Film blowing forming device and control device

Abstract

The present invention addresses the problem of providing a blow molding device that improves the commercial value. The blow molding apparatus includes: an air supply / exhaust device that supplies / exhausts air to / from air bubbles; and a control device (126) for controlling the air supply and exhaust device. When the diameter of the bubble is changed, the control device (126) controls the difference between the air supply / exhaust amount of the air supply / exhaust device on the basis of information relating to the bubble before or during the change of the diameter of the bubble.

Description

Technical Field

[0001] This application claims priority based on Japanese Patent Application No. 2023-221878 filed on December 27, 2023. The entire content of the Japanese application is incorporated herein by reference.

[0002] The present invention relates to a blown film forming apparatus and a control apparatus. Background Art

[0003] There is known a blown film forming apparatus in which a molten molding material is extruded from a die into a tubular shape, air is blown into the inside thereof to expand it, a thin film (hereinafter also referred to as a bubble) is formed, and the thin film is folded to form a flat film, and the flat film is wound up to form a roll body.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017-177348

[0005] There is known a case where the diameter of the bubble and the width (fold diameter) of the flat film are changed by controlling the difference between the air supply amount and the air discharge amount to the bubble. At this time, there is sometimes a situation where the vibration of the bubble does not converge even after waiting for a long time. If the unstable state is entered, it is necessary to take measures such as temporarily changing the molding conditions, so it takes time to change the width of the flat film, and the loss of the molding material increases. Summary of the Invention

[0006] The present invention has been made in this situation, and one exemplary object of one embodiment thereof is to provide a blown film forming apparatus capable of changing the fold diameter without making the bubble unstable.

[0007] In order to solve the above problems, a blown film forming apparatus according to one embodiment of the present invention includes: a gas supply / discharge device that supplies and discharges gas to / from a bubble; and a control device that controls the gas supply / discharge device. When changing the diameter of the bubble, the control device controls the difference between the gas supply amount and the gas discharge amount of the gas supply / discharge device based on information related to the bubble before or during the change in the bubble diameter.

[0008] Another embodiment of the present invention is a control device. The device is a control device for a blown film forming apparatus having a gas supply / discharge device that supplies and discharges gas to / from a bubble, and when changing the diameter of the bubble, controls the difference between the gas supply amount and the gas discharge amount of the gas supply / discharge device based on information related to the bubble before or during the change in the bubble diameter.

[0009] In addition, any combination of the above components that can be mutually replaced among methods, devices, systems, etc., the components or expressions of the present invention are also effective as embodiments of the present invention.

[0010] Advantages of the Invention

[0011] According to the present invention, a blown film forming apparatus capable of changing the folding width without destabilizing bubbles can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 FIG. is a diagram showing the basic structure of the blown film forming apparatus according to the embodiment.

[0013] Figure 2 schematically shows Figure 1 the functions and configuration of the control device of.

[0014] In the figure: 100 - blown film forming apparatus, 102 - die, 120 - gas supply and exhaust device, 122 - gas supply device, 124 - exhaust device, 126 - control device, 132 - exhaust mechanism, 134 - air damper. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. The embodiments are illustrative of the invention and not restrictive, and all features and combinations thereof described in the embodiments are not necessarily essential features of the invention. The same or equivalent components, parts, and processes shown in the respective drawings are denoted by the same reference numerals, and repeated descriptions are appropriately omitted.

[0016] Figure 1 FIG. is a diagram showing the basic structure of the blown film forming apparatus 100 according to the embodiment. The blown film forming apparatus 100 includes a die 102, a cooling unit 104, a pair of guiding units 106, a tractor 108, a winder 110, a bubble state detection unit 114, a gas supply and exhaust device 120, and a control device 126.

[0017] The molten molding material is extruded from the annular extrusion port 102a formed in the die 102 into a cylindrical shape. Gas is supplied at an appropriate time inside the extruded cylindrical molding material, and the molding expands into a thin-walled film in a cylindrical shape (hereinafter, also referred to as "bubble"). Although not limited thereto, the case where the gas is air will be described below.

[0018] The cooling unit 104 is disposed above the die 102. The cooling unit 104 blows cooling air to the bubble to cool the bubble. A pair of guiding units 106 are disposed above the cooling unit 104. The pair of guiding units 106 guide the bubble to the tractor 108. The tractor 108 is disposed above the guiding unit 106. The tractor 108 includes a pair of pinch rollers 118. The pair of pinch rollers 118 are driven to rotate by a motor (not shown), and while pulling up the guided bubble, it is folded into a flat shape. Hereinafter, the bubble, that is, the film folded into a flat shape will also be referred to as a flat film. The winder 110 winds up the flat film to form a film roll 111.

[0019] The bubble state detection unit 114 detects various information related to the state of the bubbles required to detect and determine the allowable value of the air supply / discharge difference described later. Therefore, the bubble state detection unit 114 includes one or more appropriate sensors for detecting information related to the state of the required bubbles.

[0020] For example, the bubble state detection unit 114 may include a thickness detection sensor disposed between the cooling unit 104 and the pair of guide units 106. The thickness detection sensor detects the thickness of the bubbles at each position in the circumferential direction while rotating around the bubble. The thickness data detected by the thickness detection sensor is sent to the control device 126.

[0021] And, for example, the bubble state detection unit 114 may include a width detection sensor disposed between the tractor 108 and the winder 110. The width detection sensor detects the flat film width (fold diameter) at a predetermined cycle. The width data detected by the width detection sensor is sent to the control device 126.

[0022] And, for example, the bubble state detection unit 114 may include a shape detection sensor disposed between the cooling unit 104 and the pair of guide units 106. The shape detection sensor detects the bubble shape at each position in the circumferential direction while rotating around the bubble. The shape detection sensor may be, for example, a visible light camera. The bubble shape at each position in the circumferential direction can be detected by a plurality of shape detection sensors arranged, for example, at equal intervals in the circumferential direction. In this case, the shape detection sensor does not need to rotate around the bubble. The shape data detected by the shape detection sensor is sent to the control device 126.

[0023] The air supply / discharge device 120 supplies and discharges air to and from the bubble. The air supply / discharge device 120 changes the bubble diameter and the flat film width by changing the air supply / discharge difference to the bubble. The air supply / discharge device 120 may also serve as an internal cooling device that supplies cold air to the bubble and cools the bubble from the inside.

[0024] The air supply / discharge device 120 includes an air supply device 122 and an exhaust device 124.

[0025] The air supply device 122 supplies air into the bubble. The air supply device 122 is not particularly limited, but in the illustrated example, it includes an air supply mechanism 128. The air supply mechanism 128 may be an air supply blower. The air supply mechanism 128 supplies air into the bubble via the supply path 130 under the control of the control device 126. The air supply mechanism 128 can adjust the supply flow rate of the air. In addition, the air supply device 122 may also include a damper for adjusting the supply flow rate of the air.

[0026] The exhaust device 124 discharges the air inside the bubbles. The exhaust device 124 is not particularly limited, but in the illustrated example, it includes an exhaust mechanism 132 and a damper 134. The exhaust mechanism 132 can be an exhaust blower or an exhaust pump. The exhaust mechanism 132 discharges the air inside the bubbles via an exhaust path 136 under the control of the control device 126. The exhaust mechanism 132 can adjust the exhaust flow rate of the air. The damper 134 adjusts the exhaust flow rate of the air passing through the exhaust path 136. Regarding the adjustment of the exhaust flow rate, the damper 134 has a higher control responsiveness than the exhaust mechanism 132. Also, compared with the exhaust mechanism 132, the damper 134 can adjust the exhaust flow rate more finely. That is, regarding the adjustment of the exhaust flow rate, the resolution of the damper 134 is higher than that of the exhaust mechanism 132.

[0027] The control device 126 is a device that uniformly controls the blown film forming device 100.

[0028] Figure 2 It is a block diagram schematically showing the functions and configuration of the control device 126. Each functional block shown here can be implemented by elements or mechanical devices represented by a computer's CPU in terms of hardware, and is implemented by a computer program or the like in terms of software. Here, the functional modules implemented through the cooperation of these are described. Therefore, those skilled in the art can understand that these functional modules can be implemented in various forms through a combination of hardware and software.

[0029] The control device 126 includes a communication unit 140 that performs communication processing with the bubble state detection unit 114 according to various communication protocols, a U / I unit 142 that accepts operation inputs made by the user and causes the display unit to display various screens, a data processing unit 144 that performs various data processing based on the data obtained from the communication unit 140 and the U / I unit 142, and a data storage unit 146 that stores the data referred to and updated by the data processing unit 144. The U / I unit 142 can, for example, accept an instruction to change the film width.

[0030] The data processing unit 144 includes a receiving unit 150 and an air supply and exhaust control unit 152. Additionally, the components of the data processing unit 144 only represent the components of concern in the present embodiment.

[0031] The receiving unit 150 receives various data related to the state of the bubble from the bubble state detection unit 114.

[0032] The air supply and exhaust control unit 152 controls the supply of air into the bubble through the air supply device 122 and the exhaust of air from the bubble through the exhaust device 124. In particular, the air supply and exhaust control unit 152 controls the difference between the air supply amount Q1 into the bubble and the air exhaust amount Q2 from the bubble, that is, the air supply and exhaust amount difference (Q1 - Q2), and sets the bubble diameter and the flat film width to desired sizes. When increasing the bubble diameter and the flat film width, the control device 126 temporarily increases the air supply and exhaust amount difference to a positive value. In other words, the internal pressure of the bubble is increased. When decreasing the bubble diameter and the width of the flat film, the control device 126 temporarily increases the air supply and exhaust amount difference to a negative value. In other words, the internal pressure of the bubble is decreased.

[0033] However, when changing the bubble diameter and the flat film width during molding, the flat film during this change process becomes a loss. Therefore, from the perspective of reducing the loss of the molding material, it is also considered preferable to increase the air supply and exhaust amount difference to the bubble positively or negatively. However, if the air supply and exhaust amount difference to the bubble is excessively increased to a positive or negative value, in other words, if the bubble diameter changes rapidly, the bubble may fall into an unstable state. The unstable state of the bubble refers to a state where the bubble vibrates and the vibration does not converge even after a specified period (for example, 15 minutes after reaching the target value). The state where the vibration converges refers to a state where the amplitude of the vibration is below a specified value (for example, the target value ±2%). When the bubble falls into an unstable state, it is necessary to take measures such as temporarily changing the molding conditions. Instead, it takes time to change the flat film width, and the loss of the molding material becomes more.

[0034] As a result of the present inventor's investigation into the destabilization of the bubble, it was recognized that if the air supply and exhaust amount difference exceeds a certain value, the bubble may fall into an unstable state, and this value varies depending on the "ease of expansion and contraction of the bubble" or the "amount of air in the bubble" at this time.

[0035] Therefore, in the present embodiment, when changing the bubble diameter and the flat film width, the air supply and exhaust control unit 152 determines an index value of the air supply and exhaust amount difference at which the bubble will not fall into an unstable state, and controls the air supply and exhaust amount difference so as not to exceed this index value or an allowable value based on the index value. In the present embodiment, the index value can also be regarded as the upper limit of the air supply and exhaust amount difference. The allowable value is a value obtained by multiplying the safety factor (for example, 0.9) by the index value. The air supply and exhaust control unit 152 can control the air supply and exhaust amount difference so as not to exceed the index value. Alternatively, the air supply and exhaust control unit 152 can also control the air supply and exhaust amount difference so as not to exceed the allowable value. In short, by controlling the air supply and exhaust amount difference so as not to exceed the index value or the allowable value, the bubble will not fall into an unstable state and the bubble diameter and the flat film width can be changed, so that the loss of the molding material can be reduced.

[0036] In addition, the easier the bubble can expand and contract, the more rapidly the bubble diameter changes, so the bubble is likely to fall into an unstable state. Also, even when the difference in the supply and exhaust amounts is the same, the smaller the amount of air in the bubble, the greater these rates of change, and the more rapidly the bubble diameter changes, so the bubble is likely to fall into an unstable state. Therefore, regarding the index value of the difference in the supply and exhaust amounts, the easier the bubble can expand and contract, the smaller the index value becomes, and the more difficult it is for the bubble to expand and contract, the larger the index value becomes. Also, regarding the index value of the difference in the supply and exhaust amounts, the smaller the amount of air in the bubble, the smaller the index value becomes, and the larger the amount of air in the bubble, the larger the index value becomes.

[0037] The supply and exhaust control unit 152 preferably controls in such a manner that the difference in the supply and exhaust amounts becomes as large as possible within a range not exceeding the index value or the allowable value of the difference in the supply and exhaust amounts. For example, the supply and exhaust control unit 152 can increase the difference in the supply and exhaust amounts to the index value. Alternatively, the supply and exhaust control unit 152 can increase the difference in the supply and exhaust amounts to the allowable value. In short, by increasing the difference in the supply and exhaust amounts as much as possible within a range not exceeding the index value or the allowable value of the difference in the supply and exhaust amounts, the bubble diameter and the width of the flat film can be changed more quickly, so that the loss of the molding material can be further reduced.

[0038] Specifically, the supply and exhaust control unit 152 controls at least one of the supply amount of the air supply mechanism 128 of the air supply device 122, the opening degree of the damper 134 of the exhaust device 124, and the exhaust amount of the exhaust mechanism 132 of the exhaust device 124, and changes at least one of the supply amount Q1 and the exhaust amount Q2, thereby changing the difference in the supply and exhaust amounts.

[0039] For example, the supply and exhaust control unit 152 can also increase or decrease the exhaust amount Q2 by controlling the opening degree of the damper 134 to increase or decrease the difference in the supply and exhaust amounts (Q1 - Q2). At this time, the exhaust amount Q2 and the difference in the supply and exhaust amounts can be finely adjusted.

[0040] Also, for example, the supply and exhaust control unit 152 can, in addition to controlling the opening degree of the damper 134, also control the exhaust amount of the exhaust mechanism 132 to increase or decrease the exhaust amount Q2, thereby increasing or decreasing the difference in the supply and exhaust amounts (Q1 - Q2). At this time, the exhaust amount Q2 and the difference in the supply and exhaust amounts can be finely adjusted. Also, a larger difference in the supply and exhaust amounts can be achieved. For example, when the index value of the difference in the supply and exhaust amounts is large, the width of the flat film can be changed in a shorter time. Therefore, when the index value is small, that is, when the index value is less than a specified amount, the supply and exhaust control unit 152 can adjust the exhaust amount Q2 only through the damper 134. When the index value is large, that is, when the index value is equal to or more than the specified amount, the supply and exhaust control unit 152 can adjust the exhaust amount Q2 through the exhaust mechanism 132 in addition to the damper 134, or can adjust the exhaust amount Q2 through the exhaust mechanism 132 instead of the damper 134.

[0041] The supply / discharge control unit 152 can determine an index value of the supply / discharge volume difference at a prescribed cycle during the period of changing the width of the flat film, that is, during the period from the start of changing the width of the flat film to the end of the change, and change the supply / discharge volume difference each time a new index value is determined. This is because if the bubble diameter changes, the index value of the supply / discharge volume difference also changes.

[0042] Next, a method for determining the index value of the supply / discharge volume difference will be described. The supply / discharge control unit 152 determines the index value of the supply / discharge volume difference based on information related to the current bubble, that is, the bubble before the change if the bubble diameter is to be changed, or the bubble during the change if the bubble diameter is being changed. The information related to the bubble is information related to the ease of expansion and contraction of the bubble or information related to the amount of air in the bubble. The supply / discharge control unit 152 can determine the index value of the supply / discharge volume difference based on information related to the ease of expansion and contraction of one or more bubbles. The supply / discharge control unit 152 can determine the index value of the supply / discharge volume difference based on information related to the amount of air in one or more bubbles. The supply / discharge control unit 152 can determine the index value of the supply / discharge volume difference based on information related to the ease of expansion and contraction of one or more bubbles and information related to the amount of air in one or more bubbles.

[0043] Examples of the information related to the ease of expansion and contraction of the bubble are as follows.

[0044] · Viscosity of the bubble

[0045] · Thickness of the bubble

[0046] · Frost line height

[0047] · Melt viscosity of the molding material

[0048] · Shear rate of the molding material

[0049] · Temperature of the molding material

[0050] · Temperature at a prescribed position of the die 102

[0051] · Temperature at a prescribed position of the extruder

[0052] · Extrusion amount of the molding material from the extrusion port 102a of the die 102

[0053] · Extrusion speed from the extrusion port 102a of the die 102

[0054] · Speed of pulling the bubble, that is, the pulling speed

[0055] · Blow-up ratio

[0056] · Bubble shape (for example, the profile of the bubble diameter from the extrusion port 102a of the die 102 to the pair of pinch rolls 118)

[0057] As information related to the amount of air in the bubble, for example, the following can be cited.

[0058] · Shape of the bubble

[0059] · Height from the die 102 to the pair of pinch rollers 118

[0060] · Blow-up ratio

[0061] · Bubble shape (bubble diameter)

[0062] · Width of the flat film

[0063] · Diameter of the extrusion port 102a of the die 102

[0064] The air supply / discharge control unit 152 can determine an index value of the air supply / discharge amount difference based on information related to at least one of these bubbles.

[0065] For example, the air supply / discharge control unit 152 can use a learned learner that has undergone machine learning to determine the index value. At this time, the learner can be learned in such a way that if information related to at least one bubble is input, the index value of the air supply / discharge amount difference is output.

[0066] The above is the basic structure of the blown film forming apparatus 100.

[0067] Next, operations related to the change in the width of the flat film of the blown film forming apparatus 100 will be described. In the control device 126, if an instruction to change the width of the flat film is received, the index value of the air supply / discharge amount difference is determined based on information related to at least one bubble. The control device 126 controls the air supply / discharge amount difference so as not to exceed the determined index value or allowable value, and changes the bubble diameter and the width of the flat film.

[0068] Next, the effects that can be achieved by the present embodiment will be described. According to the present embodiment, when changing the width of the flat film during forming, an index value of the air supply / discharge amount difference at which the bubble does not fall into an unstable state is determined based on information related to the ease of expansion and contraction of the bubble or information related to the amount of air in the bubble, and the air supply / discharge amount difference is controlled so as not to exceed this index value. As a result, the bubble does not fall into an unstable state and the width of the flat film can be changed.

[0069] As described above, the present invention has been described according to the embodiment. Those skilled in the art can understand that this embodiment is an example, and various modifications can exist in the combination of these respective constituent elements or respective processing steps, and such modifications are also included in the scope of the present invention. Hereinafter, such modifications will be described.

[0070] (Modification Example 1)

[0071] Unlike the embodiment, the index value may not be the upper limit value of the supply and exhaust air volume difference. The index value may only be a value such that the smaller the bubbles are more easily stretchable or the less air is in the bubbles, and the larger the bubbles are less easily stretchable or the more air is in the bubbles. At this time, for example, the supply and exhaust control unit 152 may be such that the smaller the index value, the smaller the supply and exhaust air volume difference is reduced, and the larger the index value, the larger the supply and exhaust air volume difference is increased. The supply and exhaust control unit 152 may define a function in which the smaller the index value, the smaller the supply and exhaust air volume difference becomes, and the larger the index value, the larger the supply and exhaust air volume difference becomes, and determine the supply and exhaust air volume difference according to this function. Alternatively, the data storage unit 146 may store a table in which the index value and the supply and exhaust air volume difference are corresponding and associated, and the supply and exhaust control unit 152 refers to this table to determine the supply and exhaust air volume difference corresponding to the current index value.

[0072] As a further modification example, the index value may be a value such that the larger the bubbles are more easily stretchable or the less air is in the bubbles, and the smaller the bubbles are less easily stretchable or the more air is in the bubbles. At this time, for example, the supply and exhaust control unit 152 may be such that the larger the index value, the smaller the supply and exhaust air volume difference is reduced, and the smaller the index value, the larger the supply and exhaust air volume difference is increased. The supply and exhaust control unit 152 may define a function in which the larger the index value, the smaller the supply and exhaust air volume difference becomes, and the smaller the index value, the larger the supply and exhaust air volume difference becomes, and determine the supply and exhaust air volume difference according to this function. Alternatively, the data storage unit 146 may store a table in which the index value and the supply and exhaust air volume difference are corresponding and associated, and the supply and exhaust control unit 152 refers to this table to determine the supply and exhaust air volume difference corresponding to the current index value.

[0073] That is, the supply and exhaust control unit 152 determines the supply and exhaust air volume difference corresponding to the current index value according to the correlation between the index value and the supply and exhaust air volume difference.

[0074] (Modification Example 2)

[0075] Unlike the embodiment and the above modification examples, the supply and exhaust air volume difference may be determined without determining the index value as an intermediate value.

[0076] Specifically, when the supply and exhaust control unit 152 changes the bubble diameter, the smaller the bubbles are more easily stretchable or the less air is in the bubbles, the smaller the supply and exhaust air volume difference is reduced, and the larger the bubbles are less easily stretchable or the more air is in the bubbles, the larger the supply and exhaust air volume difference is increased. At this time, for example, a function or a table defining the relationship between the information related to the bubbles and the supply and exhaust air volume difference may be prepared, and the supply and exhaust control unit 152 determines the supply and exhaust air volume difference corresponding to the information related to the current bubbles according to this function or table.

[0077] According to an embodiment, the present invention has been described using specific terms, but the embodiment only shows one aspect of the principle and application of the present invention. In the embodiment, within the scope not departing from the idea of the present invention defined by the technical solution, many variations and configuration changes are allowed. Also, any combination of the embodiment and the variations is effective as an embodiment of the present invention. The new embodiment generated by the combination has the effects of the combined embodiment and the variations respectively.

Claims

1. A film blowing molding device, comprising: a supply and exhaust device for supplying and exhausting gas to the bubbles; and A control device controls the air supply and exhaust device, The control device controls the difference in the supply and exhaust amount of the supply and exhaust device based on information on the bubbles before or during the change of the bubble diameter when the bubble diameter is changed.

2. The film blowing molding device according to claim 1, wherein: The control device determines an index value of the supply and exhaust volume difference based on information related to the bubbles when changing the bubble diameter, and controls the supply and exhaust volume difference of the air supply and exhaust device based on the determined index value.

3. The film blowing molding device according to claim 2, wherein: The index value becomes smaller as the bubbles are more easily expanded and contracted, and becomes smaller as the amount of gas in the bubbles is less.

4. The film blowing molding device according to claim 2, wherein: The control device controls the air supply and exhaust volume difference of the air supply and exhaust device so that the air supply and exhaust volume difference becomes smaller as the index value becomes smaller when the bubble diameter is changed.

5. The film blowing molding device according to claim 2, wherein: The control device controls the difference in the supply and exhaust volume of the supply and exhaust device so as not to exceed an index value or an allowable value based on the index value when the bubble diameter is changed.

6. The film blowing molding device according to claim 2, wherein: The control device controls the air supply and exhaust volume difference of the air supply and exhaust device based on the correlation between the index value and the air supply and exhaust volume difference when changing the bubble diameter.

7. The film blowing molding device according to claim 2, wherein: The air supply and exhaust device includes a blower and a damper for adjusting the flow rate; The control device controls the air supply and exhaust volume difference only by the damper when the upper limit is less than a predetermined amount, and controls the air supply and exhaust volume difference by the blower in addition to or instead of the damper when the upper limit is greater than a predetermined amount.

8. The film blowing molding device according to claim 1, wherein: When changing the bubble diameter, the control device controls the supply and exhaust volume difference of the air supply and exhaust device based on information related to the bubbles before or during the change of the bubble diameter, so that the bubbles become smaller as they are easier to expand and contract, or the amount of gas in the bubbles becomes smaller as the amount of gas in the bubbles is less.

9. The film blowing molding device according to any one of claims 1 to 8, wherein: The information on the bubbles is information on the ease of expansion and contraction of the bubbles or information on the amount of gas in the bubbles.

10. The film blowing molding device according to claim 1, wherein: When the control device changes the bubble diameter, if before the bubble diameter is changed, the control device controls the supply and exhaust volume difference of the supply and exhaust device based on the information related to the bubbles before the change; if during the bubble diameter change, the control device controls the supply and exhaust volume difference of the supply and exhaust device based on the information related to the bubbles during the change.

11. A control device for a film blowing device having a supply and exhaust device for supplying and exhausting a bubble supply and exhaust body, wherein: When the bubble diameter is changed, the difference in the supply and exhaust amount of the air supply and exhaust device is controlled based on information on the bubbles before or during the change in the bubble diameter.

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