Three-layer co-extrusion film blowing machine

Abstract

The invention relates to the technical field of film blowing machine equipment, in particular to a three-layer co-extrusion film blowing machine which comprises a truss, a film drawing mechanism is arranged at the position, close to the center, in the truss, the film drawing mechanism comprises a mounting frame fixed to the inner side of the truss, and a sliding table is arranged in the mounting frame; a pulling rope connected with an electric hoist is arranged at the upper end of the sliding table, a connecting block is arranged at the lower end of the pulling rope, a plurality of first grabbing plates evenly distributed in the circumferential direction of the connecting block are arranged at the lower end of the connecting block, and second grabbing plates are arranged at the lower ends of the first grabbing plates. The film drawing mechanism is arranged, the film drawing operation of the initial section of the film is achieved, the possibility that the hands are scalded due to the high temperature of the initial section of the film during manual film drawing is effectively reduced, meanwhile, the film drawing speed and direction are controlled through a traction rope, and the film drawing efficiency is improved. The possibility that the side face of the film is broken due to uneven film discharging and film discharging position deviation caused by manual film pulling is effectively reduced, and the film discharging efficiency and stability of the film blowing machine are improved.

Description

Technical Field

[0001] The present application relates to the technical field of blown film machine equipment, and particularly to a three-layer co-extrusion blown film machine. Background Art

[0002] A blown film machine refers to a type of plastic machinery that heats and melts plastic particles and then blows them into films. It is an essential mechanical product in the modern plastic product manufacturing process, including a three-layer co-extrusion blown film unit. A three-layer co-extrusion blown film machine is a device commonly used in plastic film production, mainly for producing composite films (such as food packaging films, fresh-keeping films, etc.). Its working principle is to melt and co-extrude three different types of plastics and form film layers through the blow molding process. The advantages of this device are that it can produce high-performance film materials with good strength, transparency, heat resistance, and barrier properties. The three-layer co-extrusion blown film unit has the advantages of higher output, better plasticization of products, low energy consumption, and simple operation, solving problems such as film edge curling and uneven winding size of the finished product, and raising the product quality to a new level, so it has been widely used.

[0003] Due to the different materials of the products, when producing different products, a material change operation is required. When the new material is extruded by the co-extrusion die head, it needs to be manually pulled so that the extruded film can pass through the traction device and the winding device, ensuring that the film pulling mechanism can continuously pull the film. This operation process is the film pulling operation.

[0004] Regarding the above-mentioned related technologies, when the existing three-layer co-extrusion blown film units perform film pulling, it is all manually done. Since the film is at a high temperature and has a high viscosity when it is just extruded, it is easy to stick to the hand and scald the hand, resulting in low safety during film pulling. Moreover, when pulling the film, the thickness of the film that has just been extruded and not blown is uneven, making it difficult for it to pass smoothly through the rollers of the traction device, easily causing the gap between the rollers to expand and reducing the service life of the traction device. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the present application provides a three-layer coextrusion blown film machine, which includes a truss. A die head is provided at a position near the center at the lower end of the truss. A traction device is provided at a position near the center at the upper end of the truss. A film pulling mechanism is provided at a position near the center inside the truss. The film pulling mechanism includes a mounting frame fixed to the inner side of the truss. A sliding table is provided inside the mounting frame. A traction rope connected to an electric hoist is provided at the upper end of the sliding table. An adjusting frame is provided at the upper end of the sliding table near the traction rope. The traction rope is lapped in a groove of the adjusting frame. A connecting block is provided at the lower end of the traction rope. A plurality of first gripping plates evenly distributed circumferentially along the connecting block are provided at the lower end of the connecting block. A second gripping plate is provided at the lower end of the first gripping plate. A support rod is provided at a position near the upper end inside the first gripping plate. One end of the support rod is rotatably connected to the first gripping plate. The other end of the support rod is provided with a first displacement plate. The first displacement plate is rotatably connected to the support rod. A telescopic airbag is provided at a position near the center at the upper end of the first displacement plate. The upper end of the telescopic airbag is fixedly connected to the connecting block. An air inflation fan is built in the telescopic airbag. A slitting assembly is provided at the lower end of the sliding table near the traction rope.

[0006] Further, the upper end of the second gripping plate is embedded inside the first gripping plate, and the second gripping plate is slidably connected to the first gripping plate. Fine spikes are provided at a position near the lower end inside the second gripping plate. The spikes are used to grip the film.

[0007] Further, the slitting assembly includes a limiting ring fixed to the lower end of the sliding table. The limiting ring is located directly above the connecting block. One end of the traction rope connecting the connecting block passes through the limiting ring. A plurality of curved plates evenly distributed circumferentially along the limiting ring are provided inside the limiting ring. A buckle ring is provided at the upper end of the curved plate. A connecting rod is provided on the outer side of the buckle ring. The connecting rod is rotatably connected to the curved plate through the buckle ring. A second displacement plate is provided at the upper end of the connecting rod. A plurality of the connecting rods are fixedly connected to the second displacement plate. A support is provided at the lower end of the curved plate. A roller is provided at the lower end of the support.

[0008] Further, the second displacement plate is coaxial with the limiting ring. The second displacement plate can vertically displace above the limiting ring. An extension plate is provided at a position near the edge on the outer side of the second displacement plate. The outer diameter of the ring formed by the extension plates is larger than the inner diameter of the limiting ring.

[0009] Further, an arc-shaped hot cutting rod is provided at a position near the roller at the lower end of the support. A plurality of the hot cutting rods are evenly distributed circumferentially along the limiting ring. The plurality of hot cutting rods can gather into a ring coaxial with the limiting ring.

[0010] Further, the second displacement plate coaxial with the limiting ring is also coaxial with the first displacement plate, and the circular ring formed by the first displacement plate and the first gripping plate is coaxial. The inner diameter of the second displacement plate is smaller than the outer diameter of the circular ring formed by the plurality of first gripping plates.

[0011] Further, the inner diameter of the limiting ring is larger than the outer diameter of the circular ring formed by the first gripping plates, and the first gripping plates can penetrate from below the limiting ring to above the limiting ring.

[0012] A method for using the three-layer coextrusion blown film machine described above includes the following steps: S1. Positioning: The sliding table extends outwards from the mounting frame. The connecting block of the film pulling mechanism is directly above the die head, and the second gripping plate is below the limiting ring. The telescopic airbag at the lower end of the connecting block is in a compressed state. The support rod props up the second gripping plate to make the second gripping plate expand outwards, and the first gripping plate covers the die head's material outlet. S2. Gripping: The die head extrudes the film. The telescopic airbag inhales and expands, causing the first displacement plate to drive the support rod to rotate. The support rod pulls the first gripping plate, causing the first gripping plate and the second gripping plate to close. During the closing process of the second gripping plate, the spikes on the inner side of the second gripping plate hook the front end of the film and pull the film towards the center position of the die head. At the same time, the traction rope drives the connecting block to move vertically upwards to lift the film. S3. Centering: During the upward movement of the second gripping plate, the first gripping plate penetrates from below the limiting ring to above the limiting ring and abuts against the second displacement plate. The first gripping plate pushes the second displacement plate upwards, causing the curved plate to drive the rollers to gather inwards. The film is located inside the circular ring formed by the plurality of rollers to center the film and prevent excessive deviation during the upward stretching of the film. S4. Slitting: When the rollers abut against the surface of the film, the inner side of the film is in an inflated state after blown film processing. The part of the film abutting against the surface of the hot cutting rod is hot cut by the hot cutting rod. The front section of the film during film extrusion is clamped on the second gripping plate, and the rear section of the film during film extrusion is located below the hot cutting rod. Then, the sliding table carries the waste of the front section of the film cut off and retracts it into the mounting frame to complete the slitting of the waste after film extrusion.

[0013] The technical solution provided by this application has the following beneficial effects compared with the known prior art: 1. The present application provides a film-pulling mechanism, a second grabbing plate and a first grabbing plate, and uses the opening and closing of the first grabbing plate to control the opening and closing of the second grabbing plate to grab the front section of the film, and then uses the traction rope to lift the connecting block, thereby enabling the second grabbing plate to lift the front section of the film, thereby achieving the film-pulling operation at the initial stage of the film. This effectively reduces the possibility of burns to the hands due to the high temperature of the initial stage of film discharge during manual film pulling. At the same time, the traction rope is used to control the speed and direction of film pulling, effectively reducing the possibility of uneven film discharge and film discharge position deviation caused by manual film pulling, thereby improving the film discharge efficiency and stability of the film blowing machine. 2. This application provides a slitting assembly, a curved plate, and a roller. During the film pulling process by the second gripper, the curved plate and the roller are used to limit the film, so that the film is always in a vertical state during the lifting process, preventing the film from deviating from the lifting path at the moment of starting to blow the film, thereby reducing the possibility of uneven thickness of the film during the blowing process, effectively improving the stability of the film during the blowing process, and reducing the possibility of the film breaking at the moment of blowing; 3. The present application sets up a heat cutting rod, and sets up a plurality of arc-shaped heat cutting rods that can form a ring. During the film pulling process, the heat cutting rod is used to heat cut the inflated film, separate the initial and rear sections of the film pulling, and cut off the front section with uneven film thickness, thereby reducing the possibility of the traction device roller being accidentally stretched due to uneven film thickness, and improving the working efficiency and life of the traction device. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the overall structure of the embodiment of the present application; Figure 2 This is a structural diagram of the film pulling mechanism in the embodiment of the present application; Figure 3 This is a structural diagram of the first grabbing plate in the embodiment of the present application; Figure 4 This is a schematic diagram of the deployment of the first grabbing plate in the embodiment of the present application; Figure 5 This is a schematic diagram of the aggregation of the first grab plate in the embodiment of the present application; Figure 6 This is a schematic diagram of the structure of the telescopic airbag in an embodiment of the present application; Figure 7 This is a structural diagram of the second grabbing plate in the embodiment of the present application; Figure 8 This is a schematic structural diagram of the cutting assembly in an embodiment of the present application; Figure 9 This is a schematic diagram of the gathering of the hot cutting rods in the embodiment of the present application; Figure 10 Schematic diagram of the structure of the curved plate in the embodiment of the present application.

[0015] In the figure: 1, truss; 2, die head; 3, traction device; 4, film pulling mechanism; 41, mounting frame; 42, sliding table; 43, traction rope; 44, adjusting frame; 45, connecting block; 46, first gripping plate; 47, second gripping plate; 471, barb; 48, support rod; 49, first displacement plate; 40, telescopic airbag; 5, slitting assembly; 51, limiting ring; 52, second displacement plate; 521, extension plate; 53, connecting rod; 54, buckle; 55, curved plate; 56, support; 57, roller; 58, hot cutting rod. Specific embodiments

[0016] For a better understanding of the above technical solution, the following will be combined with the accompanying drawings of the specification Figure 1-10 and specific embodiments to explain the above technical solution in detail.

[0017] Reference Figure 1 and Figure 2 As shown in FIGS. 1 and 2, the present application discloses a three-layer co-extrusion blown film machine, including a truss 1, a die head 2, a traction device 3 and a film pulling mechanism 4. The die head 2 is fixedly installed inside the truss 1 and near the lower end. The traction device 3 is fixedly installed at the upper end of the truss 1 and near the center for pulling the film. The film pulling mechanism 4 is fixedly installed inside the truss 1 and near the center for pulling the film at the initial stage when the film exits the die head 2.

[0018] The die head extrudes the film, and the extruded film is pulled out by the film pulling mechanism 4, replacing manual film pulling. Then, the pulled film is sent into the traction device 3, and the subsequent traction and winding of the film are completed by the traction device 3.

[0019] Reference Figures 1 to 7, the film pulling mechanism 4 includes a mounting frame 41, a sliding table 42, a towing rope 43, an adjusting frame 44, a connecting block 45, a first gripping plate 46, a second gripping plate 47, barbs 471, a support rod 48, a first displacement plate 49, a telescopic airbag 40 and a slitting assembly 5. The mounting frame 41 is fixedly installed on the truss 1, and the installation position of the mounting frame 41 does not interfere with the film pulling path of the film. The sliding table 42 is fixedly installed inside the mounting frame 41, and the displacement end of the sliding table 42 can extend outward from the inside of the mounting frame 41. One end of the towing rope 43 is connected to an electric hoist, and the electric hoist is fixedly installed at the displacement end of the sliding table 42. Therefore, the displacement end of the sliding table 42 can carry the electric hoist for synchronous displacement. The adjusting frame 44 is fixedly installed on the upper surface of the displacement end of the sliding table 42 and near the edge, and the towing rope 43 is arranged in the groove on the adjusting frame 44. The connecting block 45 is fixedly installed at the end of the towing rope 43 away from the electric hoist. The first gripping plate 46 is rotatably installed at the lower end of the connecting block 45, and multiple first gripping plates 46 are evenly distributed along the circumference of the connecting block 45, and multiple first gripping plates 46 can gather towards the center. The second gripping plate 47 is slidably installed at the lower end of the first gripping plate 46, and the second gripping plate 47 can slide at the lower end of the first gripping plate 46 to realize the telescoping of the second gripping plate 47. Multiple small barbs 471 are fixedly installed on the inner side of the second gripping plate 47 and near the lower end, and multiple barbs 471 are evenly distributed on the inner side wall of the second gripping plate 47 for direct contact with the film. One end of the support rod 48 is rotatably installed on the inner side wall of the first gripping plate 46 and near the upper end, and each support rod 48 is connected to a first gripping plate 46. The first displacement plate 49 is installed at the other end of the support rod 48, and multiple support rods 48 are evenly distributed along the circumference of the first displacement plate 49, and the first displacement plate 49 is rotatably connected to multiple support rods 48. The telescopic airbag 40 is fixedly installed between the first displacement plate 49 and the connecting block 45, and an air inflation fan is arranged inside the telescopic airbag 40. The telescopic airbag 40 can be telescoped in the vertical direction. By telescoping the telescopic airbag 40, the synchronous rotation of the support rod 48 is controlled. Furthermore, by using the rotation of the support rod 48, the rotation of the first gripping plate 46 is controlled, and then the opening and closing of multiple first gripping plates 46 are controlled.

[0020] During the operation of the film blowing machine, the front section of the film is extruded by the die head 2. The front section of the extruded film contacts the spurs 471 on the inner side wall of the second gripper plate 47. The electric hoist at one end of the towing rope 43 winds up the towing rope 43. The towing rope 43 drives the connecting block 45 to move vertically upward. Under the influence of its own gravity, the first gripper plate 46 and the second gripper plate 47 begin to converge towards the central position. The film hooked by the spurs 471 is lifted by the upward-moving second gripper plate 47. At this time, the telescopic airbag 40 located inside the first gripper plate 46 starts to inflate and expand. The inflated telescopic airbag 40 pushes the first displacement plate 49 downward, drives the support rod 48 to rotate by using the first displacement plate 49, and then makes the first gripper plate 46 converge towards the central position by using the support rod 48, thereby driving the second gripper plate 47 to converge further by using the first gripper plate 46. The overall process is that when the film is extruded, the second gripper plate 47 moves slowly upward while converging towards the central position. During the process of the second gripper plate 47 converging towards the central position, multiple small spurs 471 on the inner side wall of the second gripper plate 47 grab the film, and then lift the entire front section of the film upward. The lifting action of the front section of the film is completed.

[0021] Reference Figure 2 、 Figure 8 、 Figure 9 and Figure 10, the slitting assembly 5 includes a limit ring 51, a second displacement plate 52, an extension plate 521, a connecting rod 53, a snap ring 54, a curved plate 55, a bracket 56, a roller 57 and a hot cutting rod 58. The limit ring 51 is fixedly installed at the lower end of the displacement end of the sliding table 42 and near the edge. The traction rope 43 penetrates through the inside of the limit ring 51. The second displacement plate 52 is installed above the limit ring 51, and the second displacement plate 52 does not interfere with the limit ring 51. The extension plate 521 is fixedly installed on the outside of the second displacement plate 52 and near the edge, and multiple extension plates 521 are evenly distributed along the circumference of the second displacement plate 52. The outer diameter of the extension plate 521 is larger than the inner diameter of the limit ring 51. The connecting rod 53 is fixedly installed at the lower end of the second displacement plate 52, and multiple connecting rods 53 are evenly distributed along the circumference of the second displacement plate 52. The snap ring 54 is rotatably connected to the lower end of the connecting rod 53. The snap ring 54 is located inside the limit ring 51, and the snap ring 54 does not interfere with the limit ring 51 during displacement. The curved plate 55 is fixedly installed on the outside of the snap ring 54, and the curved plate 55 is rotatably connected to the connecting rod 53 through the snap ring 54. Multiple curved plates 55 are evenly distributed along the circumference of the second displacement plate 52. The outer diameter of the ring formed by multiple curved plates 55 is larger than the inner diameter of the limit ring 51. During the upward movement of the second displacement plate 52, the outer side wall of the curved plate 55 contacts the inner side wall of the limit ring 51. During the upward movement of the curved plate 55, the curved plate 55 is squeezed by the limit ring 51 to realize the rotation of the curved plate 55. The bracket 56 is fixedly installed at the lower end of the curved plate 55. The roller 57 is rotatably installed inside the bracket 56, and multiple rollers 57 are evenly distributed along the circumference of the second displacement plate 52. The hot cutting rod 58 is fixedly installed at the lower end of the bracket 56 and near the roller 57. Multiple arc-shaped hot cutting rods 58 are evenly distributed along the circumference of the second displacement plate 52. After the multiple arc-shaped hot cutting rods 58 are gathered, their heads and tails abut against each other and enclose a small circular hot cutting circle.

[0022] Among them, the outer diameter of the second displacement plate 52 is smaller than the inner diameter of the limit ring 51, and the outer diameter of the extension plate 521 is larger than the inner diameter of the limit ring 51. The extension plate 521 can prevent the second displacement plate 52 from passing through the limit ring 51. The second displacement plate 52 and the connecting rod 53 can slide inside the limit ring 51 and displace in the vertical direction. During the upward displacement of the second displacement plate 52, the outer side wall of the curved plate 55 contacts the inner side wall of the limit ring 51. Under the influence of the limit ring 51, the curved plate 55 rotates synchronously during the upward movement. Multiple curved plates 55 rotate synchronously towards the central position to realize the aggregation of multiple curved plates 55. The inner diameter of the limit ring 51 is larger than the outer diameter of the ring formed by multiple first gripping plates 46, so that the first gripping plates 46 can smoothly pass through the limit ring 51 after aggregation.

[0023] The inner diameter of the second displacement plate 52 is smaller than the outer diameter of the circular ring formed by multiple first grab plates 46. During the upward movement of the connecting block 45, the outer wall of the first grab plate 46 abuts against the inner wall of the second displacement plate 52, and during the upward movement of the first grab plate 46, the second displacement plate 52 is pushed to move upward, thereby causing the limit ring 51 to contact the curved plate 55, and the curved plate 55 rotates under the influence of the limit ring 51.

[0024] The second gripping plate 47 lifts the front section of the film, and the traction rope 43 continues to be reeled in by the electric hoist. The first gripping plate 46 and the second gripping plate 47 continue to move vertically upward. Then, the first gripping plate 46 is completely assembled under the action of the support rod 48 and the telescopic airbag 40. The first gripping plate 46 moves upward from the bottom of the limit ring 51, and then the first gripping plate 46 completely passes through the limit ring 51. As the first gripping plate 46 moves upward, it contacts the second displacement plate 52, pushing the second displacement plate 52 upward. As the second displacement plate 52 moves upward, the curved plate 55 contacts the inner wall of the limit ring 51, and the multiple curved plates 55 converge toward the center, causing the rollers 57 on the inside of the bracket 56 to wrap around the outside of the film, and the film is centered in the center of the multiple rollers 57. As a result, the front section of the film is completely placed between the second gripping plate 47 and the hot cutting rod 58. At this time, the extruded film is blown, inflated, and expanded into a hollow cylindrical shape. At this time, the front section of the film above the hot cutting rod 58 is clamped by the second gripper 47, and the part in contact with the roller 57 is clamped by the roller 57. The film below the hot cutting rod 58 is blown and expanded, and the outer wall of the film is attached to the outer wall of the hot cutting rod 58. Due to the aggregation of multiple curved hot cutting rods 58, a small circle of hot cutting ring is formed. After heating the hot cutting ring, the hot cutting ring can heat-cut the film, separating the front and back sections of the film, and cutting off the uneven front section of the film from the film.

[0025] A method for using the above-mentioned three-layer co-extrusion film blowing machine comprises the following steps: S1. Positioning: The slide 42 extends outward from the mounting bracket 41. The connecting block 45 of the film-drawing mechanism 4 is located directly above the die 2, and the second gripping plate 47 is located below the limiting ring 51. The telescopic airbag 40 at the lower end of the connecting block 45 is in a compressed state. The support rod 48 props up the second gripping plate 47, causing it to expand outward. The first gripping plate 46 covers the discharge port of the die 2. S2. Grasping: The die 2 extends the film outward, and the telescopic airbag 40 inhales and expands, causing the first displacement plate 49 to drive the support rod 48 to rotate. The support rod 48 pulls the first grabbing plate 46, causing the first grabbing plate 46 and the second grabbing plate 47 to retract. During the retraction of the second grabbing plate 47, the protrusion 471 on the inner side of the second grabbing plate 47 hooks the front end of the film and pulls the film toward the center of the die 2. At the same time, the traction rope 43 drives the connecting block 45 to move vertically upward, lifting the film upward; S3. Center. During the upward movement of the second gripper plate 47, the first gripper plate 46 penetrates from below the limit ring 51 to above the limit ring 51, and the first gripper plate 46 abuts against the second displacement plate 52. The first gripper plate 46 pushes the second displacement plate 52 upward, causing the curved plate 55 to drive the rollers 57 to gather inward. The film is located inside the ring formed by the multiple rollers 57 to center the film and prevent excessive deviation during the upward stretching of the film. S4. Slitting. When the rollers 57 abut against the surface of the film, the inner side of the film is in an inflated state after blow molding. The part of the film that abuts against the surface of the hot cutting rod 58 is hot cut by the hot cutting rod 58. The front section of the film exiting the film is clamped on the second gripper plate 47, and the rear section of the film exiting the film is located below the hot cutting rod 58. Then, the sliding table 42 carries the waste of the front section of the film cut off into the mounting frame 41 to complete the slitting of the waste after the film exits.

[0026] The working principle of the embodiment of the present application: During the working process, the die head 2 extrudes the film. The front section of the extruded film is grabbed by the spikes 471 on the inner side wall of the second gripper plate 47. While the traction rope 43 is wound upward, the telescopic airbag 40 inflates and expands, causing multiple first gripper plates 46 to gather towards the central position. The second gripper plate 47 gathers towards the central position while moving upward, and then uses the spikes 471 to lift the film upward. During the upward movement of the first gripper plate 46, it contacts the limit ring 51 and passes through below the limit ring 51. When the outer side wall of the first gripper plate 46 passes through the limit ring 51 and abuts against the second displacement plate 52, the upward movement of the first gripper plate 46 will push the second displacement plate 52 upward. The upward displacement of the second displacement plate 52 drives the curved plate 55 to move upward. The limit ring 51 contacts the curved plate 55, causing the curved plate 55 to rotate, and then realizing the operation of multiple curved plates 55 gathering towards the central position. The rollers 57 are used to limit the film, making the film located at the center of the multiple rollers 57. Then, the film is blown, and the expanded film is in the shape of a hollow cylinder. The outer side wall of the expanded film abuts against the ring formed by the hot cutting rods 58 at the lower end of the bracket 56. The hot cutting rods 58 at high temperature are used to hot cut the film, cutting off the front section with uneven film thickness from the film. Finally, the rear section of the film that can be directly used is sent into the traction device 3 by manual for winding treatment.

[0027] Although the embodiments of the present application have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present application. The scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A three-layer co-extrusion blown film machine, comprising a truss (1), a die head (2) is arranged at a position close to the center at the lower end of the truss (1), and a traction device (3) is arranged at a position close to the center at the upper end of the truss (1), characterized in that, A film pulling mechanism (4) is provided inside the truss (1) and near the center. Among them, the film pulling mechanism (4) includes a mounting frame (41) fixed to the inner side of the truss (1). A sliding table (42) is provided inside the mounting frame (41). A traction rope (43) connected to an electric hoist is provided at the upper end of the sliding table (42). An adjusting frame (44) is provided at the upper end of the sliding table (42) and near the traction rope (43). The traction rope (43) is lapped in the groove of the adjusting frame (44). A connecting block (45) is provided at the lower end of the traction rope (43). A plurality of first gripping plates (46) evenly distributed along the circumferential direction of the connecting block (45) are provided at the lower end of the connecting block (45). A second gripping plate (47) is provided at the lower end of the first gripping plate (46). A support rod (48) is provided inside the first gripping plate (46) and near the upper end. One end of the support rod (48) is rotatably connected to the first gripping plate (46). The other end of the support rod (48) is provided with a first displacement plate (49). The first displacement plate (49) is rotatably connected to the support rod (48). An expansion airbag (40) is provided at the upper end of the first displacement plate (49) and near the center. The upper end of the expansion airbag (40) is fixedly connected to the connecting block (45). The expansion airbag (40) is internally provided with an air inflation blower. A cutting component (5) is provided at the lower end of the sliding table (42) and near the traction rope (43).

2. The three-layer coextrusion blown film machine according to claim 1, wherein, The upper end of the second gripping plate (47) is embedded inside the first gripping plate (46), and the second gripping plate (47) is slidably connected to the first gripping plate (46). Fine spikes (471) are provided inside the second gripping plate (47) and near the lower end. The spikes (471) are used for gripping the film.

3. The three-layer coextrusion blown film machine according to claim 2, characterized in that, The cutting component (5) includes a limiting ring (51) fixed to the lower end of the sliding table (42). The limiting ring (51) is located directly above the connecting block (45). One end of the traction rope (43) connecting the connecting block (45) passes through the limiting ring (51). A plurality of curved plates (55) evenly distributed along the circumferential direction of the limiting ring (51) are provided inside the limiting ring (51). A buckle ring (54) is provided at the upper end of the curved plate (55). A connecting rod (53) is provided outside the buckle ring (54). The connecting rod (53) is rotatably connected to the curved plate (55) through the buckle ring (54). A second displacement plate (52) is provided at the upper end of the connecting rod (53). A plurality of the connecting rods (53) are fixedly connected to the second displacement plate (52). A bracket (56) is provided at the lower end of the curved plate (55). A roller (57) is provided at the lower end of the bracket (56).

4. A three-layer coextrusion blown film machine according to claim 3, characterized in that, The second displacement plate (52) is coaxial with the limiting ring (51). The second displacement plate (52) can vertically displace above the limiting ring (51). An extension plate (521) is provided outside the second displacement plate (52) and near the edge. The outer diameter of the ring formed by the extension plate (521) is larger than the inner diameter of the limiting ring (51).

5. The three-layer co-extrusion blown film machine according to claim 4, characterized in that, An arc-shaped hot cutting rod (58) is provided at the lower end of the bracket (56) and near the roller (57). A plurality of the hot cutting rods (58) are evenly distributed along the circumference of the limiting ring (51). The plurality of the hot cutting rods (58) can be gathered into a circular ring coaxial with the limiting ring (51).

6. The three-layer coextrusion blown film machine according to claim 5, characterized in that, The second displacement plate (52) coaxial with the limiting ring (51) is also coaxial with the first displacement plate (49), and the first displacement plate (49) and the first grab plate (46) are coaxial with each other. The inner diameter of the second displacement plate (52) is smaller than the outer diameter of the ring formed by the plurality of first grab plates (46).

7. A three-layer coextrusion blown film machine according to claim 6, wherein, The inner diameter of the limiting ring (51) is larger than the outer diameter of the circular ring formed by the first grab plate (46), and the first grab plate (46) can penetrate from the bottom of the limiting ring (51) to the top of the limiting ring (51).

8. A method for using a three-layer coextrusion blown film machine according to claim 7, characterized in that, The following steps are involved: S1. Positioning, the slide (42) extends outward from the mounting frame (41), the connecting block (45) of the film pulling mechanism (4) is located directly above the die head (2), and the second grab plate (47) is located below the limiting ring (51), the telescopic airbag (40) located at the lower end of the connecting block (45) is in a compressed state, the support rod (48) supports the second grab plate (47), so that the second grab plate (47) is expanded outward, and the first grab plate (46) covers the discharge port of the die head (2); S2. Grabbing, the die head (2) moves the film outward, the telescopic airbag (40) inhales and expands, causing the first displacement plate (49) to drive the support rod (48) to rotate, and the support rod (48) pulls the first grab plate (46), so that the first grab plate (46) and the second grab plate (47) are retracted. During the process of the second grab plate (47) retracting, the thorns (471) on the inner side of the second grab plate (47) hook the front end of the film and pull the film toward the center of the die head (2). At the same time, the traction rope (43) drives the connecting block (45) to move vertically upward to lift the film upward; S3. Centering, during the upward movement of the second grab plate (47), the first grab plate (46) passes through from the bottom of the limiting ring (51) to the top of the limiting ring (51), and the first grab plate (46) abuts against the second displacement plate (52). The first grab plate (46) pushes the second displacement plate (52) to move upward, so that the curved plate (55) drives the rollers (57) to gather inward, and the film is located inside the ring surrounded by the multiple rollers (57), so that the film is centered to avoid excessive deviation during the upward stretching process of the film; S4. Cutting. When the roller (57) contacts the surface of the film, the inner side of the film is inflated after the film blowing process. The portion of the film that contacts the surface of the hot cutting rod (58) is cut by the hot cutting rod (58). The front section of the film is clamped on the second gripping plate (47). The rear section of the film is located below the hot cutting rod (58). Then the slide (42) carries the waste of the front section of the film that has been cut and puts it into the mounting frame (41), completing the cutting of the waste after the film is cut.

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