A gas-driven core-pulling needle injection mold and an injection molding method

Abstract

The application discloses a kind of pneumatic core-pulling needle injection mold and injection molding method, the pneumatic core-pulling needle injection mold includes upper die plate assembly;Lower die plate assembly can be closed with upper die plate assembly and jointly define to form injection cavity and form with glue injection port;Core-pulling needle cavity is formed in lower die plate assembly and is communicated with injection cavity;Pneumatic core-pulling needle is implanted in core-pulling needle cavity and can be moved relative to lower die plate assembly;The core-pulling needle cavity includes pneumatic drive cavity, and the pneumatic core-pulling needle includes pneumatic drive section, the pneumatic drive section is contained in pneumatic drive cavity and is formed between the inner wall surface of pneumatic drive cavity and first gas inlet chamber and second gas inlet chamber, the first gas inlet chamber and second gas inlet chamber are independently arranged in front and back along the moving direction of pneumatic core-pulling needle;First gas inlet passage is formed on the lower die plate assembly and is communicated with the first gas inlet chamber;Second gas inlet passage is formed on the lower die plate assembly and is communicated with the second gas inlet chamber.

Description

Technical Field

[0001] This application relates to the field of mold making, and more particularly to a pneumatic core-pulling injection mold and injection method. Background Technology

[0002] Injection molds are precision tools used in injection molding processes. Their working principle involves injecting molten plastic material (such as ABS, PP, PC, nylon, etc.) under high pressure into the cavity of a mold. After cooling and solidification, the mold is opened to remove the molded product. However, some products require embedded parts (such as magnets or metal components) within the plastic material. In some cases, these embedded parts need to be mostly covered, with only a small portion of the plastic material exposed. Therefore, positioning these parts during injection molding is difficult, leading to part misalignment and quality issues.

[0003] Therefore, it is necessary to research a new injection mold to solve the above problems. Summary of the Invention

[0004] The purpose of this application is to address the shortcomings of existing technologies by proposing a pneumatic core-pulling injection mold and injection method.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] A pneumatic core-pulling injection mold, characterized in that it comprises:

[0007] Template components;

[0008] The lower mold assembly, together with the upper mold assembly, defines and forms an injection cavity with a glue injection port after the mold is closed in the vertical direction.

[0009] The core-pulling needle cavity is formed within the lower template assembly and communicates with the injection cavity;

[0010] A pneumatic core-pulling needle is implanted in the core-pulling needle cavity and can move relative to the lower template assembly in the vertical direction.

[0011] The core-pulling needle cavity includes a pneumatic drive cavity, and the pneumatic core-pulling needle includes a pneumatic drive section. The pneumatic drive section is housed within the pneumatic drive cavity and together with the inner wall surface of the pneumatic drive cavity, forms a first air inlet cavity and a second air inlet cavity. The first air inlet cavity and the second air inlet cavity are independently arranged at intervals along the moving direction of the pneumatic core-pulling needle.

[0012] A first air intake channel is formed on the lower template assembly and communicates with the first air intake cavity;

[0013] The second air intake channel is formed on the lower template assembly and communicates with the second air intake chamber;

[0014] When air is supplied to the first air intake chamber through the first air intake channel, the space of the first air intake chamber increases, the space of the second air intake chamber decreases, and the pneumatic core-pulling needle moves to one end along the up-down direction.

[0015] When air is supplied to the second air intake chamber through the second air intake channel, the space of the second air intake chamber increases, the space of the first air intake chamber decreases, and the pneumatic core-pulling needle moves to the other end in the up-down direction.

[0016] Furthermore, an annular protrusion is formed on the outer periphery of the pneumatic drive section at the middle position along the vertical direction, and the outer peripheral surface of the annular protrusion is in close contact with the inner wall surface of the pneumatic drive cavity.

[0017] The portion of the outer peripheral surface of the pneumatic drive section located at one end of the annular protrusion along the vertical direction forms the first air intake chamber between it and the inner wall surface of the pneumatic drive cavity.

[0018] The portion of the outer peripheral surface of the pneumatic drive section located at the other end of the annular protrusion along the vertical direction forms the second air intake chamber between it and the inner wall surface of the pneumatic drive cavity.

[0019] Furthermore, a first step is formed at one end of the pneumatic drive section along the vertical direction. When the pneumatic core-pulling needle moves to one end along the vertical direction, the step can abut against the first stop inner wall surface formed at the corresponding position of the core-pulling needle cavity.

[0020] A second step is formed at the other end of the pneumatic drive section along the vertical direction. When the pneumatic core-pulling needle moves to the other end along the vertical direction, the second step can abut against the inner wall surface of the second stop formed at the corresponding position of the core-pulling needle cavity.

[0021] Furthermore, the pneumatic drive section is an annular protrusion that bulges outward radially from the outer peripheral surface of a specific position of the pneumatic core-pulling needle, the first stepped portion is the end face of one end of the pneumatic drive section along the vertical direction, and the second stepped portion is the end face of the other end of the pneumatic drive section along the vertical direction.

[0022] Furthermore, the inner wall surface of the portion of the core-pulling needle cavity other than the pneumatic drive cavity is in close contact with the outer surface of the pneumatic core-pulling needle.

[0023] Furthermore, the lower template assembly includes a mold base plate, a lower template stacked on the mold base plate, and an inner mold insert embedded in the lower template;

[0024] The lower template has an inner mold receiving hole formed through it in the vertical direction. The inner mold insert is inserted into the inner mold receiving hole and the lower end of the inner mold insert in the vertical direction is supported on the mold foot plate.

[0025] The core-pulling needle cavity includes a first section hole formed through the inner mold insert in the vertical direction and a second section hole formed on the mold foot plate and communicating with the first section hole in the vertical direction.

[0026] The first segment hole includes a first segment hole away from the second segment hole along the vertical direction and a second segment hole close to the second segment hole. The diameter of the first segment hole is smaller than that of the second segment hole, and the diameter of the second segment hole is smaller than that of the second segment hole. The second segment hole and the second segment hole together form the pneumatic drive cavity.

[0027] The annular protrusion is located inside the second section hole and its outer peripheral surface is in close contact with the inner wall surface of the second section hole;

[0028] The inner wall surface of the first stop is formed by the step surface at the connection between the second segmented hole and the first segmented hole.

[0029] Furthermore, the inner wall surface of the second segmented hole is in close contact with the outer peripheral surface of the pneumatic drive section.

[0030] Furthermore, the second section hole is connected in the vertical direction at the end away from the first section hole to form a shrinkage section hole with an inner diameter smaller than the second section hole, and the inner wall surface of the second stop is formed by the step surface at the connection between the second section hole and the shrinkage section hole.

[0031] The second section hole and the tightening section hole penetrate the mold plate in the vertical direction.

[0032] Furthermore, the first air intake channel and the second air intake channel are formed on the mold plate, and respectively connect the outside to the second section hole in the transverse direction perpendicular to the vertical direction. The first air intake channel and the second air intake channel are staggered and spaced apart in the vertical direction.

[0033] To achieve the above objectives, this application also provides the following technical solutions:

[0034] An injection molding method using a pneumatic core-pulling injection mold as described in any of the above claims, the method comprising the following steps:

[0035] S1: The product part is implanted in the upper mold assembly, and the first end face and the part of the outer peripheral surface adjacent to the first end face of the product part interfere with and are fixed to the upper mold assembly;

[0036] S2: Inflate the second air intake channel, the space of the second air intake chamber increases, the space of the first air intake chamber decreases, and the pneumatic core-pulling needle moves to a set position along the up-down direction;

[0037] S3: Close the upper mold assembly and lower mold plate assembly containing the product parts. At this time, one end of the pneumatic core-pulling pin abuts against the second end face on the product part, which is opposite to the first end face.

[0038] S4: Molten plastic is injected into the injection cavity through the injection port until the injection cavity is filled and the set pressure value P is reached in the injection cavity;

[0039] S5: Inflate the first air intake channel, the space of the first air intake chamber increases, the space of the second air intake chamber decreases, and the core-pulling needle cavity moves to a specific position at the other end along the up-down direction. During this process, molten plastic liquid is simultaneously injected into the injection cavity through the injection port to maintain the set pressure value P in the injection cavity constant.

[0040] S6: After cooling, the upper and lower mold plate components open the mold and the injection molded product is removed, completing one injection molding process.

[0041] Compared with the prior art, the beneficial effect of this application is that the pneumatic core-pulling pin realizes the retraction of the core during the injection molding process and simultaneously achieves the purpose of completely encapsulating the lower end face of the product parts of the injection molded product. Attached Figure Description

[0042] Figure 1 This is a three-dimensional schematic diagram of the pneumatic core-pulling injection mold of this application, further demonstrating that the pneumatic core-pulling injection mold integrates the injection molded product.

[0043] Figure 2 This is a three-dimensional schematic diagram of the pneumatic core-pulling injection mold of this application, specifically showing a three-dimensional schematic diagram of the injection molded product after separation from the pneumatic core-pulling injection mold.

[0044] Figure 3 This is a three-dimensional exploded view of the pneumatic core-pulling injection mold of this application.

[0045] Figure 4 This figure mainly shows the pneumatic core-pulling pin of the pneumatic core-pulling pin injection mold of this application and the airflow channel that works with it. This figure shows the airflow channel in a concrete way. In order to show the specific positional relationship between the airflow channel and the pneumatic core-pulling pin, the dashed arrow line and the solid arrow line indicate the air intake direction.

[0046] Figure 5 This is a top view of the pneumatic core-pulling injection mold of this application.

[0047] Figure 6 It is self Figure 5 A cross-sectional view of the AA line, showing the state diagram when the pneumatic core-pulling needle moves up and down to the other end to the set position.

[0048] Figure 7 It is self Figure 5 The cross-sectional view of line AA shows the state of the pneumatic core-pulling needle as it moves up and down to a specific position.

[0049] Figure 8 yes Figure 6 or Figure 7 The diagram shows the state of the product after removing the pneumatic core-pulling pin and the injection-molded product. However, this diagram does not show the concrete airflow channel.

[0050] Figure 9 yes Figure 7 Enlarged view of the structure within the dashed box. Detailed Implementation

[0051] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0052] Please refer to the reference. Figures 1 to 9 The image shows a pneumatic core-pulling injection mold disclosed in this application, comprising an upper mold plate assembly, a lower mold plate assembly M, a pneumatic core-pulling pin 3, and an ejector pin assembly 4. The upper mold plate assembly and the lower mold plate assembly M are capable of mold closing and opening in the vertical direction (Y-axis direction). When the mold is closed, they jointly define an injection cavity (not shown), and a glue inlet is formed on the lower mold plate assembly (not shown, but may also be formed on the lower mold plate assembly M). A core-pulling pin cavity 20 communicating with the injection cavity is formed within the lower mold plate assembly M. (Refer to reference...) Figure 1 , Figure 3 and Figure 6 As shown, the core-pulling needle cavity 20 extends along the Y-axis direction (i.e., the vertical direction). The pneumatic core-pulling needle 3 is implanted in the core-pulling needle cavity 20 and can move relative to the lower template assembly M in the vertical direction.

[0053] Furthermore, the core-pulling needle cavity 20 includes a pneumatic drive cavity 21, and the pneumatic core-pulling needle 3 includes a pneumatic drive section 31 located closer to the lower end. The pneumatic drive section 31 is accommodated within the pneumatic drive cavity 21 and together with the inner wall surface of the pneumatic drive cavity 21, forms a first air inlet cavity 201 and a second air inlet cavity 202. The first air inlet cavity 201 and the second air inlet cavity 202 are independently and spaced apart along the moving direction of the pneumatic core-pulling needle 3 (that is, independently and spaced apart along the vertical direction). The lower template assembly M also has a first air inlet channel 2001 and a second air inlet channel 2002. The first air inlet channel 2001 communicates with the first air inlet cavity 201, and the second air inlet channel 2002 communicates with the second air inlet cavity 202. When air is supplied to the first air intake chamber 201 through the first air intake channel 2001, the space of the first air intake chamber 201 increases, the space of the second air intake chamber 202 decreases, and the pneumatic core-pulling pin 3 moves to one end along the vertical direction. When air is supplied to the second air intake chamber 202 through the second air intake channel 2002, the space of the second air intake chamber 202 increases, the space of the first air intake chamber 201 decreases, and the pneumatic core-pulling pin 3 moves to the other end along the vertical direction. This design utilizes a simple air path structure to achieve the pin retraction action (pin retraction action of the pneumatic core-pulling pin 3) during in-mold forming, realizing the injection positioning function without the need for additional holes for support.

[0054] Of course, to achieve better injection molding results, when the pneumatic core-pulling pin 3 is driven to its uppermost and lowermost extreme positions, the cavity space of both the first air inlet chamber 201 and the second air inlet chamber 202 is not zero. For example, when the pneumatic core-pulling pin 3 is driven to its uppermost extreme position, the cavity space of the first air inlet chamber 201 is still greater than zero, preventing the first air inlet chamber 201 from being completely closed with no space. This ensures that when the first air inlet channel 2001 or the second air inlet channel 2002 is inlet, the first air inlet chamber 201 or the second air inlet chamber 202 will not experience a sudden increase in volume, preventing the pneumatic core-pulling pin 3 from accelerating instantaneously. Ensuring smooth movement of the pneumatic core-pulling pin 3 ensures the stability of the injection molding process and the stability of the molten plastic injection, which is beneficial for controlling the pressure value P during the injection molding process (detailed below).

[0055] Please refer to the reference. Figures 6 to 9As shown in this embodiment, the pneumatic drive section 31 has an annular protrusion 311 formed on its outer periphery at the midpoint of its vertical direction. The outer peripheral surface of the annular protrusion 311 is in close contact with the inner wall surface of the pneumatic drive cavity 21. A first air intake cavity 201 is formed between the portion of the outer peripheral surface of the pneumatic drive section 31 at one end of the annular protrusion 311 and the inner wall surface of the pneumatic drive cavity 21. A second air intake cavity 202 is formed between the portion of the outer peripheral surface of the pneumatic drive section 31 at the other end of the annular protrusion 311 and the inner wall surface of the pneumatic drive cavity 21.

[0056] Furthermore, in order to achieve the stopping of the pneumatic core-pulling needle 3 in the vertical direction, a first step portion 312 is formed at one end of the pneumatic drive section 31 in the vertical direction (the upper end in the illustrated embodiment). When the pneumatic core-pulling needle 3 moves to one end in the vertical direction, the step portion 312 can abut against the first stopping inner wall surface 2011 formed at the corresponding position of the core-pulling needle cavity 20 to stop. Figure 6 The pneumatic core-pulling needle 3 is maintained in a set position. At this time, the first air intake chamber 201 still has a certain amount of space (that is, the space of the first air intake chamber 201 is still greater than zero). A second step portion 313 is formed at the other end of the pneumatic drive section 31 along the vertical direction. When the pneumatic core-pulling needle 3 moves to the other end along the vertical direction, the second step portion 313 can abut against the second stop inner wall surface 2021 formed at the corresponding position of the core-pulling needle cavity 20, thereby maintaining the pneumatic core-pulling needle 3 in a specific position. At this time, the second air intake chamber 202 also also has a certain amount of space (that is, the space of the second air intake chamber 202 is still greater than zero).

[0057] Please refer to the reference. Figures 1 to 9 As shown, in a preferred embodiment of this application, the pneumatic drive section 31 is an annular protrusion that bulges radially outward from the outer peripheral surface of the pneumatic core-pulling pin 3 at a specific position. The first stepped portion 312 is formed on the end face of one end of the pneumatic drive section 31 along the vertical direction. The second stepped portion 313 is formed on the end face of the other end of the pneumatic drive section 31 along the vertical direction.

[0058] In a preferred embodiment, the inner wall surface of the portion of the core-pulling needle cavity 20 excluding the pneumatic drive cavity 21 is tightly fitted with the outer surface of the pneumatic core-pulling needle 3. This ensures the stability of the pneumatic core-pulling needle 3 throughout its entire movement stroke and, more importantly, ensures airtightness. In a more preferred embodiment, a sealing ring (not shown) is fitted onto the outer peripheral surface of the portion of the pneumatic core-pulling needle 3 above the pneumatic drive section 31. The sealing ring is tightly fitted onto the inner wall surface of the corresponding pneumatic drive cavity 21 to ensure airtightness. Of course, in some embodiments, a limiting groove (not shown) can be formed on the outer peripheral surface of the pneumatic core-pulling needle 3 where the sealing ring is fitted for limiting and accommodating the sealing ring, or a limiting groove for limiting and accommodating the sealing ring can be formed on the inner wall surface of the corresponding pneumatic drive cavity 21. The main purpose of the sealing ring is to prevent pressurized gas filled into the first air inlet cavity 201 or the second air inlet cavity 202 from penetrating into the injection molding cavity and affecting the injection molding process.

[0059] Please refer to the reference. Figures 1 to 9 As shown, in a preferred embodiment of this application, the lower template assembly M includes a mold base plate M1, a lower template M2 stacked on the mold base plate M1, and an inner mold insert M3 embedded within the lower template M2. An inner mold receiving hole (not labeled) is formed through the lower template M2 along the vertical direction, and the inner mold insert M3 is implanted and received within the inner mold receiving hole. The lower end of the inner mold insert M3 along the vertical direction rests on the mold base plate M1.

[0060] The core-pulling pin cavity 20 includes a first segment hole A1 formed through the inner mold insert M3 in a vertical direction and a second segment hole A2 formed on the mold base plate M1 and communicating upward with the first segment hole A1 in a vertical direction. The first segment hole A1 includes a first segment hole A11 away from the second segment hole A2 in the vertical direction and a second segment hole A12 close to the second segment hole A2. The diameter of the first segment hole A1 is smaller than that of the second segment hole A12, and the diameter of the second segment hole A12 is smaller than that of the second segment hole A2. The second segment hole A12 and the second segment hole A2 together form the pneumatic drive cavity 21. The annular protrusion 311 is located inside the second segment hole A2, and its outer peripheral surface is in close contact with the inner wall surface of the second segment hole A2. The first stop inner wall surface 2011 is formed by the step surface at the connection between the second segment hole A12 and the first segment hole A11.

[0061] This design facilitates mold installation and enhances overall mold compatibility. When the C0 shape of the injection molded products is not significantly different, only the inner mold insert M3 needs to be replaced for universal applicability. Furthermore, it ensures that the cavity space of the first air inlet chamber 201 and the second air inlet chamber 202 always has space and is not zero. In a preferred embodiment, the inner wall surface of the second segmented hole A12 is in close contact with the outer peripheral surface of the pneumatic drive section 31. In a preferred embodiment, during the entire stroke of the pneumatic core-pulling pin 3 moving in the vertical direction, the lower end of the inner wall surface of the second segmented hole A12 remains in close contact with the outer peripheral surface of the pneumatic drive section 31 to prevent the cavity formed between the first step portion 312 and the first stop inner wall surface 2011 from affecting the pressure of the gas in the first air inlet chamber 201, thereby affecting the stable movement of the gas-driven pneumatic core-pulling pin 3.

[0062] Further, the second segment hole A2 is connected in the vertical direction at the end away from the first segment hole A1 to form a tightening segment hole A21 with an inner diameter smaller than the second segment hole A2. The second stop inner wall surface 2021 is formed by the step surface at the connection between the second segment hole A2 and the tightening segment hole A21. The second segment hole A2 and the tightening segment hole A21 penetrate the mold base plate M1 in the vertical direction. Further, in a preferred embodiment of this application, the first air intake channel 2001 and the second air intake channel 2002 are formed on the mold base plate M1, and respectively connect the outside to the second segment hole A2 in the horizontal direction perpendicular to the vertical direction. The first air intake channel 2001 and the second air intake channel 2002 are staggered and spaced apart in the vertical direction. During the entire vertical movement of the pneumatic core-pulling needle 3, the annular protrusion 311 is always located between the connection between the first air intake channel 2001 and the first air intake chamber 201 and the connection between the second air intake channel 2002 and the second air intake chamber 202. During the entire vertical movement of the pneumatic core-pulling needle 3, the annular protrusion 311 will not cross any one of the connection between the first air intake channel 2001 and the first air intake chamber 201 or the connection between the second air intake channel 2002 and the second air intake chamber 202.

[0063] The following is a brief introduction to the method of injection molding products using the pneumatic core-pulling pin injection mold of this application:

[0064] S1: Product part C is implanted in the upper mold assembly. The first end face C1 (i.e. the upper end face) of product part C and the part of the outer peripheral face C2 adjacent to the first end face C1 are fixed to the upper mold assembly by interference.

[0065] S2: Inflate the second air intake channel 2002, the space of the second air intake chamber 202 increases, the space of the first air intake chamber 201 decreases, and the pneumatic core-pulling needle 3 moves to a set position (topmost end) in the vertical direction.

[0066] S3: The upper mold assembly and lower mold plate assembly M, in which the product part C is implanted, are closed. At this time, one end of the pneumatic core-pulling pin 3 abuts against the second end face C3 (i.e., the lower end face) on the product part C, which is opposite to the first end face C1.

[0067] S4: Inject molten plastic into the injection cavity through the injection port until the injection cavity is full and the set pressure value P is reached.

[0068] S5: Inflate the first air intake channel 2001, increase the space of the first air intake chamber 201, decrease the space of the second air intake chamber 202, and move the core-pulling needle cavity 20 to a specific position along the up-down direction. During this process, molten plastic liquid is simultaneously injected into the injection cavity through the injection port to maintain the set pressure value P in the injection cavity constant.

[0069] S6: After cooling, the upper mold plate assembly and the lower mold plate assembly M open the mold and remove the injection molded product C0, completing one injection molding.

[0070] The pressure value P mentioned above is the pressure value within the injection port or the flow path of the molten plastic, which can be measured by a pressure sensor. The design scheme of this application uses a pneumatic core-pulling pin 3 to achieve pin retraction during the injection molding process and simultaneously achieve complete encapsulation of the lower end face of the product part C of the injection-molded product C0.

[0071] In this application, the injection-molded product C0 can be an injection-molded product with a magnet (i.e., product part C). A design challenge of this patent is that the magnet will float and shift when there is no positioning in the height direction during molding. Since adding positioning holes to the product is not feasible, an in-mold injection core-pulling structure is considered. This patent uses a simple structure to achieve the above function. The core-pulling pin 3 is made into a piston rod structure, controlled by an air circuit for its up-and-down movement. Before injection, it moves upward to position the magnet; when the molten plastic is quickly filled, the core-pulling pin 3 retracts to ensure complete filling of the product. The simple structure and fast response speed improve the production cycle without altering product requirements.

[0072] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A pneumatic core-pulling injection mold, characterized in that, include: Template components; The lower mold assembly, together with the upper mold assembly, defines and forms an injection cavity with a glue injection port after the mold is closed in the vertical direction. The core-pulling needle cavity is formed within the lower template assembly and communicates with the injection cavity; A pneumatic core-pulling needle is implanted in the core-pulling needle cavity and can move relative to the lower template assembly in the vertical direction. The core-pulling needle cavity includes a pneumatic drive cavity, and the pneumatic core-pulling needle includes a pneumatic drive section. The pneumatic drive section is housed within the pneumatic drive cavity and together with the inner wall surface of the pneumatic drive cavity, forms a first air inlet cavity and a second air inlet cavity. The first air inlet cavity and the second air inlet cavity are independently arranged at intervals along the moving direction of the pneumatic core-pulling needle. A first air intake channel is formed on the lower template assembly and communicates with the first air intake cavity; The second air intake channel is formed on the lower template assembly and communicates with the second air intake chamber; When air is supplied to the first air intake chamber through the first air intake channel, the space of the first air intake chamber increases, the space of the second air intake chamber decreases, and the pneumatic core-pulling needle moves to one end along the up-down direction. When air is supplied to the second air intake chamber through the second air intake channel, the space of the second air intake chamber increases, the space of the first air intake chamber decreases, and the pneumatic core-pulling needle moves to the other end along the up-down direction; The pneumatic drive section has an annular protrusion formed on the outer periphery at the middle position along the vertical direction, and the outer peripheral surface of the annular protrusion is in close contact with the inner wall surface of the pneumatic drive cavity. The first air intake chamber is formed between the portion of the outer peripheral surface of the pneumatic drive section located at one end of the annular protrusion in the vertical direction and the inner wall surface of the pneumatic drive cavity. The second air intake chamber is formed between the portion of the outer peripheral surface of the pneumatic drive section located at the other end of the annular protrusion in the vertical direction and the inner wall surface of the pneumatic drive cavity. The pneumatic drive section has a first step at one end along the vertical direction. When the pneumatic core-pulling needle moves to one end along the vertical direction, the step can abut against the first stop inner wall surface formed at the corresponding position of the core-pulling needle cavity. A second step is formed at the other end of the pneumatic drive section along the vertical direction. When the pneumatic core-pulling needle moves to the other end along the vertical direction, the second step can abut against the second stop inner wall surface formed at the corresponding position of the core-pulling needle cavity. The pneumatic drive section is an annular protrusion that bulges outward radially from the outer peripheral surface of a specific position of the pneumatic core-pulling needle. The first stepped portion is the end face of one end of the pneumatic drive section along the vertical direction, and the second stepped portion is the end face of the other end of the pneumatic drive section along the vertical direction.

2. The pneumatic core-pulling injection mold as described in claim 1, characterized in that: The inner wall of the core-pulling needle cavity, excluding the pneumatic drive cavity, is in close contact with the outer surface of the pneumatic core-pulling needle.

3. The pneumatic core-pulling injection mold as described in claim 1, characterized in that: The lower template assembly includes a mold base plate, a lower template stacked on the mold base plate, and an inner mold insert embedded in the lower template; The lower template has an inner mold receiving hole formed through it in the vertical direction. The inner mold insert is inserted into the inner mold receiving hole and the lower end of the inner mold insert in the vertical direction is supported on the mold foot plate. The core-pulling needle cavity includes a first section hole formed through the inner mold insert in the vertical direction and a second section hole formed on the mold foot plate and communicating with the first section hole in the vertical direction. The first segment hole includes a first segment hole away from the second segment hole along the vertical direction and a second segment hole close to the second segment hole. The diameter of the first segment hole is smaller than that of the second segment hole, and the diameter of the second segment hole is smaller than that of the second segment hole. The second segment hole and the second segment hole together form the pneumatic drive cavity. The annular protrusion is located inside the second section hole and its outer peripheral surface is in close contact with the inner wall surface of the second section hole; The inner wall surface of the first stop is formed by the step surface at the connection between the second segmented hole and the first segmented hole.

4. The pneumatic core-pulling injection mold as described in claim 3, characterized in that: The inner wall surface of the second segmented hole is in close contact with the outer peripheral surface of the pneumatic drive section.

5. The pneumatic core-pulling injection mold as described in claim 3, characterized in that: The second section hole is connected in the vertical direction at the end away from the first section hole to form a shrinkage section hole with an inner diameter smaller than the second section hole. The inner wall surface of the second stop is formed by the step surface at the connection between the second section hole and the shrinkage section hole. The second section hole and the tightening section hole penetrate the mold plate in the vertical direction.

6. The pneumatic core-pulling injection mold as described in claim 3, characterized in that: The first air intake channel and the second air intake channel are formed on the mold base plate, and respectively connect the outside to the second section hole in the transverse direction perpendicular to the vertical direction. The first air intake channel and the second air intake channel are staggered and spaced apart in the vertical direction.

7. A method for injection molding a product using a pneumatic core-pulling injection mold, comprising the pneumatic core-pulling injection mold as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1: The product part is implanted in the upper mold assembly, and the first end face and the outer peripheral surface of the product part adjacent to the first end face are fixed to the upper mold assembly by interference. S2: Inflate the second air intake channel, the space of the second air intake chamber increases, the space of the first air intake chamber decreases, and the pneumatic core-pulling needle moves to a set position along the up-down direction; S3: Close the upper mold assembly and lower mold plate assembly containing the product parts. At this time, one end of the pneumatic core-pulling pin abuts against the second end face on the product part, which is opposite to the first end face. S4: Molten plastic is injected into the injection cavity through the injection port until the injection cavity is filled and the set pressure value P is reached in the injection cavity; S5: Inflate the first air intake channel, the space of the first air intake chamber increases, the space of the second air intake chamber decreases, and the core-pulling needle cavity moves to a specific position at the other end along the up-down direction. During this process, molten plastic liquid is simultaneously injected into the injection cavity through the injection port to maintain the set pressure value P in the injection cavity constant. S6: After cooling, the upper and lower mold plate components open the mold and the injection molded product is removed, completing one injection molding process.

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