Injection-molded plastic anti-overflow structure

Abstract

The application relates to the field of injection molding structures, in particular to an injection molding glue anti-overflow structure which comprises the following steps: the valve needle is arranged in a movable state, a driving structure drives the valve needle to reciprocate in a hot runner when the valve needle is away from a hot nozzle, when the molten plastic in the hot runner reaches the outflow position of the valve needle sleeve, the reciprocating valve needle drives the molten plastic about to flow out from the valve needle sleeve to move to the hot runner side, so that the molten plastic is prevented from leaking out from the valve needle sleeve, and the hot runner accessory damage caused by the contact between the high-temperature molten plastic and the hot runner accessory is avoided.

Description

Technical Field

[0001] The present invention relates to the field of injection molding structures, in particular to an injection molding glue overflow prevention structure. Background Art

[0002] refer to Figure 1 and Figure 2 During injection molding, an air pump drives the piston back to the top of the cylinder, while simultaneously moving the valve needle away from the hot nozzle's injection port, opening the nozzle for injection. Once removed, the valve needle remains essentially stationary and has no effect on the molten plastic during the injection process. However, as the machine barrel begins injecting molten plastic into the mold cavity, the hot runner is squeezed by the barrel, creating a significant pressure that causes the molten plastic to move toward the valve needle housing.

[0003] Because the valve pin sleeve and valve pin have a clearance fit, the highly fluid molten plastic, under the pressure of the hot runner, will flow into the gap between the sleeve and the pin, causing leakage from the sleeve. The hot molten plastic will then come into contact with the hot runner components, where it can easily damage them. This not only wastes production costs for the mold maker but also makes hot runner maintenance difficult.

[0004] Therefore, the prior art still has deficiencies and needs further improvement. Summary of the Invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide an injection molding glue anti-overflow structure to solve the technical problem of glue leakage during the injection molding process of the existing injection molding machine.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The present invention provides an injection molding glue overflow prevention structure, comprising:

[0008] The cylinder body is provided with a cavity therein and a diversion port is provided on the cylinder body;

[0009] The hot runner is connected to the external injection molding machine and is provided with a hot nozzle for injection molding;

[0010] A valve needle sleeve is arranged on the diversion port of the cylinder body;

[0011] The valve needle, one end of which is located in the cavity of the cylinder body, and the other end passes through the valve needle sleeve and is inserted into the hot runner to the hot nozzle. The valve needle sleeve and the valve needle are clearance-fitted;

[0012] The driving structure is connected to the cylinder body, and drives the valve needle away from the injection port of the hot nozzle, and when the valve needle is away from the injection port of the hot nozzle, drives the valve needle to reciprocate in the hot runner.

[0013] The injection molded anti-overflow structure also includes:

[0014] A first piston is movably disposed in the cavity, and a driving structure drives the first piston to reciprocate in the cylinder;

[0015] The second piston is movably disposed in the cavity and movably connected to the first piston, and the valve needle is connected to a side of the second piston away from the first piston;

[0016] The driving structure drives the second piston to move toward the first piston, and the first piston pushes the second piston to drive the valve needle to reciprocate in the hot runner.

[0017] The driving structure is an air pressure pump.

[0018] The air pressure pump is provided with a first pipe and a second pipe connected to the cavity of the cylinder body, and the connection points of the first pipe and the second pipe with the cylinder body are respectively located at the two ends of the first piston. The air pressure pump drives the first piston through the first pipe and the second pipe.

[0019] The air pressure pump is provided with a third pipe connected to the cavity of the cylinder body, and the connection point of the third pipe and the cylinder body is located on the side of the second piston away from the first piston. The air pressure pump drives the second piston through the third pipe.

[0020] The reciprocating stroke of the valve needle in the hot runner is 1-2mm.

[0021] The air pressure pump drives the first piston to move in the cavity of the cylinder within a range of 1-2 mm, and the first piston pushes the second piston to move within a range of 1-2 mm.

[0022] A gear structure is provided in the cylinder body, which limits the first piston so that the movement range of the first piston between the gear structure and the top of the cylinder body is 1-2 mm.

[0023] A first bulge is provided on the first piston, and the first bulge is used to push against the second piston.

[0024] A second bulge is provided on the side of the first piston away from the second piston, and a concave avoidance structure is provided on the top of the cylinder body. The second bulge is movably inserted into the avoidance structure.

[0025] The beneficial effect of the present invention is that: the existing valve needle is basically stationary during the injection molding process and does not push the molten plastic to the side of the hot runner. The present application sets the valve needle in a movable state. When the valve needle is away from the injection port of the hot nozzle, the driving structure drives the valve needle to reciprocate in the hot runner. When the molten plastic in the hot runner reaches the outflow position of the valve needle sleeve, the reciprocating valve needle will drive the molten plastic that is about to flow out of the valve needle sleeve to move toward the side of the hot runner, thereby preventing the molten plastic from leaking from the valve needle sleeve, thereby avoiding damage to the hot runner accessories caused by contact between the high-temperature molten plastic and the hot runner accessories. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0027] Figure 1 It is a structural diagram of the prior art;

[0028] Figure 2 It is a partial enlarged diagram of the structural schematic diagram of the prior art;

[0029] Figure 3 This is a schematic structural diagram of the anti-overflow structure of the injection molding adhesive of the present invention;

[0030] Figure 4 is a schematic diagram of the second piston of the present invention being at the bottom of the cylinder;

[0031] Figure 5 Schematic diagram of the second piston abutting against the first piston of the present invention;

[0032] Figure 6 is a schematic diagram of the flow of molten plastic to the valve needle sleeve of the present invention;

[0033] Figure 7 is a schematic diagram of the first piston pushing the second piston of the present invention;

[0034] Figure 8 It is a schematic diagram of the valve needle of the present invention pushing the molten plastic to flow into the hot runner.

[0035] The accompanying drawings are numerals: 100 - movable piston, 200 - existing valve needle;

[0036] 1-cylinder body, 2-hot runner, 3-valve needle sleeve, 4-valve needle, 5-hot nozzle, 6-air pressure pump, 7-first piston, 8-second piston, 9-first pipeline, 10-second pipeline, 11-third pipeline, 12-cylinder head, 13-cylinder groove, 14-first bump, 15-second bump, 16-avoidance structure, 17-gear structure. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0038] refer to Figure 1 and Figure 2 When the injection molding machine is injecting, the piston 100 moves back to the top of the cylinder 1 and drives the existing valve needle 200 to move away from the injection port of the hot nozzle 5. Then the plastic in the hot runner 2 is injected from the hot nozzle 5. During the injection molding process, the existing valve needle 200 is basically in a stationary state and has no effect on the plastic.

[0039] Because there is a clearance fit between the valve needle sleeve 3 and the existing valve needle 200, during injection molding, the pressure generated in the hot runner 2 causes the plastic to flow into the gap between the valve needle sleeve 3 and the existing valve needle 200 and out of the valve needle sleeve 3, causing plastic leakage from the valve needle sleeve 3. The leaked high-temperature plastic can damage the hot runner 2 components, so plastic leakage from the valve needle sleeve 3 must be avoided.

[0040] Based on the above questions, refer to Figure 3 The present invention provides an injection molding glue overflow prevention structure, comprising:

[0041] The cylinder body 1 is provided with a cavity therein and a diversion port is provided on the cylinder body 1;

[0042] The hot runner 2 is connected to an external injection molding machine and is provided with a hot nozzle 5 for performing injection molding;

[0043] The valve needle sleeve 3 is arranged on the diversion port of the cylinder body 1;

[0044] The valve needle 4 has one end located in the cavity of the cylinder 1 and the other end passing through the valve needle sleeve 3 and inserted into the hot runner 2 to the hot nozzle 5. The valve needle sleeve 3 and the valve needle 4 are clearance-fitted;

[0045] The driving structure is connected to the cylinder body 1 , and drives the valve needle 4 away from the injection port of the hot nozzle 5 , and when the valve needle 4 is away from the injection port of the hot nozzle 5 , drives the valve needle 4 to reciprocate in the hot runner 2 .

[0046] In this application, the valve needle 4 is set to a movable state. When the valve needle 4 is away from the injection port of the hot nozzle 5, the driving structure drives the valve needle 4 to reciprocate in the hot runner 2. When the molten plastic in the hot runner 2 reaches the outflow position of the valve needle sleeve 3, the reciprocating valve needle 4 will drive the molten plastic that is about to flow out of the valve needle sleeve 3 to move to the side of the hot runner 2 to avoid the molten plastic from leaking from the valve needle sleeve 3, thereby avoiding damage to the hot runner 2 accessories caused by contact between the high-temperature molten plastic and the hot runner 2 accessories.

[0047] Specifically, during the injection molding process, the fluid molten plastic, under pressure within the hot runner 2, flows into the gap between the valve needle sleeve 3 and the valve needle 4, causing plastic leakage from the valve needle sleeve 3. The valve needle 4 reciprocates, constantly moving back and forth within the hot runner 2, generating a force that pushes the molten plastic back into the hot runner 2. This manifests as the valve needle 4, moving toward the side of the hot runner 2, pushing the molten plastic back into the hot runner 2 just as it's about to flow out of the valve needle sleeve 3. Throughout the injection molding process, the valve needle 4 reciprocates in this way, pushing the molten plastic between the valve needle sleeve 3 and the valve needle 4 back into the hot runner 2, effectively preventing the molten plastic from flowing out of the valve needle sleeve 3.

[0048] In some embodiments, reference Figure 3 and Figure 4 The injection molding anti-overflow structure also includes a piston, which is arranged in the cavity of the cylinder body 1. The piston includes a first piston 7 and a second piston 8. The first piston 7 is movably arranged in the cavity, and the driving structure drives the first piston 7 to reciprocate in the cylinder body 1. The second piston 8 is movably arranged in the cavity and is movably connected to the first piston 7. The valve needle 4 is connected to the side of the second piston 8 away from the first piston 7. The first piston 7 and the second piston 8 are movably connected, that is, the first piston 7 and the second piston 8 can be brought into contact or disconnected by movement.

[0049] When injection molding is to be performed, the drive structure drives the first piston 7 back to the top of the cylinder body 1, leaving space for the second piston 8 to move. The drive structure drives the second piston 8 to move toward the side of the first piston 7. The bottom of the first piston 7 presses against the second piston 8, limiting the second piston 8. During this process, the second piston 8 drives the valve needle 4 to move away from the injection port of the hot nozzle 5, and the plastic flows out of the injection port of the hot nozzle 5 for injection molding. Then, the drive structure drives the first piston 7 to move back and forth in the cylinder body 1. The reciprocating first piston 7 will continuously push the second piston 8 to move toward the side of the hot runner 2. During the injection molding process, the pressure generated in the hot runner 2 will drive the valve needle 4 to continuously move toward the first piston 7. Therefore, the second piston 8 drives the valve needle 4 to move toward the side of the hot runner 2, and the pressure in the hot runner 2 drives the valve needle 4 to move toward the first piston, thereby realizing the reciprocating motion of the valve needle 4, thereby realizing the reciprocating motion of the valve needle 4 in the hot runner 2.

[0050] It should be noted that the reciprocating movement distance range of the first piston 7 is very small. After the valve needle 4 moves away from the injection port of the hot nozzle 5, it will not push the valve needle 4 to block the injection port of the hot nozzle 5. The movement amplitude of the valve needle 4 is very small. When designing the movement range of the valve needle 4, the valve needle 4 can push the plastic to prevent it from flowing out of the valve needle sleeve 3, and at the same time does not affect the normal injection molding at the hot nozzle 5. The actual movement range distance of the valve needle 4 can be set according to actual needs.

[0051] In some embodiments, the driving structure is configured as an air pressure pump 6 , which drives the movement of the first piston 7 and the second piston 8 by means of air pressure.

[0052] In some embodiments, reference Figure 3 The air pump 6 is provided with a first pipe 9 and a second pipe 10, which are connected to the cylinder body 1 and communicate with the cavity of the cylinder body 1. The connection points of the first pipe 9 and the second pipe 10 with the cylinder body 1 are respectively located at the two ends of the first piston 7. The connection point of the first pipe 9 with the cylinder body 1 is located on the side of the first piston 7 away from the second piston 8, and the connection point of the second pipe 10 with the cylinder body 1 is located between the first piston 7 and the second piston 8. When injection molding is required to drive the first piston 7, the second pipe 10 is fed into the cylinder body 1, and the air pressure pushes the first piston 7 to move toward the top side of the cylinder body 1 (the side of the cylinder head 12). When the first pipe 9 is fed into the cylinder body 1, the air pressure pushes the first piston 7 to move toward the side away from the cylinder head 12. By alternately feeding the first pipe 9 and the second pipe 10 into the cylinder body 1, the reciprocating motion of the first piston 7 is achieved.

[0053] In some embodiments, reference Figures 3 to 5 The air pump 6 is provided with a third pipe 11 connected to the cavity of the cylinder body 1. The connection point between the third pipe 11 and the cylinder body 1 is located on the side of the second piston 8 away from the first piston 7. When the first piston 7 moves to the top of the cylinder body 1, it leaves space for the second piston 8 to move. The air pump 6 draws air into the cylinder body 1 through the third pipe 11 to drive the second piston 8 to move toward the side of the first piston 7. The second piston 8 drives the valve needle 4 to move away from the hot nozzle 5, so that the hot runner 2 can perform injection molding.

[0054] After the valve needle 4 is removed from the injection port of the hot nozzle 5, the third pipe 11 no longer takes in air. During injection molding, the highly fluid molten plastic, under pressure within the hot runner 2, flows toward the valve needle sleeve 3. During this process, the flowing molten plastic drives the valve needle 4 toward the first piston 7. The reciprocating motion of the first piston 7 pushes the valve needle 4 toward the hot runner 2, pushing the molten plastic back into the hot runner 2. During the injection molding process, the molten plastic continuously drives the valve needle 4 toward the first piston 7. The first piston 7, in turn, continuously moves the valve needle 4 toward the hot runner 2 via the second piston 8, thereby achieving reciprocating motion of the valve needle 4 within the hot runner 2.

[0055] During the injection molding process, when the molten plastic in the hot runner 2 is injected, pressure is generated to push the valve needle 4 toward the side of the first piston 7. In this embodiment, the pressure generated by the injection of the molten plastic in the hot runner 2 drives the valve needle 4 to move toward the side of the first piston 7, and the first piston 7 pushes the valve needle 4 to move toward the side of the hot runner 2, thereby realizing the reciprocating motion of the valve needle 4. In another embodiment, the reciprocating motion of the valve needle 4 in the hot runner 2 can be realized by the second valve needle 4 and the third valve needle 4. For example, the air intake of the second pipe 10 pushes the second piston 8 to drive the valve needle 4 to move toward the side of the hot runner 2, and the air intake of the third pipe 11 pushes the second piston 8 to drive the valve needle 4 to move toward the side of the first piston 7, thereby driving the reciprocating motion of the valve needle 4. The force is provided by the air pressure pump 6, thereby realizing the reciprocating motion of the valve needle 4 in the hot runner 2.

[0056] In some embodiments, reference Figures 5 to 8 After the valve needle 4 moves away from the injection port of the hot nozzle 5, it pushes the plastic flowing into the valve needle sleeve 3 back toward one end of the hot runner 2 through reciprocating motion. This movement of the valve needle 4 toward the hot nozzle 5 must not affect the normal injection of the hot runner 2. Therefore, the displacement of the valve needle 4 toward the hot nozzle 5 should not be too large. When the valve needle 4 is away from the hot nozzle 5, the range or stroke of the valve needle 4's reciprocating motion is 1-2mm. According to tests, within this stroke range, the valve needle 4 can effectively push back the plastic flowing into the valve needle sleeve 3, preventing it from flowing out of the valve needle sleeve 3, and will not affect the injection of the hot nozzle 5.

[0057] In some embodiments, the second piston 8 drives the valve needle 4 to move toward the hot runner 2 with a stroke of 1-2 mm. Therefore, the movement range of the second piston 8 in the cylinder 1 is also 2 mm, and the movement of the second piston 8 toward the hot nozzle 5 is driven by the first piston 7. The movement of the second piston 8 is driven by the first piston 7, so the range of the reciprocating motion of the first piston 7 in the cylinder 1 is also 1-2 mm. Therefore, it can be seen that when the air pump 6 drives the first piston 7 back to the top of the cylinder 1, the air pump 6 pushes the second piston 8 toward the side of the first piston 7 until it hits the first piston 7. Then, the reciprocating motion of the first piston 7 pushes the second piston 8 toward the hot runner 2, thereby pushing back the plastic that is about to flow out of the valve needle sleeve 3.

[0058] During the injection molding process, the pressure in the hot runner 2 will push the valve needle 4 to move toward the side of the first piston 7, causing the second piston 8 to return to the stroke range of the first piston 7 again. At this time, the first piston 7 will push the second piston 8 again to drive the valve needle 4 to move toward the side of the hot runner 2, thereby realizing the reciprocating motion of the valve needle 4 to continuously push the plastic flowing into the valve needle sleeve 3 toward the side of the hot runner 2, thereby preventing the plastic from flowing out of the valve needle sleeve 3.

[0059] Alternatively, the second piston 8 can be directly pushed to perform a 1-2 mm reciprocating motion within the cylinder 1 by the second and third pipes 10, 11 on the drive structure. For example, air entering the third pipe 11 pushes the second piston 8 away from the hot runner 2, while air entering the second pipe 10 pushes the second piston 8 toward the hot runner, and so on, to achieve reciprocating motion of the valve needle 4.

[0060] In some embodiments, reference Figure 3 The cylinder body 1 includes a cylinder head 12 and a cylinder groove 13. The cylinder head 12 covers the cylinder groove 13. The assembly of the cylinder head 12 and the cylinder groove 13 forms a cavity in the cylinder body 1, and the piston moves in the cylinder body 1. After the cylinder head 12 is removed from the cylinder groove 13, the piston or other components in the cylinder groove 13 can be inspected, repaired or replaced.

[0061] In some embodiments, reference Figure 5 and Figure 7 A stop structure 17 is provided within the cylinder body 1. This stop structure 17 constrains the first piston 7 between the stop structure 17 and the cylinder head 12 (the top of the cylinder body 1), allowing the first piston 7 to reciprocate only between the stop structure 17 and the cylinder head 12, with a range or stroke of 1-2 mm. The stop structure 17 limits the movement of the first piston 7, preventing poor injection caused by excessive movement of the first piston 7.

[0062] In some embodiments, reference Figure 3A first protrusion 14 is provided on the side of the first piston 7 away from the cylinder cover 12. The first protrusion 14 is used to push against the second piston 8. During the reciprocating motion of the first piston 7, the first piston 7 pushes the second piston 8 through the first protrusion 14. The setting of the first protrusion 14 facilitates the first piston 7 to push the second piston 8.

[0063] In some embodiments, reference Figure 3 A second protrusion 15 is provided on the side of the first piston 7 away from the second piston 8, and a recessed avoidance structure 16 is provided on the inner side of the cylinder cover 12. The driving structure drives the first piston 7 to move to the top of the cylinder body 1 so that the second protrusion 15 is inserted into the avoidance structure 16. The avoidance structure 16 plays a positioning role for the first piston 7.

[0064] The following is an overall description of the anti-overflow structure of the injection molding glue of this application:

[0065] During injection molding, the injection molding machine fills the hot runner 2 with molten plastic. Once the hot runner 2 is completely filled with molten plastic, the valve needle 4 is closed (located at the hot nozzle 5). The air pump 6 then drives the first piston 7 toward the top of the cylinder 1. The air pump 6 then drives the second piston 8 toward the first piston 7, moving the valve needle 4 away from the hot nozzle's injection port 5. The molten plastic in the hot runner 2 then flows through the hot nozzle 5 and into the mold cavity. Due to the injection pressure generated during plastic injection, this pressure causes the valve needle 4 to move toward the first piston 7. Furthermore, because the valve needle 4 and the valve needle sleeve 3 are clearance-fitted, the more fluid molten plastic flows out through the gap between the valve needle sleeve 3 and the valve needle 4. The first piston 7 is driven by the air pump 6 to perform a reciprocating motion with a stroke of 1-2 mm in the cylinder 1. Each time the valve needle 4 is pushed to the side of the first piston 7 by the plastic pressure, the movement of the first piston 7 toward the side of the hot runner 2 will push the second piston 8 to drive the valve needle 4 to move toward the side of the hot nozzle 5. In the process of the valve needle 4 moving toward the side of the hot nozzle 5, the valve needle 4 will drive the molten plastic at the valve needle sleeve 3 to move toward the side of the hot nozzle 5, thereby preventing the molten plastic from flowing out of the valve needle sleeve 3.

[0066] refer to Figure 4 , the second piston 8 is located at the bottom of the cylinder 1, and the valve needle 4 blocks the hot nozzle 5. When injection molding is required, the injection molding machine fills the hot runner 2 with molten plastic, and the drive structure drives the second piston 8 to move toward the side of the first piston 7, so that the valve needle 4 opens the hot nozzle 5 for injection molding.

[0067] refer to Figure 5 The driving structure drives the second piston 8 to move to abut the first piston 7. At this time, the valve needle 4 opens and the molten plastic is injected through the hot nozzle 5. During the injection molding process, in the prior art, due to the pressure in the hot runner 2, the molten plastic will flow to the gap between the valve needle sleeve 3 and the valve needle 4, and flow out from the valve needle sleeve 3. Figure 1 and Figure 2 .

[0068] refer to Figures 5 to 8 In the injection molding process, the pressure that always exists in the hot runner 2 will push the valve needle 4 toward the first piston 7. Since the valve needle 4 is set to a reciprocating state, after the valve needle 4 moves toward the first piston 7, the first piston 7 pushes the second piston 8 to drive the valve needle 4 toward the hot nozzle 5 (the driving structure stops ventilating the second piston 8 after driving the valve needle 4 away from the injection port of the hot nozzle 5), so that the molten plastic flowing into the valve needle sleeve 3 will be pushed back to the hot runner 2, thereby preventing the molten plastic from flowing out of the valve needle sleeve 3. This process is manifested as the reciprocating motion of the valve needle 4. Combined with Figure 6 and Figure 8 It can be seen that the molten plastic flows into the flow direction between the valve needle sleeve 3 and the valve needle 4, and the valve needle 4 pushes the molten plastic to move toward the hot runner 2 side.

[0069] refer to Figure 5 and Figure 7 , it can be seen that the distance between the first piston 7 and the shift structure 17 on the cylinder body 1 is 2 mm, which is the range in which the first piston 7 can move between the shift structure 17 and the cylinder cover 12. Figure 5 It can be seen from FIG that before the first piston 7 pushes the second piston 8, the distance between the first piston 7 and the shift structure 17 is 2 mm. Figure 7 As can be seen in the figure, when the first piston 7 pushes the second piston 8 to move toward the hot runner 2, the first piston 7 is in contact with the shift structure 17. The driving structure drives the first piston 7 to move back and forth between the shift structure 17 and the cylinder head 12 until the injection molding is completed.

[0070] In this application, the valve needle 4 is set to a reciprocating motion state. During the injection molding process, the valve needle 4 moves toward the hot nozzle 5 of the hot runner 2 again and again. Each time the valve needle 4 moves toward the hot nozzle 5, it can push the molten plastic, so that the molten plastic is prevented from flowing out of the valve needle sleeve 3.

[0071] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A plastic injection glue overflow prevention structure, characterized in that: include: A cylinder body is provided with a cavity therein and a diversion port is provided on the cylinder body; A hot runner connected to an external injection molding machine, wherein a hot nozzle is provided on the hot runner for performing injection molding; A valve needle sleeve is provided on the diversion port of the cylinder body; A valve needle, one end of which is located in the cavity of the cylinder body, and the other end of which passes through the valve needle sleeve and is inserted into the hot runner to the hot nozzle, and the valve needle sleeve and the valve needle are in a clearance fit; a driving structure connected to the cylinder body, wherein the driving structure drives the valve needle away from the injection port of the hot nozzle, and when the valve needle is away from the injection port of the hot nozzle, drives the valve needle to reciprocate in the hot runner; The injection molding anti-overflow structure also includes: a first piston movably disposed in the cavity, wherein the driving structure drives the first piston to reciprocate in the cylinder; a second piston movably disposed in the cavity and movably connected to the first piston, wherein the valve needle is connected to a side of the second piston away from the first piston; The driving structure drives the second piston to move toward the first piston, and the first piston pushes the second piston to drive the valve needle to reciprocate in the hot runner.

2. The anti-overflow structure for injection molding according to claim 1, characterized in that: The driving structure is an air pressure pump.

3. The anti-overflow structure for injection molding according to claim 2, characterized in that: The air pressure pump is provided with a first pipe and a second pipe connected to the cavity of the cylinder body, and the connection points of the first pipe and the second pipe with the cylinder body are respectively located at the two ends of the first piston. The air pressure pump drives the first piston through the first pipe and the second pipe.

4. The anti-overflow structure for injection molding according to claim 3, characterized in that: The air pressure pump is provided with a third pipe connected to the cavity of the cylinder body, and the connection point between the third pipe and the cylinder body is located on the side of the second piston away from the first piston. The air pressure pump drives the second piston through the third pipe.

5. The anti-overflow structure for injection molding according to any one of claims 2 to 4, characterized in that: The reciprocating stroke of the valve needle in the hot runner is 1-2 mm.

6. The anti-overflow structure for injection molding according to claim 5, characterized in that: The air pressure pump drives the first piston to move within the cavity of the cylinder within a range of 1-2 mm, and the first piston pushes the second piston to move within a range of 1-2 mm.

7. The anti-overflow structure for injection molding according to claim 6, characterized in that: The cylinder body is provided with a gear structure, which limits the first piston so that the first piston has a movement range of 1-2 mm between the gear structure and the top of the cylinder body.

8. The injection molding glue overflow prevention structure according to claim 5, characterized in that: A first bulge is provided on the first piston, and the first bulge is used to push against the second piston.

9. The injection molding glue overflow prevention structure according to claim 8, characterized in that: A second bulge is provided on the side of the first piston away from the second piston, a concave avoidance structure is provided on the top of the cylinder body, and the second bulge is movably inserted into the avoidance structure.

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