Injection molding mold for processing automobile parts

Abstract

The invention relates to an injection molding mold for automobile part machining, and relates to the technical field of injection molds. Comprising an upper mold, a lower mold and an injection molding structure, the upper mold and the lower mold are closed to form a cavity, the injection molding structure comprises a splitter plate, a melt runner communicated with the cavity is arranged in the splitter plate, and a plurality of runner heaters are arranged along the path of the melt runner. An oil cylinder is fixed on the splitter plate through a bracket, the length of the bracket enables the oil cylinder to be far away from the melt runner and the runner heater, and the temperature rise of hydraulic oil of the oil cylinder caused by heat of the runner heater is avoided; the mold further comprises a temperature sensor for monitoring the oil temperature of the oil cylinder, and a heater is arranged in the hot nozzle to maintain the glue melting temperature. The stable work of the oil cylinder is guaranteed by isolating a heat source, the action accuracy of the valve needle is improved, the problems of cold material blockage and the like are reduced, and the injection mold is suitable for efficient and high-quality injection molding of automobile parts.

Description

Technical Field

[0001] This application relates to the field of injection mold technology, and in particular to an injection molding mold for processing automotive parts. Background Technology

[0002] In the field of automotive parts injection molding, the stability and precision of the mold directly determine product quality and production efficiency. Automotive parts (such as interior parts and structural connectors) often have stringent requirements for dimensional accuracy, surface finish, and mechanical properties, which makes the flow state of the molten plastic, temperature stability, and the synchronization of valve needle movement during the injection molding process critical control points.

[0003] In traditional injection molding dies, the hydraulic cylinders that drive the valve needle are often directly mounted near the manifold or hot nozzle without effective heat insulation. To maintain the flowability of the molten plastic, the manifold and hot nozzle require continuous heating (typically maintained at 150-300℃). This heat acts directly on the hydraulic cylinder through conduction and radiation, easily causing the hydraulic oil temperature inside the cylinder to rise. When the oil temperature exceeds 60℃, the viscosity of the hydraulic oil decreases significantly, resulting in reduced pressure transmission efficiency and delayed response. This problem is particularly prominent in high-frequency injection molding production.

[0004] As the core component controlling the opening and closing of the nozzle, the valve needle's movement must be precisely synchronized with the injection molding machine screw's pushing action: the valve needle must open synchronously (or slightly ahead of time) when the screw pushes the glue to ensure that the molten glue smoothly enters the mold cavity; after injection, the valve needle must close promptly to prevent molten glue backflow or stringing. However, due to the influence of high temperature, the performance of the hydraulic oil in the cylinder deteriorates, which can cause a delay in the valve needle's opening. That is, the screw has already started pushing the glue, but the valve needle fails to move in time, causing the molten glue to be trapped inside the hot nozzle.

[0005] During the period when the molten adhesive is trapped, even if the heating nozzle continues to heat, its heat dissipation cannot completely offset the energy loss under high pressure, causing the temperature to drop rapidly. For example, the molten adhesive (such as PP or ABS) of a certain automotive plastic part, trapped in the heating nozzle for 3-5 seconds, can drop in temperature from 200℃ to below 170℃, and its viscosity increases by 2-3 times (plastic viscosity is extremely sensitive to temperature; for every 10℃ drop, viscosity can increase by 50%-100%). After cooling, the molten adhesive will change from a viscous flow state to a semi-solid or even solid state, forming a cold material.

[0006] The hazards of cold-pressed materials are manifested in many ways: 1. Gate blockage: The diameter of the hot nozzle gate is usually only 2-5mm. Due to its high hardness and irregular shape, the cold material is very easy to get stuck at the gate, which prevents the molten plastic from entering the cavity and causes a sudden increase in pressure inside the hot nozzle (which may exceed 200 bar). 2. Increased wear: Under high pressure, the new molten adhesive will forcibly flush the inner wall of the hot nozzle or push the cold material to grind the surface of the hot nozzle and valve needle, resulting in an increased clearance and causing problems such as molten adhesive leakage and flash on the product. Furthermore, the valve needle drive structure of traditional molds is mostly a direct rigid connection, lacking stroke limit design. This makes it prone to excessive or insufficient valve needle movement due to fluctuations in the hydraulic cylinder driving force. Excessive movement may cause damage to the ejector gate, while insufficient movement leads to incomplete closure of the ejector gate, further exacerbating melt leakage and cold material formation. At the same time, most traditional molds are not equipped with real-time oil temperature monitoring devices, making it impossible to provide early warning of hydraulic oil overheating. Often, problems are only addressed reactively after valve needle delays and cold material blockages occur, further increasing production losses.

[0007] Therefore, it is particularly important to redesign an injection molding structure that can overcome the problems of high temperature affecting the hydraulic cylinder, insufficient valve needle movement accuracy, and cold material hazards in automotive parts injection molds. Summary of the Invention

[0008] To address the aforementioned problems, this application provides an injection molding die for processing automotive parts.

[0009] An injection molding mold for processing automotive parts includes an upper mold, a lower mold, and an injection molding structure. The upper mold and the lower mold are closed to form a cavity. The injection molding structure includes a manifold, and the manifold has a melt flow channel communicating with the cavity. Multiple flow channel heaters are provided along the melt flow channel path. The manifold is fixed to a hydraulic cylinder by a bracket, and the length of the bracket keeps the hydraulic cylinder away from the melt flow channel and the flow channel heaters.

[0010] By adopting the above technical solution, the heat conduction and heat radiation of the flow channel heater can be blocked through the spatial isolation effect of the bracket, avoiding the decrease in viscosity of the hydraulic oil in the cylinder due to high temperature, ensuring the pressure transmission efficiency of the cylinder, and maintaining its driving stability.

[0011] Preferably, a hot nozzle is connected to the flow divider plate, the hot nozzle has an outlet that communicates with the melt flow channel, and a movable valve needle is provided inside the hot nozzle to control the opening and closing of the outlet.

[0012] By adopting the above technical solution, the timely opening and closing of the dispensing port can be achieved through the precise movement of the valve needle, avoiding molten backflow or stringing after injection molding, and ensuring the accuracy of the timing of molten plastic entering the cavity.

[0013] Preferably, the bracket is equipped with a connecting rod, which is rotatably connected to the bracket via shaft two. The two ends of the bracket are connected to shaft one and shaft three via bushings. Shaft one is fixed to the output shaft of the oil cylinder. Shaft three has a retainer on its bushing that engages with the valve needle. Shaft one and shaft three transmit driving force by swinging around shaft two via the connecting rod.

[0014] By adopting the above technical solution, the linear driving force of the hydraulic cylinder can be converted into the axial movement of the valve needle, thereby achieving stable power transmission, ensuring the synchronization between the valve needle action and the hydraulic cylinder drive, and improving control accuracy.

[0015] Preferably, the bracket has through grooves corresponding to shaft one and shaft three to form a first height groove and a second height groove, which limits the swing amplitude of shaft one and shaft three.

[0016] By adopting the above technical solution, the maximum stroke of the valve needle can be controlled, avoiding damage caused by excessive movement hitting the dispensing port, or insufficient movement causing the dispensing port to not close tightly, thus further improving the accuracy of the valve needle's movement.

[0017] Preferably, the hot nozzle has a built-in heater.

[0018] By adopting the above technical solution, the temperature of the molten adhesive inside the hot nozzle can be kept stable, preventing the molten adhesive from cooling down and solidifying before entering the cavity, ensuring that the molten adhesive is always in a good viscous flow state, and reducing the generation of cold material.

[0019] Preferably, the mold also includes a temperature sensor for monitoring the oil temperature in the hydraulic cylinder.

[0020] By adopting the above technical solution, the temperature of the hydraulic oil in the cylinder can be monitored in real time, and an early warning can be issued when the oil temperature approaches the critical value, so that operators can take cooling measures in advance to prevent the hydraulic oil performance from deteriorating and affecting the operation of the cylinder.

[0021] Preferably, the distance from the rotation center of the connecting rod to shaft three is the same as the distance to shaft one, and the length of the second height groove is the same as the length of the first height groove.

[0022] By adopting the above technical solution, the movement distance of the valve needle can be kept consistent with the extension and retraction distance of the cylinder piston rod, which is suitable for scenarios with high requirements for the symmetrical opening and closing amplitude of the dispensing port, and ensures the coordination of the action ratio.

[0023] Preferably, the distance from the rotation center of the connecting rod to shaft three is greater than the distance to shaft one, and the length of the second height groove is greater than the length of the first height groove.

[0024] By adopting the above technical solution, the gap between the valve needle and the outlet can be widened after the valve needle is fully opened, which can accommodate a small amount of cold material that may be generated, reduce the probability of cold material clogging the gate, and improve the smoothness of molten adhesive flow.

[0025] Preferably, the injection-molded structure is integrally embedded in the upper and lower molds.

[0026] By adopting the above technical solutions, the mold structure can be made more compact, the relative positions of each component can be stabilized, interference with the closing action of the upper and lower molds can be avoided, and the stability of the injection molding process can be guaranteed.

[0027] Preferably, the hydraulic cylinder is located outside the upper and lower molds.

[0028] By adopting the above technical solution, the air circulation environment outside the mold can be used to assist in heat dissipation, further reduce the temperature around the oil cylinder, reduce the impact of heat sources on hydraulic oil, and ensure the long-term stable operation of the oil cylinder.

[0029] In summary, this application includes at least one of the following beneficial technical effects: 1. By using measures such as heat source isolation brackets and temperature sensor monitoring, the working stability of the hydraulic cylinder is effectively guaranteed, the accuracy and synchronization of valve needle action are improved, and production problems caused by drive delay are reduced. 2. By incorporating a built-in heater in the hot nozzle, limiting the valve needle stroke, and expanding the clearance design, cold material generation and blockage are reduced, wear of the hot nozzle and valve needle and the risk of melt leakage are decreased, thus improving product quality. 3. The overall structure is adapted to the high-precision and high-efficiency injection molding requirements of automotive parts, enabling stable mass production and improving production efficiency and finished product qualification rate. Attached Figure Description

[0030] Figure 1 This is a perspective view of an embodiment of this application, mainly showing the assembly relationship of the upper mold, lower mold, and injection molding structure; Figure 2 This is a three-dimensional view of the lower mold, mainly showing the assembly relationship between the lower mold and the injection molding structure; Figure 3 This is a perspective view of the manifold, mainly showing the melt flow channel and the flow channel heater; Figure 4 This is a three-dimensional view of the injection-molded structure; Figure 5 This is a structural view of the bracket, connecting rod, and hydraulic cylinder shown in Example 1; Figure 6 This is a structural view showing axis one, axis two, and axis three in Example 1; Figure 7 It is a three-dimensional view showing the valve needle drive relationship; Figure 8 This is a view showing the connection relationship between the valve needle and the ferrule; Figure 9 This is a view showing the connection relationship between the valve needle and the ferrule; Figure 10 This is a structural view showing the first height groove and the second height groove in Embodiment 2; Figure 11 This is a structural view showing axis one, axis two, and axis three in embodiment 2; Figure 12 This is a perspective view showing the position of the hydraulic cylinder in Example 3.

[0031] Explanation of reference numerals in the attached drawings: 1. Manifold; 11. Melt channel; 2. Hydraulic cylinder; 3. Hot nozzle; 32. Valve needle; 4. Bracket; 41. Connecting rod; 42. Shaft 1; 43. Shaft 2; 44. Shaft 3; 441. Sleeve; 51. First height groove; 52. Second height groove; 5. Upper mold; 6. Lower mold; 7. Cavity; 8. Temperature sensor; 9. Runner heater. Detailed Implementation

[0032] The present application will be further described in detail below with reference to the accompanying drawings.

[0033] In the description of the invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, 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 the 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 limiting the invention.

[0034] Example 1 This application discloses an injection molding die for processing automotive parts, referring to... Figure 1-6 The system includes an upper mold 5, a lower mold 6, and an injection molding structure. When the upper mold 5 and lower mold 6 are closed, they form a cavity 7 for molding automotive parts. The injection molding structure is responsible for conveying molten plastic into the cavity 7. The injection molding structure includes a manifold 1, a runner heater 9, a bracket 4, a hydraulic cylinder 2, a hot nozzle 3, a valve needle 32, and related transmission components. These components work together to achieve stable delivery and precise control of the molten plastic. The injection molding structure is embedded in the upper mold 5 and lower mold 6. The corresponding positions of the upper mold 5 and lower mold 6 have pre-reserved mounting cavities that match the shape of the injection molding structure, ensuring that the components, after being embedded, will not interfere with the closing action of the upper mold 5 and lower mold 6, and can maintain a stable relative position.

[0035] The manifold 1 has at least one melt flow channel 11 inside, but the specific number of melt flow channels 11 can be designed according to the distribution of the cavity 7. One end of the melt flow channel 11 is connected to the hot nozzle 3, and the other end is directly connected to the cavity 7, forming the main path of melt from the supply end to the cavity 7.

[0036] Reference Figure 3 To prevent the molten adhesive from cooling and solidifying within the flow channel, multiple flow channel heaters 9 are evenly arranged inside the flow divider plate 1 along the path of the molten adhesive flow channel 11. The flow channel heaters 9 are electric heating rods, which continuously heat the adhesive to maintain a stable temperature within the molten adhesive flow channel 11, ensuring that the temperature within the molten adhesive flow channel 11 matches the optimal flow temperature of the molten adhesive, keeping the molten adhesive in a viscous flow state and ensuring smooth delivery.

[0037] Reference Figure 4 , Figure 5 , Figure 7 , Figure 8 and Figure 9 In this application, the hydraulic cylinder 2 is the power source for driving the valve needle 32, but its hydraulic oil is sensitive to temperature. Temperatures exceeding 60°C can easily lead to a decrease in viscosity and a reduction in pressure transmission efficiency. To prevent the heat from the flow channel heater 9 from affecting the hydraulic cylinder 2, a bracket 4 is used to achieve remote installation of the hydraulic cylinder 2.

[0038] Specifically, the bracket 4 is a rigid structure. One end of the bracket 4 is fixed to the flow divider 1, and the other end is fixedly connected to the cylinder body of the hydraulic cylinder 2. The length of the bracket 4 is designed according to the heat dissipation range of the flow channel heater 9, so that the installation position of the hydraulic cylinder 2 is far away from the melt flow channel 11 and the flow channel heater 9. By blocking heat conduction and heat radiation through spatial distance, the ambient temperature around the hydraulic cylinder 2 is effectively reduced, and the hydraulic oil temperature is prevented from rising.

[0039] In addition, a temperature sensor 8 is installed to monitor the real-time oil temperature of the hydraulic oil in cylinder 2. When the oil temperature approaches 60°C, the temperature sensor 8 can trigger the control system to issue an early warning, reminding the operator to take cooling measures to further ensure the operational stability of cylinder 2.

[0040] The hot nozzle 3 is the final channel for molten adhesive before it enters the mold cavity 7. One end of the hot nozzle 3 is connected to the manifold 1, and an internal channel communicating with the molten adhesive flow channel 11 is provided. The end of the channel is the outlet. The hot nozzle 3 has a built-in heater, which is a conventional heating coil wrapped around the outer wall or embedded in the inner wall of the hot nozzle 3. This heater is used to maintain the temperature of the molten adhesive inside the hot nozzle 3 and prevent the molten adhesive from cooling down due to heat dissipation before entering the mold cavity 7. The valve needle 32 is a slender rod-shaped structure, located in the channel inside the hot nozzle 3. Its end is adapted to the outlet and opens and closes the outlet by moving along the axial direction of the channel. In the closed state, the end of the valve needle 32 blocks the outlet; in the open state, the end of the valve needle 32 disengages from the outlet, forming a flow gap.

[0041] The bracket 4 has a connecting rod 41 inside. The middle part of the connecting rod 41 is rotatably connected to the bracket 4 via a shaft 43. The shaft 43 is fixed to the bracket 4, and the connecting rod 41 swings freely around the shaft 43. The bracket 4 has shaft holes at both ends, with bushings installed in the holes to reduce wear. Shafts 42 and 44 are respectively inserted into the bushings. One end of shaft 42 is fixedly connected to the output shaft of the cylinder 2 via a coupling, and moves synchronously with the piston rod's extension and retraction. One end of shaft 44 is connected to the bracket 4 via a bushing, and a retaining sleeve 441 is fixedly fitted onto the bushing at the other end. In this application, the retaining sleeve 441 is a clamp-type structure. The end of the valve needle 32 (i.e., the end furthest from the outlet) engages with the retaining sleeve 441.

[0042] When the piston rod of cylinder 2 retracts, it drives shaft 42 to move toward cylinder 2. Shaft 42 pushes connecting rod 41 to swing downward around shaft 43. The other end of connecting rod 41 drives shaft 44 to move upward, which in turn pulls valve needle 32 upward through sleeve 441, opening the dispensing port. Conversely, when the piston rod extends, the reverse transmission closes the dispensing port.

[0043] To ensure the accuracy of the valve needle 32's movement and prevent damage to the dispensing port or incomplete sealing due to excessive movement, through grooves are provided on the bracket 4 at positions corresponding to shaft 42 and shaft 44, forming a first height groove 51 for shaft 42 and a second height groove 52 for shaft 44. The length of the through groove is set along the swing trajectory direction of shaft 43, and the ends of shaft 42 and shaft 44 can slide within the through groove, with limiting surfaces formed at both ends of the through groove. When shaft 42 drives the connecting rod 41 to swing, the sliding range of shaft 42 and shaft 44 is restricted by the through groove, thereby limiting the maximum swing angle of the connecting rod 41 around shaft 43, and thus controlling the maximum stroke of the valve needle 32, ensuring accurate valve needle 32 movement and preventing wear or incomplete sealing of the dispensing port due to excessive movement. The distance from the rotation center of the connecting rod 41 (i.e., shaft 43) to shaft 44 is the same as the distance to shaft 42, and the length of the second height groove 52 is the same as the length of the first height groove 51. At this time, the travel distance of shaft 1 42 and shaft 3 44 is equal, and the travel distance of valve needle 32 is consistent with the extension and retraction distance of piston rod of oil cylinder 2. This is suitable for scenarios where the opening and closing amplitude of the dispensing port is required to be symmetrical.

[0044] The implementation principle of Example 1 is as follows: First, the upper mold 5 and the lower mold 6 close to form a cavity 7 for molding automotive parts. At this time, the injection molding structure is activated, and molten plastic enters the molten plastic flow channel 11 inside the manifold 1 from the supply end and begins to be conveyed to the cavity 7. The molten plastic flow channel 11 inside the manifold 1 is distributed along a preset path, and multiple flow channel heaters 9 continuously heat up to maintain the temperature inside the flow channel at the optimal flow temperature of the molten plastic, ensuring that the molten plastic is always in a viscous flow state and ensuring smooth conveying. The hydraulic cylinder 2 is installed at a position away from the manifold 1, using the spatial distance to block heat conduction and heat radiation, reducing the ambient temperature around the hydraulic cylinder 2. At the same time, the temperature sensor 8 monitors the hydraulic oil temperature of the hydraulic cylinder 2 in real time. When the oil temperature approaches 60°C, the linkage control system issues an early warning to further ensure the stability of the hydraulic cylinder 2. When molten plastic is conveyed to the cavity 7, the piston rod of the hydraulic cylinder 2 extends and retracts, driving the transmission components to move. The piston rod retracts, and shaft 42 moves towards the hydraulic cylinder 2 and pushes the connecting rod 41 to swing downward around shaft 43 on the bracket 4. The other end of the connecting rod 41 is connected to the shaft 44. The shaft 44 swings upward with the connecting rod 41. The ferrule 441 pulls the valve needle 32 upward along the internal channel of the hot nozzle 3, so that the outlet of the hot nozzle 3 opens. Conversely, when the piston rod extends, the transmission direction is opposite, and the valve needle 32 moves downward to close the outlet.

[0045] Example 2 Reference Figure 10 and Figure 11 To alleviate the problem of cold material blockage, the distance from the rotation center of the connecting rod 41 to the third shaft 44 is greater than the distance to the first shaft 42, and the length of the second height groove 52 is greater than the length of the first height groove 51.

[0046] The implementation principle of Example 2 is as follows: the travel stroke of shaft 3 44 is greater than that of shaft 1 42, which allows the gap between valve needle 32 and the outlet to be widened after the valve needle is fully opened. The widened gap can accommodate smaller cold materials, reducing the probability of cold materials getting stuck at the gate, while also reducing the flow resistance of the melt and reducing the degree to which cold materials are compacted at the outlet.

[0047] Example 3 Reference Figure 12 The oil cylinder 2 is located outside the upper mold 5 and the lower mold 6.

[0048] The implementation principle of Example 3 is as follows: the air circulation of the external environment can naturally reduce the working temperature of the oil cylinder 2. With the real-time monitoring of the temperature sensor 8, the performance of the hydraulic oil can be more effectively prevented from deteriorating due to high temperature.

[0049] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An injection molding die for processing automotive parts, comprising an upper die (5) and a lower die (6), wherein the upper die (5) and the lower die (6) have cavities (7) formed when closed, characterized in that, It also includes an injection molding structure, which includes a manifold (1), and the manifold (1) has at least one melt flow channel (11) which is connected to the cavity (7). Multiple flow channel heaters (9) are arranged inside the flow divider plate (1) along the path of the melt flow channel (11). A bracket (4) is fixedly arranged on the flow divider plate (1). One end of the bracket (4) is fixedly arranged on the flow divider plate (1), and the other end is fixedly arranged with a hydraulic cylinder (2). The length of the bracket (4) itself keeps the hydraulic cylinder (2) away from the melt flow channel (11) and the flow channel heaters (9) to avoid the heat of the flow channel heaters (9) causing the hydraulic oil temperature of the hydraulic cylinder (2) to rise.

2. The injection molding die for automotive parts processing according to claim 1, characterized in that, The flow divider plate (1) is also connected to a hot nozzle (3). The hot nozzle (3) is provided with an outlet for communicating with the melt flow channel (11). A valve needle (32) is provided inside the hot nozzle (3). The valve needle (32) moves in the channel opened inside the hot nozzle (3) to realize the opening and closing of the outlet.

3. The injection molding die for automotive parts processing according to claim 2, characterized in that, The bracket (4) is provided with a connecting rod (41), which is rotatably connected to the bracket (4) via shaft two (43). The two ends of the bracket (4) are respectively connected to shaft one (42) and shaft three (44) via bushings. Shaft one (42) is fixedly connected to the output shaft of the oil cylinder (2). A retainer (441) is fixedly sleeved on the bushing corresponding to shaft three (44). The end of the valve needle (32) is engaged with the retainer (441). The shaft one (42) and shaft three (44) transmit the driving force of the oil cylinder (2) to the valve needle (32) by the swing of the connecting rod (41) around shaft two (43).

4. The injection molding die for processing automotive parts according to claim 3, characterized in that, The bracket (4) has through grooves corresponding to the first shaft (42) and the third shaft (44) to form a first height groove (51) and a second height groove (52). The first height groove (51) and the second height groove (52) limit the swing amplitude of the first shaft (42) and the third shaft (44) along the second shaft (43) to ensure the accuracy of the valve needle (32) action.

5. The injection molding die for processing automotive parts according to claim 3, characterized in that, The hot nozzle (3) has a built-in heater to maintain the temperature of the molten adhesive inside the hot nozzle (3).

6. The injection molding die for processing automotive parts according to claim 1, characterized in that, It also includes a temperature sensor (8) for real-time monitoring of the oil temperature inside the cylinder (2).

7. The injection molding die for processing automotive parts according to claim 4, characterized in that, The distance from the rotation center of the connecting rod (41) to the third shaft (44) is the same as the distance from the rotation center of the connecting rod (41) to the first shaft (42), and the length of the second height groove (52) is the same as the length of the first height groove (51).

8. The injection molding die for processing automotive parts according to claim 4, characterized in that, The distance from the rotation center of the connecting rod (41) to the third shaft (44) is greater than the distance from the rotation center of the connecting rod (41) to the first shaft (42), and the length of the second height groove (52) is greater than the length of the first height groove (51) to widen the gap between the valve needle (32) and the hot nozzle (3) outlet after the valve needle (32) is fully opened.

9. An injection molding die for processing automotive parts according to any one of claims 1-8, characterized in that, The injection molding structure is integrally embedded in the upper mold (5) and the lower mold (6).

10. An injection molding die for processing automotive parts according to any one of claims 1-8, characterized in that, The oil cylinder (2) is located outside the upper mold (5) and the lower mold (6).

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