Inflation molding machine and control unit

Abstract

To provide inflation molding machine with enhanced product value.SOLUTION: The inflation molding machine is equipped with an air supply and exhaust system that supplies and exhausts gas to and from the bubble, and a control unit 126 that controls the air supply and exhaust system. When changing the bubble diameter, the controller 126 controls the supply and exhaust volume difference of the supply and exhaust devices based on information about the bubble before or during the bubble diameter change.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an inflation molding apparatus and a control apparatus.

Background Art

[0002] An inflation molding apparatus is known that extrudes a molten molding material from a die in a tube shape, blows air into the inside thereof to inflate it, forms a thin film (hereinafter also referred to as a bubble), folds it into a flat film, and winds up the flat film to form a roll body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is known to control the difference in the amount of air supply and exhaust to the bubble to change the bubble diameter and thus the width of the flat film (fold diameter). In this case, there may be a situation where the vibration of the bubble does not converge even after waiting for a long time, falling into an unstable state. When falling into an unstable state, it becomes necessary to take measures such as temporarily changing the molding conditions, which takes time to change the width of the flat film and increases the loss of the molding material.

[0005] The present invention has been made in such a situation, and an exemplary object of one aspect thereof is to provide an inflation molding apparatus capable of changing the fold diameter without destabilizing the bubble.

Means for Solving the Problems

[0006] In order to solve the above problems, an inflation molding apparatus according to an aspect of the present invention includes an air supply and exhaust device that supplies and exhausts gas to and from a bubble, and a control device that controls the air supply and exhaust device. When changing the bubble diameter, the control device controls the difference in the air supply and exhaust volume of the air supply and exhaust device based on information about the bubble before or during the change in the bubble diameter.

[0007] Another aspect of the present invention is a control device. This device is a control device for an inflation molding apparatus including an air supply and exhaust device that supplies and exhausts gas to and from a bubble, and when changing the bubble diameter, controls the difference in the air supply and exhaust volume of the air supply and exhaust device based on information about the bubble before or during the change in the bubble diameter.

[0008] In addition, any combination of the above components, or those obtained by mutually replacing the components and expressions of the present invention between methods, devices, systems, etc., is also effective as an aspect of the present invention.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide an inflation molding apparatus capable of changing the folding diameter without destabilizing the bubble.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. The embodiments are illustrative and not restrictive, and not all features and combinations thereof described in the embodiments are necessarily essential to the invention. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and duplicate explanations are omitted as appropriate.

[0012] Figure 1 is a diagram showing a schematic configuration of an inflation molding apparatus 100 according to an embodiment. The inflation molding apparatus 100 includes a die 102, a cooling unit 104, a pair of guide units 106, a take-up machine 108, a winder 110, a bubble state detection unit 114, an air supply and exhaust device 120, and a control device 126.

[0013] The molten molding material is extruded in a cylindrical shape from a ring-shaped extrusion port 102a formed in the die 102. Gas is supplied to the inside of the extruded cylindrical molding material at an appropriate timing, and a thin film (hereinafter also referred to as a "bubble") that swells in a cylindrical shape is formed. Although not limited thereto, the case where the gas is air will be described below.

[0014] The cooling unit 104 is disposed above the die 102. The cooling unit 104 blows cooling air onto the bubble to cool the bubble. The pair of guide units 106 are disposed above the cooling unit 104. The pair of guide units 106 guide the bubble to the take-up machine 108. The take-up machine 108 is disposed above the guide unit 106. The take-up machine 108 includes a pair of pinch rolls 118. The pair of pinch rolls 118 are driven by a motor (not shown) to rotate, and flatten and fold the guided bubble while pulling it up. Hereinafter, the flattened and folded bubble, that is, the film, is also referred to as a flat film. The winder 110 winds up the flat film to form a film roll body 111.

[0015] The bubble state detection unit 114 detects various types of information regarding the state of the bubble necessary for specifying the allowable value of the air supply and exhaust volume difference described later. Therefore, the bubble state detection unit 114 includes one or more appropriate sensors for detecting information regarding the state of the necessary bubble.

[0016] 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 bubble at each position in the circumferential direction while rotating around the bubble. The thickness data detected by the thickness detection sensor is transmitted to the control device 126.

[0017] Also for example, the bubble state detection unit 114 may include a width detection sensor disposed between the take-up machine 108 and the winding machine 110. The width detection sensor detects the flat film width (fold diameter) at a predetermined period. The width data detected by the width detection sensor is transmitted to the control device 126.

[0018] Also 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 may 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 transmitted to the control device 126.

[0019] The air supply and exhaust device 120 supplies and exhausts air to and from the bubble. The air supply and exhaust device 120 changes the flat film width by changing the difference in the air supply and exhaust amounts to the bubble, and thus changes the bubble diameter. The air supply and exhaust device 120 may also serve as an internal cooling device that supplies cold air into the bubble to cool the bubble from the inside.

[0020] The air supply and exhaust device 120 includes an air supply device 122 and an exhaust device 124.

[0021] The air supply device 122 supplies air into the bubble. The air supply device 122 includes air supply means 128 in the illustrated example although it is not particularly limited. The air supply means 128 may be an air supply blower. The air supply means 128 supplies air into the valve through the supply passage 130 in accordance with the control of the control device 126. The air supply means 128 can adjust the supply flow rate of air. Note that the air supply device 122 may further include a damper that adjusts the supply flow rate of air.

[0022] The exhaust device 124 exhausts the air in the bubble. The exhaust device 124 includes exhaust means 132 and a damper 134 in the illustrated example although it is not particularly limited. The exhaust means 132 may be an exhaust blower or an exhaust pump. The exhaust means 132 exhausts the air in the valve through the exhaust passage 136 in accordance with the control of the control device 126. The exhaust means 132 can adjust the exhaust flow rate of air. The damper 134 adjusts the exhaust flow rate of the air passing through the exhaust passage 136. The damper 134 has a higher control responsiveness than the exhaust means 132 with respect to the adjustment of the exhaust flow rate. Also, the damper 134 can adjust the exhaust flow rate more finely than the exhaust means 132. That is, the damper 134 has a higher resolution than the exhaust means 132 with respect to the adjustment of the exhaust flow rate.

[0023] The control device 126 is a device that integrally controls the inflation molding device 1.

[0024] Figure 2 is a block diagram schematically showing the functions and configuration of the control device 126. Each block shown here can be realized by elements and mechanical devices including a computer CPU in terms of hardware, and can be realized by a computer program or the like in terms of software. Here, however, functional blocks realized by their cooperation are depicted. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by a combination of hardware and software.

[0025] The control device 126 includes a communication unit 140 that executes communication processing with the bubble state detection unit 114 according to various communication protocols, a U / I unit 142 that accepts operation inputs by the user and causes various screens to be displayed on the display unit, a data processing unit 144 that executes various data processes based on the data acquired 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 may accept, for example, an instruction to change the film width.

[0026] The data processing unit 144 includes a receiving unit 150 and an air supply and exhaust control unit 152. Note that the components of the data processing unit 144 show only the components that are of interest in the present embodiment.

[0027] The receiving unit 150 receives various data regarding the state of the bubbles from the bubble state detection unit 114.

[0028] The air supply and exhaust control unit 152 controls the supply of air into the bubble by the air supply device 122 and the exhaust of air from the bubble by the exhaust device 124. In particular, the air supply and exhaust control unit 152 controls the air supply and exhaust volume difference (Q1 - Q2), which is the difference between the air supply volume Q1 into the bubble and the air exhaust volume Q2 from the bubble, to make the bubble diameter and thus the flat film width a desired size. When increasing the bubble diameter and thus the flat film width, the control device 126 temporarily increases the air supply and exhaust volume difference positively. In other words, it increases the internal pressure of the bubble. When decreasing the bubble diameter and thus the width of the flat film, the control device 126 temporarily increases the air supply and exhaust volume difference negatively. In other words, it decreases the internal pressure of the bubble.

[0029] Incidentally, when changing the bubble diameter and thus the width of the flat film during forming, the flat film during the change will be wasted. Therefore, from the perspective of reducing waste of the forming material, it might seem desirable to increase the positive or negative difference between the air supply and exhaust amounts to the bubble significantly. However, if the positive or negative difference between the air supply and exhaust amounts to the bubble is increased too much, in other words, if the bubble diameter is changed abruptly, the bubble may fall into an unstable state. An unstable state of the bubble means a state where the bubble vibrates and the vibration does not converge even after a predetermined period (for example, 15 minutes after reaching the target value) has elapsed. A state where the vibration has converged means a state where the amplitude of the vibration is below a predetermined value (for example, the target value ±2%). When the bubble falls into an unstable state, it becomes necessary to take measures such as temporarily changing the forming conditions, which instead takes time to change the width of the flat film and increases the waste of the forming material.

[0030] As a result of studying the destabilization of the bubble, the inventor of the present invention recognized that when the difference between the air supply and exhaust amounts exceeds a certain value, the bubble may fall into an unstable state, and that value varies depending on the "ease of expansion and contraction of the bubble" or the "amount of air in the bubble" at that time.

[0031] Therefore, in the present embodiment, when changing the bubble diameter and thus the width of the flat film, the air supply / exhaust control unit 152 identifies an index value of the difference between the air supply and exhaust amounts at which the bubble does not fall into an unstable state, and controls the difference between the air supply and exhaust amounts so as not to exceed that index value or an allowable value based on that index value. In the present embodiment, the index value can also be regarded as the upper limit of the difference between the air supply and exhaust amounts. The allowable value is a value obtained by multiplying the index value by a safety factor (for example, 0.9). The air supply / exhaust control unit 152 may control the difference between the air supply and exhaust amounts so as not to exceed the index value. Alternatively, the air supply / exhaust control unit 152 may control the difference between the air supply and exhaust amounts so as not to exceed the allowable value. In any case, by controlling the difference between the air supply and exhaust amounts so as not to exceed the index value or the allowable value, it is possible to change the bubble diameter and thus the width of the flat film without the bubble falling into an unstable state, and thus reduce the waste of the forming material.

[0032] Note that the easier it is for the bubble to expand and contract, the more rapidly the bubble diameter changes, and thus the bubble is more likely to enter an unstable state. Also, even when the supply / discharge air volume difference is the same, the smaller the air volume in the bubble, the greater the rate of change, and the more rapidly the bubble diameter changes, so the bubble is more likely to enter an unstable state. Therefore, the index value of the supply / discharge air volume difference decreases as the bubble is more likely to expand and contract, and increases as the bubble is less likely to expand and contract. Also, the index value of the supply / discharge air volume difference decreases as the air volume in the bubble is smaller, and increases as the air volume in the bubble is larger.

[0033] The supply / discharge control unit 152 preferably controls so that the supply / discharge air volume difference becomes as large as possible within a range not exceeding the index value or allowable value of the supply / discharge air volume difference. For example, the supply / discharge control unit 152 may increase the supply / discharge air volume difference up to the index value. Alternatively, the supply / discharge control unit 152 may increase the supply / discharge air volume difference up to the allowable value. In any case, by making the supply / discharge air volume difference as large as possible within a range not exceeding the index value or allowable value of the supply / discharge air volume difference, the bubble diameter and thus the flat film width can be changed more quickly, and the loss of the molding material can be further reduced.

[0034] Specifically, the supply / discharge control unit 152 controls at least one of the supply amount of the air supply means 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 means 132 of the exhaust device 124, and changes the supply / discharge air volume difference by changing at least one of the supply air volume Q1 and the exhaust air volume Q2.

[0035] For example, the supply / discharge control unit 152 may increase or decrease the supply / discharge air volume difference (Q1 - Q2) by controlling the opening degree of the damper 134 to increase or decrease the exhaust air volume Q2. In this case, the exhaust air volume Q2 and thus the supply / discharge air volume difference can be finely adjusted.

[0036] For example, in addition to controlling the opening degree of the damper 134, the intake and exhaust control unit 152 may control the exhaust amount of the exhaust means 132 to increase or decrease the exhaust amount Q2, thereby increasing or decreasing the intake and exhaust amount difference (Q1 - Q2). In this case, the exhaust amount Q2, and thus the intake and exhaust amount difference, can be finely adjusted. Also, a larger intake and exhaust amount difference can be realized, and for example, when the index value of the intake and exhaust amount difference is large, it becomes possible to change the flat film width in a shorter time. Therefore, when the index value is small, that is, when the index value is less than a predetermined amount, the intake and exhaust control unit 152 may adjust the exhaust amount Q2 only by the damper 134. When the index value is large, that is, when the index value is equal to or greater than a predetermined amount, the intake and exhaust control unit 152 may adjust the exhaust amount Q2 by the exhaust means 132 in addition to the damper 134, or by the exhaust means 132 instead of the damper 134.

[0037] While changing the flat film width, that is, from the start of the change in the flat film width until the change is completed, the intake and exhaust control unit 152 may specify the index value of the intake and exhaust amount difference at a predetermined cycle, and change the intake and exhaust amount difference each time a new index value is specified. This is because the index value of the intake and exhaust amount difference changes as the bubble diameter changes.

[0038] Subsequently, a method for specifying the index value of the intake and exhaust amount difference will be described. The intake and exhaust control unit 152 specifies the index value of the intake and exhaust amount difference based on information regarding the current bubble, that is, the bubble before the change in the bubble diameter if it is before the change, or the bubble during the change in the bubble diameter if it is during the change. Information regarding the bubble is information regarding the ease of expansion and contraction of the bubble or information regarding the amount of air in the bubble. The intake and exhaust control unit 152 may specify the index value of the intake and exhaust amount difference based on information regarding the ease of expansion and contraction of one or more bubbles. The intake and exhaust control unit 152 may specify the index value of the intake and exhaust amount difference based on information regarding the amount of air in one or more bubbles. The intake and exhaust control unit 152 may specify the index value of the intake and exhaust amount difference based on information regarding the ease of expansion and contraction of one or more bubbles and information regarding the amount of air in one or more bubbles.

[0039] Examples of information regarding the ease of expansion and contraction of the bubble include the following. · Viscosity of the bubble · Thickness of the bubble · Frost line height · Melt viscosity of the molding material · Shear rate of the molding material · Temperature of the molding material · Temperature at a predetermined position of the die 102 · Temperature at a predetermined position of the extruder · Extrusion amount of the molding material from the die outlet 102a of the die 102 · Extrusion speed from the die outlet 102a of the die 102 · Take-up speed, which is the speed at which the bubble is taken up · Blow ratio · Bubble shape (for example, the profile of the bubble diameter from the die outlet 102a of the die 102 to the pair of pinch rolls 118)

[0040] Examples of information regarding the amount of air in the bubble include the following. · Shape of the bubble · Height from the die 102 to the pair of pinch rolls 118 · Blow ratio · Bubble shape (bubble diameter) · Width of the flat film · Diameter of the die outlet 102a of the die 102

[0041] The air supply and exhaust control unit 152 may specify an index value of the air supply and exhaust volume difference based on information regarding at least one of these bubbles.

[0042] For example, the air supply and exhaust control unit 152 may specify the index value using a trained learning device that has performed machine learning. In this case, the learning device may be trained to output an index value of the air supply and exhaust volume difference when input with information regarding at least one bubble.

[0043] The above is the basic configuration of the inflation molding apparatus 100.

[0044] Next, the operation regarding the change in the width of the flat film of the inflation molding apparatus 100 will be described. When the control device 126 receives an instruction to change the width of the flat film, it specifies an index value of the air supply / discharge difference based on information regarding at least one bubble. The control device 126 controls the air supply / discharge difference so as not to exceed the specified index value or allowable value, and changes the bubble diameter and thus the flat film width.

[0045] Next, the effects achieved by the present embodiment will be described. According to the present embodiment, when changing the width of the flat film during molding, based on information regarding the ease of expansion and contraction of the bubble or information regarding the amount of air in the bubble, an index value of the air supply / discharge difference at which the bubble does not enter an unstable state is specified, and the air supply / discharge difference is controlled so as not to exceed that index value. As a result, the width of the flat film can be changed without the bubble entering an unstable state.

[0046] As described above, the present invention has been described based on the embodiments. It is to be understood by those skilled in the art that these embodiments are illustrative, and that various modifications are possible in the combination of each of these constituent elements and each processing process, and that such modifications are also within the scope of the present invention. Hereinafter, such modifications will be described.

[0047] (Modification 1) Unlike the embodiment, the index value may not be the upper limit value of the air supply / discharge difference. The index value may simply be a value that is smaller as the bubble is more easily expandable or contractible or as the amount of air in the bubble is smaller, and larger as the bubble is less easily expandable or contractible or as the amount of air in the bubble is larger. In this case, for example, the air supply / discharge control unit 152 may make the air supply / discharge difference smaller as the index value is smaller, and make the air supply / discharge difference larger as the index value is larger. The air supply / discharge control unit 152 may define a function in which the air supply / discharge difference becomes smaller as the index value is smaller and becomes larger as the index value is larger, and determine the air supply / discharge difference based on that function. Alternatively, the data storage unit 146 may store a table associating the index value with the air supply / discharge difference, and the air supply / discharge control unit 152 may refer to that table and determine the air supply / discharge difference corresponding to the index value at that time.

[0048] As a further modification, the index value may be larger as the bubble is more likely to expand and contract or the air amount in the bubble is smaller, and smaller as the bubble is less likely to expand and contract or the air amount in the bubble is larger. In this case, for example, the air supply / discharge control unit 152 may make the air supply / discharge amount difference smaller as the index value is larger, and make the air supply / discharge amount difference larger as the index value is smaller. The air supply / discharge control unit 152 may define a function in which the air supply / discharge amount difference becomes smaller as the index value is larger and becomes larger as the index value is smaller, and determine the air supply / discharge amount difference based on the function. Alternatively, the data storage unit 146 may store a table associating the index value with the air supply / discharge amount difference, and the air supply / discharge control unit 152 may refer to the table and determine the air supply / discharge amount difference corresponding to the index value at that time.

[0049] That is, the air supply / discharge control unit 152 determines the air supply / discharge amount difference corresponding to the index value at that time based on the correlation between the index value and the air supply / discharge amount difference.

[0050] (Modification 2) Different from the embodiments and the above-described modifications, the air supply / discharge amount difference may be determined without specifying the index value as the intermediate value.

[0051] Specifically, when changing the bubble diameter, the air supply / discharge control unit 152 makes the air supply / discharge amount difference smaller as the bubble is more likely to expand and contract or the air amount in the bubble is smaller, and makes the air supply / discharge amount difference larger as the bubble is less likely to expand and contract or the air amount in the bubble is larger. In this case, for example, a function or a table defining the relationship between the information about the bubble and the air supply / discharge amount difference is prepared, and the air supply / discharge control unit 152 may determine the air supply / discharge amount difference corresponding to the information about the bubble at that time based on the function or the table.

[0052] Based on the embodiments, the present invention has been described using specific terms. However, the embodiments merely show one aspect of the principle and application of the present invention. In the embodiments, many modifications and arrangement changes are recognized as long as they do not depart from the idea of the present invention defined in the claims. Also, any combination of the embodiments and the modification examples is also useful as an embodiment of the present invention. The new embodiment resulting from the combination has the effects of each of the combined embodiments and modification examples combined.

Explanation of Reference Numerals

[0053] 100 Inflation molding apparatus, 102 Die, 120 Air supply and exhaust device, 122 Air supply device, 124 Exhaust device, 126 Control device, 132 Exhaust means, 134 Damper.

Claims

1. An air supply and exhaust device for supplying and exhausting gas to and from a bubble, and A control device for controlling the air supply and exhaust device, wherein When changing the bubble diameter, the control device is an inflation molding device that controls the difference in air supply and exhaust volume of the air supply and exhaust device based on information about the bubble before or during the change in bubble diameter.

2. The inflation molding device according to claim 1, wherein when changing the bubble diameter, the control device specifies an index value of the difference in air supply and exhaust volume based on information about the bubble, and controls the difference in air supply and exhaust volume of the air supply and exhaust device based on the specified index value.

3. The inflation molding device according to claim 2, wherein the index value becomes smaller as the bubble is more easily expandable and contractible, and becomes smaller as the amount of gas in the bubble is smaller.

4. The inflation molding device according to claim 2, wherein when changing the bubble diameter, the control device controls the difference in air supply and exhaust volume of the air supply and exhaust device so that the difference becomes smaller as the index value becomes smaller.

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

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

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

8. The inflation molding device according to claim 1, wherein when changing the bubble diameter, the control device controls the difference in air supply and exhaust volume of the air supply and exhaust device based on information about the bubble before or during the change in bubble diameter so that the difference becomes smaller as the bubble is more easily expandable and contractible or as the amount of gas in the bubble is smaller.

9. The inflation molding device according to any one of claims 1 to 8, wherein the information about the bubble is information about the ease of expansion and contraction of the bubble or information about the amount of gas in the bubble.

10. When changing the bubble diameter, the control device controls the difference in the supply and exhaust air volume of the supply and exhaust device based on information about the bubbles before the change if it is before the change of the bubble diameter, and controls the difference in the supply and exhaust air volume of the supply and exhaust device based on information about the bubbles during the change if it is during the change of the bubble diameter. The inflation molding apparatus according to claim 1.

11. A control device for an inflation molding apparatus including a supply and exhaust device that supplies and exhausts gas to and from a bubble, the control device When changing the bubble diameter, a control device that controls the difference in the supply and exhaust air volume of the supply and exhaust device based on information about the bubbles before or during the change of the bubble diameter.

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