Insert positioning mechanism, insert positioning method and injection mold

Abstract

The invention discloses an insert positioning mechanism, an insert positioning method and an injection mold. The insert positioning mechanism comprises a positioning piece, an elastic piece and a limiting structure. The positioning piece is assembled in the mold body, and the lower end face of the positioning piece is provided with an abutting area and a guide face gradually away from the insert. The elastic piece exerts pretightening force to enable the abutting area to abut against the insert. During injection molding, the melt entering the gap between the guide surface and the insert generates an upward component force and a downward component force. When the upward component force is not larger than the pre-tightening force, the positioning piece and the downward component force jointly restrain the insert. And when the upward component force is larger than the pre-tightening force, the positioning piece retreats to the limiting structure to be separated from the insert, so that the injection molding melt completely wraps the insert, and the downward component force continuously restrains the insert. Dynamic balance of fluid force and mechanical force is utilized, the receding time of the positioning piece is accurately controlled, the insert is effectively prevented from shifting, and the upper surface of the insert is completely wrapped by injection molding melt.

Description

Technical Field

[0001] This invention relates to the field of injection molding mold technology, and more specifically to an insert positioning mechanism, an insert positioning method, and an injection mold. Background Technology

[0002] In injection molding, it is often necessary to embed metal or other material inserts inside plastic parts to enhance the local mechanical strength of the product or to achieve specific functions such as electrical conductivity or magnetic conductivity. Inserts are typically placed inside the mold cavity before mold closing. However, during the high-speed, high-pressure injection of molten metal into the mold cavity, the melt wavefront exerts a tremendous impact force on the inserts. Without effective positioning constraints, the inserts are highly susceptible to displacement, tilting, or even being swept away by the melt within the mold cavity, leading to the scrapping of the final molded product.

[0003] To prevent insert displacement, existing technologies typically use rigid ejector pins on the mold to clamp the insert. While this method is simple in structure and effectively secures the insert, after injection molding, the space occupied by the rigid ejector pins cannot be filled with plastic, leaving through holes or obvious indentations on the product surface. This fails to meet the appearance or insulation requirements that the insert surface needs to be completely covered by plastic.

[0004] To address the issue of overlap, some molds employ spring-loaded floating pins to position inserts. The principle is to use a spring to press the floating pin against the insert, and then, once the melt fills the mold cavity, the melt pressure pushes the floating pin back. However, this conventional floating structure has significant drawbacks in practical applications. When the melt just contacts the floating pin, the upward thrust of the melt often overcomes the spring preload prematurely, causing the floating pin to retract. At this point, the melt has not yet completely covered the insert surface, and the insert instantly loses its restraint and shifts under the impact of the melt. This structure makes it difficult to precisely coordinate the timing of the floating pin's retraction with the stability of the insert, resulting in extremely low yield rates when molding products with very thin plastic sections. Summary of the Invention

[0005] This invention provides an insert positioning mechanism, an insert positioning method, and an injection mold to solve the technical problem in the prior art that it is difficult to simultaneously ensure stable positioning of the insert and complete surface coverage during the insert injection molding process.

[0006] The insert positioning mechanism provided by this invention is applied to an injection mold to constrain the Z-axis displacement of an insert located at the bottom of the mold cavity, comprising: A positioning element is slidably assembled into the injection mold along the Z direction, and its lower end face has an abutment area and a guide surface; the guide surface extends from the abutment area to the outer edge of the lower end face and gradually moves away from the insert; An elastic element is configured to apply an axial preload toward the insert to the positioning element; The limiting structure is configured to limit the extreme position of the positioning member moving away from the insert along the Z direction; When the mold is closed and the injection melt has not been injected into the mold cavity, the elastic element drives the positioning element to press the abutment area against the upper surface of the insert; a guide gap that gradually expands from the abutment area toward the outer edge of the lower end face is defined between the guide surface and the upper surface of the insert. During the injection of the molten injection into the mold cavity, the molten injection entering the guide gap is guided by the guide surface to generate an upward component force acting on the positioning member and a downward component force acting on the insert. When the upward component force is not greater than the axial preload force, the downward component force and the positioning member together constrain the insert to the bottom of the mold cavity. As the pressure inside the mold cavity increases, when the upward component force is greater than the axial preload force, the positioning member moves along the Z direction to the position where it is stopped by the limiting structure, so that the lower end face disengages from the insert, so that the injection melt completely covers the upper surface of the insert, and the downward component force continues to constrain the insert to the bottom of the mold cavity.

[0007] Preferably, the lower end face is formed as a downwardly convex spherical surface, and the lowest point of the spherical surface defines the abutment area; the section of the spherical surface extending outward from the lowest point constitutes the guide surface.

[0008] Preferably, the positioning element is a T-shaped floating pin, including an upper flange and a lower rod; the injection mold has a relief cavity for accommodating the flange and a sliding hole for the rod to pass through.

[0009] Preferably, a floating gap is defined between the top wall of the clearance cavity and the upper surface of the flange, and the axial height of the floating gap is equal to the limit distance that the positioning member can move along the Z direction; the limiting structure includes the top wall of the clearance cavity.

[0010] Preferably, a spring hole is provided in the injection mold directly above the clearance cavity, and the elastic element is a compression spring housed in the spring hole, with the lower end of the compression spring pressing against the upper surface of the flange.

[0011] Preferably, a fitting micro-gap is defined between the rod and the wall of the sliding hole, and the radial dimension of the fitting micro-gap is smaller than the overflow threshold of the injection molten metal.

[0012] The present invention also provides an insert positioning method, implemented based on the insert positioning mechanism described in any of the above claims, comprising the following steps: S1. With the mold closed and the injection melt not yet injected into the mold cavity, the elastic element drives the positioning element to press the abutment area against the upper surface of the insert. S2. During the injection of the molten injection into the mold cavity, the molten injection entering the guide gap is guided by the guide surface, generating an upward component force acting on the positioning element and a downward component force acting on the insert. S3. When the upward component force is not greater than the axial preload force, the downward component force and the positioning member are used together to constrain the insert to the bottom of the mold cavity. S4. As the pressure inside the mold cavity increases, when the upward component force is greater than the axial preload force, the positioning member is driven by the upward component force to move along the Z direction to the position stopped by the limiting structure, so that the lower end face is disengaged from the insert, so that the injection melt completely covers the upper surface of the insert, and the downward component force is used to continuously constrain the insert to the bottom of the mold cavity.

[0013] The present invention also provides an injection mold, comprising: The mold body, which internally defines a cavity for placing inserts; and An insert positioning mechanism as described in any of the above is assembled in the mold body to constrain the Z-direction displacement of the insert located at the bottom of the mold cavity.

[0014] One or more technical solutions provided in this invention have at least the following technical effects or advantages: This invention utilizes the principles of fluid mechanics and the dynamic balance of mechanical forces. By setting a guide surface of a specific shape on the lower end face of the positioning component, the injection melt injected into the mold cavity is transformed into a power source to assist in positioning. In the initial stage of injection, the injection melt enters the guide gap and is squeezed and guided by the guide surface, generating a downward component force that presses against the insert. At this time, since the upward component force is not yet sufficient to overcome the axial preload of the elastic component, the positioning component maintains mechanical pressure on the insert. At the same time, in conjunction with the downward component force generated by the injection melt itself, a strong double constraint is formed on the insert, effectively preventing the insert from premature displacement under the impact of the melt wavefront.

[0015] As the filling process progresses and the pressure within the mold cavity continuously increases, the upward force acting on the positioning element increases and eventually overcomes the axial preload, driving the positioning element to automatically retract upwards. During and after the positioning element detaches from the insert, the injection melt already covering the insert continuously provides a stable and reliable downward force, taking over the subsequent clamping action from the positioning element and ultimately achieving complete coverage of the upper surface of the insert. This insert positioning mechanism does not rely on complex external hydraulic or pneumatic core-pulling systems; it achieves precise timing control of positioning and retraction solely based on fluid pressure changes during the injection molding process. Its simplified and reliable structure significantly improves the yield rate of insert injection molding, making it particularly suitable for insert overmolding processes with ultra-thin glue areas.

[0016] In addition, the present invention also provides an insert positioning method and injection mold based on the above-mentioned mechanism, which also have the above-mentioned beneficial effects, and can ensure the positional accuracy of the insert under complex flow field and obtain a plastic coating layer with complete appearance. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of the insert positioning mechanism provided in an embodiment of the present invention in the state of mold closing and before the injection melt is injected into the mold cavity; Figure 2 for Figure 1 The diagram shows the state of the insert positioning mechanism during the injection of molten metal into the mold cavity. Figure 3 for Figure 1 The diagram shows the state of the insert positioning mechanism after the injection melt is filled and overcomes the axial preload of the elastic element. Figure 4 for Figure 1 A magnified view of a portion of point A in the middle.

[0018] Explanation of reference numerals in the attached drawings: 10, positioning element; 11, lower end face; 12, abutment area; 13, guide surface; 14, flange; 15, rod; 20, elastic element; 30, insert; 40, flow guide gap; 50, mold body; 51, mold cavity; 511, injection melt; 52, clearance cavity; 53, sliding hole; 54, floating gap; 55, spring hole. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] See Figures 1 to 4As shown, this embodiment of the invention provides an injection mold and its insert positioning mechanism. The injection mold includes a mold body 50, and the interior of the mold body 50 defines a cavity 51 for placing an insert 30. The insert 30 can be a metal skeleton such as a die-casting part, stamping part, or machined part, which is placed at the bottom of the cavity 51 and is partially or completely covered by the injection melt 511 during the injection molding process. The insert positioning mechanism is assembled in the mold body 50 and is mainly used to reliably constrain the insert 30 in the Z-direction (i.e., the vertical direction perpendicular to the surface of the insert 30) throughout the entire injection filling process to prevent the insert 30 from shifting or flipping under the impact of high-pressure, high-frequency melt, while ensuring that the upper surface of the insert 30 can obtain a plastic coating layer of a set thickness.

[0022] The insert positioning mechanism mainly includes a positioning element 10 slidably mounted in the injection mold along the Z-direction and an elastic element 20 providing initial power to it. The positioning element 10 is typically made of wear-resistant and high-temperature resistant mold steel, such as H13 or SKD61, and its surface can be nitrided or titanium-plated to improve the sliding fit life. In this embodiment, the positioning element 10 is preferably a T-shaped floating pin structure, which includes a flange portion 14 at the upper end and a rod portion 15 at the lower end. Correspondingly, the mold body 50 has a space inside for accommodating and sliding the positioning element 10, specifically including a clearance cavity 52 for accommodating the flange portion 14 and a sliding hole 53 for the rod portion 15 to pass through with a clearance fit.

[0023] Furthermore, such as Figure 4 As shown, the lower end face 11 of the positioning member 10 is formed as a downwardly convex spherical structure. The central region at the bottom of this spherical structure defines an abutment area 12 for direct contact with the upper surface of the insert 30; while the smooth transition section extending outward from the abutment area 12 of the spherical structure constitutes a guide surface 13. In other alternative embodiments, the lower end face 11 may also be formed as a truncated conical surface or a stepped surface with a large radius chamfer, but compared to the spherical structure, it can provide the smoothest infinitely variable flow guide surface for the fluid, avoiding sudden changes in melt flow rate or turbulence caused by sharp angles or abrupt cross sections, thereby ensuring that the injection-molded melt 511 has a more uniform wavefront distribution upon entry.

[0024] The elastic element 20 is configured to apply an axial preload force toward the insert 30 to the positioning element 10. A spring hole 55 is provided in the mold body 50 directly above the clearance cavity 52. ​​The elastic element 20 is housed within the spring hole 55, and its lower end presses against the upper surface of the flange portion 14. The elastic element 20 is typically a helical compression spring. In alternative solutions, depending on the mold space and the required preload force, the elastic element 20 can be replaced with a disc spring assembly, a nitrogen spring, or a high-temperature polyurethane elastomer.

[0025] To precisely control the plastic coating thickness on the upper surface of the insert 30, the insert positioning mechanism also includes a limiting structure. Specifically, a floating gap 54 is provided between the top wall of the clearance cavity 52 and the upper surface of the flange 14. The axial height of this floating gap 54 is equal to the maximum upward movement distance of the positioning member 10 along the Z direction. In some specific scenarios applied to ultra-thin wall overmolding, the height of this floating gap 54 can be precisely set to approximately 0.25 mm. When the positioning member 10 floats up until the flange 14 is in contact with the top wall of the clearance cavity 52, the top wall of the clearance cavity 52 constitutes a limiting structure that prevents the positioning member 10 from continuing to retract. Meanwhile, in order to prevent the injection molten material 511 from overflowing along the rod 15 under high pressure, a fitting micro-gap is defined between the outer wall of the rod 15 and the wall of the sliding hole 53. The radial dimension of this fitting micro-gap is strictly controlled to be less than the overflow threshold of the injection molten material 511. For example, depending on the viscosity characteristics of the plastic raw material used (such as PC, ABS or PA), this micro-gap can be controlled between 0.01 mm and 0.02 mm, thereby achieving a dynamic balance between venting and preventing flash by utilizing the physical gap threshold.

[0026] The following is combined Figures 1 to 3 The embedding positioning method and dynamic working principle of the embodiments of the present invention are described in detail.

[0027] like Figure 1 As shown, in the initial state after the injection molding machine completes the mold closing action and before the injection melt 511 is injected into the mold cavity 51, the elastic element 20 is in a compressed state and releases the axial preload. This preload drives the positioning element 10 downward, causing the abutment area 12 of the lower end face 11 to press tightly against the upper surface of the insert 30. At this time, due to the upward contraction geometry of the guide surface 13, a guide gap 40 that gradually expands from the inside to the outside is naturally defined between the guide surface 13 and the upper surface of the insert 30. In this stage, the insert 30 is pressed against the bottom rigid support surface of the mold cavity 51 purely by mechanical preload.

[0028] like Figure 2As shown, during the injection molding process where the injection molding machine begins injection and the molten injection 511 is rapidly injected into the mold cavity 51, the high-temperature and high-pressure molten injection 511 first gathers and flows into the guide gap 40. In this microscopic flow field, the molten injection 511 is squeezed and guided by the guide surface 13, and under the action of fluid mechanics, it undergoes force decomposition, generating an upward component force perpendicular to the guide surface 13 of the positioning member 10, and a downward component force pressing against the upper surface of the insert 30. In the initial stage of filling, the area of ​​the melt entering the guide gap 40 is limited, and the upward component force generated is not greater than the axial preload provided by the elastic member 20. Therefore, the positioning member 10 remains in its original position, maintaining mechanical pressure on the insert 30; more importantly, at this time, the downward component force generated by the molten injection 511 itself begins to play a role, cooperating with the positioning member 10 to form a double pressing effect of fluid force and mechanical force superposition, completely eliminating the risk of slippage or warping of the insert 30 during the initial impact of the melt wavefront.

[0029] like Figure 3 As shown, as the filling process in the mold cavity 51 nears completion and the holding pressure stage arrives, the fluid pressure in the mold cavity 51 increases sharply. When the upward component force acting on the bottom of the spherical surface of the positioning member 10 continues to increase and finally overcomes the axial preload of the elastic member 20, the positioning member 10 is forcibly lifted by the injection molten material 511 and moves upward along the Z direction. When the flange portion 14 of the positioning member 10 abuts against the top wall of the clearance cavity 52, the positioning member 10 stops moving, at which point the lower end face 11 just disengages from the floating distance set by the insert 30. With the retraction of the positioning member 10, the injection molten material 511 quickly flows in and completely fills the central area vacated by the positioning member 10, achieving complete coverage of the upper surface of the insert 30. In this final state, since the mechanical pressure of the positioning member 10 has been removed, the stability of the insert 30 is completely transferred to the high-pressure injection molten material 511 covering it, using the continuously existing downward component force of the fluid to firmly constrain the insert 30 to the bottom of the mold cavity until molding and cooling.

[0030] The embodiments of the present invention resolve the inherent contradiction between "compression" and "encapsulation" in ultra-thin wall insert injection molding by coupling micro-geometric surface design with spring mechanical properties. This not only eliminates the need for complex external drive cylinders or hydraulic cylinders, but also enables adaptive switching of action timing by utilizing the melt's own flow state, greatly improving the mass production yield of precision structural parts and the reliability of equipment operation.

Claims

1. An insert positioning mechanism, applied to an injection mold to constrain the Z-direction displacement of an insert (30) located at the bottom of the mold cavity, characterized in that, include: The positioning element (10) is slidably assembled in the injection mold along the Z direction, and its lower end face (11) has an abutment area (12) and a guide surface (13); the guide surface (13) extends from the abutment area (12) to the outer edge of the lower end face (11) and gradually moves away from the insert (30). The elastic element (20) is configured to apply an axial preload toward the insert (30) to the positioning element (10); The limiting structure is configured to limit the extreme position of the positioning member (10) moving away from the insert (30) in the Z direction; When the mold is closed and the injection melt has not been injected into the mold cavity, the elastic element (20) drives the positioning element (10) to press the abutment area (12) against the upper surface of the insert (30); a guide gap (40) is defined between the guide surface (13) and the upper surface of the insert (30) and gradually expands from the abutment area (12) toward the outer edge of the lower end face (11). During the injection of the injection molten material into the mold cavity, the injection molten material entering the guide gap (40) is guided by the guide surface (13) to generate an upward component force acting on the positioning member (10) and a downward component force acting on the insert (30). When the upward component force is not greater than the axial preload force, the downward component force and the positioning member (10) together constrain the insert (30) to the bottom of the mold cavity. As the pressure inside the mold cavity increases, when the upward component force is greater than the axial preload force, the positioning member (10) moves along the Z direction to the position stopped by the limiting structure, so that the lower end face (11) is disengaged from the insert (30), so that the injection melt completely covers the upper surface of the insert (30), and the downward component force continues to constrain the insert (30) to the bottom of the mold cavity.

2. The insert positioning mechanism according to claim 1, characterized in that, The lower end face (11) is formed as a downwardly convex spherical surface, and the lowest point of the spherical surface defines the abutment area (12); the section of the spherical surface extending outward from the lowest point constitutes the guide surface (13).

3. The insert positioning mechanism according to claim 1, characterized in that, The positioning element (10) is a T-shaped floating pin, including a flange (14) at the upper end and a rod (15) at the lower end; the injection mold has a relief cavity (52) for accommodating the flange (14) and a sliding hole (53) for the rod (15) to pass through.

4. The insert positioning mechanism according to claim 3, characterized in that, A floating gap (54) is defined between the top wall of the clearance cavity (52) and the upper surface of the flange (14), and the axial height of the floating gap (54) is equal to the limit distance that the positioning member (10) can move along the Z direction; the limiting structure includes the top wall of the clearance cavity (52).

5. The insert positioning mechanism according to claim 4, characterized in that, A spring hole (55) is provided in the injection mold directly above the clearance cavity (52). The elastic element (20) is a compression spring housed in the spring hole (55), and the lower end of the compression spring presses against the upper surface of the flange (14).

6. The insert positioning mechanism according to claim 3, characterized in that, A fitting micro-gap is defined between the rod (15) and the wall of the sliding hole (53), the radial dimension of which is smaller than the overflow threshold of the injection molten metal.

7. An insert positioning method, characterized in that, Based on the insert positioning mechanism as described in any one of claims 1 to 6, the method includes the following steps: S1. When the mold is closed and the injection melt has not been injected into the mold cavity, the elastic element (20) drives the positioning element (10) so that the abutting area (12) presses against the upper surface of the insert (30); S2. During the injection of the injection molten material into the mold cavity, the injection molten material entering the guide gap (40) is guided by the guide surface (13), generating an upward component force acting on the positioning member (10) and a downward component force acting on the insert (30); S3. When the upward component force is not greater than the axial preload force, the downward component force and the positioning member (10) are used together to constrain the insert (30) to the bottom of the mold cavity; S4. As the pressure inside the mold cavity increases, when the upward component force is greater than the axial preload force, the positioning member (10) is driven by the upward component force to move along the Z direction to the position stopped by the limiting structure, so that the lower end face (11) is separated from the insert (30), so that the injection melt completely covers the upper surface of the insert (30), and the downward component force is used to continuously constrain the insert (30) to the bottom of the mold cavity.

8. An injection mold, characterized in that, include: The mold body (50) has a cavity (51) inside for placing the insert (30); as well as The insert positioning mechanism as described in any one of claims 1 to 6 is assembled in the mold body (50) to constrain the Z-direction displacement of the insert (30) located at the bottom of the mold cavity (51).

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