Polyurethane resin forming device

Abstract

The invention belongs to the technical field of polyurethane resin processing, and particularly relates to a polyurethane resin forming device which comprises a rack, an injection mold arranged on the rack, an injection device and a bubble removing device. The injection mold comprises a lower mold arranged on the rack and an upper mold arranged on the rack in a lifting manner; the injection device is arranged on the upper mold; the bubble removing device comprises a vacuum tank, and a stirring shaft is arranged in the vacuum tank; a charging barrel is further arranged on the rack, the vacuum tank is connected with the charging barrel, and the charging barrel is further connected with the injection device; an exhaust auxiliary box is arranged on the side face of the vacuum tank, the exhaust auxiliary box is externally connected with a negative pressure device, and an air hole is formed in the exhaust auxiliary box and can be in butt joint with an exhaust opening in the injection mold. Bubbles of a polyurethane resin liquid raw material are removed in the vacuum tank, then the polyurethane resin liquid raw material is conveyed into the charging barrel, then the polyurethane resin liquid raw material is conveyed into the injection device and injected into the injection mold through the injection device, and the exhaust auxiliary box can assist in exhausting air in the injection mold before injection and can assist in exhausting in the injection molding process to avoid the air hole defect of a product.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane resin processing technology, and specifically relates to a polyurethane resin molding apparatus. Background Technology

[0002] Polyurethane resin is a class of polymeric materials produced by the stepwise polymerization reaction of isocyanates and polyols. Its core characteristic is the presence of repeating urethane groups in its molecular structure. This structure endows it with a broad spectrum of properties, ranging from soft to hard and from elastic to rigid, making it one of the most widely used polymeric materials in industrial and consumer applications. Polyurethane injection molding is a highly efficient and automated mass production process for PU products. The core process involves rapidly injecting liquid PU raw materials, mixed under high pressure, into a sealed mold, where they then solidify through a chemical reaction. This process is particularly suitable for producing PU elastomers and rigid products with complex structures and high dimensional accuracy, and is widely used in the automotive, electronics, and medical fields.

[0003] In polyurethane resin injection molding, air bubbles are one of the most common and significantly harmful defects. Air bubble formation stems from problems in raw materials, processes, or mold design, and its impact extends to all aspects of product performance, appearance, lifespan, and safety. The most fundamental cause of air bubble formation is the inherent characteristics of the raw materials or improper pretreatment; essentially, gaseous impurities or reaction byproducts carried in the raw materials are introduced into the mold. Similarly, poor venting during injection can also lead to porosity defects in the product. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a polyurethane resin molding device that can effectively remove air bubbles from the raw material and achieve effective venting during the injection process, thereby solving the above-mentioned technical problems.

[0005] Technical solution: In order to achieve the above objectives, the present invention provides a polyurethane resin molding apparatus, comprising: a frame, an injection mold, an injection device, and a degassing device disposed on the frame; The injection mold includes a lower mold mounted on a frame and an upper mold mounted on the frame in a height-reducible manner, wherein the upper mold is located directly above the lower mold. The injection device is located on the upper mold, and the injection device can inject material into the mold cavity after the upper mold and lower mold are closed; The debubbling device includes a vacuum tank, and a stirring shaft is provided inside the vacuum tank; The frame is also equipped with a feeding device, which includes a material cylinder. The vacuum tank is connected to the material cylinder, and the material cylinder is also connected to an injection device to deliver material thereto. The vacuum tank is slidably mounted on the frame. An exhaust auxiliary box is provided on the side of the vacuum tank. The exhaust auxiliary box is connected to a negative pressure device. The exhaust auxiliary box is provided with air holes, which can be connected to the exhaust port on the injection mold.

[0006] Through the above technical solution, the polyurethane resin liquid raw material is degassed in a vacuum tank, then sent to a barrel for storage, and then sent to an injection device. It is then injected into the mold cavity of the injection mold through the injection device. The venting auxiliary box can help to expel air from the injection mold before injection and can help to vent air during the injection molding process to avoid product porosity defects.

[0007] Furthermore, a first motor is provided on the side of the vacuum tank, and the first motor is connected to a stirring shaft. The vacuum tank is connected to a material cylinder through a delivery pump. The first motor drives the stirring shaft to stir the liquid polyurethane resin in the vacuum tank. The bottom of the vacuum tank is provided with a sliding device, which includes a base plate, a set of guide rods on the base plate, and a drive cylinder between the guide rods. The bottom of the vacuum tank is mounted on the guide rods through a bracket and connected to the drive cylinder. When the drive cylinder is activated, the entire vacuum tank can slide on the guide rods under its drive, thereby realizing the docking and separation of the exhaust auxiliary box and the injection mold.

[0008] Furthermore, the material cylinder is equipped with a feeding drive cylinder, and the end of the feeding drive cylinder is equipped with a piston. The piston is located in the material cylinder. The feeding drive cylinder extends to drive the piston to press down, thereby pressing the liquid polyurethane resin into the injection device. Solenoid valves are installed at the connection points between the material cylinder and the vacuum tank and the injection device. The material cylinder is a metering cylinder, and the solenoid valves are used to control the on / off state of the two pipelines.

[0009] Furthermore, the lower mold is provided with an exhaust groove, and the air holes on the exhaust auxiliary box can be connected to the exhaust groove.

[0010] Furthermore, two sets of screws are rotatably mounted on the frame, a second motor is mounted on the top of the screws, and a mounting plate is mounted on the screws. The four corners of the mounting plate are engaged with the screws through threaded sleeves. The upper mold is located at the bottom of the mounting plate, and the injection device is located at the top of the mounting plate. The second motor drives the screws to rotate synchronously, and the mounting plate, which is threaded with the screws, can move up and down to realize the mold closing and opening operations.

[0011] Furthermore, the injection device includes an injection cylinder, a spiral pusher disposed inside the injection cylinder, a third motor disposed at the top of the injection cylinder, the third motor being connected to the spiral pusher, and polyurethane resin entering the injection cylinder being delivered to the injection port at its front end through the spiral pusher and injected out under a certain pressure. The injection cylinder has inlets on both sides, and the inlets are connected to the cylinder.

[0012] Furthermore, both the lower and upper molds are provided with cooling holes, and cooling water channels are evenly distributed in the cooling holes to ensure that the temperature of each area of ​​the mold is consistent, reduce shrinkage stress, ensure the dimensional accuracy of the product, and enable the product to solidify and set quickly.

[0013] Furthermore, the lower mold is mounted on the frame via a set of mold feet, and an ejection assembly is provided between the mold feet. The ejection assembly includes a liftable top plate and an ejector rod on the top plate, which can extend into the mold cavity to eject the product.

[0014] As can be seen from the above technical solution, the present invention has the following beneficial effects: 1. The present invention provides a polyurethane resin molding apparatus that degasses the polyurethane resin raw material before injection. By placing the raw material in a vacuum tank, the air bubbles in the raw material are broken and overflowed through a low-pressure environment. At the same time, stirring is applied to accelerate the expulsion of air bubbles, thereby reducing the possibility of air bubbles in the product from the source and improving product quality.

[0015] 2. The present invention also includes an venting auxiliary box, which is connected to a negative pressure device to extract air before or during injection. This reduces the air pressure inside the mold cavity, allowing the gas to be quickly discharged through the venting groove. This enables the resin to fill the mold cavity more smoothly, avoiding problems such as insufficient filling caused by gas obstruction. It also effectively reduces the generation of defects such as air bubbles. Furthermore, the movable and interlocking design of the venting auxiliary box can be matched with injection molds of different specifications. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a polyurethane resin molding apparatus according to the present invention; Figure 2 This is a partial view of a polyurethane resin molding apparatus according to the present invention.

[0017] In the diagram: 1-frame, 11-screw, 12-second motor, 13-mounting plate; 2-Injection mold, 21-Lower mold, 22-Upper mold, 23-Ventilation groove; 3-Injection device, 31-Injection cylinder, 32-Spiral pusher, 33-Third motor; 4-Deaerator, 41-Vacuum tank, 42-Stirring shaft, 43-First motor, 44-Transfer pump; 5-Feeding device, 51-Cylinder, 52-Feeding drive cylinder, 53-Piston; 6-Exhaust auxiliary box, 61-Air vent; 71-Base plate, 72-Guide rod, 73-Drive cylinder; 81-Top plate, 82-Top rod. Detailed Implementation

[0018] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0019] like Figure 1-2 As shown, a polyurethane resin molding apparatus includes: a frame 1, an injection mold 2, an injection device 3, and a degassing device 4 disposed on the frame 1. The injection mold 2 includes a lower mold 21 disposed on the frame 1 and an upper mold 22 disposed on the frame 1 in a height-reducible manner, wherein the upper mold 22 is disposed directly above the lower mold 21; The injection device 3 is mounted on the upper mold 22, and the injection device 3 can inject material into the mold cavity after the upper mold 21 and the lower mold 21 are closed. The debubbling device 4 includes a vacuum tank 41, and a stirring shaft 42 is provided inside the vacuum tank 41. The frame 1 is also provided with a feeding device 5, which includes a material cylinder 51. The vacuum tank 41 is connected to the material cylinder 51, and the material cylinder 51 is also connected to the injection device 3 to deliver materials thereto. The vacuum tank 41 is slidably mounted on the frame 1. The side of the vacuum tank 41 is provided with an exhaust auxiliary box 6. The exhaust auxiliary box 6 is externally connected to a negative pressure device. The exhaust auxiliary box 6 is provided with an air hole 61, which can be connected to the exhaust port on the injection mold 2.

[0020] The vacuum tank 41 is equipped with a first motor 43 on its side, which is connected to the stirring shaft 42. The vacuum tank 41 is connected to the material cylinder 51 through a delivery pump 44. The bottom of the vacuum tank 41 is provided with a sliding device, which includes a base plate 71, a set of guide rods 72 on the base plate 71, and a drive cylinder 73 between the guide rods 72. The bottom of the vacuum tank 41 is supported by a bracket and connected to the drive cylinder 73.

[0021] Liquid polyurethane resin raw material is placed in a vacuum tank 41. The pressure inside the container is gradually reduced using the vacuum tank 41, typically maintaining a vacuum level between -0.08 MPa and -0.1 MPa. Under vacuum conditions, the gas pressure inside the bubbles is greater than the external pressure, causing the bubbles to expand and burst, releasing the gas. Simultaneously, the first motor 43 is activated, driving the stirring shaft 42. The stirring blades on the stirring shaft 42 agitate the raw material, accelerating the escape of the bubbles. Furthermore, to further enhance the degassing effect, a heating element can be installed inside the stirring shaft 42, heating while stirring. The solubility of the gas in the resin decreases with increasing temperature, promoting bubble precipitation. However, care must be taken to control the heating temperature to avoid excessively high temperatures that could cause reactions or changes in the properties of the raw material; generally, the temperature should be 10-20°C lower than the normal processing temperature.

[0022] The feed cylinder 51 is provided with a feeding drive cylinder 52, and the end of the feeding drive cylinder 52 is provided with a piston 53, which is located in the feed cylinder 51. Solenoid valves are provided at the connection points of the material cylinder 51 with the vacuum tank 41 and the injection device 3. The material cylinder 51 is a metering cylinder, which can realize quantitative injection and avoid material waste and excessive burrs.

[0023] To further optimize the design, the lower mold 21 is equipped with an venting groove 23, and the air holes 61 on the venting auxiliary box 6 can connect with the venting groove 23. During injection or molding, air is naturally present in the mold cavity, and the polyurethane resin may also generate gas during flow and curing. Using a negative pressure device connected to the mold venting groove 23 to extract air before or during injection reduces the air pressure in the mold cavity, allowing the gas to be quickly discharged through the venting groove 23. This enables the resin to fill the mold cavity more smoothly, avoiding problems such as insufficient filling due to gas obstruction, and effectively reducing defects such as air bubbles. It is important to note that the suction pressure and time of the negative pressure device must be precisely controlled according to factors such as the type of polyurethane resin, the shape and size of the product. Excessive suction pressure or time may cause resin to be sucked out of the venting holes or leave marks on the product surface; insufficient suction pressure or time will not achieve the desired venting effect. Meanwhile, in order to achieve a better connection between the air hole 61 on the exhaust auxiliary box 6 and the exhaust groove 23, a sealing connector can be provided at the end of the air hole 61 and the exhaust groove 23.

[0024] The frame 1 has two sets of screws 11 rotatably mounted on it. A second motor 12 is mounted on the top of each screw 11. A mounting plate 13 is mounted on each screw 11, and the four corners of the mounting plate 13 engage with the screws 11 via threaded sleeves. An upper mold 22 is located at the bottom of the mounting plate 13, and an injection device 3 is located at the top of the mounting plate 13. Furthermore, for products requiring higher pressure, which necessitates higher injection and holding pressures, the upper mold 22 can be driven by a hydraulic cylinder, and the screws can be replaced with guide rods.

[0025] Specifically, the injection device 3 includes an injection cylinder 31, a spiral pusher 32 disposed inside the injection cylinder 31, and a third motor 33 disposed on the top of the injection cylinder 31, the third motor 33 being connected to the spiral pusher 32; The injection cylinder 31 has inlets on both sides, and the inlets are connected to the material cylinder 51.

[0026] Specifically, both the lower mold 21 and the upper mold 22 are provided with cooling holes.

[0027] Specifically, the lower mold 21 is mounted on the frame 1 via a set of mold feet, and an ejection assembly is provided between the mold feet. The ejection assembly includes a liftable top plate 81 and an ejector rod 82 on the top plate 81. The ejector rod 82 can extend into the mold cavity to eject the product.

[0028] The polyurethane resin molding apparatus provided by this invention first places liquid polyurethane resin raw material into a vacuum tank 41 to create a vacuum environment. Simultaneously, a stirring shaft 42 stirs the raw material to remove air bubbles. Then, a delivery pump 43 sends the raw material to a barrel 51. Subsequently, the upper mold 22, driven by a second motor 12, moves downwards to cover the lower mold 21, completing the mold closing. The vacuum tank 41, driven by a drive cylinder 73, moves closer to the injection mold 2. The venting auxiliary box 6's vent 61 aligns with the venting groove 23, extracting air from the mold cavity of the injection mold 2. The raw material in the barrel 51 is pressed into the injection cylinder 31 by the feeding drive cylinder 42. A third motor 33 drives a spiral pusher 32 to rotate, pushing the raw material towards the injection port and injecting it into the mold cavity of the injection mold 2. During this process, the venting auxiliary box 6 assists in venting. After injection, pressure holding, venting, and cooling are performed. After the product is molded, the top plate 81 rises, driving the ejector rod 82 to eject the product.

[0029] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A polyurethane resin molding apparatus, characterized in that, include: The frame (1), the injection mold (2), the injection device (3) and the de-bubbling device (4) are mounted on the frame (1); The injection mold (2) includes a lower mold (21) disposed on the frame (1) and an upper mold (22) disposed on the frame (1) in a height-reducible manner, wherein the upper mold (22) is disposed directly above the lower mold (21); The injection device (3) is located on the upper mold (22), and the injection device (3) can inject materials into the mold cavity after the upper mold (21) and the lower mold (21) are closed; The debubbling device (4) includes a vacuum tank (41), and a stirring shaft (42) is provided inside the vacuum tank (41). The frame (1) is also provided with a feeding device (5), which includes a material cylinder (51). The vacuum tank (41) is connected to the material cylinder (51), and the material cylinder (51) is also connected to the injection device (3) to deliver materials therein. The vacuum tank (41) is slidably mounted on the frame (1). The side of the vacuum tank (41) is provided with an exhaust auxiliary box (6). The exhaust auxiliary box (6) is connected to a negative pressure device. The exhaust auxiliary box (6) is provided with an air hole (61). The air hole (61) can be connected to the exhaust port on the injection mold (2).

2. The polyurethane resin molding apparatus according to claim 1, characterized in that, The vacuum tank (41) is provided with a first motor (43) on its side. The first motor (43) is connected to the stirring shaft (42). The vacuum tank (41) is connected to the material cylinder (51) through a delivery pump (44). The bottom of the vacuum tank (41) is provided with a sliding device, which includes a base plate (71), a set of guide rods (72) on the base plate (71), and a drive cylinder (73) between the guide rods (72). The bottom of the vacuum tank (41) is mounted on the guide rods (72) through a bracket and connected to the drive cylinder (73).

3. The polyurethane resin molding apparatus according to claim 1, characterized in that, The feed cylinder (51) is provided with a feeding drive cylinder (52), and the end of the feeding drive cylinder (52) is provided with a piston (53), which is located in the feed cylinder (51). The material cylinder (51) is equipped with a solenoid valve at the connection point between it and the vacuum tank (41) and the injection device (3). The material cylinder (51) is a metering cylinder.

4. The polyurethane resin molding apparatus according to claim 1, characterized in that, The lower mold (21) is provided with an exhaust groove (23), and the air hole (61) on the exhaust auxiliary box (6) can be connected to the exhaust groove (23).

5. The polyurethane resin molding apparatus according to claim 1, characterized in that, Two sets of screws (11) are rotatably mounted on the frame (1). A second motor (12) is mounted on the top of the screws (11). A mounting plate (13) is mounted on the screws (11). The four corners of the mounting plate (13) are engaged with the screws (11) through screw sleeves. The upper mold (22) is located at the bottom of the mounting plate (13). The injection device (3) is located at the top of the mounting plate (13).

6. The polyurethane resin molding apparatus according to claim 1, characterized in that, The injection device (3) includes an injection cylinder (31) and a spiral pusher (32) disposed inside the injection cylinder (31). A third motor (33) is provided on the top of the injection cylinder (31), and the third motor (33) is connected to the spiral pusher (32). The injection cylinder (31) has inlets on both sides, and the inlets are connected to the material cylinder (51).

7. The polyurethane resin molding apparatus according to claim 1, characterized in that, Cooling holes are provided on both the lower mold (21) and the upper mold (22).

8. The polyurethane resin molding apparatus according to claim 1, characterized in that, The lower mold (21) is mounted on the frame (1) via a set of mold feet. An ejection assembly is provided between the mold feet. The ejection assembly includes a liftable top plate (81) and an ejector rod (82) on the top plate (81). The ejector rod (82) can extend into the mold cavity to eject the product.

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