PVC plastic cable protection layer and preparation method thereof

Abstract

The application discloses PVC plastic cable protection layer and a preparation method thereof, which obtains a PVC plastic base pipe through extrusion molding, heats the PVC plastic base pipe after extrusion, and makes the PVC plastic base pipe enter a high-elastic state; then, the PVC base pipe in the high-elastic state is arranged in a metal pipe and is subjected to bidirectional stretching and flaring operation, so that a close physical embedding structure is formed between the PVC base pipe and the metal pipe, and the deformation characteristics of the end pipe opening are optimized through the flaring process, thereby effectively reducing the stress concentration phenomenon of the connecting area in long-term use; on this basis, the embedded metal ring is not continuous with the metal pipe, adapts to long-term plugging and unplugging use scenarios, allows the PVC material between the metal pipe and the metal ring to freely expand and shrink when the temperature changes, reduces internal stress accumulation caused by inconsistent thermal expansion, and can adapt to scenarios with relatively high local load. Therefore, the scheme can adapt to scenarios with relatively high local load and has the advantages of higher service life.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of pipe injection molding, in particular to a PVC plastic cable protection layer and a preparation method thereof. BACKGROUND

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

[0003] At present, the industry attempts to improve the structural strength of the PVC protection layer by compounding other materials, for example, mixing reinforcing particles into the raw material during the melting stage to obtain an extruded blank with higher strength; after cooling, an additional protection layer or other materials are added to the outside of the extruded blank to improve the strength. However, in fact, changing the raw material can only improve the overall strength, and it is difficult to improve the performance of the weak part. The additional protection layer or other materials are usually combined simply, and it is difficult to achieve close fitting of the two, and the overall performance is still insufficient. In the long-term work and obvious local load scenarios, the performance requirements of the PVC protection layer cannot be met. SUMMARY

[0004] The purpose of the present application is to provide a PVC plastic cable protection layer and a preparation method thereof, which solves the problem of insufficient performance of conventional PVC protection layers in long-term work and obvious local load scenarios.

[0005] To achieve this purpose, the application adopts the following technical solutions:

[0006] A preparation method of a PVC plastic cable protection layer, comprising:

[0007] An PVC plastic base pipe is obtained by extrusion molding, and the extruded PVC plastic base pipe is heated to make the PVC plastic base pipe enter a high-elastic state;

[0008] The high-elastic PVC plastic base pipe is arranged in a metal pipe, and the high-elastic PVC plastic base pipe is subjected to bidirectional stretching and flaring in the axial and radial directions, and a first pipe body is obtained after cooling; the first pipe body comprises a middle pipe and end pipe openings at both ends, and the size of the end pipe opening is larger than that of the middle pipe;

[0009] Embedding a metal ring at the end of the pipe, the inner diameter of the metal ring is larger than the inner diameter of the middle pipe of the first pipe body, and a second pipe body is obtained;

[0010] The second pipe body is placed into a double-color injection molding machine, a PVC inner layer part is injected at the end of the pipe by inner layer injection, and a PVC outer layer part is injected outside the middle pipe by outer layer injection, the PVC inner layer part wraps the metal ring, and the PVC outer layer part wraps the metal pipe, and a PVC plastic cable protection layer is obtained after cooling.

[0011] Optionally, the PVC plastic base pipe is obtained by extrusion molding, and the PVC plastic base pipe after extrusion is heated to make the PVC plastic base pipe enter a high-elastic state, comprising:

[0012] The PVC raw material is extruded by an extruder to form a PVC plastic base pipe with a preset length;

[0013] The PVC plastic base pipe is pulled to the heating device by a pulling device;

[0014] The heating device provides hot air at 100°-120°, and the hot air circulates inside and outside the PVC plastic base pipe to make the PVC plastic base pipe uniformly enter a high-elastic state.

[0015] Optionally, the high-elastic PVC plastic base pipe is arranged in the metal pipe, and the high-elastic PVC plastic base pipe is stretched in the axial and radial directions and flared to obtain a first pipe body, comprising:

[0016] The PVC plastic base pipe is pulled to the first feeding device by the pulling device, so that the high-elastic PVC plastic base pipe is arranged in the metal pipe;

[0017] The PVC plastic base pipe is stretched in the length direction by applying an axial tension to the PVC plastic base pipe by the axial stretching equipment;

[0018] The PVC plastic base pipe is radially expanded by the expansion device to form a fit between the middle pipe and the inner wall of the metal pipe, and the end pipes at both ends are first flared;

[0019] The end pipes are secondly flared by the flaring die device, so that the size of the end pipes is larger than the size of the middle pipe;

[0020] The PVC plastic base pipe is cooled to obtain a first pipe body.

[0021] Optionally, the metal ring is embedded at the end of the pipe of the first pipe body, the inner diameter of the metal ring is larger than the inner diameter of the middle pipe of the first pipe body, and a second pipe body is obtained, comprising:

[0022] The PVC plastic base pipe is pulled to the second feeding device by the pulling device.

[0023] Heating the end nozzle and putting the metal ring into the end nozzle through the second feeding device;

[0024] Cooling the end nozzle to make the inner wall of the end nozzle fit the metal ring, and obtaining a second pipe body.

[0025] Optionally, the second pipe body is put into a double-color injection molding machine, a PVC inner layer part is injected at the end nozzle through inner layer injection, and a PVC outer layer part is injected outside the middle pipeline through outer layer injection, comprising:

[0026] Putting a preset insert through the middle pipeline of the second pipe body and putting the second pipe body into a mold cavity of the double-color injection molding machine;

[0027] Inner layer injection is performed at the end nozzle by a first injection part of the double-color injection molding machine, so that the PVC inner layer part wraps the metal ring and tightly fits the inner wall of the end nozzle;

[0028] The PVC outer layer part is injected outside the middle pipeline by a second injection part of the double-color injection molding machine, so that the PVC outer layer part wraps the metal pipe and tightly fits the outer wall of the middle pipeline;

[0029] Uniform cooling of the entire pipe body is performed by a cooling device, so that the injection materials of the PVC inner layer part and the PVC outer layer part are solidified and form a stable embedded structure with the metal ring and the metal pipe, respectively;

[0030] The insert is taken out and removed, and a PVC plastic cable protection layer is obtained.

[0031] Optionally, the PVC plastic base pipe is cooled to obtain a first pipe body, and then further comprising:

[0032] Measuring and obtaining a first caliber D1 of the end nozzle of the first pipe body, obtaining a diameter D2 of the metal ring, a preset front chamfer length L c and a preset front chamfer angle θ1;

[0033] According to the product of the thermal expansion coefficient of the first pipe body and the first caliber D1, an expansion caliber D3 is calculated, and an expansion caliber difference Δ D is calculated. D The expansion caliber difference Δ D is negative;

[0034] According to the expansion caliber difference Δ D and a correction angle formula, a correction angle θ0 is calculated.

[0035] The correction angle formula is: ;

[0036] Sum the front chamfer angle θ1 and the correction angle θ0 to obtain a first corrected correction angle θ2, and take the first corrected correction angle θ2 as a new preset front chamfer angle θ1.

[0037] Optionally, the PVC plastic base pipe is cooled to obtain a first pipe body, and then the method further comprises:

[0038] According to the first corrected correction angle θ2, the expansion diameter difference Δ D and a correction length formula, a correction length L0 is calculated.

[0039] The correction length formula is: ;

[0040] Let the front chamfer length L c Subtract the correction length L0 to obtain a first corrected chamfer length L1, and take the first corrected chamfer length L1 as a new preset front chamfer length L c ;

[0041] A chamfered metal ring model is constructed with the first corrected chamfer length L1 and the first corrected correction angle θ2, an end pipe mouth model is constructed with the first caliber D1, and the metal ring model and the end pipe mouth model are imported into a finite element analysis software to analyze the stress conditions of the metal ring model and the end pipe mouth model in a heating environment.

[0042] It is determined whether the maximum contact stress between the metal ring model and the end pipe mouth model exceeds a preset safety value, if not, the calculation of the correction angle θ0 is returned; if yes, the new preset front chamfer length L c is increased by the correction length L0, and the new preset front chamfer angle θ1 is increased by the correction angle θ0.

[0043] The metal ring is front chamfered with the new preset front chamfer length L c and the new preset front chamfer angle θ1.

[0044] Optionally, the end pipe mouth is cooled to make the inner wall of the end pipe mouth adhere to the metal ring to obtain a second pipe body, and then the method further comprises:

[0045] The inner wall of the end pipe mouth 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 mouth and the inner wall of the metal ring by a spraying method.

[0046] The polytetrafluoroethylene coating on the end pipe mouth and the metal ring is heated to make the polytetrafluoroethylene coating solidify on the end pipe mouth and the metal ring.

[0047] The PVC plastic cable protection layer adopts the preparation method of the PVC plastic cable protection layer, and specifically comprises a base pipe, a metal pipe and a metal ring.

[0048] Compared with the prior art, the PVC plastic cable protection layer has the following beneficial effects:

[0049] The PVC plastic cable protection layer and the preparation method thereof have the following advantages: the high-elastic PVC base pipe is inserted into the metal pipe and subjected to bidirectional stretching and flaring, so that a close physical fitting structure is formed between the PVC base pipe and the metal pipe; the metal pipe provides additional support in the middle region, thereby enhancing the compression resistance of the pipe; the deformation characteristics of the end pipe opening are optimized through the flaring process, thereby effectively reducing the stress concentration of the connecting region during long-term use; the embedded metal ring is not continuous with the metal pipe, and has a certain flexibility, which is suitable for long-term plugging and unplugging, and allows the PVC material between the metal pipe and the metal ring to freely expand and contract when the temperature changes, thereby reducing the internal stress accumulation caused by inconsistent thermal expansion, and adapting to scenarios with high local load. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0051] The structures, proportions, sizes, etc. shown in the drawings of the present specification are only used to cooperate with the content disclosed in the present specification, to enable those skilled in the art to understand and read, and are not used to limit the defined conditions under which the present application can be implemented, so they do not have technical significance. Any modification of structure, change of proportion relationship or adjustment of size, which does not affect the effects and purposes that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application.

[0052] Figure 1 The flowchart of the PVC plastic cable protection layer and the preparation method thereof provided by the embodiments of the present application is shown in the drawings.

[0053] Figure 2A cross-section structure schematic diagram of the PVC plastic cable protection layer provided by the embodiment of the present application is shown in the figure.

[0054] The figure shows: 100, base pipe; 200, metal pipe; 300, metal ring; 110, middle pipe; 120, end pipe; 130, PVC outer layer; 140, PVC inner layer. DETAILED DESCRIPTION

[0055] In order to make the inventive purposes, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the embodiments described below are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0056] In the description of the present application, it should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there can be a component disposed therebetween.

[0057] The technical solutions of the present application will be further described below in combination with the drawings and through specific embodiments.

[0058] Embodiment one

[0059] The preparation method of the PVC plastic cable protection layer provided by the embodiment includes the following steps:

[0060] S100, obtaining a PVC plastic base pipe by extrusion molding, and heating the PVC plastic base pipe after extrusion to make the PVC plastic base pipe enter a high-elastic state;

[0061] S200, arranging the PVC plastic base pipe in a high-elastic state in a metal pipe 200, and performing bidirectional stretching and flaring of the PVC plastic base pipe in the high-elastic state in the axial and radial directions, and cooling to obtain a first pipe body; the first pipe body includes a middle pipe 110 and end pipes 120 at both ends, and the size of the end pipes 120 is greater than the size of the middle pipe 110;

[0062] S300, embedding a metal ring 300 at the end nozzle 120 of the first pipe body, the inner diameter of the metal ring 300 is greater than the inner diameter of the middle pipe 110 of the first pipe body, to obtain a second pipe body;

[0063] S400, placing the second pipe body into a double-color injection molding machine, injecting a PVC inner layer part 140 at the end nozzle 120 through inner layer injection molding, and injecting a PVC outer layer part 130 on the outer side of the middle pipe 110 through 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 a PVC plastic cable protection layer is obtained after cooling.

[0064] Specifically, the preparation method of the PVC plastic cable protection layer in the embodiment inserts a high-elastic PVC base pipe into the metal pipe 200 and performs bidirectional stretching and flaring operation, so that a close physical embedding structure is formed between the PVC base pipe and the metal pipe 200, not only providing additional support in the middle region of the metal pipe 200 to enhance the compression resistance of the pipe, but also optimizing the deformation characteristics of the end nozzle 120 through the flaring 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 pipe 200, and a certain flexibility is reserved to adapt to the long-term plugging and unplugging use scenario, while allowing the PVC material between the metal pipe 200 and the metal ring 300 to freely expand and contract when the temperature changes, reducing the internal stress accumulation caused by inconsistent thermal expansion, and being able to adapt to scenarios with higher local load. Therefore, the PVC plastic cable protection layer and the preparation method thereof can adapt to scenarios with higher local load and have the advantage of longer service life.

[0065] Specifically, step S100: obtaining a PVC plastic base pipe by extrusion molding, and heating the extruded PVC plastic base pipe to make the PVC plastic base pipe enter a high-elastic state, including:

[0066] S110, extruding the PVC raw material through an extruder to form a PVC plastic base pipe with a predetermined length;

[0067] S120, pulling the PVC plastic base pipe to a heating device by a pulling device;

[0068] S130, providing hot air at 100°~120° by the heating device, and circulating the hot air on the inner and outer sides of the PVC plastic base pipe, so that the PVC plastic base pipe uniformly enters a high-elastic state.

[0069] The traction device can deliver the cooled PVC plastic base pipe from the outlet of the extruder to the subsequent heating device, which can be a mechanical hand with a linear motor moving module, a vacuum adsorption traction device with a linear motor moving module, etc., which can transfer the PVC plastic base pipe from the previous device to the next device; in subsequent embodiments, the equipment flow of the PVC plastic base pipe, the first pipe body and the second pipe body can be moved by the above-mentioned traction device, which is not limited in this embodiment. The heating device can make the molecular chain inside the PVC plastic base pipe reach a high flexibility through uniform heating, providing conditions for subsequent deformation processing, including but not limited to hot air circulating oven, far infrared heating device, etc., and the subsequent heating method can also be heated by similar heating structure.

[0070] Specifically, step S200: a high-elastic PVC plastic base pipe is arranged in the metal pipe 200, and the high-elastic PVC plastic base pipe is subjected to bidirectional stretching in the axial and radial directions and flaring, and a first pipe body is obtained after cooling, specifically including:

[0071] S210, continue to pull the PVC plastic base pipe to the first feeding device by the traction device, so that the high-elastic PVC plastic base pipe is arranged in the metal pipe 200;

[0072] For example, the first feeding device includes a positioning mold, a hopper and a transfer structure. The cavity of the positioning mold matches the metal pipe 200. After the positioning mold is opened, the metal pipe 200 can be put into the positioning mold from the hopper through the transfer structure, and then the positioning mold is closed to position the metal pipe 200. The positioning mold is provided with a relief hole corresponding to the PVC plastic base pipe, so that the PVC plastic base pipe can be pulled through the metal pipe 200 by the traction device. In addition, the first feeding device can also include a mechanical hand for clamping the metal pipe 200. The mechanical hand moves the metal pipe 200 to a first predetermined position, so that the PVC plastic base pipe can be pulled through the metal pipe 200 by the traction device. In this embodiment, it is not limited;

[0073] S220, the PVC plastic base pipe is stretched in the length direction by applying an axial tension to the PVC plastic base pipe by the axial stretching equipment. The axial stretching equipment has stretching clamps for clamping both ends of the PVC plastic base pipe, which can deform axially at a predetermined tension and speed;

[0074] S230, the PVC plastic base pipe is expanded radially by the expansion device, so that the middle pipe 110 is in close contact with the inner wall of the metal pipe 200, and the end pipe 120 at both ends is flared; the expansion device at least includes an expansion air bag or a hydraulic expansion device which can extend into the PVC plastic base pipe, and uniform expansion is realized by controlling the pressure and time;

[0075] S240, performing a second flaring on the end pipe mouth 120 through a flaring die device, so that the size of the end pipe mouth 120 is larger than that of the middle pipe 110, specifically, the inner diameter of the end pipe mouth 120 is larger than that of the middle pipe 110, and the outer diameter of the end pipe mouth 120 is larger than that of the middle pipe 110; the flaring die is not limited, and is well known to those skilled in the art, and is not limited in this embodiment;

[0076] S250, cooling the PVC plastic base pipe to obtain a first pipe body;

[0077] Wherein, the PVC plastic base pipe is expanded radially by the expansion device, ensuring that the base pipe and the metal pipe 200 form a tight physical fit. This fit not only improves the compression resistance of the middle pipe 110, but also greatly improves the overall stability of the pipe body. The fitted structure can provide stronger support under external force, avoiding deformation problems caused by gaps between the metal pipe 200 and the PVC base pipe. In addition, this fit effectively solves the problem of internal stress accumulation that may be caused by thermal expansion and cold contraction differences under temperature differences, so that the product can maintain structural stability under larger temperature fluctuations.

[0078] Then, the end pipe mouth 120 is further flared through a flaring die, at which time the end pipe mouth 120 is flared twice, the first flaring is to preliminarily expand the end pipe mouth 120 to adapt to the overall stress distribution, and the second flaring is to make more precise adjustment to the end pipe mouth 120 to match the subsequent metal ring 300; through the above-mentioned twice flaring, 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 showing excellent anti-displacement ability when external vibration or load changes. In addition, this flared structure is formed in stages, which reduces the amount of plastic deformation generated in a single processing process and reduces stress concentration, thereby significantly improving the overall fatigue resistance.

[0079] Specifically, step S300: embedding a metal ring 300 at the end pipe mouth 120 of the first pipe body, 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:

[0080] S310, continue to pull the PVC plastic base pipe to the second feeding device through the pulling device;

[0081] Exemplarily, the second feeding device can also include a positioning mold, a hopper and a transfer structure. The cavity of the positioning mold is also matched with the metal pipe 200, and a relief hole is provided corresponding to the metal pipe 200 (the middle outer side region of the first pipe body), so that the end portion of the first pipe body is clamped by the positioning mold, and the end portion pipe opening 120 is suspended; Similarly, the second feeding device can also include a mechanical hand for clamping the first pipe body, and the mechanical hand moves the first pipe body to a second preset position, so as to facilitate the subsequent suspension of the end portion pipe opening 120 of the first pipe body for subsequent heating, installation, cooling and the like.

[0082] S320, heating the end portion pipe opening 120 and putting the metal ring 300 into the end portion pipe opening 120 through the second feeding device; Specifically, the metal ring 300 is clamped from the hopper by the transfer structure and put into the end portion pipe opening 120.

[0083] S330, cooling the end portion pipe opening 120 to make the inner wall of the end portion pipe opening 120 adhere to the metal ring 300, and obtaining a second pipe body; Specifically, the end portion pipe opening 120 can be cooled by a cooling device, which includes but is not limited to a cold air cooling device, a cooling water tank and the like, which can cool the end portion pipe opening 120.

[0084] Firstly, the first pipe body is moved to the second feeding device by the traction device, ensuring that the end portion pipe opening 120 of the first pipe body is suspended, providing precise positioning for subsequent operations. The second feeding device fixes the first pipe body, while leaving a relief space for the embedding of the metal ring 300, to avoid mechanical stress or deformation of the first pipe body, which can ensure that the metal ring 300 can be accurately placed in the specified position to form an embedded structure. Then, during the embedding of the metal ring 300, the end portion pipe opening 120 is heated to make the material enter a high 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 molecular chain in the end portion pipe opening 120 in a high compliance state, but also enhances the contact area with the metal ring 300 after embedding, ensuring that the two are tightly adhered to each other. When the metal ring 300 is embedded, the cooling device is used to quickly solidify the pipe opening and restore it to a stable state, thereby realizing the long-term stable connection between the metal ring 300 and the end portion pipe opening 120.

[0085] As a supplementary embodiment, after step S330: cooling the end portion pipe opening 120 to make the inner wall of the end portion pipe opening 120 adhere to the metal ring 300, and obtaining a second pipe body, it further includes:

[0086] S340, ultrasonic cleaning the inner wall of the end portion pipe opening 120 and the inner wall of the metal ring 300, and spraying a polytetrafluoroethylene coating on the inner wall of the end portion pipe opening 120 and the inner wall of the metal ring 300 by a spraying method;

[0087] S350, heating the polytetrafluoroethylene coating on the end nozzle 120 and the metal ring 300, so that the polytetrafluoroethylene coating is solidified on the end nozzle 120 and the metal ring 300;

[0088] Due to the extremely low friction coefficient of the polytetrafluoroethylene coating itself, 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 injection molding quality of the PVC inner layer part 140, and also reducing the risk of defects such as edge warping or peeling during the injection molding process. In addition, the solidified polytetrafluoroethylene coating plays a role in assisting the positioning of the metal ring 300, thereby enhancing the embedding effect in the subsequent injection molding process.

[0089] Specifically, step S400: placing the second pipe body into the two-color injection molding machine, injecting the PVC inner layer part 140 at the end nozzle 120 by inner layer injection, and injecting the PVC outer layer part 130 on the outside of the middle pipe 110 by outer layer injection, comprising:

[0090] S410, inserting a pre-set insert through the middle pipe 110 of the second pipe body, and placing the second pipe body into the mold cavity of the two-color injection molding machine;

[0091] S420, inner layer injection at the end nozzle 120 by the first injection part of the two-color injection molding machine, so that the PVC inner layer part 140 wraps the metal ring 300 and tightly fits the inner wall of the end nozzle 120; the setting of the insert can maintain the shape of the inner cavity of the subsequent PVC plastic cable protection layer;

[0092] S430, injecting the PVC outer layer part on the outside of the middle pipe 110 by the second injection part of the two-color injection molding machine, so that the PVC outer layer part wraps the metal pipe 200 and tightly fits the outer wall of the middle pipe 110;

[0093] S440, uniformly cooling the entire pipe body by the cooling device, so that the injection molding materials of the PVC inner layer part 140 and the PVC outer layer part 130 are solidified and form a stable embedding structure with the metal ring 300 and the metal pipe 200, respectively;

[0094] S450, removing the insert to obtain the PVC plastic cable protection layer.

[0095] It should be noted that the first injection part of the two-color injection molding machine injects raw materials from the end pipe opening 120, the second injection part of the two-color injection molding machine injects raw materials from the outside of the middle pipe 110, and the metal ring 300 and the metal pipe 200 are embedded and installed; the inner layer injection ensures the sealing performance of the metal ring 300 and the end part, and the outer layer injection enhances the compression strength and durability of the middle pipe 110. Among them, the structure of the two-color injection molding machine and its mold (the first injection part and the second injection part) are not specifically expanded in this embodiment, and the specific structure of the mold is adaptively adjusted according to the position of the metal ring 300 and the metal pipe 200. It can be injected into the PVC raw material at the corresponding position of the end pipe opening 120 and the middle pipe 110, which is not described in detail in this embodiment.

[0096] On the basis of the above-mentioned embodiment, in step S250: cooling the PVC plastic base pipe to obtain a first pipe body, then further comprising:

[0097] S261, measure and obtain the first caliber D1 of the end pipe opening 120 of the first pipe body, obtain the diameter D2 of the metal ring 300, the preset front chamfer length L c And the preset front chamfer angle θ1;

[0098] S262, according to the product of the thermal expansion coefficient of the first pipe body and the first caliber D1, calculate the expansion caliber D3, and calculate the expansion caliber difference Δ D ; The expansion caliber difference Δ D is negative, Δ D =D1-D3; The thermal expansion coefficient is determined by the material of the first pipe body;

[0099] S263, according to the expansion caliber difference Δ D And the correction angle formula, calculate the correction angle θ0;

[0100] Among them, the correction angle formula is: ;

[0101] S264, sum the front chamfer angle θ1 and the correction angle θ0 to obtain the corrected first correction angle θ2, and take the corrected first correction angle θ2 as the new preset front chamfer angle θ1;

[0102] It can be understood that in the subsequent steps, the end pipe opening 120 of the first pipe body needs to be heated so that the end pipe opening 120 of the first pipe body expands. At this time, according to the above steps, a smaller corrected first correction angle θ2 can be obtained, and this angle is used as the front chamfer processing 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 pipe opening 120, and the smaller chamfer can also improve the contact area between the metal ring 300 and the end pipe opening 120, thereby improving the firmness of the embedding.

[0103] On the basis of the above-mentioned embodiments, the step S250 of cooling the PVC plastic base pipe to obtain a first pipe body further comprises:

[0104] S271, according to the corrected first correction angle θ2, the expansion diameter difference Δ D and the correction length formula, the correction length L0 is calculated;

[0105] The correction length formula is: ;

[0106] S272, let the front chamfer length L c subtract the correction length L0 to obtain the corrected first chamfer length L1, and take the corrected first chamfer length L1 as the new preset front chamfer length L c ;

[0107] S273, the corrected first chamfer length L1, the corrected first correction angle θ2, the chamfered metal ring 300 model is constructed, the first caliber D1 is constructed, the end pipe mouth 120 model is constructed, the metal ring 300 model and the end pipe mouth 120 model are imported into finite element analysis software (such as ANSYS), the stress condition of the metal ring 300 model and the end pipe mouth 120 model in the heating environment is analyzed;

[0108] S274, whether the maximum contact stress between the metal ring 300 model and the end pipe mouth 120 model exceeds the preset safety value is judged, if not, return to execute step S263, the correction angle θ0 is calculated; if yes, the new preset front chamfer length L c is increased by the correction length L0, and the new preset front chamfer angle θ1 is increased by the correction angle θ0;

[0109] S275, the new preset front chamfer length L c , the new preset front chamfer angle θ1 is chamfered to the metal ring 300.

[0110] In the above steps, the step-by-step correction and measurement method is adopted, the relationship between the chamfer length and the angle is matched more, the import path of the metal ring 300 is optimized, the problem of insufficient contact area caused by excessive chamfer angle in the installation process is reduced, and the problems of embedding difficulty or instability caused by small chamfer are avoided. Therefore, the geometric design of chamfer realizes the balance between smoothness and stability of embedding. The introduction of the correction angle enhances the overall embedding quality of the metal ring 300 through dynamic adjustment, so that the performance of the end pipe mouth 120 in the high temperature or high load scene is more superior. Specifically, the optimized chamfer design avoids the fatigue cracking phenomenon of the embedding area caused by stress concentration in long-term vibration or thermal cycle, thereby prolonging the service life of the protective layer.

[0111] Embodiment two

[0112] The embodiment also provides a PVC plastic cable protection layer prepared by the preparation method in the above embodiment, and specifically comprises a base pipe 100, a metal pipe 200 and a metal ring 300; the base pipe 100 comprises a middle pipe 110 and end pipe mouths 120 at both ends; the metal pipe 200 is sleeved outside the middle pipe 110, and the metal ring 300 is sleeved inside the end pipe mouth 120; a PVC outer layer part 130 is injection molded outside the middle pipe 110, and a PVC inner layer part 140 is injection molded inside the end pipe mouth 120. The metal of the metal pipe 200 and the metal ring 300 can be selected from copper, iron and the like, and is not limited in the embodiment.

[0113] In addition, at least a plurality of metal rings 300 are sleeved in the end pipe mouth 120, and when external pressure or impact occurs, the multi-layer structure can disperse stress to uniformly transmit load, thereby avoiding stress concentration, effectively reducing the risk of material fatigue and cracking, to a certain extent, compensating for the expansion difference caused by temperature change, improving the thermal stability of the whole structure, and reducing the influence of thermal cycle on the connection.

[0114] The embodiment one describes the specific implementation and technical effects of the preparation method of the PVC plastic cable protection layer, and the PVC plastic cable protection layer in the embodiment is formed by the preparation method, and also has the technical effects.

[0115] The above embodiment is only used to illustrate the technical solutions of the present application, but not to limit it; although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a PVC plastic cable protective layer, characterized in that, include: PVC plastic base pipe is obtained by extrusion molding, and the extruded PVC plastic base pipe is heated to bring the PVC plastic base pipe into 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 bidirectional stretching and flaring in both the axial and radial directions, so that the part of the PVC plastic base tube that does not protrude from the metal tube fits into the metal tube. Cooling yields a first pipe body; the first pipe body includes a central pipe and end pipe openings at both ends, the size of the end pipe openings being larger than the size of the central pipe; A metal ring is embedded at the end of the first pipe body, and the inner diameter of the metal ring is larger than the inner diameter of the middle pipe of the first pipe body to obtain the second pipe body. The second tube is placed in a two-color injection molding machine. The inner PVC layer is injected at the end of the tube through inner layer injection molding, and the outer PVC layer is injected on the outside of the middle tube through outer layer injection molding. The inner PVC layer wraps around a metal ring and is tightly fitted to the inner wall of the end tube. The outer PVC layer wraps around a metal tube and is tightly fitted to the outer wall of the middle tube. After cooling, a PVC plastic cable protection layer is obtained.

2. The method for preparing a PVC plastic cable protective layer according to claim 1, characterized in that, The process of obtaining a PVC plastic base pipe through extrusion molding and then heating the extruded PVC plastic base pipe to bring it into a highly elastic state includes: PVC raw materials are extruded through an extruder to form PVC plastic base pipes of a predetermined length; The PVC plastic base pipe is pulled to the heating device using a traction device; The heating device provides hot air at 100°~120°, which circulates inside and outside the PVC plastic base pipe, allowing the PVC plastic base pipe to uniformly enter a high-elasticity state.

3. The method for preparing a PVC plastic cable protective layer according to claim 2, characterized in that, The process of inserting a highly elastic PVC plastic base tube through a metal tube, and subjecting the highly elastic PVC plastic base tube to bidirectional stretching and flaring in both axial and radial directions, followed by cooling to obtain a first tube body, includes: Continue to pull the PVC plastic base pipe to the first feeding device through the traction device, so that the highly elastic PVC plastic base pipe passes through the metal pipe; An axial tension is applied to the PVC plastic base pipe using an axial stretching device, causing it to stretch along its length. The PVC plastic base pipe is radially expanded by the expansion device, so that the middle pipe fits into the inner wall of the metal pipe, and the end pipe openings at both ends are first flared. The end pipe opening is flared a second time using a flaring mold device, making the size of the end pipe opening larger than the size of the middle pipe. The PVC plastic base pipe is cooled to obtain the first pipe body.

4. The method for preparing a PVC plastic cable protective layer according to claim 3, characterized in that, The step of embedding a metal ring at the end of the first pipe body, wherein the inner diameter of the metal ring is larger than the inner diameter of the middle section of the first pipe body, to obtain the second pipe body, includes: Continue to pull the PVC plastic base pipe to the second feeding device using the traction device; The end of the tube is heated, and a metal ring is placed inside the end of the tube using a second feeding device. The end of the tube is cooled so that the inner wall of the end of the tube fits into the metal ring, thus obtaining the second tube.

5. The method for preparing a PVC plastic cable protective layer according to claim 3, characterized in that, The process of placing the second pipe body into a two-color injection molding machine, injecting the inner PVC layer at the end pipe opening through inner layer injection molding, and injecting the outer PVC layer on the outside of the middle pipe through outer layer injection molding includes: The pre-set insert is passed through the middle pipe of the second tube, and the second tube is placed into the mold cavity of the two-color injection molding machine; The inner layer is injected at the end of the tube opening using the first injection section of the two-color injection molding machine, so that the inner layer of PVC wraps around the metal ring and fits tightly against the inner wall of the end tube opening. The second injection section of the two-color injection molding machine injects a PVC outer layer onto the outside of the middle pipe, so that the PVC outer layer wraps around the metal pipe and fits tightly against the outer wall of the middle pipe. The entire tube is cooled evenly by a cooling device, which solidifies the injection molding materials of the inner and outer PVC layers and forms a stable interlocking structure with the metal ring and the metal tube. Remove and take out the insert to obtain the PVC plastic cable protection layer.

6. The method for preparing a PVC plastic cable protective layer according to claim 3, characterized in that, The process of cooling the PVC plastic base pipe to obtain the first pipe body further includes: Measure and obtain the first diameter D1 of the end opening of the first tube body, and obtain the diameter D2 of the metal ring and the preset front chamfer length L. c and the preset front chamfer angle θ1; The expansion diameter D3 is calculated by multiplying the thermal expansion coefficient of the first tube body by the first diameter D1, and the expansion diameter difference Δ is also calculated. D ; Expansion diameter difference Δ D It is a negative value; Based on the difference in expansion diameter Δ D And the correction angle formula is used to calculate the correction angle θ0; The formula for the correction angle is: ; Sum the front chamfer angle θ1 and the correction angle θ0 to obtain the first correction angle θ2 after correction, and use the first correction angle θ2 after correction as the 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 process of cooling the PVC plastic base pipe to obtain the first pipe body further includes: Based on the first correction angle θ2 after correction and the difference in expansion diameter Δ D And the correction length formula is used to calculate the correction length L0; The formula for the correction length is: ; Let the length of the front chamfer be L c Subtracting the correction length L0 yields the corrected first chamfer length L1, which is then used as the new preset front chamfer length L. c ; Using the corrected first chamfer length L1 and the corrected first correction angle θ2, a chamfered metal ring model is constructed, and an end pipe model is constructed using the first diameter D1. The metal ring model and the end pipe model are imported into finite element analysis software to analyze the stress of the metal ring model and the end pipe model in the heating environment. Determine whether the maximum contact stress between the metal ring model and the end nozzle model exceeds a preset safety value. If not, return to the previous calculation to obtain 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 by the correction angle θ0; With the new preset front chamfer length L c The new preset front chamfer angle θ1 is used to chamfer the metal ring.

8. The method for preparing a PVC plastic cable protective layer according to claim 4, characterized in that, After cooling the end of the tube to make the inner wall of the end of the tube fit against the metal ring to obtain the second tube, the process further includes: The inner walls of the end nozzle and the metal ring are ultrasonically cleaned, and a polytetrafluoroethylene coating is sprayed onto the inner walls of the end nozzle and the metal ring using a spraying method. The polytetrafluoroethylene coating on the end nozzle and the metal ring is heated to cure the polytetrafluoroethylene coating on the end nozzle and the metal ring.

9. A PVC plastic cable protective layer, characterized in that, The method for preparing a PVC plastic cable protective layer according to any one of claims 1-8 includes: a base pipe, a metal pipe, and a metal ring; the base pipe includes a central pipe and end pipe openings at both ends; the metal pipe is sleeved outside the central pipe, and the metal ring is sleeved inside the end pipe openings; a PVC outer layer is injection molded outside the central pipe, and a PVC inner layer is injection molded inside the end pipe openings.

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