Bracket-free PVC (polyvinyl chloride) extrusion die

Abstract

A cylindrical die cavity is formed in a rear die body and a front die body, a columnar damping die body is arranged in the die cavity, the rear end of the damping die body is connected with the rear wall of the die cavity, the front end of the damping die body is connected with an inner die body, a damping convex ring is arranged on the periphery of the damping die body, and the damping convex ring is connected with the rear wall of the die cavity. A feeding port of the die is formed in the side wall of the die cavity and located on the rear side of the damping convex ring. According to the PVC extrusion die disclosed by the utility model, materials extruded by the PVC extrusion die do not have a process of re-distributing and fusing a bracket, so that an extruded PVC pipe product does not have a bracket line, and the impact resistance of the PVC pipe is greatly improved.

Description

Technical Field

[0001] This utility model relates to the field of extrusion die technology, and in particular to a supportless PVC extrusion die. Background Technology

[0002] Impact resistance is a crucial indicator for PVC pipe products. Under the same material formulation and flow channel structure, the impact resistance is closely related to the product's support lines. At the support lines, the product's density is relatively low, making the pipe prone to breakage during impact tests. Currently, all known PVC extrusion dies rely on supports to maintain the overall die structure and ensure production safety. All PVC pipe products produced by such dies have support lines, significantly reducing their impact resistance. Therefore, developing a support-free PVC extrusion die to improve the impact resistance of PVC pipe products is of great significance. Patent document CN203844188U, published on September 24, 2014, discloses a PVC extrusion die structure, including a die, a mandrel, a die support, and a flow divider. The inclined sections of the die and mandrel form a compression zone, while the straight sections form a forming zone. The mandrel between the forming zone and the compression zone has protrusions, forming a compression flow channel. This structure can reduce flow divider marks on the die support to a certain extent, improving the quality of the plastic material. However, the PVC extrusion mold still has a mold support, and the support lines caused by the mold support still exist in the final PVC pipe product. The problem of low impact resistance of the PVC pipe product has not been solved. Utility Model Content

[0003] The purpose of this invention is to solve the problem that existing PVC extrusion molds all rely on supports to support the overall structure of the mold. Due to the relatively low density of the product at the support line, the pipe products are prone to breakage during impact tests. This invention provides a supportless PVC extrusion mold that can significantly improve the impact resistance of the produced PVC pipe products.

[0004] A further objective of this invention is to mitigate impact and pressure, optimize the flow path of PVC materials during the extrusion process, reduce resistance and turbulence, and improve the fluidity and uniformity of the material.

[0005] The technical solution adopted by this utility model to achieve the above-mentioned objective is a supportless PVC extrusion mold, including a rear mold body and a front mold body fixed thereto. The rear mold body and the front mold body have a cylindrical mold cavity inside. A columnar damping mold body is provided in the mold cavity. The rear end of the damping mold body is connected to the rear wall of the mold cavity. The front end of the damping mold body is connected to an inner mold body. A damping protrusion ring is provided on the outer periphery of the damping mold body. The mold inlet is located on the side wall of the mold cavity and behind the damping protrusion ring. The front ends of the inner mold body and the front mold body are respectively connected to a mandrel and a die. This invention eliminates the mold support structure. In order to support and fix the entire internal mold structure, the damping mold is directly connected to the rear mold. This also prevents the material from entering from the rear side of the rear mold and then expanding and being extruded in all directions, as is the case in the existing extrusion method. Therefore, this invention sets the feed port on the side wall of the mold cavity and on the rear side of the damping ring. This ensures that after the material is damped by the damping ring, it expands and is extruded evenly in a cylindrical shape. This achieves the purpose of eliminating the support line, improving the density and uniformity of the product, and greatly improving the impact resistance of the product.

[0006] Preferably, the damping mold is cylindrical, and the rear wall of the mold cavity is provided with a fixing hole adapted to the cylindrical damping mold, and the rear end of the damping mold is embedded in the fixing hole.

[0007] Preferably, the rear wall of the mold cavity is an inclined surface, the damping convex ring is inclinedly arranged on the outer peripheral surface of the damping mold body and its inclination direction is consistent with the inclination direction of the inclined surface, the mold inlet is located above the top of the inclined surface, and the upper part of the damping convex ring is close to the mold inlet.

[0008] Preferably, the height of the damping convex ring increases linearly from the side near the feed inlet to the side away from the feed inlet.

[0009] Preferably, the gap between the damping ring near the feed inlet and the mold cavity sidewall is 1.5-2.5 times that between the damping ring away from the feed inlet and the mold cavity sidewall.

[0010] Preferably, the rear end face of the damping mold is provided with a positioning pin, and the bottom surface of the fixing hole is provided with a positioning hole corresponding to the positioning pin.

[0011] Preferably, the cross-section of the damping convex ring is arc-shaped, and the two ends of the cross-section of the damping convex ring are provided with transition arcs at the connection between them and the circumferential surface of the damping mold body, and the connection between the feed port and the membrane cavity is provided with transition arcs.

[0012] Preferably, the angle α between the inclined surface of the rear wall of the mold cavity and the center line of the mold cavity is 50-70 degrees, and the plane containing the center line of the damping convex ring is parallel to the inclined surface of the rear wall of the mold cavity.

[0013] Preferably, the rear wall of the rear mold body and the center of the damping mold body are provided with vent holes, and the vent holes are in a straight line.

[0014] The beneficial effect of this utility model is that it effectively solves the problem that existing PVC extrusion molds all need to rely on supports to support the overall structure of the mold. Due to the relatively low density of the product at the support line, the pipe products are prone to breakage during impact tests. The supportless PVC extrusion mold of this utility model does not have a support re-diversion and fusion process for the extruded plastic. Therefore, the extruded PVC pipe products do not have support lines, which greatly improves the impact resistance of PVC pipes and has high practical value. Attached Figure Description

[0015] Figure 1 This is a structural cross-sectional view of a supportless PVC extrusion mold according to this utility model.

[0016] Figure 2 This is a schematic diagram of the structure of the damping modulus of this utility model.

[0017] Figure 3 This is a structural cross-sectional view of the rear mold body of this utility model.

[0018] Figure 4 yes Figure 2 The left view.

[0019] Figure 5 This is a three-dimensional structural diagram of the rear mold body of this utility model.

[0020] In the diagram: 1. Rear mold body, 2. Front mold body, 3. Mold cavity, 4. Damping mold body, 5. Rear wall, 6. Inner mold body, 7. Damping convex ring, 8. Feed port, 9. Mandrel, 10. Die, 11. Fixing hole, 12. Positioning pin, 13. Positioning hole, 14. Vent hole, R. Transition arc. Detailed Implementation

[0021] The specific implementation methods of the present invention will be further described below through examples and in conjunction with the accompanying drawings.

[0022] Example

[0023] exist Figure 1In the illustrated embodiment, a supportless PVC extrusion mold includes a rear mold body 1 and a front mold body 2 fixed thereto. The rear mold body 1 and the front mold body 2 form a cylindrical mold cavity 3 inside. A columnar damping mold body 4 is provided inside the mold cavity 3. The rear end of the damping mold body 4 is connected to the rear wall 5 of the mold cavity 3, and the front end of the damping mold body 4 is connected to an inner mold body 6. A damping protrusion ring 7 is provided on the outer periphery of the damping mold body 4. The mold inlet 8 is located on the side wall of the mold cavity 3 and behind the damping protrusion ring 7. The front ends of the inner mold body 6 and the front mold body 2 are respectively connected to a mandrel 9 and a die 10. In this embodiment, the rear mold body 1 has a groove at its cavity, and the front mold body 2 has a raised stepped structure at its cavity. The stepped structure is adapted to the groove and is used to position the front mold body 2 onto the rear mold body 1. Six fixing screw holes are provided around the cavity opening of the mating surface of the rear mold body 1 and the front mold body 2. Screw holes for screws are provided around the cavity opening of the corresponding front mold body 2. The rear mold body 1 and the front mold body 2 are positioned by the groove and the stepped structure and then fixed with screws. The front ends of the inner mold body 6 and the front mold body 2 are respectively connected to the mandrel 9 and the die 10. The front end of the inner mold body 6 is connected to the mandrel 9, and the tapered surface at the front end of the outer periphery of the inner mold body 6 is smoothly connected to the tapered surface at the rear end of the outer periphery of the mandrel 9. The front end of the front mold body 2 is connected to the die 10, and the tapered surface at the front end of the inner wall of the front mold body 2 is smoothly connected to the tapered surface at the rear end of the inner wall of the die 10, thereby forming a PVC extrusion channel. The PVC extrusion die of this invention has a rear die body 1 and a front die body 2 fixedly connected, forming a cylindrical die cavity 3 inside. This die cavity 3 structure is similar to that of existing PVC extrusion dies. A columnar damping die body 4 is provided inside the die cavity 3, with a damping ring 7 on its outer periphery. The rear end of the damping die body 4 is connected to the rear wall 5 of the die cavity 3, and the front end is connected to the inner die body 6. Because this invention eliminates the die support, the damping die body is directly connected to the rear die body to support and fix the entire internal die structure. This connection method also prevents the material from entering from the rear side of the rear die and then expanding outwards in the existing method. Therefore, this invention sets the feed inlet on the side wall of the die cavity, behind the damping ring, ensuring that the material, after being damped by the damping ring, expands and is extruded uniformly in a cylindrical shape, thus eliminating the support line and greatly improving the product's impact resistance. The design of the damping die body and damping ring can effectively control the flow rate and pressure of the PVC material, improving the stability and uniformity of the extrusion process. This invention achieves damping and control during the PVC material extrusion process through the design of a damping mold and a damping convex ring. The damping mold, fixed on the rear mold body, serves as the support for the entire inner flow channel, eliminating the traditional mold support frame structure. At the same time, the overall extrusion molding is achieved through side feeding. Since the material in this mold does not need to pass through the support frame and there are no support lines, the impact resistance of the product is significantly better than that of similar traditional products.The PVC extrusion mold of this invention can be widely used in the extrusion molding process of PVC pipes and other products, especially in the manufacturing process of products requiring high quality.

[0024] In a preferred embodiment, the damping modulus 4 is cylindrical (see...). Figure 2 The rear wall of the mold cavity 3 is provided with a fixing hole 11 that matches the cylindrical damping mold body 4, and the rear end of the damping mold body 4 is embedded in the fixing hole 11. The fixing hole on the rear wall of the mold cavity matches the diameter of the cylindrical damping mold body. Embedding the rear end of the damping mold body in the fixing hole stably fixes the cylindrical damping mold body, achieving precise fixation and ensuring its stability and reliability during the extrusion process. The damping mold body embedded in the fixing hole effectively prevents its movement or deformation during material extrusion, enhancing the overall stability of the mold. Furthermore, this fixing method simplifies the installation process of the damping mold body and improves the assembly efficiency of the mold; simultaneously, by replacing the damping mold body, the process parameters of the mold can be easily adjusted.

[0025] In a preferred embodiment, the rear wall 5 of the mold cavity 3 is an inclined surface. The damping ring 7 is inclined on the outer peripheral surface of the damping mold body 4, and its inclination direction is consistent with the inclination direction of the inclined surface. The mold inlet 8 is located above the top of the inclined surface, and the upper part of the damping ring 7 is close to the mold inlet 8. The front section (upstream section) of the inlet is threaded to connect to the flange device of the extruder, and the rear section is a smooth flow channel surface to guide the material into the flow channel. The rear wall of the mold cavity is an inclined surface, that is, the rear wall of the mold cavity is inclined backward on the side near the inlet, so that the length of the mold cavity on the side near the inlet is greater than the length of the mold cavity on the side away from the inlet. At the same time, the damping ring is inclined on the outer peripheral surface of the damping mold body, and its inclination direction is consistent with the inclination direction of the inclined surface. Thus, the flow channel at the inlet is in an inclined state, and the mold inlet is located above the top of the inclined surface, with the upper part of the damping ring close to the mold inlet. After the material enters the rear die, to prevent it from directly impacting the die and causing excessive internal pressure, the flow channel surface at the rear end of the rear die is set at a certain angle to mitigate impact and pressure, guiding the material forward during extrusion. The material flowing out of the inlet is influenced by the inclined surface and the damping ring, resulting in a guiding effect towards the front and downward side of the die cavity (the side of the die cavity furthest from the inlet). Simultaneously, during forward extrusion, the material is damped and diverted by the damping ring, optimizing the flow path of the PVC material during extrusion, reducing resistance and turbulence, and improving material flowability and uniformity. Positioning the inlet above the top of the inclined surface allows the PVC material to enter the die cavity more smoothly, reducing feeding resistance and improving feeding efficiency. The upper part of the damping ring is close to the inlet, allowing for better control of material flow and pressure, improving the uniformity of material extrusion.

[0026] In a preferred embodiment, the height of the damping protrusion 7 increases linearly from the side closer to the feed inlet 8 to the side farther away from the feed inlet 8. The variation law of the damping protrusion height is that the height of the damping protrusion increases linearly from the side closer to the feed inlet to the side farther away from the feed inlet. During the forward extrusion process after the material enters the die, due to the initial extrusion speed of the material conveyed by the screw in the barrel, it will inevitably be conveyed towards the end farther from the feed inlet first. This will lead to inconsistent material quantity inside the flow channel, and the final extruded product will also have performance problems. To solve this problem, this invention sets a damping die inside the flow channel, which sets a damping protrusion as close as possible to the feed inlet. The size of its protrusion structure is uneven, with one end larger than the other, gradually decreasing in size in the middle. To ensure that the amount of material is consistent near and far from the feed inlet, the larger end is located at the end furthest from the feed inlet, and the smaller end is located at the end near the feed inlet. When the material passes through the damping protrusion, the flow channel at the larger end becomes narrower and longer, and the material flow rate slows down, thereby ensuring that the amount of material in the subsequent flow channel is consistent.

[0027] In a preferred embodiment, the gap between the damping ring 7 near the inlet 8 and the sidewall of the mold cavity 3 is 1.5-2.5 times that between the damping ring 7 away from the inlet 8 and the sidewall of the mold cavity 3. This illustrates the variation of the gap distance between the highest point of the damping ring and the sidewall of the cylindrical mold cavity. Typically, the gap distance between the damping ring near the inlet and the sidewall of the mold cavity is 1.5-2.5 times that between the damping ring away from the inlet and the sidewall of the mold cavity. Figure 1 The embodiment described in the previous example is doubled. For instance, if the gap between the damping ring near the feed inlet and the mold cavity sidewall is 6 mm, then the gap between the damping ring away from the feed inlet and the mold cavity sidewall is 3 mm. During the extrusion process after the material enters the mold body, due to the initial extrusion velocity, the material preferentially moves towards the end away from the feed inlet. This leads to inconsistent material flow within the flow channel surrounding the internal mold body, resulting in uneven extrusion and ultimately performance problems in the extruded product. In this invention, the larger gap between the damping ring near the feed inlet and the mold cavity sidewall reduces the resistance of the mold cavity near the feed inlet, making it easier for PVC material to enter the mold cavity. Conversely, the smaller gap between the damping ring away from the feed inlet and the mold cavity sidewall increases the resistance of the PVC material during extrusion, ultimately ensuring uniform extrusion of the material within the mold cavity and significantly improving the consistency of the PVC product material.

[0028] In a preferred embodiment, the rear end face of the damping mold 4 is provided with four positioning pins 12, and the bottom surface of the fixing hole 11 is provided with four positioning holes 13 corresponding to the positioning pins 12 (see...). Figure 4 Figure 5The rear end face of the damping mold body is equipped with a positioning pin to ensure accurate positioning of the mold body during installation. The bottom surface of the fixing hole has a positioning hole corresponding to the positioning pin for precise alignment and fixation. Because the damping protrusion on the damping mold body of this invention has directionality, the protrusion structure is larger at one end and smaller at the other, gradually decreasing in size in the middle. To ensure consistent material flow near and far from the inlet, the larger end of the damping protrusion must be at the end furthest from the inlet, and the smaller end must be at the end near the inlet; misalignment is not allowed. Therefore, by setting the positioning pin and positioning hole, accurate positioning of the damping mold body during installation is ensured, preventing quality degradation of PVC pipe products due to damping protrusion misalignment. The use of positioning pins and positioning holes also simplifies the installation process and facilitates operation.

[0029] In a preferred embodiment, the damping ring 7 has an arc-shaped cross-section. The ends of the damping ring 7's cross-section are connected to the circumferential surface of the damping die 4 with transition arcs R. Similarly, the connection between the feed inlet 8 and the membrane cavity is also provided with a transition arc R. The arc-shaped cross-section of the damping ring better reduces the force of material flow, ensuring extrusion stability. The transition arcs at the ends of the damping ring's cross-section and the circumferential surface of the damping die reduce resistance and friction during material flow, improving flow efficiency. Similarly, the connection between the feed inlet and the membrane cavity also has a transition arc. This ensures that all corners of the flow channel are rounded, mitigating the impact force during feeding and ensuring a smooth transition. This structure further optimizes the material flow path, improving mixing uniformity and extrusion stability. It effectively reduces resistance and friction during extrusion, increases extrusion efficiency, and reduces energy consumption.

[0030] In a preferred embodiment, the angle α between the inclined surface of the rear wall 5 of the mold cavity 3 and the centerline of the mold cavity 3 is 50-70 degrees, and the plane containing the centerline of the damping ring 7 is parallel to the inclined surface of the rear wall 5 of the mold cavity 3. Typically, the angle (acute angle) α between the inclined surface of the rear wall of the mold cavity and the centerline of the mold cavity is 50-70 degrees. Figure 3 In the embodiment shown, α is 60 degrees, and the plane containing the center line of the damping convex ring is parallel to the inclined surface of the rear wall of the mold cavity, i.e. Figure 2 In the embodiment shown, the angle (acute angle) between the plane containing the center line of the damping convex ring and the length direction of the damping mold is also 60 degrees.

[0031] In a preferred embodiment, both the rear wall 5 of the rear mold body 1 and the center of the damping mold body 4 are provided with vent holes 14, which are aligned in a straight line. This design, with vent holes on both the rear wall of the rear mold body and the center of the damping mold body, provides better gas discharge and pressure balance. Furthermore, aligning the vent holes in a straight line further optimizes the gas discharge path, improving gas discharge efficiency and extrusion stability. By designing the vent holes and aligning them in a straight line, the gas discharge path and efficiency can be significantly optimized, preventing the influence of gas within the membrane cavity on the extrusion process and avoiding porosity in the PVC pipe that could affect product quality.

[0032] This invention relates to a supportless PVC extrusion die. In PVC pipe products, by eliminating support lines, the overall impact resistance of the pipe is improved. Material is fed from the inlet of the rear die. Because the material is initially extruded towards the far inlet end, the subsequent material quantity is inconsistent. However, by adding a damping die, the material flow velocity is significantly reduced as it passes through the damping die, due to the narrower and longer flow channel at the far inlet. This ensures that the flow velocity at the far inlet end matches that at the near inlet, thus guaranteeing a consistent amount of extruded material. Throughout this process, since there is no support for re-diversion and fusion, the extruded product does not have support lines. This solves the problem in existing PVC extrusion dies that rely on supports for the overall die structure. The relatively low density of the product at the support lines makes the pipe prone to breakage during impact tests, thus greatly improving the pipe's impact resistance.

[0033] In addition to the above embodiments, within the scope disclosed in the claims and specification of this utility model, the technical features or technical data of this utility model can be reselected and combined to form new embodiments. These can be achieved by those skilled in the art without creative effort. Therefore, these embodiments not described in detail in this utility model should also be regarded as specific embodiments of this utility model and within the protection scope of this utility model.

Claims

1. A supportless PVC extrusion die, comprising a rear die body and a front die body fixed thereto, characterized in that, The rear mold body and the front mold body have cylindrical mold cavities inside. A columnar damping mold body is provided inside the mold cavity. The rear end of the damping mold body is connected to the rear wall of the mold cavity, and the front end of the damping mold body is connected to the inner mold body. A damping protrusion ring is provided on the outer periphery of the damping mold body. The mold inlet is located on the side wall of the mold cavity and behind the damping protrusion ring. The front ends of the inner mold body and the front mold body are respectively connected to the mandrel and the die. The rear wall of the mold cavity is an inclined surface. The damping convex ring is inclined on the outer peripheral surface of the damping mold body and its inclination direction is consistent with the inclination direction of the inclined surface. The mold inlet is located above the top of the inclined surface, and the upper part of the damping convex ring is close to the mold inlet.

2. The supportless PVC extrusion die according to claim 1, characterized in that, The damping mold is cylindrical, and the rear wall of the mold cavity is provided with a fixing hole that is adapted to the cylindrical damping mold. The rear end of the damping mold is embedded in the fixing hole.

3. The supportless PVC extrusion die according to claim 1, characterized in that, The height of the damping cam increases linearly from the side closer to the feed inlet to the side farther away from the feed inlet.

4. The supportless PVC extrusion die according to claim 1, characterized in that, The gap between the damping ring near the feed inlet and the mold cavity sidewall is 1.5-2.5 times that between the damping ring away from the feed inlet and the mold cavity sidewall.

5. The supportless PVC extrusion die according to claim 2, characterized in that, The rear end face of the damping mold is provided with a positioning pin, and the bottom surface of the fixing hole is provided with a positioning hole corresponding to the positioning pin.

6. The supportless PVC extrusion die according to claim 1, characterized in that, The cross-section of the damping convex ring is arc-shaped, and the two ends of the cross-section of the damping convex ring are provided with transition arcs at the connection between them and the circumferential surface of the damping mold body. The connection between the feed port and the mold cavity is also provided with a transition arc.

7. The supportless PVC extrusion die according to claim 1, characterized in that, The angle α between the inclined surface of the rear wall of the mold cavity and the center line of the mold cavity is 50-70 degrees, and the plane containing the center line of the damping convex ring is parallel to the inclined surface of the rear wall of the mold cavity.

8. The supportless PVC extrusion die according to any one of claims 1-7, characterized in that, Ventilation holes are provided on the rear wall of the rear mold body and the center of the damping mold body, and the ventilation holes are in a straight line.

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