A mechanism for preventing injection molding flash for an injection molding mold

Abstract

The utility model discloses a kind of anti-injection burr mechanisms for injection mold, the burr mechanism includes cylinder body, the upper and lower parts of the cylinder body are respectively provided with gas storage cavity and piston cavity, the gas storage cavity and piston cavity are communicated by two groups of one-way flow passages with opposite airflow direction, piston is assembled in the piston cavity, piston rod that passes through cylinder body is fixedly connected in piston bottom portion.In the utility model, first, the compressibility of compressed air is used to store energy to reset piston rod when mold is opened, avoids the physical fatigue limit of metal material, eliminates the most fatal weakness of spring from principle, compressed air as medium, will not fatigue, system life mainly depends on sealing element and valve, far more than spring, even if check valve or throttle valve slightly leaks, system can still work for a period of time, significantly improve mold life and production stability, reduce unplanned downtime, reduce maintenance cost.

Description

Technical Field

[0001] This utility model relates to the field of injection mold technology, and in particular to an anti-burr mechanism for injection molds. Background Technology

[0002] In injection molding, due to the fluidity of plastic raw materials, their thermal expansion and contraction characteristics, and the complexity of product structures (such as thin walls, deep cavities, and insert splicing), molten plastic easily overflows from tiny gaps such as parting surfaces, ejector pin holes, or insert seams during high-pressure injection, forming burrs upon cooling. Burrs not only severely affect the product's appearance and dimensional accuracy but also require significant manpower for subsequent trimming or may even lead to product scrap, greatly reducing production efficiency and increasing manufacturing costs.

[0003] To address the aforementioned issues, existing technologies typically employ auxiliary mechanisms within the mold to enhance localized pressure in the mold-closing area, thereby preventing plastic overflow. For example, by installing a spring-driven pre-compression mechanism within the mold, additional clamping force is applied to areas prone to burrs during mold closing.

[0004] However, this spring-based solution has many inherent drawbacks: First, the injection mold opens and closes at an extremely high frequency (up to dozens of times per minute), and the spring is subjected to alternating loads for a long time, which makes it very easy for metal fatigue to occur, resulting in the loss of elasticity or breakage. Second, when the spring fails, the mechanism cannot reset properly, causing the burr problem to reappear, and may even damage the mold, resulting in unplanned downtime and maintenance costs. Utility Model Content

[0005] The purpose of this utility model is to provide an anti-burr mechanism for injection molds in order to solve the technical problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An anti-burr mechanism for injection molds is disclosed. The injection mold includes an upper mold base and a lower mold base. An upper mold is mounted on the upper mold base, and a lower mold is mounted on the lower mold base. When the upper mold and the lower mold are closed, they form a mold cavity. An anti-burr mechanism is mounted on the upper mold. The anti-burr mechanism includes a cylinder body. An air storage cavity and a piston cavity are respectively opened in the upper and lower parts of the cylinder body. The air storage cavity and the piston cavity are connected by two sets of unidirectional flow channels with opposite airflow directions. A piston is assembled in the piston cavity, and a piston rod passing through the cylinder body is fixedly connected to the bottom of the piston.

[0007] As a further description of the above technical solution: The unidirectional flow channel includes an ascending pipe and a return pipe. A one-way valve is installed on the ascending pipe, and a throttle valve is installed on the return pipe.

[0008] As a further description of the above technical solution: The bottom of the cylinder is provided with a bottom groove, and the bottom of the piston chamber is provided with a number of air holes that communicate with the bottom groove.

[0009] As a further description of the above technical solution: The cylinder body has an annular groove that exposes two sets of unidirectional flow channels, and the outer edge of the annular groove is engaged with a split arc-shaped shell.

[0010] As a further description of the above technical solution: The upper mold has a mounting groove for fixing the cylinder and a strip groove for accommodating the movement of the piston rod. The strip groove is connected to the mold cavity.

[0011] In summary, due to the adoption of the above technical solution, the beneficial effects of this utility model are: First, when the mold is closed, the piston rod rises under the injection pressure, moving away from the mold cavity and applying pressure to a specific position in the mold to prevent burrs from forming. The compressibility of compressed air stores energy to reset the piston rod when the mold is opened, avoiding the physical fatigue limit of the metal material and eliminating the most fatal weakness of the spring in principle. Secondly, compressed air, as the medium, does not experience fatigue. The system's lifespan depends primarily on the seals and valves, far exceeding that of springs. Even with slight leakage from the check valve or throttle valve, the system can still operate for a period of time, significantly improving mold life and production stability, reducing unplanned downtime, and lowering maintenance costs. Attached Figure Description

[0012] Figure 1 A schematic diagram of the internal structure of an anti-burr mechanism for injection molds according to an embodiment of the present invention is shown. Figure 2 A schematic diagram of the installation of the anti-burr mechanism according to an embodiment of the present invention on a mold is shown; Figure 3 A three-dimensional structural schematic diagram of the upper and lower molds provided according to an embodiment of the present utility model is shown; Figure 4 A three-dimensional structural schematic diagram of an injection mold provided according to an embodiment of the present utility model is shown; Figure 5 A top view schematic diagram of an injection mold provided according to an embodiment of the present utility model is shown; Figure 6 It shows Figure 5 Schematic diagram of the cross-sectional structure along the AA direction.

[0013] Legend: 1. Upper mold frame; 2. Lower mold frame; 3. Upper mold; 301. Mounting groove; 302. Strip groove; 4. Lower mold; 5. Anti-burr mechanism; 51. Cylinder body; 5101. Air storage cavity; 5102. Piston cavity; 5103. Annular groove; 5104. Bottom groove; 5105. Air hole; 52. Split-type arc-shaped shell; 53. Return pipe; 54. Ascending pipe; 55. One-way valve; 56. Throttle valve; 57. Piston; 58. Piston rod; 6. Mold cavity. Detailed Implementation

[0014] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0015] Please see Figure 1-6 This utility model provides a technical solution: an anti-burr mechanism for injection molds. The injection mold includes an upper mold frame 1 and a lower mold frame 2. An upper mold 3 is installed on the upper mold frame 1, and a lower mold 4 is installed on the lower mold frame 2. When the upper mold 3 and the lower mold 4 are closed, a mold cavity 6 is formed. The upper mold 3 has an installation groove 301 for fixing a cylinder 51 and a strip groove 302 for accommodating the movement of a piston rod 58. The strip groove 302 is connected to the mold cavity 6 and provides space for the up and down movement of the piston rod 58, allowing its end to act on the area near the mold cavity 6. The upper mold 3 is equipped with an anti-burr mechanism 5. When the mold is closed, the piston rod 58 rises under the injection pressure, moving away from the mold cavity and applying pressure to a specific position on the mold to prevent burrs from forming. The compressibility of compressed air stores energy to reset the piston rod 58 when the mold is opened, avoiding the physical fatigue limit of the metal material. In principle, this eliminates the most fatal weakness of the spring. Moreover, compressed air, as the medium, will not experience fatigue. The system life depends mainly on the seals and valves, far exceeding that of the spring. Even if the one-way valve 55 or the throttle valve 56 leaks slightly, the system can still work for a period of time, significantly improving the mold life and production stability, reducing unplanned downtime, and lowering maintenance costs.

[0016] Specifically, such as Figure 1As shown, the anti-burr mechanism 5 includes a cylinder 51. The upper and lower parts of the cylinder 51 are respectively provided with an air storage cavity 5101 and a piston cavity 5102. The air storage cavity 5101, acting as a "pneumatic spring," stores compressed air. A piston 57 is assembled inside the piston cavity 5102. A piston rod 58, passing through the cylinder 51, is fixedly connected to the bottom of the piston 57 and serves as the main moving and working chamber. The piston 57 moves within the piston cavity 5102, while the piston rod 58 extends from the bottom of the cylinder 51. During mold closing, it rises under injection pressure, moving away from the mold cavity and applying pressure to specific locations on the mold to prevent burrs. A bottom groove 5104 is provided at the bottom of the cylinder 51, and several air holes 5105 communicating with the bottom groove 5104 are provided at the bottom of the piston cavity 5102. The air vent 5105 introduces air pressure into the bottom of the piston chamber 5102, allowing the piston assembly to provide initial reset power based on its own gravity when the mold is opened. The air storage cavity 5101 and the piston chamber 5102 are connected by two sets of one-way flow channels with opposite airflow directions, namely the rising pipe 54 and the return pipe 53, to achieve energy storage and controllable release. A one-way valve 55 is installed on the rising pipe 54, which allows air to flow from the piston chamber 5102 to the air storage cavity 5101, but prevents reverse flow; this is the energy storage channel. A throttle valve 56 is installed on the return pipe 53. The throttle valve 56 does not restrict "whether it can flow" but precisely controls the "speed" of air flowing back from the air storage cavity 5101 to the piston chamber 5102; this is the controllable energy release channel.

[0017] Specifically, such as Figure 1 As shown, the cylinder body 51 has an annular groove 5103 that exposes two sets of unidirectional flow channels. The outer edge of the annular groove 5103 is engaged with a split arc-shaped housing 52, which seals the pipes and valves inside the cylinder body 51. This makes the internal pneumatic circuit easy to install, maintain and replace, and improves the modularity and maintainability of the mechanism.

[0018] Working principle: When in use, in the open mold state, the bottom of the piston chamber 5102 has no pressure in the rod chamber, and the piston 57 and piston rod 58 are at their lowest position under their own weight. At this time, the air storage cavity 5101 stores the compressed air left over from the previous cycle, the anti-burr mechanism 5 is in standby state, and the piston rod 58 does not apply pressure. During mold closing, the piston rod 58 is pushed upward by the injection pressure. When the thrust exceeds the weight and friction of the piston assembly, the piston 57 and piston rod 58 begin to rise. During the rise of the piston 57, the air in the rod chamber at the top of the piston chamber 5102 is compressed, and the pressure of the compressed air increases, opening the one-way valve 55 on the riser pipe 54. The air flows into the air storage cavity 5101 through the riser pipe 54 and is stored. The piston rod 58 continues to rise and moves within the strip groove 302, precisely pressing... An additional, controllable preload is applied to the potential burr area of ​​the mold (such as the seam of the core insert). When the mold is fully closed, the piston rod 58 reaches its highest position and is flush with the bottom of the strip groove 302. Under the additional pressure applied by the piston rod 58, the mold closing surface is firmly pressed, and the molten plastic is injected into the mold cavity 6. Due to the additional pressing effect of the anti-burr mechanism 5, the plastic is effectively prevented from overflowing from the mold parting surface or insert gap under high pressure, thereby preventing the generation of burrs. After injection molding is completed, the mold begins to open, and the injection pressure is lost. The upward thrust acting on the lower surface of the piston rod 58 disappears, and the weight of the piston assembly causes the piston 57 to descend. The space of the rodless chamber in the upper part of the piston chamber 5102 increases, and the pressure decreases. At this time, the compressed air stored in the air storage cavity 5101 forms a pressure difference with the rodless chamber. The high-pressure air in the air storage cavity 5101 pushes the throttle valve 56 on the return pipe 53, and the air begins to flow from the air storage cavity 5101 to the rodless chamber. The throttle valve 56 limits the air flow rate, thereby controlling the speed at which the piston descends, making it descend smoothly and slowly, avoiding the impact and vibration caused by rapid descent. Under the combined action of the thrust of the compressed air and the weight of the piston assembly, the piston 57 and piston rod 58 smoothly return to the lowest position, and the mechanism returns to its initial state, waiting for the next cycle.

[0019] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A mechanism for preventing burrs in injection molds, the injection mold comprising an upper mold base (1) and a lower mold base (2), an upper mold (3) mounted on the upper mold base (1), and a lower mold (4) mounted on the lower mold base (2), wherein the upper mold (3) and the lower mold (4) form a mold cavity (6) when closed, and an anti-burr mechanism (5) is mounted on the upper mold (3), characterized in that, The simulated rough edge mechanism (5) includes a cylinder (51), and the upper and lower parts of the cylinder (51) are respectively provided with an air storage cavity (5101) and a piston cavity (5102). The air storage cavity (5101) and the piston cavity (5102) are connected by two sets of unidirectional flow channels with opposite airflow directions. A piston (57) is assembled in the piston cavity (5102), and a piston rod (58) passing through the cylinder (51) is fixedly connected to the bottom of the piston (57).

2. The anti-burr mechanism for injection molds according to claim 1, characterized in that, The one-way flow channel includes an ascending pipe (54) and a return pipe (53). A one-way valve (55) is installed on the ascending pipe (54), and a throttle valve (56) is installed on the return pipe (53).

3. The anti-burr mechanism for injection molds according to claim 1, characterized in that, The bottom of the cylinder (51) is provided with a bottom groove (5104), and the bottom of the piston chamber (5102) is provided with a number of air holes (5105) that communicate with the bottom groove (5104).

4. The anti-burr mechanism for injection molds according to claim 1, characterized in that, The cylinder body (51) has an annular groove (5103) that exposes two sets of unidirectional flow channels, and the outer edge of the annular groove (5103) is engaged with a split arc-shaped shell (52).

5. The anti-burr mechanism for injection molds according to claim 1, characterized in that, The upper mold (3) has an installation groove (301) for fixing the cylinder (51) and a strip groove (302) for accommodating the piston rod (58). The strip groove (302) is connected to the mold cavity (6).

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