A plastic pipe forming machine

Abstract

The present invention relates to the technical field of plastic pipe forming, and particularly relates to a plastic pipe forming machine, which comprises a feeding device, a screw extrusion device, an extrusion head and a stretching and expanding device connected in sequence along the material traveling direction, and a traction device is arranged on one side of the feeding port of the stretching and expanding device. Through the arrangement of the extrusion head and the stretching and expanding device, the present invention can continuously complete the extrusion molding, diameter expansion and biaxial orientation of plastic pipes, 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 period and low production efficiency of existing large-diameter plastic pipes 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, approximately occupying 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 softening the plastic pipe 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 heatings and two coolings, 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:

[0005] 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 stretching and expanding device; wherein,

[0006] 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 communicated with the screw extrusion device, and a first spiral cooling cavity sleeving outside the forming channel is arranged on the right part of the die;

[0007] 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; on the left side of the inner die, a diameter-expanding cover with a gradually increasing radius from left to right is coaxially arranged. The left end of the diameter-expanding cover is in sealed cooperation 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 communicated with the discharge port, and the other end of the diameter-expanding cavity is communicated with the forming channel through a feed port on the fixed sleeve; on the right side of the fixed sleeve, an annular water pipe sleeving outside the outer die is arranged, and a plurality of outer spray heads are evenly distributed on the inner side of the annular water pipe.

[0008] During operation, first, the materials are 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 through 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, 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, and after being quickly sprayed and cooled by the outer 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 perform axial orientation on 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 increased 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.

[0009] Through the two-stage cooling of the first spiral cooling cavity and the outer 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 increased 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.

[0010] 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.

[0011] Optionally, the die includes a shunting 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 shunting cone is provided at the left end of the mandrel within the shunting section. The gap between the shunting cone and the inner wall of the shunting section forms a shunting 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.

[0012] By providing the shunting cone, the molten material can be dispersed from the center flow of the screw into a circular flow within the shunting cavity. The support frame is provided to support the mandrel and the inner die, and at the same time, the material is shunted again and enters the rectifying cavity through the flow-through hole. The rectifying cavity is provided so that the material shunted by the support frame can be fully rectified and fused to avoid 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.

[0013] 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 in 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 a first water pipe. The right end of the second water pipe is detachably connected to a third water pipe in 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.

[0014] By adopting the above technical solution, external cooling water can be introduced into the inner spray holes by using the water inlet pipe, the second water pipe, the third water pipe, the fourth water pipes, and the water guiding holes. Thus, the plastic pipe pulled out from the discharge port can be water-cooled from the inside, which can not only cooperate with the outer spray head to realize simultaneous internal and external cooling of the plastic pipe, improve the production efficiency and avoid the problem of spontaneous disorientation due to low cooling efficiency of the plastic pipe, ensure the production quality of larger-diameter plastic pipes, but also avoid the problem of internal stress generated in the plastic pipe due to unilateral cooling, further ensuring the production quality.

[0015] Optionally, a ring-shaped 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 ring-shaped 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.

[0016] 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-walled part of the core mold 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-expanding cover through the air guiding hole, and the diameter-expanding cover is thermally insulated by the hot air, so that the temperature in the diameter-expanding 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 it can be preliminarily cooled in a non-contact manner 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.

[0017] Optionally, the inner cavity of the diameter-expanding cover is communicated with the inner spray hole through an atomization cavity, the atomization cavity is of a Venturi tube structure, and the water guiding hole is communicated with the throat of the atomization cavity.

[0018] 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 achieve pre-atomization, thereby improving the atomization effect and further improving the subsequent cooling effect.

[0019] Optionally, the diameter-expanding cover is sequentially connected with a first diameter-expanding section, a second diameter-expanding section and a guiding section from left to right. An annular partition extending inward is arranged between the second diameter-expanding section and the guiding section. The annular partition divides the inner cavity of the diameter-expanding cover into a non-communicating first cavity and a second cavity. A back pressure valve is arranged on the annular partition. 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 and the diameter-expanding cavity is arranged on the second diameter-expanding section.

[0020] By adopting the above technical solution, with the arrangement of the through holes, hot air can be introduced into the diameter expansion cavity. When the plastic pipe exits from the discharge port and blocks the discharge port, the diameter expansion cavity between the inner side of the plastic pipe and the second diameter expansion section becomes an approximately enclosed space. Therefore, through the back pressure valve, sufficient back pressure is generated in the first cavity and the diameter expansion cavity between the inner side of the plastic pipe and the second diameter expansion section. Furthermore, the radial orientation of the plastic pipe can be assisted by the expansion of the hot air, making the outer wall of the plastic pipe closely adhere to the outer wall of the diameter expansion 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.

[0021] Optionally, the outer mold 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 mold, and a strip-shaped groove communicating with the second spiral cooling cavity is arranged inside the left part of the outer mold; 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.

[0022] By adopting the above technical solution, with the arrangement 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 guiding 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 the orientation heat preservation in the diameter expansion cavity after multiple heat exchanges along the way, so that secondary heating is not required, achieving the purpose of energy conservation and environmental protection.

[0023] Optionally, the strip-shaped groove is communicated with the upper wall of the diameter expansion cavity through an inclined groove.

[0024] 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 expansion cavity outside the outer diameter of the plastic pipe, assisting the radial orientation of the plastic pipe, thereby improving the orientation efficiency.

[0025] Optionally, both the third air pipe and the second water pipe are made of heat-insulating materials.

[0026] By adopting the above technical solution, it can prevent the cooling gas or cooling water from cooling the molten material at the support frame, thus ensuring the uniform flow of the material in the support section and avoiding the influence on the molding quality caused by the melt retention.

[0027] In summary, the present invention includes at least one of the following beneficial technical effects:

[0028] 1. By setting up the extrusion head and the stretching and diameter-expanding device, the extrusion molding, diameter expansion, and biaxial orientation of plastic pipes 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.

[0029] 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. It can not only cooperate with the outer spray head to realize the simultaneous internal and external cooling of the plastic pipes, improve the 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 generated in the plastic pipes caused by unilateral cooling, further ensuring the production quality.

[0030] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a perspective view of the extrusion head and the stretching and diameter-expanding device of the present invention from one perspective;

[0032] Figure 2 is a perspective view of the extrusion head and the stretching and diameter-expanding device of the present invention from another perspective;

[0033] Figure 3 is a left view of the present invention;

[0034] Figure 4 is Figure 3 a cross-sectional view taken along the A-A direction in

[0035] Figure 5 is Figure 4 a partial enlarged view at B in

[0036] Figure 6 is a cross-sectional view of the stretching and diameter-expanding device of the present invention;

[0037] Figure 7 is Figure 6 a partial enlarged view at C in

[0038] Figure 8 isFigure 6 Partial enlarged view at D in the [Chinese description];

[0039] Figure 9 Isometric view of the present invention after removing the traction device.

[0040] Explanation of reference numerals:

[0041] 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 mold; 81. Shunt cone; 82. Installation groove; 83. Air guide hole; 9. Spiral extrusion device. Detailed implementation manners

[0042] The following further describes the present invention in detail with reference to the Figure 1 - Figure 9 accompanying drawings.

[0043] An embodiment of the present invention discloses a plastic pipe forming machine.

[0044] 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 accompanying drawings. It is 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.

[0045] 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 that are sequentially connected along the material traveling direction. A traction device is provided on one side of the stretching and diameter-expanding device 5; wherein,

[0046] The extrusion head includes a die and a core die 8. The core die 8 is fixed inside 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 the material to flow through. The left side of the forming channel is connected to a screw extrusion device 9. A first spiral cooling chamber 42 sleeving outside the forming channel is arranged at the right part of the die.

[0047] 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 on the right side of the die. 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 cooperation with the core die 8. The gap between the diameter-expanding cover 57 and the outer die 52 forms a diameter-expanding chamber 58. The gap between the outer die 52 and the inner die 53 forms a discharge port 54. One end of the diameter-expanding chamber 58 is connected to the discharge port 54, and the other end of the diameter-expanding chamber 58 is connected to the forming channel through a feed port 59 on the fixed sleeve 51. A ring-shaped water pipe 72 sleeving outside the outer die 52 is arranged on the right side of the fixed sleeve 51. A plurality of outer spray nozzles 73 are evenly distributed on the inner side of the ring-shaped water pipe 72.

[0048] 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 is dispersed from the center of the screw into a ring-shaped flow, ensuring uniform distribution. Then it is extruded and formed through the right side of the forming channel. Since the first spiral cooling chamber 42 sleeving outside the forming channel is arranged at the right part of the die, the material 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-expanding chamber 58 through the feed port 59 and realizes radial diameter expansion under the action of the diameter-expanding cover 57, 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 54, and is quickly sprayed and cooled by the outer spray nozzles 73 of the ring-shaped water pipe 72 and then reaches the traction device where it 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 perform axial orientation on the plastic pipe in the diameter-expanding chamber 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 problem of long preparation cycle and low production efficiency of existing large-diameter plastic pipes is solved while ensuring the production quality of large-diameter plastic pipes.

[0049] Through the two-stage cooling of the first spiral cooling chamber 42 and the outer nozzle 73, on the one hand, the high-elastic plastic pipe at a relatively high temperature is cooled in a gentle and uniform manner by air cooling, 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, 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.

[0050] 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 adjustment of the gap size of the discharge port 54 can be realized, so as to meet the production of plastic pipes with different radii and thicknesses; in actual production, to compensate for expansion, the gap of the discharge port 54 is generally 1.05-1.1 times the thickness of the plastic pipe.

[0051] 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 core die 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 core die 8 and the rectification section 3 forms a rectification cavity 31, and the gap between the core die 8 and the extrusion section 4 forms an extrusion cavity 41; the outer diameter of the core die 8 in the extrusion cavity 41 gradually decreases from both sides to the middle.

[0052] Through the setting of the distribution cone 81, the molten material can be dispersed from the center flow of the screw into a ring flow in the distribution cavity 11; the support frame 22 is set to support the core die 8 and the inner die 53, and at the same time, the material is shunted again and enters the rectification cavity 31 through the through-flow hole 21; the rectification cavity 31 is set so that the material shunted 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.

[0053] As an optional technical solution, installation grooves 82 communicating with each other are arranged on the corresponding sides of the core die 8 and the inner die 53. A second water pipe 75 is arranged in the installation groove 82 of the core die 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 the 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-connect joint 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.

[0054] 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 the plastic pipe with a larger diameter, and avoid the problem of internal stress generated in the plastic pipe due to unilateral cooling, further ensuring the production quality.

[0055] 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.

[0056] 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 hot air after heat exchange enters the inner cavity of the diameter-expanding cover 57 through the air guide hole 83, and the diameter-expanding cover 57 is thermally 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 sprayed out after being mixed with the cooling water entering the inner spray hole 74. 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 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 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, so as to absorb a large amount of heat by vaporization, further improving the cooling effect.

[0057] 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.

[0058] 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.

[0059] As an alternative technical solution, the diameter-expanding cover 57 is composed of 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 annular partition plate 575 extending inward is arranged between the second diameter-expanding section 572 and the guiding section 576. The annular partition plate 575 divides the inner cavity of the diameter-expanding cover 57 into a non-communicating first cavity 573 and a second cavity 577. A back-pressure valve 578 is arranged on the annular partition plate 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 arranged on the second diameter-expanding section 572.

[0060] 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.

[0061] As an alternative technical solution, a second spiral cooling cavity 55 is arranged at the discharge port 54 of the outer die 52. An air inlet pipe 6 communicated with the second spiral cooling cavity 55 is arranged on the right side of the outer die 52. A strip-shaped groove 56 communicated with the second spiral cooling cavity 55 is arranged 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.

[0062] 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 heat preservation in the diameter-expanding cavity 58, so that secondary heating is not required, achieving the purpose of energy conservation and environmental protection.

[0063] 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.

[0064] By adopting the above technical solution, the high-speed airflow 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.

[0065] As an alternative technical solution, both the third air pipe 64 and the second water pipe 75 are made of heat-insulating materials.

[0066] 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 retention of the melt.

[0067] The above are all the preferred embodiments of the present invention, and the protection scope of the present invention is not limited accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A plastic pipe forming machine, characterized in that, It includes a feeding device, a screw extrusion device (9), an extrusion head and a stretching and diameter-expanding device (5) which are connected in sequence along the material traveling direction; among them, 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 screw extrusion device (9). A first spiral cooling cavity (42) sleeving outside the forming channel is arranged at 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 on the right side of the die. 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 with 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 sealed cooperation 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). 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). An annular water pipe (72) sleeving outside the outer die (52) is arranged on the right side of the fixed sleeve (51). A plurality of outer spray nozzles (73) are evenly distributed on the inner side of the annular water pipe (72). The die includes a flow distribution section (1), a support section (2), a rectifying section (3) and an extrusion section (4) which are connected in sequence from left to right. A ring-shaped air pipe (63) is coaxially arranged outside the support section (2). Installation grooves (82) which are communicated with each other are arranged on the corresponding sides of the core die (8) and the inner die (53). A third air pipe (64) extending inside each support frame (22) and extending into the installation groove (82) is arranged inside 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 die (8). A second water pipe (75) is arranged in the installation groove (82) of the core die (8). 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-connect joint (76). A plurality of water guiding holes (79) arranged radially are arranged at intervals along the circumferential direction inside the inner die (53). The third water pipe (77) is communicated with the corresponding water guiding holes (79) through a plurality of fourth water pipes (78). A plurality of inner spray holes (74) communicated with the corresponding water guiding holes (79) are arranged on the right side of the inner die (53). The inner cavity of the diameter-expanding cover (57) is communicated with the inner spray holes (74).

2. The plastic pipe forming machine according to claim 1, wherein, The support frame (22) is arranged inside the support section (2). A flow dividing cone (81) is arranged at the left end of the core mold (8) inside the flow dividing section (1). The gap between the flow dividing cone (81) and the inner wall of the flow dividing section (1) forms a flow dividing cavity (11). The gap between the support frames (22) forms a through-flow hole (21). The gap between the core mold (8) and the rectifying section (3) forms a rectifying cavity (31). The gap between the core mold (8) and the extrusion section (4) forms an extrusion cavity (41). The outer diameter of the core mold (8) inside the extrusion cavity (41) gradually decreases from both sides to the middle.

3. A plastic pipe forming machine according to claim 2, wherein, 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 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).

4. A plastic pipe forming machine according to claim 1, characterized in that, The inner cavity of the diameter-expanding cover (57) is communicated with the inner spray holes (74) through an atomization cavity (579). The atomization cavity (579) is of a Venturi tube structure. The water guiding hole (79) is communicated with the throat of the atomization cavity (579).

5. A plastic pipe forming machine according to claim 4, characterized in that, The diameter-expanding cover (57) is sequentially connected with a first diameter-expanding section (571), a second diameter-expanding section (572), and a guiding section (576) from left to right. An inward-extending annular partition plate (575) is arranged between the second diameter-expanding section (572) and the guiding section (576). The annular partition plate (575) divides the inner cavity of the diameter-expanding cover (57) into a non-communicating first cavity (573) and a second cavity (577). A back pressure valve (578) is arranged on the annular partition plate (575). The first cavity (573) is communicated with the air intake hole (83). The second cavity (577) is communicated with the atomization cavity (579). A through hole (�74) communicating the first cavity (573) with the diameter-expanding cavity (58) is arranged on the second diameter-expanding section (572).

6. A plastic pipe forming machine according to claim 5, 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 arranged on the right side of the outer mold (52). A strip-shaped groove (56) communicating with the second spiral cooling cavity (55) is arranged inside the left part of the outer mold (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). The left side of the first spiral cooling cavity (42) is communicated with an annular air pipe (63) through a second air pipe (62).

7. A plastic pipe forming machine according to claim 6, characterized in that, The strip-shaped groove (56) is communicated with the upper wall of the diameter-expanding cavity (58) through an inclined groove (65).

8. A plastic pipe forming machine according to claim 7, characterized in that, Both the third air pipe (64) and the second water pipe (75) are made of heat-insulating materials.

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