Injection molding equipment and process for large-diameter polyethylene elbow

Abstract

The application discloses a kind of injection molding equipment and process of large-diameter polyethylene elbow.The equipment includes extruder, injection mold and mold driving system.Injection mold adopts coaxial 90-degree arc-shaped outer mold and inner mold assembly spliced by unit module to form closed forming cavity.Mold driving system is half-round guiding cage structure, and built-in power wheel driving mold is rotated in its interior according to half-round path.The extruder is connected with injection pipe of mold distribution cover, and polyethylene melt is continuously injected into forming cavity from bottom to top.The injection molding process is balanced feeding by multiple injection pipes, and forced cooling by spray pipe, to realize one-step injection molding of large-diameter polyethylene elbow.The equipment cooperates with corresponding assembly, injection molding, cooling, demolding and reassembly process steps, solves the forming problem of large-diameter PE elbow, and has the advantages of modularity, adjustability, high efficiency and good forming quality.

Description

Technical Field

[0001] This invention relates to the field of polyethylene elbow processing technology, specifically to an injection molding equipment and process for large-diameter polyethylene elbows. Background Technology

[0002] Compared to traditional pipe materials such as cast iron pipes, cement pipes, and glass pipes, polyethylene (PE) pipes have significant technical advantages, mainly manifested in good flexibility, strong corrosion resistance, bendability, excellent wear resistance, light weight, convenient installation, and long service life. Therefore, they are widely used in water supply and drainage, gas transmission, and chemical fluid processing. However, for large-diameter PE pipes, regardless of whether extrusion or polyethylene strip winding processes are used, the fabrication of matching elbows and fittings is quite difficult. Large-diameter elbows have complex structures and large dimensions, making it difficult to form them in a single process using existing technologies. Furthermore, the strength and sealing performance after forming often fail to simultaneously meet usage requirements, becoming a key bottleneck restricting the widespread application of large-diameter PE piping systems.

[0003] Replacing polyethylene elbows with steel fittings is not only expensive but also poses a corrosion risk. Furthermore, it negates the inherent advantages of polyethylene pipes, such as corrosion resistance and lightweight design, thus failing to fully utilize the comprehensive performance of the polyethylene piping system. Therefore, there is an urgent need to develop specialized injection molding equipment and processes suitable for large-diameter polyethylene elbows to achieve efficient and low-cost integrated molding of elbow fittings, thereby solving the technical problem of difficult matching of elbow fittings in large-diameter polyethylene piping systems. Summary of the Invention

[0004] The purpose of this invention is to provide an injection molding equipment and process for large-diameter polyethylene elbows. The equipment can drive the injection mold to rotate through a mold drive system and fill the injection mold with molten polyethylene material to achieve the one-piece molding of large-diameter polyethylene elbows, thus solving the problems in the prior art.

[0005] The technical solution adopted by this invention to solve its technical problem is: injection molding equipment for large-diameter polyethylene elbows, including an extruder, an injection mold, and a mold drive system. The extruder can inject polyethylene hot melt material into the injection mold, and the mold drive system can drive the injection mold to move. The injection mold includes an outer mold assembly and an inner mold assembly arranged coaxially. Both the outer mold assembly and the inner mold assembly are arc-shaped molds with an axial bend of 90 degrees. A forming cavity is opened between the outer mold assembly and the inner mold assembly. An end cap is installed at one end of the outer mold assembly and the inner mold assembly in the length direction. The extruder has a flow divider cover at the other end of the outer mold assembly and the inner mold assembly along their length. The discharge port of the extruder is connected to the inlet of the flow divider cover. Several interconnected injection pipes are installed on the flow divider cover, and each injection pipe extends into the molding cavity near the end of the end cover. The outer mold assembly is composed of several axial unit outer molds, and each unit outer mold includes two sets of detachable semi-circular sleeves. The inner mold assembly is also composed of several axial unit inner molds. A detachable mandrel is fitted at the axial center of each unit inner mold, and the end cover has a corresponding opening for the mandrel. The mold has a through-hole, and each unit's inner mold includes an upper component, a lower component, a left component, and a right component. Two sets of semi-circular sleeves corresponding to the unit's outer mold are assembled to form the outer peripheral wall of the molding cavity, and the upper, lower, left, and right components corresponding to the unit's inner mold are assembled to form the inner peripheral wall of the molding cavity. The mold driving system includes a guide cage that cooperates with the injection mold. The guide cage is a semi-circular frame structure that rotates 180 degrees axially. A horizontally arranged support fixing plate is provided in the middle of the guide cage, and a sliding door that can be opened and closed is provided on the support fixing plate. The injection mold can enter the lower half of the guide cage. Several drive wheels are installed inside the guide cage, each capable of radial extension and retraction along the cross-section of the guide cage. These drive wheels can move to contact the injection mold. Activation of the drive wheels drives the outer mold assembly, inner mold assembly, end cap, and mandrel within the mold drive system. A flip-top cover, which can be opened and closed, is installed on the upper half of the guide cage above the support plate, corresponding to the bottom end of the injection pipe extending into the molding cavity. Several spray pipes are also installed circumferentially around the inner circumference of the guide cage. The end cap is fixedly installed at one end of the outer mold assembly and inner mold assembly along their length. Flanges are provided on the outer edges of both ends of each unit's outer mold along the axial direction. Connecting bolts are provided on the flanges of adjacent unit outer molds. Two sets of semi-circular sleeves of the unit's outer mold have connecting hinges on one side and buckles on the other side. The flow divider cover has a molten material injection hole at its axial center, which is connected to the extruder's outlet. Several flow divider pipes, each connected to the molten material injection hole, are arranged circumferentially on the flow divider cover. Each flow divider pipe is connected to an injection pipe. A radial track, matching the injection pipe, is also provided on the flow divider cover around the flow divider pipes. The cross-sectional diameter of the mandrel gradually decreases, with the diameter at the end near the end cap being larger than the diameter at the end near the flow divider cover. The upper, lower, left, and right components each include an inner mold core seat and an inner mold outer edge, with a support between the inner mold core seat and the inner mold outer edge.The mandrel is equipped with connecting rails corresponding to the four sets of components. A concave channel that mates with the connecting rails is formed on the inner circumference of the inner mold core seat. When the inner mold core seats of the upper, lower, left, and right components are fitted onto the mandrel, the outer edges of the inner molds are joined to form a complete circumference. An upper support is installed on the upper half of the guide cage, and a lower support is installed on the lower half. Two openable and closable flaps are also installed on the upper half of the guide cage above the bracket fixing plate. Each flap is connected to the guide cage via ball joints, and the two flaps are connected by snap fasteners. The opening and closing positions of the drive wheel and the flaps are staggered. A wheel seat bracket is installed on the power wheel, and a drive motor is provided on one side of the wheel seat bracket. The output shaft of the drive motor is connected to the wheel axle of the power wheel. Corresponding to the position of the wheel seat bracket, a screw hole is opened on the guide cage, and a screw is installed in the screw hole. A rocker handle is provided at the end of the screw that extends out of the guide cage, and the end of the screw that extends into the guide cage is installed on the wheel seat bracket through a bearing. Rotating the rocker handle can adjust the distance between the power wheel and the injection mold. The injection molding process for large-diameter polyethylene elbows includes the following steps: ① Pull the injection tube outward along the radial track on the manifold to the outer edge of the manifold, close the sliding door on the bracket fixing plate, insert the end cap, install the mandrel onto the through hole of the end cap, and slide down the concave channels on the upper, lower, left, and right parts of each unit's inner mold according to the installation sequence of the unit inner mold, aligning them with the connecting rails on the mandrel to complete the installation of the inner mold; ② After the inner mold is installed in step ①, move the injection tube inward along the radial track to the molding cavity position, and connect the injection tube to the manifold on the manifold. Then open the flip cover and install all the unit outer molds on the end cap in sequence; ③ After the outer mold is installed in step ②, close and lock the flip cover, adjust the power wheel on the mold drive system to move it into contact with the outer mold, support the injection mold in the guide cage, and then open the sliding door on the bracket fixing plate to provide a channel for the injection mold to move downward; ④ After the injection mold is installed and supported in step ③ After extrusion, the extruder extrudes the polyethylene hot melt material, which enters the bottom of the molding cavity through the injection pipe. Simultaneously, the spray pipe cools the material as it enters the molding cavity. As the molten material is injected, the injection mold slowly descends in a semi-circular direction under the drive of the power wheel. The injection pipe continuously injects the polyethylene hot melt material vertically into the molding cavity, while the spray pipe cools the material around its perimeter at the corresponding positions, until the injection mold moves to the bottom of the lower quarter circle of the mold drive system. The injection mold is then completely filled with polyethylene molten material and cools to form the elbow. ⑤ After the polyethylene elbow pipe in step ④ is processed, the injection pipe is moved outward along the radial track on the manifold cover, and the high-pressure air chamber is connected. High-pressure air is injected into the injection pipe to remove any accumulated polyethylene molten material. At this point, the position of the injection pipe within the guide cage will not affect the movement of the injection mold. ⑥ The mandrel at the lower end of the mold drive system is hooked and fixed. The power wheel rotates in the opposite direction, driving the injection mold upward along the guide cage, while the mandrel disengages.Until the injection mold moves to the upper quarter circle position of the guide cage, the mandrel is completely disengaged; ⑦ After the mandrel is completely disengaged from the injection mold in step ⑥, remove the end cap from the inner and outer molds, and slide it down the mandrel to the lower end of the guide cage, then reassemble it with the bottom end of the mandrel; ⑧ After the end cap is disassembled and slid into place in step ⑦, slide the upper and lower parts of the first unit inner mold closest to the end cap radially towards the center to demold and remove them, align the concave channel on them with the connecting rail on the mandrel, slide them down to the position of the end cap, and then... The left and right components of this unit's inner mold are moved towards the center for demolding and removal. They are then slid down along the mandrel's connecting rail and installed onto the end cap, completing the demolding and reassembly of the bottom unit's inner mold. The above steps are repeated for the demolding and reassembly of subsequent unit inner molds until all inner molds are demolded and reassembled. At this point, both the inner mold and mandrel are positioned at the lower quarter circle of the guide cage. After the inner mold demolding and reassembly in step ⑧ are completed, the sliding door is closed, the flip cover is opened, and the position of the power wheel is adjusted to avoid interference during outer mold disassembly. The upper part of the guide cage is then... The outer molds of each unit within the quarter circle are disassembled segment by segment until they are completely removed; ⑩ After all the outer molds in step ⑨ have been removed, the injection-molded and demolded polyethylene elbow product is lifted out from the opened flap position and inspected before being stored. The injection pipe in the guide cage will not affect the lifting out of the finished pipe. Then the flap is closed; ⑪ After the finished polyethylene elbow from step ⑩ has been taken out, the power wheel in the lower quarter circle of the guide cage is adjusted to press it against the inner mold. The sliding door is opened, and the power wheel is turned on to drive the reassembled inner mold, mandrel, and end cap upwards. Once the guide cage reaches the upper quarter circle position, close the sliding door; ⑫ After the inner mold, mandrel, and end cap from step ⑪ have moved to the upper quarter circle position of the guide cage, move the injection pipe inward along the radial track to reset it, extending it to the bottom of the molding cavity and connecting it to the distribution pipe on the distribution cover. Open the flip cover, install the unit outer mold in sequence, and fix the end cap to the outer mold and inner mold. Adjust the position of the power wheel to press it firmly onto the outer mold. Finally, open the sliding door, close the flip cover, and prepare to begin the next injection molding process for a polyethylene elbow.

[0006] The positive effects of this invention are as follows: The injection molding equipment and process for large-diameter polyethylene elbows described in this invention use an extruder in conjunction with an injection mold, and a guide cage mold drive system drives the mold to rotate slowly along a semi-circular path, realizing continuous filling molding of polyethylene molten material from the bottom, with simultaneous injection, movement and cooling. This fundamentally solves the technical bottleneck of the difficulty in one-time molding of large-diameter polyethylene elbows, avoids the problems of high cost and loss of corrosion resistance caused by alternative pipe fitting solutions, and fully retains the comprehensive advantages of polyethylene pipes such as corrosion resistance, lightweight, and good flexibility.

[0007] The injection mold employs a coaxially arranged outer mold assembly and inner mold assembly, both of which are arc-shaped molds with a 90-degree axial bend. Together with end caps and manifold caps, they form a relatively closed molding cavity, enabling one-time injection molding of large-diameter polyethylene 90-degree elbows. This solves the problem of difficult manufacturing of large-diameter PE elbows, and the overall strength and sealing performance are superior to split-part components. Both the outer and inner mold assemblies adopt a modular assembly structure. The unit outer mold is connected by two sets of semi-circular sleeves, and the unit inner mold is assembled from four parts (upper, lower, left, and right) with detachable mandrels. Selecting different types of unit molds allows for flexible adaptation to the production needs of elbows with different diameters, significantly reducing mold manufacturing costs. The manifold cap is equipped with melt injection holes and several manifold tubes. Each injection tube extends into the molding cavity to achieve multi-point balanced feeding, effectively avoiding weld lines and uneven filling during the injection molding process of large-diameter elbows, ensuring product quality.

[0008] The power wheel in the mold drive system can be adjusted radially along the cross-section to adapt to molds of different diameters. The opening and closing design of the flip-top and sliding door makes mold loading and unloading operations convenient and efficient. The synchronous cooling of the spray pipe effectively ensures product quality. In terms of process, non-destructive demolding is achieved by the injection pipe moving on the radial track of the manifold. High-pressure air removes residual molten material, and the segmented inner mold demolding and reassembly process allows the entire process to be quickly cyclical, greatly improving production efficiency. This equipment and process realizes efficient and low-cost integrated injection molding production of large-diameter polyethylene elbows, and has significant practical and promotional value. Attached Figure Description

[0009] Figure 1 This is a three-dimensional structural schematic diagram of the injection molding equipment of the present invention; Figure 2 This is a front view of the injection molding equipment of the present invention; Figure 3 yes Figure 2 Top view; Figure 4 yes Figure 2 The left view; Figure 5 This is a schematic diagram of the injection mold structure; Figure 6 It is a half-section view of the injection mold; Figure 7 This is a schematic diagram of the end cap structure; Figure 8 This is a schematic diagram of the diversion cover structure; Figure 9 This is a schematic diagram of the unit's external mold structure; Figure 10 This is a schematic diagram of the internal structure of the unit mold; Figure 11 This is a schematic diagram of the mandrel structure; Figure 12 This is a cross-sectional view of the unit's internal mold fitting on the mandrel; Figure 13 This is a schematic diagram of the mold drive system; Figure 14 This is a schematic diagram showing the power wheel positioned on the inner circumference of the mold drive system; Figure 15 This is a simplified schematic diagram showing the finished elbow formed after step ⑤ of the process in this invention. Figure 16This is a simplified schematic diagram showing the mandrel being removed after step ⑥ of the process in this invention. Figure 17 This is a simplified schematic diagram showing the reassembly of the end cap and inner mold onto the mandrel after step ⑧ in the process of this invention. Figure 18 This is a simplified schematic diagram illustrating the demolding of the outer mold and the removal of the finished product after step ⑩ in the process of this invention. Figure 19 This is a simplified schematic diagram of the inner mold, mandrel, and end cap reassembled after step ⑪ in the process of this invention, which moves upward to the upper guide cage of the support fixing plate. Detailed Implementation

[0010] The present invention relates to an injection molding equipment for large-diameter polyethylene elbows, such as... Figure 1-4 As shown, it includes an extruder 24, an injection mold, and a mold drive system. The extruder 24 can inject polyethylene hot melt material into the injection mold, and the mold drive system can drive the injection mold to move. Through the relative movement of the injection mold, the internal molten material is filled layer by layer, thereby completing the production of the polyethylene elbow.

[0011] like Figure 5-12 As shown, the injection mold includes an outer mold assembly and an inner mold assembly arranged coaxially. Both the outer mold assembly and the inner mold assembly are arc-shaped molds with an axial bend of 90 degrees. A molding cavity 1 is formed between the outer mold assembly and the inner mold assembly. By injecting molten polyethylene into the molding cavity 1 and cooling it, a 90-degree polyethylene elbow can be obtained. An end cap 2 is installed at one end of the outer mold assembly and the inner mold assembly along their length, and a flow divider 3 is provided at the other end of the outer mold assembly and the inner mold assembly along their length. The end cap 2 is used to fix the outer mold assembly and the inner mold assembly, so that the molding cavity 1 is formed between the outer mold assembly and the inner mold assembly in a set state. The flow divider 3 can realize the uniform injection operation in the molding cavity 1 to ensure the processing quality of the polyethylene elbow.

[0012] The discharge port of the extruder 24 is connected to the inlet of the diversion cover 3. Several interconnected injection pipes 4 are installed on the diversion cover 3. The injection pipes 4 are arranged circumferentially on the diversion cover 3. Each injection pipe 4 extends into the molding cavity 1 near the end cover 2. The injection pipe 4 is an arc-shaped pipe with an axial bend of 90 degrees to fit the molding cavity 1. The discharge port of the injection pipe 4 is located at the bottom of the bent mold. Polyethylene hot melt material is injected from the bottom. The end cover 2 at the bottom of the injection mold is arranged horizontally. In this way, the discharge port of the injection pipe 4 is in a vertical position to facilitate the fall of the polyethylene hot melt material.

[0013] To facilitate the demolding of the finished polyethylene elbow, the outer mold assembly is composed of several axial unit outer molds spliced ​​together. Each unit outer mold includes two sets of detachable semi-circular sleeves 5. The inner mold assembly is also composed of several axial unit inner molds spliced ​​together. A detachable mandrel 6 is provided at the axial center of each unit inner mold. The end cap 2 has a through hole 18 that mates with the mandrel 6. Each unit inner mold includes an upper component 7, a lower component 8, a left component 9, and a right component 10. The four components are assembled on the mandrel 6 to support the inner mold assembly.

[0014] The two sets of semi-circular sleeves 5 corresponding to the outer mold of the unit are assembled as the outer peripheral wall of the molding cavity 1, and the upper part 7, lower part 8, left part 9 and right part 10 corresponding to the inner mold of the unit are assembled as the inner peripheral wall of the molding cavity 1.

[0015] To achieve rotational drive of the injection mold, the positions of the manifold 3 and the injection pipe 4 remain relatively stationary, ensuring that the outlet of the injection pipe 4 is always vertical. This improves the processing quality and efficiency of the polyethylene elbow. Figure 13 As shown, the mold drive system includes a guide cage 25 that cooperates with the injection mold. The guide cage 25 is a semi-circular frame structure that rotates 180 degrees axially, which can provide necessary support and guidance for the movement of the internal injection mold.

[0016] A horizontally arranged support plate 26 is located in the middle of the guide cage 25. The support plate 26 has an opening and closing sliding door 27. When the sliding door 27 is open, the injection mold can enter the lower half of the guide cage 25; when closed, the sliding door 27 can be used as an operating table. Several drive wheels 28 are also provided inside the guide cage 25. Each drive wheel 28 can be adjusted radially along the cross-section of the guide cage 25 to accommodate molds of different diameters. The drive wheels 28 can move to contact the injection mold. Activating the drive wheels 28 drives the outer mold assembly, inner mold assembly, end cap 2, and mandrel 6 within the injection mold drive system. A motor can be installed on the drive wheels 28 as a power mechanism, rotating automatically to move the internal injection mold.

[0017] A horizontally arranged support plate 26 is provided at the middle position of the guide cage 25. The support plate 26 divides the guide cage 25 into an upper quarter circle and a lower quarter circle. The support plate 26 can be placed on the ground to ensure the firmness and stability of the entire mold drive system. After the injection mold moves from the upper quarter circle position to the lower quarter circle position, the position of the injection pipe 4 inside remains relatively unchanged, which can maintain a vertical feeding state to fill the molding cavity 1 in the injection mold with polyethylene molten material.

[0018] To facilitate the removal of the finished polyethylene elbow from the inside, a hinged flap 29 is installed on the upper half of the guide cage 25 on the upper side of the support fixing plate 26. During the movement of the injection mold, to achieve cooling and molding at the injection position, several circumferentially arranged spray pipes 30 are installed on the inner circumference of the guide cage 25 corresponding to the bottom end of the injection pipe 4 extending into the molding cavity 1. The drive wheel 28 is positioned to avoid the opening and closing position of the flap 29, so as to drive the injection mold without affecting the normal opening of the flap 29.

[0019] During the casting process of the polyethylene elbow, the outer mold assembly at the bottom of the mold is simultaneously sprayed with spray pipe 30 for forced cooling. The entire injection mold rotates 90 degrees axially under the drive of the mold drive system. The positions of the flow divider 3 and the injection pipe 4 remain relatively fixed, and the outlet of the injection pipe 4 is always kept in a vertical position. This is conducive to the horizontal and uniform distribution of the injected polyethylene hot melt material under the action of gravity, thereby improving the processing quality and efficiency of the polyethylene elbow.

[0020] When using the injection molding equipment for large-diameter polyethylene elbows described in this invention, to avoid uneven solidification and voids during cooling of the entire mold during injection molding, a semi-circular long elbow heat-insulating pipe, namely injection pipe 4, is used at the discharge port of extruder 24. This pipe extends from the discharge port of extruder 24 all the way to the bottom of the elbow mold, injecting hot-melt polyethylene material from the bottom. Simultaneously, spraying is applied to the outer periphery of the outer mold bottom using spray pipe 30 for forced cooling. A semi-circular mold drive system is installed outside the injection mold, driving the internal injection mold to slowly descend in a semi-circular direction. The injection pipe 4 continuously injects hot-melt polyethylene material and cools the surrounding area until the elbow mold is completely filled and cooled into the finished elbow. Then, the injection pipe 4 is moved away along the radial track 17 on the manifold cover 3, and high-pressure air is used to force the molten material out of the injection pipe to prevent condensation and blockage. The mold drive system drives the injection mold to move upwards from the bottom to return to its original position, simultaneously pulling out the mandrel 6 in the middle of the inner mold, demolding and reinstalling the inner mold, and then demolding and removing the outer mold section by section. Open the flip cover 29 to lift out the finished polyethylene elbow. Then, reassemble the inner mold, injection pipe, and outer mold to prepare for the production of the next polyethylene elbow.

[0021] The coaxially arranged 90-degree arc-shaped outer mold assembly, together with the inner mold assembly and end caps 2 and flow divider caps 3, forms a relatively closed molding cavity 1, which can injection mold large-diameter polyethylene 90-degree elbows in one step, fundamentally solving the problem of difficult manufacturing of large-diameter polyethylene elbows. Both the outer mold assembly and the inner mold assembly adopt a modular splicing structure. The outer mold is assembled from a semi-circular sleeve 5, and the inner mold is assembled from four parts (upper, lower, left, and right) with a detachable mandrel 6, which can flexibly adapt to different diameter specifications, greatly reducing mold manufacturing costs and maintenance difficulty.

[0022] Furthermore, the end cap 2 is fixedly installed at one end of the outer mold assembly and the inner mold assembly along their length, providing a basic positioning for the installation of the outer mold assembly and the inner mold assembly. To facilitate the connection between the various unit outer molds and the assembly connection of the two sets of semi-circular sleeves 5 on the same unit outer mold, flanges 11 are provided on the outer edges of both ends of each unit outer mold along the axial direction. Connecting bolts 12 are provided on the flanges 11 of adjacent unit outer molds. A hinge 13 is provided on one side of each set of semi-circular sleeves 5 of the unit outer mold, and a buckle 14 is provided on the other side. The flanges 11, hinges 13, and buckles 14 are all designed to avoid contact with the drive wheels 28; that is, the circumferentially arranged flanges 11 can have clearance grooves that mate with each drive wheel 28.

[0023] The outer molds of adjacent units are fastened together by flanges 11 and connecting bolts 12, ensuring axial sealing and structural strength after splicing and preventing molten material leakage during injection molding. The semi-circular sleeve 5 adopts an opening and closing method with hinges 13 and buckles 14, making mold loading and unloading operations convenient and efficient, significantly improving production efficiency.

[0024] Furthermore, in order to ensure that the polyethylene melt can be evenly injected into each distribution pipe 16 during the injection operation, a melt injection hole 15 is provided at the axial position of the distribution cover 3. The melt injection hole 15 is connected to the discharge port of the extruder 24. Several distribution pipes 16 connected to the melt injection hole 15 are arranged circumferentially on the distribution cover 3. Each distribution pipe 16 is connected to the injection pipe 4, so that the melt is evenly distributed to each injection pipe 4, realizing multi-point balanced feeding in the molding cavity 1 and ensuring consistent filling in all parts of the large-diameter elbow.

[0025] To prevent interference with the injection pipe 4 when removing the finished polyethylene elbow during demolding, a radial track 17 is provided on the distribution cover 3 around the distribution pipe 16 to cooperate with the injection pipe 4. After injection molding is completed, the injection pipe 4 can slide along the radial track 17 to the outer side of the distribution cover 3, leaving space for subsequent finished product hoisting and demolding operations, so as to facilitate subsequent demolding operations and avoid interference with the mold or the finished polyethylene elbow.

[0026] Furthermore, to facilitate the disassembly of the mandrel 6, the cross-sectional diameter of the mandrel 6 gradually decreases, with the diameter at the end near the end cap 2 being larger than the diameter at the end near the distributor cap 3. The aforementioned mandrel 6 adopts a conical, gradually decreasing diameter structure, providing a draft angle for demolding, allowing the internal mandrel 6 to be easily removed after injection molding. The through hole 18 on the end cap 2 not only provides the necessary space for the removal of the mandrel 6 but also provides precise installation positioning for the mandrel 6, ensuring coaxiality.

[0027] Furthermore, to facilitate the positioning and assembly of each component of the unit mold on the mandrel 6, the upper component 7, lower component 8, left component 9, and right component 10 each include an inner mold core seat 19 and an inner mold outer edge 20. A bracket 21 is provided between the inner mold core seat 19 and the inner mold outer edge 20. A connecting rail 22 corresponding to the four sets of components is provided on the mandrel 6. A concave channel 23 that mates with the connecting rail 22 is opened on the inner circumferential surface of the inner mold core seat 19. When the inner mold core seats 19 of the upper component 7, lower component 8, left component 9, and right component 10 are fitted onto the mandrel 6, the inner mold outer edges 20 are spliced ​​to form a complete circumference, constituting the inner circumferential wall of the mold.

[0028] The four components of the aforementioned unit inner mold are precisely positioned by the connecting rail 22 on the mandrel 6 and the concave channel 23 of the inner mold core seat 19, ensuring the roundness and coaxiality of the inner circumference wall after assembly. The bracket 21 connects the inner mold core seat 19 and the outer edge 20 of the inner mold, enhancing the structural strength of the inner mold. This split-type inner mold structure facilitates assembly, disassembly, and maintenance, further reducing usage and maintenance costs.

[0029] Both the outer mold assembly and the inner mold assembly can be divided into five interconnected sections. The injection pipe 4 acts as an insulation pipe to prevent the polyethylene molten material from losing temperature during injection molding. It extends directly from the molding cavity 1 between the outer mold assembly and the inner mold assembly to the end cap 2 near the bottom, and the internal polyethylene molten material is filled by the rotation of the injection mold. The radial track 17 allows the injection pipe 4 to move outward relative to the diversion cover 3, leaving space for subsequent finished product hoisting and demolding operations. At the same time, the removed injection pipe 4 can be connected to a high-pressure or high-temperature gas chamber. After injection molding, the molten material in the injection pipe 4 is discharged to prevent condensation and blockage during the next use.

[0030] Furthermore, in order to improve the stability of the vertical arrangement of the mold drive system, an upper support 31 is installed on the upper half of the guide cage 25 and a lower support 32 is installed on the lower half of the guide cage 25. The upper support 31 and the lower support 32 can provide effective support for both ends of the guide cage 25, and together with the bracket fixing plate 26, they can provide more stable support for the entire device.

[0031] Furthermore, in order to facilitate the disassembly and assembly of the internal injection mold or the hoisting of the molded polyethylene elbow, the upper half of the guide cage 25 on the upper side of the bracket fixing plate 26 is also equipped with two openable and closable flaps 29. Each flap 29 is connected to the guide cage 25 by ball joint 33, and the two flaps 29 are connected by buckle 34. The opening and closing positions of the power wheel 28 and the flaps 29 are staggered.

[0032] Furthermore, to facilitate adaptation to injection molds of different diameters, and to ensure that the drive wheel 28 can always press against and contact the outer circumferential surface of the mold for driving, such as... Figure 14As shown, a wheel seat bracket 35 is installed on the power wheel 28, and a drive motor 36 is provided on one side of the wheel seat bracket 35. The output shaft of the drive motor 36 is connected to the wheel axle of the power wheel 28. When the drive motor 36 is started, it can drive the power wheel 28 to rotate, thereby driving the injection mold to move in the guide cage 25.

[0033] To achieve radial position adjustment of the drive wheel 28, a screw hole is provided on the guide cage 25 corresponding to the position of the wheel seat bracket 35. A screw 37 is installed in the screw hole. A crank handle 38 is provided at the end of the screw 37 extending out of the guide cage 25. The end of the screw 37 extending into the guide cage 25 is mounted on the wheel seat bracket 35 through a bearing. Rotating the crank handle 38 can adjust the distance between the drive wheel 28 and the injection mold, ensuring that the drive wheel 28 can be pressed against the outer periphery of the mold. The bearing facilitates the adjustment of the position of the drive wheel 28, ensuring that its rotation direction is consistent with the movement direction of the injection mold, thereby achieving the corresponding function of driving the injection mold to move.

[0034] The injection molding process for large-diameter polyethylene elbows includes the following steps: ① Pull the injection pipe 4 outward along the radial track 17 on the diversion cover 3 to the outer edge of the diversion cover 3, close the sliding door 27 on the bracket fixing plate 26, insert the end cover 2, install the mandrel 6 onto the through hole 18 of the end cover 2, and, according to the installation sequence of the unit inner mold, align the concave channels 23 on the upper part 7, lower part 8, left part 9 and right part 10 of each unit inner mold with the connecting rail 22 on the mandrel 6 and slide them down to complete the installation of the inner mold; ②After the inner mold is installed in step ①, move the injection pipe 4 inward along the radial track 17 into the molding cavity 1, and connect the injection pipe 4 to the diversion pipe 16 on the diversion cover 3. Then open the flip cover 29 and install all the unit outer molds on the end cover 2 in sequence. ③ After the outer mold is installed in step ②, close and lock the flip cover 29, adjust the power wheel 28 on the mold drive system to move it into contact with the outer mold, support the injection mold in the guide cage 25, and then open the sliding door 27 on the bracket fixing plate 26 to provide a channel for the injection mold to move down. ④ After the injection mold is installed and supported in step ③, the extruder 24 extrudes the polyethylene hot melt material, which enters the bottom of the molding cavity 1 through the injection pipe 4. At the same time as the molten material enters the molding cavity 1, the spray pipe 30 cools it down. As the molten material is injected, the injection mold slowly moves down in a semi-circular direction under the drive of the power wheel 28. The injection pipe 4 continuously injects the polyethylene hot melt material into the molding cavity 1 in the vertical direction. At the same time, the spray pipe 30 cools it down around the corresponding position until the injection mold moves to the bottom position of the lower quarter circle of the mold drive system. The injection mold is completely filled with polyethylene molten material and cools to form the elbow finished product. ⑤ After the polyethylene elbow pipe in step ④ is processed, the injection pipe 4 is moved outward along the radial track 17 on the diversion cover 3, and the high-pressure air chamber is connected. High-pressure air is injected into the injection pipe 4 to remove the polyethylene melt accumulated inside. At this time, the position of the injection pipe 4 in the guide cage 25 will not affect the movement of the injection mold. ⑥ Hook and fix the mandrel 6 at the lower end of the mold drive system with a hook. The power wheel 28 rotates in the opposite direction, driving the injection mold to rotate upward along the guide cage 25. At the same time, the mandrel 6 is dislodged until the injection mold moves to the upper quarter circle position of the guide cage 25, and the mandrel 6 is completely dislodged. ⑦ After the mandrel 6 is completely removed from the injection mold in step ⑥, remove the end cap 2 from the inner mold and outer mold, and let it slide down along the mandrel 6 to the lower end of the guide cage 25, and reassemble it with the bottom end of the mandrel 6. ⑧ After the end cover 2 is disassembled and slid into place in step ⑦, slide the upper part 7 and lower part 8 of the first unit inner mold closest to the end cover 2 radially toward the center to demold and remove them. Align the concave channel 23 on them with the connecting rail 22 on the mandrel 6 and slide them down to the position of the end cover 2. Then move the left part 9 and right part 10 of this unit inner mold toward the middle, demold and remove them. Similarly, slide them down along the connecting rail 22 of the mandrel 6 to the position of the end cover 2. This completes the demolding and reinstallation of the bottom unit inner mold. Repeat the above steps to demold and reinstall the inner molds of the subsequent units until all inner molds are demolded and reinstalled. At this time, the inner mold and the mandrel 6 are both in the lower quarter circle position of the guide cage 25. ⑨ After the inner mold is demolded and reassembled in step ⑧, close the sliding door 27, open the flip cover 29, adjust the position of the power wheel 28 to avoid interference during the disassembly of the outer mold, and disassemble each unit of the outer mold in the upper quarter circle of the guide cage 25 section by section until it is completely removed. ⑩ After all the outer molds in step ⑨ have been removed, the injection-molded and demolded polyethylene elbow products are lifted out at the open flap 29 position and inspected and stored. The injection pipe 4 in the guide cage 25 will not affect the lifting out of the finished pipe. Then the flap 29 is closed. ⑪ After the polyethylene elbow finished product in step ⑩ is taken out, adjust the power wheel 28 in the lower quarter circle of the guide cage 25 to press it against the inner mold, open the sliding door 27, turn on the power wheel 28 to drive the reinstalled inner mold, mandrel 6 and end cover 2 upward to the position of the upper quarter circle of the guide cage 25, and close the sliding door 27. ⑫ After the inner mold, mandrel 6 and end cap 2 are moved to the position of the upper quarter circle of the guide cage 25 in step ⑪, the injection pipe 4 is moved inward along the radial track 17 to reset, extending into the bottom position of the molding cavity 1 and connecting with the diversion pipe 16 on the diversion cover 3. The flip cover 29 is opened, the unit outer mold is installed in sequence, and the end cap 2 is fixedly connected to the outer mold and the inner mold. The position of the power wheel 28 is adjusted to press it against the outer mold. Finally, the sliding door 27 is opened, the flip cover 29 is closed, and the next injection molding polyethylene elbow processing process is prepared to begin.

[0035] The mold drive system needs to support the entire equipment, so it must be robust enough, but its structure is not complex. The guide cage 25 can be constructed using angle iron or steel pipes, and is mostly hollow in the middle, so it does not affect many operations, such as the assembly and disassembly of the outer mold. The flip-top 29 design on the upper part of the guide cage 25 allows the bent tube product to be lifted out without affecting the stability of the mold drive system. An operating room can be set at the lower end of the mold drive system for convenient operations such as the reassembly of the inner mold. The drive motors 36 of each power wheel 28 can be centrally controlled from the control room, facilitating the accurate operation of the injection mold during injection and demolding reassembly.

[0036] During the manufacturing process of polyethylene elbows, a wire mesh skeleton can be added to the forming cavity 1 between the outer mold and the inner mold, but it must be avoided from the injection pipe 4 to prevent interference between the two. After pouring in the polyethylene hot melt material, the wire mesh is wrapped in it to form a polyethylene elbow with a skeleton, which can increase the pressure resistance and ring stiffness of the elbow.

[0037] In summary, this invention achieves highly efficient integrated injection molding of large-diameter polyethylene elbows through the organic combination of a mold drive system and modular injection molds, fundamentally breaking through the technical bottlenecks of traditional processes. The equipment features a reasonable structure, convenient operation, and strong adaptability, flexibly meeting the production needs of elbows of various specifications, and significantly reducing mold manufacturing costs and maintenance difficulties. The overall process is compact and highly efficient, combining excellent product quality with good economic benefits. It provides reliable equipment support and technical assurance for the promotion and application of large-diameter polyethylene pipeline systems, possessing broad market prospects and significant social promotion value.

[0038] The technical solutions of this invention are not limited to the embodiments described herein. All technical contents not described in detail herein are well-known technologies.

Claims

1. An injection molding equipment for large-diameter polyethylene elbows, characterized in that: The system includes an extruder (24), an injection mold, and a mold drive system. The extruder (24) injects polyethylene hot melt material into the injection mold, and the mold drive system moves the injection mold. The injection mold includes an outer mold assembly and an inner mold assembly arranged coaxially. Both the outer mold assembly and the inner mold assembly are arc-shaped molds with an axial bend of 90 degrees. A molding cavity (1) is provided between the outer mold assembly and the inner mold assembly. An end cap (2) is installed at one end of the outer mold assembly and the inner mold assembly in the length direction, and a flow divider cap (3) is provided at the other end of the outer mold assembly and the inner mold assembly in the length direction. The discharge port of the extruder (24) is connected to the inlet of the flow divider cap (3). Several interconnected injection pipes (4) are installed on the flow divider cap (3), and each injection pipe (4) extends into the molding cavity. 1) The inner end near the end cap (2) is where the outer mold assembly is made up of several axial unit outer molds spliced ​​together. Each unit outer mold includes two sets of detachable semi-circular sleeves (5). The inner mold assembly is also made up of several axial unit inner molds spliced ​​together. A detachable mandrel (6) is provided at the axial center of all unit inner molds. The end cap (2) is provided with a through hole (18) that matches the mandrel (6). Each unit inner mold includes an upper part (7), a lower part (8), a left part (9), and a right part (10). The two sets of semi-circular sleeves (5) corresponding to the unit outer mold are assembled as the outer peripheral wall of the molding cavity (1). The upper part (7), lower part (8), left part (9), and right part (10) corresponding to the unit inner mold are assembled as the inner peripheral wall of the molding cavity (1). The mold driving system includes a guide cage (25) that cooperates with the injection mold. The guide cage (25) is a semi-circular frame structure that rotates 180 degrees axially. A horizontally arranged support plate (26) is provided in the middle of the guide cage (25). A sliding door (27) that can be opened and closed is provided on the support plate (26). When the sliding door (27) is opened, the injection mold can enter the lower half of the guide cage (25). Several drive wheels (28) are also provided inside the guide cage (25). Each drive wheel (28) can move along the guide cage (25). The radial extension and retraction of the cross section can be adjusted. The power wheel (28) can move to contact the injection mold. When the power wheel (28) is started, it can drive the outer mold assembly, inner mold assembly, end cap (2) and mandrel (6) in the injection mold to move in the mold drive system. A flip cover (29) that can be opened and closed is also installed on the upper half of the guide cage (25) on the upper side of the bracket fixing plate (26), corresponding to the bottom end position of the injection pipe (4) extending into the molding cavity (1). Several spray pipes (30) arranged in a circle are also installed on the inner circumference of the guide cage (25).

2. The injection molding equipment for large-diameter polyethylene elbows according to claim 1, characterized in that: The end cap (2) is fixedly installed at one end of the outer mold assembly and the inner mold assembly in the length direction. The outer edges of both ends of the outer mold of each unit are provided with flanges (11). The flanges (11) of adjacent unit outer molds are provided with connecting bolts (12). The two sets of semi-circular sleeves (5) of the unit outer mold are provided with hinges (13) on one side and buckles (14) on the other side.

3. The injection molding equipment for large-diameter polyethylene elbows according to claim 1, characterized in that: The axial position of the diversion cover (3) is provided with a melt injection hole (15), which is connected to the discharge port of the extruder (24). Several diversion pipes (16) connected to the melt injection hole (15) are arranged on the circumference of the diversion cover (3). Each diversion pipe (16) is connected to the injection pipe (4). A radial track (17) that cooperates with the injection pipe (4) is also provided on the diversion cover (3) on the outer periphery of the diversion pipe (16).

4. The injection molding equipment for large-diameter polyethylene elbows according to claim 1, characterized in that: The cross-sectional diameter of the mandrel (6) gradually decreases, and the diameter of the end of the mandrel (6) near the end cap (2) is greater than the diameter of the end near the diverter cap (3).

5. The injection molding equipment for large-diameter polyethylene elbows according to claim 1, characterized in that: The upper component (7), lower component (8), left component (9) and right component (10) each include an inner mold core seat (19) and an inner mold outer edge (20). A bracket (21) is provided between the inner mold core seat (19) and the inner mold outer edge (20). A connecting rail (22) corresponding to the four components is provided on the mandrel (6). A concave channel (23) that matches the connecting rail (22) is opened on the inner circumferential surface of the inner mold core seat (19). When the inner mold core seats (19) of the upper component (7), lower component (8), left component (9) and right component (10) are installed on the mandrel (6), the inner mold outer edge (20) is spliced ​​to form a complete circumference.

6. The injection molding equipment for large-diameter polyethylene elbows according to claim 1, characterized in that: The upper half of the guide cage (25) is equipped with an upper support (31), and the lower half of the guide cage (25) is equipped with a lower support (32).

7. The injection molding equipment for large-diameter polyethylene elbows according to claim 1, characterized in that: The upper half of the guide cage (25) on the upper side of the bracket fixing plate (26) is also equipped with two flip covers (29) that can be opened and closed. Each flip cover (29) is connected to the guide cage (25) by ball joint (33), and the two flip covers (29) are connected by buckle (34). The opening and closing positions of the power wheel (28) and the flip covers (29) are staggered.

8. The injection molding equipment for large-diameter polyethylene elbows according to claim 1, characterized in that: A wheel seat bracket (35) is installed on the power wheel (28). A drive motor (36) is provided on one side of the wheel seat bracket (35). The output shaft of the drive motor (36) is connected to the wheel axle of the power wheel (28). A screw hole is provided on the guide cage (25) corresponding to the position of the wheel seat bracket (35). A screw rod (37) is installed in the screw hole. A crank handle (38) is provided at one end of the screw rod (37) that extends out of the guide cage (25). The other end of the screw rod (37) that extends into the guide cage (25) is installed on the wheel seat bracket (35) through a bearing. Turning the crank handle (38) can adjust the distance between the power wheel (28) and the injection mold.

9. An injection molding process for large-diameter polyethylene elbows, characterized in that: The process of processing large-diameter polyethylene elbows using any of the injection molding equipment described in claims 1-8 includes the following steps: ① Pull the injection pipe (4) outward along the radial track (17) on the diversion cover (3) to the outer edge of the diversion cover (3), close the sliding door (27) on the bracket fixing plate (26), put in the end cover (2), install the mandrel (6) onto the through hole (18) of the end cover (2), and slide down the concave channel (23) on the upper part (7), lower part (8), left part (9) and right part (10) of each unit inner mold according to the installation sequence of the unit inner mold, align the concave channel (23) on the upper part (7), lower part (8), left part (9) and right part (10) of each unit inner mold with the connecting rail (22) on the mandrel (6) to complete the installation of the inner mold; ②After the inner mold is installed in step ①, move the injection pipe (4) inward along the radial track (17) to the position of the molding cavity (1), and connect the injection pipe (4) to the diversion pipe (16) on the diversion cover (3). Then open the flip cover (29) and install all the unit outer molds on the end cover (2) in sequence. ③ After the outer mold is installed in step ②, close and lock the flip cover (29), adjust the power wheel (28) on the mold drive system to move to contact the outer mold, support the injection mold in the guide cage (25), and then open the sliding door (27) on the bracket fixing plate (26) to provide a channel for the injection mold to move down; ④ After the injection mold is installed and supported in step ③, the extruder (24) extrudes the polyethylene hot melt material, which enters the bottom of the molding cavity (1) through the injection pipe (4). At the same time, the spray pipe (30) cools the material as it enters the molding cavity (1). As the material is injected, the injection mold slowly moves down in a semi-circular direction under the drive of the power wheel (28). The injection pipe (4) continuously injects the polyethylene hot melt material into the molding cavity (1) in the vertical direction. At the same time, the spray pipe (30) cools the material around the corresponding position until the injection mold moves to the bottom position of the lower quarter circle of the mold drive system. The injection mold is completely filled with polyethylene hot melt material and cools to form the elbow product. ⑤ After the polyethylene elbow pipe in step ④ is processed, the injection pipe (4) is moved outward along the radial track (17) on the diversion cover (3), and the high pressure air chamber is connected. The high pressure air is injected into the injection pipe (4) to remove the polyethylene melt accumulated inside. At this time, the position of the injection pipe (4) in the guide cage (25) will not affect the movement of the injection mold. ⑥ Hook and fix the mandrel (6) at the lower end of the mold drive system with a hook. The power wheel (28) rotates in the opposite direction, driving the injection mold to rotate upward along the guide cage (25). At the same time, the mandrel (6) comes out until the injection mold moves to the position of the upper quarter circle of the guide cage (25) and the mandrel (6) comes out completely. ⑦ After the mandrel (6) in step ⑥ is completely removed from the injection mold, remove the end cap (2) from the inner mold and outer mold, and let it slide down along the mandrel (6) to the lower end of the guide cage (25) and reassemble it with the bottom end of the mandrel (6). ⑧ After the end cap (2) in step ⑦ is disassembled and slid down into place, slide the upper part (7) and lower part (8) of the first unit inner mold closest to the end cap (2) radially toward the center to remove it from the mold, and align the concave channel (23) on it with the connecting rail (22) on the mandrel (6), slide it down to install it in the position of the end cap (2), then move the left part (9) and right part (10) of this unit inner mold toward the middle, remove it from the mold, and slide it down along the connecting rail (22) of the mandrel (6) to install it in the position of the end cap (2), thus completing the demolding and reinstallation of the bottom unit inner mold. Repeat the above steps to demold and reinstall the inner molds of the subsequent units until all inner molds are demolded and reinstalled. At this time, the inner mold and the mandrel (6) are both in the lower quarter circle position of the guide cage (25). ⑨ After the inner mold is demolded and reassembled in step ⑧, close the sliding door (27), open the flip cover (29), adjust the position of the power wheel (28) to avoid interference during the disassembly of the outer mold, and disassemble the outer mold of each unit in the upper quarter circle of the guide cage (25) section by section until it is completely removed; ⑩ After all the outer molds in step ⑨ have been removed, the polyethylene elbow product that has been injection molded and demolded is lifted out at the position of the open flap (29) and inspected and put back into storage. The injection pipe (4) in the guide cage (25) will not affect the lifting out of the finished pipe. Then the flap (29) is closed. After the polyethylene elbow finished product in step 10 is taken out, adjust the power wheel (28) in the lower quarter circle of the guide cage (25) to press it onto the inner mold, open the sliding door (27), turn on the power wheel (28) to drive the reinstalled inner mold, mandrel (6) and end cap (2) to the position of the upper quarter circle of the guide cage (25), and close the sliding door (27). Step 11 After the inner mold, mandrel (6) and end cap (2) are moved to the position of the upper quarter circle of the guide cage (25), the injection pipe (4) is moved inward along the radial track (17) and reset, extending into the bottom position of the molding cavity (1) and connected to the diversion pipe (16) on the diversion cover (3). The flip cover (29) is opened, the unit outer mold is installed in sequence, and the end cap (2) is fixedly connected to the outer mold and inner mold. The position of the power wheel (28) is adjusted so that it is pressed against the outer mold. Finally, the sliding door (27) is opened and the flip cover (29) is closed to prepare for the next injection molding of polyethylene elbow.

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