure not only improves the compressive performance of the middle pipe 110, but also greatly improves the overall stability of the pipe body. The interlocking structure can provide stronger support under the action of external force, avoiding deformation problems caused by the gap between the metal pipe 200 and the PVC base pipe. In addition, this fitting also effectively solves the problem of internal stress accumulation caused by the difference in thermal expansion and contraction under temperature difference conditions, so that the product can maintain structural stability in large temperature fluctuations.

[0026] Next, the end pipe opening 120 is further expanded through the expansion die. At this time, the end pipe opening 120 undergoes secondary expansion. The first expansion is to initially expand the end pipe opening 120 to adapt it to the overall structural stress distribution. The second expansion is to make a more refined adjustment to the end pipe opening 120 to match the subsequent metal ring 300. Through the above secondary expansion, the geometric fit between the PVC plastic base pipe and the metal ring 300 is enhanced, so that the metal pipe 200 can maintain a more stable position during installation and use, especially when there is external vibration or load changes, it exhibits better anti-displacement ability. In addition, the expansion structure is gradually formed in stages, which reduces the amount of plastic deformation generated in a single processing process, reduces stress concentration, and thus significantly improves the overall fatigue resistance.

[0027] Specifically, step S300: embedding a metal ring 300 at the end pipe opening 120 of the first pipe body, wherein the inner diameter of the metal ring 300 is larger than the inner diameter of the middle pipe 110 of the first pipe body, to obtain a second pipe body, comprising: S310, continue to pull the PVC plastic base pipe to the second feeding device through the pulling device; Exemplarily, the second feeding device may also include a positioning mold, a silo and a transfer structure. The mold cavity of the positioning mold also matches the metal tube 200. A avoidance hole is provided corresponding to the metal tube 200 (the middle outer area of ​​the first tube body), so that the end of the first tube body can be clamped by the positioning mold, so that the end nozzle 120 is suspended. Similarly, the second feeding device may also include a manipulator for clamping the first tube body, and the manipulator moves the first tube body to a second preset position, so as to facilitate the subsequent suspension of the end nozzle 120 of the first tube body for subsequent heating, installation, cooling and other steps. S320, heating the end nozzle 120, and placing the metal ring 300 in the end nozzle 120 through the second feeding device; specifically, the metal ring 300 is clamped from the silo through the transfer structure and placed in the end nozzle 120; S330, cooling the end nozzle 120 so that the inner wall of the end nozzle 120 fits with the metal ring 300 to obtain a second tube body; specifically, the end nozzle 120 can be cooled by a cooling device, and the cooling device includes but is not limited to a cold air cooling device, a cooling water tank and other structures, which can cool the end nozzle 120.

[0028] First, the first tube body is moved to the second feeding device by the traction device to ensure that the end nozzle 120 of the first tube body is suspended, so as to provide accurate positioning for subsequent operations. The second feeding device fixes the first tube body and leaves a space for the embedding of the metal ring 300 to avoid mechanical stress or deformation of the first tube body, so as to ensure that the metal ring 300 can be accurately placed in the specified position to form a mosaic structure. Then, during the embedding process of the metal ring 300, the end nozzle 120 is heated to make its material enter a highly elastic state, thereby reducing the plastic resistance of the material and facilitating the embedding of the metal ring 300. The heating not only makes the internal molecular chain of the end nozzle 120 in a highly flexible state, but also enhances the contact area with the metal ring 300 after embedding, ensuring a close fit between the two. After the metal ring 300 is embedded, the cooling device is used to quickly solidify the nozzle and restore it to a stable state, thereby realizing a long-term and stable connection between the metal ring 300 and the end nozzle 120.

[0029] As a supplementary implementation, in step S330: cooling the end nozzle 120 so that the inner wall of the end nozzle 120 fits with the metal ring 300 to obtain the second tube body, the method further includes: S340, ultrasonically cleaning the inner wall of the end nozzle 120 and the inner wall of the metal ring 300, and spraying a polytetrafluoroethylene coating on the inner wall of the end nozzle 120 and the inner wall of the metal ring 300 by spraying; S350, heating the polytetrafluoroethylene coating on the end pipe opening 120 and the metal ring 300, so that the polytetrafluoroethylene coating is cured on the end pipe opening 120 and the metal ring 300; Since the tetrafluoroethylene coating itself has an extremely low friction coefficient, the PVC material is more evenly covered on the inner wall of the metal ring 300 and the end nozzle 120 during the injection molding process of the two-color injection molding machine, reducing the friction resistance between the inner wall and the PVC, helping to improve the quality of the injection molded product of the PVC inner layer 140, and also reducing the risk of defects in the PVC inner layer 140 during the injection molding process, such as edge warping or peeling. In addition, the cured tetrafluoroethylene coating plays an auxiliary positioning role for the metal ring 300, thereby enhancing the chimeric effect in the subsequent injection molding process.

[0030] Specifically, step S400: placing the second pipe body into a two-color injection molding machine, injecting the PVC inner layer part 140 at the end pipe opening 120 by inner layer injection molding, and injecting the PVC outer layer part 130 on the outer side of the middle pipe 110 by outer layer injection molding, including: S410, passing the preset insert through the middle pipe 110 of the second tube body, and placing the second tube body into the mold cavity of the two-color injection molding machine; S420, performing inner layer injection molding at the end nozzle 120 through the first injection molding part of the two-color injection molding machine, so that the PVC inner layer part 140 wraps the metal ring 300 and fits tightly with the inner wall of the end nozzle 120; the setting of the insert can maintain the inner cavity shape of the subsequent PVC plastic cable protective layer; S430, injecting a PVC outer layer on the outer side of the middle pipe 110 through the second injection molding part of the two-color injection molding machine, so that the PVC outer layer wraps the metal pipe 200 and fits tightly with the outer wall of the middle pipe 110; S440, uniformly cooling the entire tube body by a cooling device, so that the injection molding materials of the PVC inner layer portion 140 and the PVC outer layer portion 130 are solidified and form a stable interlocking structure with the metal ring 300 and the metal tube 200 respectively; S450, take out and remove the insert to obtain the PVC plastic cable protective layer.

[0031] It should be noted that the first injection molding part of the two-color injection molding machine injects raw materials from the end nozzle 120, and the second injection molding part of the two-color injection molding machine injects raw materials from the outside of the middle pipe 110, so as to realize the embedded installation of the above-mentioned metal ring 300 and the metal pipe 200; the inner layer injection molding ensures the covering of the metal ring 300 and the sealing performance of the end, and the outer layer injection molding enhances the compressive strength and durability of the middle pipe 110. The structure of the two-color injection molding machine and its mold (the first injection molding part and the second injection molding part) are not specifically expanded in this embodiment. The specific structure of the mold is adaptively adjusted according to the position of the metal ring 300 and the metal pipe 200, and the PVC raw materials can be injected into the corresponding positions of the end nozzle 120 and the middle pipe 110, which will not be repeated in this embodiment.

[0032] On the basis of the above embodiment, in step S250: cooling the PVC plastic base pipe to obtain a first pipe body, the following further comprises: S261, measure and obtain the first diameter D1 of the end tube opening 120 of the first tube body, obtain the diameter D2 of the metal ring 300, and the preset front chamfer length L c and a preset front chamfer angle θ1; S262, calculate the expansion diameter D3 according to the product of the thermal expansion coefficient of the first tube body and the first diameter D1, and calculate the expansion diameter difference Δ D ; Expansion diameter difference Δ D is a negative value, Δ D =D1-D3; the above thermal expansion coefficient is determined by the material of the first tube; S263, according to the expansion diameter difference Δ D And the correction angle formula, calculate the correction angle θ0; The correction angle formula is: ; S264, summing the front chamfer angle θ1 and the correction angle θ0 to obtain a corrected first correction angle θ2, and using the corrected first correction angle θ2 as a new preset front chamfer angle θ1; It is understandable that in the subsequent steps, the end nozzle 120 of the first tube body needs to be heated so that the end nozzle 120 of the first tube body expands. At this time, a smaller first correction angle θ2 can be obtained according to the above steps, and this angle is used as the front chamfering angle of the metal ring 300. At this time, the smaller chamfer can also meet the installation requirements of the metal ring 300 inserted into the end nozzle 120. At the same time, the smaller chamfer can increase the contact area between the metal ring 300 and the end nozzle 120, thereby improving the firmness of the fit.

[0033] On the basis of the above embodiment, in step S250: cooling the PVC plastic base pipe to obtain a first pipe body, the following further comprises: S271, according to the corrected front chamfer angle θ2, the expansion diameter difference Δ D And the correction length formula, calculate the correction length L0; The correction length formula is: ; S272, front chamfer length L c Subtract the correction length L0 to obtain the corrected first chamfer length L1, and use the corrected first chamfer length L1 as the new preset front chamfer length L c ; S273, constructing a chamfered metal ring 300 model with the corrected first chamfer length L1 and the corrected first correction angle θ2, constructing an end nozzle 120 model with the first diameter D1, importing the metal ring 300 model and the end nozzle 120 model into finite element analysis software (such as ANSYS), and analyzing the stress conditions of the metal ring 300 model and the end nozzle 120 model in a heating environment; S274, determine whether the maximum contact stress between the metal ring 300 model and the end nozzle 120 model exceeds the preset safety value. If not, return to step S263 and calculate the correction angle θ0; if so, set the new preset front chamfer length L c Increase the correction length L0, so that the new preset front chamfer angle θ1 increases the correction angle θ0; S275, with the new preset front chamfer length L c , the metal ring 300 is front chamfered at a new preset front chamfer angle θ1.

[0034] In the above steps, a gradual correction and measurement method is adopted to make the relationship between the chamfer length and the angle more matched, optimize the introduction path of the metal ring 300, reduce the problem of insufficient contact area caused by excessive chamfer angle during installation, and avoid the embedding difficulty or instability caused by too small chamfer. As a result, the geometric design of the chamfer achieves a balance between the smoothness of introduction and the stability of the fit. The introduction of the correction angle enhances the overall fit quality of the metal ring 300 through dynamic adjustment, making the performance of the end nozzle 120 more superior in high temperature or high load scenarios. Specifically, the optimized chamfer design avoids fatigue cracking in the fitting area due to stress concentration in long-term vibration or thermal cycling, thereby extending the service life of the protective layer.

[0035] Embodiment 2 This embodiment also provides a PVC plastic cable protective layer, which is prepared by the preparation method in the above embodiment, and specifically includes a base tube 100, a metal tube 200 and a metal ring 300; the base tube 100 includes a middle tube 110 and end tube openings 120 at both ends; the metal tube 200 is sleeved outside the middle tube 110, and the metal ring 300 is sleeved inside the end tube openings 120; the middle tube 110 is injection-molded with a PVC outer layer 130, and the end tube openings 120 are injection-molded with a PVC inner layer 140. The metal of the above metal tube 200 and the metal ring 300 can be made of copper, iron and other materials, which are not limited in this embodiment.

[0036] In addition, at least a plurality of metal rings 300 are sleeved in the end pipe mouth 120. When external pressure or impact occurs, this multi-layer structure can disperse stress to evenly transfer the load, thereby avoiding stress concentration, effectively reducing the risk of material fatigue and cracking, and compensating for the expansion difference caused by temperature changes to a certain extent, thereby improving the thermal stability of the entire structure and reducing the impact of thermal cycles on the joints.

[0037] The specific implementation method and technical effects of the preparation method of the PVC plastic cable protective layer are described in Example 1. The PVC plastic cable protective layer in this example is formed by the preparation method and also has the technical effects.

[0038] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a PVC plastic cable protective layer, characterized in that: include: A PVC plastic base tube is obtained by extrusion molding, and the extruded PVC plastic base tube is heated to make the PVC plastic base tube enter a high elastic state; A highly elastic PVC plastic base tube is inserted into a metal tube, and the highly elastic PVC plastic base tube is subjected to axial and radial biaxial stretching and expansion, and then cooled to obtain a first tube body; the first tube body comprises a middle tube and end tube openings at both ends, and the size of the end tube openings is larger than the size of the middle tube; A metal ring is embedded in the end of the first tube body, wherein the inner diameter of the metal ring is larger than the inner diameter of the middle pipe of the first tube body, so as to obtain a second tube body; The second tube body is placed in a two-color injection molding machine, and the PVC inner layer is injected at the end pipe opening by inner layer injection molding, and the PVC outer layer is injected on the outside of the middle pipe by outer layer injection molding. The PVC inner layer is wrapped with a metal ring, and the PVC outer layer is wrapped with a metal pipe, and the PVC plastic cable protective layer is obtained by cooling.

2. The method for preparing a PVC plastic cable protective layer according to claim 1, characterized in that: The method of obtaining the PVC plastic base tube by extrusion molding and heating the extruded PVC plastic base tube to make the PVC plastic base tube enter a highly elastic state comprises: Extruding the PVC raw material through an extruder to form a PVC plastic base tube of a preset length; The PVC plastic base pipe is pulled to the heating device by a pulling device; The heating device provides hot air at 100°~120°, so that the hot air circulates inside and outside the PVC plastic base tube, making the PVC plastic base tube evenly enter a high elastic state.

3. The method for preparing a PVC plastic cable protective layer according to claim 2, characterized in that: The method of inserting a highly elastic PVC plastic base tube into a metal tube, biaxially stretching and expanding the highly elastic PVC plastic base tube in the axial and radial directions, and cooling the tube to obtain a first tube body comprises: The PVC plastic base tube is continuously pulled to the first feeding device by the pulling device, so that the highly elastic PVC plastic base tube passes through the metal tube; Apply axial tension to the PVC plastic base pipe through an axial stretching device to stretch it along the length direction; The PVC plastic base pipe is radially expanded by the expansion device, so that the middle pipe is fitted with the inner wall of the metal pipe, and the end pipe openings at both ends are first expanded; Performing a second expansion on the end pipe opening by using an expansion die device, so that the size of the end pipe opening is larger than the size of the middle pipe; The PVC plastic base pipe is cooled to obtain a first pipe body.

4. The method for preparing a PVC plastic cable protective layer according to claim 3, characterized in that: The metal ring is embedded in the end of the first tube body, and the inner diameter of the metal ring is larger than the inner diameter of the middle pipe of the first tube body, so as to obtain the second tube body, comprising: Continue to pull the PVC plastic base pipe to the second feeding device through the pulling device; The end pipe opening is heated, and a metal ring is placed in the end pipe opening through a second feeding device; The end pipe opening is cooled so that the inner wall of the end pipe opening fits with the metal ring to obtain a second pipe body.

5. The method for preparing a PVC plastic cable protective layer according to claim 3, characterized in that: The second pipe body is placed in a two-color injection molding machine, and a PVC inner layer portion is injected at the end pipe opening by inner layer injection molding, and a PVC outer layer portion is injected on the outer side of the middle pipe by outer layer injection molding, including: Pass the preset insert through the middle pipe of the second tube body, and put the second tube body into the mold cavity of the two-color injection molding machine; The first injection molding part of the two-color injection molding machine performs inner layer injection molding at the end pipe mouth, so that the PVC inner layer wraps the metal ring and fits tightly with the inner wall of the end pipe mouth; The PVC outer layer is injected on the outer side of the middle pipe by the second injection molding part of the two-color injection molding machine, so that the PVC outer layer wraps the metal pipe and fits tightly with the outer wall of the middle pipe; The entire pipe body is evenly cooled by the cooling device, so that the injection molding materials of the PVC inner layer and the PVC outer layer are solidified and form a stable interlocking structure with the metal ring and the metal pipe respectively; Take out and remove the insert to get the PVC plastic cable protection.

6. The method for preparing a PVC plastic cable protective layer according to claim 3, characterized in that: The PVC plastic base pipe is cooled to obtain a first pipe body, and then the following steps are further included: Measure and obtain the first diameter D1 of the end of the first tube body, the diameter D2 of the metal ring, and the preset front chamfer length L c and a preset front chamfer angle θ1; According to the product of the thermal expansion coefficient of the first tube body and the first diameter D1, the expansion diameter D3 is calculated, and the expansion diameter difference Δ D ; Expansion diameter difference Δ D is a negative value; According to the expansion diameter difference Δ D And the correction angle formula, calculate the correction angle θ0; The correction angle formula is: ; The front chamfer angle θ1 and the correction angle θ0 are summed to obtain a corrected first correction angle θ2, and the corrected first correction angle θ2 is used as a new preset front chamfer angle θ1.

7. The method for preparing a PVC plastic cable protective layer according to claim 6, characterized in that: The PVC plastic base pipe is cooled to obtain a first pipe body, and then the following steps are further included: According to the corrected front chamfer angle θ2 and the expansion diameter difference Δ D And the correction length formula, calculate the correction length L0; The correction length formula is: ; Subtract the correction length L0 from the front chamfer length Lc to obtain the corrected first chamfer length L1, and use the corrected first chamfer length L1 as the new preset front chamfer length Lc; The chamfered metal ring model is constructed with the corrected first chamfer length L1 and the corrected first correction angle θ2, and the end nozzle model is constructed with the first diameter D1. The metal ring model and the end nozzle model are imported into the finite element analysis software to analyze the stress conditions of the metal ring model and the end nozzle model in the heating environment; Determine whether the maximum contact stress between the metal ring model and the end nozzle model exceeds the preset safety value. If not, return to execute the calculation to obtain the correction angle θ0; if yes, increase the correction length L0 by the new preset front chamfer length Lc, and increase the correction angle θ0 by the new preset front chamfer angle θ1; The metal ring is front chamfered with a new preset front chamfer length Lc and a new preset front chamfer angle θ1.

8. The method for preparing a PVC plastic cable protective layer according to claim 3, characterized in that: After the end pipe opening is cooled so that the inner wall of the end pipe opening fits with the metal ring to obtain the second pipe body, the method further includes: The inner wall of the end pipe opening and the inner wall of the metal ring are ultrasonically cleaned, and a polytetrafluoroethylene coating is sprayed on the inner wall of the end pipe opening and the inner wall of the metal ring by a spraying method; The polytetrafluoroethylene coating on the end pipe opening and the metal ring is heated so that the polytetrafluoroethylene coating is solidified on the end pipe opening and the metal ring.

9. A PVC plastic cable protective layer, characterized in that: The method for preparing a PVC plastic cable protective layer as described in any one of claims 1 to 8 comprises: a base tube, a metal tube and a metal ring; the base tube comprises a middle tube and end tube openings at both ends; the metal tube sleeve is arranged outside the middle tube, and the metal ring sleeve is arranged inside the end tube openings; a PVC outer layer is injection-molded outside the middle tube, and a PVC inner layer is injection-molded inside the end tube openings.

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