Plastic pipe forming machine

Abstract

The invention relates to the technical field of plastic pipe forming, in particular to a plastic pipe forming machine which comprises a feeding device, a spiral extrusion device, an extrusion head and a stretching and expanding device which are sequentially connected in the material advancing direction, and a traction device is arranged on one side of a feeding port of the stretching and expanding device. Through the arrangement of the extrusion head and the stretching and expanding device, extrusion molding, expanding and biaxial orientation of the plastic pipe can be continuously completed, continuous industrial production is achieved, and due to the fact that the tensile strength and the initial modulus in the orientation direction are remarkably improved, and the elongation at break is reduced, the production cost is reduced on the basis that the production quality of the large-diameter plastic pipe is guaranteed. The problems that an existing large-diameter plastic pipe is long in preparation period and low in production efficiency are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic pipe forming, and particularly relates to a plastic pipe forming machine. Background Art

[0002] At present, the plastic pipes used in China mainly include polyethylene (PE), polyvinyl chloride (PVC), and random copolymer polypropylene (PP-R). Among them, the PVC pipes account for the largest share, about 70% of the market share. However, for larger-diameter pipes, the traditional plastic pipe extrusion process is difficult to meet the strength requirements of large-diameter pipes. Due to technical limitations, when preparing larger-diameter plastic pipes at present, generally, they are extruded and formed by a double-screw extruder, then after cooling and shaping, they are transferred to the side of an expanding device. After the plastic pipe is softened by secondary heating, it is axially stretched by a tractor, and radially expanded by a conical part. However, this method has the following problems: Since multiple steps are carried out separately, the preparation cycle is long and the production efficiency is low; during the production process, there are two heating and two cooling operations, which not only increase the preparation cycle but also cause an increase in energy consumption and an increase in production costs. Summary of the Invention

[0003] In order to solve the problems of long preparation cycle and low production efficiency of existing larger-diameter plastic pipes, the present invention provides a plastic pipe forming machine.

[0004] The plastic pipe forming machine provided by the present invention adopts the following technical solutions: A plastic pipe forming machine includes a feeding device, a screw extrusion device, an extrusion head, and a stretching and expanding device connected in sequence along the material traveling direction. A traction device is arranged on one side of the feeding port of the stretching and expanding device; wherein, The extrusion head includes a die and a core die. The core die is fixed in the die through a support frame and is coaxially arranged with it. The gap between the core die and the die forms a forming channel for material flow. The left side of the forming channel is connected to the screw extrusion device, and a first spiral cooling cavity sleeved outside the forming channel is arranged on the right part of the die; The stretching and expanding device includes a fixed sleeve, an outer die, and an inner die. The fixed sleeve is fixed on the right side of the die. The outer die is detachably connected inside the fixed sleeve. The inner die is coaxially arranged inside the outer die. The left side of the inner die is detachably connected to the right side of the core die; a diameter-expanding cover with a gradually increasing radius from left to right is coaxially arranged on the left side of the inner die. The left end of the diameter-expanding cover is hermetically fitted with the core die; the gap between the diameter-expanding cover and the outer die forms a diameter-expanding cavity, and the gap between the outer die and the inner die forms a discharge port. One end of the diameter-expanding cavity is connected to the discharge port, and the other end of the diameter-expanding cavity is connected to the forming channel through the feeding port on the fixed sleeve; an annular water pipe sleeved outside the outer die is arranged on the right side of the fixed sleeve, and a plurality of outer nozzles are evenly distributed on the inner side of the annular water pipe.

[0005] During operation, materials are first added into the screw extrusion device. After being preheated, thermally mixed, and dissolved in the screw extrusion device, they are extruded into the extrusion head. Due to the presence of the core die, the molten materials flow from the center of the screw and disperse into an annular flow, ensuring uniform distribution. Then, they are extruded and formed on the right side of the forming channel. Since the right part of the die is provided with a first spiral cooling cavity sleeved outside the forming channel, the materials can be preliminarily cooled by air cooling during the forming process, making the extruded plastic pipe in a high elastic state. Then, the formed plastic pipe enters the diameter expansion cavity through the feed port and realizes radial expansion under the action of the diameter expansion cover, obtaining a plastic pipe with the required radius. During this process, by utilizing the movement ability of the polymer chain segments in the high elastic state plastic pipe, they are rearranged along the direction of the acting force under the external force to form an ordered structure, thus realizing the radial orientation of the plastic pipe. During the orientation process, the plastic pipe always moves to the right until it is discharged from the discharge port. After being quickly sprayed and cooled by the external spray head of the annular water pipe, it reaches the traction device and is tractioned by the traction device. By quickly cooling down, the movement of the chain segments is frozen to avoid spontaneous disorientation, and the traction process will also axially orient the plastic pipe in the diameter expansion cavity. Therefore, in summary, through the setting of the extrusion head and the stretching and diameter expansion device, the extrusion forming, diameter expansion, and biaxial orientation of the plastic pipe can be continuously completed, realizing continuous industrial production. Since the tensile strength and initial modulus in the orientation direction are significantly improved and the elongation at break is reduced, on the basis of ensuring the production quality of large-diameter plastic pipes, the problems of long preparation cycle and low production efficiency of existing large-diameter plastic pipes are solved.

[0006] Through the two-stage cooling of the first spiral cooling cavity and the external spray head, on the one hand, by using the gentle and uniform air cooling method for cooling, a high elastic state plastic pipe with a relatively high temperature is obtained, so that subsequent orientation does not require secondary heating, achieving the purpose of energy saving. At the same time, without complete cooling and secondary heating, the overall production efficiency is also improved indirectly. On the other hand, by using the method of spraying cooling water, the plastic pipe after orientation is quickly cooled to avoid spontaneous disorientation and ensure the production quality of large-diameter plastic pipes.

[0007] It should be noted that both the outer die and the inner die are detachably connected. Therefore, by replacing the outer die with different inner diameters and the inner die with different outer diameters, the size of the gap at the discharge port can be adjusted, so as to meet the production of plastic pipes with different radii and thicknesses. In actual production, to compensate for expansion, the gap at the discharge port is generally 1.05 - 1.1 times the thickness of the plastic pipe.

[0008] Optionally, the die includes a flow splitting section, a support section, a rectifying section, and an extrusion section connected in sequence from left to right. The support frame is disposed within the support section. A flow splitting cone is provided at the left end of the mandrel within the flow splitting section. The gap between the flow splitting cone and the inner wall of the flow splitting section forms a flow splitting cavity. The gap between the support frames forms a flow through hole. The gap between the mandrel and the rectifying section forms a rectifying cavity. The gap between the mandrel and the extrusion section forms an extrusion cavity. The outer diameter of the mandrel within the extrusion cavity gradually decreases from both sides towards the middle.

[0009] By providing the flow splitting cone, the molten material can be dispersed from the center flow of the screw into an annular flow within the flow splitting cavity. The support frame is provided to support the mandrel and the inner die, and at the same time, the material is split again and enters the rectifying cavity through the flow through hole. The rectifying cavity is provided so that the material split by the support frame can be fully rectified and fused, avoiding the weakening of the weld line. The rectified material then enters the extrusion cavity, and the gap of the extrusion cavity gradually decreases in the advancing direction, thereby completing the extrusion molding.

[0010] Optionally, mounting grooves communicating with each other are provided on the corresponding sides of the mandrel and the inner die. A second water pipe is provided within the mounting groove of the mandrel. The left end of the second water pipe passes through the support frame and the support section and extends outside the support section to communicate with the water inlet pipe. The water inlet pipe is connected to the annular water pipe through the first water pipe. The right end of the second water pipe is detachably connected to a third water pipe within the mounting groove of the inner die through a quick connector. A plurality of radially arranged water guiding holes are provided at intervals along the circumferential direction within the inner die. The third water pipe communicates with the corresponding water guiding holes through a plurality of fourth water pipes. A plurality of inner spray holes communicating with the corresponding water guiding holes are provided on the right side of the inner die.

[0011] By adopting the above technical solution, by using the water inlet pipe, the second water pipe, the third water pipe, the fourth water pipe, and the water guiding holes, external cooling water can be introduced into the inner spray holes, so that the plastic pipe pulled out from the discharge port can be water-cooled from the inside. It can cooperate with the outer spray head to realize the simultaneous internal and external cooling of the plastic pipe, improve the production efficiency, avoid the problem of spontaneous disorientation due to the low cooling efficiency of the plastic pipe, ensure the production quality of larger diameter plastic pipes, and avoid the problem of internal stress generation in the plastic pipe caused by unilateral cooling, further ensuring the production quality.

[0012] Optionally, an annular air pipe is coaxially arranged outside the support section. A third air pipe extending inside each support frame to the mounting groove is provided within the annular air pipe. An air guiding hole communicating with the inner cavity of the mounting groove and the diameter expanding cover is provided on the mandrel. The inner cavity of the diameter expanding cover communicates with the inner spray holes.

[0013] By adopting the above technical solution, cold air is introduced into the installation groove through the annular trachea and the third trachea, and when passing through the thin wall of the core mold located in the extrusion cavity, it can participate in the cooling of the material at the extrusion cavity from the inside, so as to cooperate with the first spiral cooling cavity to realize the internal and external cooling during the extrusion of the plastic pipe, which can not only improve the cooling effect but also improve the cooling efficiency; moreover, the cold air after heat exchange becomes hot air and enters the inner cavity of the diameter expansion cover through the air guiding hole, and the diameter expansion cover is insulated by the hot air, so that the temperature in the diameter expansion cavity is always higher than the glass transition temperature of the material, thereby ensuring the smooth progress of the diameter expansion and orientation of the plastic pipe; then the hot air enters the inner spray hole and is sprayed out after being mixed with the cooling water entering the inner spray hole. On the one hand, introducing the cooling water can make the temperature of the mixed fluid formed in the inner spray hole lower than the temperature of the plastic pipe after orientation in the discharge port, so that non-contact preliminary cooling can be carried out from the inside. On the other hand, the hot air atomizes the cooling water and sprays it out from the inner spray hole, making the cooling on the inner side of the plastic pipe more uniform after the discharge port discharges, improving the cooling effect, and the atomized water droplets mixed with the hot air can also evaporate from the liquid state to the gaseous state more quickly, thereby absorbing a large amount of heat through the vaporization method and further improving the cooling effect.

[0014] Optionally, the inner cavity of the diameter expansion cover is communicated with the inner spray hole through an atomization cavity. The atomization cavity is a Venturi tube structure, and the water guiding hole is communicated with the throat of the atomization cavity.

[0015] By adopting the above technical solution, using the Venturi tube structure of the atomization cavity, the hot air and the cooling water can be mixed at the throat to realize pre-atomization, thereby improving the atomization effect and further improving the subsequent cooling effect.

[0016] Optionally, the diameter expansion cover is sequentially connected with a first diameter expansion section, a second diameter expansion section and a guiding section from left to right. An annular partition plate extending inward is arranged between the second diameter expansion section and the guiding section. The annular partition plate divides the inner cavity of the diameter expansion cover into a non-communicating first cavity and a second cavity. A back pressure valve is arranged on the annular partition plate. The first cavity is communicated with the air guiding hole, and the second cavity is communicated with the atomization cavity; a through hole communicating the first cavity with the diameter expansion cavity is arranged on the second diameter expansion section.

[0017] By adopting the above technical solution, with the provision of the through holes, hot air can be introduced into the diameter-expanding cavity. When the plastic pipe exits from the discharge port and blocks the discharge port, the diameter-expanding cavity between the inner side of the plastic pipe and the second diameter-expanding section becomes an approximately closed space. Therefore, through the back-pressure valve, sufficient back pressure is generated in the first cavity and the diameter-expanding cavity between the inner side of the plastic pipe and the second diameter-expanding section, and then the expansion of the hot air can be utilized to assist the radial orientation of the plastic pipe, making the outer wall of the plastic pipe closely adhere to the outer wall of the diameter-expanding cavity after orientation, so that the shape of the plastic pipe after orientation is more regular, improving the quality of the plastic pipe after production; in addition, the back-pressure valve also increases the pressure difference between the first cavity and the second cavity, thereby increasing the flow rate of the hot air entering the inner spray holes, further improving the cooling effect and cooling efficiency.

[0018] Optionally, the outer die is provided with a second spiral cooling cavity at the discharge port, an air inlet pipe communicating with the second spiral cooling cavity is arranged on the right side of the outer die, and a strip-shaped groove communicating with the second spiral cooling cavity is arranged inside the left part of the outer die; the strip-shaped groove is communicated with the right side of the first spiral cooling cavity through a first air pipe, and the left side of the first spiral cooling cavity is communicated with the annular air pipe through a second air pipe.

[0019] By adopting the above technical solution, with the provision of the first air pipe and the second air pipe, cooling gas can be provided by using a single air inlet pipe, making its structure simple; the cooling gas sequentially passes through the second spiral cooling cavity, the strip-shaped groove, the first air pipe, the first spiral cooling cavity, the second air pipe, the installation groove, the air guide holes, the first cavity, the second cavity and the atomization cavity and then enters the inner spray holes, so that it can not only meet the requirements of cooling the inner and outer sides of the extrusion section, the inner and outer sides of the discharge port and the inner side atomization cooling of the plastic pipe after discharge, but also form hot air to provide conditions for heat preservation of the orientation in the diameter-expanding cavity after multiple heat exchanges along the way, so that secondary heating is not required, achieving the purpose of energy conservation and environmental protection.

[0020] Optionally, the strip-shaped groove is communicated with the upper wall of the diameter-expanding cavity through an inclined groove.

[0021] By adopting the above technical solution, the high-speed air flow in the strip-shaped groove forms negative pressure at the inclined groove, and then sucks the air in the diameter-expanding cavity outside the outer diameter of the plastic pipe, assisting the radial orientation of the plastic pipe, thereby improving the orientation efficiency.

[0022] Optionally, both the third air pipe and the second water pipe are made of heat-insulating materials.

[0023] By adopting the above technical solution, it can be avoided that the cooling gas or cooling water cools the molten material at the support frame, thereby ensuring the uniform flow of the material in the support section and avoiding the influence on the forming quality caused by the retention of the melt.

[0024] In summary, the present invention includes at least one of the following beneficial technical effects: 1. By providing an extrusion head and a stretching and diameter-expanding device, the extrusion molding, diameter expansion, and biaxial orientation of plastic pipes can be continuously completed, enabling continuous industrial production. Since the tensile strength and initial modulus in the orientation direction are significantly increased, and the elongation at break is decreased, on the basis of ensuring the production quality of large-diameter plastic pipes, the problems of long preparation cycle and low production efficiency of existing large-diameter plastic pipes are solved.

[0025] 2. By adopting the above technical solution, using the water inlet pipe, the second water pipe, the third water pipe, the fourth water pipe, and the water diversion holes, external cooling water can be introduced into the inner spray holes, so that the plastic pipes drawn out from the discharge port can be water-cooled from the inside. This can not only cooperate with the outer spray head to achieve simultaneous internal and external cooling of the plastic pipes, improve production efficiency, and avoid the problem of spontaneous disorientation due to low cooling efficiency of the plastic pipes, ensuring the production quality of large-diameter plastic pipes, but also avoid the problem of internal stress generation in the plastic pipes caused by unilateral cooling, further ensuring the production quality.

[0026] 3. By means of the back pressure valve, sufficient back pressure is generated in the first chamber and the diameter-expanding chamber between the inner side of the plastic pipe and the second diameter-expanding section. Furthermore, the radial orientation of the plastic pipe can be assisted by the expansion of hot air, so that the outer wall of the plastic pipe closely adheres to the outer wall of the diameter-expanding chamber after orientation, making the shape of the plastic pipe more regular after orientation and improving the quality of the plastic pipe after production. In addition, the back pressure valve also increases the pressure difference between the first chamber and the second chamber, thereby increasing the flow rate of the hot air entering the inner spray holes and further improving the cooling effect and cooling efficiency. Description of the Drawings

[0027] Figure 1 is a perspective view of the extrusion head and the stretching and diameter-expanding device of the present invention from one perspective; Figure 2 is a perspective view of the extrusion head and the stretching and diameter-expanding device of the present invention from another perspective; Figure 3 is a left view of the present invention; Figure 4 is Figure 3 a cross-sectional view taken along the A-A direction in Figure 5 is Figure 4 a partial enlarged view at B in Figure 6 is a cross-sectional view of the stretching and diameter-expanding device of the present invention; Figure 7 is Figure 6 a partial enlarged view at C in Figure 8 is Figure 6 a partial enlarged view at D in Figure 9 is a perspective view of the present invention after removing the traction device.

[0028] Description of the drawing reference numerals: 1. Shunt section; 11. Shunt cavity; 2. Support section; 21. Flow-through hole; 22. Support frame; 3. Rectifying section; 31. Rectifying cavity; 4. Extrusion section; 41. Extrusion cavity; 42. First spiral cooling cavity; 5. Stretching and diameter-expanding device; 51. Fixed sleeve; 52. Outer die; 53. Inner die; 54. Discharge port; 55. Second spiral cooling cavity; 56. Strip-shaped groove; 57. Diameter-expanding cover; 571. First diameter-expanding section; 572. Second diameter-expanding section; 573. First cavity; 574. Through hole; 575. Annular partition; 576. Guide section; 577. Second cavity; 578. Back pressure valve; 579. Atomization cavity; 58. Diameter-expanding cavity; 59. Feed port; 6. Air inlet pipe; 61. First air pipe; 62. Second air pipe; 63. Annular air pipe; 64. Third air pipe; 65. Inclined groove; 7. Water inlet pipe; 71. First water pipe; 72. Annular water pipe; 73. Outer spray head; 74. Inner spray hole; 75. Second water pipe; 76. Quick-connect joint; 77. Third water pipe; 78. Fourth water pipe; 79. Water diversion hole; 8. Core die; 81. Shunt cone; 82. Installation groove; 83. Air guide hole; 9. Spiral extrusion device. Detailed implementation manners

[0029] The following is a further detailed description of the present invention in conjunction with the attached Figure 1 - Figure 9 drawings.

[0030] An embodiment of the present invention discloses a plastic pipe forming machine.

[0031] It should be noted that in the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0032] Referring to Figure 1 - Figure 9 , a plastic pipe forming machine includes a feeding device, a spiral extrusion device 9, an extrusion head and a stretching and diameter-expanding device 5 connected in sequence along the material traveling direction, and a traction device is arranged on one side of the feed port 59 of the stretching and diameter-expanding device 5; wherein, The extrusion head includes a die and a core die 8. The core die 8 is fixed in the die through a support frame 22 and is coaxially arranged with it. The gap between the core die 8 and the die forms a forming channel for material flow. The left side of the forming channel is communicated with the spiral extrusion device 9, and a first spiral cooling cavity 42 sleeved outside the forming channel is arranged on the right part of the die; The stretching and diameter-expanding device 5 includes a fixed sleeve 51, an outer die 52 and an inner die 53. The fixed sleeve 51 is fixed to the right side of the die head. The outer die 52 is detachably connected inside the fixed sleeve 51. The inner die 53 is coaxially arranged inside the outer die 52. The left side of the inner die 53 is detachably connected to the right side of the core die 8. A diameter-expanding cover 57 with a gradually increasing radius from left to right is coaxially arranged on the left side of the inner die 53. The left end of the diameter-expanding cover 57 is in sealing fit with the core die 8. The gap between the diameter-expanding cover 57 and the outer die 52 forms a diameter-expanding cavity 58. The gap between the outer die 52 and the inner die 53 forms a discharge port 54. One end of the diameter-expanding cavity 58 is communicated with the discharge port 54, and the other end of the diameter-expanding cavity 58 is communicated with the forming channel through a feed port 59 on the fixed sleeve 51. A ring-shaped water pipe 72 sleeved outside the outer die 52 is arranged on the right side of the fixed sleeve 51. A plurality of outer spray heads 73 are evenly distributed on the inner side of the ring-shaped water pipe 72.

[0033] During operation, first, the material is added into the screw extrusion device 9. After being preheated, thermally mixed and dissolved in the screw extrusion device 9, it is extruded into the extrusion head. Due to the presence of the core die 8, the molten material flows from the center of the screw and is dispersed into an annular flow to ensure uniform distribution. Then it is extruded and formed after passing through the right side of the forming channel. Since a first spiral cooling cavity 42 sleeved outside the forming channel is arranged on the right part of the die head, the material can be preliminarily cooled by air cooling during the forming process, so that the extruded and formed plastic pipe is in a highly elastic state. Then the formed plastic pipe enters the diameter-expanding cavity 58 through the feed port 59 and realizes radial diameter expansion under the action of the diameter-expanding cover 57 to obtain a plastic pipe with the required radius. During this process, the movement ability of the polymer chain segments in the highly elastic plastic pipe is utilized to make them rearrange along the acting force direction under the external force to form an ordered structure, thereby realizing the radial orientation of the plastic pipe. During the orientation process, the plastic pipe always moves to the right until it is discharged from the discharge port 54, and is quickly sprayed and cooled by the outer spray heads 73 of the ring-shaped water pipe 72 and then reaches the traction device where it is tractioned by the traction device. The movement of the chain segments is frozen by rapid cooling to avoid spontaneous disorientation, and the traction process will also axially orient the plastic pipe in the diameter-expanding cavity 58. Therefore, in summary, through the setting of the extrusion head and the stretching and diameter-expanding device 5, the extrusion forming, diameter expansion and biaxial orientation of the plastic pipe can be continuously completed, realizing continuous industrial production. Since the tensile strength and initial modulus in the orientation direction are significantly improved and the elongation at break is reduced, the problems of long preparation period and low production efficiency of the existing large-diameter plastic pipes are solved while ensuring the production quality of large-diameter plastic pipes.

[0034] Through the two-stage cooling of the first spiral cooling chamber 42 and the outer nozzle 73, on the one hand, cooling is carried out in a gentle and uniform way by air cooling to obtain a highly elastic plastic pipe at a relatively high temperature, so that subsequent orientation does not require secondary heating, achieving the purpose of energy saving. At the same time, without complete cooling and secondary heating, the overall production efficiency is also increased indirectly; on the other hand, the rapid cooling of the plastic pipe after orientation is realized by spraying cooling water, avoiding spontaneous disorientation and ensuring the production quality of large-diameter plastic pipes.

[0035] It should be noted that both the outer die 52 and the inner die 53 are detachably connected. Therefore, by replacing the outer die 52 with different inner diameters and the inner die 53 with different outer diameters, the size of the gap at the discharge port 54 can be adjusted to meet the production of plastic pipes with different radii and thicknesses; in actual production, to compensate for expansion, the gap at the discharge port 54 is generally 1.05 - 1.1 times the thickness of the plastic pipe.

[0036] As an optional technical solution, the die head includes a distribution section 1, a support section 2, a rectification section 3, and an extrusion section 4 connected in sequence from left to right. The support frame 22 is arranged in the support section 2, and a distribution cone 81 is arranged at the left end of the mandrel 8 in the distribution section 1; the gap between the distribution cone 81 and the inner wall of the distribution section 1 forms a distribution cavity 11, the gap between the support frames 22 forms a through-flow hole 21, the gap between the mandrel 8 and the rectification section 3 forms a rectification cavity 31, and the gap between the mandrel 8 and the extrusion section 4 forms an extrusion cavity 41; the outer diameter of the mandrel 8 in the extrusion cavity 41 gradually decreases from both sides to the middle.

[0037] Through the setting of the distribution cone 81, the molten material can be dispersed from the center flow of the screw into an annular flow in the distribution cavity 11; the support frame 22 is set to support the mandrel 8 and the inner die 53, and at the same time, the material is further divided and enters the rectification cavity 31 through the through-flow hole 21; the rectification cavity 31 is set so that the material after being divided by the support frame 22 can be fully rectified and fused to avoid weakening of the weld line; the rectified material then enters the extrusion cavity 41, and the gap of the extrusion cavity 41 gradually decreases in the advancing direction, thus completing the extrusion molding.

[0038] As an optional technical solution, installation grooves 82 communicating with each other are arranged on the corresponding sides of the mandrel 8 and the inner die 53. A second water pipe 75 is arranged in the installation groove 82 of the mandrel 8. The left end of the second water pipe 75 passes through the support frame 22 and the support section 2 and extends outside the support section 2 to be connected with the water inlet pipe 7. The water inlet pipe 7 is connected with the annular water pipe 72 through a first water pipe 71; the right end of the second water pipe 75 is detachably connected with a third water pipe 77 in the installation groove 82 of the inner die 53 through a quick connector 76; a plurality of water guiding holes 79 arranged radially are arranged at intervals along the circumferential direction in the inner die 53, and the third water pipe 77 is connected with the corresponding water guiding holes 79 through a plurality of fourth water pipes 78; a plurality of inner spray holes 74 communicating with the corresponding water guiding holes 79 are arranged on the right side of the inner die 53.

[0039] By adopting the above technical solution, by using the water inlet pipe 7, the second water pipe 75, the third water pipe 77, the fourth water pipe 78 and the water diversion hole 79, external cooling water can be introduced into the inner spray hole 74, so that the plastic pipe drawn out from the discharge port 54 can be water-cooled from the inside. It can cooperate with the outer spray head 73 to realize the simultaneous internal and external cooling of the plastic pipe, improve the production efficiency, avoid the problem of spontaneous orientation due to the low cooling efficiency of the plastic pipe, ensure the production quality of large-diameter plastic pipes, and avoid the problem of internal stress generated in the plastic pipe due to unilateral cooling, further ensuring the production quality.

[0040] As an alternative technical solution, a ring-shaped air pipe 63 is coaxially arranged outside the support section 2, and a third air pipe 64 extending along the inside of each support frame 22 into the installation groove 82 is arranged in the ring-shaped air pipe 63; an air guide hole 83 communicating the installation groove 82 and the inner cavity of the diameter-expanding cover 57 is arranged on the core mold 8, and the inner cavity of the diameter-expanding cover 57 is communicated with the inner spray hole 74.

[0041] By adopting the above technical solution, cold air is introduced into the installation groove 82 by using the ring-shaped air pipe 63 and the third air pipe 64, and can participate in the cooling of the material at the extrusion cavity 41 from the inside when passing through the thin wall of the core mold 8 located in the extrusion cavity 41, so as to cooperate with the first spiral cooling cavity 42 to realize the internal and external cooling when the plastic pipe is extruded, which can not only improve the cooling effect, but also improve the cooling efficiency; moreover, the cold air after heat exchange becomes hot air and enters the inner cavity of the diameter-expanding cover 57 through the air guide hole 83, and the diameter-expanding cover 57 is insulated by the hot air, so that the temperature in the diameter-expanding cavity 58 is always higher than the glass transition temperature of the material, thereby ensuring the smooth progress of the diameter expansion and orientation of the plastic pipe; then the hot air enters the inner spray hole 74 and is mixed with the cooling water entering the inner spray hole 74 and then sprayed out. On the one hand, introducing the cooling water can make the temperature of the mixed fluid formed in the inner spray hole 74 lower than the temperature of the plastic pipe after orientation in the discharge port 54, so that preliminary cooling can be carried out in a non-contact manner from the inside. On the other hand, the hot air is used to atomize the cooling water and spray it out from the inner spray hole 74, making the cooling on the inner side of the plastic pipe more uniform after the discharge port 54 discharges, improving the cooling effect, and the atomized water droplets mixed with the hot air can also evaporate from the liquid state to the gaseous state more quickly, thereby absorbing a large amount of heat through the vaporization method and further improving the cooling effect.

[0042] As an alternative technical solution, the inner cavity of the diameter-expanding cover 57 is communicated with the inner spray hole 74 through an atomization cavity 579, the atomization cavity 579 is a Venturi tube structure, and the water diversion hole 79 is communicated with the throat of the atomization cavity 579.

[0043] By adopting the above technical solution, by using the Venturi tube structure of the atomization cavity 579, the hot air and the cooling water can be mixed at the throat to realize pre-atomization, thereby improving the atomization effect and further improving the subsequent cooling effect.

[0044] As an alternative technical solution, the diameter-expanding cover 57 includes a first diameter-expanding section 571, a second diameter-expanding section 572, and a guiding section 576 connected in sequence from left to right. An inwardly extending annular partition 575 is provided between the second diameter-expanding section 572 and the guiding section 576. The annular partition 575 divides the inner cavity of the diameter-expanding cover 57 into a non-connected first cavity 573 and a second cavity 577. A back-pressure valve 578 is provided on the annular partition 575. The first cavity 573 is communicated with the air guide hole 83, and the second cavity 577 is communicated with the atomization cavity 579. A through hole 574 communicating the first cavity 573 with the diameter-expanding cavity 58 is provided on the second diameter-expanding section 572.

[0045] By adopting the above technical solution, with the arrangement of the through hole 574, hot air can be introduced into the diameter-expanding cavity 58. When the plastic pipe discharges from the discharge port 54 and blocks the discharge port 54, the diameter-expanding cavity 58 between the inner side of the plastic pipe and the second diameter-expanding section 572 becomes an approximately closed space. Therefore, sufficient back pressure is generated in the first cavity 573 and the diameter-expanding cavity 58 between the inner side of the plastic pipe and the second diameter-expanding section 572 through the back-pressure valve 578. Furthermore, the radial orientation of the plastic pipe can be assisted by the expansion of the hot air, so that the outer wall of the plastic pipe closely adheres to the outer wall of the diameter-expanding cavity 58 after orientation, thereby making the shape of the plastic pipe more regular after orientation and improving the quality of the plastic pipe after production. In addition, the back-pressure valve 578 also increases the pressure difference between the first cavity 573 and the second cavity 577, thereby increasing the flow rate of the hot air entering the inner spray holes 74 and further improving the cooling effect and cooling efficiency.

[0046] As an alternative technical solution, a second spiral cooling cavity 55 is provided at the discharge port 54 of the outer die 52. An air inlet pipe 6 communicated with the second spiral cooling cavity 55 is provided on the right side of the outer die 52. A strip-shaped groove 56 communicated with the second spiral cooling cavity 55 is provided inside the left part of the outer die 52. The strip-shaped groove 56 is communicated with the right side of the first spiral cooling cavity 42 through a first air pipe 61, and the left side of the first spiral cooling cavity 42 is communicated with an annular air pipe 63 through a second air pipe 62.

[0047] By adopting the above technical solution, with the arrangement of the first air pipe 61 and the second air pipe 62, cooling gas can be provided by using a single air inlet pipe 6, making its structure simple. The cooling gas sequentially passes through the second spiral cooling cavity 55, the strip-shaped groove 56, the first air pipe 61, the first spiral cooling cavity 42, the second air pipe 62, the installation groove 82, the air guide hole 83, the first cavity 573, the second cavity 577, and the atomization cavity 579 and then enters the inner spray holes 74. Thus, it can not only meet the requirements of cooling the inner and outer sides of the extrusion section 4, the inner and outer sides of the discharge port 54, and the inner side atomization cooling of the plastic pipe after discharge, but also form hot air after multiple heat exchanges along the way to provide conditions for improving the orientation insulation in the diameter-expanding cavity 58, so that secondary heating is not required, achieving the purpose of energy conservation and environmental protection.

[0048] As an alternative technical solution, the strip-shaped groove 56 communicates with the upper wall of the diameter-expanding cavity 58 through an inclined groove 65.

[0049] By adopting the above technical solution, the high-speed air flow in the strip-shaped groove 56 forms a negative pressure at the inclined groove 65, and then sucks the air in the diameter-expanding cavity 58 outside the outer diameter of the plastic pipe, assisting the radial orientation of the plastic pipe, thereby improving the orientation efficiency.

[0050] As an alternative technical solution, both the third air pipe 64 and the second water pipe 75 are made of heat-insulating materials.

[0051] By adopting the above technical solution, it is possible to prevent the cooling gas or cooling water from cooling the molten material at the support frame 22, thereby ensuring the uniform flow of the material in the support section 2 and avoiding the influence on the molding quality caused by the melt retention.

[0052] The above are all the preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention shall be covered within the protection scope of the present invention.

Claims

1. A plastic tube forming machine, characterized in that: It comprises a feeding device, a screw extrusion device (9), an extrusion head and a stretching and expanding device (5) which are sequentially connected along the direction of material travel, and a traction device is provided on one side of the feeding port (59) of the stretching and expanding device (5); wherein: The extruder head comprises a mouth die and a core die (8), the core die (8) being fixed in the mouth die through a support frame (22) and being arranged coaxially therewith, the gap between the core die (8) and the mouth die forming a molding channel for material circulation, the left side of the molding channel being connected to a spiral extrusion device (9), and the right side of the mouth die being provided with a first spiral cooling chamber (42) sleeved outside the molding channel; The stretching and expanding device (5) comprises a fixed sleeve (51), an outer die (52) and an inner die (53); the fixed sleeve (51) is fixed to the right side of the die; the outer die (52) is detachably connected to the fixed sleeve (51); the inner die (53) is coaxially arranged in the outer die (52); the left side of the inner die (53) is detachably connected to the right side of the core die (8); an expanding cover (57) with a radius gradually increasing from left to right is coaxially arranged on the left side of the inner die (53); the left end of the expanding cover (57) is sealed with the core die (8); The gap between the outer mold (57) and the outer mold (52) forms an expansion cavity (58), and the gap between the outer mold (52) and the inner mold (53) forms a discharge port (54). One end of the expansion cavity (58) is connected to the discharge port (54), and the other end of the expansion cavity (58) is connected to the molding channel through a feed port (59) on the fixed sleeve (51). An annular water pipe (72) sleeved on the outside of the outer mold (52) is provided on the right side of the fixed sleeve (51), and a plurality of external nozzles (73) are evenly distributed on the inner side of the annular water pipe (72).

2. A plastic tube forming machine according to claim 1, characterized in that: The die comprises a diversion section (1), a support section (2), a rectification section (3) and an extrusion section (4) which are connected in sequence from left to right; the support frame (22) is arranged in the support section (2); a diversion cone (81) is arranged at the left end of the core die (8) in the diversion section (1); a gap between the diversion cone (81) and the inner wall of the diversion section (1) forms a diversion cavity (11); a gap between the support frame (22) forms a flow hole (21); a gap between the core die (8) and the rectification section (3) forms a rectification cavity (31); and a gap between the core die (8) and the extrusion section (4) forms an extrusion cavity (41); and the outer diameter of the core die (8) in the extrusion cavity (41) gradually decreases from both sides to the middle.

3. A plastic tube forming machine according to claim 2, characterized in that: The core mold (8) and the inner mold (53) are both provided with mutually communicating mounting grooves (82) on corresponding sides. A second water pipe (75) is provided in the mounting groove (82) of the core mold (8). The left end of the second water pipe (75) passes through the support frame (22) and the support section (2) and extends to the outside of the support section (2) to communicate with the water inlet pipe (7). The water inlet pipe (7) is communicated with the annular water pipe (72) through the first water pipe (71). The right end of the second water pipe (75) is detachably connected to a third water pipe (77) in the mounting groove (82) of the inner mold (53) through a quick-connect joint (76). A plurality of radially arranged water inlet holes (79) are provided at intervals in the circumferential direction in the inner mold (53). The third water pipe (77) is communicated with the corresponding water inlet holes (79) through a plurality of fourth water pipes (78). A plurality of inner spray holes (74) communicating with the corresponding water inlet holes (79) are provided on the right side of the inner mold (53).

4. A plastic tube forming machine according to claim 3, characterized in that: An annular air pipe (63) is coaxially arranged outside the support section (2), and a third air pipe (64) is arranged inside the annular air pipe (63) and extends along the inside of each support frame (22) to the installation groove (82); an air inlet hole (83) communicating with the installation groove (82) and the inner cavity of the expansion cover (57) is arranged on the core mold (8), and the inner cavity of the expansion cover (57) is communicated with the inner spray hole (74).

5. A plastic tube forming machine according to claim 4, characterized in that: The inner cavity of the expansion cover (57) is connected to the inner spray hole (74) via an atomization cavity (579); the atomization cavity (579) is a Venturi tube structure; the water inlet hole (79) is connected to the throat of the atomization cavity (579).

6. A plastic tube forming machine according to claim 5, characterized in that: The expansion cover (57) comprises a first expansion section (571), a second expansion section (572) and a guide section (576) which are connected in sequence from left to right; an annular baffle (575) extending inward is provided between the second expansion section (572) and the guide section (576); the annular baffle (575) divides the inner cavity of the expansion cover (57) into a first cavity (573) and a second cavity (577) which are not connected; a back pressure valve (578) is provided on the annular baffle (575); the first cavity (573) is connected to the air inlet hole (83); the second cavity (577) is connected to the atomization cavity (579); and a through hole (574) which connects the first cavity (573) and the expansion cavity (58) is provided on the second expansion section (572).

7. A plastic tube forming machine according to claim 6, characterized in that: The outer mold (52) is provided with a second spiral cooling cavity (55) at the discharge port (54); an air inlet pipe (6) communicating with the second spiral cooling cavity (55) is provided on the right side of the outer mold (52); a strip groove (56) communicating with the second spiral cooling cavity (55) is provided in the left part of the outer mold (52); the strip groove (56) is communicated with the right side of the first spiral cooling cavity (42) through the first air pipe (61); and the left side of the first spiral cooling cavity (42) is communicated with the annular air pipe (63) through the second air pipe (62).

8. A plastic tube forming machine according to claim 7, characterized in that: The strip-shaped groove (56) is connected to the upper wall of the diameter-expanding cavity (58) via an inclined groove (65).

9. A plastic tube forming machine according to claim 8, characterized in that: The third air pipe (64) and the second water pipe (75) are both made of heat-insulating materials.

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