A three-layer insulated wire forming manufacturing device and manufacturing method

Abstract

This invention relates to the field of cable manufacturing technology, specifically to a three-layer insulated wire forming manufacturing equipment and method. The equipment includes an extruder and a co-extrusion die, connected to each other. The co-extrusion die includes a die head, a mandrel, and a sleeve arranged coaxially from front to back. An outer die sleeve and an inner die sleeve are coaxially arranged inside the sleeve. An outer layer flow channel is formed between the outer wall of the outer die sleeve and the inner wall of the sleeve; a middle layer flow channel is formed between the inner wall of the outer die sleeve and the outer wall of the inner die sleeve; and an inner layer flow channel is formed between the inner wall of the inner die sleeve and the outer wall of the mandrel. The rear ends of the outer, middle, and inner layer flow channels are connected to the extruder via a feed pipe. This invention utilizes a buffer chamber and adjustment components to adaptively adjust the volume of the buffer chamber and the flow area of ​​the feed orifice based on the pressure changes of the recycled plastic melt, dynamically smoothing flow pressure fluctuations, avoiding interface disorder between heterogeneous melt layers, and ensuring the concentricity and thickness uniformity of the three-layer insulation.

Description

Technical Field

[0001] This invention relates to the field of cable manufacturing technology, specifically to a three-layer insulated wire forming and manufacturing equipment and method. Background Technology

[0002] Conventional triple-insulated cable forming and manufacturing equipment generally uses multi-layer co-extrusion die head assemblies as the positioning basis for plastic melt diversion and compounding. The multi-layer co-extrusion die head assembly consists of a coaxially nested die head body, diversion sleeve, core mold, and die sleeve. There are channel gaps between the components to allow the flow of virgin plastic melt and recycled plastic melt and the confluence of multiple layers. Although the structure of the multi-layer co-extrusion die head assembly is simple and reliable, when extruding triple-insulated wire with recycled plastic as the middle layer, under the high temperature and high pressure of unstable rheological properties of recycled plastic, the flow rate and channel pressure of the recycled material melt are prone to transient changes, thereby disrupting the interlayer pressure balance at the confluence of multiple layers. Moreover, when subsequent co-extrusion molding is carried out continuously or when the channel gap needs to be finely adjusted during the batch switching of recycled material, the fixed cross-section of each channel cannot make adaptive spatial changes. Pressure imbalance is very likely to leave structural defects such as uneven layer thickness, excessive eccentricity, or local thinning of the insulation layer inside the insulated cable.

[0003] To address the aforementioned issues, existing technologies offer several solutions, such as adjusting process parameters like extrusion temperature, screw speed, and feed rate, or incorporating mixing teeth and damping grooves on the surface of the manifold to reduce melt flow unevenness. However, these measures only mitigate the fluctuations, not eliminate them entirely; pressure imbalances still occur with prolonged continuous operation and frequent batch changes of recycled material. Another approach is to install a high-precision melt gear pump at the front of the die head to prevent the recycled material melt pressure from directly compressing the internal flow channels. While effective, this method significantly increases the overall mechanical dimensions of the equipment, manufacturing costs, and melt residence time, thus reducing production efficiency.

[0004] Therefore, there is a need for a three-layer insulated wire forming and manufacturing equipment that can eliminate the interference of recycled material flow pressure fluctuations on the internal multi-layer flow channel balance while ensuring stable extrusion molding, so as to adapt to the efficient and high-quality production of three-layer insulated wire thin-walled coating parts for high-frequency transformers that have strict requirements for electrical insulation quality. Summary of the Invention

[0005] The purpose of this invention is to provide a three-layer insulated wire forming and manufacturing equipment and method to solve the problem in the background art that the existing equipment cannot eliminate the interference of the flow pressure fluctuation of recycled plastic melt on the extrusion balance of the three-layer insulation layer, which easily leads to uneven layer thickness and substandard insulation performance of the formed insulation wire.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A three-layer insulated wire forming manufacturing equipment and method includes an extruder unit and a co-extrusion module. The extruder unit is connected to the co-extrusion module. The co-extrusion module includes a die head, a mandrel, and a sleeve arranged coaxially from front to back. An outer mold sleeve and an inner mold sleeve are coaxially arranged inside the sleeve. An outer flow channel is formed between the outer side wall of the outer mold sleeve and the inner side wall of the sleeve. A middle flow channel is formed between the inner side wall of the outer mold sleeve and the outer side wall of the inner mold sleeve. An inner flow channel is formed between the inner side wall of the inner mold sleeve and the outer side wall of the mandrel. The rear ends of the outer, middle, and inner flow channels are connected to the extruder unit through a feed pipe. A wire feeding channel is coaxially provided inside the mandrel. The middle flow channel is used for the flow of recycled plastic melt. A buffer chamber is provided on the rear side of the middle flow channel. An adjustment component is coaxially arranged in the buffer chamber. When pressure fluctuations occur in the feed pipe connected to the middle flow channel, the adjustment component adjusts the volume of the buffer chamber under the action of melt pressure.

[0007] By setting a buffer chamber and an adjustment component on the rear side of the middle layer flow channel, when the pressure fluctuation of the recycled plastic melt occurs in the feed pipe connected to the middle layer flow channel, the adjustment component is driven to move coaxially in the buffer chamber by the pressure change of the melt itself. This allows the adjustment component to adaptively adjust the volume in the buffer chamber, providing a dynamic volume buffer and release space for the recycled plastic melt. This avoids the recycled plastic melt from directly impacting the downstream co-extrusion junction under transient high pressure, effectively preventing the disorder of the interface between heterogeneous melt layers caused by flow field instability. Furthermore, when the melt pressure in the feed tube rises transiently, the volume of the buffer chamber increases synchronously to smooth out the pressure spikes. This ensures that during the co-extrusion of the three layers of melt in the outer, middle, and inner channels, the interfacial shear stress between the recycled material in the middle layer and the virgin materials in the inner and outer layers remains dynamically balanced. This avoids the problem of localized thinning of the inner and outer virgin material layers caused by the inability of existing equipment to eliminate the interference of recycled plastic melt pressure fluctuations on the extrusion balance of the three-layer insulation layer. This ensures the concentricity and thickness uniformity of the final three-layer insulation wire coating. Moreover, compared to external electronic sensors and active servo adjustment mechanisms, this adjustment component relies on the melt pressure itself for single-degree-of-freedom passive adaptive adjustment. This not only shortens the response time for pressure smoothing but also results in a more compact overall structure, reducing the failure rate of the precision extrusion die and facilitating subsequent cleaning and maintenance.

[0008] Preferably, the adjusting assembly includes a pressure ring, an adjusting screw, and a pressure spring. A melt channel is provided between the inner wall of the pressure ring and the inner wall of the buffer chamber. The pressure ring is coaxially disposed in the buffer chamber. Multiple through holes are arranged in a circumferential array on the front wall of the pressure ring. An adjusting screw is coaxially rotatably connected in each through hole. The adjusting screw is threaded to the rear end of the sleeve. The pressure spring is coaxially sleeved with the adjusting screw. The front and rear ends of the pressure spring are respectively connected to the front end of the screw and the front end face of the pressure ring. A feed hole is provided between the buffer chamber and the middle layer flow channel. A piston sleeve is provided at the front end of the pressure ring. When the pressure ring moves forward due to the melt pressure fluctuation in the feed pipe, the piston sleeve is embedded in the feed hole.

[0009] By installing an adjustment assembly including a pressure ring, adjusting screw, and pressure spring within the buffer chamber, when the pressure of the recycled plastic melt increases in the feed pipe connected to the buffer chamber, the high pressure of the melt pushes the pressure ring forward, overcoming the resistance of the pressure spring. This causes the piston sleeve at the front end of the pressure ring to embed into the feed hole, thereby reducing the flow channel area of ​​the feed hole and actively reducing the transient flow rate of the melt entering the middle layer channel. This effectively prevents the problem of excessive layer thickness caused by the sudden influx of high-pressure melt directly into the middle layer channel. Furthermore, when the pressure of the recycled plastic melt in the feed pipe decreases, the elastic potential energy of the pressure spring is released, driving the pressure ring to move backward. This causes the pressure ring to forcefully squeeze the buffer chamber behind it, adaptively discharging the temporarily stored melt in the buffer chamber to the front of the pressure ring through the first melt channel to form melt flow compensation. This ensures the continuity and stability of the melt flow rate when the middle layer supply pressure is insufficient, avoiding the problem of local thinning or even delamination of the insulation wire caused by intermittent recycled material or undervoltage in existing equipment, and ensuring a constant insulation layer thickness. Furthermore, by using multiple through holes in a circumferential array and coaxially rotating to connect the adjusting screws, not only can the initial axial position of the pressure ring be precisely and evenly adjusted through multiple screws, but also the circumferential constraint of multiple screws ensures that the pressure ring and the buffer cavity always have a very high degree of coaxiality when sliding back and forth along the axial direction, thereby reducing the risk of adjustment failure caused by mechanical eccentricity jamming.

[0010] Preferably, the rear end of the sleeve is provided with an overflow port, and an overflow valve is coaxially connected to the overflow port, the overflow valve being in communication with the regulating buffer chamber.

[0011] By setting an overflow port at the rear end of the sleeve and coaxially connecting it to an overflow valve, and ensuring that the overflow valve is connected to the interior of the buffer chamber, when the recycled plastic melt entering the buffer chamber experiences sudden extreme ultra-high pressure due to abnormal blockage of the flow channel or abnormal overload of the extruder, the overflow valve is directly activated by the melt's own pressure to unload the fluid nearby. This avoids the ultra-high pressure melt instantly suffocating the co-extrusion die head, effectively preventing die cracking or high-pressure ejection accidents caused by the transient pressure in the buffer chamber exceeding the mechanical pressure limit. Furthermore, when the melt pressure inside the buffer chamber exceeds the preset safety threshold of the overflow valve, the valve core inside the overflow valve automatically opens, directing the excess high-pressure recycled plastic melt outward through the overflow port to force pressure relief, ensuring that the core flow channel inside the co-extrusion module is always within a safe dynamic pressure range.

[0012] Preferably, the front end of the piston sleeve is provided with a conical flow surface, and the conical flow surface and the inner wall of the feed hole form a flow channel. When there is no pressure in the buffer chamber, the front end of the piston sleeve is not embedded in the feed hole.

[0013] By setting a conical flow surface at the front end of the piston sleeve, and ensuring that the front end of the piston sleeve is not embedded in the feed hole when there is no pressure in the buffer chamber, the tapered geometry of the conical flow surface provides smooth streamlined guidance for the recycled plastic melt during initial material entry or normal low-pressure flow. This avoids the high-viscosity melt from generating flow dead zones or severe local shear heat at the abrupt edge of the feed hole, effectively preventing the recycled plastic melt from degrading and carbonizing due to excessive residence time. Furthermore, when the pressure ring moves forward under pressure, the tapered flow surface can cut into the fluid along the flow trajectory of the melt, reducing the fluid displacement resistance during the forward movement of the piston sleeve. It can also guide excess melt to flow smoothly to both sides, reducing the transient fluid back-impact pressure on the front end of the piston sleeve. This ensures the high sensitivity response of the adaptive adjustment component under small pressure changes, avoiding the problem of lag in adaptive piston adjustment caused by excessive pressure resistance on the front end of the regulating valve core in existing equipment, or even the inability to move forward and throttle in time during sudden high pressure, thus ensuring the timeliness of flow feedback adjustment. Furthermore, compared to traditional flat-head plungers or abrupt intermittent valve cores, the conical flow surface of this invention cooperates with the inner wall of the feed hole, which allows the effective adjustment stroke of the flow channel between full opening and embedded throttling to be axially lengthened. This successfully transforms the steep abrupt adjustment of high-pressure melt into a smooth linear gradual adjustment, reducing the impact of drastic flow rate changes on the melt laminar flow state, and thus reducing the mechanical fatigue damage caused by the fluctuation stress of the flow field to the inside of the mold.

[0014] Preferably, the outer mold sleeve, inner mold sleeve and core mold are all provided with threaded guide grooves on their outer side walls, and the depth of the threaded guide grooves gradually decreases from back to front.

[0015] By providing threaded guide grooves on the outer walls of the outer mold sleeve, inner mold sleeve, and core mold, and making the groove depth gradually decrease from back to front, the threaded guide grooves are used to force the high-pressure melt to be diverted and sheared and reorganized circumferentially when the polymer plastic melt is conveyed forward along its respective flow channel. This avoids the uneven initial flow velocity of the melt caused by the unilateral feeding of the die head, and effectively prevents the weakening of the interlayer peel strength of the insulated cable due to the obvious confluence marks when the heterogeneous melts directly merge. Furthermore, as the depth of the threaded guide groove gradually decreases from back to front, the axial flow resistance in each layer of the flow channel increases continuously and uniformly, forcing the melt accumulated in the threaded groove to continuously overflow into the annular flow channel on the outer periphery. This achieves a smooth transition from rotational tangential flow to uniform axial laminar flow, ensuring that the outer, middle, and inner layers of melt establish a highly symmetrical circumferential pressure and velocity field before reaching the confluence point. This avoids the problem of local eccentricity and uneven layer thickness in extruded cables caused by the inability of existing equipment to eliminate the interference of the flow pressure fluctuation of recycled plastic melt on the extrusion balance of the three-layer insulation layer. This ensures the extreme precision of the concentricity and thickness distribution of the final three-layer insulation wire coating.

[0016] Preferably, a second melt channel is provided between the outer wall of the pressure ring and the outer wall of the buffer cavity, the sum of the passing areas of the first melt channel and the second melt channel is S1, and the passing area of ​​the feed hole is S2, where S1=S2.

[0017] By setting a second melt channel between the outer wall of the pressure ring and the outer wall of the buffer chamber, and making the sum of the passing areas S1 of the first and second melt channels equal to the passing area S2 of the feed hole, the symmetrical channel configuration with internal and external double-sided flow diversion uniformly guides the melt as it flows through the pressure ring. This avoids the pressure ring being subjected to unidirectional radial lateral pressure due to the melt flowing only from one side of the pressure ring, effectively preventing the pressure ring from becoming eccentrically tilted or mechanically jammed due to uneven force during axial sliding. Furthermore, by limiting the sum of the areas S1 of the two melt channels to be equal to the area S2 of the feed hole, the total cross-sectional area of ​​the flow channel when the polymer melt passes through this adjustment area remains constant. This ensures that the flow rate and shear rate of the recycled plastic melt in the buffer chamber have extremely high axial continuity, avoiding the problem of additional local resistance dissipation or sudden changes in flow velocity caused by sudden increases or decreases in the cross-sectional area of ​​the flow channel in existing equipment, which leads to turbulent melt flow field. This ensures the dynamic stability of the overall flow resistance of the middle layer feeding system.

[0018] Preferably, the rear end of the sleeve is provided with a feed hole, and there are two feed holes that communicate with the outer layer flow channel, the middle layer flow channel and the inner layer flow channel. The two feed holes that communicate with each flow channel are symmetrical to each other, and the horizontal projection of the two feed holes that communicate with the middle layer flow channel is within the horizontal projection of the pressure ring.

[0019] By providing multiple feed holes at the rear end of the sleeve, and ensuring that each feed hole communicating with the outer, middle, and inner flow channels has two holes that are symmetrical to each other, the extrusion pressure delivered from the external single side is evenly divided into a bidirectional counter-impacting balanced pressure during the initial injection of the three-way plastic melt. This avoids local eccentricity and flow deviation of the melt inside the co-extrusion die caused by a single feeding direction, and effectively prevents the mandrel inside the co-extrusion die from slight lateral unidirectional pressure caused by uneven initial feeding shear stress, thus preventing slight bending deformation.

[0020] Furthermore, since the horizontal projections of the two feed holes connected to the middle layer flow channel are within the horizontal projection of the pressure ring, the recycled plastic melt from the middle layer, fed in from the external feed pipe, can impact and act on the effective pressure surface of the pressure ring with the shortest axial path and directly facing it. This ensures that the transient pressure pulsation energy of the recycled plastic melt can be converted into mechanical power to push the pressure ring forward without loss and in real time. This avoids the problem in existing equipment where the high-pressure melt causes severe pressure dissipation in the dead corner inside the buffer chamber due to feed hole position offset, or the problem of severe lag in the response of the adaptive adjustment mechanism. This ensures the timely response of the adaptive flow adjustment of the middle layer flow channel.

[0021] Preferably, the method for manufacturing a three-layer insulated wire based on the above-described device includes the following steps: Step 1: Pull the metal wire core through the wire feeding channel inside the core mold; Step 2: The extrusion unit includes Extruder No. 1, Extruder No. 2 and Extruder No. 3. Extruder No. 1 feeds plastic melt into the outer layer flow channel through the feed pipe box, Extruder No. 3 feeds plastic melt into the inner layer flow channel through the feed pipe, and Extruder No. 2 feeds recycled plastic melt into the middle layer flow channel through the feed pipe. Step 3: When the pressure of the recycled plastic melt in the feed pipe connected to the middle layer flow channel increases, the recycled plastic melt pushes the pressure ring forward, the front end of the piston sleeve is embedded in the feed hole, and the flow area of ​​the flow channel decreases; when the pressure of the recycled plastic melt in the feed pipe connected to the middle layer flow channel decreases, the pressure ring moves backward under the elastic force of the pressure spring, and the flow area of ​​the flow channel increases. Step 4: The melt in the outer, middle and inner flow channels flows to the front end of the core mold, and the melt forms three insulating layers on the outside of the metal wire core. The formed three-layer insulated wire is then transported to the outside of the die head.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention, by setting up a buffer chamber and adjusting components, utilizes the pressure changes of the recycled plastic melt itself to adaptively adjust the internal volume of the buffer chamber and the flow area of ​​the feed hole, dynamically suppressing flow pressure fluctuations, avoiding interface disorder between heterogeneous melt layers, and ensuring the concentricity and thickness uniformity of the three insulating layers.

[0023] 2. By setting up a piston sleeve in conjunction with a conical flow surface structure, the invention transforms the steep abrupt change in the regulation of high-pressure melt into a smooth linear gradual change, reducing the impact of drastic changes in flow velocity on the laminar flow state of the melt. This avoids dead zones in the flow and melt degradation and carbonization, while ensuring the sensitivity and timeliness of adaptive regulation.

[0024] 3. This invention provides threaded guide grooves with gradually varying groove depths on the outer walls of the outer mold sleeve, inner mold sleeve, and core mold to perform circumferential forced diversion and shear reorganization of the melt, so that each layer of melt establishes a highly symmetrical circumferential pressure field and velocity field before merging, thereby further ensuring the concentricity and thickness accuracy of the coating layer. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the three-layer insulated wire forming and manufacturing equipment of the present invention; Figure 2 This is a rear view of a three-layer insulated wire forming and manufacturing equipment according to the present invention; Figure 3 for Figure 2 Full sectional view at point AA; Figure 4 for Figure 3 A magnified view of a section at point D; Figure 5 for Figure 2 Full sectional view at point BB; Figure 6 for Figure 5 A magnified view of a section at point E in the middle; Figure 7 for Figure 2 Full sectional view at point CC; Figure 8 for Figure 7 A magnified view of a section at point F in the middle; Figure 9 This is a schematic diagram of the adjustment component in this invention.

[0026] In the diagram: 1. Die head; 2. Core die; 3. Sleeve; 4. Inner die sleeve; 5. Outer die sleeve; 6. Outer flow channel; 7. Middle flow channel; 8. Inner flow channel; 9. Wire feeding channel; 10. Buffer chamber; 11. Pressure ring; 12. Adjusting screw; 13. Pressure spring; 14. No. 1 melt channel; 15. Feed hole; 16. Piston sleeve; 17. Overflow port; 18. Overflow valve; 19. Conical flow surface; 20. Flow channel; 21. Threaded guide groove; 22. No. 2 melt channel; 23. Feed hole; 24. Metal wire core; 25. Feed pipe. Detailed Implementation

[0027] Please see Figures 1 to 9This invention provides a three-layer insulated wire forming and manufacturing equipment and method, the technical solution of which is as follows: A three-layer insulated wire forming and manufacturing equipment. Figures 1 to 4 The system includes an extruder unit and a co-extrusion module. The extruder unit is connected to the co-extrusion module. The co-extrusion module includes a die head 1, a core die 2, and a sleeve 3 arranged coaxially from front to back. An outer die sleeve 5 and an inner die sleeve 4 are coaxially arranged inside the sleeve 3. An outer flow channel 6 is formed between the outer side wall of the outer die sleeve 5 and the inner side wall of the sleeve 3. A middle flow channel 7 is formed between the inner side wall of the outer die sleeve 5 and the outer side wall of the inner die sleeve 4. An inner flow channel 8 is formed between the inner side wall of the inner die sleeve 4 and the outer side wall of the core die 2. Threaded guide grooves 21 are provided on the outer side walls of the outer die sleeve 5, the inner die sleeve 4, and the core die 2. The depth of the threaded guide grooves 21 gradually decreases from back to front. The rear ends of the outer flow channel 6, the middle flow channel 7, and the inner flow channel 8 are connected to the extruder unit through a feed pipe 25. A feed hole 23 is provided at the rear end of the sleeve 3, which is connected to the outer flow channel 6, the middle flow channel 7, and the inner flow channel 8. Each of the three extruders has two feed holes 23, and the two feed holes 23 connected to each flow channel are symmetrical to each other. The horizontal projection of the two feed holes 23 connected to the middle flow channel 7 is within the horizontal projection of the pressure ring 11. The extruder unit includes a No. 1 extruder, a No. 2 extruder, and a No. 3 extruder. The No. 1 extruder feeds plastic melt into the outer flow channel 6 through the feed pipe 25 box, and the No. 3 extruder feeds plastic melt into the inner flow channel 8 through the feed pipe 25. The No. 2 extruder feeds recycled plastic melt into the middle flow channel 7 through the feed pipe 25. The core mold 2 has a wire feeding channel 9 coaxially arranged inside. The middle flow channel 7 is used for the flow of recycled plastic melt. A buffer chamber 10 is provided on the rear side of the middle flow channel 7. An adjustment component is coaxially arranged in the buffer chamber 10. When pressure fluctuation occurs in the feed pipe 25 connected to the middle flow channel 7, the adjustment component adjusts the volume in the buffer chamber 10 under the action of melt pressure.

[0028] Figures 2 to 9The adjustment assembly includes a pressure ring 11, an adjusting screw 12, and a pressure spring 13. A first melt channel 14 is provided between the inner wall of the pressure ring 11 and the inner wall of the buffer cavity 10, and a second melt channel 22 is provided between the outer wall of the pressure ring 11 and the outer wall of the buffer cavity 10. The pressure ring 11 is coaxially disposed within the buffer cavity 10. Multiple through holes are arranged in a circumferential array on the front wall of the pressure ring 11, and an adjusting screw 12 is coaxially rotatably connected to each through hole. The adjusting screw 12 is threadedly connected to the rear end of the sleeve 3. The pressure spring 13 is coaxially sleeved with the adjusting screw 12. The front and rear ends of the pressure spring 13 are connected to the front end of the screw and the front end face of the pressure ring 11, respectively. A feed hole 15 is provided between the buffer chamber 10 and the middle layer flow channel 7. The sum of the passing areas of the first melt channel 14 and the second melt channel 22 is S1, and the passing area of ​​the feed hole 15 is S2, where S1=S2. A piston sleeve 16 is provided at the front end of the pressure ring 11. A conical flow surface 19 is provided at the front end of the piston sleeve 16. A flow channel 20 is formed between the conical flow surface 19 and the inner wall of the feed hole 15. When there is no pressure in the buffer chamber 10, the front end of the piston sleeve 16 is not embedded in the feed hole 15. When the pressure ring 11 moves forward due to the fluctuation of the melt pressure in the feed pipe 25, the piston sleeve 16 is embedded in the feed hole 15. An overflow port 17 is provided at the rear end of the sleeve 3. An overflow valve 18 is coaxially connected to the overflow port 17 and communicates with the regulating buffer chamber 10.

[0029] For a method of forming and manufacturing a three-layer insulated wire using the above-mentioned equipment, please refer to [link / reference]. Figures 1 to 9 The specific steps are as follows: Step 1: The traction metal wire core 24 is guided into the wire feeding channel 9 inside the core mold 2 through the wire threading mechanism, and the traction is maintained at a constant speed while waiting for extrusion and coating. Step 2: Start extruder No. 1, extruder No. 2 and extruder No. 3 in sequence. Extruder No. 1 conveys the new insulating plastic melt to the outer layer flow channel 6 through the symmetrical feed holes 23. Extruder No. 3 conveys the inner layer insulating plastic melt to the inner layer flow channel 8 through the symmetrical feed holes 23. Extruder No. 2 conveys the pre-treated recycled plastic melt to the buffer chamber 10 of the middle layer flow channel 7 through the symmetrical feed holes 23. Step 3: When the discharge fluctuation of the No. 2 extruder causes the pressure of the recycled plastic melt in the buffer chamber 10 to rise, the high-pressure melt pushes the pressure ring 11 to move forward against the elastic force of the pressure spring 13. The front end of the piston sleeve 16 gradually embeds into the feed hole 15, reducing the passing area of ​​the flow channel 20 and decreasing the melt flow rate entering the middle layer flow channel 7. When the melt pressure in the buffer chamber 10 drops, the pressure spring 13 pushes the pressure ring 11 to reset backward, and the piston sleeve 16 gradually withdraws from the feed hole 15. The passing area of ​​the flow channel 20 increases, increasing the melt flow rate entering the middle layer flow channel 7, thus completing the adaptive dynamic adjustment of the middle layer melt flow rate. When the transient pressure in the buffer chamber 10 exceeds the preset threshold of the overflow valve 18, the overflow valve 18 automatically opens to discharge excess melt and force pressure relief. Step 4: After the outer, middle, and inner layers of melt are diverted and homogenized by the threaded guide grooves 21 on the corresponding flow channels, they are conveyed to the front end of the core mold 2 to converge. They are then sequentially wrapped around the outside of the uniformly moving metal wire core 24 to form an inner insulation layer, a middle recycled insulation layer, and an outer brand new insulation layer. Finally, the three-layer insulation wire is pulled out of the die head 1 to complete the cooling and winding.

[0030] By leveraging the pressure pulsations of the recycled plastic melt itself, the pressure ring 11 is directly driven to achieve adaptive flow regulation, eliminating the need for additional power drive or sensor control modules. When the No. 2 extruder experiences pressure fluctuations due to uneven viscosity of the recycled plastic melt, the pressure ring 11 directly responds to the pressure change by adjusting the flow area in real time. This dynamically smooths out the flow fluctuations of the melt entering the middle layer channel 7, preventing pressure fluctuations of the recycled plastic from interfering with the co-extrusion balance of the three-layer melt and ensuring uniform and concentric thickness of each layer of the insulation wire. Simultaneously, the two-stage homogenization achieved through the conical flow surface 19 and the gradually changing deep threaded guide groove 21 ensures a stable and symmetrical flow field for each layer of melt, transforming abrupt pressure regulation into smooth linear regulation. This further reduces the impact of flow field fluctuations on extrusion molding accuracy, effectively solving the problems of uneven layer thickness and excessive concentricity that easily occur when reusing recycled plastic to form three-layer insulation wires. This improves the utilization rate of recycled plastic and reduces production costs while ensuring the performance of the insulation wire product.

[0031] The specific embodiment of the present invention has been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the embodiments described above. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and ideas of the present invention should still fall within the protection scope of the present invention.

Claims

1. A three-layer insulated wire forming and manufacturing equipment, comprising an extruder unit and a co-extrusion die, wherein the extruder unit and the co-extrusion die are connected, characterized in that, The co-extrusion module includes a die head (1), a core die (2), and a sleeve (3) arranged coaxially from front to back. An outer die sleeve (5) and an inner die sleeve (4) are coaxially arranged inside the sleeve (3). An outer flow channel (6) is formed between the outer sidewall of the outer die sleeve (5) and the inner sidewall of the sleeve (3). A middle flow channel (7) is formed between the inner sidewall of the outer die sleeve (5) and the outer sidewall of the inner die sleeve (4). An inner flow channel (8) is formed between the inner sidewall of the inner die sleeve (4) and the outer sidewall of the core die (2). The outer flow channel (6), middle flow channel (7), and inner flow channel (8) are connected in a series. The rear ends of the laminar flow channel (7) and the inner flow channel (8) are connected to the extruder unit through the feed pipe (25). The core mold (2) is coaxially provided with a wire feeding channel (9). The middle flow channel (7) is used for the flow of recycled plastic melt. The rear side of the middle flow channel (7) is provided with a buffer chamber (10). An adjustment component is coaxially provided in the buffer chamber (10). When pressure fluctuation occurs in the feed pipe (25) connected to the middle flow channel (7), the adjustment component adjusts the volume in the buffer chamber (10) under the action of melt pressure.

2. The three-layer insulated wire forming and manufacturing equipment according to claim 1, characterized in that, The adjustment assembly includes a pressure ring (11), an adjusting screw (12), and a pressure spring (13). A melt channel (14) is provided between the inner wall of the pressure ring (11) and the inner wall of the buffer cavity (10). The pressure ring (11) is coaxially arranged in the buffer cavity (10). Multiple through holes are arranged in a circular array on the front side wall of the pressure ring (11). An adjusting screw (12) is coaxially rotatably connected in each through hole. The adjusting screw (12) is connected to the rear of the sleeve (3). The pressure spring (13) and the adjusting screw (12) are coaxially sleeved. The front and rear ends of the pressure spring (13) are respectively connected to the front end of the screw and the front end face of the pressure ring (11). A feed hole (15) is provided between the buffer cavity (10) and the middle layer flow channel (7). A piston sleeve (16) is provided at the front end of the pressure ring (11). When the pressure ring (11) moves forward due to the fluctuation of the melt pressure in the feed pipe (25), the piston sleeve (16) is embedded in the feed hole (15).

3. The three-layer insulated wire forming and manufacturing equipment according to claim 2, characterized in that, The sleeve (3) has an overflow port (17) at its rear end. An overflow valve (18) is coaxially connected to the overflow port (17). The overflow valve (18) is connected to the regulating buffer chamber (10).

4. The three-layer insulated wire forming and manufacturing equipment according to claim 2, characterized in that, The piston sleeve (16) has a conical flow surface (19) at its front end. The conical flow surface (19) and the inner wall of the feed hole (15) form a flow channel (20). When there is no pressure in the buffer chamber (10), the front end of the piston sleeve (16) is not embedded in the feed hole (15).

5. The three-layer insulated wire forming and manufacturing equipment according to claim 1, characterized in that, The outer mold sleeve (5), inner mold sleeve (4) and core mold (2) are all provided with threaded guide grooves (21) on their outer side walls. The depth of the threaded guide grooves (21) gradually decreases from back to front.

6. The three-layer insulated wire forming and manufacturing equipment according to claim 2, characterized in that, A second melt channel (22) is provided between the outer wall of the pressure ring (11) and the outer wall of the buffer cavity (10). The sum of the passing areas of the first melt channel (14) and the second melt channel (22) is S1, and the passing area of ​​the feed hole (15) is S2, where S1 = S2.

7. The three-layer insulated wire forming and manufacturing equipment according to claim 6, characterized in that, The sleeve (3) has a feed hole (23) at its rear end. There are two feed holes (23) that are connected to the outer flow channel (6), the middle flow channel (7) and the inner flow channel (8). The two feed holes (23) connected to each flow channel are symmetrical to each other. The horizontal projection of the two feed holes (23) connected to the middle flow channel (7) is within the horizontal projection of the pressure ring (11).

8. A method for manufacturing a three-layer insulated wire based on the device described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Pull the metal wire core (24) through the wire feeding channel (9) inside the core mold (2); Step 2: The extrusion unit includes Extruder 1, Extruder 2 and Extruder 3. Extruder 1 feeds plastic melt into the outer layer flow channel (6) through the feed pipe (25), Extruder 3 feeds plastic melt into the inner layer flow channel (8) through the feed pipe (25), and Extruder 2 feeds recycled plastic melt into the middle layer flow channel (7) through the feed pipe (25). Step 3: When the pressure of the recycled plastic melt in the feed pipe (25) connected to the middle layer flow channel (7) increases, the recycled plastic melt pushes the pressure ring (11) forward, the front end of the piston sleeve (16) is embedded in the feed hole (15), and the passage area of ​​the flow channel (20) decreases; when the pressure of the recycled plastic melt in the feed pipe (25) connected to the middle layer flow channel (7) decreases, the pressure ring (11) moves backward under the elastic force of the pressure spring (13), and the passage area of ​​the flow channel (20) increases; Step 4: The melt in the outer layer flow channel (6), middle layer flow channel (7) and inner layer flow channel (8) flows to the front end of the core mold (2). The melt forms a three-layer insulation layer on the outside of the metal wire core (24). The formed three-layer insulation wire is transported to the outside of the mold head (1).

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