Pre-plasticizing mechanism with pressure maintaining function and injection molding machine

Abstract

This invention relates to the field of injection molding technology, specifically to a pre-plasticizing mechanism and injection molding machine with a pressure-holding function. The mechanism includes an injection molding machine frame, an injection head, a rotary valve, and a reverse-push assembly. By installing a rotary valve within the injection pipe, the pipe cavity is divided into an injection cavity and a feeding cavity. A pressure-driven assembly senses pressure changes in the feeding cavity; when the pressure exceeds a threshold, it automatically drives the rotary valve core to rotate, connecting the fixed valve channel with the rotary valve channel, thus achieving controllable flow of the melt. Simultaneously, a reverse-push assembly is provided, which, when the screw pusher resets, drives the rotary valve, which is in a closed state, to move towards the injection cavity, compressing the melt within. This actively applies pressure to the cavity after the screw retracts, solving the problems of melt backflow and the inability to actively apply pressure in existing pre-plasticizing mechanisms, which lead to quality defects such as shrinkage cavities and dents in the product.

Description

Technical Field

[0001] This invention relates to the field of injection molding technology, specifically to a pre-plasticizing mechanism and injection molding machine with a pressure-holding function. Background Technology

[0002] In injection molding, the pre-plasticizing mechanism melts solid plastic granules and delivers them to the front end of the injection pipe. Once the melt reaches the preset amount, the screw pushes the melt into the mold cavity, completing the product molding. To ensure the density and dimensional stability of the product, the injection molding process usually needs to enter a holding pressure stage after injection to compensate for the volume loss caused by the cooling and shrinkage of the melt.

[0003] However, existing pre-plasticizing mechanisms have significant drawbacks in practical applications. Because injection molding machines require a certain margin in their injection action, typically only about 98% of the melt is injected into the mold cavity before the screw stops rotating and retracts. During screw retraction, residual melt in the nozzle easily flows back into the feeding chamber under pressure differential, rather than continuing to enter the mold cavity to fill shrinkage space. Even if some melt manages to flow into the mold cavity, its flow rate and pressure are difficult to control, failing to create a stable and effective pressure-holding effect. This leads to quality defects such as shrinkage cavities and dents inside the product, and also prolongs the molding cycle and reduces process stability.

[0004] To address the aforementioned issues, existing technologies have incorporated check valves within the nozzle to prevent melt backflow via a one-way valve. However, these solutions generally suffer from the following drawbacks: the opening and closing of the check valve depends on the melt flow direction, resulting in a delayed response and an inability to actively apply pressure to the cavity after the screw retracts; the axial movement of the valve core alters the valve cavity volume, causing pressure fluctuations; and the check valve structures are mostly ball or cone valves, offering limited sealing reliability and failing to meet the high requirements of precision injection molding.

[0005] Therefore, developing a pre-plasticizing mechanism that can automatically close the flow channel and prevent backflow after the screw retracts, and can actively apply pressure to the cavity, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the problems existing in the prior art, a pre-plasticizing mechanism and injection molding machine with pressure-holding function are provided. By installing a rotary valve in the injection pipe, the inner cavity of the pipe is divided into an injection cavity and a feeding cavity. A pressure-driven component senses the pressure change in the feeding cavity. When the pressure exceeds a threshold, it automatically drives the rotary valve core to rotate, connecting the fixed valve channel and the rotary valve channel, thus achieving controllable on / off of the melt. At the same time, a reverse-push component is provided. When the screw pusher is reset, it drives the screw pusher and the rotary valve to move towards the injection cavity, squeezing the melt in the injection cavity. Thus, after the screw retracts, it actively applies pressure to the cavity, solving the problems of melt backflow and inability to actively apply pressure in the existing pre-plasticizing mechanism, which leads to quality defects such as shrinkage cavities and dents in the product.

[0007] To address the problems of existing technologies, this invention provides a pre-plasticizing mechanism with a pressure-holding function, comprising: an injection molding frame with an injection pipe on one side and a push cylinder on the other side; a sliding frame inside the injection molding frame, the sliding frame being connected to the output rod of the push cylinder; a motor mounted on the sliding frame; a helical push rod inside the injection pipe, the helical push rod being drively connected to the output shaft of the motor; an injection head located at the outlet of the injection pipe; and a rotary valve slidably disposed within the injection pipe along its axial direction, dividing the inner cavity of the injection pipe into an injection cavity communicating with the mold cavity and a feeding cavity communicating with the space where the helical push rod is located; the rotary valve... The rotary valve includes a fixed valve core and a rotary valve core arranged coaxially, and a pressure drive assembly for driving the rotary valve core to rotate relative to the fixed valve core; the fixed valve core has a fixed valve channel, and the rotary valve core has a rotary valve channel that can selectively communicate with the fixed valve channel; when the pressure of the feeding chamber on the pressure drive assembly is greater than a preset threshold, the pressure drive assembly drives the rotary valve core to rotate, so that the rotary valve channel communicates with the fixed valve channel; a reverse push assembly is disposed in the injection pipe and is connected to the helical push rod and the rotary valve for driving the rotary valve, which is in the closed state, to squeeze the injection cavity when the helical push rod is reset.

[0008] Preferably, the rotary valve further includes a sliding cylinder, which is coaxially and slidably disposed within the injection pipe; the fixed valve core is coaxially disposed at one end of the sliding cylinder facing the injection cavity; and the rotary valve core is rotatably disposed within the sliding cylinder and abuts against the side of the fixed valve core facing the feeding cavity.

[0009] Preferably, a driven cylinder is provided at one end of the rotary valve core facing the feeding chamber, and a mounting cavity is formed between the inner circumference of the sliding cylinder and the outer circumference of the driven cylinder. An arc-shaped groove is provided on the outer circumference of the driven cylinder. The pressure drive assembly includes: a pressure ring, which is coaxially and slidably disposed in the mounting cavity and splinedly connected to the inner circumference of the sliding cylinder, and a drive block that slides with the arc-shaped groove is provided on the inner circumference of the pressure ring; and an elastic element, which is disposed in the mounting cavity and abuts against the pressure ring.

[0010] Preferably, a limiting boss is provided at one end of the outer periphery of the driven cylinder facing the feeding chamber, and the pressure ring elastically abuts against one end of the limiting boss.

[0011] Preferably, one end of the rotary valve core is provided with a connecting shaft, the connecting shaft passes through the fixed valve core and is rotatably connected to it, and a retaining ring is provided at one end of the connecting shaft extending to the injection cavity.

[0012] Preferably, the injection molding pipe has an outer chamber and an inner chamber coaxially arranged inside the opening, and a connecting hole is provided between the outer chamber and the inner chamber. The reverse pushing assembly includes: an inner push cylinder, one end of which is coaxially connected to the rotary valve, and the other end of which extends into the inner chamber and forms an inner piston end. The outer periphery of the inner push cylinder and the inner wall of the inner chamber form an inner pressure chamber, which communicates with the connecting hole; and an outer push cylinder, one end of which is connected to the head of the helical push rod, and the other end of which extends into the outer chamber and forms an outer piston end. The outer piston end and the inner wall of the outer chamber form an outer pressure chamber, which communicates with the connecting hole. Hydraulic oil is injected into the inner pressure chamber and the outer pressure chamber.

[0013] Preferably, the reverse pushing assembly further includes a connecting rod that passes radially through the head of the helical push rod, and the two ends of the connecting rod are fixedly connected to the outer push cylinder.

[0014] Preferably, the inner circumference of the injection-molded pipe is provided with a limiting groove extending along its axial direction, and the outer side of the rotary valve is provided with a limiting block, which extends into the limiting groove and slides therewith.

[0015] Preferably, the reverse pushing assembly further includes: a fixed cylinder, coaxially disposed within the injection pipe; a partition cylinder, coaxially disposed within the fixed cylinder, wherein the outer periphery of the partition cylinder and the inner periphery of the fixed cylinder form the outer cavity, a positioning cylinder is disposed at one end of the partition cylinder facing the feeding chamber, wherein the outer periphery of the positioning cylinder and the inner periphery of the partition cylinder form the inner cavity, and the connecting holes are axially distributed on the partition cylinder.

[0016] An injection molding machine with a pressure holding function includes a pre-plasticizing mechanism with a pressure holding function.

[0017] The advantages of this application compared to the prior art are:

[0018] This application utilizes a pressure-driven component to sense the pressure in the feeding chamber and automatically control the valve opening and closing, achieving precise switching between injection and pressure replenishment processes without the need for external control signals, ensuring timely and reliable response. The rotational engagement of the rotary and fixed valve channels eliminates the volume changes caused by the traditional axial valve core movement, avoiding pressure fluctuations. The valves provide a reliable seal after closure, effectively preventing melt backflow. The reverse-push component converts the resetting motion of the screw pusher into axial compression of the injection cavity by the rotary valve, actively applying pressure replenishment to the cavity after the flow channel closes, solving the problem that traditional mechanisms cannot actively replenish pressure after the screw retraction. This mechanism integrates injection, check valve, and pressure replenishment functions into a compact structure, suitable for precision injection molding, significantly reducing defects such as shrinkage cavities and dents in products, and improving product quality and process stability. Attached Figure Description

[0019] Figure 1 This is a perspective view of a pre-plasticizing mechanism with a pressure-holding function according to the present invention;

[0020] Figure 2 This is a three-dimensional sectional view of a pre-plasticizing mechanism with a pressure-holding function according to the present invention;

[0021] Figure 3 This is a cross-sectional view of a rotary valve and a reverse push assembly in a pre-plasticizing mechanism with a pressure-holding function according to the present invention.

[0022] Figure 4 yes Figure 3 A magnified view of part A;

[0023] Figure 5 yes Figure 3 A magnified view of section B;

[0024] Figure 6 This is an exploded perspective view of the driven cylinder and the outer push cylinder in a pre-plasticizing mechanism with a pressure-holding function according to the present invention.

[0025] Figure 7 This is an exploded perspective view of a rotary valve component in a pre-plasticizing mechanism with a pressure-holding function according to the present invention, viewed from a first perspective.

[0026] Figure 8 yes Figure 7 A magnified view of a portion at point C;

[0027] Figure 9 This is an exploded perspective view of a rotary valve component in a pre-plasticizing mechanism with a pressure-holding function according to the present invention, viewed from a second perspective.

[0028] Figure 10 yes Figure 9A magnified view of a portion of point D.

[0029] The diagram is labeled as follows: 1. Injection molding machine frame; 11. Injection pipe; 111. Limiting groove; 12. Push cylinder; 13. Sliding frame; 14. Motor; 15. Spiral push rod; 2. Injection head; 31. Injection cavity; 32. Feeding cavity; 33. Fixed valve core; 331. Fixed valve passage; 34. Rotary valve core; 341. Rotary valve passage; 342. Driven cylinder; 3421. Arc groove; 3422. Limiting boss; 343 344. Connecting shaft; 35. Snap ring; 36. Pressure drive assembly; 37. Pressure ring; 38. Drive block; 39. Elastic element; 30. Sliding cylinder; 31. Limiting block; 42. Reverse push assembly; 43. Inner push cylinder; 44. Inner pressure chamber; 45. Outer push cylinder; 46. Outer pressure chamber; 47. Connecting rod; 48. Fixing cylinder; 49. Separating cylinder; 40. Connecting hole; 41. Positioning cylinder. Detailed Implementation

[0030] To further understand the features, technical means, and specific objectives and functions achieved by the present invention, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0031] like Figures 1 to 2 As shown, a pre-plasticizing mechanism with a pressure-holding function includes: an injection molding machine frame 1, with an injection pipe 11 on one side and a push cylinder 12 on the other side; a sliding frame 13 is also provided inside the injection molding machine frame 1, the sliding frame 13 is connected to the output rod of the push cylinder 12, a motor 14 is provided on the sliding frame 13, a spiral push rod 15 is provided inside the injection pipe 11, and the spiral push rod 15 is drively connected to the output shaft of the motor 14; an injection head 2 is provided at the outlet of the injection pipe 11; a rotary valve is slidably provided inside the injection pipe 11 along the axial direction, and divides the inner cavity of the injection pipe 11 into an injection cavity 31 communicating with the mold cavity and a feeding cavity 32 communicating with the space where the spiral push rod 15 is located; the rotary valve includes a coaxially mounted... The system includes a fixed valve core 33 and a rotary valve core 34, and a pressure drive assembly 35 for driving the rotary valve core 34 to rotate relative to the fixed valve core 33. The fixed valve core 33 has a fixed valve channel 331, and the rotary valve core 34 has a rotary valve channel 341 that can selectively communicate with the fixed valve channel 331. When the pressure of the feeding chamber 32 on the pressure drive assembly 35 is greater than a preset threshold, the pressure drive assembly 35 drives the rotary valve core 34 to rotate, so that the rotary valve channel 341 communicates with the fixed valve channel 331. A reverse push assembly 4 is disposed in the injection pipe 11 and is connected to the spiral push rod 15 and the rotary valve component for driving the rotary valve component, which is in the closed state, to squeeze the injection cavity 31 when the spiral push rod 15 is reset.

[0032] During operation, the screw pusher 15 rotates under the drive of the motor 14, conveying molten plastic from the feeding chamber 32 to the injection chamber 31. Initially, the rotary valve channel 341 and the fixed valve channel 331 are misaligned, and the flow channel is closed. When the melt pressure in the feeding chamber 32 gradually increases with the screw conveying and exceeds a preset threshold, the pressure drive component 35 senses the pressure change and drives the rotary valve core 34 to rotate, causing the rotary valve channel 341 to overlap and connect with the fixed valve channel 331. The melt enters the injection chamber 31 through the overlapped valve channel and is injected into the mold cavity via the injection head 2, completing the injection action.

[0033] After injection, the spiral pusher 15 stops rotating and begins its reverse reset. At this time, the pressure in the feeding chamber 32 drops rapidly, the pressure drive assembly 35 resets, and drives the rotary valve core 34 to rotate in the reverse direction, causing the rotary valve channel 341 to re-align and close with the fixed valve channel 331, cutting off the channel between the feeding chamber 32 and the injection chamber 31 and preventing melt backflow. Simultaneously, the reset action of the spiral pusher 15 drives the rotary valve assembly 4 to slide axially towards the injection chamber 31. Since the valve channel is closed, the movement of the rotary valve directly compresses the melt within the injection chamber 31, applying additional pressure to the cavity and filling the volume gap caused by melt cooling and shrinkage. After pressure replenishment, the rotary valve resets in subsequent injection cycles.

[0034] like Figure 3 , Figure 6 , Figure 7 and Figure 9 As shown, the rotary valve also includes a sliding cylinder 36, which is coaxially and slidably disposed within the injection pipe 11; a fixed valve core 33 is coaxially disposed at one end of the sliding cylinder 36 facing the injection cavity 31; and a rotary valve core 34 is rotatably disposed within the sliding cylinder 36 and abuts against the side of the fixed valve core 33 facing the feeding cavity 32.

[0035] Driven by the reverse pushing component 4, the sliding cylinder 36 slides axially along the injection molding pipe 11, causing the fixed valve core 33 and the rotary valve core 34 to move as a whole. When the rotary valve core 34 rotates relative to the fixed valve core 33 under the drive of the pressure driving component 35, the mating surfaces between the two remain in close contact, ensuring the reliability of valve opening and closing. The outer wall of the sliding cylinder 36 slides in contact with the inner wall of the injection molding pipe 11, guiding and sealing the valve core assembly to prevent melt leakage from the outer periphery of the valve core assembly.

[0036] The sliding cylinder 36 integrates the fixed valve core 33 and the rotary valve core 34 into a single module, facilitating assembly and disassembly and reducing manufacturing and maintenance difficulties. The sliding fit between the sliding cylinder 36 and the injection molding pipe 11 provides precise axial guidance for the valve core assembly, ensuring the rotary valve maintains coaxiality during axial movement and preventing jamming or sealing failure due to misalignment. The rotary valve core 34 abuts against the end face of the fixed valve core 33, with uniform force on the mating surfaces. It can automatically tighten under melt pressure, achieving pressure-assisted sealing; the higher the pressure, the more reliable the seal.

[0037] like Figure 8 and Figure 10 As shown, a driven cylinder 342 is provided at one end of the rotary valve core 34 facing the feeding chamber 32. A mounting cavity is formed between the inner circumference of the sliding cylinder 36 and the outer circumference of the driven cylinder 342. An arc-shaped groove 3421 is provided on the outer circumference of the driven cylinder 342. The pressure drive assembly 35 includes: a pressure ring 351, which is coaxially and slidably disposed in the mounting cavity and splinedly connected to the inner circumference of the sliding cylinder 36. A drive block 3511 that slides with the arc-shaped groove 3421 is provided on the inner circumference of the pressure ring 351; and an elastic element 352, which is disposed in the mounting cavity and abuts against the pressure ring 351.

[0038] The melt pressure in the feeding chamber 32 acts on the end face of the pressure ring 351 facing the feeding chamber 32. When the melt pressure increases, it pushes the pressure ring 351 to slide towards the injection cavity 31 against the elastic force of the elastic element 352. When the pressure ring 351 slides, the driving block 3511 on its inner circumference slides along the arc groove 3421 on the outer circumference of the driven cylinder 342. Due to the guiding effect of the arc groove 3421, the axial movement of the driving block 3511 is converted into the circumferential rotation of the driven cylinder 342, thereby driving the rotary valve core 34 to rotate relative to the fixed valve core 33. When the melt pressure decreases, the elastic element 352 pushes the pressure ring 351 to slide in the opposite direction, driving the rotary valve core 34 to rotate in the opposite direction and reset. By selecting elastic elements 352 with different elastic coefficients or adjusting the pre-compression amount of the elastic element 352, the action threshold of the pressure drive assembly 35 can be set.

[0039] The spline connection between the pressure ring 351 and the sliding cylinder 36 ensures that the pressure ring 351 only moves axially and does not rotate, making the coordinated movement of the drive block 3511 and the arc groove 3421 precisely controllable. The arc groove 3421 directly converts the axial displacement of the pressure ring 351 into the rotation angle of the rotary valve core 34, resulting in a short transmission path and fast response speed. The elastic force of the elastic element 352 can be preset. By selecting springs of different stiffness or adjusting the pre-compression amount, the pressure threshold for valve core opening can be flexibly set to adapt to different plastic melt characteristics and injection molding process requirements.

[0040] like Figure 4As shown, a limiting boss 3422 is provided at one end of the outer periphery of the driven cylinder 342 facing the feeding chamber 32, and the pressure ring 351 elastically abuts against one end of the limiting boss 3422.

[0041] In the initial state, the elastic element 352 pushes the pressure ring 351 against the limiting boss 3422, placing the pressure ring 351 in its initial position. At this time, the rotary valve channel 341 and the fixed valve channel 331 are in a misaligned closed state. When the pressure in the feeding chamber 32 increases, pushing the pressure ring 351 towards the injection cavity 31, the pressure ring 351 moves away from the limiting boss 3422, compressing the elastic element 352. Simultaneously, the rotation of the rotary valve core 34 is driven by the cooperation of the drive block 3511 and the arc groove 3421, opening the valve passage. When the pressure in the feeding chamber 32 decreases, the elastic element 352 pushes the pressure ring 351 to slide in the opposite direction until the pressure ring 351 re-aggregates against the limiting boss 3422. At this time, the rotary valve core 34 resets, and the valve passage closes. The limiting boss 3422 precisely limits the reset position of the pressure ring 351, ensuring that the rotary valve core 34 returns to the accurate initial position each time it closes.

[0042] like Figure 8 As shown, a connecting shaft 343 is provided at one end of the rotary valve core 34. The connecting shaft 343 passes through the fixed valve core 33 and is rotatably connected to it. A retaining ring 344 is provided at one end of the connecting shaft 343 extending to the injection cavity 31.

[0043] When the rotary valve core 34 rotates relative to the fixed valve core 33 under the drive of the pressure drive assembly 35, the connecting shaft 343 rotates within the central hole of the fixed valve core 33, providing radial support and rotational guidance for the rotary valve core 34. The retaining ring 344 abuts against the end face of the fixed valve core 33, restricting the axial displacement of the rotary valve core 34 toward the injection cavity 31; at the same time, the end of the rotary valve core 34 facing the feeding cavity 32 is kept pressed under the action of the pressure drive assembly 35, forming a bidirectional axial positioning together with the retaining ring 344, so that the fit clearance between the rotary valve core 34 and the fixed valve core 33 remains constant.

[0044] The rotational engagement between the connecting shaft 343 and the fixed valve core 33 provides a precise rotation center for the rotary valve core 34, ensuring that the rotary valve core 34 and the fixed valve core 33 always remain coaxial, avoiding valve channel misalignment or jamming due to skewness. The combined action of the retaining ring 344 and the axial force of the pressure drive assembly 35 achieves bidirectional axial positioning of the rotary valve core 34, preventing it from shifting during melt pressure fluctuations or mechanism movement, and ensuring the sealing reliability of the mating surfaces.

[0045] like Figure 4 and Figure 5As shown, the injection pipe 11 has an outer chamber and an inner chamber coaxially arranged inside the opening. A connection hole 451 is provided between the outer chamber and the inner chamber. The reverse push assembly 4 includes an inner push cylinder 41, one end of which is coaxially connected to the rotary valve, and the other end of which extends into the inner chamber and forms an inner piston end. The outer periphery of the inner push cylinder 41 and the inner wall of the inner chamber form an inner pressure chamber 411, which is connected to the connection hole 451. An outer push cylinder 42 has one end connected to the head of the spiral push rod 15, and the other end of which extends into the outer chamber and forms an outer piston end. The outer piston end and the inner wall of the outer chamber form an outer pressure chamber 421, which is connected to the connection hole 451. Hydraulic oil is injected into the inner pressure chamber 411 and the outer pressure chamber 421.

[0046] When the helical pusher 15 completes its injection action and begins its reverse reset, it drives the outer pusher cylinder 42 to move towards the outer chamber. The outer piston end compresses the hydraulic oil in the outer pressure chamber 421, increasing the hydraulic oil pressure. High-pressure hydraulic oil enters the inner pressure chamber 411 through the connecting hole 451, pushing the inner piston end to move the inner pusher cylinder 41 in the opposite direction, thereby driving the rotary valve to slide axially towards the injection cavity 31. Since the valve passage of the rotary valve is closed, its axial sliding directly compresses the melt in the injection cavity 31, applying additional pressure to the cavity. When the helical pusher 15 injects forward, the outer pusher cylinder 42 moves in reverse, the hydraulic oil flows back, and the inner pusher cylinder 41 and the rotary valve reset.

[0047] Using hydraulic oil as the transmission medium, the reverse linkage between the reset motion of the helical push rod 15 and the axial push of the rotary valve is achieved, resulting in smooth transmission without mechanical shock. Hydraulic transmission has excellent buffering and vibration absorption characteristics, absorbing speed fluctuations during the reset process of the helical push rod 15, making the pressure compensation action uniform and gentle. By selecting hydraulic oil of different viscosities or adjusting the orifice diameter of the connecting hole 451, the response speed and pressure of the pressure compensation action can be precisely controlled to adapt to different injection molding process requirements.

[0048] like Figure 3 As shown, the reverse pushing assembly 4 also includes a connecting rod 43 that passes radially through the head of the spiral push rod 15, and the two ends of the connecting rod 43 are fixedly connected to the outer push cylinder 42.

[0049] Driven by motor 14, the helical push rod 15 rotates, causing the connecting rod 43 and the outer push cylinder 42 to rotate synchronously. Since the outer piston end of the outer push cylinder 42 has a sliding fit with the inner wall of the outer cavity, and the outer pressure chamber 421 is filled with hydraulic oil, the rotational movement of the outer push cylinder 42 does not compress or suck the hydraulic oil in the outer pressure chamber 421; it only generates circumferential friction on the sliding contact surface with the inner wall of the outer cavity. The pressure in the outer pressure chamber 421 is determined solely by the axial displacement of the outer push cylinder 42 and is independent of its rotational movement.

[0050] The pressure within the external pressure chamber 421 is generated solely by axial displacement; rotational motion does not cause pressure fluctuations, ensuring the pressure control accuracy of the reverse-push assembly 4. The connecting rod 43 radially penetrates the head of the helical push rod 15, featuring a simple structure, ease of processing and assembly, and reliable connection.

[0051] like Figure 3 and Figure 7 As shown, the inner circumference of the injection pipe 11 is provided with a limiting groove 111 extending along its axial direction, and the outer side of the rotary valve is provided with a limiting block 361, which extends into the limiting groove 111 and slides therewith.

[0052] When the reverse-push assembly 4 drives the rotary valve to move axially along the injection molding pipe 11, the limiting block 361 slides synchronously within the limiting groove 111. The limiting groove 111 forms a circumferential constraint on the limiting block 361, restricting the circumferential rotation of the rotary valve within the injection molding pipe 11, allowing it to move only in a straight line along the axial direction. When the rotary valve core 34 rotates relative to the fixed valve core 33 under the drive of the pressure drive assembly 35, the sliding cylinder 36 is circumferentially locked through the cooperation of the limiting block 361 and the limiting groove 111. The sliding cylinder 36 and the fixed valve core 33 remain stationary, and only the rotary valve core 34 rotates, ensuring the accuracy of the valve opening and closing action.

[0053] like Figure 4 and Figure 5 As shown, the reverse pushing assembly 4 further includes: a fixed cylinder 44, coaxially disposed within the injection pipe 11; a partition cylinder 45, coaxially disposed within the fixed cylinder 44, wherein the outer periphery of the partition cylinder 45 and the inner periphery of the fixed cylinder 44 form the outer cavity, a positioning cylinder 452 is provided at one end of the partition cylinder 45 facing the feeding chamber 32, wherein the outer periphery of the positioning cylinder 452 and the inner periphery of the partition cylinder 45 form the inner cavity, and the connecting holes 451 are axially distributed on the partition cylinder 45.

[0054] The fixed cylinder 44 provides precise radial positioning for the partition cylinder 45, ensuring that the outer chamber and the inner chamber are coaxial. The partition cylinder 45 and the positioning cylinder 452 together form the boundary between the inner and outer chambers. The outer push cylinder 42 slides axially within the outer chamber, and the inner push cylinder 41 slides axially within the inner chamber. The two are pressure-linked through the hydraulic oil in the connecting hole 451. The positioning cylinder 452 also guides the sliding of the inner push cylinder 41, ensuring the straightness of its axial movement.

[0055] The coaxial nesting design of the fixed cylinder 44, the partition cylinder 45, and the positioning cylinder 452 ensures the coaxiality of the outer and inner chambers, making the movement axes of the outer push cylinder 42 and the inner push cylinder 41 coincide, avoiding jamming or sealing failure caused by misalignment. The separate design of the partition cylinder 45 and the fixed cylinder 44 facilitates processing and assembly; each part can be processed independently and then assembled, reducing manufacturing difficulty. The positioning cylinder 452 extends from the end of the partition cylinder 45 and is integrally or fixedly connected to the partition cylinder 45, providing good structural rigidity and stable guiding support for the inner push cylinder 41. The connecting holes 451 are distributed axially on the partition cylinder 45, facilitating processing, and multiple connecting holes 451 can be provided to increase the flow area of ​​hydraulic oil and improve response speed. This structure integrates the outer and inner chambers into a coaxial assembly, resulting in a compact overall structure that facilitates overall installation into the injection molding pipe 11, improving assembly efficiency and maintenance convenience. The outer wall of the fixed cylinder 44 can fit against the inner wall of the injection pipe 11, using the injection pipe 11 itself as an external constraint, which further enhances the stability of the structure.

[0056] An injection molding machine with a pressure holding function includes a pre-plasticizing mechanism with a pressure holding function.

[0057] The above embodiments only illustrate one or more implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of protection of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A pre-plasticizing mechanism with a pressure-holding function, characterized in that, include: An injection molding machine frame has an injection pipe on one side and a push cylinder on the other side. A sliding frame is also installed inside the injection molding machine frame. The sliding frame is connected to the output rod of the push cylinder. A motor is installed on the sliding frame. A spiral push rod is installed inside the injection pipe. The spiral push rod is drivenly connected to the output shaft of the motor. An injection head is located at the outlet of the injection pipe; A rotary valve is slidably disposed within the injection pipe along its axial direction, dividing the inner cavity of the injection pipe into an injection cavity communicating with the mold cavity and a feeding cavity communicating with the space where the spiral push rod is located. The rotary valve includes a fixed valve core and a rotary valve core coaxially arranged, and a pressure drive assembly for driving the rotary valve core to rotate relative to the fixed valve core. The fixed valve core has a fixed valve channel, and the rotary valve core has a rotary valve channel that can selectively communicate with the fixed valve channel. When the pressure of the feeding cavity on the pressure drive assembly is greater than a preset threshold, the pressure drive assembly drives the rotary valve core to rotate, so that the rotary valve channel communicates with the fixed valve channel. A reverse-push assembly is disposed inside the injection pipe and is drively connected to the helical push rod and the rotary valve, for driving the rotary valve, which is in the closed state, to squeeze the injection cavity when the helical push rod is reset.

2. The pre-plasticizing mechanism with pressure-holding function according to claim 1, characterized in that, The rotary valve also includes a sliding cylinder, which is coaxially and slidably disposed within the injection pipe; the fixed valve core is coaxially disposed at one end of the sliding cylinder facing the injection cavity; the rotary valve core is rotatably disposed within the sliding cylinder and abuts against the side of the fixed valve core facing the feeding cavity.

3. A pre-plasticizing mechanism with pressure-holding function according to claim 2, characterized in that, The rotary valve core has a driven cylinder at one end facing the feeding chamber. A mounting cavity is formed between the inner circumference of the sliding cylinder and the outer circumference of the driven cylinder. An arc-shaped groove is provided on the outer circumference of the driven cylinder. The pressure drive assembly includes: A pressure ring is coaxially and slidably disposed in the mounting cavity and connected to the inner circumference of the sliding cylinder by a spline. The inner circumference of the pressure ring is provided with a driving block that slides with the arc-shaped groove. An elastic element is disposed in the mounting cavity and abuts against the pressure ring.

4. A pre-plasticizing mechanism with pressure-holding function according to claim 3, characterized in that, A limiting boss is provided at one end of the outer periphery of the driven cylinder facing the feeding chamber, and the pressure ring elastically abuts against one end of the limiting boss.

5. A pre-plasticizing mechanism with pressure-holding function according to any one of claims 2-4, characterized in that, One end of the rotary valve core is provided with a connecting shaft, which passes through the fixed valve core and is rotatably connected to it. A retaining ring is provided at one end of the connecting shaft that extends to the injection cavity.

6. A pre-plasticizing mechanism with pressure-holding function according to any one of claims 1-4, characterized in that, The injection pipe has an outer chamber and an inner chamber coaxially arranged inside its opening, and a connecting hole is provided between the outer chamber and the inner chamber. The reverse pushing assembly includes: An inner push cylinder has one end coaxially connected to the rotary valve, and the other end extends into the inner chamber to form an inner piston end. The outer periphery of the inner push cylinder and the inner wall of the inner chamber enclose an inner pressure chamber, which is connected to the connecting hole. An outer push cylinder has one end connected to the head of the spiral push rod, and the other end extends into the outer chamber to form an outer piston end. The outer piston end and the inner wall of the outer chamber enclose an outer pressure chamber, which is connected to the connecting hole. Hydraulic oil is injected into the inner pressure chamber and the outer pressure chamber.

7. A pre-plasticizing mechanism with pressure-holding function according to claim 6, characterized in that, The reverse push assembly also includes a connecting rod that passes radially through the head of the helical push rod, and the two ends of the connecting rod are fixedly connected to the outer push cylinder.

8. A pre-plasticizing mechanism with pressure-holding function according to claim 6, characterized in that, The inner circumference of the injection-molded pipe is provided with a limiting groove extending along its axial direction, and the outer side of the rotary valve is provided with a limiting block, which extends into the limiting groove and slides in cooperation with it.

9. A pre-plasticizing mechanism with pressure-holding function according to claim 6, characterized in that, The reverse push component also includes: A fixed cylinder is coaxially disposed inside the injection pipe; A separator cylinder is coaxially disposed within the fixed cylinder. An outer cavity is formed between the outer circumference of the separator cylinder and the inner circumference of the fixed cylinder. A positioning cylinder is disposed at one end of the separator cylinder facing the feeding cavity. An inner cavity is formed between the outer circumference of the positioning cylinder and the inner circumference of the separator cylinder. The connecting holes are distributed axially on the separator cylinder.

10. An injection molding machine with a pressure-holding function, characterized in that, Includes a pre-plasticizing mechanism with a pressure-holding function as described in any one of claims 1-4.

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