Injection molding screw

Abstract

This invention discloses an injection molding screw, belonging to the field of injection molding equipment structure, comprising: a guide screw, the guide screw including a first threaded section; a first guide wheel, the first guide wheel being installed at the discharge end of the first threaded section, and having a plurality of first guide plates circumferentially arranged with a rotation direction opposite to that of the first threaded section; and a second guide wheel, the second guide wheel being located on the side of the first guide wheel away from the first threaded section, and having a plurality of second guide plates circumferentially arranged with a rotation direction the same as that of the first threaded section. This design, by installing two guide wheels in opposite directions at the discharge end of the injection molding screw, uniformly stirs the molten plastic inside the screw and barrel, resulting in a more uniform density distribution of the molten plastic and solving the problem of excessively high or low local strength in injection molded products.

Description

Technical Field

[0001] This invention relates to an injection molding tool, and more specifically, to an injection molding screw. Background Technology

[0002] Many existing injection molding machines use screws as the feeding tool. During the injection molding process, plastic is melted between the screw and the barrel, and then the molten plastic is pushed into the injection cavity for molding. However, in existing injection molding technology, the molten plastic tends to form an unevenly dense mixture inside the screw and barrel. This results in some areas having excessively high density and others having excessively low density, leading to uneven strength in the final product. This affects the overall quality of the product and reduces its lifespan.

[0003] For example, Chinese Patent Publication No. CN216658809U, published on November 30, 2021, is entitled "Anti-slip Injection Screw for Injection Molding Machine". This application includes a screw head and a push screw. The screw head is installed at the front end of the push screw. Multiple conveying grooves are provided on the circular outer wall of the screw head. This solution can avoid the situation where the raw material solidified on the outer wall of the injection screw is not completely remelted and sticks together. However, it cannot achieve a uniform density distribution of the molten plastic inside the screw and barrel, which can easily lead to the phenomenon of excessively high or low local strength of the product. Summary of the Invention

[0004] This invention overcomes the problem of inconsistent surface strength of injection molded products due to uneven density of molten plastic in the prior art. It provides an injection screw in which two guide rollers are installed in opposite directions at the discharge port of the injection screw to stir the molten plastic inside the screw and barrel evenly, thus solving the problem of excessively high or low local strength of injection molded products.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: an injection molding screw, comprising: a guide screw, the guide screw including a first threaded section; a first guide wheel, the first guide wheel being installed at the discharge end of the first threaded section, and having a plurality of first guide plates with a rotation direction opposite to that of the first threaded section in the circumferential direction; and a second guide wheel, the second guide wheel being disposed on the side of the first guide wheel away from the first threaded section, and having a plurality of second guide plates with a rotation direction the same as that of the first threaded section in the circumferential direction. In this design, the rotation direction of the guide screw is the same as the thread direction of the first threaded section. The molten plastic on the guide screw is propelled along the thread direction of the first threaded section. The rotation direction of the first guide plate on the first guide wheel is opposite to that of the thread of the first threaded section, which can hinder the moving molten plastic, thereby dispersing the propelling molten plastic and making the molten plastic more uniform. When the molten plastic continues to move to the second guide wheel, the second guide plate on the second guide wheel can stir the molten plastic again. The rotation direction of the second guide plate on the second guide wheel is the same as that of the thread of the first threaded section, that is, the same as the rotation direction of the guide screw. This can propel the molten plastic on the second guide wheel, increasing the discharge pressure of the molten plastic to a certain extent. Furthermore, the installation methods of the first and second guide wheels are opposite, that is, the rotation directions of their respective guide plates are opposite, which can counteract the axial force generated during their rotation, eliminating the need for additional structures to counteract the axial force.

[0006] Preferably, the first threaded section has several guide channels in the same direction as the thread. These guide channels penetrate the threads of the first threaded section and are in the same direction as the thread. When the molten plastic flows to the first threaded section, some of the molten plastic can continue to move along the thread groove, while some enters the next thread groove directly through the guide channels. This process disperses and remixes the molten plastic, effectively acting as a stirrer. Furthermore, having multiple guide channels allows for more uniform stirring of the molten plastic, resulting in a more even density distribution and ensuring the quality of the injection-molded product.

[0007] Preferably, the first threaded section has several guide channels with the direction opposite to the thread direction. The guide channels pass through the threads of the first threaded section and are opposite to the thread direction. When the molten plastic flows to the first threaded section, part of the molten plastic continues to move along the thread groove, while part of the molten plastic flows back from the guide channel to the previous thread groove. This not only disperses and remixes the molten plastic in its original state, but also prolongs the melting time of some of the molten plastic. Setting multiple guide channels allows for multiple backflows of the molten plastic, resulting in more thorough mixing of the molten plastic, making the density of the molten plastic more uniform, and ensuring the quality of the injection molded product.

[0008] Preferably, the feed screw further includes a feed section and a second threaded section located between the feed section and the first threaded section, wherein a secondary thread is arranged between the threads of the second threaded section. The entire feed screw body consists of a feed section, a second threaded section, and a first threaded section, from the feed end to the discharge end. The feed section is used to receive solid plastic granules and to initially melt the solid plastic. When the molten plastic enters the second and first threaded sections, it is already in a molten state. As the solid plastic granules gradually melt, they change from solid to liquid, and the space they occupy within the feed screw decreases. Therefore, the propulsion speed of the molten plastic in the second and first threaded sections is lower than that in the feed section. Thus, the plastic propulsion speed slows down at the beginning of the second threaded section, which can prolong the heating time of the plastic. A secondary thread is arranged between the threads in the second threaded section to separate the plastic entering the second threaded section, thereby increasing the heating area of ​​the plastic. At the same time, due to the addition of the secondary thread, the temperature of the secondary thread teeth rises during continuous heating, which can also form a heating element, making the plastic in the second threaded section more uniformly heated and improving the melting effect. This design extends the heating time and increases the heating area, ensuring that the plastic is fully heated and melted.

[0009] Preferably, the feed screw is externally provided with a barrel, the inner diameter of which matches the outer diameter of the feed screw and the outer diameters of the first and second guide wheels. The cooperation between the feed screw and the barrel allows the plastic to be smoothly propelled within the screw and barrel. The matching of the barrel's inner diameter with the feed screw's outer diameter prevents the feed screw from rotating inside the barrel if its outer diameter is too large, or from flowing through the gap between the feed screw and the barrel if its outer diameter is too small, resulting in poor plastic melting. Similarly, the matching of the barrel's inner diameter with the outer diameters of the first and second guide wheels prevents the guide wheels from directly contacting the inner wall of the barrel if their outer diameters are too large, damaging the interior. Conversely, if their outer diameters are too small, the molten plastic adhering to the inner wall of the barrel cannot be stirred, affecting the stirring effect.

[0010] Preferably, several sets of heaters are arranged at intervals on the outside of the barrel corresponding to different threaded sections of the guide screw. Different heaters are required for different positions on the guide screw, and the number of heaters also varies. For the feeding section, since the plastic is in granular form, it needs to be melted, which requires more heat, so more heaters are needed here. For the second threaded section, the plastic is basically melted, so fewer heaters are needed to ensure melting effect compared to the feeding section. For the first threaded section, the plastic is already completely molten, and only heat preservation is required, so the number of heaters is minimized here.

[0011] Preferably, the device also includes a screw head, which is fixedly connected to the end of the guide screw where the second guide wheel is located via a check ring. The screw head is located at the discharge end of the guide screw, i.e., where the second guide wheel is located, and guides the molten plastic into the nozzle position. The check ring is fitted onto the screw head and abuts against the guide screw, preventing the molten plastic at the screw head from flowing back.

[0012] Preferably, the screw head is connected to a nozzle via a connector. The connector has a groove that matches the screw head and a connecting block for connecting the nozzle. One end of the connector has a groove that matches the screw head and is rotatably connected to the screw head. The other end of the connector is fixed with a connecting block, and the connecting block has a nozzle. The connecting block has a through hole with a gradually decreasing diameter along the direction from the screw head to the nozzle. The groove, the through hole, and the nozzle are interconnected, ensuring smooth spraying and effectively increasing the spraying pressure. The connector is fixed to the barrel by screws or other fasteners.

[0013] Compared with the prior art, the beneficial effects of the present invention are: (1) it can make the molten material between the screw and the barrel evenly stirred; (2) the two guide wheels installed in opposite directions can balance the axial force generated by each; (3) the structure is simple, easy to use, and can ensure product quality and prevent uneven surface strength of the product. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the material guide screw of the present invention.

[0015] Figure 2 This is a schematic diagram of the first and second guide wheels of the present invention.

[0016] Figure 3 These are sectional views, front views, and isometric views of the present invention.

[0017] Figure 4 for Figure 3 A magnified view of A in the middle.

[0018] Figure 5 This is a schematic diagram of Embodiment 2 of the present invention.

[0019] Figure 6 This is a schematic diagram of Embodiment 3 of the present invention.

[0020] In the diagram: 1. Feeding screw, 2. First threaded section, 3. First guide wheel, 4. Second guide wheel, 5. First guide plate, 6. Second guide plate, 7. Feeding section, 8. Second threaded section, 9. Secondary thread, 10. Barrel, 11. Heater, 12. Screw head, 13. Check ring, 14. Connecting body, 15. Nozzle, 16. Feeding channel, 17. Connecting block, 18. Feed inlet. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0022] Example 1: As Figures 1 to 4 The injection screw shown includes a barrel 10 and a guide screw 1. The barrel 10 is sleeved outside the guide screw 1, and the guide screw 1 can rotate inside the barrel 10. The guide screw 1 has a feed section 7, a second threaded section 8, and a first threaded section 2 arranged sequentially from the feed end to the discharge end. Two guide wheels are also provided on the first threaded section 2 of the guide screw 1 near the discharge port: a first guide wheel 3 and a second guide wheel 4. The first guide wheel 3 is arranged close to the discharge side of the first threaded section 2, and the second guide wheel 4 is installed at a distance from the first threaded section 2. Further away from the outlet side of section 2, a guide column is provided between the first guide wheel 3 and the second guide wheel 4. Several guide grooves are arranged on the guide column. The first guide wheel 3 and the second guide wheel 4 are evenly arranged with the first guide plate 5 and the second guide plate 6 in the circumferential direction. The first guide plate 5 on the first guide wheel 3 has the opposite rotation direction to the thread rotation direction of the guide screw 1, that is, the opposite rotation direction to the thread rotation direction of the first threaded section 2. The second guide plate 6 on the second guide wheel 4 has the same rotation direction as the thread rotation direction of the guide screw 1, that is, the same rotation direction as the thread rotation direction of the first threaded section 2. In this design, the rotation direction of the guide screw 1 is consistent with its thread direction, which can drive the plastic between the guide screw 1 and the barrel 10. The barrel 10 is also provided with a feed port 18 at the feed section 7 for plastic particles to enter the guide screw 1. When the plastic particles enter the feed section 7 of the guide screw 1, the plastic particles begin to melt into a liquid state and are pushed towards the second thread section 8. When the plastic flows to the second thread section 8, it is basically completely molten and finally enters the first thread section 2, and then reaches the position of the first guide wheel 3. Since the rotation direction of the first guide wheel 3 is consistent with the rotation direction of the guide screw 1, but the rotation direction of its first guide plate 5 is opposite to the thread direction of the guide screw 1, when the molten plastic comes into contact with the first guide plate 5 on the first guide wheel 3, the first guide plate 5 can act as an obstacle to the moving molten plastic. The first guide wheel 3 is used to disperse the molten plastic being pushed forward, making the molten plastic more uniform. Then, the molten plastic is pushed to the second guide wheel 4 through the guide groove on the guide column. The second guide plate 6 on the second guide wheel 4 can stir the molten plastic again. Since the rotation direction of the second guide wheel 4 is the same as the rotation direction of the guide screw 1, and the rotation direction of the second guide plate 6 is the same as the thread rotation direction of the guide screw 1, that is, the rotation direction of the second guide plate 6 is the same as the rotation direction of the guide screw 1, the second guide plate 6 can push the molten plastic on the second guide wheel 4, which increases the discharge pressure of the molten plastic to a certain extent. In addition, the installation method of the first guide wheel 3 and the second guide wheel 4 is opposite, that is, the rotation direction of their respective guide plates is opposite, which can cancel the axial force generated when they rotate, and there is no need to add an additional structure to cancel the axial force.

[0023] The outer surface of the feed cylinder 10 is equipped with a different number of heaters 11 depending on the different parts of the feed screw 1, such as... Figure 3 As shown, heater 11 is mainly a heating ring. Feed section 7 is used for the entry of solid plastic granules and for the initial melting of the solid plastic; therefore, it requires the highest heat. Thus, two sets of heaters 11 are arranged outside the barrel 10, with each set containing at least three heaters 11. When the plastic enters the second threaded section 8, a large amount of heat is also required to ensure complete melting; therefore, two sets of heaters 11 are arranged outside the barrel 10, with each set containing two to three heaters 11. When the molten plastic enters the first threaded section 2, it mainly performs heat preservation work, so the required heat is smaller. Only two to three sets of heaters 11 are needed outside the barrel 10, with each set containing two heaters 11. Furthermore, the heaters 11 are spaced apart to ensure more uniform heating. When the molten plastic enters the second threaded section 8 and the first threaded section 2, it is already in a molten state. During the gradual melting process of the solid granular plastic in section 7, it gradually changes from a solid to a liquid state, and the space it occupies within the feed screw 1 becomes smaller. Therefore, the pushing speed of the molten plastic in the second threaded section 8 and the first threaded section 2 will be less than the pushing speed of the plastic in the feed section 7. Thus, the plastic pushing speed slows down from the second threaded section 8, which can prolong the heating time of the plastic. The second threaded section 8 is used to prolong the heating time and heating effect of the plastic. A secondary thread 9 is arranged between the threads of the second threaded section 8, which can separate the plastic entering the second threaded section 8, thereby increasing the heating area of ​​the plastic. At the same time, due to the addition of the secondary thread 9, the thread temperature of the secondary thread 9 increases during continuous heating, which can also form a heating element, making the plastic in the second threaded section 8 more uniformly heated and the melting effect better. This scheme prolongs the heating time and increases the heating area, which can ensure that the plastic is fully heated and melted.

[0024] The inner diameter of the barrel 10 is matched with the maximum outer diameter of the guide screw 1, the first guide wheel 3 and the second guide wheel 4. The cooperation between the guide screw 1 and the barrel 10 allows the plastic to be smoothly pushed inside the guide screw 1 and the barrel 10. If the maximum outer diameter of the guide screw 1 is too large or too small, it will affect the plastic. If the outer diameter of the guide screw 1 is too large, it will not be able to rotate inside the barrel 10, and the plastic will not be able to be pushed forward. If the outer diameter of the guide screw 1 is too small, some of the molten plastic will not be pushed along the threaded groove, but will flow through the gap between the guide screw 1 and the barrel 10, resulting in poor plastic melting. The inner diameter of the barrel 10 also matches the outer diameter of the first guide wheel 3 and the second guide wheel 4. If the outer diameter of the first guide wheel 3 and the second guide wheel 4 is too large, the first guide plate 5 and the second guide plate 6 will directly contact the inner wall of the barrel 10, damaging the internal structure. If the outer diameter of the first guide wheel 3 and the second guide wheel 4 is too small, the molten plastic that is in close contact with the inner wall of the barrel 10 will not be stirred, affecting the stirring effect.

[0025] A screw head 12 is fixedly connected to the discharge end of the feed screw 1. The screw head 12 is matched with a connector 14. The other end of the connector 14 is connected to the nozzle 15 through a connecting block 17. Finally, the entire connector 14 is fixed to the barrel 10 by screws and other fasteners. The groove on the connector 14 that matches the screw head 12 is connected to the connecting block 17 and the nozzle 15 to ensure that the plastic is sprayed out smoothly. The connecting block 17 is provided with a through hole whose diameter gradually decreases along the direction from the screw head 12 to the nozzle 15, which can effectively increase the spraying pressure. The rod of the screw head 12 is also fitted with a check ring 13 to prevent the molten plastic at the screw head 12 from flowing back.

[0026] This solution can make the density distribution of the molten material inside the injection molding equipment more uniform, thereby avoiding the problem of excessively high or low local strength in the product due to uneven density, and improving the overall quality of the injection molded product.

[0027] Example 2: As Figure 5 The injection screw shown differs from that of Embodiment 1 only in that a material guide channel 16 is provided on the thread of the first thread segment 2. The direction of the material guide channel 16 is along the direction of the thread and it passes through the thread at an incline. The number of material guide channels 16 can be set according to actual needs, and the material guide channels 16 are evenly arranged on the thread.

[0028] Because the density distribution of the plastic is uneven when it melts in the second threaded section 8, when the molten plastic is pushed from the second threaded section 8 to the first threaded section 2, the molten plastic moves along the thread direction. When the molten plastic flows to the first threaded section 2, part of the molten plastic can continue to move along the thread groove, while part of it directly enters the next thread groove through the guide channel 16. This process disperses and remixes the molten plastic, effectively acting as a stirrer. Furthermore, setting multiple guide channels 16 allows for more uniform stirring of the molten plastic, resulting in a more uniform density distribution in each part and ensuring the quality of the injection molded product. Compared to Example 1, this solution adds a stirring operation, further improving the density uniformity of the molten plastic.

[0029] It is worth noting that the material guide channel 16 in this solution can be a through groove directly opened on the thread, that is, the thread is discontinuous, or a through hole opened on the thread. Both of these forms are effective and have basically the same effect.

[0030] Example 3: As Figure 6 The injection screw shown differs from that of Embodiment 2 only in that the direction of the guide channel 16 is reversed. That is, a guide channel 16 penetrating the thread is provided on the thread of the first thread segment 2. The direction of the guide channel 16 is opposite to the direction of the thread and is arranged obliquely on the thread.

[0031] When the molten plastic flows to the first threaded section 2, a portion of the molten plastic continues to move along the threaded groove, while another portion flows back from the guide channel 16 to the previous threaded groove. This not only disperses and remixes the molten plastic in its original state but also extends the melting time of a portion of the molten plastic. Setting multiple guide channels 16 allows for multiple backflows of the molten plastic, resulting in more thorough mixing, a more uniform density, and ensuring the quality of the injection-molded product. Compared to Example 2, this solution increases the mixing time of the molten plastic and adds an extra mixing operation compared to Example 1, resulting in a more uniform density of the molten plastic.

Claims

1. An injection molding screw characterized by, The utility model relates to a material feeding screw rod, comprising: a material feeding screw rod, comprising a first threaded section at the material feeding screw rod discharge end; a first material feeding wheel installed at the discharge end of the first threaded section and provided with a plurality of first material feeding pieces in the opposite direction of the first threaded section; a second material feeding wheel provided on the side of the first material feeding wheel away from the first threaded section and provided with a plurality of second material feeding pieces in the same direction as the first threaded section; 2. An injection molding screw as defined in claim 1 wherein, the threads on the first threaded section are provided with a plurality of material feeding channels in the same direction as the threads, which pass through the thread of the first threaded section.

3. An injection molding screw as defined in claim 1 wherein, the threads on the first threaded section are provided with a plurality of material feeding channels in the opposite direction of the threads, which pass through the thread of the first threaded section.

4. An injection molding screw as defined in any one of claims 1 to 3, characterized in that The material feeding screw rod further comprises a feeding section and a second threaded section between the feeding section and the first threaded section, and the second threaded section is provided with a secondary thread between the threads.

5. An injection molding screw as defined in any one of claims 1 to 3, characterized in that The material feeding screw rod is externally provided with a barrel, and the inner diameter of the barrel matches the outer diameter of the material feeding screw rod and the outer diameters of the first material feeding wheel and the second material feeding wheel.

6. An injection molding screw as defined in claim 5 wherein, A plurality of groups of heaters are arranged on the outside of the barrel corresponding to different threaded sections of the material feeding screw rod, and the number of heaters in each group is not completely consistent.

7. An injection molding screw as defined in any one of claims 1 to 3, characterized in that The utility model further comprises a screw head fixedly connected to one end of the material feeding screw rod provided with the second material feeding wheel through a non-return ring, and the non-return ring is sleeved on the screw head rod part.

8. An injection molding screw as defined in claim 7 wherein, The screw head is connected with a nozzle through a connecting body, the connecting body is provided with a groove matched with the screw head and a connecting block for connecting the nozzle, and the connecting block is provided with a through hole gradually decreasing in hole diameter from the screw head to the nozzle.

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