A leak-tight vacuum forming apparatus

Abstract

The application discloses a sealed vacuum forming device, and relates to the technical field of vacuum forming, which comprises a supporting plate, a lifting platform, an upper mold, a lower mold and a vacuum mold group. The lifting platform is slidingly installed on a guide rod on the supporting plate, the upper mold is installed below the lifting platform, and the lower mold is installed above a back pressure mechanism through a fixing table. The middle part of the back pressure mechanism is penetrated, and a plurality of triangular closed pieces are arranged in the back pressure mechanism to form a blocking part. The closed pieces are connected with a gear ring through a gear set, and the gear ring is driven by a cylinder. After the vacuum mold group is started, the negative pressure in a sealed chamber is increased, the cylinder piston rod is retracted to drive the shifting rod to drive the gear ring to rotate, all the closed pieces are driven to slide synchronously to the center through the gear set, the middle passage is completely closed, an independent pressure maintaining space is formed, and resin infiltrates glass fibers and is solidified and shaped in a constant pressure field. The back pressure mechanism adopts pure mechanical transmission, is high in reliability, and prevents product defects caused by pressure fluctuation.

Description

Technical Field

[0001] This invention relates to the field of vacuum forming technology, specifically a vacuum forming device that provides a seal and prevents leakage. Background Technology

[0002] Vacuum-assisted molding technology is widely used in the manufacture of interior parts for rail transit vehicles due to its high requirements for lightweight, structural strength and surface quality. For example, fiberglass components such as seat frames, armrest bases and air duct covers on high-speed railways and EMU trains are made by laying glass fiber in a mold, closing the mold and drawing a vacuum, and then injecting resin. Under negative pressure, the resin fully impregnates the fiber and cures it.

[0003] In existing equipment, after vacuuming is completed, the gas path between the molding cavity and the vacuum system still needs to be maintained. The gas pressure will fluctuate, and the continuous pressure difference will cause the resin to be sucked into the vacuum chamber during the injection process, resulting in resin waste. The molding chamber is also difficult to clean, and the product will have defects such as excessive porosity and reduced strength. Therefore, how to automatically cut off the gas path and establish a pressure-holding environment in a highly reliable manner after vacuuming has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a vacuum forming device that is sealed and leak-proof, so as to solve the technical problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a sealed and leak-proof vacuum forming device, comprising a support plate, a lifting platform, an upper mold, a lower mold, and a vacuum module. The support plate is disposed on one side of the vacuum module, the lifting platform is mounted on the support plate, a back pressure mechanism is disposed on the vacuum module, a fixed platform is disposed on the back pressure mechanism, the upper mold is disposed below the lifting platform, a mold coupling body is disposed in the middle of the upper mold, and the lower mold is mounted on the fixed platform. At the start of operation, the operator first accurately lays the glass fiber reinforced material inside the cavity of the lower mold to ensure uniform fiber distribution. Then, the control system starts the drive module, which drives the lifting platform to slide downward along a pair of guide rods until the upper mold and the lower mold are closed. At this time, the glass fiber is sealed in the forming cavity formed by the mold coupling body and the lower mold.

[0006] The back pressure mechanism has a through-hole in the middle. The back pressure mechanism is equipped with a pneumatic drive unit and a blocking unit. The pneumatic drive unit includes a cylinder and a gear ring. A lever is connected between the piston rod of the cylinder and the gear ring. The blocking unit includes several sealing plates. The sealing plates are evenly distributed in a circle and seal the through-hole. A gear set for transmitting power is provided between the gear ring and each sealing plate.

[0007] Furthermore, the back pressure mechanism is disc-shaped and consists of three layers: an upper layer, a middle layer, and a bottom layer. Each of the three layers has a through-hole in the middle, and an outer ring plate is provided around each layer. A sealed partition cavity is formed between the upper and middle layers, and a transmission cavity is formed between the middle and bottom layers. Several support rods are installed below the bottom layer. The gear set passes through the middle layer, and the gear ring is located in the transmission cavity. All the sealing plates are slidably installed in the sealed partition cavity. When the vacuum module is activated, the air in the sealed cavity is rapidly extracted, and the pressure in the sealed cavity drops and approaches a vacuum state, providing negative pressure adsorption conditions for subsequent resin injection.

[0008] Furthermore, the cylinder is arc-shaped and installed at the bottom of the bottom plate. A groove is formed on the outer ring plate, through which the lever connects to the piston rod. A connecting pipe connects the end of the cylinder furthest from the lever to the vacuum module. A spring is pre-installed inside the cylinder. Initially, the piston rod is held extended by the spring force. As the vacuum level in the sealed chamber increases, the internal air pressure of the cylinder, connected to the vacuum module via the connecting pipe, also decreases. When the negative pressure overcomes the spring force inside the cylinder, the piston rod retracts and displaces backward. This retraction causes the lever to slide within the groove, thereby driving the gear ring to rotate circumferentially.

[0009] Furthermore, each of the sealing plates is triangular in shape, with the right-angled sides of adjacent sealing plates contacting each other. Each sealing plate has a slot, and a limiting element is provided on the middle layer plate corresponding to each sealing plate. The slot in each sealing plate is slidably connected to the limiting element. The rotation of the gear ring drives all the pinions to rotate synchronously, and the large gear also rotates synchronously under the drive of the pinions. Under the guidance and constraint of the limiting element on the sealing plate, the rotational motion of the large gear is converted into the linear motion of the sealing plate sliding radially towards the center. Several sealing plates simultaneously and smoothly move towards the center until the right-angled sides of adjacent sealing plates contact each other and press together, completely sealing the through-passage in the middle of the back pressure mechanism. After the sealing plates in the back pressure mechanism are completely closed, in order to ensure that the sealing plates are not deformed or damaged due to excessive pressure drop caused by the continuous operation of the vacuum module, the vacuum module has a detection unit. The detection unit senses the pressure change and stops the operation of the vacuum module. At this time, the air passage between the sealed chamber and the vacuum module is cut off, forming an independent sealed pressure-holding space.

[0010] Furthermore, each gear set consists of a rotating shaft, a large gear, and a small gear. The rotating shaft passes through the middle layer plate, and the large gear and small gear are connected at both ends of the rotating shaft. The large gear is located in the sealed partition cavity, and the small gear is located in the transmission cavity.

[0011] Furthermore, each of the sealing plates has a toothed groove on its inclined side, and the large gear meshes with the toothed groove, while all the small gears mesh with the outer ring of the gear ring. After the fiberglass cools and sets, the vacuum module releases the negative pressure through its built-in pressure relief element. The negative pressure inside the cylinder disappears, and the piston rod returns to its original position under the elastic force of the spring. The lever drives the gear ring to rotate, driving all the sealing plates to retract in the radial centrifugal direction. The channel in the middle of the back pressure mechanism is reopened. Finally, the operator controls the lifting platform to rise through the drive module, separating the upper mold from the lower mold. The formed fiberglass product can then be smoothly removed from the lower mold, completing a full work cycle.

[0012] Furthermore, a pair of guide rods and a slide rail are integrally provided on the support plate. The lifting platform is slidably mounted on the pair of guide rods, and a drive module is provided on the lifting platform. The drive module is connected to the slide rail, and a resin feed pipe is connected to the mold assembly. The upper mold 5 and the mold assembly 6 are made of thin and tough material. Under stable pressure, the resin feed pipe begins to inject resin into the molding cavity. Under the auxiliary adsorption of negative pressure, the resin can quickly and evenly fill the gaps in the glass fibers, achieving full wetting and bonding. The upper mold 5 undergoes flexible deformation under the action of negative pressure. Through flexible deformation, the upper mold 5 fits the glass fibers more tightly, preventing the glass fibers from moving under the pressure of the resin, ensuring the consistency of the thickness of the fiberglass blank. The resin feed pipe automatically closes after the amount of material fed reaches the preset value to prevent excessive resin injection and overflow from the mold. During the subsequent cooling and shaping process, the pressure holding space maintains a constant pressure to ensure that the fiberglass completes curing under stable pressure, avoiding defects such as pores, shrinkage depressions, or uneven fiber distribution caused by pressure fluctuations, and improving the quality of the product.

[0013] Furthermore, rubber sealing rings and labyrinth sealing rings are provided at positions corresponding to the outer ring of the upper mold and the upper plate. A pair of rubber sealing rings are in sealing contact, and a pair of labyrinth sealing rings cooperate with each other. After the mold is closed, the pair of rubber sealing rings fit tightly together to form the first main seal, ensuring that the molding cavity is isolated from the outside atmosphere. The pair of labyrinth sealing rings around the rubber sealing rings also interlock to create multiple concave and convex tortuous channels. The molding cavity is connected to the vacuum module through the back pressure mechanism, becoming a sealed chamber. When the rubber sealing rings age or fail locally due to long-term operation, the gas changes its flow direction multiple times when passing through the multiple concave and convex tortuous grooves, and the pressure is reduced step by step to achieve back pressure. This still effectively prevents leakage and ensures that the molding area maintains the integrity of the seal during the curing cycle, providing a stable and reliable sealing guarantee.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention sets up a back pressure mechanism with pure mechanical transmission between the vacuum module and the lower mold. It uses the negative pressure of the molding cavity itself to drive the cylinder and gear set, automatically completing the physical cut-off of the air path without the need for solenoid valves or external signals. This fully mechanical structure is corrosion-resistant and interference-resistant in the resin volatilization atmosphere, and responds promptly and reliably. It effectively eliminates the problem of resin being sucked into the vacuum pipeline and significantly reduces the frequency of equipment maintenance.

[0015] After the air path is cut off, the closed sheet assembly in this invention establishes an independent pressure-holding space between the molding cavity and the vacuum module, so that the resin wets the glass fiber and cures it in a constant pressure field. This avoids defects such as pores, shrinkage depressions and uneven fiber distribution caused by pressure fluctuations, and improves the structural density and surface quality of fiberglass products. It is suitable for mass production of high-speed rail interior parts. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall appearance and structure of the present invention; Figure 2 This is a schematic diagram of the overall bottom view of the present invention; Figure 3 This is a schematic diagram of the lifting platform portion of the present invention; Figure 4 This is a schematic diagram of the lower mold part of the present invention; Figure 5 This is a schematic diagram of the mounting structure of the sealing sheet of the present invention; Figure 6 This is a schematic diagram of the mounting structure of the toothed ring of the present invention; Figure 7 This is a schematic diagram of the internal structure of the back pressure mechanism of the present invention.

[0017] In the diagram: 1. Support plate; 2. Guide rod; 3. Lifting platform; 4. Drive module; 5. Upper mold; 6. Mold assembly; 7. Lower mold; 8. Rubber sealing ring; 9. Labyrinth sealing ring; 10. Resin feed pipe; 11. Support frame rod; 12. Fixed platform; 13. Vacuum module; 14. Upper plate; 15. Middle plate; 16. Bottom plate; 17. Outer ring plate; 18. Slide groove; 19. Sealing plate; 20. Limiting component; 21. Large gear; 22. Small gear; 23. Gear ring; 24. Lever; 25. Cylinder; 26. Conductor pipe. Detailed Implementation

[0018] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figures 1-7 As shown, a leak-proof vacuum forming device includes a support plate 1, a lifting platform 3, an upper mold 5, a lower mold 7, and a vacuum module 13. The support plate 1 is located on one side of the vacuum module 13. The lifting platform 3 is mounted on the support plate 1. The vacuum module 13 is equipped with a back pressure mechanism, and a fixed platform 12 is mounted on the back pressure mechanism. The upper mold 5 is mounted below the lifting platform 3. A mold coupling body 6 is located in the middle of the upper mold 5. The lower mold 7 is mounted on the fixed platform 12. A pair of guide rods 2 and a slide rail are integrally mounted on the support plate 1. The lifting platform 3 is slidably mounted on the pair of guide rods 2. A drive module 4 is mounted on the lifting platform 3 and connected to the slide rail. A resin feed pipe 10 is connected to the mold coupling body 6. Rubber sealing rings 8 and labyrinth sealing rings 9 are provided at positions corresponding to the outer ring of the upper mold 5 and the upper plate 14. The pair of rubber sealing rings 8 are in sealing contact, and the pair of labyrinth sealing rings 9 cooperate with each other.

[0020] At the start of the operation, the operator first accurately lays the glass fiber reinforced material inside the cavity of the lower mold 7, ensuring uniform fiber distribution. Then, the control system activates the drive module 4, which drives the lifting platform 3 to slide downwards along a pair of guide rods 2 until the upper mold 5 and lower mold 7 close. At this point, the glass fiber is enclosed within the molding cavity formed by the mold coupling body 6 and the lower mold 7. After mold closing, a pair of rubber sealing rings 8 fit tightly together, forming the first main seal, ensuring the molding cavity is isolated from the outside atmosphere. A pair of labyrinth sealing rings 9 surrounding the rubber sealing rings 8 also interlock, creating multiple intersecting, tortuous channels. The molding cavity is connected to the vacuum module 13 via a back pressure mechanism, becoming a sealed chamber. When the rubber sealing rings 8 age or partially fail due to long-term operation, the gas changes its flow direction multiple times as it passes through the multiple intersecting, tortuous channels, gradually reducing the pressure and achieving back pressure. This effectively prevents leakage, ensuring the molding area maintains the integrity of the seal during the curing cycle, providing a stable and reliable sealing guarantee.

[0021] The back pressure mechanism has a through-hole in the middle. It contains a pneumatic drive unit and a blocking unit. The pneumatic drive unit includes a cylinder 25 and a gear ring 23. A lever 24 connects the piston rod of the cylinder 25 to the gear ring 23. The blocking unit includes several sealing plates 19, which are evenly distributed circumferentially to seal the through-hole. A gear set for power transmission is provided between the gear ring 23 and each sealing plate 19. The back pressure mechanism is disc-shaped and consists of three layers: an upper layer, a middle layer, and a bottom layer. All three layers have a through-hole in the middle. An outer ring plate 17 is also provided outside the three layers. A sealed partition cavity is formed between the upper layer plate 14 and the middle layer plate 15. A transmission cavity is formed between the middle layer plate 15 and the bottom layer plate 16. Several support rods 11 are installed below the bottom layer plate 16. The gear set passes through the middle layer plate 15. The gear ring 23 is located in the transmission cavity. All the sealing plates 19 are slidably installed in the sealed partition cavity. When the vacuum module 13 is activated, the air in the sealed chamber is rapidly extracted, the pressure in the sealed chamber drops and approaches a vacuum state, providing negative pressure adsorption conditions for subsequent resin injection.

[0022] The cylinder 25 is arc-shaped and is installed at the bottom of the bottom plate 16. A sliding groove 18 is provided on the outer ring plate 17. The lever 24 passes through the sliding groove 18 and is connected to the piston rod. A guide tube 26 is connected between the end of the cylinder 25 away from the lever 24 and the vacuum module 13. Each sealing piece 19 is triangular. The right-angled sides of adjacent sealing pieces 19 are in contact with each other. A slot is provided on each sealing piece 19. A limiting member 20 is provided on the middle plate 15 corresponding to each sealing piece 19. The slot in each sealing piece 19 is slidably connected to the limiting member 20. A spring is pre-installed inside the cylinder 25. In the initial state, the piston rod is kept in an extended state by the spring force. As the vacuum level in the sealed chamber increases, the air pressure inside the cylinder 25, which is connected to the vacuum module 13 through the conductor 26, also decreases. When the negative pressure suction overcomes the elastic force of the spring inside the cylinder 25, the piston rod retracts and moves backward. The retraction action of the piston rod drives the lever 24 to slide in the slide groove 18, thereby driving the gear ring 23 to rotate circumferentially. The rotation of the gear ring 23 drives all the pinions 22 to rotate synchronously. The large gear 21 also rotates synchronously under the drive of the pinions 22. Under the guidance and constraint of the limiting member 20 on the sealing plate 19, the rotational motion of the large gear 21 is converted into the linear motion of the sealing plate 19 sliding radially towards the center. Several sealing plates 19 move towards the center smoothly at the same time until the right-angled sides of the adjacent sealing plates 19 contact each other and press together, completely sealing the through-passage in the middle of the back pressure mechanism. After the sealing plates 19 in the back pressure mechanism are completely closed, in order to ensure that the sealing plates 19 are not deformed and damaged due to excessive pressure drop caused by the continuous operation of the vacuum module 13, the vacuum module 13 activates the detection unit. The detection unit senses the pressure change and stops the operation of the vacuum module 13. At this time, the air passage between the sealed chamber and the vacuum module 13 is cut off, forming an independent sealed pressure-holding space.

[0023] Each gear set consists of a rotating shaft, a large gear 21, and a small gear 22. The rotating shaft passes through the middle plate 15. The large gear 21 and the small gear 22 are connected at both ends of the rotating shaft. The large gear 21 is located in the sealed partition cavity, and the small gear 22 is located in the transmission cavity. Each sealing plate 19 has a toothed groove on its inclined side. The large gear 21 meshes with the toothed groove, and all the small gears 22 mesh with the outer ring of the toothed ring 23. The upper mold 5 and the mold coupling body 6 are made of thin and tough material. Under stable pressure, the resin feed pipe 10 begins to inject resin into the molding cavity. Under the auxiliary adsorption of negative pressure, the resin can quickly and evenly fill the gaps in the glass fiber, achieving full wetting and bonding. The upper mold 5 undergoes flexible deformation under the action of negative pressure. Through flexible deformation, the upper mold 5 fits the glass fiber more tightly, preventing the glass fiber from moving under the pressure of the resin, ensuring the consistency of the thickness of the fiberglass blank. The feed amount in the resin feed pipe 10 is automatically closed after reaching the preset value to prevent excessive resin injection and overflow of the mold. In the subsequent cooling and shaping process, the pressure holding space maintains a constant pressure to ensure that the fiberglass is cured under stable pressure, avoiding defects such as pores, shrinkage depressions or uneven fiber distribution caused by pressure fluctuations, and improving the quality of the product. After the fiberglass cools and sets, the vacuum module 13 releases the negative pressure through its built-in pressure relief element. The negative pressure inside the cylinder 25 disappears, and the piston rod returns to its original position under the elastic force of the spring. The lever 24 drives the gear ring 23 to rotate, driving all the sealing plates 19 to retract in the radial centrifugal direction. The channel in the middle of the back pressure mechanism is reopened. Finally, the operator controls the lifting platform 3 to lift through the drive module 4, separating the upper mold 5 from the lower mold 7. The formed fiberglass product can then be smoothly removed from the lower mold 7, completing a full work cycle.

[0024] The working principle of this invention is as follows: At the start of operation, the operator first accurately lays the glass fiber reinforced material inside the cavity of the lower mold 7, ensuring uniform fiber distribution. Then, the control system starts the drive module 4, which drives the lifting platform 3 to slide downwards along a pair of guide rods 2 until the upper mold 5 and the lower mold 7 are closed. At this time, the glass fiber is sealed in the molding cavity formed by the mold coupling body 6 and the lower mold 7. After the mold is closed, a pair of rubber sealing rings 8 fit tightly together to form the first main seal, ensuring that the molding cavity is isolated from the outside atmosphere. A pair of labyrinth sealing rings 9 around the rubber sealing rings 8 also fit together to form multiple intersecting channels. The molding cavity is connected to the vacuum module 13 through the back pressure mechanism, becoming a sealed chamber. When the rubber sealing rings 8 age or partially fail due to long-term operation, the gas changes its flow direction multiple times when passing through the multiple intersecting channels, and the pressure is gradually reduced to achieve back pressure. This still effectively prevents leakage and ensures that the molding area maintains the integrity of the seal during the curing cycle, providing a stable and reliable sealing guarantee.

[0025] When the vacuum module 13 is activated, the air in the sealed chamber is rapidly extracted, and the pressure in the sealed chamber drops and approaches a vacuum state, providing negative pressure adsorption conditions for subsequent resin injection. A spring is pre-installed inside the cylinder 25. Initially, the piston rod is held extended by the spring force. As the vacuum level in the sealed chamber increases, the air pressure inside the cylinder 25, connected to the vacuum module 13 via the conductor 26, also decreases. When the negative pressure suction overcomes the spring force inside the cylinder 25, the piston rod retracts and moves backward. This retraction of the piston rod causes the lever 24 to slide within the groove 18, thereby driving the gear ring 23 to rotate circumferentially. The rotation of the gear ring 23 drives all the pinions 22 to rotate synchronously. The large gear 21 also rotates synchronously under the drive of the pinions 22. Under the guidance and constraint of the limiting member 20 on the sealing plate 19, the rotational motion of the large gear 21 is converted into the linear motion of the sealing plate 19 sliding radially towards the center. Several sealing plates 19 move towards the center smoothly at the same time until the right-angled sides of the adjacent sealing plates 19 contact each other and press together, completely sealing the through-passage in the middle of the back pressure mechanism. After the sealing plates 19 in the back pressure mechanism are completely closed, in order to ensure that the sealing plates 19 are not deformed and damaged due to excessive pressure drop caused by the continuous operation of the vacuum module 13, the vacuum module 13 activates the detection unit. The detection unit senses the pressure change and stops the operation of the vacuum module 13. At this time, the air passage between the sealed chamber and the vacuum module 13 is cut off, forming an independent sealed pressure-holding space.

[0026] The upper mold 5 and the mold coupling body 6 are made of thin and tough material. Under stable pressure, the resin feed pipe 10 begins to inject resin into the molding cavity. Under the auxiliary adsorption of negative pressure, the resin can quickly and evenly fill the gaps in the glass fiber, achieving full wetting and bonding. The upper mold 5 undergoes flexible deformation under the action of negative pressure. Through flexible deformation, the upper mold 5 fits the glass fiber more tightly, preventing the glass fiber from moving under the pressure of the resin, ensuring the consistency of the thickness of the fiberglass blank. The feed amount in the resin feed pipe 10 is automatically closed after reaching the preset value to prevent excessive resin injection and overflow of the mold. In the subsequent cooling and shaping process, the pressure holding space maintains a constant pressure to ensure that the fiberglass is cured under stable pressure, avoiding defects such as pores, shrinkage depressions or uneven fiber distribution caused by pressure fluctuations, and improving the quality of the product. After the fiberglass cools and sets, the vacuum module 13 releases the negative pressure through its built-in pressure relief element. The negative pressure inside the cylinder 25 disappears, and the piston rod returns to its original position under the elastic force of the spring. The lever 24 drives the gear ring 23 to rotate, driving all the sealing plates 19 to retract in the radial centrifugal direction. The channel in the middle of the back pressure mechanism is reopened. Finally, the operator controls the lifting platform 3 to lift through the drive module 4, separating the upper mold 6 from the lower mold 7. The formed fiberglass product can then be smoothly removed from the lower mold 7, completing a full work cycle.

[0027] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A vacuum forming device that is sealed and leak-proof, characterized in that: The assembly includes a support plate (1), a lifting platform (3), an upper mold (5), a lower mold (7), and a vacuum module (13). The support plate (1) is located on one side of the vacuum module (13). The lifting platform (3) is mounted on the support plate (1). The vacuum module (13) is equipped with a back pressure mechanism and a fixed platform (12) is mounted on the back pressure mechanism. The upper mold (5) is mounted below the lifting platform (3). A mold connecting body (6) is located in the middle of the upper mold (5). The lower mold (7) is mounted on the fixed platform (12). The back pressure mechanism has a through-hole in the middle. The back pressure mechanism is equipped with a pneumatic drive unit and a blocking unit. The pneumatic drive unit includes a cylinder (25) and a gear ring (23). A lever (24) is connected between the piston rod of the cylinder (25) and the gear ring (23). The blocking unit includes several sealing plates (19). The several sealing plates (19) are evenly distributed in a circle. The several sealing plates (19) seal the through-hole. A gear set for transmitting power is provided between the gear ring (23) and each sealing plate (19).

2. The vacuum forming device for sealing and preventing leakage according to claim 1, characterized in that: The back pressure mechanism is disc-shaped and consists of three layers: upper, middle and bottom. The middle of each of the three layers is open, and an outer ring plate (17) is provided on the outside of each layer. A sealed partition cavity is formed between the upper layer plate (14) and the middle layer plate (15), and a transmission cavity is formed between the middle layer plate (15) and the bottom layer plate (16). Several support rods (11) are installed below the bottom layer plate (16). The gear set passes through the middle layer plate (15), and the gear ring (23) is located in the transmission cavity. All the sealing plates (19) are slidably installed in the sealed partition cavity.

3. The vacuum forming device for sealing and preventing leakage according to claim 2, characterized in that: The cylinder (25) is arc-shaped and is installed at the bottom of the bottom plate (16). The outer ring plate (17) has a sliding groove (18). The lever (24) passes through the sliding groove (18) and is connected to the piston rod. The end of the cylinder (25) away from the lever (24) is connected to the vacuum module (13) by a conduit (26).

4. The vacuum forming device for sealing and preventing leakage according to claim 2, characterized in that: Each of the closed pieces (19) is triangular in shape, with the right-angled sides of adjacent closed pieces (19) in contact with each other. Each closed piece (19) has a slot. The middle layer plate (15) is provided with a limiting member (20) corresponding to each closed piece (19). The slot in each closed piece (19) is slidably connected to the limiting member (20).

5. The vacuum forming device for sealing and preventing leakage according to claim 4, characterized in that: Each gear set consists of a shaft, a large gear (21) and a small gear (22). The shaft passes through the middle plate (15). The large gear (21) and the small gear (22) are connected at both ends of the shaft. The large gear (21) is located in the sealed partition cavity, and the small gear (22) is located in the transmission cavity.

6. The vacuum forming device for sealing and preventing leakage according to claim 5, characterized in that: Each of the closed pieces (19) has a toothed groove on its inclined side, the large gear (21) meshes with the toothed groove, and all the small gears (22) mesh with the outer ring of the toothed ring (23).

7. The vacuum forming device for sealing and preventing leakage according to claim 1, characterized in that: The support plate (1) is integrally provided with a pair of guide rods (2) and a slide rail. The lifting platform (3) is slidably installed on the pair of guide rods (2). The lifting platform (3) is provided with a drive module (4). The drive module (4) is connected to the slide rail. The mold assembly (6) is connected with a resin feed pipe (10).

8. A vacuum forming apparatus for sealing and preventing leakage according to any one of claims 1-7, characterized in that: The outer ring of the upper mold (5) and the upper plate (14) are provided with rubber sealing rings (8) and labyrinth sealing rings (9) respectively. A pair of rubber sealing rings (8) are in sealing contact, and a pair of labyrinth sealing rings (9) cooperate with each other.

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