An injection mold

Abstract

The present invention discloses an injection mold, comprising a rotatable tooth shaft and a movable push plate, wherein the tooth shaft extends out of the push plate and is formed with a threaded portion at one end, and the product is injection molded on the threaded portion, and the push of the push plate and the rotation of the tooth shaft drive the product to move horizontally; the mold also comprises a limiter, which limits the stroke of the push plate so that the stroke of the push plate is less than the tooth profile height of the threaded portion. The injection mold described in the present invention is provided with a limiter to limit the pushing stroke of the push plate; thus, before the push plate is in place, the product is driven to move by the push of the push plate and the rotation of the tooth shaft; when the push plate is in place, only the rotation of the tooth shaft is used to rotate and unscrew the threads, thereby completely demolding; thus, during the demolding process, the situation in which the tooth profile push plate is subjected to force and is pulled and deformed is reduced, thereby reducing the quality of the threads on the plastic product.

Description

Technical Field

[0001] The invention belongs to the field of injection molding, and in particular relates to an injection mold. Background Art

[0002] Rotary screw-cutting molds use a push plate and a rotary screw-cutting thread (hereinafter referred to as a thread cutter) to simultaneously push the plastic product out of the mold. During the latter part of the thread-cutting action and when the last circle of threads (the tail thread) is ejected from the mold, the thread profile is easily deformed by the push of the push plate, affecting the thread quality of the plastic product. Summary of the Invention

[0003] In order to solve the problem of damage to the tail teeth during the demoulding process mentioned in the background art, the present invention provides an injection mold that prevents damage to the tail teeth by limiting the demoulding stroke.

[0004] To achieve the above object, the specific technical solution of the injection mold of the present invention is as follows:

[0005] An injection mold includes a rotatable tooth shaft and a movable push plate. The tooth shaft extends out of the push plate at one end to form a threaded portion. The product is injection molded on the threaded portion. The push of the push plate and the rotation of the tooth shaft drive the product to move horizontally. It also includes a limiter, which limits the stroke of the push plate so that the stroke of the push plate is less than the tooth profile height of the threaded portion.

[0006] Furthermore, the height of the tail teeth is equal to the difference between the stroke of the push plate and the tooth profile height of the threaded portion.

[0007] Furthermore, the limiting member includes a limiting screw, and the head of the limiting screw is used to abut against the push plate.

[0008] Furthermore, the limiting member includes a limiting block, and the limiting block is formed with a limiting portion extending to the moving path of the push plate.

[0009] Furthermore, the injection mold further includes a first elastic member and a second elastic member, the first elastic member pushes the push plate to separate, and the second elastic member pushes the push plate to move along the tooth axis.

[0010] Furthermore, the thrust provided by the first elastic member is greater than the thrust provided by the second elastic member.

[0011] Furthermore, the deformation x of the first elastic member, the deformation x of the second elastic member and the stroke S of the push plate before mold opening satisfy x <S<x。

[0012] Furthermore, the push plate is formed with a positioning protrusion, and the product is formed with a socket for inserting the positioning protrusion.

[0013] Furthermore, the height of the positioning protrusion is equal to the difference between the tooth profile height of the threaded portion and the stroke of the push plate.

[0014] Furthermore, the injection mold further includes a trough body; the push plate serves as an insert, and the push plate is sleeved in the trough body.

[0015] Furthermore, the side wall of the groove body is formed with an inner bevel, and the push plate is formed with an outer bevel on the outer periphery that fits the inner bevel; the side wall of the tooth shaft is formed with a conical surface, and the push plate is formed with a conical through hole that fits the conical surface.

[0016] The injection mold of the present invention has the following advantages: a limiter is provided to limit the pushing stroke of the push plate; thus, before the push plate is in place, the product is driven to move by the push of the push plate and the rotation of the tooth shaft; when the push plate is in place, only the rotation of the tooth shaft is used to rotate and unscrew the threads, thereby completely demolding the product; thus, during the demolding process, the situation in which the tooth-shaped push plate is subjected to force and is pulled and deformed is reduced, thereby reducing the quality of the threads on the plastic product. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structural state of the injection mold before demoulding of the present invention;

[0018] Figure 2 This is a schematic diagram of the elastic member and the limiting member before demoulding of the present invention;

[0019] Figure 3 This is a schematic diagram of the structural state of the injection mold after demoulding of the present invention;

[0020] Figure 4 This is a schematic diagram of the elastic member and the limiting member after demoulding of the present invention;

[0021] Figure 5 It is a schematic diagram of the positioning protrusion of the present invention.

[0022] Description of the marks in the figure:

[0023] 1. Moving mold fixing plate; 2. Moving mold plate; 21. Guide pillar; 22. Slot body; 23. Inner bevel; 24. Spring; 25. Glue; 3. Fixed mold plate; 4. Tooth axis; 41. Threaded portion; 42. Conical surface; 5. Push plate; 51. Limiting hole; 52. Positioning bump; 53. Outer bevel; 54. Conical through hole; 6. Limiting screw; 7. Limiting block; 71. Limiting portion; 8. Product; 81. Socket. DETAILED DESCRIPTION

[0024] In order to better understand the purpose, structure and function of the present invention, an injection mold of the present invention is further described in detail below with reference to the accompanying drawings.

[0025] like Figure 1 and Figure 2As shown, the injection mold of the present invention includes a movable platen 2 and a fixed platen 3. The movable platen 2 is mounted on a movable mold fixing plate 1. Before injection molding, the movable mold fixing plate 1 drives the movable platen 2 and the fixed platen 3 to close the mold and form a cavity, into which the raw material is injected for molding.

[0026] In order to form the screw threads on the inner wall of the product 8, a tooth shaft 4 is connected to the movable template 2 for transmission, and a threaded portion 41 is formed at the end of the tooth shaft 4 and extends into the mold cavity, so that screw threads are formed on the inner wall of the injection-molded product 8, and the product 8 is injection-molded on the threaded portion 41.

[0027] The movable mold plate 2 is equipped with a push plate 5, which is mounted on the outer surface of the threaded portion 41, exposing the threaded portion 41. The mold surface is set on the push plate 5. After the mold is closed, the mold surface on the push plate 5 and the mold surface on the fixed mold plate 3 are combined to form the above-mentioned mold cavity. During demolding, the movable mold fixed plate 1 drives the movable mold plate 2, the threaded portion 4, and the push plate 5 to move and separate from the fixed mold plate 3. The product 8 is now threadedly connected to the threaded portion 41. The push plate 5 is then driven to move along the threaded portion 4 and push the product 8 to move horizontally. The threaded portion 4 is synchronously driven to rotate, and its own rotation is converted into translational movement of the product 8. In other words, the push of the push plate 5 and the rotation of the threaded portion 4 drive the product 8 to move horizontally, thus removing the threads and demolding.

[0028] In order to make the push plate 5 move relatively along the tooth axis 4, four sets of guide pillars 21 are fixed to the movable template 2. The push plate 5 is provided with sliding holes for sleeves of the guide pillars 21, which serve as precise guiding and positioning structures for the push plate 5 to cooperate with the tooth axis 4 and the movable template 2.

[0029] In order to prevent the tail teeth of the product 8 from being damaged during the threading and demoulding process, the injection mold also includes a limiter, which is used to abut against the push plate 5 to limit the stroke of the push plate 5 along the tooth axis 4, so that the stroke of the push plate 5 is less than the tooth profile height of the threaded portion 41. The height of the tail teeth is equal to the difference between the stroke of the push plate 5 and the tooth profile height of the threaded portion 41. Therefore, when the push plate 5 abuts against the limiter, part of the product 8 is still connected to the threaded portion 41. In this way, during the threading process, multiple turns of thread share the force between the threaded portion 41 and the threaded portion, preventing damage to the thread teeth, especially the tail teeth that are subjected to the greatest force. Finally, continue to rotate the tooth axis 4 to translate the product 8, and the product 8 and the push plate 5 are separated, completing the demoulding.

[0030] In actual application, the number of threads required to hold the threaded shaft 4 in place to resist the elastic force and prevent the threads from being damaged requires fine-tuning the limit stroke to find a balance point based on the state of the product 8 during the on-site trial mold. Therefore, the position of the limiter relative to the push plate 5 is adjusted to adjust the limit distance and ensure the quality of the thread profile of the product 8. Without damaging the threads, when the push plate 5 and the limiter abut, only the tail thread of the product 8 is threadedly connected to the threaded portion 41, that is, only one rotation is required to demold the product 8, which is relatively convenient.

[0031] Specifically, the limiting member includes a limiting screw 6. The push plate 5 is provided with a limiting hole 51 through which the limiting screw 6 passes. The head of the limiting screw 6 can slide within the limiting hole 51, and the rod portion of the limiting screw 6 passes through the bottom of the limiting hole 51 and is threadedly connected to the moving template 2. When the head of the limiting screw 6 abuts against the bottom of the limiting hole 51 of the push plate 5, the push plate 5 is limited.

[0032] To prevent the limiting screw 6 from breaking, the limiting member further includes a limiting block 7. The limiting block 7 is bolted to the moving template 2, and the limiting block 7 is formed with a limiting portion 71 extending to the moving path of the push plate 5, thereby limiting the push plate 5.

[0033] In addition to the above situation, the limiting member can also adopt only the limiting block 7, or other structures with blocking functions, such as rods, bumps, etc.

[0034] To drive the push plate 5 to drive the product 8 to perform thread tapping demolding, the injection mold further includes an elastic member. The elastic member drives the push plate 5 to move along the tooth shaft 4, so that the product 8 performs thread tapping demolding. Specifically, the elastic member is clamped between the moving template 2 and the push plate 5. Thus, when the mold is opened, the fixed template 3 no longer presses the push plate 5, and the elastic member pushes out the push plate 5. The push plate 5 drives the product 8 to translate, and the tooth shaft 4 rotates synchronously, realizing thread tapping demolding.

[0035] The elastic member includes a first elastic member and a second elastic member. The first elastic member pushes the push plate 5 and the moving template away from each other, and the second elastic member pushes the push plate 5 to move along the tooth shaft 4. Therefore, the elastic coefficient of the first elastic member is much greater than that of the second elastic member, so that the thrust provided by the first elastic member is greater than the thrust provided by the second elastic member. Moreover, before the mold is opened, the deformation amount x1 of the first elastic member, the deformation amount x2 of the second elastic member, and the stroke S of the push plate 5 satisfy x1 < S < x2. Thus, when the mold is opened, under the action of the strong elasticity of the first elastic member and the weak elastic deformation of the second elastic member, a thrust is applied to push the push plate 5 loose, solving the problem that the injection mold is tightly pressed under high pressure during injection molding of the injection molding machine, and enabling the rotary thread tapping of the tooth shaft 4 to proceed smoothly. In the subsequent thread tapping demolding process, the second elastic member pushes the push plate 5 to perform.

[0036] Combined Figure 5 As shown, the push plate 5 is formed with a positioning bump 52, and the product 8 is formed with a socket 81 for the positioning bump 52 to insert, thereby fixing the plastic product 8, so that when the tooth shaft 4 rotates, the plastic product 8 is pushed away from the tooth shaft 4. At the same time, the height of the positioning bump 52 is equal to the difference between the tooth profile height of the thread portion 41 and the stroke of the push plate 5. When only the tail thread remains on the thread portion 41 after only the push plate 5 arrives, the height of the positioning bump 52 is the same as the axial height of the tail thread on the tooth shaft 4. When the tail thread rotates and unscrews by thread tapping, the plastic product 8 synchronously disengages from the positioning bump 52 and also disengages from the tooth shaft 4 and can automatically fall off, completing the injection molding process.

[0037] To facilitate the placement of the push plate 5, the movable platen 2 is formed with a groove 22; the push plate 5 serves as an insert, which is sleeved into the groove 22 of the movable platen 2. Compared with conventional structures, eliminating the mold frame push plate 5 structure can reduce one mold frame push plate 5. Because the integrated push plate 5 insert is only about 1 / 4 of the mold frame push plate 5's specifications, the mold is also lighter, and its corresponding limiting and guiding structures are simplified and lightweight. It also eliminates the need for the original mold frame push plate 5 and the precise positioning structure between the backing plate.

[0038] The sidewalls of the groove body 22 are formed with an inner bevel 23, and the outer periphery of the push plate 5 is formed with an outer bevel 53 that mates with the inner bevel 23. The sidewalls of the tooth axis 4 are formed with a conical surface 42, and the push plate 5 is formed with a conical through-hole 54 that mates with the conical surface 42. The threaded portion 41 extends from the conical through-hole 54. As a result, the push plate 5 is driven to move along the tooth axis 4, and the inner bevel 23 and outer bevel 53 disengage, and the conical surface 42 and conical through-hole 54 disengage. As a result, the mating surfaces of the push plate 5 are all inclined, allowing the push plate 5 to instantly disengage from the mating surfaces when ejecting, thereby reducing the ejection force. With a relatively small thrust, the push plate 5 can continue to push and complete the ejection. This small thrust reduces the force exerted by the push plate 5 on the molded part, ensuring the integrity and non-deformation of the molded part. The inclined mating surfaces also serve as a guide and positioning tool when the insert on the push plate 5 returns to its original position.

[0039] In order to facilitate understanding of the above scheme, the above structure is quantified below.

[0040] Example 1.

[0041] Combine Figures 1 to 4 As shown, the thread profile height, i.e., the total height from the starting thread to the ending thread, is 11.5 mm. The limit screw 6 serves as the primary limiting mechanism, limiting the travel of the push plate 5 to 10.5 mm. Consequently, when the screw threads are unscrewed and the push plate 5 is simultaneously pushed out, the push plate 5 is restrained when it reaches the screw end face and cannot be pushed further out. At this point, the product 8 still has approximately one full circle of threads attached to the threaded shaft 4, but is no longer subject to the thrust of the push plate 5, thus preventing damage to the thread profile.

[0042] The force of spring 24 at the bottom of the push plate 5 insert is calculated based on the weight of the push plate 5. A D10X50 rectangular coil spring 24 with a preload of 17.5mm is selected as the second elastic element. The thrust generated by the rotation of the threaded shaft 4 on the product 8 and the thrust of spring 24 are combined to push the push plate 5 out. The distance pushed out by the push plate 5 is less than the thread height. At the end of the thread, the rotation of the threaded shaft 4 is used to rotate the plastic part 8 out of the mold, completing the thread removal and demolding.

[0043] Since this embodiment utilizes compression, the deformation is essentially compression. Simultaneously, the first elastic member is a polyurethane foam 25. During mold opening, the strong elastic deformation of the polyurethane foam 25 assists in the threading action, applying a force to the push plate 5 to loosen the push plate 5. This resolves the problem of high pressure and mold compression during injection molding by the injection molding machine, allowing for smooth rotation of the threaded shaft 4. The polyurethane foam 25 is designed to compress 5mm, significantly less than the 11.5mm thread profile height from the start to the end of the threading. This ensures that during the initial unthreading phase, the majority of the threads of the plastic product 8 remain attached to the threaded shaft 4. This prevents the polyurethane foam 25 from forcefully pushing against the push plate 5, which could damage the threads due to only a few threads remaining on the shaft unable to overcome the force of the push plate 5.

[0044] In addition, the inner bevel is 23 degrees and the outer bevel is 53 degrees and the angle is 8 degrees, which can ensure the separation effect.

[0045] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. An injection mold, characterized in that: The invention comprises a rotatable tooth shaft (4) and a movable push plate (5), wherein one end of the tooth shaft (4) extending out of the push plate (5) is formed with a threaded portion (41), and the product (8) is injection molded on the threaded portion (41). The pushing of the push plate (5) and the rotation of the tooth shaft (4) drive the product (8) to move horizontally; the invention also comprises a limiter, which limits the stroke of the push plate (5) so that the stroke of the push plate (5) is less than the tooth profile height of the threaded portion (41); the push plate (5) is formed with a positioning convex point (52), and the product (8) is formed with a positioning convex point (53). The socket (81) is inserted into the point (52); the height of the positioning protrusion (52) is equal to the difference between the tooth profile height of the threaded portion (41) and the stroke of the push plate (5); it also includes a first elastic member and a second elastic member, the first elastic member pushes the push plate (5) to separate, and the second elastic member pushes the push plate (5) to move along the tooth axis (4); the thrust provided by the first elastic member is greater than the thrust provided by the second elastic member; before the mold is opened, the deformation variable x1 of the first elastic member, the deformation variable x2 of the second elastic member and the stroke S of the push plate (5) meet x1 <S<x2。 2. The injection mold according to claim 1, characterized in that The height of the tail teeth is equal to the difference between the stroke of the push plate (5) and the tooth profile height of the threaded portion (41).

3. The injection mold according to claim 1, characterized in that The limiting member comprises a limiting screw (6), and the head of the limiting screw (6) is used for abutting against the push plate (5).

4. The injection mold according to claim 1 or 3, characterized in that: The limiting member comprises a limiting block (7), and the limiting block (7) is formed with a limiting portion (71) extending to the moving path of the push plate (5).

5. The injection mold according to claim 1, wherein: It also includes a trough body (22); a push plate (5) as an insert, and the push plate (5) is sleeved in the trough body (22).

6. The injection mold according to claim 5, characterized in that The side wall of the groove body (22) is formed with an inner bevel (23), and the push plate (5) is formed with an outer bevel (53) on the outer periphery thereof, which is in contact with the inner bevel (23); the side wall of the tooth shaft (4) is formed with a conical surface (42), and the push plate (5) is formed with a conical through hole (54) in contact with the conical surface (42).

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