Continuous melt compensated thick walled plastic pipe extrusion apparatus

Abstract

This utility model discloses a continuous melt-compensated thick-walled plastic pipe extrusion equipment, belonging to the field of plastic pipe extrusion molding technology. It includes: an extruder, a feeding die, a shaping sleeve assembly, and a traction machine arranged sequentially; a feeding channel is formed between the inner and outer walls of the feeding die, and a melt channel is formed between the inner and outer walls of the shaping sleeve assembly, with the feeding channel and melt channel connected; both the inner and outer walls of the shaping sleeve assembly are integrated with cooling systems to achieve gradient cooling of the pipe from the surface to the interior, causing the pipe at the melt channel outlet to solidify into a solid part, while the inlet end remains molten, forming a conical melt compensation zone; the traction speed of the traction machine is set to be less than the extrusion speed of the extruder, and under the action of extrusion pressure and traction resistance, the melt continuously compensates and fills the solidified pipe core. Through a synergistic mechanism of "simultaneous cooling, shaping, and material replenishment," rapid shaping of the inner and outer walls of the pipe and dynamic core shrinkage are achieved, ensuring uniform pipe wall thickness and eliminating internal defects.

Description

Technical Field

[0001] This utility model belongs to the field of plastic pipe extrusion molding technology, specifically relating to a continuous melt compensation type thick-walled plastic pipe extrusion equipment. Background Technology

[0002] In the manufacturing of plastic pipes, especially in the production of large-diameter, high-wall-to-thickness-ratio thick-walled plastic pipes, extrusion molding is the mainstream process. With the increasing demand for high-performance plastic pipes in infrastructure construction, thick-walled plastic pipes with nominal wall thicknesses exceeding 100mm or even 200mm are being used more and more widely.

[0003] In the existing technology, during the extrusion process of plastic pipes, molten plastic is uniformly extruded through the annular gap of the die to form a pipe blank, and then the outer diameter is shaped and solidified by vacuum shaping sleeve or spray cooling.

[0004] However, for pipes with large wall thickness (especially nominal wall thickness ≥ 150 mm), due to factors such as the weight of the melt itself, differences in cooling rate, and flow instability, the melt is prone to asymmetrical flow or local sagging before it is fully solidified, resulting in obvious wall thickness deviation in the circumferential direction. This uneven wall thickness not only reduces the dimensional accuracy and appearance quality of the product, but also causes structural defects such as stress concentration, decreased compressive strength, and easy cracking during long-term use. Utility Model Content

[0005] This invention addresses the aforementioned problems in the existing technology by proposing a continuous melt-compensated thick-walled plastic pipe extrusion device that can ensure uniform wall thickness of thick-walled pipes.

[0006] This utility model can be achieved through the following technical solutions:

[0007] A continuous melt-compensated thick-walled plastic pipe extrusion device includes:

[0008] An extruder, a feeding die, a shaping sleeve assembly, and a traction machine are arranged sequentially along the material extrusion direction;

[0009] A feeding channel is formed between the inner and outer walls of the feeding mold, and a melt channel is formed between the inner and outer walls of the shaping sleeve assembly. The feeding channel is connected to the melt channel.

[0010] The inner and outer walls of the shaping sleeve assembly are both equipped with a cooling system. The cooling system is configured to perform gradient cooling of the bar material flowing through the melt channel from the surface to the inside. As the traction machine continues to pull the tube, the tube material at the outlet end of the melt channel cools and solidifies to form a solid part, while the tube material at the inlet end of the melt channel is in a molten state and forms a cone-shaped melt compensation zone.

[0011] The traction rate of the traction machine is set to be less than the extrusion rate of the extruder. Under the combined action of extrusion pressure and traction resistance, the melt in the melt compensation zone continuously compensates and fills the solidified pipe core.

[0012] As a further improvement of this utility model, the diameter of the melt compensation zone gradually decreases along the extrusion direction of the pipe and closes at the core position of the pipe. The conical circumferential surface of the melt compensation zone is an inclined surface or an inwardly concave curved surface.

[0013] As a further improvement of this utility model, the shaping sleeve assembly consists of an inner shaping sleeve and an outer shaping sleeve, and the inner shaping sleeve and the outer shaping sleeve together form the melt channel.

[0014] As a further improvement of this utility model, the inner shaping sleeve and the outer shaping sleeve are respectively provided with cooling channels for the flow of cooling medium in their tube walls to form the cooling system.

[0015] As a further improvement of this utility model, the feeding mold includes a mold body and a die, and the extruder, the mold body, the die, and the shaping sleeve are connected in sequence. A first feeding channel is formed in the mold body, and a second feeding channel is formed in the die. The first feeding channel and the second feeding channel are connected to form the feeding channel.

[0016] As a further improvement of this utility model, the first feeding channel includes a first channel section and a second channel section, wherein,

[0017] The cross-sectional area of ​​the first channel section gradually decreases from the inlet end to the outlet end;

[0018] The cross-sectional area of ​​the second channel section increases and then decreases from the inlet end to the outlet end.

[0019] As a further improvement of this utility model, the cross-sectional area of ​​the second feed channel gradually increases from its inlet end to its outlet end, forming a gradually expanding flow channel, wherein,

[0020] The cross-sectional area of ​​the inlet end flow channel of the second feed channel is the same as the cross-sectional area of ​​the outlet end flow channel of the second channel section;

[0021] The cross-sectional area of ​​the outlet end of the second feed channel is the same as the cross-sectional area of ​​the inlet end of the melt channel.

[0022] As a further improvement of this utility model, a heat insulation pad is provided on the connecting end face of the die and the shaping sleeve assembly.

[0023] As a further improvement of this utility model, a spray box is provided between the shaping sleeve assembly and the traction machine.

[0024] As a further improvement of this utility model, the inner cavity of the feeding mold and the shaping sleeve assembly are connected, and an exhaust pipe is provided in the inner cavity. The exhaust pipe passes through the gap between the extruder and the feeding mold and extends outward.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Effectively suppresses circumferential wall thickness deviation and improves dimensional accuracy:

[0027] This equipment utilizes the synergistic effect of gradient cooling and dynamic melt compensation to rapidly cool and solidify the inner and outer surfaces of the pipe while retaining a certain range of molten state in the core and middle areas, forming a controllable "melt compensation zone." Within this zone, continuously applied extrusion pressure drives the melt to flow along a conical path towards the pipe's axis and the middle layer of the wall thickness, filling in microscopic pores and volume shrinkage caused by cooling contraction, gravity sagging, or uneven flow in real time. This continuous compensation mechanism of "cooling, forming, and replenishing simultaneously" breaks through the limitations of "uncontrollable shrinkage after forming" in traditional extrusion, significantly improving material density and completely avoiding common defects in thick-walled pipes such as loose structure, shrinkage cavities, and voids, thereby greatly improving the mechanical strength, pressure resistance, and long-term reliability of the pipe.

[0028] 2. Smaller-sized extruders can be used to process large-diameter, thick-walled pipes, reducing equipment investment costs:

[0029] By adopting a "low extrusion rate" operating mode and relying on the pressure accumulation effect formed by the melt in the shaping sleeve to achieve core feeding, it does not completely rely on the instantaneous output capacity of the extruder to maintain the integrity of the pipe forming. It can achieve equivalent or even better filling effect by using a smaller-sized extruder in combination with optimized flow channel design and pressure feedback mechanism. This not only reduces the performance requirements of the extruder host, reduces equipment procurement costs and plant space occupation, but also improves the flexibility of equipment configuration. It is particularly suitable for small and medium-sized enterprises to carry out low-cost trial production and production of high value-added thick-walled pipes.

[0030] 3. By adjusting the melt pressure through a traction machine, the mold structure is simplified and the process controllability is improved:

[0031] By adjusting the speed of the traction machine to change the traction resistance of the melt, the melt pressure and compensation rate in the shaping zone can be precisely controlled. This pressure control method does not rely on complex flow channel design or in-mold pressure adjustment mechanism, reducing manufacturing difficulty and maintenance costs. At the same time, the traction speed, as an externally adjustable parameter, responds quickly and is easy to operate, facilitating rapid process adjustments according to different materials and specifications, thus improving production flexibility and control accuracy. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the layout of the linear thick-walled plastic pipe extrusion equipment according to Embodiment 1 of this utility model;

[0033] Figure 2 This is a schematic diagram of the layout of the bent-tube type thick-walled plastic pipe extrusion equipment according to Embodiment 2 of this utility model.

[0034] In the diagram, 100 is the extruder; 200 is the feeding die; 210 is the die body; 211 is the first feeding channel; 2111 is the first channel section; 2112 is the second channel section; 220 is the die; 221 is the second feeding channel; 300 is the shaping sleeve assembly; 310 is the melt channel; 320 is the inner shaping sleeve; 330 is the outer shaping sleeve; 340 is the cooling channel; 400 is the spray box; 500 is the traction machine; 600 is the pipe; 610 is the melt compensation zone; 700 is the heat insulation pad; and 800 is the exhaust pipe. Detailed Implementation

[0035] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. The technical methods of the present invention will be further described, but the present invention is not limited to these embodiments.

[0036] Example 1

[0037] like Figure 1 As shown, this utility model provides a continuous melt-compensated thick-walled plastic pipe extrusion device, comprising:

[0038] The extruder 100, the feeding die 200, the shaping sleeve assembly 300 and the traction machine 500 are arranged sequentially along the material extrusion direction;

[0039] A feeding channel is formed between the inner and outer walls of the feeding mold 200, and a melt channel 310 is formed between the inner and outer walls of the shaping sleeve assembly 300. The feeding channel and the melt channel 310 are connected.

[0040] The inner and outer walls of the shaping sleeve assembly 300 are both equipped with cooling systems. The cooling system is configured to perform gradient cooling of the bar material flowing through the melt channel 310 from the surface to the inside. As the traction machine 500 continuously pulls the tube 600, the tube 600 located at the outlet end of the melt channel 310 cools and solidifies to form a solid part, while the tube 600 located at the inlet end of the melt channel 310 is in a molten state and forms a cone-shaped melt compensation zone 610.

[0041] The traction rate of the traction machine 500 is set to be less than the extrusion rate of the extruder 100, forming a "slow pull, fast output" operating state. This speed difference causes the melt to generate a combined force that propels it axially toward the core of the pipe wall under the combined action of extrusion pressure and traction resistance. This drives the melt to continuously and uniformly fill the core of the solidified outer pipe wall radially. During this process, since the inner and outer walls of the pipe 600 have been initially cooled and solidified, the compensation filling of the melt can not only improve the density of the pipe 600, but also support the initially solidified inner and outer walls of the pipe 600, so that the outer wall of the pipe 600 is always in close contact with the inner wall of the melt channel 310, thereby improving the uniformity of the wall thickness of the pipe 600.

[0042] The entire compensation process is equivalent to establishing a "self-compensating" mechanism within the 600mm inner wall of the pipe, effectively preventing wall thickness deviations caused by uneven cooling and unstable melt flow. The beneficial effects of this include at least the following:

[0043] 1. Effectively suppresses circumferential wall thickness deviation and improves dimensional accuracy:

[0044] This equipment utilizes the synergistic effect of gradient cooling and dynamic melt compensation to rapidly cool and solidify the inner and outer surfaces of the pipe 600 while retaining a certain range of molten state in the core and middle areas, forming a controllable "melt compensation zone 610". Within this zone, continuously applied extrusion pressure drives the melt to flow along a conical path towards the axis of the pipe 600 and the middle layer of the wall thickness, filling in microscopic pores and volume shrinkage caused by cooling shrinkage, gravity sagging, or uneven flow in real time. This continuous compensation mechanism of "cooling, forming, and replenishing simultaneously" breaks through the limitations of "uncontrollable shrinkage after forming" in traditional extrusion, significantly improving material density and completely avoiding defects such as loose structure, shrinkage cavities, and voids common in thick-walled pipes, thereby greatly improving the mechanical strength, pressure resistance, and long-term reliability of the pipe 600.

[0045] 2. A smaller-sized extruder (100mm) can be used to process large-diameter, thick-walled pipes (600mm), reducing equipment investment costs.

[0046] By adopting a "low extrusion rate" operating mode and relying on the pressure accumulation effect formed by the melt in the shaping sleeve to achieve core feeding, it does not completely rely on the instantaneous output capacity of the extruder 100 to maintain the complete forming of the pipe 600. An equivalent or even better filling effect can be achieved by using a smaller-sized extruder 100 in conjunction with an optimized flow channel design and pressure feedback mechanism. This not only reduces the performance requirements of the extruder host, reduces equipment procurement costs and plant space occupation, but also improves the flexibility of equipment configuration. It is particularly suitable for small and medium-sized enterprises to carry out low-cost trial production and manufacturing of high-value-added thick-walled pipes 600.

[0047] 3. By adjusting the melt pressure using the traction machine 500, the mold structure is simplified and the process controllability is improved:

[0048] By adjusting the speed of the traction machine 500, the traction resistance to the melt is changed, thereby precisely controlling the melt pressure and compensation rate in the shaping zone. This pressure control method does not rely on complex flow channel design or in-mold pressure adjustment mechanism, reducing manufacturing difficulty and maintenance costs. At the same time, the traction speed, as an externally adjustable parameter, responds quickly and is easy to operate, facilitating rapid process adjustments according to different materials and specifications, thus improving production flexibility and control accuracy.

[0049] Overall, the solution provided in this embodiment, through an innovative continuous melt compensation mechanism, not only solves the industry problem of uneven wall thickness and core defects in large-diameter thick-walled pipes 600, but also achieves multiple technological advancements such as cost reduction in equipment, simplification of molds, and ease of process control while ensuring product quality, thus having significant industrial application value.

[0050] Preferably, the diameter of the melt compensation zone 610 gradually decreases along the extrusion direction of the pipe 600 and closes at the core position of the pipe 600. The formation of this conical melt compensation zone 610 allows the melt to flow smoothly along the gradually narrowing path during its advancement towards the core, avoiding flow turbulence or stagnation. This facilitates the concentrated and continuous injection of the melt into the core region of the solidifying pipe wall under pressure, achieving efficient and uniform volume compensation. Consequently, this improves the uniformity of the pipe wall thickness and eliminates pores within the pipe 600, suppressing the generation of internal defects.

[0051] Preferably, the conical circumferential surface of the melt compensation zone 610 is an inclined surface or an inwardly concave curved surface, which gives the melt a more reasonable flow channel transition shape during the flow to the core of the tube 600. The inclined surface or the inwardly concave curved surface can effectively guide the melt to flow towards the center along a smooth path, reduce flow resistance and shear stress concentration, and avoid eddies, stagnant material or pressure fluctuations caused by uneven flow. This is conducive to the melt achieving stable and continuous core filling under the synergistic effect of extrusion pressure and traction resistance, improving filling density and further suppressing the generation of internal defects.

[0052] Among them, the concave curved surface can enhance the convergence effect of the melt at the front end of the compensation zone and optimize the pressure transmission efficiency, thereby improving the stability and controllability of the molding process. It is particularly suitable for the uniform and dense continuous production of large cross-section pipes 600.

[0053] Preferably, the shaping sleeve assembly 300 consists of an inner shaping sleeve 320 and an outer shaping sleeve 330, which together form a melt channel 310. The inner shaping sleeve 320 and the outer shaping sleeve 330 are respectively provided with cooling channels 340 for the flow of cooling medium to form a cooling system. This double-sleeve shaping sleeve structure realizes independent cooling control of the inner and outer walls of the melt channel 310. The cooling medium flows evenly through the cooling channels 340 in the inner and outer shaping sleeves 330, and the cooling intensity and temperature distribution of the inner and outer walls can be precisely adjusted, thereby achieving synchronous and balanced gradient cooling of the inner and outer surfaces of the pipe 600.

[0054] This design allows the inner and outer walls of the tube 600 to begin solidification almost simultaneously during the extrusion process, effectively suppressing deformation, wall deviation, or melt sagging caused by unilateral cooling. It significantly improves the uniformity of the circumferential wall thickness and dimensional stability of the tube 600. At the same time, synchronous internal and external cooling accelerates the setting speed, shortens the cooling cycle, and improves production efficiency.

[0055] More importantly, the rapid outer layer shaping provides a stable geometric boundary for the formation of the internal melt compensation zone 610, ensuring that the melt flows orderly towards the core and is compacted within the conical region, thereby achieving integrated molding of thick-walled tubes from the outside in with a dense structure, and significantly reducing the risk of internal defects.

[0056] Preferably, the feeding mold 200 includes a mold body 210 and a die 220. The extruder 100, mold body 210, die 220 and shaping sleeve assembly 300 are connected in sequence. A first feeding channel 211 is formed in the mold body 210 and a second feeding channel 221 is formed in the die 220. The first feeding channel 211 and the second feeding channel 221 are connected and form a feeding channel.

[0057] Furthermore, the first feed channel 211 includes a first channel section 2111 and a second channel section 2112, wherein,

[0058] The cross-sectional area of ​​the first channel section 2111 gradually decreases from the inlet end to the outlet end, forming a converging compression channel. This allows the melt from the extruder 100 to be continuously compressed in this section, effectively expelling gas and further compacting the melt, which helps to improve the homogeneity and fluidity of the melt.

[0059] The cross-sectional area of ​​the second channel section 2112 increases and then decreases from the inlet end to the outlet end, forming an "expansion-contraction" type flow channel structure. This structure can release pressure and re-rectify the compressed melt, eliminate uneven flow, balance the circumferential pressure distribution, and prevent the melt from generating deflection or eddies when entering the die 220.

[0060] This stepped optimized flow channel design significantly improves the uniformity and stability of the melt before it enters the die 220 and the subsequent melt channel 310 through the synergistic effect of "compression and densification - rectification and pressure equalization". It not only effectively prevents internal defects caused by gas entrainment and uneven density in the melt, but also provides a reliable flow basis for the symmetrical extrusion of the thick-walled pipe 600 in the circumferential direction.

[0061] Preferably, the cross-sectional area of ​​the second feed channel 221 gradually increases from its inlet end to its outlet end, forming a gradually expanding flow channel, wherein,

[0062] The inlet flow channel cross-sectional area of ​​the second feed channel 221 is the same as that of the second channel section 2112, ensuring that the melt flows through the connection between the mold body 210 and the die 220 without any step change, achieving a smooth transition and avoiding dead flow angles or sudden pressure changes.

[0063] The cross-sectional area of ​​the outlet end of the second feed channel 221 is the same as the cross-sectional area of ​​the inlet end of the melt channel 310, so that a continuous and equal-diameter connected flow channel structure is formed between the outlet of the die 220 and the inlet of the shaping sleeve assembly 300, effectively eliminating melt disturbance or flow deviation caused by geometric abrupt changes.

[0064] The design of the gradually expanding second feed channel 221 not only ensures the smooth introduction of the melt, but also helps to maintain the circumferential pressure balance of the melt in the annular gap, improves the uniformity and centering of the melt when it enters the shaping sleeve, and lays a good foundation for the subsequent formation of a stable and symmetrical conical melt compensation zone 610 in the melt channel 310. The continuous matching design of the overall flow channel not only improves the stability of the extrusion process of the thick-walled pipe 600, but also significantly enhances the uniformity of wall thickness and structural consistency, which is conducive to achieving high-quality and high-precision continuous production.

[0065] Preferably, a heat insulation pad 700 is provided on the connection end face of the die 220 and the shaping sleeve assembly 300 to reduce the heat transfer from the die 220 to the shaping sleeve assembly 300. It should be noted that since the shaping sleeve assembly 300 has a cooling system inside, it needs to maintain a low and stable temperature to achieve rapid shaping of the outer wall of the pipe 600 and gradient cooling from the outside to the inside. If the die 220 and the shaping sleeve assembly 300 are in direct contact, the high-temperature die 220 will continuously conduct heat to the shaping sleeve assembly 300, causing its local temperature to rise, cooling efficiency to decrease, and affecting the dimensional accuracy and surface quality of the pipe 600.

[0066] By setting the heat insulation pad 700, this unexpected heat conduction path is effectively blocked. This not only protects the cooling capacity of the shaping sleeve assembly 300, enabling it to continuously and evenly cool the pipe 600 efficiently, but also helps maintain the thermal stability of the die 220 exit area, preventing the melt from generating stress or flow defects due to excessive temperature difference in the early stage of molding.

[0067] This design achieves physical isolation between the hot and cold zones, ensuring that the cooling process proceeds according to the preset gradient, providing reliable conditions for the melt to form a stable compensation zone in the core, and significantly improving the overall density and forming stability of the 600 tube.

[0068] Preferably, a roundness correction device (not shown in the figure) can be added to the outlet end of the shaping sleeve assembly 300. When the pipe 600 still has a certain thermoplasticity but has a certain strength, it can be subjected to axial rotation extrusion or uniform radial pressure to correct deformation in real time and improve the roundness of the pipe 600.

[0069] Preferably, a spray box 400 is provided between the shaping sleeve assembly 300 and the traction machine 500. The spray box 400 is used to further cool and shape the initially cured pipe 600 evenly. Cooling water is continuously sprayed onto the surface of the pipe 600 through circumferentially arranged water spray holes or spray pipes, so that its temperature is further reduced and tends to be uniform, completing the complete curing process from the surface to the core. After the pipe 600 is cut by a cutting machine, it can be stored.

[0070] Preferably, the inner cavities of the feeding die 200 and the shaping sleeve assembly 300 are connected. An exhaust pipe 800 is provided in the inner cavity. The exhaust pipe 800 passes through the gap between the extruder 100 and the feeding die 200 and extends outward. The exhaust pipe 800 continuously draws high-temperature air from the inner cavity of the pipe 600 and the inner cavity of the shaping sleeve assembly 300, thereby accelerating the cooling of the inner wall of the pipe and reducing the temperature of the inner sizing sleeve 320, and stabilizing the pipe dimensions.

[0071] Example 2

[0072] like Figure 2 As shown, Embodiment 2 provides a continuous melt-compensated plastic bent pipe extrusion equipment. The difference between Embodiment 1 and Embodiment 2 is that Embodiment 1 is for the extrusion of thick-walled straight pipes, while Embodiment 2 is for the extrusion of plastic bent pipes.

[0073] Correspondingly, in Embodiment 2, the sizing sleeve assembly, spray box 400, and traction machine 500 are all set as arc-shaped structures that match the curvature of the bend. The overall principle is the same as in Embodiment 1, so it will not be described again.

[0074] It is worth mentioning that, apart from the different shapes of the sizing sleeve assembly, spray box 400, and traction machine 500, the extruder 100 in Embodiment 1 is preferably located on the end face of the die 210, while the extruder 100 in Embodiment 2 is preferably located on the side of the die 210. This is to prevent interference with the extruder 100 at the end of the die 210 after the bent tube is extruded.

[0075] The technical means disclosed in this utility model are not limited to those described above, but also include technical solutions composed of any combination of the above technical features. The above are specific embodiments of this utility model. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this utility model, and these improvements and modifications are also considered within the scope of protection of this utility model.

[0076] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0077] Furthermore, in this utility model, the use of terms such as "first," "second," and "a" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. The terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly specified. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0078] The technical solutions of the various embodiments of this utility model can be combined with each other, but only if they are based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the protection scope claimed by this utility model.

[0079] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

Claims

1. A continuous melt compensated thick walled plastic pipe extrusion apparatus characterized by, include: An extruder, a feeding die, a shaping sleeve assembly, and a traction machine are arranged sequentially along the material extrusion direction; A feeding channel is formed between the inner and outer walls of the feeding mold, and a melt channel is formed between the inner and outer walls of the shaping sleeve assembly. The feeding channel is connected to the melt channel. The inner and outer walls of the shaping sleeve assembly are both equipped with a cooling system. The cooling system is configured to perform gradient cooling of the bar material flowing through the melt channel from the surface to the inside. As the traction machine continues to pull the tube, the tube material at the outlet end of the melt channel cools and solidifies to form a solid part, while the tube material at the inlet end of the melt channel is in a molten state and forms a cone-shaped melt compensation zone. The traction rate of the traction machine is set to be less than the extrusion rate of the extruder. Under the combined action of extrusion pressure and traction resistance, the melt in the melt compensation zone continuously compensates and fills the pre-solidified core of the pipe.

2. A continuous melt compensated thick walled plastic pipe extrusion apparatus as claimed in claim 1 wherein, The diameter of the melt compensation zone gradually decreases along the extrusion direction of the pipe and closes at the core of the pipe. The conical circumferential surface of the melt compensation zone is an inclined surface or an inwardly concave curved surface.

3. A continuous melt compensated thick walled plastic pipe extrusion apparatus as claimed in claim 1 wherein, The shaping sleeve assembly consists of an inner shaping sleeve and an outer shaping sleeve, and the inner shaping sleeve and the outer shaping sleeve together form the melt channel.

4. A continuous melt compensated thick walled plastic pipe extrusion apparatus as claimed in claim 3 wherein, The inner and outer shaping sleeves are respectively provided with cooling channels for the flow of cooling medium in their tube walls to form the cooling system.

5. A continuous melt compensated thick walled plastic pipe extrusion apparatus as claimed in claim 1 wherein, The feeding die includes a die body and a die. The extruder, the die body, the die, and the shaping sleeve are connected in sequence. A first feeding channel is formed in the die body, and a second feeding channel is formed in the die. The first feeding channel and the second feeding channel are connected to form the feeding channel.

6. A continuous melt compensated thick walled plastic pipe extrusion apparatus as claimed in claim 5 wherein, The first feeding channel includes a first channel section and a second channel section, wherein, The cross-sectional area of ​​the first channel section gradually decreases from the inlet end to the outlet end; The cross-sectional area of ​​the second channel section increases and then decreases from the inlet end to the outlet end.

7. A continuous melt compensated thick walled plastic pipe extrusion apparatus as claimed in claim 6 wherein, The cross-sectional area of ​​the second feed channel gradually increases from its inlet end to its outlet end, forming a gradually expanding flow channel. The cross-sectional area of ​​the inlet end flow channel of the second feed channel is the same as the cross-sectional area of ​​the outlet end flow channel of the second channel section; The cross-sectional area of ​​the outlet end of the second feed channel is the same as the cross-sectional area of ​​the inlet end of the melt channel.

8. A continuous melt-compensated thick-walled plastic pipe extrusion equipment according to claim 5, characterized in that, A heat insulation pad is provided on the connecting end face of the die and the shaping sleeve assembly.

9. A continuous melt compensated thick walled plastic pipe extrusion apparatus as claimed in claim 1 wherein, A spray box is provided between the shaping sleeve assembly and the traction machine.

10. A continuous melt compensated thick walled plastic pipe extrusion apparatus as claimed in claim 1 wherein, The inner cavity of the feeding die and the shaping sleeve assembly is connected. An exhaust pipe is provided in the inner cavity. The exhaust pipe passes through the gap between the extruder and the feeding die and extends outward.

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