Film blowing process and film blowing machine

Abstract

The invention relates to the technical field of film blowing machines, and provides a film blowing process which comprises the following steps: S100, pressing a cylindrical film bubble into a double-layer sheet-shaped film, S200, carrying out reciprocating rotation traction on the double-layer sheet-shaped film, S300, carrying out secondary inflation expansion on the double-layer sheet-shaped film subjected to reciprocating rotation traction to form a film bubble, and S300, carrying out secondary inflation expansion on the double-layer sheet-shaped film subjected to reciprocating rotation traction to form a film bubble. S400, the secondary forming film bubbles are subjected to edge insertion and pressed into an M-shaped film, and S500, the formed M-shaped film subjected to edge insertion is rolled and pressed, the film is in a double-layer sheet shape during rotating traction, no formed M-shaped folded edge exists, the process sequence of the rotating action is before edge insertion rolling, the rotating action acts on a flat film body, thin and thin point dispersion is achieved, and the film is formed. According to the film blowing technology, the sealing and guiding device is used for sealing and guiding secondary formed film bubbles, the subsequent folded edges and the surface flatness of a film cannot be disturbed, direct pressing and rolling are conducted after edge inserting forming is conducted on the M-shaped folded edges, the M edges are in a stable state all the time, and dislocation and wrinkles cannot be generated due to rotation. And the edge inserting quality is improved.

Description

Technical Field

[0001] This invention relates to the field of blown film machine technology, specifically to a blown film process and a blown film machine. Background Technology

[0002] Traditional blown film machines typically employ two processes during film blowing: edge insertion and rotation. Edge insertion refers to guiding both sides of the film to a folded state, making its sides M-shaped. The rotary process addresses the issue that the thickness of the cylindrical film bubble extruded from the blow molding die is rarely perfectly uniform, and this thickness deviation is a systematic error. If a point on the film bubble is thicker, subsequent bubbles in that location will also be thicker, and vice versa. These uneven thicknesses accumulate at the same locations on the roll, resulting in uneven film roll thickness after winding, causing rib breakage and poor winding quality. To solve this problem, a rotary traction method is used. This involves a horizontal forward and reverse rotary traction device. The traction rollers reciprocate horizontally around the central axis of the circular blown film head at a certain angle. This causes the distribution of film thickness points along the axial direction of the roll to exhibit a wave-like pattern, effectively reducing the thickness deviation problem.

[0003] Based on the two processes mentioned above, in order to achieve edge folding while avoiding the problem of rib bursting caused by uneven thickness, a combination of rotation and insertion is adopted. However, in traditional methods, such as the Chinese invention patent CN109968645B entitled "Multifunctional Insertion Mechanism for Blown Film Equipment," an insertion mechanism is installed below the rotating traction device. This insertion mechanism includes two symmetrically arranged triangular insertion plate assemblies, which combine rotation and insertion to sequentially insert and rotate the film bubble. However, this method has shortcomings: 1. The formed M-shaped fold is prone to misalignment and displacement during subsequent rotation, leading to tangled wrinkles when the film is rolled up. In subsequent cutting processes, errors may occur in the positioning and cutting of the wrinkled areas, resulting in deviations in the finished product dimensions and increased material waste. Furthermore, during bag manufacturing, it is difficult to achieve uniform heat sealing at the wrinkles, easily leading to localized incomplete seals. Finally, the film with wrinkles has uneven strength and is prone to tearing at the wrinkles. In food packaging, daily necessities packaging, and other scenarios, poor sealing can lead to spoilage of the contents, leakage, and other problems, affecting product quality and safety.

[0004] 2. If the rotation process is abandoned in order to avoid misalignment of the M edge, the systematic thickness deviation of the film bubble will continue to accumulate, which can easily lead to the bursting of the film roll and poor winding quality. In addition, the thinner areas of the film are easily burned through during heat sealing due to insufficient heat resistance, resulting in sealing failure. The thicker areas are not heat-sealed and are easy to peel off because heat cannot penetrate to the inner layer. Summary of the Invention

[0005] To overcome the above-mentioned defects, embodiments of the present invention provide a blown film process and a blown film machine, which solves the technical problem that the pre-formed M-shaped fold is prone to misalignment and displacement during subsequent rotation in the related technology, resulting in entanglement wrinkles when the film is wound up. If the rotation process is abandoned in order to avoid M-edge misalignment, the systematic thickness deviation of the film bubble will continue to accumulate, which will easily lead to the film roll bursting and poor winding quality.

[0006] According to one aspect, at least one embodiment of the present invention provides a blown film process, comprising: S100, pressing a cylindrical film bubble into a double-layer sheet film; S200, The double-layer sheet film is reciprocated and rotated for traction; S300: The double-layer sheet film after reciprocating rotation and traction is inflated a second time to form a membrane bubble; S400: Insert the edges of the secondary molded film bubble and press it into an M-shaped film; S500, M-type film formed by winding up the sewn edges and pressing together.

[0007] For example, in a blown film process provided by at least one embodiment of the present invention, S300 includes: S310. Select two mutually spaced points for traction sealing of the double-layer sheet film after reciprocating rotation traction; S320. Inflate the double-layer sheet film 200 located between the two traction seals to expand it into a secondary-formed film bubble 300.

[0008] For example, in a blown film process provided in at least one embodiment of the present invention, S320 further includes: S321. Inflate the double-layer sheet film between the two traction seals using an inflator. The inflator moves synchronously with the double-layer sheet film and is pulled out before moving to the next traction seal.

[0009] For example, in a blown film process provided by at least one embodiment of the present invention, in S321, the inflation component is inflated at least once, and after the secondary forming film bubble is inflated, the maximum width at the last traction seal should be equal to the preset width of the M-type film product.

[0010] For example, in a blown film process provided by at least one embodiment of the present invention, the process further includes: S210, performing a width-direction correction on the double-layer sheet film after reciprocating rotation and traction.

[0011] For example, in a blown film process provided by at least one embodiment of the present invention, the process further includes: S410, performing secondary width direction correction on the M-shaped thin film formed by the inserted edge.

[0012] According to another aspect, at least one embodiment of the present invention provides a blown film machine, comprising: a film bubble extrusion molding device for melting and plasticizing plastic raw materials and extruding cylindrical film bubbles; A-frame guides and extrudes cylindrical membrane bubbles into double-layer sheet-like films; A rotary traction device for pulling a double-layer sheet-like film; The sealing guide device has two sets for pulling and sealing the upper and lower ends of the secondary forming bubble. The sealing guide device includes two rollers that roll against each other. The two rollers can roll against the two ends of the secondary forming bubble so that the secondary forming bubble remains sealed and expands under the action of inflation. An inserting device is used to insert edges into secondary-formed film bubbles; A winding device for winding up M-shaped film products that have been inserted and pressed together.

[0013] For example, in a blown film machine provided by at least one embodiment of the present invention, there is a roller gap between the two rollers of the sealing guide device, the two sets of sealing guide devices are respectively arranged on the upper and lower sides of the insert device, and the two roller gaps are located on the same vertical line.

[0014] For example, in a blown film machine provided in at least one embodiment of the present invention, the two rollers are a light shaft and a leather shaft, respectively. The leather shaft rolls and elastically presses against the peripheral wall of the light shaft, so that the air in the secondary forming film bubble located between the two sets of sealing guide devices is in a sealed state.

[0015] For example, in a blown film machine provided in at least one embodiment of the present invention, there is also: a correction device having two sets, one set located between the rotary traction device and the edge insertion device, for correcting the double-layer sheet film after reciprocating rotary traction, and the other set located between the edge insertion device and the winding device, for correcting the M-shaped film finished product formed after edge insertion. The alignment device includes a horizontally rotating frame and two parallel alignment rollers rotatably mounted on the rotating frame. The two alignment rollers are arranged horizontally and at intervals, and can rotate synchronously with the rotating frame to adjust the angle with the film.

[0016] The beneficial effects of this invention are as follows: In this invention, during rotational traction, the film is in a double-layer sheet state without a formed M-shaped fold. The rotational action only acts on the flat film body, achieving thickness dispersion and not disturbing subsequent folding. In subsequent processes, after the M-shaped fold is formed by inserting the edge, there is no further rotation process. After the fold is formed, it is directly pressed and rolled up. The M-edge remains in a stable state and will not be misaligned or wrinkled due to rotation. The flat and wrinkle-free M-shaped fold ensures accurate positioning during subsequent cutting, reduces finished product size deviation, reduces material waste, and makes the tension in the folded area more uniform during bag heat sealing, resulting in a stronger heat seal. When used at the end, the film has uniform strength and will not tear at the fold or wrinkle. In food packaging, daily necessities packaging, and other scenarios, it can effectively reduce the deterioration and leakage of contents, improving product quality and safety. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are merely some exemplary embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the exemplary embodiments of the present invention and these drawings without any creative effort.

[0018] Figure 1 This is a schematic diagram of a blown film process and blown film machine according to one embodiment of the present invention; Figure 2 for Figure 1 A magnified schematic diagram of the structure of part A in the diagram; Figure 3 for Figure 1 A schematic diagram of the sealing guide device in the embodiment; Figure 4 for Figure 1 A schematic diagram of the structure of the correction device located between the insertion device and the winding device in the embodiment.

[0019] In the diagram: 100, cylindrical film bubble; 200, double-layer sheet film; 300, secondary forming film bubble; 400, M-type finished film; 500, sealing guide device; 510, roller; 511, optical axis; 512, leather shaft; 520, roller gap; 600, edge insertion device; 700, correction device; 710, rotating frame; 720, correction roller; 800, film bubble extrusion molding equipment; 900, herringbone frame; 1000, rotary traction device; 1100, winding device. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it.

[0021] To keep the drawings concise, each drawing only schematically shows the parts relevant to the invention; these do not represent the actual structure of the product. Furthermore, for ease of understanding, in some drawings, only one of components with the same structure or function is schematically shown, or only one is labeled. In this document, "one" not only means "only one," but can also mean "more than one," and "several" includes "two" and "more than two."

[0022] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0024] In the description of this embodiment, terms such as "upper," "lower," "left," and "right" are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of description and simplification of operation, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0025] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] like Figure 1The diagram illustrates a blown film process according to an embodiment of the present invention, wherein S100 involves pressing a cylindrical film bubble 100 into a double-layer sheet film 200. A practical example of this step is as follows: polyethylene granules are fed into a film bubble extrusion molding equipment 800. Specifically, this equipment includes an extruder hopper for receiving the polyethylene granules. Through screw conveying, shearing, extrusion, and barrel heating, the solid raw material melts into a uniform molten plastic melt. Under the pressure of the barrel, the melt is extruded through the annular flow channel of the annular die, forming a continuous cylindrical hollow film bubble. Simultaneously, a cooling fan blows uniform cold air outwards from the film bubble, rapidly cooling and solidifying the high-temperature molten film bubble to prevent adhesion and deformation, ensuring the stability of the film bubble's shape. The cooled and solidified cylindrical film bubble 100 is conveyed upwards to a herringbone frame 900, which consists of two symmetrically arranged inclined guide plates. Through the symmetrical extrusion action of the herringbone frame 900, the cylindrical film bubble 100 is gradually flattened and pressed along the axial direction to form a double-layer sheet film 200.

[0027] Further, in S200, the double-layer sheet film 200 is reciprocated and rotated. A practical reference example of this step is: the double-layer sheet film 200 after pressing is conveyed to the rotary traction device 1000 through the guide roller. The rotary traction device 1000 can be a horizontal forward and reverse rotary traction device. This device is a conventional device currently in use, and its principle will not be described in detail here. At this time, the film is in a double-layer sheet state without a formed M-shaped fold, and the rotation action only acts on the film itself.

[0028] Further, in step S300, the double-layer sheet film 200, after reciprocating rotational traction, undergoes secondary inflation to expand into a membrane bubble. A practical example of this step is as follows: the double-layer sheet film 200, after rotational traction, enters the secondary inflation area through a first sealing guide device 500. After inflation in the secondary inflation area, it is removed through a second sealing guide device 500. By setting two sealing guide devices 500, gas leakage during inflation is ensured. It should be noted that S300 is only a necessary process step during the initial equipment commissioning. After equipment commissioning is completed, subsequent film inflation is no longer required. Because of the two sealing guide devices 500, the gas inside the secondary-formed membrane bubble 300 can be retained for a relatively long time. In the actual example, the membrane bubble gas can be used for approximately one week after a single inflation.

[0029] Further, in step S400, the secondary-formed film bubble 300 is inserted and pressed into an M-shaped film product 400. A practical reference example of this step is as follows: the secondary-formed film bubble 300 is conveyed to the insertion device 600. The insertion device 600 is a conventional device currently in use, and its principle will not be elaborated here. The insertion device 600 gradually guides the two sides of the secondary-formed film bubble 300 to a folded state, so that the sides form a regular M-shaped fold. After the insertion is formed, the M-shaped folded film bubble is pressed again by a subsequent sealing guide device 500 to fix the shape of the M-shaped fold. At the same time, the secondary-formed film bubble 300 is pressed into an M-shaped film product 400, eliminating slight wrinkles at the fold and ensuring that the film body is flat overall.

[0030] Finally, S500, the M-shaped film product 400 is formed by winding up the inserted edges and pressing it together. After pressing and shaping, the M-shaped film product 400 is guided by rollers to adjust the conveying path and is wound up at a uniform speed by the winding rollers of the winding machine. During the winding process, the winding tension is adjusted by the tension control system to ensure that the film roll is wound tightly and flat, without problems such as bursting, wrinkles, or deviation, and finally a qualified finished film roll is formed.

[0031] Based on the steps in the above example, the related technology adopts the method of inserting the edge first and then rotating. When the formed M-shaped folded edge is rotated and pulled, it will cause the folded edge to be misaligned and wrinkled, which will lead to problems such as cutting size deviation, poor heat sealing of bag making, tearing and leakage during end use. This example employs a novel process of rotating first and then inserting the edge. During rotation and traction, the film is in a double-layer sheet state without a formed M-shaped fold. The rotation only acts on the flat film body, achieving thickness dispersion and avoiding disturbance to subsequent folding. In subsequent processes, after the M-shaped fold is formed by inserting the edge, there is no further rotation process. After the fold is formed, it is directly pressed and rolled up. The M-edge remains stable and will not be misaligned or wrinkled due to rotation. The flat and wrinkle-free M-shaped fold ensures accurate positioning during subsequent cutting, reduces finished product size deviation, reduces material waste, and results in more uniform tension in the folded area during bag heat sealing, leading to a stronger heat seal. The film strength is more uniform during end use, preventing tearing at folds or wrinkles. In food packaging, daily necessities packaging, and other scenarios, this effectively reduces the risk of spoilage and leakage of contents, improving product quality and safety.

[0032] Furthermore, in related technologies, when inserting the edge first and then rotating, the edge insertion relies on the internal air pressure support of the initial cylindrical membrane bubble (100). However, in this process, the rotating traction device 1000 is usually placed above the edge insertion device 600, meaning that rotational traction is performed immediately after edge insertion. In this process, rotation causes fluctuations in the membrane bubble air pressure, resulting in unstable folded edge dimensions. If the sheet film is directly edged, without internal support, the folded edge is prone to collapse and irregular shape. In this example, the double-layer sheet film 200 after rotational traction is re-inflated to provide uniform internal support force for the edge insertion. Moreover, the conveying structure is stable before and after the second edge insertion, which does not cause significant fluctuations inside the membrane bubble, thus improving the edge insertion quality.

[0033] In a further example, S300 includes two steps: S310, selecting two spaced-apart points on the reciprocatingly rotated and drawn double-layer sheet film 200 for traction sealing; and S320, inflating the double-layer sheet film 200 located between the two traction seals to expand it into a secondary-formed bubble 300. In a specific example corresponding to S310, the reciprocatingly rotated and drawn double-layer sheet film 200 first enters the first sealing guide device 500. The traction sealing process step mentioned in this example corresponds to the sealing guide device 500; therefore, mentioning the sealing guide device 500 indicates a traction sealing point. The sealing guide device 500 serves to guide and transport the double-layer sheet film 200, while also providing a sealing effect. In one example, the sealing guide device 500 is composed of two rollers 510, one of which includes at least one leather roller 512 or other roller 510 with an elastic outer wall material, and the other is preferably an optical roller 511. In the preferred example, the elastic pressure between the leather roller 512 and the optical roller 511 can both transport the double-layer sheet film 200 and provide a flexible sealing effect. Subsequently, after the initial segment of the membrane passes through the first sealing guide device 500, an inflation device, such as a needle-shaped inflation head or an air gun, is used to pierce through the initial segment of the membrane and inject gas into the membrane cavity. Due to the sealing effect of the first sealing guide device 500, the injected gas will not leak from the inlet end, and the end of the initial segment of the membrane is usually sealed. Therefore, the air pressure inside the membrane bubble begins to gradually build up and remain stable, preparing for the edge insertion device 600 to perform edge insertion. A second sealing guide device 500 is also set at the subsequent station of the edge insertion device 600. The two sealing guide devices 500 cooperate with each other to form a stable seal for the gas inside the intermediate membrane bubble, ensuring that the folded edge shape does not spring back and deform. In addition, the second sealing guide device 500 simultaneously applies a pressing force while sealing, pressing the edged membrane bubble into an M-shaped finished membrane product 400. It should be noted that the description of the sealing guide devices 500 mentioned above: the first and the second correspond to the one before and the one after the traction seal, respectively.

[0034] Based on the steps in the example above, the inlet seal prevents gas leakage, ensuring that the bubble pressure reaches the preset value after inflation. The outlet seal prevents pressure leakage, ensuring that the bubble remains full and stable throughout the insertion process. Insertion is completed within the pressure stabilization range, the bubble is supported by uniform air pressure, and the guiding force of the insert plate on the bubble edge is more precise. During folding, misalignment due to bubble movement is prevented, ultimately improving the consistency of the width and angle dimensions of the M-shaped fold. Furthermore, due to the dispersion effect of the reciprocating rotation traction on the thickness points during the initial inflation, the air pressure is constant and evenly distributed inside the bubble after secondary inflation, preventing localized bulges and depressions.

[0035] If the method of inserting the edge first and then rotating is adopted, that is, first forming the M-shaped fold and then rotating and pulling the film with the M-shaped fold, this process has the limitation that the M-shaped fold formed after inserting the edge has a thickness of several times that of the flat film. This causes the thickness, rigidity, and tension of the two sides of the film to differ from the middle flat film area. When the traction clamping rollers hold and rotate back and forth, the clamping force and traction force on the thick M-shaped fold area and the thin flat film area are inconsistent, thus affecting the thickness dispersion effect. In this example, the double-layer sheet film 200 has no M-shaped fold, and the overall thickness and tension are uniform. When rotating, the force of the traction clamping rollers can be transmitted to the entire width of the film more evenly. The film can follow the rotation trajectory and move smoothly. The thickness points can be dispersed in a wave pattern along the preset path, achieving a better thickness correction effect. Furthermore, if the method of inserting the edges first and then rotating is adopted, the thickness points of the film are not dispersed by rotation and traction before insertion. When inserting the edges under the premise of systematic thickness deviation, the thick areas may be difficult to bend to the preset angle due to the strong support force, which may result in problems such as excessively large folding angle and excessive width. The thin areas are easily squeezed by the inserting plate due to the weak support force, resulting in problems such as excessively small folding angle, excessively narrow width, or even collapse. Ultimately, it may lead to uneven M-shaped folding width and angle of the entire film, affecting the quality of the finished product.

[0036] In a further example, during the overall equipment commissioning phase, S320 includes S321, inflating the double-layer sheet film 200 between two traction seals using an inflator inserted into it. The inflator moves synchronously with the double-layer sheet film 200 and is pulled out before reaching the next traction seal. One specific implementation of this step is as follows: First, the width of the pre-formed M-shaped film 400 needs to be determined as a criterion for judging the degree of inflation. The double-layer sheet film 200, after reciprocating rotation and traction, is uniformly conveyed to the secondary inflation area. Then, the inflator, such as a needle-shaped inflator head, is inserted into the initial section of the double-layer sheet film 200, i.e., the unexpanded starting area, for inflation. Simultaneously, the inflator moves synchronously with the double-layer sheet film 200. As an example of synchronous movement, the inflator can be connected to a flexible air supply line to move with the film. During inflation, the inflation amount needs to be controlled to achieve the final goal of making the width at the next traction seal equal to the pre-set width of the M-shaped film 400. During the process, a debugging step is required. The debugging step is as follows: During the initial inflation, the maximum width of the membrane bubble formed after inflation should be slightly larger than the width of the pre-formed M-shaped film 400. This allows for shrinkage space after the gas is removed from the inflatable component. When the moving inflatable component is transported with the film to the front of the sealing guide device 500 after insertion, inflation should be stopped and the inflatable component should be removed from the film. At the same time, it is necessary to ensure that the flexible air path and the inflatable component do not interfere with the insertion device 600. As an example, in order to ensure that the inflation can reach the preset value after one insertion, the film conveying speed during the initial inflation stage can be appropriately slowed down to facilitate observation and inflation operation. After inflation reaches the normal standard, the speed can be restored to normal.

[0037] Subsequently, the inflation component is removed, the membrane bubble is deflated, and the film with the inflation component insertion hole is removed from the next traction seal. The gas inside the secondary forming membrane bubble 300 is stable. At this point, the width of the next traction seal is equal to the preset width of the M-shaped film product 400. It should be noted that the width of the M-shaped film formed after edge insertion and pressing is narrower than the width of the film located at the previous traction seal. Therefore, the width of the film corresponding to the next traction seal is used as the standard. It should be noted that this example emphasizes inflation adjustment in the initial section of the double-layer sheet film 200. The film wound up during the initial adjustment process is scrap and not considered as the main product. Therefore, puncturing does not affect the overall film quality.

[0038] In a further example, although the double-layer sheet film 200 has undergone optimized thickness distribution after reciprocating rotational traction, it may still exhibit lateral deviation in the width direction due to force fluctuations during rotational traction and slight offsets in the conveying path. Therefore, a first width correction process is implemented. After secondary inflation, the film bubble is formed into an M-shaped film product 400 via the edge insertion device 600 and sealing guide. During the edge insertion process, slight fluctuations in the film bubble and minor errors in the insertion plate guide may cause the M-shaped film product 400 to exhibit lateral deviation in the width direction again. Therefore, a second width correction process is implemented. Even if the initial correction is accurate during the edge insertion process, fluctuations in film bubble inflation and minor errors in the insertion plate guide may still cause slight lateral deviations in the M-shaped film product 400. If directly wound up, the deviation will continue to accumulate, resulting in defects such as wavy edges and uneven sides in the final film roll. Subsequent cutting requires the removal of more edge material, causing material waste. During bag making, the uneven edges make accurate positioning impossible, leading to dimensional deviations in the finished product. The secondary correction calibrates the M-shaped film product 400 after edge insertion, adjusting the film's lateral orientation to ensure it smoothly enters the winding process along the preset path of the winding device 1100. During winding, the two edges of the film remain aligned, ultimately forming a neat, offset film roll. This neat film roll eliminates the need for extensive edge trimming during subsequent cutting, reducing material waste.

[0039] like Figures 1-3 The image shows a blown film machine according to an embodiment of the present invention, including a film bubble extrusion molding device 800 for melting and plasticizing plastic raw materials and extruding a cylindrical film bubble 100, a rotary traction device 1000 for guiding and extruding the cylindrical film bubble 100 into a double-layer sheet film, and a traction device 1000 for pulling the double-layer sheet film 200, and an edge-inserting device 600 for inserting edges into the secondary-formed film bubble 300. All of these devices have been exemplified and described above and will not be repeated here. In addition, it also includes sealing and guiding devices 500 at both ends for pulling and sealing the secondary-formed film bubble 300. See also... Figure 2 The sealing guide device 500 includes two rotatably arranged rollers 510, with a roller gap 520 formed between the two rollers 510 for the film to pass through. Preferably, one roller 510 is a leather roller 512, and the other roller 510 is a smooth roller 511. A driving element such as a cylinder can be used to drive the smooth roller 511 or the leather roller 512 closer to the other roller 510, forming a rolling pressure, thereby achieving the effects of guiding and end sealing. (Continue reading...) Figure 2Two sealing guide devices 500 are respectively positioned above and below the insertion device 600, and the two roller gaps 520 are located on the same vertical line. This means that the film, after being rotated and pulled, inflates after passing through the upper sealing guide device 500, then enters the lower insertion device 600 for insertion, and finally exits through the lowest sealing guide device 500. This ensures that the film bubble's conveying path is vertically straight, without any lateral bends or offset inflection points. On one hand, the straight path reduces the friction contact points between the film and equipment components, avoiding defects such as film scratches and thinning caused by path bends. On the other hand, vertical conveying ensures that the film bubble's gravity is aligned with the conveying direction, allowing for smooth movement without additional lateral traction force, and preventing film bubble offset and wrinkles caused by uneven lateral force. Secondly, the upper sealing guide seals the upper end of the membrane bubble, and the lower sealing guide seals the lower end of the membrane bubble, forming a vertical coaxial layout. This ensures that the side walls of the sealing area are gapless and the force is symmetrical. During secondary inflation, the gas can diffuse evenly in the vertical direction, and the radial expansion of the membrane bubble is consistent. This prevents the pressure imbalance problem of one side bulging and the other side collapsing. From the perspective of the insertion process, the insertion device 600 guides and folds the membrane bubble within the vertical pressure stabilization zone. The uniform air pressure provides stable support for the edge of the membrane bubble. The guiding force of the insertion plate on both sides of the edge is relatively symmetrical, which makes the width of the formed M-shaped fold consistent and the angle regular, avoiding fold skewing and dimensional deviation caused by membrane bubble displacement.

[0040] In some examples, the web-correcting device 700 mentioned in the above process includes a horizontally rotatable frame 710 and two parallel web-correcting rollers 720 rotatably mounted on the frame 710. The frame 710 is equipped with an independently driven motor, which drives the frame 710 to rotate horizontally and simultaneously rotates the two parallel web-correcting rollers 720, thereby adjusting the angle between the web-correcting rollers 720 and the film. For details, see [link to documentation]. Figure 4 A web-correcting device 700 is located between the edge-insertion device 600 and the winding device 1100. The two web-correcting rollers 720 of this device 700 are at the same height and are higher than the winding device 1100 and the edge-insertion device 600. This allows the M-shaped film product 400, after passing through the web-correcting device 700, to adhere to the two web-correcting rollers 720. Thus, when the two web-correcting rollers 720 rotate with the rotating frame 710, they can effectively correct the web alignment of the film. Simultaneously, Figure 1The two alignment rollers 720 of the middle alignment device 700 are located at different heights, allowing the rotated and pulled film to move from below the first alignment roller 720 to above the second alignment roller 720. This ensures the film adheres to the two alignment rollers 720, creating a certain tension. Supported and guided by the two parallel alignment rollers 720, the film is aligned and calibrated along the adjusted path. The M-shaped film product 400, after edge pressing, may experience new lateral offsets due to edge guidance errors or minor fluctuations in membrane bubble pressure. Direct winding will result in uneven film roll edges. The second alignment device 700 is then activated; its working principle is the same as the first group and will not be described in detail here.

[0041] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A blown film process, characterized in that, include: S100, The cylindrical membrane bubble (100) is pressed into a double-layer sheet film (200); S200, reciprocating rotational traction of the double-layer sheet film (200); S300, inflate the double-layer sheet film (200) after reciprocating rotation and traction to expand it into a secondary-formed film bubble (300); S400: Insert the edges of the secondary molded film bubble (300) and press it into an M-shaped film product (400); S500, M-type film finished product (400) formed by winding up the sewn edges and pressing them together.

2. The blown film process according to claim 1, characterized in that, The S300 includes: S310. Select two mutually spaced points on the double-layer sheet film (200) after reciprocating rotational traction and perform traction sealing; S320. Inflate the double-layer sheet film (200) located between the two traction seals to expand it into a secondary-formed film bubble (300).

3. The blown film process according to claim 2, characterized in that, The S320 includes: S321. Inflate the double-layer sheet film (200) between the two traction seals by inserting an inflator into it. The inflator moves synchronously with the double-layer sheet film (200) and is pulled out before moving to the next traction seal.

4. The blown film process according to claim 3, characterized in that, In S321, the inflatable component is inflated at least once, and after the secondary molding bubble (300) is inflated, the width of the second traction seal should be equal to the preset width of the M-type film product (400).

5. The blown film process according to claim 1, characterized in that, Also includes: S210. Perform a width-direction correction on the double-layer sheet film (200) after reciprocating rotational traction.

6. The blown film process according to claim 1, characterized in that, Also includes: S410. Perform secondary width direction correction on the M-shaped thin film finished product (400) formed by the insertion edge.

7. A blown film machine, characterized in that, The blown film process according to any one of claims 1-6 includes: A film bubble extrusion molding equipment (800) is used to melt and plasticize plastic raw materials and extrude cylindrical film bubbles (100); A chevron (900) is used to guide and extrude a cylindrical membrane bubble (100) into a double-layer sheet film (200); A rotary traction device (1000) is used to traction the double-layer sheet film (200); The sealing guide device (500) has two sets for pulling and sealing the upper and lower ends of the secondary molded bubble (300). The sealing guide device (500) includes two rollers (510) that roll against each other. The two rollers (510) can roll against both sides of the ends of the secondary molded bubble (300) so that the secondary molded bubble (300) remains sealed and expands under the action of inflation. An inserting device (600) is used to insert the edges of the secondary molded bubble (300); A winding device (1100) is used to wind up the M-shaped film product (400) that has been inserted and pressed together.

8. A blown film machine according to claim 7, characterized in that, The sealing guide device (500) has a roller gap (520) between the two rollers (510). The two sets of sealing guide devices (500) are respectively arranged on the upper and lower sides of the insert device (600), and the two roller gaps (520) are located on the same vertical line.

9. A blown film machine according to claim 8, characterized in that, The two rollers (510) are a light shaft (511) and a leather shaft (512), respectively. The leather shaft (512) rolls and elastically presses against the peripheral wall of the light shaft (511), so that the air in the secondary forming bubble (300) located between the two sets of sealing guide devices (500) is in a sealed state.

10. A blown film machine according to claim 9, characterized in that, Also includes: The correction device (700) has two sets. One set is located between the rotary traction device and the edge insertion device, and is used to correct the double-layer sheet film (200) after reciprocating rotary traction. The other set is located between the edge insertion device (600) and the winding device (1100), and is used to correct the M-shaped film product (400) formed after edge insertion. The correction device (700) includes a horizontally rotatable frame (710) and two parallel correction rollers (720) rotatably mounted on the frame (710). The two correction rollers (720) are arranged horizontally and at intervals, and can synchronously rotate with the frame (710) to adjust the angle with the film.

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