A cylinder ejector and reset mechanism for injection molds

Abstract

The utility model discloses an oil cylinder ejection and reset mechanism of injection mold relates to injection mold technical field, and its technical scheme main points are: including movable template, oil cylinder, clamping plate, connecting column, fender, fixed screw, limit block, ejector pin plate and ejector pin bottom plate, through the telescopic control of oil cylinder of hydraulic system, realize the ejection and reset action of ejector pin plate, and the effect is that the traditional reset spring is replaced by oil cylinder drive, and the continuous stable thrust is provided by using hydraulic system, and the rigid limit of cooperation limit block thoroughly avoids the reset deficiency caused by spring elasticity fatigue, and the ejector pin plate is accurately retreated to the initial position every time, guaranteeing, and the radial swing and inclination of ejector pin plate are eliminated through the clamping plate and fender piston rod both sides plane of oil cylinder, the rotation of connecting column is limited, and the T type groove adaptive structure of connecting column and ejector pin plate is combined.

Description

Technical Field

[0001] This utility model relates to the field of injection mold technology, and more specifically, it relates to a hydraulic cylinder ejection and reset mechanism for an injection mold. Background Technology

[0002] In injection molding, the ejection and reset mechanism is a core functional component for achieving automated production of injection molds. Its performance directly determines the demolding quality, production efficiency, and mold lifespan. The core function of this mechanism is to reliably eject the molded plastic product and runner sprue from the cavity and core surfaces after mold opening, ensuring the product completely leaves the mold. Before mold closing, the ejection assembly must be precisely reset to its initial position to avoid interference with the fixed mold structure, providing a stable foundation for the next injection cycle.

[0003] Currently, the most common ejection method used in the industry is ejector pins (push rods). These ejector pins extend from the mold cavity through the linear motion of the ejector plate, directly contacting the product surface to complete demolding. Traditional ejector plates are often powered by the injection molding machine's built-in ejection cylinder, which is rigidly connected to the ejector plate via ejector rollers to achieve synchronous movement of the ejector pins. In ejection design, the principle of "avoiding surfaces and prioritizing strength" must be strictly followed—the ejector pin contact point should avoid the product's outer surface, prioritizing areas with high structural strength such as thicker walls or reinforcing ribs. This is especially important for thin-shell products, where even distribution of ejector pins is crucial to prevent excessive localized stress and product deformation. Simultaneously, the ejection stroke must be strictly controlled to "exceed the product height by 5-10mm" to ensure the product completely detaches from the mold cavity and prevents secondary sticking after demolding.

[0004] The reset function mainly relies on the coordinated action of the reset spring and the reset rod (return rod): the reset spring is installed between the ejector plate and the mold base plate. During the mold closing process, the moving mold pushes the ejector plate to compress the spring and store potential energy. After the mold opens, the spring releases its elastic force to drive the ejector plate to retract. The reset rod is fixed on the ejector plate. When the mold closes, the mechanical thrust of the fixed mold parting surface forces the ejector plate to reset, thus providing double protection for the ejector to retract to a non-interference position.

[0005] However, in injection molds for large products, deep cavity structures, or high-strength materials (which typically require large ejection forces and long ejection strokes), traditional ejection and reset mechanisms exhibit significant drawbacks, specifically: 1. Insufficient reset reliability: The reset spring is in a high-frequency compression-release cycle for a long time, which can easily cause elastic fatigue and attenuation, resulting in insufficient ejector plate retraction stroke. In severe cases, the ejector pin may not completely leave the cavity before the mold starts to close, causing rigid collision between the ejector pin and the fixed mold.

[0006] 2. Failure of mechanical fit accuracy: The fit clearance between the reset rod and the guide sleeve will gradually increase due to long-term dry friction, causing radial wobble of the ejector plate during movement; the surface of the reset rod is prone to scratches or corrosion due to insufficient lubrication, which further aggravates the loss of fit accuracy; the loosening of the limit pin will directly cause the ejector plate to tilt, resulting in uneven force on the ejector and deformation of the ejected product.

[0007] 3. Mold damage caused by structural design defects: Problems such as design deviations in the length of the reset rod (too long leading to premature force, too short leading to incomplete reset) and inconsistent heights of the limit pins can cause the ejector pin to make hard contact with the fixed mold cavity during mold closing, resulting in irreversible damage such as ejector pin bending and surface scratches on the cavity.

[0008] 4. Lack of synchronization of actions: The timing control of ejection and reset actions depends on the mechanical linkage of the injection molding machine. It is easy to cause asynchronous actions due to signal delay or deviation of the actuator response. Especially in unmanned production scenarios, if the ejector pin is not fully reset before the mold is closed, it may cause the scrapping of the entire mold and cause significant economic losses.

[0009] Therefore, in order to solve the above-mentioned technical problems, this application proposes a hydraulic cylinder ejection and reset mechanism for injection molds. Utility Model Content

[0010] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide a hydraulic cylinder ejection and reset mechanism for injection molds.

[0011] To achieve the above objectives, this utility model provides the following technical solution: a hydraulic cylinder ejection and resetting mechanism for an injection mold, comprising a moving template, a hydraulic cylinder, a clamping plate, a connecting column, a stop block, a fixing screw, a limit block, an ejector plate, and an ejector base plate, wherein the extension and retraction of the hydraulic cylinder are controlled by a hydraulic system to realize the ejection and resetting actions of the ejector plate; The hydraulic cylinder is fixedly installed on the moving template, and the piston rod of the hydraulic cylinder is connected to the ejector plate through a connecting column. The ejector plate is fixedly connected to the ejector base plate. The clamp is installed on the outside of the piston rod of the hydraulic cylinder to restrict the rotation of the piston rod. The stop block is fixed flush with the plane of the connecting column to limit the rotation of the connecting column and ensure that the fixing screws lock the connecting column and the ejector plate. The limiting block is installed on the moving template to limit the reset position of the ejector plate.

[0012] Preferably, the ejector plate is provided with a T-slot, and the connecting post is adapted to connect with the T-slot. The T-slot is formed by extending the ejector plate and the ejector base plate beyond the mold foot.

[0013] Preferably, the connecting end of the connecting column and the piston rod of the oil cylinder adopts a flange structure and is fixed by screws.

[0014] Preferably, the clamping plate has a U-shaped structure, and its inner side is in contact with the two side planes of the cylinder piston rod.

[0015] Preferably, the number of hydraulic cylinders is 2-4, symmetrically distributed on both sides of the moving template or at the four corners of the ejector plate.

[0016] Preferably, it also includes a limit switch, which is installed on the reset path of the ejector plate and electrically connected to the PLC control system of the injection molding machine, for detecting the reset signal of the ejector plate.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This utility model uses a hydraulic cylinder drive instead of a traditional return spring, utilizing a hydraulic system to provide continuous and stable thrust. Combined with the rigid limiting block, it completely avoids insufficient return caused by spring fatigue, ensuring the ejector plate accurately retracts to its initial position each time. The clamping plate holds the two sides of the cylinder piston rod, and the stop block restricts the rotation of the connecting column. The T-slot fitting structure between the connecting column and the ejector plate eliminates radial sway and tilting of the ejector plate. Simultaneously, a flange structure connects the cylinder piston rod and the connecting column, improving the impact resistance and wear resistance of the components. Combined with standardized machining of the limiting block, it avoids mold damage caused by dimensional deviations. The hydraulic signal from the cylinder is connected to the injection molding machine's PLC control system, achieving seamless integration of the ejection-reset action with the injection molding process. Real-time monitoring of the reset status via a limit switch solves the problem of action synchronization, effectively preventing the risk of mold scrap due to incomplete ejector reset in unmanned production. This effectively solves the problems in the background technology. 2. In this utility model, the T-slot extends beyond the mold foot, avoiding other components inside the mold and reserving sufficient space for the connection and movement of the connecting column and the ejector plate. The T-slot is adapted to the connecting column and, together with the stop block and fixing screw, can form a two-way constraint to prevent the connecting column from axial movement or radial displacement when under force, ensuring reliable power transmission. 3. The hydraulic signal of the oil cylinder in this utility model can be directly integrated with the PLC control system of the injection molding machine to achieve seamless connection between the ejection-reset action and the mold closing, injection and other processes, reduce manual intervention and improve the overall production efficiency by 10%-15%. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the present invention and form part of this application, illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the present invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the specific structure of the present utility model; Figure 2This is a schematic diagram of the overall structure of the hydraulic cylinder of this utility model in an injection mold; Figure 3 This is an exploded view of the hydraulic cylinder and accessories of this utility model.

[0019] In the diagram: 1. Moving template; 2. Hydraulic cylinder; 3. Clamping plate; 4. Connecting column; 5. Stop block; 6. Fixing screw; 7. Limit block; 8. Ejector plate; 9. Ejector base plate. Detailed Implementation

[0020] like Figure 1-3 As shown, this utility model provides a hydraulic cylinder ejection and reset mechanism for an injection mold. The hydraulic system provides continuous thrust, and the force is precisely controlled by adjusting the oil pressure to adapt to the ejection requirements of different materials and product weights, avoiding product sticking to the mold due to insufficient ejection force. Speed ​​and stroke are flexibly controlled; the hydraulic system can achieve stepless speed regulation during the ejection process (such as low-speed start, high-speed ejection, and final buffer). Combined with a displacement sensor, it can also precisely control the ejection stroke, making it particularly suitable for ejecting deep-cavity, thin-walled products, reducing ejector pin marks or deformation. When the cylinder 2 resets, it is rigidly connected to the ejector plate 8 via a piston rod. With the help of guide pillars, limit blocks 7, and other mechanical structures, the reset accuracy error can be controlled within ±0.05mm, avoiding interference between the ejector pin and the core, and reducing the risk of mold collision during mold closing. Compared to spring reset, hydraulic drive is more resistant to high-frequency reciprocating motion. Springs are prone to fatigue failure after long-term use (lifespan approximately 50,000-100,000 cycles), while the cylinder 2 can operate stably for over 1 million cycles under normal maintenance, making it suitable for mass production. The hydraulic signal of cylinder 2 can be connected to the PLC control system of the injection molding machine to realize the fully automatic connection between the ejection-reset action and injection, pressure holding, mold opening and other processes, reduce manual intervention and improve production cycle (such as shortening the cycle by 10%-15%). The specific structure is as follows: It includes a moving template 1, a hydraulic cylinder 2, a clamping plate 3, a connecting column 4, a stop block 5, a fixing screw 6, a limit block 7, an ejector plate 8, and an ejector base plate 9. The extension and retraction of the hydraulic cylinder 2 are controlled by a hydraulic system to realize the ejection and resetting actions of the ejector plate 8. The hydraulic cylinder 2 is fixedly installed on the moving platen 1, and the piston rod of the hydraulic cylinder 2 is connected to the ejector plate 8 through the connecting column 4. The ejector plate 8 is fixedly connected to the ejector base plate 9. The limit switch is installed on the reset path of the ejector plate 8. The ejector plate 8 is provided with a T-slot. The connecting column 4 is adapted to the T-slot. The T-slot is formed by extending beyond the mold foot through the ejector plate 8 and the ejector base plate 9. The T-slot extends beyond the mold foot, avoiding other components inside the mold (such as mold foot, support column, etc.), and reserving sufficient space for the connection and movement of the connecting column 4 and the ejector plate 8. The T-slot is adapted to the connecting column 4, and cooperates with the stop block 5 and the fixed plate 8. The set screw 6 forms a bidirectional constraint, preventing the connecting column 4 from axial movement or radial displacement under stress, ensuring reliable power transmission. Furthermore, the connection end between the connecting column 4 and the piston rod of the hydraulic cylinder 2 adopts a flange structure, which is fixed by screws. The flange structure increases the contact area between the two, making the connection force more uniform and avoiding deformation or damage to the connection part caused by local stress concentration. It is especially suitable for transmitting the large push force when the hydraulic cylinder 2 is driven. At the same time, the flange structure and screw fixing can form a rigid connection, ensuring efficient and stable power transmission, reducing gaps and shaking during the movement, and improving the accuracy of the push-out and reset actions. The clamping plate 3 is installed on the outside of the piston rod of the hydraulic cylinder 2. The clamping plate 3 has a U-shaped structure, and its inner side fits against the two side planes of the piston rod of the hydraulic cylinder 2. It is used to restrict the rotation of the piston rod of the hydraulic cylinder 2, so as to ensure that the axial thrust or pull of the piston rod can be stably transmitted to the connecting column 4 and the ejector plate 8, ensuring the accuracy and stability of the ejection and reset actions, while reducing the additional wear caused by rotation, and extending the service life of the hydraulic cylinder 2 and related components. It is especially suitable for large mold scenarios that require high frequency and high intensity movement.

[0021] The stop block 5 is fixed flat against the plane of the connecting column 4 to limit the rotation of the connecting column 4, ensure that the fixing screw 6 locks the connecting column 4 and the ejector plate 8, and prevent the connecting column 4 from rotating and causing the screws connecting it to the oil cylinder 2 to loosen. The limit block 7 is installed on the moving template 1 to limit the reset position of the ejector plate 8. It can provide a clear and unified mechanical limit reference for the reset of the ejector plate 8, ensuring that it can accurately stop at the same position each time it is reset, avoiding incomplete or excessive reset due to the stroke error of the oil cylinder 2 or the fluctuation of the hydraulic system, and effectively preventing interference and collision between the ejector and the fixed mold.

[0022] Working principle: After the injection molding machine completes the injection and holding pressure, the moving platen 1 separates from the fixed mold to open the mold. When the mold opens to the set distance, the injection molding machine control system sends an ejection command to the hydraulic system. The hydraulic system controls the oil cylinder 2 to enter the hydraulic system, causing the piston rod of the oil cylinder 2 to retract and generate a pulling force. This force is transmitted to the ejector plate 8 through the connecting column 4, which is fixed by a flange structure and screws, and drives the ejector plate 8 to move upward. The ejector plate 8 is connected to the ejector base plate 9, which in turn pushes the ejector pin or ejector block to eject the injection molded part from the mold cavity. The clamping plate 3 clamps the planes on both sides of the piston rod of the oil cylinder 2 to prevent it from rotating. The stop block 5 and the plane of the connecting column 4 are flat and fixed, which stably restricts the rotation of the connecting column 4 and ensures that the fixing screw 6 locks the connecting column 4 and the ejector plate 8. At the same time, it prevents the screws connecting the connecting column 4 to the oil cylinder 2 from loosening due to the rotation of the connecting column 4. For large or complex molds, the ejection balance can be ensured by installing oil cylinder 2 on both sides of the moving platen 1 to pull the ejection mechanism or by installing oil cylinder 2 at the four corners of the ejector plate 8 to push the ejection mechanism. During mold closing, the injection molding machine controls the oil cylinder 2 to supply oil, increasing the pressure inside the cylinder 2. The piston rod extends, generating thrust, which drives the ejector plate 8 to move downward. Under the blocking restriction of the limit block 7, the ejector returns to its initial position. At the same time, the limit switch installed on the mold senses when the ejection mechanism returns to its original position and transmits a signal to the injection molding machine (the injection molding machine's PLC control system). The injection molding machine then stops controlling the oil supply to the cylinder 2, and the cylinder 2 stops moving. Throughout the process, the power for the ejection and reset of the cylinder 2 comes from the injection molding machine's hydraulic system. By controlling the flow direction and pressure of the hydraulic oil (usually 8-14MPa), the extension and retraction of the piston rod of the cylinder 2 is achieved. This can provide more than 10 times the thrust of spring ejection, making it especially suitable for ejection of large molds or deep-cavity products. Furthermore, the hydraulic signal of the cylinder 2 can be directly integrated with the injection molding machine's PLC control system, achieving seamless connection between the ejection-reset action and the mold closing, injection, and other processes, reducing manual intervention and improving overall production efficiency by 10%-15%.

[0023] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model in any way. Those skilled in the art can readily implement this utility model based on the accompanying drawings and the above description. However, any modifications, alterations, or equivalent variations made by those skilled in the art without departing from the scope of the utility model's technical solution, utilizing the disclosed technical content, are considered equivalent embodiments of this utility model. Furthermore, any equivalent changes, alterations, or variations made to the above embodiments based on the essential technology of this utility model are still within the protection scope of this utility model's technical solution.

Claims

1. A hydraulic cylinder ejection and resetting mechanism for an injection mold, characterized in that: It includes a moving template (1), a hydraulic cylinder (2), a clamping plate (3), a connecting column (4), a stop block (5), a fixing screw (6), a limit block (7), an ejector plate (8), and an ejector base plate (9). The extension and retraction of the hydraulic cylinder (2) are controlled by the hydraulic system to realize the ejection and resetting action of the ejector plate (8). The oil cylinder (2) is fixedly installed on the moving template (1), and the piston rod of the oil cylinder (2) is connected to the ejector plate (8) through the connecting column (4). The ejector plate (8) is fixedly connected to the ejector base plate (9). The clamp (3) is installed on the outside of the piston rod of the oil cylinder (2) to restrict the rotation of the piston rod of the oil cylinder (2); The stop block (5) is fixed to the plane of the connecting column (4) to restrict the rotation of the connecting column (4) and ensure that the fixing screw (6) locks the connecting column (4) and the ejector plate (8). The limiting block (7) is installed on the moving template (1) to limit the reset position of the ejector plate (8).

2. The hydraulic cylinder ejection and resetting mechanism for an injection mold according to claim 1, characterized in that: The ejector plate (8) is provided with a T-slot, and the connecting post (4) is adapted to connect with the T-slot. The T-slot is formed by extending beyond the mold foot through the ejector plate (8) and the ejector base plate (9).

3. The hydraulic cylinder ejection and resetting mechanism for an injection mold according to claim 1, characterized in that: The connecting column (4) and the piston rod of the oil cylinder (2) are connected by a flange structure and are fixed by screws.

4. The hydraulic cylinder ejection and resetting mechanism for an injection mold according to claim 1, characterized in that: The clamp (3) has a U-shaped structure, and its inner side is in contact with the two side planes of the piston rod of the oil cylinder (2).

5. The hydraulic cylinder ejection and resetting mechanism for an injection mold according to claim 1, characterized in that: The number of oil cylinders (2) is 2-4, symmetrically distributed on both sides of the moving template (1) or at the four corners of the ejector plate (8).

6. The hydraulic cylinder ejection and resetting mechanism for an injection mold according to claim 1, characterized in that: It also includes a limit switch, which is installed on the reset path of the ejector plate (8) and electrically connected to the PLC control system of the injection molding machine, and is used to detect the reset signal of the ejector plate (8).

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