Forming device and forming method for PE large-diameter thick-wall pipeline

Abstract

The invention relates to a forming device for a PE large-diameter thick-wall pipeline, which comprises a mouth mold, a core mold and a control assembly, the mouth mold and the core mold are arranged at an outlet of an extruder, the core mold is coaxially sleeved with the mouth mold, an annular flow divider is arranged on the core mold, the annular flow divider and the core mold are coaxially fixed, and the control assembly is arranged on the control assembly. A cooling loop is arranged in the annular flow divider, the cooling loop is communicated with an external cooling system, and the control assembly controls the cooling system to introduce cooling liquid into the cooling loop; the invention further relates to a forming method for the PE large-diameter thick-wall pipeline, the thick-wall pipeline is pre-divided into multiple layers of pipe walls, and step-by-step extrusion composite forming is carried out. The method has the advantages that the sag effect is reduced, production is facilitated, and the production cost is controlled.

Description

Technical Field

[0001] This application relates to the technical field of pipe forming, and in particular to a forming device and a forming method for large-diameter thick-wall PE pipes. Background Art

[0002] Large-diameter thick-wall PE pipes generally refer to solid-wall pipes with an outer diameter of more than 500 mm and a pipe wall thickness of more than 40 mm. The production of PE pipes is generally extruded and formed by an extruder. During the extrusion process of large-diameter pipes, due to the thick pipe wall, the cooling and solidification speed is slow, and the melt will sag under the action of gravity, resulting in a small wall thickness on the upper part and a large wall thickness on the lower part, that is, the "melt sag effect", so that the obtained pipe wall cannot reach the required tolerance and cannot achieve compliant butt fusion welding.

[0003] In related technologies, in order to avoid the melt sag effect, one way is to use high-price low-melt hammer raw materials, or by adjusting the die gap of the extruder, that is: increasing the upper gap and decreasing the lower gap. Although it can be compensated to a certain extent, the effect that this compensation can achieve is also very limited. Or by a special device to transfer the pre-treated cold compressed air to the inner surface of the polyethylene pipe, and take away the heat on the inner surface of the pipe through air convection, so as to realize the way of cooling the pipe simultaneously on the outer wall and the inner wall of the pipe to accelerate the cooling of the pipe, and can reduce the influence degree of "melt sag". In view of the above related technologies, although the wall thickness deviation caused by large-diameter melt hammers can be improved, the production cost and control difficulty are relatively high. Summary of the Invention

[0004] In order to ensure reducing the melt sag effect while facilitating production and controlling production costs, this application provides a forming device and a forming method for large-diameter thick-wall PE pipes.

[0005] The forming device and the forming method for large-diameter thick-wall PE pipes provided by this application adopt the following technical solutions: A forming device for large-diameter thick-wall PE pipes includes a die and a mandrel arranged at the outlet of an extruder and a control component. The die is coaxially sleeved outside the mandrel. An annular diverter is arranged on the mandrel. The annular diverter is coaxially fixed with the mandrel. A cooling circuit is arranged inside the annular diverter. An external cooling system is communicated with the cooling circuit. The control component controls the cooling system to introduce a coolant into the cooling circuit.

[0006] By employing this technical solution, the molten PE flows between the core and die, dissipating heat through an annular diverter. This heat is then rapidly removed through an internal cooling circuit, mitigating sag and improving wall thickness consistency and molding stability. The control component precisely controls the temperature of the annular diverter, thereby precisely controlling the temperature of the molten material flowing between the die and core, effectively reducing the temperature of the preform emerging from the mold.

[0007] Preferably, the annular diverter is formed with a first conical surface at both ends along the die feeding direction.

[0008] By adopting the above technical solution, the first conical surface can achieve smooth flow of the melt from the core mold to the die, optimize the melt flow trajectory, reduce shear dead angles, prevent eddy currents and accumulation, and improve flow channel uniformity.

[0009] Preferably, a support frame is provided between the annular diverter and the core mold, and second conical surfaces are formed on both ends of the support frame along the feeding direction of the die. There are multiple support frames arranged in a circular array around the axis of the core mold.

[0010] By adopting the above technical solutions, the support frame provides structural stability, allowing the annular diverter to be fixed to the core mold and maintain coaxiality to prevent deviation. The tapered end face further guides the melt flow, improving molding consistency and overall extrusion stability.

[0011] Preferably, any two of the support frames are provided with conduits for connecting the annular diverter and the external cooling system, and the two conduits are respectively connected to the internal cooling circuit of the annular diverter.

[0012] By adopting the above technical solution, the conduit is embedded inside the support frame without taking up additional space, effectively introducing the coolant into the cooling circuit inside the diverter, thereby realizing closed-loop operation of the temperature control system.

[0013] Preferably, the core mold is a hollow structure, and the two conduits pass through the cavity in the core mold toward a side away from the extrusion side of the extruder.

[0014] By adopting the above technical solution, the catheter passes through the core mold cavity to the side of the extrusion direction, effectively avoiding direct contact with the molten material, reducing pollution and structural interference. The core mold has a hollow structure, and the catheter can be guided from its inside to the diverter, forming a hidden layout, thereby improving the compactness and durability of the device.

[0015] Preferably, the external cooling system connected to the two conduits is an oil temperature cooling system.

[0016] By adopting the above technical solution, an oil temperature cooling system is used, which has high temperature control accuracy and stable heat exchange efficiency. It can keep the cooling system running reliably in high-temperature and high-pressure environments. By maintaining the coolant within a specific temperature range through a constant temperature control oil temperature system, the influence of the temperature fluctuation of the diverter on the extrusion molding quality can be avoided.

[0017] Preferably, the cooling circuit inside the annular diverter is spirally distributed inside the annular diverter.

[0018] By adopting the above technical solution, the coolant flows in a spiral manner inside the annular diverter, forming a sufficient heat exchange path to ensure that heat is evenly removed and prevent local overheating. The spiral distribution is beneficial to increasing the cooling area and extending the cooling path, thereby enhancing the heat exchange efficiency.

[0019] A forming method for large-diameter thick-walled PE pipes, which pre-divides the thick-walled pipe into multiple layers of pipe walls and performs step-by-step extrusion and composite forming: S1: Put the raw materials into the extruder. After heating to a molten state, install the forming device on the extruder and extrude the first inner pipe through the core die and the die of the forming device. S2: Send the first inner pipe into the spray cooling water tank for cooling and shaping. S3: Blow dry the water droplets on the surface of the first inner pipe through a blower. S4: After sending the first inner pipe into the heating box, pass it through the covering die head and extrude the second pipe wall, which is covered on the surface of the first inner pipe for bonding. S5: Cool the second pipe wall through a blower, then send it into the heating box for heating, and extrude the third pipe wall through the covering die head. S6: Repeat the steps of S4 - S5 to cover multiple layers of PE pipe walls on the first inner pipe. S7: Finally, send the multi-layer formed thick-walled pipe into the spray cooling water tank for cooling.

[0020] By adopting the above technical solution, the multi-layer pipe walls are extruded, cooled, and bonded step by step, which can achieve precise control of the wall thickness of each layer and the cooling rate. As a whole, a laminated structure is formed, which has excellent mechanical strength and stability. By using the multi-step extrusion method to form the thick-walled pipe in layers, the sag effect can be significantly reduced, the wall thickness consistency can be improved, and the material cost and control difficulty can be reduced.

[0021] In summary, the present application includes at least one of the following beneficial technical effects: 1. By setting an annular diverter and its internal cooling circuit in the forming device, and cooperating with a precise temperature control system, the temperature of the molten PE blank can be effectively controlled, the "sag effect" under the action of gravity can be significantly weakened, and the consistency of the pipe wall thickness and the stability of the extrusion process can be improved. 2. An integrated solution using a hollow core mold, a spiral cooling circuit, embedded ducts, and an oil temperature cooling system achieves the advantages of a compact structure, a large heat exchange area, and a long cooling path. While ensuring the strength of the device, it significantly improves the cooling efficiency and optimizes the overall extrusion process control; 3. The forming method adopts a multi-layer coating and step-by-step extrusion strategy, which not only reduces the dependence on raw materials (such as high melt index PE), allows the use of lower-cost PE100 raw materials, but also improves the forming stability and product consistency, facilitating the large-scale production of high-quality and low-cost large-diameter thick-walled pipes. Description of the Drawings

[0022] Figure 1 is a cross-sectional view mainly showing the internal structure of the forming device for large-diameter thick-walled PE pipes in Embodiment 1 of the present application; Figure 2 is an axonometric view mainly showing the structure between the annular diverter and the core mold in Embodiment 1 of the present application; Figure 3 is a device distribution diagram mainly showing the forming method for large-diameter thick-walled PE pipes in Embodiment 2 of the present application.

[0023] Reference numerals: 1, forming device; 2, die; 3, core mold; 4, annular diverter; 41, first conical surface; 42, cooling circuit; 5, support frame; 51, second conical surface; 6, duct; 10, extruder; 20, spray cooling water tank; 30, fan; 40, heating box; 50, coating die head; 60, tractor; 70, cutting machine. Detailed Description of the Embodiments

[0024] The following further elaborates on the present application Figures 1 - 3 with reference to the accompanying drawings.

[0025] Embodiment 1 of the present application discloses a forming device and a forming method for large-diameter thick-walled PE pipes.

[0026] Embodiment 1 Refer to Figures 1 - 2 , the forming device 1 for large-diameter thick-walled PE pipes includes a die 2 and a core mold 3 detachably fixed at the outlet of the extruder 10. The die 2 is coaxially sleeved outside the core mold 3, and the core mold 3 is hollow. An annular diverter 4 is sleeved on the core mold 3, the annular diverter 4 is coaxially sleeved on the core mold 3, the annular diverter 4 is located in the middle of the gap between the core mold 3 and the die 2, and the annular diverter 4 is detachably fixed to the core mold 3 through a support frame 5. A plurality of support frames 5 are circumferentially arranged around the axis of the core mold 3. In this embodiment, four support frames 5 are provided. First conical surfaces 41 are formed at both ends of the annular diverter 4 along the feeding direction of the die 2. Second conical surfaces 51 are formed at both ends of any one support frame 5 along the feeding direction of the die 2.

[0027] A cooling circuit 42 is provided within the annular diverter 4, and the cooling circuit 42 is arranged in a spiral shape. Two conduits 6 are connected to the cooling circuit 42. The two conduits 6 extend through the corresponding support frame 5 and the side wall of the core mold 3, and then pass through the hollow inner cavity of the core mold 3 to the side facing away from the extruder 10. The two conduits 6 pass through the extruder 10 and connect to an external cooling system. In this embodiment of the present application, the cooling system adopts an oil cooling system. The two conduits 6 are used to flow out and in, respectively, the coolant.

[0028] The forming device 1 for large-diameter, thick-walled PE pipes further includes a control assembly, which can be configured as a PLC integrated module including a processor and components such as a power supply, a control screen, and buttons electrically connected to the processor, and connected to an external cooling system via an electrical circuit or wireless signal. The control assembly allows a worker to control the cooling system, thereby precisely controlling the temperature of the annular diverter 4, thereby precisely controlling the temperature of the molten raw material flowing through the annular diverter 4 between the die 2 and the core die 3.

[0029] A forming device 1 for large-diameter, thick-walled PE pipes operates as follows: A worker, through a control assembly, controls the flow of coolant into a conduit 6, thereby controlling the flow of coolant into and out of a cooling circuit 42 within an annular diverter 4, thereby precisely controlling the temperature of the annular diverter 4. An extruder 10 extrudes molten material from left to right in the diagram. The molten material flows through the annular diverter 4, exchanging heat with it. This method effectively controls the temperature of the molten PE preform, significantly reducing the "sag effect" caused by gravity, and improving the consistency of the pipe wall thickness and the stability of the extrusion process.

[0030] Example 2 See also Figure 3 The forming method for PE large-diameter thick-walled pipes is to pre-divide the thick-walled pipes into multiple layers of pipe walls and extrude them step by step through an extruder 10. The forming method is as follows: S1: The raw materials are placed in an extruder 10 and heated to a molten state. The forming device 1 for PE large-diameter thick-walled pipes in Example 1 is installed on the initial extruder 10, and the first layer of the inner pipe is extruded through the core die 3 and the die 2 of the forming device 1; S2: Send the first layer of inner tubes into the spray cooling water tank 20 for cooling and shaping; S3: The water droplets on the surface of the first layer of inner tubes are blown dry by the fan 30; S4: After the first layer of inner tube is fed into the heating box 40, a coating die 50 is installed on the second extruder 10. After the first layer of inner tube passes through the coating die 50, the extruder 10 extrude the second layer of tube wall, which is coated on the surface of the first layer of inner tube and bonded; S5: Cool the second layer of the pipe wall through the fan 30, then send it into the heating box 40 for heating, and extrude the third layer of the pipe wall through the coating die head 50 installed on the third extruder 10; S6: Repeat the steps of S4 - S5 until the preset multi-layer PE layer pipe wall is coated on the first inner pipe; S7: Finally, send the multi-layer formed thick-walled pipe into the spray cooling water tank 20 for cooling; S8: The tractor 60 sends the cooled thick-walled pipe into the cutting machine 70 for cutting.

[0031] The multi-step extrusion method is used to form the thick-walled pipe in layers, which can significantly reduce the sag effect, improve the wall thickness consistency, reduce the material cost and the control difficulty.

[0032] The above are all the preferred embodiments of this application. The protection scope of this application is not limited by this. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A forming device for large-diameter and thick-wall PE pipes, characterized in that: The invention comprises a mouth die (2) and a core die (3) and a control component arranged at the outlet of an extruder (10), wherein the mouth die (2) is coaxially sleeved on the outside of the core die (3), an annular diverter (4) is arranged on the core die (3), the annular diverter (4) is coaxially fixed with the core die (3), a cooling circuit (42) is arranged inside the annular diverter (4), the cooling circuit (42) is connected to an external cooling system, and the control component controls the cooling system to pass cooling liquid into the cooling circuit (42).

2. The forming device for a large-diameter and thick-wall PE pipe according to claim 1, characterized in that: The annular flow divider is formed with first conical surfaces (41) at both ends along the feeding direction of the die (2).

3. The forming device for large-diameter thick-wall PE pipes according to claim 1, characterized in that: A support frame (5) is provided between the annular diverter (4) and the core mold (3), and second conical surfaces (51) are respectively formed on both ends of the support frame (5) along the feeding direction of the die (2). There are multiple support frames (5) arranged in a circular array around the axis direction of the core mold (3).

4. The forming device for a large-diameter thick-wall PE pipe according to claim 3, characterized in that: Any two of the support frames (5) are provided with conduits (6) for connecting the annular diverter (4) and the external cooling system, and the two conduits (6) are respectively connected to the internal cooling circuit (42) of the annular diverter (4).

5. The forming device for a large-diameter and thick-wall PE pipe according to claim 4, wherein: The core mold (3) is a hollow structure, and the two conduits (6) pass through the cavity in the core mold (3) toward a side facing away from the extrusion side of the extruder (10).

6. The forming device for a large-diameter and thick-wall PE pipe according to claim 4, characterized in that: The external cooling system connected to the two conduits (6) is an oil temperature cooling system.

7. The forming device for a large-diameter and thick-wall PE pipe according to claim 1, characterized in that: The cooling circuit (42) inside the annular flow divider (4) is distributed in a spiral manner inside the annular flow divider (4).

8. A forming method for large-diameter thick-wall PE pipes, using the forming device according to any one of claims 1-7, characterized in that: Pre-dividing thick-walled pipes into multiple layers and extruding them into composite shapes in steps: S1: placing the raw materials into an extruder (10), heating them to a molten state, installing a molding device (1) on the extruder (10), and extruding a first layer of inner tube through the core die (3) and the die (2) of the molding device (1); S2: sending the first layer of inner tubes into the spray cooling water tank (20) for cooling and shaping; S3: Drying the water droplets on the surface of the first layer of inner tube by using the fan (30); S4: After the first layer of inner tube is fed into the heating box (40), the second layer of tube wall is extruded through the coating die (50) and coated on the surface of the first layer of inner tube for bonding; S5: cooling the second layer of tube wall by a fan (30), then sending it into a heating box (40) for heating, and extruding the third layer of tube wall through a coating die (50); S6: Repeat steps S4-S5 to coat the first inner tube with multiple layers of PE pipe wall; S7: Finally, the multi-layered thick-walled pipe is sent to a spray cooling water tank (20) for cooling.

Images