A PET injection mold

Abstract

The utility model provides a kind of PET injection mould, it is related to mould technology, specifically discloses movable mould and fixed mould, the cavity is set up on the side wall opposite movable mould and fixed mould, the forming part compatible with cavity is equipped on the side wall opposite movable mould and fixed mould, injection channel is set up on the side of movable mould away from fixed mould, injection channel is communicated with cavity, injection channel is equipped in fixed mould and is communicated with cavity, ejector pin is installed in injection channel, and the local part of ejector pin is set in cavity after penetrating forming part, the inner hole of product is changed into ejector pin forming, and product is pushed out by push tube structure, improve the contact area of push-out structure and product, solve product fracture problem;Ejector pin is integrated in the channel of fixed mould, part of cavity is retained during injection, and gate condensation plugging is formed automatically.

Description

Technical Field

[0001] This utility model relates to the field of mold technology, and more specifically, to a PET injection mold. Background Technology

[0002] PET contains polyethylene terephthalate, the most important type of thermoplastic polyester, commonly known as polyester resin. It is a condensation polymer of terephthalic acid and ethylene glycol, and together with PBT, it is collectively referred to as thermoplastic polyester, or saturated polyester. Due to its excellent properties, PET plastic is widely used in the processing of various packaging containers such as plastic bottles. When processing PET plastic into thin-walled small containers, injection molding is generally required. During the injection molding process, because the temperature of the molten plastic is very high, the air pressure inside the mold cavity increases sharply as the molten plastic is injected into the mold cavity. This increases the resistance to the subsequent molten plastic, which can easily cause the melt to stop flowing, resulting in insufficient mold filling. Furthermore, when the thin-walled structure of the small container is ejected from the mold after molding, it is prone to breakage during the ejection process. Utility Model Content

[0003] The purpose of this utility model is to provide a PET injection mold that addresses the shortcomings of existing technologies and solves the problems mentioned in the background.

[0004] The technical solution of this utility model is implemented as follows:

[0005] The utility model provides a PET injection mold, including a moving mold and a fixed mold. A cavity is formed on the side wall opposite to the moving mold and the fixed mold. A molding part adapted to the cavity is formed on the side wall opposite to the moving mold and the fixed mold. An injection channel is formed on the side of the moving mold away from the fixed mold and the injection channel is connected to the cavity. An injection channel connected to the cavity is provided in the fixed mold. An ejector pin is installed in the injection channel and a portion of the ejector pin passes through the molding part and is placed in the cavity.

[0006] In some technical solutions of this utility model, the fixed mold includes an outer mold and an inner mold. The outer mold and the moving mold are detachably connected. The outer mold has an installation cavity for installing the inner mold. The molding part and the inner mold are integrally formed. The injection channel is located in the molding part. The inner mold has an inlet and outlet hole for installing ejector pins. The inlet and outlet hole is connected to the injection channel.

[0007] In some technical solutions of this utility model, a sleeve structure is installed in the inlet and outlet hole, the sleeve structure is slidably disposed in the inlet and outlet hole, a portion of the sleeve structure is embedded in the injection channel, and the ejector pin extends outward after passing through the sleeve structure.

[0008] In some technical solutions of this utility model, the cross-section of the injection channel is stepped.

[0009] In some technical solutions of this utility model, an annular cooling groove is provided on the outer side wall of the moving mold.

[0010] In some technical solutions of this utility model, a mold-separating mechanism is also provided. The mold-separating mechanism includes two mounting seats arranged in pairs. The two mounting seats are detachably connected to the moving mold and the fixed mold, respectively. A guide structure is installed on one of the mounting seats, and the other mounting seat is slidably disposed in the guide structure. A telescopic structure is installed on one of the mounting seats, and the telescopic end of the telescopic structure is detachably connected to the other mounting seat.

[0011] In some technical solutions of this utility model, an adjustment mechanism is also included for driving the sleeve structure to reciprocate within the inlet and outlet holes.

[0012] The inner mold has a first annular cooling channel on its outer side wall, and two second cooling channels communicating with the first cooling channel are formed along its axial direction on the outer side wall of the inner mold. The outer mold has two inlets and outlets that correspond one-to-one with the second cooling channels, and the second cooling channels are connected to their corresponding inlets and outlets.

[0013] Compared with the prior art, this utility model has at least the following advantages or beneficial effects: This technology changes the inner hole of the product to ejector pin molding, and the product is pushed out by the push tube structure, which increases the contact area between the push structure and the product and solves the problem of product breakage; the ejector pin is integrated into the channel of the fixed mold, and part of it is retained in the cavity during injection molding, which automatically forms the gate condensation and sealing; and the stepped flow channel controls the flow, preventing the natural accumulation of air bubbles at the cross-sectional abrupt change, and preventing the occurrence of porosity defects. Attached Figure Description

[0014] Figure 1 This is a three-dimensional structural diagram of the fixed mold and the moving mold of this utility model.

[0015] Figure 2 This is a cross-sectional structural diagram showing the working state of the fixed mold and the moving mold in this utility model.

[0016] Figure 3 This is a first-view cross-sectional structural diagram of the fixed mold and the moving mold of this utility model.

[0017] Figure 4 This is a second-view cross-sectional structural diagram of the fixed mold and the moving mold of this utility model.

[0018] Figure label:

[0019] 1. Fixed mold; 2. Outer mold; 3. Cooling ring groove; 4. Inlet and outlet; 5. Sleeve structure; 6. Ejector pin; 7. Mounting base; 8. Telescopic structure; 9. Guide structure; 10. Injection channel; 11. Product; 12. Inner mold; 13. First cooling channel; 14. Second cooling channel; 15. Adjustment mechanism. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0022] Example

[0023] This utility model provides a PET injection mold, such as Figures 1-4As shown, the system includes a moving mold and a fixed mold 1. Cavities are formed on the opposite sidewalls of the moving mold and the fixed mold 1. A molding part adapted to the cavity is provided on the opposite sidewall of the fixed mold 1 and the moving mold. An injection channel 10 is formed on the side of the moving mold away from the fixed mold 1, communicating with the cavity. An injection channel 10 communicating with the cavity is also provided inside the fixed mold 1. An ejector pin 6 is installed inside the injection channel 10, with a portion of the ejector pin 6 penetrating the molding part and then positioned within the cavity. The moving mold and the fixed mold 1 cooperate to form a closed cavity. The injection channel 10 guides molten PET material to fill the cavity, and the ejector pin 6 pushes the product out of the mold after injection. The working process of the above mold is as follows: First, the moving mold and the fixed mold 1 are closed, the molding part is embedded in the cavity to form the product cavity, the molten PET is injected into the cavity through the injection channel 10 of the moving mold, and at the same time, the injection channel 10 of the fixed mold 1 may serve as an auxiliary injection or venting channel. The material is cooled and solidified under pressure. The ejector pin 6 is partially embedded in the cavity to maintain the gate shape. After the moving and fixed molds are separated, the ejector pin 6 moves axially along the injection channel 10 to eject the product 11 from the molding part. The design of the double injection channel 10 enhances the uniformity of material filling, which is especially suitable for complex thin-walled PET products 11. The ejector pin 6 is integrated into the injection channel 10 of the fixed mold to realize automatic gate cutting and reduce manual trimming process. The ejector pin 6 is partially retained in the cavity during the injection stage. With the above structure, it forms corresponding holes in the molded part and can also cool the molded part. It can accurately control the gate solidification time, prevent stringing, and can also form blind holes in the injection molded part to assist in the formation of the injection molded part.

[0024] In some technical solutions of this utility model, the fixed mold 1 includes an outer mold 2 and an inner mold 12. The fixed mold 1 is designed in a modular manner. The outer mold 2 provides structural support, and the inner mold 12 independently undertakes the molding function to achieve rapid mold change. The outer mold 2 is detachably connected to the moving mold. The outer mold 2 has an installation cavity for installing the inner mold 12. The molding part and the inner mold 12 are integrally formed. The injection channel 10 is located in the molding part. The inner mold 12 has an inlet and outlet hole for installing the ejector pin 6, and the inlet and outlet hole is connected to the injection channel 10. The molding part and the inner mold 12 are integrally molded. The inner mold 12, which integrates the molding part and the injection channel 10, is embedded in the mounting cavity of the outer mold 2. The melt enters the cavity through the injection channel 10 of the inner mold 12. The ejector pin 6 slides in the inlet and outlet holes to complete the ejection action. The inner mold 12 can be directly replaced after the outer mold 2 is disassembled without the need for overall mold disassembly. The inner mold 12 is made of wear-resistant alloy and is manufactured separately to extend the life of high-wear areas and reduce the overall mold cost. The inlet and outlet holes are coaxially designed with the injection channel 10 to ensure the precise movement trajectory of the ejector pin 6 and avoid eccentric wear. The split structure allows different inner molds 12 to be matched with the same outer mold 2, realizing quick switching of "one mold with multiple cavities".

[0025] In some technical solutions of this utility model, a sleeve structure 5 is installed in the inlet and outlet hole. The sleeve structure 5 is slidably disposed in the inlet and outlet hole, and partially embedded in the injection channel 10. The ejector pin 6 extends outward after passing through the sleeve structure 5. The sleeve structure 5 serves as a guide and sealing component for the ejector pin 6, forming a dynamic sealing interface to prevent melt backflow. The melt pressure pushes the sleeve back into the inlet and outlet hole, and its front conical surface fits tightly against the wall of the injection channel 10 to form a pressure seal. When the sleeve structure 5 ejects the product 11, the ejector pin 6 is in a stationary state. The outer wall of the sleeve scrapes off residual PET from the surface of the ejector pin 6, keeping the ejector pin 6 clean. The thermal expansion coefficient of the sleeve matches that of the mold steel, maintaining sealing performance at high temperatures and preventing cold slug spots caused by overflow. The replaceable sleeve design solves the problem of repairing the wear of the ejector pin 6 hole in traditional integral molds. Furthermore, the inside of the sleeve is polished to reduce the friction coefficient of the ejector pin 6 movement and reduce the risk of jamming.

[0026] In some technical solutions of this utility model, the cross-section of the injection channel 10 is stepped. The stepped injection channel 10 forms a flow control node through abrupt changes in cross-section, which adjusts the shear rate. In the initial stage of filling, the melt maintains a low shear rate when passing through the large cross-section area to avoid excessive orientation of PET molecular chains. In the final filling stage, the shear rate increases when flowing through the small cross-section area, enhancing the shrinkage compensation ability of the last filled area. The stepped cross-section forms a natural venting node, and air bubbles gather at the abrupt changes in cross-section and are discharged through the mold parting surface. The graded shear control reduces the anisotropy of the product 11 and improves the optical uniformity of transparent products 11 such as PET preforms.

[0027] In some technical solutions of this utility model, an annular cooling groove 3 is provided on the outer wall of the moving mold. The annular cooling groove located on the outer side of the moving mold forms a closed-loop cooling circuit, realizing uniform and rapid heat dissipation on the moving mold side, reducing the internal stress of the product 11, and preventing stress whitening of the PET profile.

[0028] Preferably, the depth of the annular groove is adjustable to accommodate the different cooling needs of products with different wall thicknesses.

[0029] In some technical solutions of this utility model, a mold-separating mechanism is also included. This mechanism achieves high-precision mold opening and closing through the linkage of a precision optical axis guide mechanism and an electric push rod. The mold-separating mechanism includes two paired mounting seats 7, which are detachably connected to the moving mold and the fixed mold 1, respectively. One mounting seat 7 is equipped with a guide structure 9, and the other mounting seat 7 is slidably disposed within the guide structure 9. One mounting seat 7 is equipped with a telescopic structure 8, the telescopic end of which is detachably connected to the other mounting seat 7. The telescopic structure 8 (e.g., a servo electric cylinder) drives the mounting seat 7 to close precisely along the guide post. The mold-closing force is fed back in real time by a pressure sensor mounted on the fixed mold 1. When the telescopic end of the telescopic structure 8 retracts, the optical axis within the guide structure 9 ensures that the moving and fixed molds separate without lateral displacement. The separate design of the dual mounting seats 7 allows for individual replacement of the guide or drive components, reducing maintenance costs.

[0030] Preferably, the guide post surface is hard chrome plated and used with a graphite self-lubricating bearing to achieve oil-free lubrication and avoid contaminating food-grade PET products 11.

[0031] In some technical solutions of this utility model, an adjustment mechanism 15 is also included for driving the ejector pin 6 or the sleeve structure 5 to reciprocate within the inlet and outlet holes. The adjustment mechanism 15 is an electric push rod structure, with two electric push rods controlling the movement of the ejector pin 6 and the sleeve structure 5 respectively. Thus, through electromechanical coordinated control, the ejection stroke value can be input according to the size of the product 11, and the servo motor drives the ball screw in the electric push rod structure to adjust the initial position of the ejector pin 6 or the sleeve structure 5, ensuring the quality of the product 11 during manufacturing.

[0032] The inner mold 12 has a first annular cooling channel 13 on its outer side wall. The inner mold 12 has two second cooling channels 14 connected to the first cooling channel 13 along its axial direction on its outer side wall. The outer mold 2 has two inlets and outlets 4 that correspond one-to-one with the second cooling channels 14 on its side wall. The second cooling channels 14 are connected to their corresponding inlets and outlets 4. The circulating cooling channel composed of the first cooling channel 13, the second cooling channel 14 and the inlets and outlets 4 can accelerate the cooling of the inner mold 12 and prevent stress whitening of the PET profile.

[0033] Furthermore, sealing rings are provided at both ends of the inner mold 12, and the circulating cooling channel is located between the two sealing rings to prevent leakage of cooling medium (water, oil).

[0034] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A PET injection mold, characterized in that, The mold includes a moving mold and a fixed mold (1). The moving mold and the fixed mold (1) have cavities on their opposite sidewalls. The fixed mold (1) and the moving mold have molding parts that are adapted to the cavities on their opposite sidewalls. The moving mold has an injection channel (10) on the side away from the fixed mold (1). The injection channel (10) is connected to the cavity. The fixed mold (1) has an injection channel (10) connected to the cavity. An ejector pin (6) is installed in the injection channel (10). The ejector pin (6) is partially inserted through the molding part and placed in the cavity.

2. A PET injection mold according to claim 1, characterized in that, The fixed mold (1) includes an outer mold (2) and an inner mold (12). The outer mold (2) is detachably connected to the moving mold. The outer mold (2) has an installation chamber for installing the inner mold (12). The molding part is integrally formed with the inner mold (12). The injection channel (10) is located in the molding part. The inner mold (12) has an inlet and outlet hole for installing the ejector pin (6). The inlet and outlet hole is connected to the injection channel (10).

3. A PET injection mold according to claim 2, characterized in that, A sleeve structure (5) is installed in the inlet and outlet hole. The sleeve structure (5) is slidably disposed in the inlet and outlet hole. A portion of the sleeve structure (5) is embedded in the injection channel (10). The ejector pin (6) extends outward after passing through the sleeve structure (5).

4. A PET injection mold according to claim 1, characterized in that, The cross-section of the injection channel (10) is stepped.

5. A PET injection mold according to claim 1, characterized in that, The outer wall of the moving mold is provided with an annular cooling groove (3).

6. A PET injection mold according to any one of claims 1-5, characterized in that, It also includes a mold-separating mechanism, which includes two mounting seats (7) arranged in pairs. The two mounting seats (7) are detachably connected to the moving mold and the fixed mold (1) respectively. A guide structure (9) is installed on one of the mounting seats (7), and the other mounting seat (7) is slidably disposed in the guide structure (9). A telescopic structure (8) is installed on one of the mounting seats (7), and the telescopic end of the telescopic structure (8) is detachably connected to the other mounting seat (7).

7. A PET injection mold according to claim 3, characterized in that, It also includes an adjustment mechanism (15) for driving the sleeve structure (5) to reciprocate within the inlet and outlet holes.

8. A PET injection mold according to claim 2, characterized in that, The inner mold (12) has a first cooling channel (13) in the shape of an annular opening on its outer side wall. The inner mold (12) has two second cooling channels (14) that communicate with the first cooling channel (13) along its axial direction on its outer side wall. The outer mold (2) has two inlets and outlets (4) that correspond one-to-one with the second cooling channels (14) on its side wall. The second cooling channels (14) are connected to their corresponding inlets and outlets (4).

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