Three-layer co-extruded tube and co-extrusion head

Abstract

The application provides a three-layer co-extrusion pipe and a co-extrusion head to at least solve the pipe connection technical problem in the prior art. According to the co-extrusion pipe, a marking layer is coated outside a co-extrusion layer, the marking layer is formed by extrusion molding of a first material and a second material, the first material and the second material have different colors, the first material and the second material are arranged at intervals along the axial direction of the co-extrusion pipe at least at the end surface of the co-extrusion pipe, and the first material and the second material have a joint line or a transition zone at the joint position. The depth of the co-extrusion pipe inserted into the connecting seat when connected can be identified according to the color of the marking layer and the position of the joint line, the depth of the insertion is ensured to meet the requirements, and when different pipes are simultaneously constructed, it is not necessary to observe whether the end surfaces are flush, but the relative position of the joint line or the transition zone can be directly observed, the insertion is in place, the end surface of the co-extrusion pipe is more flush, and the co-extrusion pipe connection is more firm.

Description

Technical Field

[0001] This application relates to the field of power pipelines, and in particular to three-layer co-extruded pipes and co-extrusion die heads. Background Technology

[0002] Currently, most traditional power and communication conduits on the market are single-layer structures made of ordinary PVC, PE, and other materials. Under complex working conditions such as high humidity, acid and alkali corrosion, long-term ultraviolet radiation, bridge mounting, and underground tunneling, they are prone to accelerated aging and pipe wall degradation and embrittlement. The single-layer structure not only has a high coefficient of friction during cable installation, easily damaging optical and electrical cables, but also frequently causes cable short circuits due to pipe leakage, severely shortening the designed service life of the cables. Furthermore, some conduits have drawbacks such as poor environmental performance, high energy consumption, and inconvenient construction. In addition, the requirements for the protection of power and communication cables are even higher in complex and harsh environments such as urban underground integrated pipe corridors, power transmission and distribution networks, highway cable laying, and marine energy development.

[0003] Co-extruded pipes are made by extruding at least two materials simultaneously. This not only creates a double or multi-layer structure, but also prevents delamination when multiple materials are mixed locally, resulting in higher pipe strength. Furthermore, the outer layer is usually made of aging-resistant materials, which can extend the service life of the pipe and meet the protection requirements of power and communication cables.

[0004] Due to transportation limitations, the length of a single pipeline is finite. During pipeline construction, multiple pipeline sections need to be connected using connectors. Because the outer wall of the pipeline is a single color, it is difficult to judge the insertion depth at the insertion point. Therefore, different pipelines may be inserted into the connector to different depths during construction. Multiple pipelines are often installed side-by-side, resulting in different pipeline ends being on different planes, requiring cutting or other operations, which inconveniences the construction process. Furthermore, insufficient insertion depth may cause the pipeline to detach later, allowing rainwater or foreign objects to enter and affecting normal pipeline use. Adding markings to the outside of the pipeline increases manufacturing costs, and using markers during construction increases labor costs.

[0005] Chinese patent application CN201934807U, entitled "Three-Layer Co-Extruded PE Pipe," discloses a three-layer co-extruded PE pipe. The pipe wall consists of three layers: a protective layer, a supporting layer, and a non-toxic anti-corrosion layer, from the outside in. This utility model uses three materials with different chemical properties and prices for co-extrusion. Furthermore, the outer wall of the pipe is a single color, and the insertion depth cannot be observed from the outside when using the connector, failing to address the issue of pipe marking.

[0006] Chinese patent application CN2751539Y, entitled "Three-Layer Co-Extruded Drip Irrigation Pipe," discloses a three-layer co-extruded drip irrigation pipe manufactured using a co-extrusion process with three extruders. The pipe has an outlet at the junction of the dripper's outlet window and the pipe wall. Its key feature is that the pipe wall is composed of a waterproof layer, a foaming layer, and an anti-aging layer. However, this patent also features a single-color outer wall for the pipe, making it impossible to observe the insertion depth from the outside when using the connector, and it fails to address the issue of pipe marking.

[0007] Chinese patent application CN2336949Y, entitled "Three-Layer Co-Extrusion Die Head," discloses a processing and forming device for three-layer plastic composite pipes. It consists of an extruder middle, inner, and outer layer connecting body, a die head body, a flow divider cone, middle, inner, and outer layer dies, a mandrel, and multiple flow channels within the die head. Notably, this die head features three independent flow channels, with independent material supply from each of the three extruders. The rational arrangement of the flow channel feed angles effectively overcomes the shortcomings of existing technologies, enabling the production of various three-layer composite pipes composed of materials A, B, and C. Furthermore, the thickness of each layer can be individually adjusted, improving production efficiency and enhancing the physical properties and appearance quality of the pipe. This patent primarily produces ordinary three-layer pipes, and the insertion depth of the produced pipes cannot be directly identified by visual inspection of the outer wall. Utility Model Content

[0008] This application provides a three-layer co-extruded tube and a co-extrusion die head to at least solve the pipe connection technology problems existing in the prior art.

[0009] According to a first aspect of this application, a co-extruded tube is provided, including a marking layer and a co-extruded layer, the marking layer covering the co-extruded layer, the marking layer being extruded using a first material and a second material, the first material and the second material having different colors, the first material and the second material being spaced apart at least on the end surface of the co-extruded tube along the axial direction of the co-extruded tube, and the junction of the first material and the second material having a junction line or transition zone.

[0010] Compared with the prior art, the co-extruded tube of this application has the following advantages: The depth to which the co-extruded pipe is inserted into the connector during connection can be identified by the color of the marking layer and the position of the boundary line. This ensures that the insertion depth meets the requirements. When different pipes are installed simultaneously, there is no need to observe whether the ends are flush; simply check the relative position of the boundary line or transition zone. For example, the length of the boundary line or transition zone from the end face can be set as the length of the connector insertion. In this way, the insertion depth can be quickly determined by whether the boundary line or transition zone is obstructed, eliminating the need to judge the insertion depth from the other end of the co-extruded pipe. Proper insertion not only makes the end faces of the co-extruded pipe more flush but also makes the co-extruded pipe connection more secure, preventing external factors from affecting the connection and better protecting the cables inside the co-extruded pipe. It also prevents foreign objects from entering the co-extruded pipe and affecting its use.

[0011] In one embodiment, the marking layer has a substrate ring, and the substrate ring and the co-extruded layer are made of the same second material.

[0012] In one embodiment, the marking layer is provided with a marking ring, which is formed by extrusion molding of a first material.

[0013] In one embodiment, a transition ring is provided between the substrate ring and the marking ring.

[0014] In one embodiment, the cross-section of the marking ring is rectangular, triangular, semi-circular, trapezoidal, or semi-circular groove.

[0015] In one embodiment, the marking layer includes a first annular region and a second annular region, wherein the number of marking rings in the first annular region is different from the number of marking rings in the second annular region.

[0016] In one embodiment, the co-extruded tube is provided with a cutting area, which is provided with a marking reference cutting end and a length reference cutting end.

[0017] According to a second aspect of this application, a three-layer co-extruded tube is provided, which adopts the above-mentioned co-extruded tube structure and further includes a grooved layer located inside the co-extruded layers.

[0018] In one embodiment, the cable tray layer is provided with straight grooves, wavy grooves, or spiral grooves, which are evenly distributed on the inner wall of the three-layer co-extruded tube. The cable tray can reduce the contact area and prevent the cable from sticking to the inner wall of the three-layer co-extruded tube.

[0019] According to a third aspect of this application, a co-extrusion die head for a three-layer co-extrusion tube is provided, comprising a core die, an outer die, an outer runner ring, an inner runner ring, a core runner ring, a first pair of interfaces, a second pair of interfaces, and a frame. A forming channel is formed between the core die and the outer die. A marking injection channel is formed between the inner runner ring and the outer runner ring. A co-extrusion injection channel is formed between the core runner ring and the inner runner ring. The marking injection channel is connected to the first pair of interfaces. The co-extrusion injection channel is connected to the second pair of interfaces. A grooved injection channel is formed between the core runner ring and the frame. The grooved injection channel is connected to a third injection port. The forming channel is connected to the marking injection channel, the grooved injection channel, and the co-extrusion injection channel. The marking injection channel is provided with a valve structure or a negative pressure backflow structure, which controls the flow of a first material within the marking injection channel.

[0020] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this application, nor is it intended to limit the scope of this application. Other features of this application will become readily apparent from the following description. Attached Figure Description

[0021] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of this application are illustrated in the drawings by way of example and not limitation, in which: In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0022] Figure 1 A three-dimensional schematic diagram of the co-extruded tube according to Embodiment 1 of this application is shown; Figure 2 A half-sectional schematic diagram of the co-extruded tube of Embodiment 1 of this application is shown; Figure 3 A half-sectional schematic diagram of the co-extruded tube according to Embodiment 2 of this application is shown; Figure 4 A three-dimensional schematic diagram of the co-extruded tube according to Embodiment 3 of this application is shown; Figure 5 A half-sectional schematic diagram of the co-extruded tube of Embodiment 3 of this application is shown; Figure 6 A three-dimensional schematic diagram of the co-extruded tube according to Embodiment 4 of this application is shown; Figure 7 A three-dimensional schematic diagram of the co-extruded tube according to Embodiment 5 of this application is shown; Figure 8 A schematic diagram of the composition of the co-extrusion tube manufacturing apparatus according to Embodiment 6 of this application is shown; Figure 9 A rear view schematic diagram of the co-extrusion tube manufacturing apparatus according to Embodiment 6 of this application is shown; Figure 10 It shows Figure 9A half-section diagram at point AA in the middle; Figure 11 It shows Figure 9 A half-section diagram at point BB; Figure 12 A schematic diagram of the internal structure of the co-extruded tube manufacturing apparatus according to Embodiment 6 of this application is shown; Figure 13 A schematic diagram of the rear outer mold and annular piston of the co-extrusion tube manufacturing apparatus of Embodiment 6 of this application is shown; Figure 14 A schematic diagram of the rear outer mold of the co-extrusion tube manufacturing apparatus according to Embodiment 6 of this application is shown; Figure 15 It shows Figure 10 Enlarged view of a portion of point E in the middle; Figure 16 This diagram shows a partially enlarged view of point E under negative pressure conditions generated by the annular piston. Figure 17 A perspective view of the co-extrusion tube manufacturing apparatus of Embodiment 7 of this application is shown; Figure 18 A rear view schematic diagram of the co-extrusion tube manufacturing apparatus according to Embodiment 7 of this application is shown; Figure 19 It shows Figure 18 A half-section diagram at point CC; Figure 20 The co-extrusion tube manufacturing apparatus under atmospheric pressure is shown. Figure 18 A half-section diagram at point DD; Figure 21 The co-extrusion tube manufacturing apparatus is shown under pressure. Figure 18 A half-section diagram at point DD; Figure 22 It shows Figure 21 A magnified view of a portion of point F in the middle.

[0023] Explanation of the labels in the diagram: X, first direction; Y, second direction; Z, third direction; 1. Core mold; 2. Outer mold; 3. Outer runner ring; 4. Inner runner ring; 5. Core runner ring; 6. Frame; 7. First pair of interfaces; 8. Second pair of interfaces; 9. Third pair of interfaces; 10. Threaded connector; 11. Molding channel; 12. Co-extrusion injection channel; 13. Marking injection channel; 14. Groove injection channel; 15. Valve structure; 16. Negative pressure return structure; 17. Positive pressure propulsion structure; 18. Pressure stabilizing chamber; 19. Outer core mold; 20. Inner core mold; 21. Front outer mold; 22. Rear outer mold; 23. Connecting cavity; 24. Annular piston; 25. Annular part; 26. Transmission part; 27. External thread; 28. Threaded sleeve; 29. ​​Bevel gear; 30. Protective shell; 31. Cavity; 32. Annular cavity; 33. First driving part; 34. First driving component; 35. First material; 36. Third material; 37. Second material; 38. Tapered segment; 39. Tubular piston; 40. Elastic reset component; 41. Small protrusion; 141. Marking layer; 142. Co-extruded layer; 143. Groove layer; 144. End surface; 145. Substrate ring; 146. Marking ring; 147. Transition ring; 148. First annular region; 149. Second annular region; 150. Straight groove; 151. Wavy groove; 152. Spiral groove; 153. Marking point; 154. Cutting area; 155. Marking reference cutting end; 156. Length reference cutting end. Detailed Implementation

[0024] To make the objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] Example 1: like Figure 1 and Figure 2 As shown, a co-extruded tube is manufactured using the method or apparatus of Example 1 or 2.

[0026] like Figure 1 and Figure 2As shown, the three-layer co-extruded tube includes a marking layer 141, a co-extruded layer 142, and a grooved layer 143. The marking layer 141 covers the co-extruded layer 142. The marking layer 141 is extruded using a first material 35 and a second material 37. The first material 35 and the second material 37 have different colors. The first material 35 and the second material 37 are spaced apart along the axial direction of the co-extruded tube at least on the end surface 144 of the co-extruded tube. The junction of the first material 35 and the second material 37 has a junction line or transition area, which is a junction line or transition area naturally formed by different colored materials. The grooved layer 143 is located inside the co-extruded layer 142. The co-extruded layer 142 is made of the second material 37, and the grooved layer 143 is made of the third material.

[0027] like Figure 1 and Figure 2 As shown, in one embodiment, the marking layer 141 is provided with a substrate ring 145, and the substrate ring 145 and the co-extruded layer 142 are made of the same second material 37.

[0028] like Figure 1 and Figure 2 As shown, in one embodiment, the marking layer 141 is provided with a marking ring 146, which is extruded from a first material 35.

[0029] like Figure 1 and Figure 2 As shown, in one embodiment, the marking layer 141 includes a first annular region 148 and a second annular region 149. The number of marking rings 146 in the first annular region 148 is different from the number of marking rings 146 in the second annular region 149. The marking layer 141 mainly covers the first material 35, and the second material 37 forms five annular structures, that is, three at the upper end and two at the lower end. In one embodiment, the different widths of the upper and lower marking rings 146 make the overall width of the marking area the same.

[0030] like Figure 1 and Figure 2 As shown, in one embodiment, the groove layer 143 is provided with straight grooves 150, which are evenly distributed on the inner wall of the three-layer co-extruded tube.

[0031] like Figure 2 As shown, in one embodiment, the marking ring 146 has a triangular cross-section.

[0032] JT-HPO pipe is a high-strength, aging-resistant three-layer oriented co-extruded pipe. Its core is a three-layer co-extruded structure: the outer layer blocks environmental corrosion, the middle layer provides structural support, and the inner layer optimizes cable-laying performance. These three layers work together to achieve integrated protection, strength, and function, overcoming the shortcomings of traditional single-layer pipes that excel in only one specific performance characteristic but lack comprehensive overall performance. The material and process parameters for each layer are as follows: Preparation of Marking Layer 141: The first material 35 is a UV-resistant composite polymer resin (with added nano-level antioxidants and UV absorbers). After being melted in a co-extrusion machine, it is coated on the outside of the co-extruded layer 142 with a thickness of 1.5-3.0 mm. A nano-dispersion process is used to ensure uniform distribution of additives. After cooling, a purple outer protective layer is formed. The color change level is ≥4 and the tensile retention rate is ≥95%. Compared with traditional pipes, the aging resistance life is extended by more than 3 times. It can adapt to low temperature to high temperature environments from -30℃. There is no performance degradation under strong acid and alkali and ultraviolet radiation. The cable length is increased by 50%, the number of inspection wells used is reduced by 30%, and the construction cost is reduced.

[0033] Preparation of co-extruded layer 142: The second material 37 is a mixed material, in which high-performance PVC resin and CPVC resin are mixed in a ratio of 9:1 to 7:3, with the addition of modifiers, toughening agents, and stabilizers. The mixture is melted in a twin-screw extruder to form a pipe blank. The pipe blank is then subjected to axial and circumferential stretching (stretch ratio 1:2.5) using a biaxial orientation device to form a molecular network structure. After cooling, the wall thickness of the intermediate layer is controlled at 2.0-10.0 mm (adjusted according to the nominal outer diameter). The ring stiffness is tested to be ≥10-50 KN / ㎡, and the Vicat softening temperature is ≥93℃ for Type I, ≥105℃ for Type II, ≥120℃ for Type III, and ≥135℃ for Type IV. The maximum ring stiffness reaches 50 KN / ㎡, and the tensile strength is ≥45 MPa (circumferential) and ≥52 MPa (longitudinal). Impact resistance is improved by 10 times, preventing pipe wall brittleness. Material savings exceed 20%, and energy consumption and carbon emissions are reduced by 15%, meeting the requirements of green and sustainable development.

[0034] Fabrication of Cable Tray Layer 143: The silicon core layer is processed on the inner wall of the cable tray layer 143 using a laser etching machine (50W power, 0.05mm etching depth). After etching, the static friction coefficient of the inner wall is ≤0.2. After three-layer co-extrusion molding, it is processed into a flared plug-in structure by a flaring machine, or it can be directly plugged in. The length is cut into 6m, 9m, or 12m specifications. This significantly reduces cable pulling resistance, eliminates the risk of cable scratches, allows a single person to complete long-distance cable pulling operations, and improves construction efficiency by 40%. The silicon core layer is tightly bonded to the pipe body, and its service life is synchronized with the pipe body, eliminating subsequent maintenance costs.

[0035] The marking layer 141 achieves a color change level ≥4 and a tensile retention rate ≥95% through optimized formulation of composite polymer materials; the intermediate layer improves ring stiffness by 50%, tensile strength by 50%, Vicat softening temperature by 20%-30%, and impact resistance by more than 10 times through biaxial orientation process; the inner silicon core layer reduces the coefficient of friction by 80% through precise control of surface roughness by laser etching.

[0036] For highway cable laying, JT-HPO pipes with a nominal outer diameter of 110mm and a wall thickness of 4.9mm (ring stiffness ≥32KN / ㎡) are selected. They are directly buried underground using plug-in connections. The cables are lightweight, easy to handle, and easy to connect, requiring no mechanical assistance and reducing construction costs. The low friction coefficient of the inner layer ensures a single cable length of up to 100m, eliminating the need for additional inspection wells. The UV-resistant surface layer prevents aging issues associated with open-air laying, while the high-strength middle layer withstands soil pressure from vehicle traffic.

[0037] Example 2: like Figure 3 As shown, the difference from Embodiment 3 is that the groove layer 143 is provided with corrugated grooves 151, which are evenly distributed on the inner wall of the three-layer co-extruded tube. In one embodiment, the marking ring 146 has a semi-circular waist-groove cross-section, which facilitates molding. The co-extruded layer 142 is made of the first material 35, and the marking layer 141 is formed by alternating the first material 35 and the color material.

[0038] Example 3: like Figure 4 and Figure 5 As shown, the difference from Embodiment 3 is that the groove layer 143 is provided with spiral grooves 152, which are evenly distributed on the inner wall of the three-layer co-extruded tube. In one embodiment, the marking ring 146 has a rectangular cross-section. Figure 4 As shown, in one embodiment, a transition ring 147 is provided between the substrate ring 145 and the marking ring 146.

[0039] Example 4: like Figure 6 As shown, the difference from Example 3 is that the marking ring 146 is not set, but the marking point 153 is set. The marking point 153 is made of different materials co-extruded on the outside of the pipe wall, and the material can be fed intermittently.

[0040] Example 5: like Figure 7 As shown, the difference from Embodiment 3 is that the co-extruded tube is provided with a cutting area 154, which is provided with a marking reference cutting end 155 and a length reference cutting end 156. That is, cutting is first performed according to the position of the marking ring 146. The position of the marking ring 146 can be automatically identified by an artificial intelligence image or color recognition device to cut the marking reference cutting end 155, or it can be cut manually. Then, the length reference cutting end 156 is cut according to the length. This ensures that the position of the marking ring 146 is more accurate and that the co-extruded tube has the same length.

[0041] Example 6: refer to Figure 8 , Figure 9 , Figure 10 and Figure 11A co-extrusion tube manufacturing apparatus is disclosed, primarily for forming three-layer co-extruded tubes. The co-extrusion tube manufacturing apparatus of this embodiment includes a co-extrusion die head, a first injection molding machine, a second injection molding machine, and a third injection molding machine. The first, second, and third injection molding machines are purchased ordinary injection molding machines and are therefore not shown. The injection speeds of the first, second, and third injection molding machines are related to the size and thickness of the co-extruded tube. The co-extrusion die head is provided with a core mold 1, an outer mold 2, an outer runner ring 3, an inner runner ring 4, a core runner ring 5, a first coupling 7, a second coupling 8, a third coupling 9, and a frame 6. The first coupling 7, second coupling 8, and third coupling 9 are each provided with threaded holes. The first coupling 7 is located in the third direction or at a certain angle to the third direction, the second coupling 8 is located in the first direction, and the third coupling 9 is located in the second direction. The first injection molding machine connects to the first coupling 7 via a threaded coupling pipe 10, the second injection molding machine connects to the second coupling 8 via the threaded coupling pipe 10, and the third injection molding machine connects to the third coupling 9 via the threaded coupling pipe 10. 9. A forming channel 11 is formed between the core mold 1 and the outer mold 2. A marking injection channel 13 is formed between the inner flow channel ring 4 and the outer flow channel ring 3. A co-extrusion injection channel 12 is formed between the inner flow channel ring 4 and the core flow channel ring 5. A grooved injection channel 14 is formed between the core flow channel ring 5 and the frame 6. The marking injection channel 13 is connected to the first pair of interfaces 7. The co-extrusion injection channel 12 is connected to the second pair of interfaces 8. The grooved injection channel 14 is connected to the third pair of interfaces 9. The forming channel 11 is connected to the marking injection channel 13, the grooved injection channel 14, and the co-extrusion injection channel 12. The marking injection channel 13 is equipped with a valve structure 15 or a negative pressure backflow structure 16. The valve structure 15 controls the flow of the first material in the marking injection channel 13 or the forming channel 11. Alternatively, the forming channel 11 is equipped with a positive pressure propulsion structure 17 and a pressure stabilizing chamber 18. The pressure stabilizing chamber 18 is located on the side closer to the marking injection channel 13, and the positive pressure propulsion structure 17 is located on the side away from the marking injection channel 13. The first direction is axially upward, and the first direction, the second direction, and the third direction are perpendicular to each other. The frame 6 is equipped with multiple mounting holes for easy installation on other structures.

[0042] refer to Figure 8 , Figure 10 and Figure 11To facilitate processing and installation, and to form co-extruded tubes of different sizes, the outer mold 2 includes a front outer mold 21 and a rear outer mold 22, which are arranged along a first direction. For ease of processing, the main structure of the front outer mold 21 and the rear outer mold 22 is a rotating structure. The core mold 1 includes an outer core mold 19 and an inner core mold 20, with the outer core mold 19 fitted onto the inner core mold 20. Different inner core molds 20 and front outer molds 21 can be used to produce different types of co-extruded tubes. In some embodiments, the inner core mold 20 needs to be able to rotate relative to the outer core mold 19; therefore, the inner core mold 20 passes through the center hole of the frame 6 and has a drive structure at its end. Biaxial orientation requires axial and circumferential stretching of the tube blank; therefore, the forming channel 11 between the outer mold 2 and the core mold 1 is partially tapered.

[0043] refer to Figure 8 , Figure 10 and Figure 12 The outer flow channel ring 3, inner flow channel ring 4, core flow channel ring 5 and frame 6 all adopt a rotating body structure. The outer flow channel ring 3, inner flow channel ring 4 and core flow channel ring 5 are designed as tubular rings, which are sequentially nested and fixed on the frame 6. In order to stabilize the distribution of materials in different directions, the inner flow channel ring 4, core flow channel ring 5 and frame 6 are machined with threaded grooves or raised threaded structures to form annular marked injection channels 13, grooved injection channels 14 and co-extrusion injection channels 12, which guide the material to flow in annular shape.

[0044] like Figure 10 and Figure 11 As shown, in one embodiment, a connecting cavity 23 is provided between the marking injection channel 13 and the molding channel 11. The connecting cavity 23 is annular, and an annular piston 24 is provided axially in the connecting cavity 23. When the annular piston 24 moves axially, it increases the volume of the connecting cavity 23, which can generate negative pressure. The valve structure 15 and the negative pressure retraction structure 16 can be an integral structure, namely the annular piston 24 structure.

[0045] like Figure 10 and Figure 11 As shown, in one embodiment, the connecting cavity 23 is located on the outer end face of the inner flow channel ring 4. The annular piston 24 and the inner flow channel ring 4 are arranged axially. When the annular piston 24 moves towards the inner flow channel ring 4 and its first end face contacts the outer end face of the inner flow channel, the connecting cavity 23 is closed, i.e., the marked injection channel 13 is closed. When the annular piston 24 moves away from the inner flow channel ring 4 and its first end face does not contact the outer end face of the inner flow channel, the connecting cavity 23 is opened, i.e., the marked injection channel 13 is opened. The annular piston 24 can achieve linear movement by means of a hydraulic cylinder, a gear and rack, a worm gear structure, or a cam.

[0046] like Figure 12 and Figure 13As shown, in one embodiment, the annular piston 24 includes an annular portion 25 and a transmission portion 26. The transmission portion 26 has multiple threads extending axially from the annular portion 25. A portion of the transmission portion 26 has external threads 27, which mate with a threaded sleeve 28. The threaded sleeve 28 is driven to rotate by a second driving member. The second driving member is a bevel gear 29, which rotates directly or indirectly via a geared motor or a hydraulic motor. The forward and reverse rotation of the bevel gear 29 corresponds to the forward and reverse axial movement of the annular piston 24. Figure 11 As shown, to limit the position of the bevel gear 29, a first bearing and a second bearing are provided to limit the axial position of the bevel gear 29, so that the bevel gear 29 provides an axial force to the annular piston 24. A protective shell 30 is provided outside the bevel gear 29. Figure 13 and Figure 14 As shown, the rear outer mold 22 is provided with an annular cavity 32 and a bore cavity 31. The annular cavity 32 can accommodate the annular part 25 of the annular piston 24, and the bore cavity 31 can accommodate the transmission part 26.

[0047] like Figure 8 and Figure 11 As shown, in one embodiment, the core mold 1 is provided with a first driving part 33, which is connected to a first driving member 34 to achieve unidirectional rotation or small-angle back-and-forth rotation. The core mold 1 is provided with small protrusions 41 for processing grooves on the inner wall of the co-extruded tube, which can process straight, spiral, and wavy grooves. refer to Figure 10 and Figure 11 A method for manufacturing a co-extruded tube includes at least two alternating injection states during the manufacturing of the same co-extruded tube. The co-extruded tube manufacturing apparatus is equipped with at least a marking injection channel 13 and a co-extrusion injection channel 12. In the first injection state, the marking injection channel 13 injects a first material 35 at a first speed under a first pressure, and the co-extrusion injection channel 12 injects a second material 37 at a second speed under a second pressure. When the second material 37 exits the co-extrusion die head, the first material 35 is located on the outer surface of the second material 37. In the second injection state, the pressure of the marking injection channel 13 decreases or the marking injection channel 13 is closed, causing the injection speed of the first material 35 to decrease to zero or to draw in a certain amount of the second material 37 in the reverse direction. The injection pressure of the co-extrusion injection channel 12 remains unchanged or increases, and the injection speed of the second material 37 in the co-extrusion injection channel 12 increases. When the second material 37 exits the co-extrusion die head, the second material 37 is directly exposed on the outer surface. The first pressure is provided by the first injection machine, and the second pressure is provided by the second injection machine. When manufacturing a three-layer tube, a third injection machine is also provided, which provides a third material 36.

[0048] like Figure 16As shown, in one possible embodiment, a negative pressure retraction structure 16, i.e., an annular piston 24, is provided in the marking injection channel 13. In the second injection state, the negative pressure retraction structure 16 provides negative pressure, allowing a portion of the second material 37 to enter the marking injection channel 13, such as... Figure 15 As shown, in the first injection state, the negative pressure back-pulse structure 16 provides positive pressure to push the first material 35 and the second material 37 of the marked injection channel 13 to move along the injection direction.

[0049] like Figure 11 As shown, in one possible embodiment, a valve structure 15 is provided in the marked injection channel 13. In the second injection state, the valve structure 15 closes the channel, and the injection speed of the first material 35 drops to zero. Figure 10 As shown, in the first injection state, the valve structure 15 opens the channel, and the first material 35 resumes the injection speed.

[0050] Example 7: refer to Figure 17 , Figure 18 , Figure 19 and Figure 20 The difference from Embodiment 1 is that the molding channel 11 is provided with a positive pressure propulsion structure 17 and a pressure stabilizing chamber 18. The pressure stabilizing chamber 18 is located on the side of the outer mold 21 near the molding channel 11, and the positive pressure propulsion structure 17 is located on the side of the inner core mold 20 near the molding channel 11. The positive pressure propulsion structure 17 can be provided with a separate pressurizing device, or pressurization can be achieved using an injection molding machine. Alternatively, it can be formed using an outer core mold 19 and an inner core mold 20, with the outer core mold 19 fitted onto the inner core mold 20. The inner core mold 20 is provided with a tapered section 38. When the tapered section 38 moves along the first direction, it can increase the volume of the molding channel 11 to achieve pressure reduction. When the tapered section 38 moves in the opposite direction to the first direction, it can decrease the volume of the molding channel 11 to achieve pressure increase.

[0051] like Figure 20 and Figure 21 As shown, the pressure stabilizing chamber 18 is equipped with a tubular piston 39 and an elastic reset member 40. After being compressed to a certain length, the elastic reset member 40 is installed in the pressure stabilizing chamber 18 to push the tubular piston 39 to remain in a position close to the marking injection channel 13. When the pressure of the molding channel 11 on the tubular piston 39 exceeds a certain range, it can push the tubular piston 39 to move.

[0052] A method for manufacturing co-extruded tubes includes at least two manufacturing states during the manufacturing of the same co-extruded tube, alternating between a first injection state and a second injection state. The co-extruded tube manufacturing apparatus used is equipped with at least a marking injection channel 13, a co-extrusion injection channel 12, and a forming channel 11. Figure 20As shown, in the first injection state, the marked injection channel 13 injects the first material 35 at a first speed under the first pressure, and the co-extrusion injection channel 12 injects the second material 37 at a second speed under the second pressure. When the second material 37 detaches from the co-extrusion die head, the first material 35 is located on the outer surface of the second material 37; as shown... Figure 21 and Figure 22 As shown, in the second injection state, the pressure in the molding channel 11 increases. A pressure stabilizing chamber 18 is provided on the outside of the molding channel 11, allowing a portion of the first material 35 in the molding channel 11 to enter the pressure stabilizing chamber 18. That is, the first material 35 does not enter the molding channel 11 within a certain area, while the second material 37 advances along the outer wall of the molding channel 11. When the second material 37 detaches from the co-extrusion die head, the second material 37 is directly exposed on the outer surface. The pressure in the molding channel 11 can be controlled by the inner mandrel 20 moving towards the molding channel 11.

[0053] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this application can be achieved, and this is not limited herein.

[0054] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0055] It should be understood that if the directional terms such as "upper," "lower," "front," "rear," "left," and "right" are used to describe the embodiments of this application from the angle shown in a certain drawing, they should not be construed as limiting the embodiments of this application. In addition, in the context, it should also be understood that when it is mentioned that a component is connected to another component "upper" or "lower," it can be directly connected to the other component "upper" or "lower," or it can be indirectly connected to the other component "upper" or "lower" through an intermediate component.

[0056] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A co-extruded tube, characterized in that: It includes a marking layer (141) and a co-extruded layer (142), the marking layer (141) covering the co-extruded layer (142), the marking layer (141) being extruded using a first material (35) and a second material (37), the first material (35) and the second material (37) having different colors, the first material (35) and the second material (37) being spaced apart along the co-extruded tube axially at least on the end surface (144) of the co-extruded tube, and having a boundary line or transition zone at the junction of the first material (35) and the second material (37).

2. The co-extruded tube according to claim 1, characterized in that: The marking layer (141) is provided with a substrate ring (145), and the substrate ring (145) and the co-extruded layer (142) are made of the same second material (37).

3. The co-extruded tube according to claim 2, characterized in that: The marking layer (141) is provided with a marking ring (146), which is formed by extrusion molding of the first material (35).

4. The co-extruded tube according to claim 3, characterized in that: A transition ring (147) is provided between the substrate ring (145) and the marking ring (146).

5. The co-extruded tube according to claim 3 or 4, characterized in that: The cross-section of the marking ring (146) is rectangular, triangular, semi-circular, trapezoidal or semi-circular groove.

6. The co-extruded tube according to claim 5, characterized in that: The marking layer (141) includes a first annular region (148) and a second annular region (149), wherein the number of marking rings (146) in the first annular region (148) is different from the number of marking rings (146) in the second annular region (149).

7. The co-extruded tube according to claim 6, characterized in that: The co-extruded tube is provided with a cutting area (154), and the cutting area (154) is provided with a marking reference cutting end (155) and a length reference cutting end (156).

8. A three-layer co-extruded tube, employing the co-extruded tube structure described in any one of claims 1-7, characterized in that: The three-layer co-extruded tube is further provided with a groove layer (143), which is located inside the co-extruded layer (142).

9. The three-layer co-extruded tube according to claim 8, characterized in that: The groove layer (143) is provided with straight grooves (150), wavy grooves (151) or spiral grooves (152), and the straight grooves (150), wavy grooves (151) or spiral grooves (152) are evenly distributed on the inner wall of the three-layer co-extruded tube.

10. A co-extrusion die head for a three-layer co-extrusion tube, characterized in that: The assembly includes a core mold (1), an outer mold (2), an outer runner ring (3), an inner runner ring (4), a core runner ring (5), a first pair of interfaces (7), a second pair of interfaces (8), and a frame (6). A molding channel (11) is formed between the core mold (1) and the outer mold (2). A marking injection channel (13) is formed between the inner runner ring (4) and the outer runner ring (3). A co-extrusion injection channel (12) is formed between the core runner ring (5) and the inner runner ring (4). The marking injection channel (13) is connected to the first pair of interfaces (7). The co-extrusion injection channel (12) is connected to the second pair of interfaces (8). A wire groove injection channel (14) is formed between the core runner ring (5) and the frame (6). The groove injection channel (14) is connected to the third pair of interfaces (9). The molding channel (11) is connected to the marking injection channel (13), the groove injection channel (14) and the co-extrusion injection channel (12). The marking injection channel (13) is provided with a valve structure (15) or a negative pressure backflow structure (16). The valve structure (15) controls the flow of the first material (35) in the marking injection channel (13) or the molding channel (11). Alternatively, the molding channel (11) is provided with a positive pressure propulsion structure (17) and a pressure stabilizing chamber (18). The pressure stabilizing chamber (18) is located on the side close to the marking injection channel (13), and the positive pressure propulsion structure (17) is located on the side away from the marking injection channel (13).

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