A nozzle for foaming co-injection

Abstract

The present application relates to the technical field of polymer coinjection processing, and more particularly to a nozzle for foam coinjection, comprising a nozzle body, a valve core coaxially arranged and slidably mounted within the nozzle body, a barrel coupling sleeve fixedly connected to the nozzle body and used to introduce melt, and a nozzle head disposed at one end of the valve core away from the barrel coupling sleeve and used to extend into a mold gate; the barrel coupling sleeve has a feed port for melt entry, the nozzle head has a discharge port for injecting the melt, and the valve core has a central flow channel at its axial center for connecting the feed port and the discharge port. This application ensures that the product can maintain a stable skin-core-skin structure, thereby improving the quality of coinjection molding.

Description

Technical Field

[0001] The present application relates to the technical field of polymer co-injection processing, and in particular to a nozzle for foaming co-injection. Background Art

[0002] Existing polymer co-injection nozzles are specifically designed for co-injection molding processes, capable of injecting two or more different polymer melts simultaneously or sequentially into the mold's gate. To prevent the melts in the nozzle from pre-foaming due to pressure loss during injection, the nozzles are designed to open during injection and close afterward. However, these nozzles are complex in structure and cannot guarantee the layered injection of the different melts.

[0003] In related technologies, flow channel distribution issues can cause the core and skin layers to interpenetrate within the nozzle, making it impossible to maintain the desired skin-core-skin structure. To meet the desired skin-core-skin ratio for the finished part, it's sometimes necessary to increase the storage ratio of the skin material and reduce the amount of core material. Due to the skin-core-skin material flow sequence, it's often difficult to ensure that the skin material completely clears the core material during the material flow transition from skin to core and back again. This can result in residual core material being trapped in the skin, damaging the skin of the co-injected part and resulting in defective products.

[0004] To address these issues, existing coinjection nozzles require a large amount of skin material to completely remove the core material. Therefore, these nozzles are not suitable for forming coinjected parts with long flow ratios and a large core-to-skin ratio. To address these issues, improvements to the coinjection nozzle structure are needed to ensure a stable skin-core-skin structure in the finished part, thereby improving the quality of coinjection molding. Summary of the Invention

[0005] In order to ensure that the product can maintain a stable skin-core-skin structure and improve the quality of co-injection molding, the present application provides a nozzle for foaming co-injection.

[0006] The present application provides a nozzle for foaming co-injection using the following technical solution:

[0007] A nozzle for foaming co-injection, comprising a nozzle body, a valve core coaxially arranged and slidably mounted inside the nozzle body, a barrel coupling sleeve fixedly connected to the nozzle body and used to pass melt, and a nozzle head sleeved on an end of the valve core away from the barrel coupling sleeve and used to extend into a mold gate;

[0008] The barrel connecting sleeve has a feed port for the melt to enter, the nozzle head has a discharge port for extruding the melt, and the valve core has a central flow channel at the axial center position for connecting the feed port and the discharge port.

[0009] By adopting the above technical solution, the valve core and the nozzle body are installed in a coaxial sliding manner. The central flow channel set in the valve core connects to the discharge port at the front end and the feed port at the rear end, ensuring the smooth passage of the melt. By adjusting the sliding and switching timing of the valve core, the nozzle can be adapted to different injection molding requirements, including different skin and core layer ratios, and different melt characteristics. It also ensures that the different melts of the skin layer material and the core layer material can be injected in layers and sequentially during the injection process, reducing the residue of the core layer material in the skin layer, thereby maintaining the skin-core-skin structure required for the part. The structure of the nozzle is relatively complex, but it simplifies the operation process. The automated valve core sliding switching function reduces the need for manual intervention and improves production efficiency.

[0010] Furthermore, the valve core comprises a first valve section, a second valve section, and a third valve section which are coaxially arranged and fixedly connected in sequence;

[0011] The first valve section has a nozzle outlet channel for communicating with the discharge port;

[0012] The third valve section has a core layer central feed channel for communicating with the feed port, and an end of the third valve section close to the barrel connecting sleeve is provided with a limiting flange block on the outer peripheral wall for abutting against the end of the nozzle body;

[0013] The second valve section has a core layer small hole for connecting the core layer central feed channel and the nozzle outlet channel.

[0014] By adopting the above technical solution, the valve core is divided into the first valve section, the second valve section and the third valve section. The segmented design makes the flow path of the skin layer material and the core layer material in the nozzle more clear and controllable. The nozzle outlet channel of the first valve section is directly connected to the discharge port to ensure the smooth extrusion of the melt; the core layer center feed channel of the third valve section is connected to the feed port, providing a channel for the injection of the core layer material. The limit flange block set at one end of the third valve section near the barrel connecting sleeve plays the role of stabilizing the position of the valve core. During the operation of the nozzle, the limit flange block is tightly abutted against the end of the nozzle body to prevent the valve core from shifting or shaking under the action of the high-pressure melt. The core layer hole on the second valve section is the key channel connecting the core layer center feed channel and the nozzle outlet channel. It also provides a separate channel for the entry of the skin layer material, which can further control the wrapping effect of the skin layer material on the core layer material, ensuring that the core layer material is completely wrapped by the skin layer material during the extrusion process, forming a stable skin-core-skin structure. The small holes in the core layer help to adjust the flow rate and pressure of the melt, thereby optimizing the quality of co-injection molding, achieving precise stratification of the skin and core layers, and avoiding mutual penetration of the melt in the nozzle.

[0015] Furthermore, the valve core is provided with a cortex inlet groove along the length direction of the outer wall, and the first valve section is provided with a cortex radial feed hole radially on the side wall, and the cortex radial feed hole is interconnected with the cortex inlet groove and the nozzle outlet channel.

[0016] By adopting this technical solution, when the nozzle body slides until the cortex inlet groove is connected to the feed port of the barrel coupling sleeve, it is equivalent to independently opening the feed flow channel for the cortex melt. The cortex melt enters the cortex inlet groove from the feed port and then enters the nozzle outlet channel through the cortex radial feed hole. The combination of the cortex inlet groove and the cortex radial feed hole allows the cortex material to flow along a specific path and be precisely introduced into the nozzle outlet channel, enhancing the nozzle's ability to control the cortex material, helping to form a more uniform and stable cortex structure, and optimizing the wrapping effect of the cortex on the core layer, thereby achieving a higher quality skin-core-skin structure.

[0017] Furthermore, the inner diameter of the core layer hole is smaller than the inner diameter of the core layer center feed channel and the nozzle outlet channel, the second valve section is radially provided with a core layer switch pin for controlling the opening and closing of the core layer hole at the center position, the second valve section is provided with an opening and closing slide groove for the core layer switch pin to be installed and slid, the nozzle body is provided with a guide ball socket groove on the inner wall that matches the end of the core layer switch pin, and the second valve section is radially provided with a throttling hole for communicating with the core layer hole on the opposite side of the opening and closing slide groove.

[0018] By adopting the above technical solution, the core layer switch pin achieves the effect of precisely controlling the opening and closing of the core layer orifice. When the nozzle body slides to the point where the core layer switch pin aligns with the guide ball socket groove on the inner wall of the nozzle body, the skin layer material enters the throttle hole through the skin layer inlet groove and forms fluid pressure, forcing the core layer switch pin to overcome friction and enter the guide ball socket groove through the opening and closing slide groove. The skin layer orifice is opened and connects the core layer center feed channel with the nozzle outlet channel. The core material melt enters the core layer center feed channel through the feed inlet and then enters the nozzle outlet channel through the core layer orifice. At this time, the skin layer melt flow channel and the core layer melt flow channel are opened simultaneously, thus forming a stable skin-core-skin structure.

[0019] Furthermore, the outer wall of the nozzle head is provided with a front end convex step, the outer wall of the nozzle body is provided with a rear end convex step, the nozzle head and the nozzle body are externally sleeved with a pressure spring, and the pressure spring abuts between the front end convex step and the rear end convex step.

[0020] With this technical solution, once the nozzle tip is inserted into the mold gate, pressure causes the valve core to slide within the nozzle body, sequentially opening the skin and core channels. A pressure spring provides rebound force for the nozzle tip and valve core. During injection, after the melt is extruded through the nozzle tip, the pressure spring automatically returns the nozzle tip and valve core to their initial positions using its own elastic force. This automatic reset function ensures nozzle stability and reliability during continuous injection, reducing errors and downtime caused by manual resets.

[0021] Furthermore, the number of the cortex inlet grooves and the cortex radial feed holes are both multiple and arranged in one-to-one correspondence, each of the cortex inlet grooves is circumferentially arranged on the outer wall of the valve core, and each of the cortex radial feed holes is circumferentially arranged on the first valve section.

[0022] By adopting this technical solution, the provision of multiple skin inlet grooves and radial skin feed holes ensures that the skin material is evenly distributed within the valve core and nozzle, helping to form a more uniform and stable skin structure during the injection process, thereby improving part quality. Due to the increased number of skin inlet grooves and radial skin feed holes, the skin material can more fully envelop the core material. This enhanced envelopment helps reduce exposure and leakage of the core material, resulting in a more complete skin-core-skin structure.

[0023] Furthermore, the limiting flange block is provided with an inclined abutting sealing surface on a side close to the nozzle body, and the end of the nozzle body is provided with an abutting sealing surface that matches the inclined abutting sealing surface.

[0024] By adopting the above technical solution, the coordination of the inclined sealing abutment surface and the abutment sealing surface improves the reliability of the valve core closing. When the valve core moves forward into the nozzle body under the action of the spring force and slides to the predetermined position, the inclined abutment sealing surface and the abutment sealing surface closely contact each other, ensuring that the valve core can be accurately positioned in the required position and seal the skin inlet, ensuring the sealing of the nozzle closure.

[0025] Furthermore, the diameter of the nozzle head gradually decreases at an end away from the nozzle body.

[0026] By adopting this technical solution, the gradual reduction in nozzle tip diameter helps optimize melt flow and reduce melt retention within the nozzle tip. During the injection molding process, the melt is subjected to higher shear rates and injection pressures as it exits the nozzle tip due to the smaller diameter at the tip end. This results in smoother and more stable flow, helping to improve melt filling efficiency and part quality. After injection molding, the smaller diameter at the tip end makes it easier for the melt to be fully extruded, reducing melt retention and solidification within the nozzle tip.

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

[0028] Through the segmented design of the valve core and the coordination of the core layer hole, the skin layer inlet groove and the skin layer radial feed hole, the skin layer material and the core layer material are accurately layered and injected sequentially in the nozzle. The core layer hole, the skin layer inlet groove and the skin layer radial feed hole optimize the flow path of the melt, so that the skin layer material can be evenly distributed in the nozzle, forming a stable skin structure, ensuring that the core layer material is completely wrapped by the skin layer material. The core layer switch pin accurately controls the entry of the core material, further enhancing the wrapping effect of the skin layer on the core layer, avoiding mutual penetration of the melt in the nozzle, and thus obtaining a high-quality skin-core-skin structure;

[0029] The pressure spring between the nozzle head and the nozzle body provides rebound force for the nozzle head and valve core, realizing the automatic reset function of the valve core, reducing the need for manual intervention and improving production efficiency;

[0030] The cooperation between the inclined abutting sealing surface and the abutting sealing surface makes the sliding process of the valve core in the nozzle body smoother and more stable, ensuring that the valve core can be accurately positioned at the required position, thereby improving the stability and accuracy of injection molding. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the overall structure of a nozzle used for foaming co-injection in an embodiment of the present application.

[0032] Figure 2 This is a schematic diagram of the structural decomposition of a nozzle used for foaming co-injection in an embodiment of the present application.

[0033] Figure 3 It is a schematic cross-sectional view of the nozzle in a fully closed state in an embodiment of the present application.

[0034] Figure 4 It is a schematic cross-sectional structural diagram of the nozzle in an embodiment of the present application in a state where only the cortical flow channel is open.

[0035] Figure 5 It is a schematic cross-sectional structural diagram of the nozzle in an embodiment of the present application in a state where the skin layer flow channel and the core layer flow channel are simultaneously open.

[0036] Explanation of the accompanying symbols: 1. Nozzle body; 11. Rear end convex step; 12. Abutment sealing surface; 13. Guide ball socket groove; 2. Nozzle head; 21. Front end convex step; 22. Discharge port; 3. Barrel connecting sleeve; 31. Feed port; 4. Valve core; 41. First valve section; 411. Nozzle outlet channel; 412. Cortex radial feed hole; 42. Second valve section; 421. Core layer small hole; 422. Core layer switch pin; 4221. Opening and closing slide groove; 423. Throttle hole; 43. Third valve section; 431. Limiting flange; 4311. Inclined abutment sealing surface; 432. Core layer center feed channel; 44. Cortex inlet groove; 5. Pressure spring. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of this application more clear, the following Figure 1-5 And embodiments, the present application is further described in detail.

[0038] The present application embodiment discloses a nozzle for foaming co-injection. Figure 1 and Figure 2 The spring nozzle for foaming co-injection includes a nozzle body 1, a nozzle head 2, a barrel connecting sleeve 3, a valve core 4 and a pressure spring 5.

[0039] The valve core 4 is coaxially penetrated and slidably installed inside the nozzle body 1. The barrel connecting sleeve is fixedly connected to one end of the nozzle body 1 and is used to pass the melt. The nozzle head 2 is sleeved and fixedly connected to the end of the valve core 4 away from the barrel connecting sleeve 3. The diameter of the nozzle head 2 away from the nozzle body 1 gradually decreases to match the mold gate diameter.

[0040] The outer wall of the nozzle tip 2 is integrally connected to a front convex step 21, while the outer wall of the nozzle body 1 is integrally connected to a rear convex step 11. A pressure spring 5 is sleeved around the exterior of the nozzle tip 2 and nozzle body 1, with the ends of the pressure spring 5 abutting the opposing sides of the front convex step 21 and rear convex step 11. When the nozzle tip 2 is driven by the mold shifter to extend into contact with the mold sprue bushing, the shifting force overcomes the elastic force of the pressure spring 5, causing the valve core 4 to slide within the nozzle body 1. The pressure spring 5 provides a rebound force for the nozzle tip 2 and valve core 4, thereby resetting the nozzle tip 2 and valve core 4.

[0041] Combine Figure 3 The barrel connecting sleeve 3 has a feed port 31 for the melt to enter at the axial center position, the nozzle head 2 has a discharge port 22 for injecting the melt at the axial center position, and the valve core 4 has a central and peripheral flow channel for connecting the feed port 31 and the discharge port 22 at the axial center position, thereby ensuring smooth passage of the melt.

[0042] In this embodiment, the valve core 4 includes a first valve section 41, a second valve section 42, and a third valve section 43, which are coaxially arranged and integrally connected in sequence. The third valve section 43 is located on the side proximal to the barrel coupling sleeve 3. A limiting flange 431 is integrally connected to the outer peripheral wall of the end of the third valve section 43 proximal to the barrel coupling sleeve, which is configured to abut the end of the nozzle body 1. The limiting flange 431 is provided with an inclined abutting sealing surface 4311 on the side proximal to the nozzle body 1. The end of the nozzle body 1 is provided with an abutting sealing surface 12 that mates with the inclined abutting sealing surface 4311. When the valve core 4 moves into the interior of the nozzle body 1 under pressure and slides to a predetermined position, the inclined abutting sealing surface 4311 abuts the abutting sealing surface 12, ensuring that the valve core 4 is accurately positioned in the desired sealing position and that the nozzle is sealed when closed.

[0043] The first valve section 41 has a nozzle outlet channel 411 at the axial center for communicating with the discharge port 22. The third valve section 43 has a core layer central feed channel 432 at the axial center for communicating with the feed port 31. The second valve section 42 has a core layer aperture 421 for connecting the core layer central feed channel 432 with the nozzle outlet channel 411. The diameter of the core layer aperture 421 is smaller than the diameters of the core layer central feed channel 432 and the nozzle outlet channel 411. The nozzle outlet channel 411, the core layer aperture 421, and the core layer central feed channel 432 together form a complete central flow channel.

[0044] The valve core 4 has multiple skin inlet grooves 44 defined along its length on its outer wall. A radial skin feed hole 412 is defined radially along the sidewall of the first valve section 41. This radial skin feed hole 412 is located near the second valve section 42 in the first valve section 41 and communicates with both the skin inlet grooves 44 and the nozzle outlet channel 411. A core switch pin 422 is radially defined at the center of the second valve section 42. This second valve section 42 also includes an opening and closing chute 4221 for mounting and sliding the core switch pin 422. The nozzle body 1 has a guide ball socket 13 defined on its inner wall for the end of the core switch pin 422 to engage. The core layer switch pin 422 can be used to control the opening and closing of the core layer hole 421. When the nozzle does not inject the melt into the mold gate and the core layer is closed, the core layer switch pin 422 leaves the guide ball socket 13 and is completely confined in the opening and closing slide groove 4221. The core layer hole 421 is blocked by the core layer switch pin 422 to prevent the core layer melt from passing through.

[0045] Reference Figure 3 and Figure 4When the nozzle body 1 slides to the cortex inlet groove 44 and is connected to the feed port 31 of the barrel connecting sleeve 3, and the core layer switch pin 422 is not in the guide ball socket groove 13, it is equivalent to opening the feed flow channel of the leather melt alone. The leather melt enters the cortex inlet groove 44 from the feed port 31, and then enters the nozzle outlet channel 411 from the cortex radial feed hole 412. At this time, the parts extruded from the nozzle outlet channel 411 are all composed of cortex material.

[0046] Reference Figure 3 and Figure 5 , the second valve section 42 is radially provided with a throttle hole 423 for communicating with the core layer small hole 421 on the opposite side of the opening and closing slide groove 4221. When the nozzle body 1 slides to the guide ball socket groove 13 on the inner wall of the nozzle body 1 where the core layer switch pin 422 is aligned, the skin layer material enters the throttle hole 423 from the skin layer inlet groove 44 and forms fluid pressure, forcing the core layer switch pin 422 to overcome the friction force and enter the guide ball socket groove 13 from the opening and closing slide groove 4221, so that the skin layer small mouth is opened and connects the core layer center feed channel 432 and the nozzle outlet channel 411, the core material melt enters the core layer center feed channel 432 from the feed port 31, and then enters the nozzle outlet channel 411 through the core layer small hole 421. At this time, the skin layer melt flow channel and the core layer melt flow channel are opened at the same time, and the melt injected from the nozzle outlet channel 411 is a stable skin-core structure. When extrusion needs to be stopped, the nozzle body 1 gradually moves away from the mold gate, and the nozzle returns to Figure 4 state, at this time, the melt injected from the nozzle outlet channel 411 is composed of skin material.

[0047] The operating principle of a nozzle for foaming co-injection according to an embodiment of the present application is as follows: the skin and core flow channels are separated at the feed inlet 31 of the barrel connector. The skin material enters the nozzle outlet channel 411 through the skin inlet groove 44 on the outer periphery of the valve core 4, meaning the skin channel opens first while the core channel remains closed. When the skin channel fully opens and begins to flow into the nozzle outlet channel 411, building up melt pressure, this pressure acts on the bottom of the switch pin through the orifice 423, forcing the core switch pin 422 to the open position, overcoming the friction caused by the pin's displacement, thereby opening the core flow channel. The subsequent nozzle flow field maintains the simultaneous opening of the skin and core channels. The skin material enters from the outer periphery of the nozzle outlet channel 411, forming the outer layer of the nozzle outlet channel 411 flow field. The core material, however, must enter the nozzle outlet channel 411 through the intermediate core layer aperture 421, which is much smaller than the nozzle outlet channel 411 aperture. Consequently, it is enveloped by the outer skin layer, forming a sandwich structure. The core material then flows through this flow field to the mold gate. This ensures to the greatest extent possible that the core material will not penetrate the skin layer prematurely and destroy the co-injected skin-core-skin structure.

[0048] The pressure drop gradient between the core layer's central feed channel 432 and the core layer's small holes 421 maximizes the pressure drop gradient of the core layer through the core layer's small holes 421, thereby increasing the cell nucleation rate and increasing the number of cell nucleation points to form a microbubble structure in the core layer. Ultimately, a smooth, skin-covered microbubble core sandwich microbubble product is achieved, which is another feature and advantage of the present application. This eliminates surface finish defects in the microbubble product.

[0049] When the nozzle is closed, the core layer switch pin 422 reaches the closed position first, while the skin layer inlet remains partially open. This ensures that the nozzle outlet channel 411 will not have more core layer than skin layer when the nozzle is closed. This ensures that when the next cycle begins at the same time, the skin layer is still the main layer, enveloping any core layer material that may remain in the center layer. The opening and closing of the nozzle is achieved entirely by the mechanical movement of the valve core 4 and the core layer switch pin 422 caused by the forward and backward movement of the nozzle head 2. The opening of the core layer switch pin 422 is achieved through the combined action of mechanical movement and skin layer melt pressure, ensuring timely opening. The closing of the core layer switch pin 422 is completely forced by mechanical movement, mainly due to the reset of the pressure spring 5, which forces the nozzle valve core 4 to move, driving the core layer switch pin 422 back to the closed position.

[0050] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A nozzle for foaming co-injection, characterized by: It comprises a nozzle body (1), a valve core (4) coaxially arranged and slidably mounted inside the nozzle body (1), a barrel connecting sleeve (3) fixedly connected to the nozzle body (1) and used for passing melt, and a nozzle head (2) arranged at one end of the valve core (4) away from the barrel connecting sleeve (3) and used for extending into the mold gate; The barrel connecting sleeve has a feed port (31) for the melt to enter, the nozzle head (2) has a discharge port (22) for injecting the melt, and the valve core (4) has a central flow channel at the axial center position for connecting the feed port (31) and the discharge port (22); The valve core (4) comprises a first valve section (41), a second valve section (42), and a third valve section (43) which are coaxially arranged and fixedly connected in sequence; The first valve section (41) has a nozzle outlet channel (411) for communicating with the discharge port (22); The third valve section (43) has a core layer central feed channel (432) for communicating with the feed port (31); an end of the third valve section (43) close to the barrel connecting sleeve is provided with a limiting flange (431) on the outer peripheral wall for abutting and sealing against the end of the nozzle body (1); The second valve section (42) has a core layer small hole (421) for connecting the core layer central feed channel (432) and the nozzle outlet channel (411); The valve core (4) is provided with a cortex inlet groove (44) along the length direction on the outer wall, and the first valve section (41) is provided with a cortex radial feed hole (412) in the radial direction of the side wall, and the cortex radial feed hole (412) is communicated with the cortex inlet groove (44) and the nozzle outlet channel (411); The inner diameter of the core layer hole (421) is smaller than the inner diameter of the core layer central feed channel (432) and the nozzle outlet channel (411); the second valve section (42) is radially provided with a core layer switch pin (422) at the center position for controlling the opening and closing of the core layer hole (421); the second valve section (42) is provided with an opening and closing slide groove (4221) for the core layer switch pin (422) to be installed and slid; the nozzle body (1) is provided with a guide ball socket groove (13) on the inner wall thereof for matching with the end of the core layer switch pin (422); the second valve section (42) is radially provided with a throttling hole (423) for communicating with the core layer hole (421) on the opposite side of the opening and closing slide groove (4221).

2. The nozzle for foaming co-injection according to claim 1, characterized in that: The outer peripheral wall of the nozzle head (2) is provided with a front end convex step (21), and the outer peripheral wall of the nozzle body (1) is provided with a rear end convex step (11). The nozzle head (2) and the nozzle body (1) are externally sleeved with a pressure spring (5), and the pressure spring (5) is in contact between the front end convex step (21) and the rear end convex step (11).

3. The nozzle for foaming co-injection according to claim 1, characterized in that: The number of the cortex inlet grooves (44) and the cortex radial feed holes (412) are both multiple and arranged in a one-to-one correspondence. Each of the cortex inlet grooves (44) is circumferentially arranged on the outer wall of the valve core (4), and each of the cortex radial feed holes (412) is circumferentially arranged on the first valve section (41).

4. The nozzle for foaming co-injection according to claim 1, characterized in that: The limiting flange (431) is provided with an inclined abutting sealing surface (4311) on a side close to the nozzle body (1), and the end of the nozzle body (1) is provided with an abutting sealing surface (12) that matches the inclined abutting sealing surface (4311).

5. The nozzle for foaming co-injection according to claim 1, characterized in that: The diameter of the nozzle head (2) gradually decreases at one end away from the nozzle body (1).

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