Inflation molding equipment

Abstract

To provide an inflation molding apparatus that does not require replacement of a sizing ring in changing an outer diameter of a bubble.SOLUTION: An inflation molding apparatus is a downward water-cooling inflation molding apparatus. The inflation molding apparatus has a sizing ring 28 that defines an outer diameter of a bubble. The sizing ring 28 includes a variable inner diameter mechanism 32 that changes an inner diameter of the sizing ring 28.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an inflation molding apparatus. [Background technology]

[0002] There is a known inflation molding apparatus that extrudes molten resin from a die into a tube shape, blows air into the inside of the tube to inflate it, and forms a thin film. There are two types of inflation molding apparatus: an upward type that extrudes molten resin upward, and a downward type that extrudes molten resin downward. When the molten resin is cooled with water, as in Patent Document 1, the downward type is mainly used. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-231266 A Summary of the Invention [Problem to be solved by the invention]

[0004] Downward inflation molding apparatuses generally include a sizing ring for determining the outer diameter of the bubble. In conventional downward inflation molding apparatuses, when changing the outer diameter of the bubble, it is necessary to replace the sizing ring with one having a different inner diameter of the insertion hole through which the bubble passes. Replacing the sizing ring is a complicated task and places a heavy burden on the worker. In addition, the replacement takes time, during which the film production is stopped. In addition, in order to replace the sizing ring, it is necessary to stop molding, i.e., to stop the flow of resin, and when molding is resumed, i.e., when the resin flow is started again, resin loss is inevitably generated.

[0005] The present invention has been made in view of the above circumstances, and one exemplary purpose of an embodiment of the present invention is to provide an inflation molding apparatus that does not require replacement of a sizing ring when changing the outer diameter of a bubble. [Means for solving the problem]

[0006] In order to solve the above problems, an inflation molding apparatus according to one embodiment of the present invention is a downward water-cooled inflation molding apparatus, and includes a sizing ring that determines the outer diameter of a bubble. The sizing ring includes an inner diameter varying mechanism that changes the inner diameter of the sizing ring.

[0007] Any combination of the above components, or mutual substitution of the components or expressions of the present invention between methods, devices, systems, etc. are also valid aspects of the present invention. Effect of the Invention

[0008] According to the present invention, it is not necessary to replace the sizing ring when changing the outer diameter of the valve. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an inflation molding apparatus. [Diagram 2] 2 is a cross-sectional view showing a second cooling device and its periphery in FIG. 1. [Diagram 3] 3(a) and (b) are perspective views showing the sizing ring of FIG. 2. FIG. [Figure 4] FIG. 4 is a perspective view showing one of the blades in FIGS. [Diagram 5] 5(a) to (c) are diagrams illustrating the operation of the sizing ring. [Figure 6] 6(a) and (b) are perspective views showing sizing rings according to modified examples. [Figure 7] FIG. 7 is a side view of the sizing ring of FIGS. 6(a) and (b). [Figure 8] 8(a) to (c) are diagrams illustrating the operation of the sizing ring of FIGS. 6(a) and (b). [Figure 9]9(a) and (b) show a sizing ring and its surroundings according to yet another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted as appropriate.

[0011] 1 is a diagram showing a schematic configuration of an inflation molding apparatus 1 according to an embodiment. The inflation molding apparatus 1 includes a die 10, a first cooling device 12, a second cooling device 14, a pair of stabilizing plates 16, and a pinch roll 18. The inflation molding apparatus 1 is a so-called downward type inflation molding apparatus in which resin is extruded downward from the die 10.

[0012] Molten resin is supplied to the die 10 from an extruder (not shown). The supplied molten resin is extruded from a ring-shaped discharge port 10a formed in the die 10. Air is appropriately ejected from air ejection ports 10b formed inside the discharge port 10a into the extruded molten resin. This forms a bubble 24, which is a tubular thin resin film.

[0013] The first cooling device 12 is disposed below the die 10. The first cooling device 12 blows cooling air onto the bubble 24 to cool the bubble 24.

[0014] The second cooling device 14 is disposed below the first cooling device 12. The second cooling device 14 cools the bubbles 24 by directly contacting the bubbles 24 with cooling water. In addition, the second cooling device 14 determines the outer diameter of the bubbles 24, as will be described in detail later.

[0015] Upon being cooled in the first cooling device 12 and the second cooling device 14, the bubbles 24 solidify.

[0016] The pair of stabilizer plates 16 are disposed below the second cooling device 14 and guide the bubble 24 between the pair of pinch rolls 18. The pair of pinch rolls 18 are disposed below the stabilizer plates 16. The pair of pinch rolls 18 pull down the guided bubble 24 and fold it flat. The winder 20 winds up the folded resin film to form a film roll body 22.

[0017] 2 is a cross-sectional view showing the second cooling device 14. The second cooling device 14 includes a water tank 26, a sizing ring 28 and a first cylindrical member 29 provided in the water tank 26, a rotation mechanism 30, and a second cylindrical member 31 provided below the water tank 26.

[0018] The water tank 26 has, although not limited to, a substantially circular shape in a plan view, an open top, and an insertion hole 26b through which the bubble 24 passes is formed in the bottom 26a.

[0019] The first cylindrical member 29 is provided so that its central axis extends in the vertical direction. The lower end of the first cylindrical member 29 is placed on the bottom 26a of the water tank 26 and is spigot-fitted to the bottom 26a. The sizing ring 28 is placed on the upper end of the first cylindrical member 29. In other words, the sizing ring 28 is supported by the first cylindrical member 29. The upper end of the first cylindrical member 29 is spigot-fitted to the sizing ring 28, specifically, to its second holding member 54 (described later).

[0020] The second cylindrical member 31 is fixed to the lower surface of the bottom portion 26a of the water tub 26. The second cylindrical member 31 has the same inner diameter as the insertion hole 26b of the water tub 26, and surrounds the valve 24.

[0021] Cooling water is supplied to the water tank 26 from a supply port 26c formed in the bottom 26a. An overflow pipe 34 extending above the sizing ring 28 is attached to the bottom 26a of the water tank 26. This keeps the level WH of the cooling water at a predetermined level above the sizing ring 28. The cooling water cools the bubble 24 as it flows down between the outer periphery of the bubble 24 and the insertion hole 28a of the sizing ring 28.

[0022] A plurality of (e.g., four) plates 27 are fixed to the outer peripheral surface 26d of the water tank 26. A first bolt 70 is screwed vertically downward into each of the plurality of plates 27. The first bolts 70 are provided, for example, at equal intervals in the circumferential direction. The first bolts 70 penetrate the plates 27, and the tips of the first bolts 70 each abut against the upper surface 60a of the mounting table 60. The water tank 26 is supported on the mounting table 60 via the plurality of first bolts 70. The first bolts 70 and the plates 27 form a ball screw mechanism, and when the first bolts 70 are turned, the plates 27 and therefore the water tank 26 move up and down. In other words, the height of the water tank 26 is adjusted.

[0023] A plurality of (e.g., four) support members 62 are fixed to the upper surface 60a of the mounting table 60. A second bolt 72 is screwed horizontally into each of the plurality of support members 62 toward the central axis of the sizing ring 28. The second bolts 72 are provided, for example, at equal intervals in the circumferential direction. The second bolts 72 penetrate the support members 62, and the tips of the second bolts 72 each abut against the outer circumferential surface 26d of the water tank 26. The plurality of second bolts 72 position the water tank 26 in the horizontal direction. For example, the water tank 26 is positioned in the horizontal direction so that the central axis of the sizing ring 28 coincides with the central axis of the discharge port 10a of the die 10.

[0024] The sizing ring 28 is a member that defines the outer diameter of the bubble 24 by the circumferential surface 28b of the insertion hole 28a. In detail, the bubble 24 passes through the sizing ring 28 while contacting the circumferential surface 28b of the insertion hole 28a, so that the outer diameter of the bubble 24 is defined to a size corresponding to the inner diameter of the insertion hole 28a (i.e., the same as or slightly smaller than the inner diameter).

[0025] The sizing ring 28 of this embodiment is configured so that the inner diameter of the insertion hole 28a can be changed. As a result, when the outer diameter of the bubble 24 is changed, the inner diameter of the insertion hole 28a of the sizing ring 28 can be changed, and it is not necessary to replace the sizing ring as in the conventional inflation molding apparatus. Note that FIG. 2 shows the state in which the inner diameter of the sizing ring 28 is at its maximum.

[0026] 3(a) and (b) are perspective views showing the sizing ring 28. Fig. 3(a) shows the sizing ring 28 in a state where the inner diameter of the insertion hole 28a is maximized, and Fig. 3(b) shows the sizing ring 28 in a state where the inner diameter of the insertion hole 28a is minimized. Fig. 4 is a perspective view showing one of the blades 50 of the sizing ring 28.

[0027] The sizing ring 28 includes a plurality of (32 in the illustrated example) blades (inner diameter defining members) 50 arranged in the circumferential direction, and a first holding member 52 and a second holding member 54 that hold the plurality of blades 50. In this example, the entire sizing ring 28, i.e., the plurality of blades 50, the first holding member 52, and the second holding member 54, configure the inner diameter varying mechanism 32 that changes the inner diameter of the insertion hole 28a.

[0028] The first holding member 52 is a thin-walled annular member. The first holding member 52 has slits 52a formed therein at equal intervals in the circumferential direction, the same number as the number of blades 50. The slits 52a extend linearly. In a plan view, the slits 52a are inclined with respect to the radial direction so that the radially outer side is positioned to one side in the circumferential direction (the front side in the clockwise direction in the illustrated example).

[0029] The second holding member 54 is a member having the same shape and size as the first holding member 52. That is, the second holding member 54 is a thin-walled annular member. The second holding member 54 has slits 54a, the same number as the number of blades 50, formed at equal intervals in the circumferential direction. The slits 54a extend linearly. In plan view, the slits 54a are inclined with respect to the radial direction so that the radially outer side is located on the other circumferential side (the clockwise rear side in the illustrated example). That is, the slits 54a are inclined in the opposite direction to the slits 52a in plan view.

[0030] The blades 50 are members having a substantially triangular prism shape, and are arranged so that the side surfaces 50a of adjacent blades 50 contact each other. In particular, the blades 50 are arranged so as to overlap at least adjacent blades 50 in the radial direction. The insertion hole 28a of the sizing ring 28 is defined by the multiple blades 50, and the circumferential surface 28b of the insertion hole 28a is formed by the side surfaces 50a of the multiple blades 50. The height of the circumferential surface 28b of the insertion hole 28a is determined by the height of the blades 50. The height of the circumferential surface 28b may be formed to a height necessary to define the outer diameter of the bubble 24 based on simulation, experiment, or knowledge.

[0031] The blade 50 includes an inner upper surface 50b and an outer upper surface 50c located above the inner upper surface 50b. An upper protrusion 50d protruding upward is provided on the outer periphery of the outer upper surface 50c. A lower protrusion 50f protruding downward is provided on the outer periphery of the lower surface 50e of the blade 50. The upper protrusion 50d of the blade 50 engages with a slit 52a of the first holding member 52, and the lower protrusion 50f engages with a slit 54a of the second holding member 54.

[0032] 5(a) to (c) are diagrams for explaining the operation of the sizing ring 28. In FIG. 5(a) to (c), only two blades 50 are shown for ease of viewing. Also, the second holding member 54 is omitted. FIG. 5(a) shows a state in which the inner diameter of the insertion hole 28a is maximum, and FIG. 5(c) shows a state in which the inner diameter of the insertion hole 28a is minimum. When the first holding member 52 is rotated clockwise relative to the second holding member 54, the state of the sizing ring 28 changes from FIG. 5(a) to FIG. 5(b) to FIG. 5(c). Conversely, when the first holding member 52 is rotated counterclockwise relative to the second holding member 54, the state of the sizing ring 28 changes from FIG. 5(c) to FIG. 5(b) to FIG. 5(a).

[0033] As described above, the slits 52a are inclined with respect to the radial direction so that the radially outer side is positioned closer to the front side in the clockwise direction, and conversely, the radially inner side is positioned closer to the rear side in the clockwise direction.

[0034] Therefore, when the first holding member 52 is rotated clockwise relative to the second holding member 54, the upper protrusions 50d, and therefore the blades 50, move radially inward along the slits 52a and slits 54a relative to the first holding member 52 and the second holding member 54. The more each blade 50 moves radially inward, the smaller the inner diameter of the insertion hole 28a formed by the side surface 50a of each blade 50 becomes.

[0035] Conversely, when the first holding member 52 is rotated counterclockwise relative to the second holding member 54, the upper protrusions 50d, and therefore the blades 50, move radially outward along the slits 52a and slits 54a relative to the first holding member 52 and the second holding member 54. The more each blade 50 moves radially outward, the larger the inner diameter of the insertion hole 28a formed by the side surface 50a of each blade 50 becomes.

[0036] In other words, by rotating first holding member 52 clockwise or counterclockwise relative to second holding member 54, the relative position of each of the multiple blades 50 to the other blades 50 changes, and the inner diameter of insertion hole 28a changes.

[0037] Here, the case where the first holding member 52 is rotated relative to the second holding member 54 has been described, but the present invention is not limited to this. The second holding member 54 may be rotated relative to the first holding member 52.

[0038] When the insertion hole 28a, the size of which is variable, is formed by a plurality of blades 50, the insertion hole 28a inevitably becomes non-circular. In this example, the insertion hole 28a of the sizing ring 28 is polygonal. Therefore, the inner diameter of the insertion hole 28a may be the diameter of the largest circle that fits into the insertion hole 28a, or if the insertion hole 28a is polygonal, it may be the diameter of the inscribed circle thereof.

[0039] Return to FIG. 2. As described above, the insertion hole 28a of the sizing ring 28 is not a perfect circle. Therefore, the gap between the insertion hole 28a and the bubble 24 is large or small in some parts in the circumferential direction. That is, the amount of water flowing is large or small in some parts in the circumferential direction. The area where the amount of water flowing is large cools faster than the area where the amount of water flowing is small, that is, the time until solidification is short. The area where the amount of water flowing is small cools slower than the area where the amount of water flowing is large, that is, the time until solidification is long. The bubble 24 is stretched and thinned by being pulled by the pinch roll 18, but the area where the time until solidification is short does not stretch as much as the area where the time until solidification is long, and the area where the time until solidification is long stretches more than the area where the time until solidification is short. As a result, the thickness of the bubble 24 becomes non-uniform in the circumferential direction.

[0040] Although the thickness of the bubbles 24 is within the allowable range, if the thickness is uneven in the circumferential direction and thick or thin portions are piled up when forming the film roll body 22, unevenness will occur on the outer periphery of the film roll body. The unevenness will cause distortion of the film.

[0041] Therefore, in the present embodiment, the multiple blades 50 that define the insertion hole 28a of the sizing ring 28 are rotated around the bubble 24 while maintaining their relative positions relative to each other. This makes it possible to vary the locations of large and small gaps between the insertion hole 28a and the bubble 24 in the circumferential direction without changing the size of the inner diameter of the insertion hole 28a. As a result, the thick and thin locations of the bubble 24 vary in the circumferential direction, making it possible to prevent thick portions or thin portions from piling up on each other when the film roll body 22 is formed.

[0042] The rotation mechanism 30 is a mechanism for rotating the plurality of blades 50 while maintaining their relative positions relative to one another. Although not particularly limited, the rotation mechanism 30 of the present embodiment rotates the plurality of blades 50 by rotating the sizing ring 28. The rotation mechanism 30 rotates the sizing ring 28 once every 20 to 30 minutes, for example.

[0043] In this example, the rotation mechanism 30 rotates the water tank 26, the sizing ring 28, and the plurality of blades 50. In detail, the rotation mechanism 30 includes a drive device 36 and a transmission mechanism 38.

[0044] The driving device 36 is, for example, a motor or a gear motor, and outputs a rotational force. The transmission mechanism 38 is a mechanism for transmitting the rotational force of the driving device 36 to the water tub 26, and includes an external gear 40 and a rotary bearing 42.

[0045] The external gear 40 is fitted to the output shaft 36a of the drive unit 36. The slewing bearing 42 is disposed so as to surround the valve 24. In this example, the central axes of the slewing bearing 42, the sizing ring 28 and the water tank 26 are substantially aligned.

[0046] The slewing bearing 42 includes an inner ring 44 and an outer ring 46. The inner ring 44 is fixed to a frame (not shown). The outer ring 46 is fixed to the water tank 26. In this example, the outer ring 46 is fixed to a mounting table 60 on which the water tank 26 is placed, that is, indirectly fixed to the water tank 26, but it may also be fixed directly to the water tank 26. External teeth 46a that mesh with the external gear 40 are formed on the outer periphery of the outer ring 46.

[0047] When the external gear 40 rotates in accordance with the rotation of the output shaft 36a, the outer ring 46 rotates. As described above, the outer ring 46 is fixed to the water tank 26. In addition, the sizing ring 28 is fixed to the water tank 26. Therefore, when the outer ring 46 rotates, the sizing ring 28 rotates.

[0048] The rotation mechanism 30 may preferably rotate (i.e., reciprocate) the water tank 26 within a predetermined angular range (e.g., a predetermined angular range of 360° or less), thereby preventing twisting of a hose (not shown) connected to the supply port 26c.

[0049] In the present embodiment described above, it is possible to change the inner diameter of the insertion hole 28a of the sizing ring 28. As a result, when the outer diameter of the bubble 24 is changed, it is only necessary to change the inner diameter of the insertion hole 28a of the sizing ring 28, and it is not necessary to replace the sizing ring as in the conventional inflation molding apparatus.

[0050] In the present embodiment, the blades 50 that define the inner diameter of the insertion hole 28a of the sizing ring 28 are rotated around the bubble 24 while maintaining their relative positions. This allows the locations of large and small gaps to be varied in the circumferential direction without changing the size of the inner diameter of the insertion hole 28a. As a result, the thick and thin locations of the bubble 24 vary in the circumferential direction, making it possible to prevent thick or thin portions from piling up on each other when the film roll body 22 is formed.

[0051] Furthermore, in this embodiment, the sizing ring 28 and therefore the multiple blades 50 are rotated together with the water tank 26. This makes it possible to prevent unevenness from occurring on the outer periphery of the film roll body 22. Furthermore, because the water tank 26 is rotated together with the sizing ring 28, it is not necessary to place the components of the rotation mechanism 30 inside the water tank 26. If the components of the rotation mechanism 30 were placed inside the water tank 26, the water in the water tank 26 would sway, which would cause uneven thickness in the bubble 24, but this can be avoided.

[0052] The present invention has been described above based on the embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each processing step, and that such modifications are also within the scope of the present invention. Modifications will be described below.

[0053] (Variation 1) 6(a) and (b) are perspective views showing a sizing ring 128 according to a modified example. Fig. 6(a) shows the sizing ring 128 in a state where the inner diameter of the insertion hole 128a is maximized, and Fig. 6(b) shows the sizing ring 128 in a state where the inner diameter of the insertion hole 128a is minimized. Fig. 7 is a side view of the sizing ring 128. For ease of viewing, Fig. 7 shows only one blade 150.

[0054] Sizing ring 128 includes a plurality of blades (inner diameter defining members) 150 (32 in the illustrated example), and a first holding member 152 and a second holding member 154 that hold the plurality of blades 150. In this example, the entire sizing ring 128, i.e., the plurality of blades 150, the first holding member 152, and the second holding member 154, configures an inner diameter varying mechanism 132 that changes the inner diameter of insertion hole 128a.

[0055] The first holding member 152 is a thin, annular member. The second holding member 154 is a member having the same shape and size as the first holding member 152. In other words, the second holding member 154 is a thin, annular member.

[0056] Each of the multiple blades 150 includes a substantially arc-shaped main body portion 156 and a linear connecting portion 158. One end 156a of the main body portion 156 is rotatably connected to the first holding member 152, and the other end 156b is rotatably connected to one end 158a of the connecting portion 158. The other end 158b of the connecting portion 158 is rotatably connected to the second holding member 154. The one end 156a of the main body portion 156 and the other end 158b of the connecting portion 158 are located on roughly opposite sides with the center of the holding members 152, 154 in between.

[0057] Each of the multiple blades 150 is arranged so as to overlap at least one of the other blades 150 in the axial direction. Ends 156a of main body portions 156 of the multiple blades 150 are connected to the first holding member 152 so as to be aligned in the circumferential direction. Similarly, ends 158b of connecting portions 158 of the multiple blades 150 are connected to the second holding member 154 so as to be aligned in the circumferential direction.

[0058] 8(a) to 8(c) are diagrams for explaining the operation of the sizing ring 128. In FIG. 8(a) to 8(c), only two blades 150 are shown for ease of viewing. FIG. 8(a) shows a state in which the inner diameter of the insertion hole 128a is at its maximum, and FIG. 8(c) shows a state in which the inner diameter of the insertion hole 128a is at its minimum. When the first holding member 152 is rotated clockwise relative to the second holding member 154, the state of the sizing ring 128 changes from FIG. 8(a) to FIG. 8(b) to FIG. 8(c). Conversely, when the first holding member 152 is rotated counterclockwise relative to the second holding member 154, the state of the sizing ring 128 changes from FIG. 8(c) to FIG. 8(b) to FIG. 8(a).

[0059] As described above, one end of the blade 150 (i.e., end 156a of the main body portion 156) is connected to the first retaining member 152, and the other end (i.e., end 158b of the connecting portion 158) is connected to the second retaining member 154.

[0060] Therefore, when the first holding member 152 is rotated clockwise relative to the second holding member 154, the connecting portion of the end 156a of the main body 156 with the first holding member 152 moves clockwise, while the connecting portion of the end 158b of the connecting portion 158 with the second holding member 154 does not move. This changes the relative position of the main body 156 and the connecting portion 158. Then, the blade 150 rotates clockwise about the other end (i.e., the end 158b of the connecting portion 158). As a result, the blade 150 moves radially inward. The more each blade 150 moves radially inward, the smaller the inner diameter of the insertion hole 128a of the sizing ring 128 formed by the side surface 150a of each blade 150 becomes.

[0061] On the other hand, when the first holding member 152 is rotated counterclockwise relative to the second holding member 154, the connecting portion of the end 156a of the main body 156 with the first holding member 152 moves counterclockwise, while the connecting portion of the end 158b of the connecting portion 158 with the second holding member 154 does not move. This changes the relative position of the main body 156 and the connecting portion 158. Then, the blade 150 rotates counterclockwise about the other end (i.e., the end 158b of the connecting portion 158). As a result, the blade 150 moves radially outward. The more the blade 150 moves radially outward, the larger the inner diameter of the insertion hole 128a of the sizing ring 128 formed by the side surfaces 150a of the multiple blades 150 becomes.

[0062] As with the sizing ring 28 of the embodiment, by rotating the first retaining member 152 clockwise or counterclockwise relative to the second retaining member 154, the relative position of each of the multiple blades 150 to the other blades 150 changes, and the inner diameter of the insertion hole 128a changes.

[0063] Here, the case where the first holding member 152 is rotated relative to the second holding member 154 has been described, but the present invention is not limited to this, and the second holding member 154 may be rotated relative to the first holding member 152.

[0064] The variable-sized insertion hole 128a formed by the plurality of blades 150 is non-circular, similar to the insertion hole 128 of the embodiment. Therefore, similar to the embodiment, the plurality of blades 150 may be rotated by a rotation mechanism while maintaining their relative positions. For example, the sizing ring 128 and the plurality of blades 150 may be rotated together with the water tank 26.

[0065] The inflation molding apparatus 1 may include a plurality of sizing rings 128 arranged concentrically in the vertical direction. By adjusting the number of sizing rings 128, the total height of the circumferential surface of the insertion hole 28a can be adjusted.

[0066] According to this modification, it is possible to achieve the same effects as those of the embodiment.

[0067] (Variation 2) In the embodiment and the above-mentioned modified example, the case where the rotation mechanism 30 rotates the sizing ring together with the water tank 26 has been described, but the rotation mechanism 30 may directly rotate the sizing ring.

[0068] A case where the sizing ring 128 of the first modified example is directly rotated will be described. FIGS. 9(a) and (b) are diagrams showing a sizing ring 128 and its periphery according to yet another modified example. In this example, for ease of viewing, only four blades 150 are shown. The sizing ring 128 of FIGS. 9(a) and (b) corresponds to the sizing ring 128 of FIGS. 6(a) and (b). The sizing ring 128 of this modified example has external teeth 152a and 154a formed on the outer circumferential surfaces of the first holding member 152 and the second holding member 154. The rotation mechanism 30 includes a driving device (not shown) and an external gear 40 fitted to the rotating shaft of the driving device. The external teeth 152a and 154a of the holding members 152 and 154 mesh with the external gear 40. As a result, when the external gear 40 rotates with the rotation of the output shaft of the driving device, the sizing ring 128 rotates together with the holding members 152 and 154.

[0069] The sizing ring 28 of the embodiment may be directly rotated. In this case, for example, external teeth may be formed on the outer circumferential surfaces of the first holding member 52 and the second holding member 54, and the holding members 52, 54 may be rotated by meshing with the external gear 40.

[0070] When the inner diameter of the sizing ring is changed, the external teeth of the first and second holding members are disengaged from the external gear 40 fitted to the rotating shaft of the drive device 36 of the rotation mechanism 30. In other words, they are not meshed. When the entire sizing ring is rotated, the external teeth of the first and second holding members are engaged with the external gear fitted to the rotating shaft of the drive device 36 of the rotation mechanism 30. In other words, they are meshed. In this case, the second cooling device 14 may be provided with an engagement state switching mechanism that engages and disengages the external teeth of the first and second holding members with the external gear fitted to the rotating shaft of the drive device 36 of the rotation mechanism 30.

[0071] Alternatively, when the inner diameter of the sizing ring is changed, one of the external teeth of the first holding member and the second holding member is engaged with an external gear fitted to the rotation shaft of the drive device 36 of the rotation mechanism 30. That is, in this example, the inner diameter of the sizing ring is changed by rotating one of the first holding member and the second holding member by the drive device 36 of the rotation mechanism 30. When the entire sizing ring is rotated, both of the external teeth of the first holding member and the second holding member are engaged with an external gear fitted to the rotation shaft of the drive device. In this case, the second cooling device 14 may be provided with an engagement state switching mechanism that engages the external gear fitted to the rotation shaft of the drive device 36 of the rotation mechanism 30 with one of the external teeth of the first holding member and the second holding member, or with both of them.

[0072] According to this modification, similarly to the embodiment, it is possible to prevent unevenness from occurring on the outer periphery of the film roll body 22. Moreover, since the sizing ring is directly rotated, i.e., the water tank 26 is not rotated, the problem of the hose connected to the supply port 26c of the water tank 26 being twisted does not occur.

[0073] (Variation 3) In the embodiment and the above-mentioned modified example, the second cooling device 14 is provided with the rotation mechanism 30, but the present invention is not limited to this, and the second cooling device 14 may have a configuration in which the second cooling device 14 does not have a rotation mechanism. That is, a configuration in which the multiple blades 50, 150 constituting the variable-size insertion hole 28a are not rotated may be considered.

[0074] (Variation 4) In the embodiment and the above-mentioned modified example, the sizing ring 28, 128 of the second cooling device 14 is provided with the inner diameter variable mechanism 32, 132. However, the present invention is not limited to this, and the sizing ring may not be provided with the inner diameter variable mechanism. That is, the inner diameter of the sizing ring may not be variable. In other words, the sizing ring may be formed in a tubular shape having a cylindrical inner circumferential surface. The rotation mechanism may directly rotate the sizing ring, or may rotate the sizing ring by rotating the water tank 26. By rotating the sizing ring, it is possible to suppress variations in the film thickness of the bubble due to processing errors in the inner circumferential surface of the sizing ring or installation errors of the sizing ring.

[0075] Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present invention. A new embodiment resulting from the combination has the combined effects of the respective embodiments and modifications. [Explanation of symbols]

[0076] 1 inflation molding device, 24 bubble, 26 water tank, 28,128 sizing ring, 30 rotating mechanism, 50,150 blade.

Claims

1. A downward water-cooled inflation molding apparatus, Equipped with a sizing ring that determines the outer diameter of the bubble, The sizing ring includes an inner diameter varying mechanism that changes the inner diameter of the sizing ring, The sizing ring is placed in a water tank, The inner diameter varying mechanism includes a plurality of inner diameter defining members arranged in parallel in a circumferential direction to define the inner diameter, An inflation molding apparatus, wherein each of the plurality of inner diameter defining members overlaps at least one of the other inner diameter defining members when viewed in a radial direction, but does not overlap with the other inner diameter defining members when viewed in an axial direction.

2. An inflation molding apparatus as described in claim 1, further comprising a rotation mechanism for rotating the inner diameter defining member.

3. The inflation molding apparatus according to claim 2 , wherein the rotation mechanism rotates the sizing ring.

4. A downward water-cooled inflation molding apparatus, Equipped with a sizing ring that determines the outer diameter of the bubble, The sizing ring includes an inner diameter varying mechanism that changes the inner diameter of the sizing ring, The sizing ring is placed in a water tank, The inflation molding apparatus further includes a rotation mechanism that rotates the sizing ring.

5. A downward water-cooled inflation molding apparatus, Equipped with a sizing ring that determines the outer diameter of the bubble, The sizing ring includes an inner diameter varying mechanism that changes the inner diameter of the sizing ring, The inflation molding apparatus further comprises a rotation mechanism for rotating the sizing ring during molding.

6. A downward water-cooled inflation molding apparatus, Equipped with a sizing ring that determines the outer diameter of the bubble, The sizing ring includes an inner diameter varying mechanism that changes the inner diameter of the sizing ring, The inflation molding apparatus further includes a rotation mechanism that rotates the sizing ring while maintaining the size of the inner diameter of the sizing ring.

7. 7. The inflation molding apparatus according to claim 2, wherein the rotation mechanism rotates the sizing ring together with a water tank that accommodates the sizing ring.

8. 4. The inflation molding apparatus according to claim 1, wherein the inner diameter varying mechanism changes the inner diameter of the sizing ring by changing a relative position between one inner diameter defining member and another inner diameter defining member.

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