Pipe extrusion molding machine head

Abstract

The invention relates to the technical field of pipe extrusion molding, in particular to a pipe extrusion molding machine head which solves the problems that a pipe extruded by a traditional molding machine head is low in cooling efficiency and uneven in cooling, the pipe extrusion molding machine head comprises an opening die installed outside and a core rod installed inside, and a die opening gap is formed between the core rod and the opening die and used for extruding the pipe. The end part of the core rod axially extends in the direction of the extruded pipe and extends out of the mouth mold for a certain distance, a flow cavity is formed in the core rod, and an input flow channel and a backflow flow channel which are communicated with the flow cavity are formed in the core rod; the part, located in the forming machine head, of the core rod is connected with an input pipe communicating with the input runner and a backflow pipe communicating with the backflow runner, and the input pipe and the backflow pipe both penetrate through the outer wall of the forming machine head. A medium used for cooling is input into the flow cavity through the input pipe, the medium flows in the flow cavity to cool the core rod, the cooled core rod is used for cooling the inner wall of an extruded pipe, and finally the medium is discharged through the backflow pipe.

Description

Technical Field

[0001] The present invention relates to the technical field of pipe extrusion molding, and particularly to a pipe extrusion molding head. Background Art

[0002] Pipe extrusion molding is one of the important processes in the processing field. Its principle is to heat and melt high molecular materials (such as polyethylene, polypropylene, polyvinyl chloride, etc.) through an extruder, form them into a tubular blank through a die head mold, and then make pipe products with specific specifications and properties through subsequent processes such as cooling, traction, and cutting. This process has the characteristics of high production efficiency, strong continuity, and good dimensional stability of products, and is widely used in fields such as building water supply and drainage, municipal engineering, agricultural irrigation, and industrial pipelines. With the continuous improvement of the requirements for pipe performance in various industries, such as high strength, corrosion resistance, high temperature resistance, and impact resistance, the pipe extrusion molding process is also continuously optimized and innovated. Especially in key links such as die head design, material plasticization effect, and cooling system efficiency, it has become the key research and development direction of the industry technology.

[0003] The cooling link after pipe extrusion molding is crucial. At present, in the traditional pipe extrusion molding process, it is common to directly transport the extruded pipe to a cooler and cool it from the outer wall of the pipe with cold water. This cooling method usually sprays water on the outer wall of the pipe through a nozzle to achieve the cooling of the pipe.

[0004] However, the existing method of cooling the pipe only cools from the outer wall of the pipe. When the pipe wall is thick, during the cooling process of the pipe from the outside to the inside, the inside and the outside cannot be cooled simultaneously. This makes the shrinkage degree of the inside and the outside of the pipe inconsistent during the cooling process, and thus easily causes the pipe to deform. Even if the pipe is formed subsequently, due to the asynchronous cooling, the strength of different positions on the outer wall of the pipe will also be different, and it is easy to break when the stress is uneven.

[0005] In addition, relying solely on the cooling method from the outside to the inside seriously reduces the cooling efficiency. In order to achieve the cooling effect, after the pipe is completely cooled from the outside to the inside, the cooler often needs to be designed with a very long distance, which undoubtedly increases the equipment input cost, including equipment purchase cost, installation space cost, etc. At the same time, the long cooling distance will also affect the layout of the production site, reduce the utilization rate of the production site, and make the production process less compact and efficient. Summary of the Invention

[0006] (1) Technical Problems to be Solved

[0007] Aiming at the deficiencies of the prior art, the present invention provides a pipe extrusion molding head, which solves the problems of low cooling efficiency and uneven cooling of the pipe extruded by the traditional molding head.

[0008] (2) Technical Solution

[0009] To achieve the above object, the present invention provides the following technical solution: A pipe extrusion forming head includes a die installed externally and a mandrel installed internally. A die gap is formed between the mandrel and the die for extruding pipes. The end of the mandrel extends axially along the direction of the extruded pipe and extends a certain distance outside the die. A flow cavity is provided inside the mandrel, and an input flow channel and a return flow channel communicating with the flow cavity are provided inside the mandrel; A part of the mandrel located inside the forming head is connected with an input pipe communicating with the input flow channel and a return pipe communicating with the return flow channel. Both the input pipe and the return pipe penetrate through the outer wall of the forming head; A medium for cooling is input into the flow cavity through the input pipe. The medium flows in the flow cavity to cool the mandrel. The cooled mandrel is used to cool the inner wall of the extruded pipe, and finally the medium is discharged through the return pipe.

[0010] Further, the flow cavity inside the mandrel is close to the outer wall of the mandrel.

[0011] Further, the input flow channel communicates with one end of the flow cavity close to the forming head, and the return flow channel communicates with one end of the flow cavity far from the forming head.

[0012] Further, a plurality of baffles are provided in the flow cavity, and the baffles divide the flow cavity into a plurality of independent cavities.

[0013] Further, the cavities communicate with the input flow channel and the return flow channel respectively through branch flow channels.

[0014] Further, the mandrel has an installation roller inside, the flow cavity is arranged inside the installation roller inside the mandrel, and the input flow channel and the return flow channel are also arranged inside the installation roller inside the mandrel.

[0015] Further, an installation cavity for installing the installation roller is opened inside the mandrel. The length of the installation cavity is longer than that of the installation roller, and the installation roller can move axially inside the installation cavity along the mandrel for adjusting the position of the installation roller.

[0016] Further, a lead screw is installed at the end of the mandrel extending outward. One end of the lead screw is connected to the installation roller, and rotating the lead screw can drive the installation roller to move axially inside the installation cavity along the mandrel.

[0017] Further, both the input flow channel and the return flow channel have bendable connecting pipes, and the connecting pipes are installed inside the installation cavity.

[0018] Further, an observation port is opened on the outer wall of the mandrel, and a transparent component is installed in the observation port. The outer wall of the transparent component is consistent with the outer wall of the mandrel.

[0019] (3) Beneficial Effects

[0020] Compared with the prior art, the present invention provides a pipe extrusion forming head, which has the following beneficial effects:

[0021] For the pipe extrusion forming head, the mandrel extends axially along the direction of the extruded pipe. And through the setting of the flow cavity in the mandrel, a low-temperature medium (such as water, brine, oil, etc.) for cooling is input into the flow cavity through an input pipe. The low-temperature cooling medium cools the mandrel. In this way, after the pipe extruded along the mandrel moves to the cooling position of the mandrel, the mandrel conducts heat to cool the inner wall of the pipe in direct contact with its outer wall, so as to realize the internal cooling of the extruded pipe.

[0022] Combined with the traditional way of cooling the outer wall of the pipe (such as spraying cold water on the outer wall of the pipe), synchronous cooling of the inner and outer walls of the pipe is realized, avoiding uneven internal and external shrinkage caused by the traditional cooling method of "outer cold and inner hot", greatly reducing the risk of pipe deformation, and ensuring uniform internal and external strength of the pipe, improving the forming quality of the pipe.

[0023] By adopting the method of synchronous internal and external cooling, the cooling time only by the outer wall is effectively shortened. Especially for thick-walled pipes, the total cooling time required can be significantly reduced, effectively improving the cooling efficiency. At the same time, there is no need to rely on the ultra-long distance design of the traditional cooler, reducing the equipment occupation space, reducing the length of the production line and the site cost, and improving the cooling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a three-dimensional structural schematic diagram of the present invention;

[0025] Figure 2 is a partial cross-sectional three-dimensional structural schematic diagram of the present invention;

[0026] Figure 3 is a cross-sectional structural schematic diagram of the first embodiment of the flow cavity of the present invention;

[0027] Figure 4 is a cross-sectional structural schematic diagram of the second embodiment of the flow cavity of the present invention;

[0028] Figure 5 is a cross-sectional structural schematic diagram of the flow cavity of the present invention, wherein an installation roller is arranged inside the mandrel;

[0029] Figure 6 is of the present invention Figure 3 is a partially enlarged structural schematic diagram of the position A shown in;

[0030] Figure 7 is of the present invention Figure 4 is a partially enlarged structural schematic diagram of the position B shown in;

[0031] Figure 8 For the present invention Figure 5 It is a schematic structural diagram of the partial enlargement at position C shown in the present invention;

[0032] Figure 9 For the present invention Figure 5 It is a schematic structural diagram of the partial enlargement at position D shown in the present invention;

[0033] Figure 10 It is a schematic perspective sectional structure diagram of a mandrel of the present invention. Among them, the flow cavity inside the mandrel is the first embodiment and is longitudinally cut along the vertical axis direction;

[0034] Figure 11 It is a schematic perspective sectional structure diagram of a mandrel of the present invention. Among them, the flow cavity inside the mandrel is the first embodiment and is longitudinally cut along the parallel axis direction;

[0035] Figure 12 It is a schematic perspective sectional structure diagram of a mandrel of the present invention. Among them, the flow cavity inside the mandrel is the second embodiment and is longitudinally cut along the parallel axis direction;

[0036] Figure 13 It is a schematic perspective sectional structure diagram of a mandrel of the present invention. Among them, an installation roller is provided inside the mandrel and is longitudinally cut along the parallel axis direction;

[0037] Figure 14 For the present invention Figure 10 It is a schematic structural diagram of the partial enlargement at position E shown in the present invention;

[0038] Figure 15 For the present invention Figure 11 It is a schematic structural diagram of the partial enlargement at position F shown in the present invention;

[0039] Figure 16 For the present invention Figure 12 It is a schematic structural diagram of the partial enlargement at position G shown in the present invention;

[0040] Figure 17 For the present invention Figure 13 It is a schematic structural diagram of the partial enlargement at position H shown in the present invention.

[0041] In the figure: 1. Die; 2. Mandrel; 3. Connecting body; 4. Flow cavity; 5. Input pipe; 6. Return pipe; 7. Input flow channel; 8. Return flow channel; 9. Die gap; 10. Baffle; 11. Cavity; 12. Branch flow channel; 13. Installation roller; 14. Installation cavity; 15. End cover; 16. Observation port; 17. Lead screw; 18. Screwing part; 19. Threaded post; 20. Connecting sleeve; 21. Connecting frame; 22. Joint; 23. Valve; 24. Temperature sensor; 25. Flange; 26. Bolt; 27. Step hole; 28. Threaded hole; 29. Connecting pipe; 30. Rib; 31. Chute. Detailed implementation manners

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] In the prior art, a pipe extrusion forming head mainly includes an external die 1, an internal mandrel 2, and a connecting body 3 connected to the die 1. The mandrel 2 and the die 1 are coaxially arranged, and an annular die gap 9 is formed therebetween, and this gap determines the wall thickness of the extruded pipe. The connecting body 3 connected to the die 1 is used to dock with the extruder, and the connection methods include integral molding, fixed connection, and detachable connection.

[0044] For fixed connection, it is usually fixed by welding or other means;

[0045] For detachable connection, a flange 25 is usually provided on the connecting body 3 and connected to the flange of the extruder outlet through a bolt group, which is convenient for disassembly, maintenance, or replacement of different specifications of the die 1.

[0046] The die 1 and the connecting body 3 adopt a bolt 26 connection structure, and the specific design is as follows:

[0047] As Figure 9 shown, a stepped hole 27 is machined on the die, the connecting body 3 is installed in the stepped hole 27 of the die 1, and at the same time, a screw hole 28 matching the bolt 26 is provided on the connecting body 3. After the bolt 26 passes through the stepped hole 27 for positioning, it is screwed into the screw hole 28 of the connecting body 3, and the reliable connection between the two is achieved through the tightening force of the bolt 26.

[0048] When operations such as repairing, overhauling the inside of the forming head or replacing the mandrel 2 are required, only need to loosen the bolt 26, and the die 1 can be disassembled from the connecting body 3, quickly opening the internal space of the forming head, which is convenient for the operator to perform maintenance operations. This structural design takes into account both connection stability and disassembly convenience, can effectively improve the equipment maintenance efficiency, and reduce the overhaul difficulty.

[0049] Working principle of the extruder: The extruder drives the screw to rotate through the motor, and feeds the solid plastic particles (such as polyethylene, polypropylene, polyvinyl chloride, etc.) conveyed in the hopper into the heating barrel. Under the combined action of the shear force of the screw and the heating of the barrel, the plastic particles are melted into a uniform fluid and pushed by the screw towards the die head direction. When the molten material enters the inside of the die 1, it is restricted by the die gap 9 formed by the mandrel 2 and the die 1, and is forced to pass through this annular channel, initially forming a tubular blank. The inner walls of both the tubular blank and the subsequent formed pipe closely adhere to the outer wall of the mandrel 2 and move along its axis. This close movement provides the basis for the internal cooling square described in detail below.

[0050] When the molten material is extruded through the die gap 9 to the outside of the forming die head, due to the size constraint of the forming die head and the external cooling effect on the pipe (such as spraying water or air cooling), it is gradually solidified into a pipe with a specific outer diameter and wall thickness. Subsequently, through the uniform traction of the tractor and the further cooling and shaping of the pipe by the cooling device, the production of the pipe is completed.

[0051] Please refer to Figures 1-3 and Figure 6 For a pipe extrusion forming die head of the present invention, the end of the mandrel 2 extends axially along the direction of the extruded pipe and extends a certain (sufficient) distance outside the die 1. A flow cavity 4 is provided inside the mandrel 2, and this flow cavity 4 serves as a circulation space for a cooling medium (such as water, brine, oil, etc.); at the same time, an input flow channel 7 and a return flow channel 8 connected to the flow cavity 4 are also provided inside the mandrel 2. The input flow channel 7 is used to introduce the cooling medium into the flow cavity 4, and the return flow channel 8 is used to export the cooling medium after heat exchange is completed. Through such a structural design, a channel basis is provided for realizing the internal cooling of the pipe. The mandrel 2 is made of a material with good thermal conductivity (such as metals like copper, aluminum, or stainless steel, etc.) to improve the heat exchange efficiency between the cooling medium and the inner wall of the pipe and ensure a significant cooling effect.

[0052] As Figure 6 shown, the flow cavity 4 inside the mandrel 2 is arranged closely against the outer wall of the mandrel 2, minimizing the heat transfer path between the cooling medium and the inner wall of the pipe and reducing the thermal resistance. This structure enables the cooling medium to quickly and efficiently transfer the temperature from the outer wall of the mandrel 2, significantly improving the cooling efficiency of the mandrel 2 for the inner wall of the pipe.

[0053] In the pipe extrusion forming device of the present invention, the mandrel 2 is used to cool the inside of the pipe, which can be combined with a traditional cooling device (such as cooling by spraying cold water on the outer wall of the pipe) to achieve synchronous cooling of the inside and outside of the pipe. The structure of the mandrel 2 in this patent injects a low-temperature cooling medium (such as water, brine, oil, etc.) through the internal flow cavity 4, enabling the mandrel 2 to conductively cool the inner wall of the pipe in direct contact with its outer wall, forming a two-way cooling method for cooling the inner wall and the outer wall of the pipe.

[0054] This synchronous cooling technology can effectively solve the problem of uneven internal and external shrinkage caused by "external cooling and internal heating" in traditional processes, avoid the deformation of the pipe due to asynchronous cooling, ensure the uniform strength of the inner and outer layers of the pipe, and significantly improve the product quality. Especially for thick-walled pipes, synchronous internal and external cooling can greatly shorten the cooling time, with the cooling efficiency increased by about 30%-50% compared with traditional single outer wall cooling. At the same time, there is no need to rely on the long conveying distance of traditional cooling machines, and the floor area of the equipment is reduced by about 40%-60%, reducing the site cost and the complexity of the production line, and combining high efficiency and economy.

[0055] As Figures 2-3 shown, a connecting frame 21 is fixedly arranged inside the forming head, and a connecting sleeve 20 is arranged in the middle of the connecting frame 21. The connection mode between the mandrel 2 and the connecting sleeve 20 is flexible and can adopt fixed connection or detachable connection. Among them, the detachable connection is realized through a threaded structure: one end of the mandrel 2 located inside the forming head is provided with a threaded post 19, and the connecting sleeve 20 is provided with a threaded hole matching it, and the two are detachably connected by screwing, which is convenient for the installation, disassembly and later maintenance of the mandrel 2.

[0056] On the part of the mandrel 2 located inside the forming head, connectors 22 for connecting the input pipe 5 and the return pipe 6 are respectively arranged. The input pipe 5 is connected to the input flow channel 7 inside the mandrel 2 through the connector 22, and the return pipe 6 is connected to the return flow channel 8 inside the mandrel 2 through the connector 22. The setting of the connector 22 facilitates the installation and disassembly of the input pipe 5 and the return pipe 6. The input pipe 5 and the return pipe 6 penetrate the outer wall of the forming head to form a circulation channel for the cooling medium. The input pipe 5 and the return pipe 6 are made of heat-insulating and high-temperature-resistant materials (such as ceramic fiber, high-temperature-resistant heat-insulating alloy or Teflon composite material, etc.), which can effectively block the heat exchange between the cooling medium and the high-temperature molten material, and ensure the stable non-interference between the medium for cooling and the high-temperature molten material.

[0057] During operation, the low-temperature cooled medium is injected into the flow cavity 4 through the input pipe 5 and the input flow channel 7, flows in the flow cavity 4, quickly takes away the heat of the mandrel 2, and reduces the surface temperature of the mandrel 2; the cooled mandrel 2 is in direct contact with the inner wall of the extruded pipe, conducts the heat to the medium, and realizes the cooling of the inner wall of the pipe; the medium that has completed the heat exchange is finally discharged through the return flow channel 8 and the return pipe 6 to form a complete cooling circulation system. It realizes the efficient circulation of the medium, enhances the cooling effect of the mandrel 2 on the inner wall of the pipe, and cooperates with the external cooling device to realize the synchronous cooling of the inside and outside of the pipe.

[0058] The installation positions of the input pipe 5 and the return pipe 6 are further described as follows: The input pipe 5 and the return pipe 6 are connected to the part of the mandrel 2 inside the forming head and extend out through the outer wall of the forming head. This layout design ensures that when the input pipe 5 and the return pipe 6 pass through the high-temperature molten material area inside the forming head, although they can avoid direct contact with the high-temperature molten material and cause obstruction to the flow path of the high-temperature molten material, it does not affect the normal extrusion molding of the pipe because the high-temperature molten material will be remelted together after passing through the input pipe 5 and the return pipe 6.

[0059] If the input pipe 5 and the return pipe 6 are installed on the part of the mandrel 2 extending outside the forming head or the outer wall, the input pipe 5 and the return pipe 6 will be exposed in the pipe forming area (outside the die 1), which may cause physical interference with the extruded pipe, hinder the smooth demolding of the pipe or lead to molding defects.

[0060] A temperature sensor 24 is installed at the position of the return pipe 6 outside the forming head, and its function is to monitor the temperature of the cooling medium in real time during the return process. And on the part of the input pipe 5 outside the forming head, a valve 23 is installed. This valve 23 is an electric valve 23 and has the function of accurately controlling the flow rate of the cooling medium. The temperature sensor 24 and the valve 23 are electrically connected through a controller to form a complete temperature control and adjustment system.

[0061] Specifically, one end of the input pipe 5 is connected to a pump body. The pump body, as a power source, can provide continuous and stable power for the input of the cooling medium to ensure that the cooling medium can circulate. The controller can analyze and process the temperature data transmitted by the temperature sensor 24 in real time. When the temperature sensor 24 detects that the temperature of the cooling medium in the return pipe 6 is too high, the controller will immediately send an instruction to the valve 23 to increase its opening degree, thereby accelerating the flow rate of the cooling medium and reducing the temperature by increasing the input of cold quantity; conversely, if the detected temperature is too low, the controller will control the valve 23 to reduce its opening degree and slow down the flow rate of the cooling medium to avoid the decrease of heat utilization rate due to excessive cold quantity.

[0062] Through this dynamic flow rate adjustment mechanism based on real-time temperature monitoring, the system can automatically adjust the delivery volume of the cooling medium according to the actual working conditions, ensure the efficient progress of the heat conversion process while maximizing the heat utilization rate, avoid energy waste, provide stable and reliable temperature control guarantee for the process inside the forming head, and thus improve the operation efficiency and process stability of the entire equipment.

[0063] As Figure 3 、 6 、10, 11, 14, and 15 show, the first embodiment of the layout of the flow cavity 4 inside the mandrel 2:

[0064] The flow cavity 4 is integrally arranged on the part of the mandrel 2 outside the die 1, and the length direction of the flow cavity 4 is distributed along the length direction of the mandrel 2. The flow cavity 4 has a certain length to sufficiently cool the pipe. The input flow channel 7 is connected to one end of the flow cavity 4, and the reflux flow channel 8 is connected to the other end of the flow cavity 4.

[0065] The input flow channel 7 can be connected to the end of the flow cavity 4 close to the forming head, and the reflux flow channel 8 can be connected to the end of the flow cavity 4 far from the forming head; or the input flow channel 7 can be connected to the end of the flow cavity 4 far from the forming head, and the reflux flow channel 8 can be connected to the end of the flow cavity 4 close to the forming head.

[0066] However, it is preferably that the input flow channel 7 is connected to the end of the flow cavity 4 close to the forming head, and the reflux flow channel 8 is connected to the end of the flow cavity 4 far from the forming head, so that the flow direction of the medium will be determined, and the flow direction of the medium in the flow cavity 4 is the same as the direction of the extruded pipe.

[0067] When the input flow channel 7 is connected to one end of the flow cavity 4 and the reflux flow channel 8 is connected to the other end of the flow cavity 4, the cooling medium flows in a single direction in the flow cavity 4. During this process, the medium will gradually increase in temperature due to continuously absorbing the heat conducted by the mandrel 2 (resulting from the high temperature of the extruded pipe), resulting in a gradual increase in the temperature of the cooling medium in the flow cavity 4 along the flow direction. For example, the medium just flowing into the flow cavity has a low temperature and high cooling efficiency, and the medium at the outlet end has a high temperature and a decreased cooling capacity. This phenomenon will cause the cooling effect on the inner wall of the pipe to show unevenness of "strong in the front section and weak in the rear section".

[0068] To solve the problem of the gradually increasing temperature of the cooling medium caused by the single-direction flow of the medium in the flow cavity 4 in the above first embodiment, as Figure 4 、 7 、12 and 16 show, the following provides a second embodiment of the layout of the flow cavity 4 in the mandrel 2:

[0069] A number of baffles 10 are arranged in the flow cavity 4, and the baffles 10 divide the flow cavity 4 into a number of independent cavities 11. Each cavity 11 is communicated with the input pipe 5 through a branch flow channel 12 and is communicated with the reflux pipe 6 through a branch flow channel 12. The position arrangement of the branch flow channels 12 for input and the branch flow channels 12 for output can enable the medium to flow fully in the cavity 11 before being discharged.

[0070] The long flow cavity 4 in the first embodiment is divided into a number of short cavities 11, avoiding the temperature increase caused by the cumulative heat absorption of the medium due to long-distance flow, ensuring that the medium in each cavity 11 participates in heat exchange in a low-temperature state, keeping the outer wall of the mandrel 2 at the same cooling temperature along the axis, and eliminating the temperature difference of "cold in the front section and hot in the rear section".

[0071] Moreover, the flow cavity 4 is divided into several independent cavities 11 by the baffle 10, which can effectively increase the contact area with the medium and improve the cooling effect of the mandrel 2.

[0072] Based on the above two embodiments, when inputting the cooling medium into the flow cavity 4, it is preferably to adopt the layout mode of bottom input and top reflux: the input flow channel 7 is communicated with the bottom of the flow cavity 4, and the reflux flow channel 8 is communicated with the top of the flow cavity 4. This design utilizes the gravity to make the cooled medium fill the entire flow cavity 4 from bottom to top, avoiding the formation of gas-liquid mixture or flow dead angle in the cavity, and ensuring full contact between the medium and the outer wall of the mandrel 2. At the same time, the flow path driven by gravity can make the medium evenly distributed in the flow cavity 4, effectively improving the uniformity of heat exchange.

[0073] As Figure 5 、 8 As shown in 13 and 17, an installation roller 13 is provided inside the mandrel 2, and the flow cavity 4, the input flow channel 7 and the reflux flow channel 8 are all integrally installed in the structure of the installation roller 13. Specifically, the flow cavity 4 surrounds or is embedded inside the installation roller 13 to form a circulation space for the cooling medium; partial positions of the input flow channel 7 and the reflux flow channel 8 respectively penetrate into the installation roller 13, one end is communicated with the flow cavity 4, and the other end extends to the end of the mandrel 2 and is connected with an external pipeline. This design realizes a compact layout of the internal structure of the mandrel 2 by integrating the flow cavity 4, the input flow channel 7 and the reflux flow channel 8 into the installation roller 13.

[0074] An installation cavity 14 extending along the length direction (i.e., the axial direction) of the mandrel 2 is opened inside the mandrel 2, and this cavity is used to install the installation roller 13 with the flow cavity 4, the input flow channel 7 and the reflux flow channel 8 integrally installed inside. The axial length of the installation cavity 14 is greater than that of the installation roller 13, so that the installation roller 13 can move along the axial direction of the mandrel 2 inside the installation cavity 14 to adjust the position of the installation roller 13 for adjusting the cooling position on the mandrel 2. In this way, the axial position of the installation roller 13 can be flexibly adjusted according to the actual cooling requirements.

[0075] According to the design that the position of the installation roller 13 is adjustable in the above text, its beneficial effects and application values are as follows:

[0076] In the field of pipe extrusion molding, the cooling device (such as a spray cooling machine) for externally cooling the pipe in the traditional production line is usually fixedly installed on the ground, and the relative distance between its position and the extrusion head is fixed. When the user (purchaser, user) wants to introduce the molding head with the cooling function of the mandrel 2 in the present invention, if the cooling position of the mandrel 2 (i.e., the area where the flow cavity 4 is located) does not match the spray area of the original external cooling device in the axial position (such as the cooling area of the mandrel 2 is too far forward or backward), it will cause the misalignment of the cooling intervals of the inner and outer walls of the pipe, and the synchronous temperature reduction cannot be achieved, affecting the molding quality.

[0077] Specifically, if the cooling zone of the mandrel 2 is ahead of the external cooling device, the inner wall of the pipe cools down in advance while the outer wall is still in a high-temperature state, which may cause the contraction of the inner wall to be blocked; if it is lagging, the outer wall has solidified while the inner wall has not been sufficiently cooled, easily leading to uneven internal and external stresses.

[0078] Therefore, if the original cooling device needs to be transformed, the following problems need to be faced:

[0079] High equipment transformation cost: Traditional cooling devices are often large-scale fixed equipment, involving complex structures such as ground fixing and pipeline connection. Re-disassembly and installation require a large amount of human, material and time costs;

[0080] Interruption of production continuity: The production line needs to be suspended during the equipment transformation, resulting in production capacity loss.

[0081] By arranging an axially movable mounting roller 13 inside the mandrel 2, integrating the flow cavity 4, the input flow channel 7, and the return flow channel 8 into the mounting roller 13, and using the length difference between the mounting cavity 14 of the mandrel 2 and the mounting roller 13 (the length of the mounting cavity 14 > the length of the mounting roller 13), the position of the mounting roller 13 can be adjusted. The user can slide the mounting roller 13 axially along the mandrel 2 according to the actual position of the original external cooling device, and precisely adjust the axial position of the flow cavity 4, so that the cooling zone of the mandrel 2 for the inner wall of the pipe is completely aligned with the cooling zone of the cooling device for the outer wall of the pipe. For example: when the cooling device is far from the head outlet, move the mounting roller 13 away from the forming head to extend the starting point of the inner wall cooling of the pipe; when the cooling device is close to the head, move the mounting roller 13 towards the forming head to start the internal and external cooling of the pipe in advance. To achieve synchronous cooling of the inner wall of the pipe by the mandrel 2 and the outer wall of the pipe by the cooling device.

[0082] To ensure the smooth axial movement of the mounting roller 13 in the mounting cavity 14 of the mandrel 2 and at the same time ensure good heat conduction effect, heat-conducting oil or heat-conducting silicone grease, etc. are applied at the gap between the outer wall of the mounting roller 13 and the inner wall of the mandrel 2, which not only reduces the mechanical movement resistance and improves the smoothness of the movement of the mounting roller 13, but also realizes efficient heat transfer between the mandrel 2 and the mounting roller 13 by virtue of the heat conduction characteristics of the heat-conducting oil or heat-conducting silicone grease.

[0083] A driving device for adjusting the position of the mounting roller 13 is arranged at the outermost end of the mandrel 2 located at the forming head to realize the axial movement of the mounting roller 13, mainly including the following two exemplary schemes.

[0084] Scheme 1: Drive through a lead screw 17

[0085] Such as Figure 5 and 13As shown in the figure, a lead screw 17 is installed at the end of the mandrel 2. One end of the lead screw 17 is rotatably connected to the mounting roller 13. The lead screw 17 and the mounting roller 13 can perform axial displacement synchronously. The other end passes through the end of the mandrel 2 and forms a threaded fit with the mandrel 2. When the lead screw 17 is rotated, based on the principle of screw drive, the lead screw 17 moves axially, synchronously driving the mounting roller 13 to slide in the mounting cavity 14. Precise adjustment can be achieved through the lead screw 17, and it has a self-locking function, which can ensure the stable position of the mounting roller 13 after adjustment.

[0086] It is also possible to rotatably install the lead screw 17 at the end of the mandrel 2. One end of the lead screw 17 is threadedly connected to the mounting roller 13. A threaded hole matching the lead screw 17 is provided inside the mounting roller 13. Similarly, when the lead screw 17 is rotated, based on the principle of screw drive, the rotation of the lead screw 17 drives the mounting roller 13 to slide in the mounting cavity 14.

[0087] And a screwing member 18 for rotating the lead screw 17, such as a turntable, a polyhedron block, etc., is fixedly provided on the outside of the mandrel 2 of the lead screw 17. The diameter of the screwing member 18 is smaller than the diameter of the mandrel 2.

[0088] Solution 2: Drive through a drive rod

[0089] A sleeve is provided at the end of the mandrel 2. A threaded hole is provided on the side wall of the sleeve and a setscrew is assembled. A drive rod fixedly connected to the mounting roller 13 (such as key connection or pin positioning) is passed through the inside. During adjustment, first loosen the setscrew to release the lock, and push or pull the drive rod manually or mechanically to drive the mounting roller 13 to move axially in the mounting cavity 14; after the position is determined, tighten the setscrew so that its end abuts against the drive rod to achieve fixation.

[0090] A drive handle is fixedly provided on the outside of the mandrel 2 of the drive rod for pushing and pulling the drive rod. Similarly, the diameter of the drive handle is smaller than the diameter of the mandrel 2.

[0091] The present invention is not limited to the above two adjustment methods, and drive devices such as gear-rack drive and worm-gear drive can also be used for driving.

[0092] As Figure 17 As described above, to prevent the mounting roller 13 from rotating when axially moving in the mounting cavity 14 of the mandrel 2, positioning can be achieved through the guiding structure of the rib 30 and the chute 31. Specifically, ribs 30 are provided on the outer wall of the mounting roller 13, and at the same time, chutes 31 matching the ribs 30 are machined on the inner wall of the mandrel 2. The ribs 30 are embedded in the chutes 31, only allowing the mounting roller 13 to slide axially in the mounting cavity 14 and restricting the circumferential rotation of the mounting roller 13. It is also possible to design in the reverse way, with the ribs 30 provided on the inner wall of the mandrel 2 and the chutes 31 opened on the outer wall of the mounting roller 13, and the axial guiding and anti-rotation functions are achieved through the same principle.

[0093] As Figure 5As shown in the figure, to ensure smooth axial movement of the installation roller 13 within the installation cavity 14, both the input flow channel 7 and the return flow channel 8 are equipped with flexible connecting pipes 29. That is, a section of the input flow channel 7 is connected through the flexible connecting pipe 29, and a section of the return flow channel 8 is also connected through the flexible connecting pipe 29. Moreover, part or the whole of the connecting pipe 29 is installed within the installation cavity 14. Due to the bending property of the connecting pipe 29, it can adaptively deform along with the movement trajectory when the installation roller 13 moves axially within the installation cavity 14, avoiding mechanical interference caused by rigid connection, thus ensuring smooth movement of the installation roller 13 without obstruction.

[0094] As Figure 13 shown in the figure, to achieve precise adjustment of the position of the installation roller 13, a specific observation port 16 is opened on the outer wall of the mandrel 2, and a transparent component is assembled within the observation port 16. The outer wall of this transparent component is precisely processed to be completely flush with the outer wall of the mandrel 2 and have the same curvature, forming a continuous and smooth outer surface. This ensures that during the contact or relative movement between the mandrel 2 and the pipe, no frictional resistance is generated due to unevenness or steps on the outer wall, nor will it cause scratches or jams on the surface of the pipe. The transparent component is made of high-temperature resistant materials (such as quartz glass, borosilicate glass, etc.). The inner wall of the transparent component does not protrude beyond the inner wall of the mandrel 2, ensuring a clear observation field of view while avoiding obstruction of the movement of the installation roller 13 by the inner wall of the transparent component. Through this design, the staff can directly observe the real-time movement position of the installation roller 13 inside the mandrel 2 through the observation port 16 and the transparent component, achieving dynamic calibration of the axial movement distance and positioning accuracy of the installation roller 13, and ensuring high-precision operation requirements of the equipment during the pipe cooling process.

[0095] When driving the installation roller 13 to move by the driving rod using the above-mentioned second solution, scale lines can also be marked on the outer wall of the driving rod to achieve precise adjustment of the installation roller 13. The scale lines are precisely calibrated according to the movement accuracy requirements of the installation roller 13. The staff can directly obtain the real-time position of the installation roller 13 by reading the scale changes when the driving rod moves.

[0096] As Figure 5 and 13 shown in the figure, to facilitate the maintenance and replacement of the installation roller 13, a detachable end cap 15 is provided at the end of the mandrel 2. The end cap 15 can be detachably connected to the mandrel 2 by means of threaded connection. The lead screw 17 or the driving rod can be connected to the end cap 15 through the corresponding connection methods mentioned above. The lead screw 17 is connected to the end cap 15 by threading, and the driving rod passes through the end cap 15. When it is necessary to disassemble and assemble the installation roller 13 inside the mandrel 2, simply open the end cap 15, and then the installation roller 13 inside the mandrel 2 can be conveniently replaced, disassembled, and assembled, effectively improving the convenience and efficiency of maintaining, disassembling, and assembling the installation roller 13.

[0097] In summary, for the pipe extrusion forming head, when in use, start the extruder, extrude the high-temperature molten material through the forming head, and form a tubular blank through the die gap 9. Introduce a low-temperature cooling medium into the flow cavity 4 inside the mandrel 2 through the input pipe 5 to keep the flow cavity 4 at a low temperature. At the same time, the outer wall of the mandrel 2 is cooled to cool the inner wall of the extruded pipe. Cooperate with the traditional cooling device to cool the outer wall of the pipe synchronously, realizing balanced cooling of the inner and outer walls. Synchronous cooling of the inner and outer walls shortens the forming time, improves production efficiency, and uniform cooling reduces the deformation of the pipe, improving the quality of pipe forming.

[0098] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A pipe extrusion forming head, comprising a die (1) installed externally and a mandrel (2) installed internally, a die gap (9) is formed between the mandrel (2) and the die (1) for extruding pipes, and it is characterized in that: The end of the mandrel (2) extends axially along the direction of the extruded pipe and extends a certain distance outside the die (1). A flow cavity (4) is provided inside the mandrel (2), and an input flow channel (7) and a return flow channel (8) communicating with the flow cavity (4) are provided inside the mandrel (2); a part of the mandrel (2) located inside the forming head is connected with an input pipe (5) communicating with the input flow channel (7) and a return pipe (6) communicating with the return flow channel (8), and both the input pipe (5) and the return pipe (6) penetrate through the outer wall of the forming head; a medium for cooling is input into the flow cavity (4) through the input pipe (5), and the medium flows in the flow cavity (4) to cool the mandrel (2). The cooled mandrel (2) is used to cool the inner wall of the extruded pipe, and finally the medium is discharged by the return pipe (6).

2. The pipe extrusion forming head according to claim 1, characterized in that: The flow cavity (4) inside the mandrel (2) is in close contact with the outer wall of the mandrel (2).

3. The pipe extrusion forming head according to claim 1, wherein: The input flow channel (7) communicates with one end of the flow cavity (4) close to the forming head, and the return flow channel (8) communicates with one end of the flow cavity (4) far from the forming head.

4. The pipe extrusion forming head according to claim 1, wherein: A number of baffles (10) are provided in the flow cavity (4), and the baffles (10) divide the flow cavity (4) into a number of independent cavities (11).

5. The pipe extrusion forming head according to claim 4, wherein: The cavities (11) communicate with the input flow channel (7) and the return flow channel (8) respectively through branch flow channels (12).

6. The pipe extrusion forming head according to claim 1 or 4, characterized in that: An installation roller (13) is provided inside the mandrel (2), the flow cavity (4) is arranged inside the installation roller (13) inside the mandrel (2), and the input flow channel (7) and the return flow channel (8) are also arranged inside the installation roller (13) inside the mandrel (2).

7. The pipe extrusion forming head according to claim 6, characterized in that: An installation cavity (14) for installing the installation roller (13) is opened inside the mandrel (2), the length of the installation cavity (14) is longer than that of the installation roller (13), and the installation roller (13) can move axially along the mandrel (2) inside the installation cavity (14) to adjust the position of the installation roller (13).

8. The pipe extrusion forming head according to claim 7, wherein: A lead screw (17) is installed at the end of the mandrel (2) extending outward, one end of the lead screw (17) is connected with the installation roller (13), and rotating the lead screw (17) can drive the installation roller (13) to move axially along the mandrel (2) inside the installation cavity (14).

9. The pipe extrusion forming head according to claim 7 or 8, characterized in that: Both the input flow channel (7) and the return flow channel (8) have bendable connecting pipes (29), and the connecting pipes (29) are installed inside the installation cavity (14).

10. The pipe extrusion forming head according to claim 9, wherein: An observation port (16) is opened on the outer wall of the mandrel (2), a transparent component is installed in the observation port (16), and the outer wall of the transparent component is consistent with the outer wall of the mandrel (2).

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