A vacuum blister forming device and forming process thereof

Abstract

The present invention belongs to the technical field of blister forming, and particularly relates to a blister box vacuum blister forming device and its forming process. The blister box vacuum blister forming device of the present invention comprises an upper box body, a lower box body, a heating unit, a clamping assembly and an exhaust assembly. When in use, the gas thrust formed by the air pressure difference can be used to support the plastic sheet. When the plastic sheet is softened by heat, the air thrust formed by the air pressure difference can balance the gravity of the plastic sheet itself, so the plastic sheet will not fall and stretch in the middle due to its own gravity. During the entire heating process, the plastic sheet always remains flat and is heated more evenly, which will not affect the subsequent blister process, thereby improving the yield rate. The blister box vacuum blister forming process of the present invention uses the air thrust generated by the air pressure difference during processing to enable the plastic sheet to maintain a flat surface after softening, and to be heated more evenly, which will not affect the subsequent blister process, thereby improving the yield rate.

Description

Technical Field

[0001] The invention belongs to the technical field of blister forming, and particularly relates to a blister box vacuum blister forming device and a forming process thereof. Background Art

[0002] Blistering is a plastic processing technology. The main principle is to heat and soften the flat plastic sheet, then use vacuum adsorption to the mold surface, and then cool it down to form. It is widely used in plastic packaging, lighting, advertising, decoration and other industries.

[0003] When using existing blister forming equipment and blister forming technology for processing, due to the weight of the plastic sheet itself, after the plastic sheet is heated and softened, it is very easy for the middle part to fall and stretch, resulting in uneven distribution of the plastic sheet surface, affecting the subsequent blister forming and resulting in a high rate of defective products. Summary of the invention

[0004] Based on this, it is necessary to provide a blister box vacuum blister forming equipment to solve the problem of high defective product generation rate during production of compression molding equipment in the prior art; and also provide a blister box vacuum blister forming process to solve the problem of high defective product generation rate during production of vacuum blister forming process for blister boxes in the prior art.

[0005] The above purpose is achieved through the following technical solutions, wherein the technical solution of the blister box vacuum blister forming equipment is:

[0006] A vacuum blister forming device for a blister box, comprising:

[0007] upper box;

[0008] A lower box body cooperates with the upper box body to form a sealed chamber;

[0009] A heating unit, used for heating the plastic sheet in the sealed chamber;

[0010] A clamping assembly is provided in a guide slide in the lower box body and is in sliding sealing contact with the inner wall of the upper box body. The clamping assembly is used to clamp the plastic sheet and cooperate with the plastic sheet to separate the sealed chamber into an upper chamber and a lower chamber. A locking piece is provided on the clamping assembly, and the locking piece is used to lock the clamping assembly in the lower box body in the up and down directions.

[0011] The air extraction assembly is used to extract the air in the upper chamber.

[0012] Furthermore, it also includes a lifting component, which is driven by the air extracted from the exhaust component and is used to control the movement of the heating unit in the up and down directions.

[0013] Furthermore, the air extraction component includes an air extraction pipeline and an air pump arranged on the upper box body, the air inlet of the air extraction pipeline is connected to the inner cavity of the upper box body, and the air pump is connected to the air extraction pipeline.

[0014] Furthermore, the vacuum assembly also includes a high-pressure pipeline, the air inlet of the high-pressure pipeline is connected to the air outlet of the vacuum pipeline, a piston cavity is arranged at the air outlet of the high-pressure pipeline, the lifting assembly includes a lifting frame and a piston rod fixedly connected together, the piston rod guide is slidably arranged in the piston cavity, and the lifting frame is fixedly connected to the heating unit.

[0015] Furthermore, the clamping assembly includes an upper clamping frame and a lower clamping frame, and also includes a fixing member for fixing the upper clamping frame and the lower clamping frame together.

[0016] Furthermore, the locking member is a spring pin arranged on the lower clamping frame, and the lower box body is provided with a locking hole for the spring pin to be inserted after being ejected.

[0017] Furthermore, it also includes a control component for controlling the opening and closing of the air pump, the control component includes a control pin extending into the locking hole, and the spring pin can push the control pin to close the air pump after it pops out.

[0018] Furthermore, it also includes a gravity balance component, which includes a winding piece, a vertical line and a weight. The winding piece is arranged on the inner wall of the upper box body, one end of the vertical line is fixedly connected to the clamping assembly, and the other end passes around the winding piece and is fixedly connected to the weight.

[0019] The beneficial effects of the vacuum blister forming device for a blister box of the present invention are as follows: when the vacuum blister forming device for a blister box of the present invention is used, the clamping assembly is first used to clamp the plastic sheet, the upper box body and the lower box body are buckled together to form a sealed chamber, the clamping assembly and the plastic sheet separate the sealed chamber into an upper chamber and a lower chamber, the air in the upper chamber is extracted by the exhaust assembly, thereby forming an air pressure difference between the upper chamber and the lower chamber, the gas thrust formed by the air pressure difference is used to support the plastic sheet, and the locking member locks the plastic sheet at a set position in the lower box body in the upper and lower directions, the heating unit is used to heat the plastic sheet, and when the plastic sheet is softened, the air thrust formed by the air pressure difference can balance the gravity of the plastic sheet itself, so the plastic sheet will not fall and stretch in the middle due to its own gravity, and the plastic sheet will always remain flat during the entire heating process, and the heat is relatively uniform, which will not affect the subsequent blister forming process, thereby improving the yield rate.

[0020] The technical solution of the vacuum blister forming process of the blister box of the present invention is:

[0021] A vacuum blister forming process for a blister box comprises the following steps:

[0022] S10: Using the air thrust generated by the air pressure difference to maintain the plastic sheet at a set position;

[0023] S20: heating the plastic sheet at the set position to soften it, and maintaining the surface of the softened plastic sheet flat by air thrust;

[0024] S30: The softened plastic sheet is subjected to vacuum forming.

[0025] Further, step S10 includes:

[0026] S11: placing a plastic sheet in the sealed chamber so that the plastic sheet separates the sealed chamber into an upper chamber and a lower chamber;

[0027] S12: The upper chamber is evacuated to form an air pressure difference between the upper chamber and the lower chamber, and the air thrust generated by the air pressure difference is used to push the plastic sheet to a set position, and the air thrust is used to keep the force balance of the plastic sheet in the upper and lower directions.

[0028] The technical effect of the vacuum blister forming process for a blister box of the present invention is that when the vacuum blister forming process for a blister box of the present invention is used for processing, after the plastic sheet is softened by heat, the air thrust formed by the air pressure difference can balance the gravity of the plastic sheet itself, so the plastic sheet will not fall and stretch in the middle due to its own gravity. During the entire heating process, the plastic sheet always remains flat and is heated more evenly, which will not affect the subsequent blister process, thereby improving the yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of embodiment 1 of the vacuum blister forming device for a blister box of the present invention;

[0030] Figure 2 for Figure 1 A schematic diagram of the structure inside the blister box vacuum blister forming equipment;

[0031] Figure 3 for Figure 1 A cross-sectional view of a vacuum blister forming device for a blister box;

[0032] Figure 4 for Figure 1 A schematic diagram of the structure inside the lower box of the blister box vacuum blister forming equipment;

[0033] Figure 5 for Figure 4 A local enlarged view of point A in FIG.

[0034] Figure 6 for Figure 1 A schematic diagram of a partial structure inside an upper box of a blister box vacuum blister forming device;

[0035] Figure 7 for Figure 1 Schematic diagram of the state of the blister box vacuum blister forming equipment when in use;

[0036] Figure 8 for Figure 1 A schematic diagram of the state when the pressure difference between the upper chamber and the lower chamber is large when the vacuum blister forming device for the blister box is in use;

[0037] Fig. 9 for Figure 1 A schematic diagram of the structure of the control components of the blister box vacuum blister forming equipment;

[0038] in:

[0039] 100, upper box; 102, sealing ring; 104, guide groove; 200, lower box; 202, sealing groove; 204, blister mold; 206, vacuum generator; 208, blister cavity; 300, clamping assembly; 310, upper clamping frame; 320, lower clamping frame; 330, fixing screw; 400, spring pin; 500, heating unit; 510, lamp holder; 512, horizontal bracket; 514, vertical bracket ; 520, heating lamp; 600, exhaust assembly; 602, exhaust pipe; 604, air pump; 606, mounting bracket; 608, high-pressure container; 610, high-pressure pipeline; 612, piston chamber; 614, pressure relief valve; 702, lifting frame; 704, piston rod; 706, pulley; 708, plumb line; 710, heavy hammer; 712, power supply; 714, wire; 716, control pin; 800, plastic sheet. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings). In the description of the present invention, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0042] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0043] The vacuum blister forming device for a blister box of the present invention will be described below in conjunction with the accompanying drawings and specific implementations of the specification.

[0044] Embodiment 1 of the vacuum blister forming device for blister boxes of the present invention:

[0045] like Figure 1 , Figure 2 , Figure 3 and Figure 5 As shown, the vacuum blister forming device of the blister box of this embodiment includes an upper box 100, a lower box 200, a clamping assembly 300, a heating unit 500, a locking member, an air extraction assembly 600, a blister assembly and a control assembly. A sealing ring 102 is provided on the lower end surface of the upper box 100, and a sealing groove 202 for cooperating with the sealing ring 102 is provided on the upper end surface of the lower box 200. The upper box 100 and the lower box 200 can form a sealed chamber after being buckled together.

[0046] like Figure 2As shown, the blister assembly is arranged in the lower box body 200, and the blister assembly includes a blister mold 204 and a vacuum generator 206. The blister mold 204 is provided with a forming hole, and a blister cavity 208 is provided between the blister mold 204 and the bottom of the lower box body 200. The vacuum generator 206 is arranged on the outer peripheral surface of the lower box body 200, and the vacuum generator 206 is connected with the blister cavity 208 through a connecting channel on the lower box body 200.

[0047] like Figure 3 , Figure 4 and Figure 5 As shown, the clamping assembly 300 is arranged in a guide sliding manner in the lower box body 200 and is in sliding and sealing contact with the inner wall of the lower box body 200. The clamping assembly 300 includes an upper clamping frame 310 and a lower clamping frame 320, and also includes a fixing member for fixing the upper clamping frame 310 and the lower clamping frame 320 together, and the fixing member is specifically a fixing screw 330. The lower box body 200 is provided with a supporting step for supporting the lower clamping frame 320. The outer peripheral surfaces of the upper clamping frame 310 and the lower clamping frame 320 are both in sliding and sealing contact with the inner wall of the lower box body 200. The upper clamping frame 310 and the lower clamping frame 320 can clamp the plastic sheet 800 and drive the plastic sheet 800 to move up and down in the lower box body 200. The locking member is a spring pin 400 arranged on the lower clamping frame 320, and the lower box body 200 is provided with a locking hole for the spring pin 400 to be inserted after being ejected. When the upper clamping frame 310 and the lower clamping frame 320 drive the plastic plate 800 to slide upward to the position of the locking hole, the spring pin 400 pops out under the action of the spring and inserts into the locking hole, thereby locking the position of the clamping assembly 300 and the plastic plate 800 in the up and down directions.

[0048] like Figure 1 , Figure 2 and Figure 6 As shown, the heating unit 500 includes a lamp holder 510 and a heating lamp tube 520. The lamp holder 510 includes a horizontal bracket 512 and a vertical bracket 514 fixedly connected together. The horizontal bracket 512 is located in the upper box body 100. There are multiple heating lamp tubes 520 and they are installed on the horizontal bracket 512. The upper box body 100 is provided with a through hole. The vertical bracket 514 passes through the through hole and then extends out from the inner cavity of the upper box body 100. The vertical bracket 514 and the hole wall of the through hole are slidably sealed. At the same time, a guide groove 104 extending in the up and down directions is provided on the inner wall surface of the upper box body 100. The end of the horizontal bracket 512 extends into the guide groove 104. The vertical bracket 514 can slide up and down and drive the horizontal bracket 512 to move up and down in the guide groove 104.

[0049] like Figure 1 and Figure 2As shown, the air extraction component 600 includes an air extraction pipeline 602 and an air pump 604 arranged on the upper box body 100, the air inlet of the air extraction pipeline 602 is connected to the inner cavity of the upper box body 100, a mounting frame 606 is arranged on the upper surface of the upper box body 100, and the air pump 604 is installed on the mounting frame 606 and is connected to the air extraction pipeline 602. The air extraction component 600 also includes a high-pressure pipeline, which includes a high-pressure container 608 and a high-pressure pipeline 610 connected to the high-pressure container 608, the air inlet of the high-pressure pipeline 610 is connected to the air outlet of the air extraction pipeline 602, and a piston cavity 612 is arranged at the air outlet of the high-pressure pipeline 610. The upper box body 100 and the high-pressure container 608 are both connected to a pressure relief valve 614 to adjust the air pressure in the upper box body 100 and the high-pressure container 608 as needed.

[0050] like Figure 1 and Figure 2 As shown, the blister box vacuum blister forming equipment also includes a lifting assembly, which includes a lifting frame 702 and a piston rod 704 fixedly connected together. The lifting frame 702 is fixedly connected to the vertical bracket 514 of the lamp holder 510, and the piston rod 704 is guided and slidably arranged in the piston chamber 612.

[0051] like Figure 3 and Figure 6 As shown, in order to facilitate the upward movement of the clamping assembly 300 and the plastic sheet 800, a gravity balance assembly is also provided in the vacuum blister molding device of the blister box. The gravity balance assembly includes a winding piece, a vertical line 708 and a weight 710. The winding piece is a pulley 706 arranged on the inner wall of the upper box body 100. One end of the vertical line 708 is fixedly connected to the clamping assembly 300, and the other end passes around the pulley 706 and is fixedly connected to the weight 710. The weight of the weight 710 is equal to the sum of the weights of the clamping assembly 300 and the spring pin 400. When the air pressure difference is used to push the clamping assembly 300 and the plastic sheet 800 upward, the air thrust generated by the air pressure difference only needs to overcome the gravity of the plastic sheet 800 itself.

[0052] like Figure 2 , Figure 5 and Fig. 9 As shown, the control component is used to control the opening and closing of the air pump 604, including a power supply 712, a wire 714 and a control pin 716. The power supply 712 is provided with a power switch for controlling the on and off of the power supply 712. The control pin 716 is inserted into the locking hole on the lower box 200 and is used to conduct the wire 714. The control pin 716 has a connection position and a disconnection position. In the initial state, the control pin 716 is inserted into the locking hole and is located in the connection position. The wire 714 is in a passage state. Turning on the power supply 712 switch can start the air pump 604. When the spring pin 400 of the clamping assembly 300 is inserted into the locking hole, the spring pin 400 will push the control pin 716 to the disconnection position, the wire 714 is in an open circuit state, and the air pump 604 is turned off.

[0053] The working process of the vacuum blister forming equipment for blister boxes in this embodiment is as follows:

[0054] like Figure 3 and Figure 5 As shown, in the initial state, the lower clamping frame 320 of the clamping assembly 300 is supported by the supporting steps on the lower box body 200, the plastic sheet 800 is placed on the lower clamping frame 320, and then the upper clamping frame 310 is placed on the plastic sheet 800, and the upper clamping frame 310 and the lower clamping frame 320 are fixed together by fixing screws 330 to clamp the plastic sheet 800. At this time, the plastic sheet 800 has not been heated and is in a hard state.

[0055] like Figure 2 , Figure 4 , Figure 5 , Figure 7 and Fig. 9 As shown, the upper box body 100 is then covered on the lower box body 200 to form a sealed chamber. Since the inner wall guide seal of the clamping assembly 300 and the lower box body 200 cooperates, the clamping assembly 300 and the plastic sheet 800 separate the sealed chamber into an upper chamber and a lower chamber. At this time, the power switch 712 is turned on. At this time, the control pin 716 is in the connection position, the air pump 604 is started, and the air in the upper chamber above the plastic sheet 800 is sucked into the high-pressure container 608. The air pressure in the upper chamber is reduced, and there is an air pressure difference between the lower chamber and the upper chamber. The plastic sheet 800 is subjected to an upward air thrust. When the air thrust is sufficient to overcome the gravity of the plastic sheet 800, the plastic sheet 800 is 00 enters a force balance state. As the air pump 604 continues to pump air, the plastic sheet 800 and the clamping assembly 300 begin to slide and rise along the inner wall of the lower box body 200 under the action of the air thrust and the weight 710. When the clamping assembly 300 moves to the position of the locking hole on the lower box body 200, the spring pin 400 of the clamping assembly 300 is inserted into the locking hole under the action of the spring, and the control pin 716 is pushed to the disconnected position by the spring pin 400. The wire 714 is open, the air pump 604 is turned off, and the clamping assembly 300 and the plastic sheet 800 are fixed in the up and down directions. At this position, the air thrust is balanced with the gravity of the plastic sheet 800 itself. During this process, the high-pressure gas in the high-pressure container 608 pushes the piston rod 704 in the piston chamber 612 to rise, and the piston rod 704 drives the lamp frame 510 and the heating lamp tube 520 thereon to rise through the lifting frame 702, so that the heating lamp tube 520 is away from the lower chamber below the plastic plate 800, and Figure 2 , Figure 7 and Figure 8 As shown, the heavier the plastic sheet 800 is, the more gas is sucked into the high-pressure container 608, the higher the piston rod 704 rises, and the farther the heating lamp 520 is from the lower chamber.

[0056] The heating unit 500 is controlled to start heating the plastic sheet 800, and the plastic sheet 800 begins to soften. Since the air thrust generated by the air pressure difference is balanced with the gravity of the plastic sheet 800 itself, even if the plastic sheet 800 begins to soften, the middle part will not fall down and stretch due to its own gravity. During the entire heating process, the plastic sheet 800 always remains flat and is heated more evenly, which will not affect the subsequent blistering process, thereby improving the yield rate.

[0057] After heating is completed, turn off the power switch 712, press the control pin 716 to reset the spring pin 400 and unlock the clamping assembly 300, open the pressure relief valve 614, the vacuum degree of the upper cavity is weakened, the clamping assembly 300 and the softened plastic sheet 800 are lowered, and then the upper box 100 is lifted, the vacuum generator 206 is turned on, the pressure in the blister cavity 208 is reduced, and the plastic sheet 800 is close to the blister mold 204, thereby completing the blister operation.

[0058] Embodiment 2 of the vacuum blister forming device for blister boxes of the present invention:

[0059] In embodiment 1, the winding member is a pulley fixed on the inner wall of the upper box body. In this embodiment, the winding member is a winding post fixed on the inner wall of the upper box body, and the outer peripheral surface of the winding post is a smooth cylindrical surface.

[0060] The specific embodiment of the vacuum blister forming process of the blister box of the present invention comprises the following steps:

[0061] In step S10, the air thrust generated by the air pressure difference is used to maintain the plastic sheet at a set position. This step includes the following contents:

[0062] S11: placing a plastic sheet in the sealed chamber so that the plastic sheet separates the sealed chamber into an upper chamber and a lower chamber;

[0063] S12: The upper chamber is evacuated to form an air pressure difference between the upper chamber and the lower chamber, and the air thrust generated by the air pressure difference is used to push the plastic sheet to a set position, and the air thrust is used to keep the force balance of the plastic sheet in the upper and lower directions.

[0064] In step S20, the plastic sheet at the set position is heated to soften it, and the surface of the softened plastic sheet is maintained flat by air thrust, so that the plastic sheet is heated more evenly.

[0065] In step S30, the softened plastic sheet is subjected to vacuum forming, and the step includes the following contents:

[0066] S31: Depressurizing the upper chamber to allow the plastic sheet to fall steadily onto the mold;

[0067] S32: The blister mold is evacuated to form the softened plastic sheet.

[0068] When the above process is used for processing, after the plastic sheet is softened, the air thrust formed by the air pressure difference can balance the gravity of the plastic sheet itself. Therefore, the plastic sheet will not fall and stretch in the middle due to its own gravity. During the entire heating process, the plastic sheet always remains flat and is heated more evenly, which will not affect the subsequent blister process, thereby improving the yield rate.

[0069] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A vacuum blister forming device for blister boxes, characterized in that: include: upper box; A lower box body cooperates with the upper box body to form a sealed chamber; A heating unit, used for heating the plastic sheet in the sealed chamber; A clamping assembly is provided in a guide slide in the lower box body and is in sliding sealing contact with the inner wall of the upper box body. The clamping assembly is used to clamp the plastic sheet and cooperate with the plastic sheet to separate the sealed chamber into an upper chamber and a lower chamber. A locking piece is provided on the clamping assembly, and the locking piece is used to lock the clamping assembly in the lower box body in the up and down directions. An air extraction assembly, used for extracting air from the upper chamber; It also includes a lifting assembly, which is driven by the air extracted from the exhaust assembly and is used to control the heating unit to move in the up and down directions; The air extraction component includes an air extraction pipeline and an air pump arranged on the upper box body, the air inlet of the air extraction pipeline is connected to the inner cavity of the upper box body, and the air pump is connected to the air extraction pipeline; The air extraction component also includes a high-pressure pipeline, the air inlet of the high-pressure pipeline is connected to the air outlet of the air extraction pipeline, a piston cavity is arranged at the air outlet of the high-pressure pipeline, the lifting component includes a lifting frame and a piston rod fixedly connected together, the piston rod guide is slidably arranged in the piston cavity, and the lifting frame is fixedly connected to the heating unit; The clamping assembly includes an upper clamping frame and a lower clamping frame, and also includes a fixing member for fixing the upper clamping frame and the lower clamping frame together; The locking member is a spring pin arranged on the lower clamping frame, and the lower box body is provided with a locking hole for the spring pin to be inserted after being ejected; Also included is a control assembly for controlling the opening and closing of the air pump, the control assembly including a control pin extending into the locking hole, and the spring pin can push the control pin to close the air pump after being ejected; It is characterized in that it also includes a gravity balance component, which includes a winding piece, a vertical line and a weight. The winding piece is arranged on the inner wall of the upper box body, one end of the vertical line is fixedly connected to the clamping assembly, and the other end passes around the winding piece and is fixedly connected to the weight.

2. A vacuum blister forming process for a blister box, characterized in that: The method is realized by the vacuum forming device for forming a blister box according to claim 1, and comprises the following steps: S10: Using the air thrust generated by the air pressure difference to maintain the plastic sheet at a set position; S20: heating the plastic sheet at the set position to soften it, and maintaining the surface of the softened plastic sheet flat by air thrust; S30: performing vacuum forming on the softened plastic sheet; Step S10 includes: S11: placing a plastic sheet in the sealed chamber so that the plastic sheet separates the sealed chamber into an upper chamber and a lower chamber; S12: The upper chamber is evacuated to form an air pressure difference between the upper chamber and the lower chamber, and the air thrust generated by the air pressure difference is used to push the plastic sheet to a set position, and the air thrust is used to keep the force balance of the plastic sheet in the upper and lower directions.

Images