JPH0230266Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial field> This invention supplies cold air from inside the die to the inside of a bubble made of a synthetic resin tube extruded from the die of an extrusion molding machine in inflation film molding. It relates to a device that forcibly cools bubbles extruded from the inside that are still in a molten state from the inside.

<Prior art> In this type of inflation film forming, bubbles that are still in a molten state immediately after being extruded from a die are expanded by the air sealed inside in the cooling and solidification process, and are formed into the desired shape. It is molded to the film width dimension. In addition, in order to make a thick film uniform in tensile strength all around and to obtain a high-quality film, we cool the bubble from the outside as well as from the inside. As with external cooling, this uses cold air for internal cooling, and in the process of blowing this cold air into the bubble from the die and circulating it, it expands and cools the bubble, and then discharges it to the outside of the bubble through the die. ing.

<Problems to be solved by the invention> However, the conventional bubble internal cooling device using cold air is
As described in Publication No. 57257, cold air is blown inside the molten bubble through circumferential slits formed in cooling rings stacked in multiple stages, and is discharged from the center. When cooling air is blown out from the circumferential slits of the cooling link, the wind speed becomes too high, causing the web to vibrate vertically or horizontally, making film forming unstable and causing uneven width dimensions of the formed film. This may cause uneven thickness.

In order to blow out cold air without vibration of the web, the wind speed from the slit must be kept below a certain value, but this limits the amount of cold air and reduces the web cooling effect. The problem is that there is a limit to the thickness of the film that can be molded, making it unsuitable for molding thick films.

The present invention improves the drawbacks of the prior art described above, and allows the web, which is still in a molten state immediately after being extruded from the extrusion die, to be smoothly blown from the inside by using a large amount of cold air without significantly vibrating vertically or horizontally. After cooling, a film with a constant width and uniform thickness is made into a thin film.
The main object of the present invention is to provide a bubble internal cooling device for inflation film molding, which allows stable molding regardless of thickness.

<Means for Solving the Problems> In order to achieve the above object, this invention provides an apparatus for cooling the inside of a bubble made of a synthetic resin tube extruded from a die of an extrusion molding machine from the inside. An outer tube having a large number of small holes formed in the tube wall that guides the die from the inside, and a central cold air supply channel that shares an axis within the outer tube, has a lower end communicating with the die central cold air outlet, and an upper end closed. and two intermediate tubes, an inner tube and an inner tube, which share the axis between the outer tube and the inner tube, are arranged concentrically on the upper surface of the die, and the upper end of the inner intermediate tube is a bubble. A cylindrical exhaust passage is formed around the inner tube, and the lower end thereof is connected to the exhaust suction passage of the die, and the upper end of the outer intermediate tube is opened inside the bubble, and the lower end thereof is closed. A cylindrical air ascending ventilation passage is formed around the inner intermediate pipe, and between the outer pipe and the outer intermediate pipe, a cold air discharge chamber and an air are separated from each other by a doughnut-shaped partition plate. Return chambers are arranged alternately in the axial direction, and each of the cold air discharge chambers is formed by a group of several short pipes in two stages, upper and lower, arranged radially across the exhaust passage and the ascending ventilation passage. Several exhaust holes are perforated in each of the outer intermediate pipes communicating with the inside of the inner pipe and between each air return chamber and the adjacent air rising passage. is connected to the exhaust passage near the upper end through a group of holes drilled in the inner intermediate pipe, and the upper end of the inner intermediate pipe located above the small hole group is located higher than the upper end of the outer intermediate pipe. , a bubble internal cooling device in inflation film molding, characterized in that it forms a mixing prevention ring for rising airflow and return airflow.

<Embodiment> Next, a typical embodiment of this invention will be described based on the drawings.

Figure 3 shows the schematic configuration of an inflation film molding machine. Molten resin extruded from extruder A by screw B is sent to die C, and extruded as bubbles W from orifice D of die C. be done. As will be described later, this bubble W is expanded to a desired film width by cold air blown into the inside, and is similarly cooled by cold air from the external cold air ring E and cold air from the internal cooling device 10, and then guided. The sheet F passes through a pair of clamping rolls G, is folded into a sheet, and is wound onto a winding drum H. The internal cooling device 10 of the present invention has a die C
It is installed so as to be located inside the bubble W at the top.

FIGS. 1 and 2 show an embodiment of the internal cooling device of the present invention, and in the figures, 11 is
There are many small holes 1 in the tube wall that guide the bubble W from the inside.
The outer tube 1a is preferably a metal punching plate having a large number of small holes 11a formed into a cylindrical body having a predetermined diameter.

An inner pipe 12 sharing the axis O is disposed within the outer pipe 11, and the central cold air supply path 1 is connected to the inner pipe 12.
3 is formed, the upper end of which is closed by an umbrella-shaped end plate 14, and the lower end thereof communicates with the central cold air outlet _C0 of the die C.

Two intermediate tubes 15 and 16, an inner and outer tube, are arranged between the outer tube 11 and the inner tube 12, sharing the axis O,
The upper end 15a of the inner intermediate tube 15 opens into the bubble W, and the lower end 15b of the inner intermediate tube 15 is
A cylindrical exhaust passage 17 communicating with the exhaust suction passage C ₁ of the die C is formed around the inner tube 12 .

Further, the upper end of the outer intermediate pipe 16 also opens into the bubble W, and its lower end is closed by a ring-shaped end plate 18 to form a cylindrical air ascending passage 19 around the inner intermediate pipe 15. There is.

These outer tube 11, inner and outer intermediate tubes 15, 16, and inner tube 12 are arranged on the upper surface of the die C so as to be located inside the bubble W.

A cold air discharge chamber 21 is formed between the outer pipe 11 and the outer intermediate pipe 16 by a doughnut-shaped partition plate 20.
The air return chambers 22 are mutually partitioned and arranged alternately every other space in the direction of the axis O.

Each of the cold air discharge chambers 21 has a set of several pipes arranged radially across the cylindrical exhaust passage 17 and the air rising passage 19, and is formed by groups of short pipes 23 arranged in two stages above and below. A group of small holes 11a formed in the wall of the outer tube 11 communicates with the inside of the inner tube 12, and the cold air from the inner tube 12 is distributed and supplied to each cold air discharge chamber 21 formed hierarchically by these short tubes 23. A path is formed from which air is blown out toward the inner surface of the web W.

Further, an outer intermediate pipe 16 located between each air return chamber 22 and the adjacent air rising passage 19
Several exhaust holes 24 are bored in each of the holes, and a part of the cooled air rising between the inner surface of the bubble W and the outer tube 11 passes through a group of small holes 11a formed in the wall of the outer tube 11. The air passes through each air return chamber 22, passes through the exhaust hole 24, ascends into the bubble W, and forms a path from which air is blown out from the upper end of the passage 19.

The air rising passage 19 communicates with the exhaust passage 17 through a group of holes 15c bored near the upper end 19a thereof, and a part of the air passing through the air rising passage 19 passes through these holes 15c and enters the exhaust passage 17. It forms a return route.

The upper end 15a of the inner intermediate pipe 15 is located above the upper end of the outer intermediate pipe 16 and downstream in the transfer direction of the instant bubble W, and this upper end 15a prevents mixing of the upward air flow and the return air flow. An air mixing prevention ring 30 is formed.

Note that the tube wall at the lower end of the outer tube 11 closer to the die C is connected to the blind cylindrical body portion 11b and the inner intermediate tube 15.
A planar ring-shaped space 25 between the lower end 15b of the
is a cylindrical perforated plate 26 through which cold air can freely pass.
It is divided into two inner and outer chambers 25a and 25b.
The outer blow-off chamber 2 is connected to the inside of the
5b is formed with an annular blowout port 25c that opens near the orifice D of the die C, and a portion of the cold air immediately after being blown out from the central cold air blowout port _C0 of the die C is transferred to the short pipe 27 and the inner pressure adjustment chamber. 25a, perforated plate 26,
A passage is formed that passes through the outer blow-off chambers 25b in a zigzag pattern and blows out air from the blow-off annular opening 25c, and the lower end 1 of the outer intermediate pipe 16 is directly above the ring-shaped space 25.
6b is closed by an end plate 18, and directly above this space 25 is an air return chamber 22 partitioned by the partition plate 20.
Needless to say, it is formed.

The central cold air outlet C ₀ of the die C and the inner intermediate pipe 15 are connected to a cold air circulation circuit J that includes, for example, a blower pump P and a cooler I, as shown in FIGS. 1 and 3.

<Operation> The operation of the present invention configured as described above will be explained below along with inflation film molding.

First, by operating the extrusion molding machine A, bubbles W in a molten state are extruded from the orifice D of the die C.
is guided along the wall of the outer tube 11 and rises.

On the other hand, the blower pump P of the cold air circulation device J is driven, and the central cold air outlet of the die C is driven through the cooler 1.
Cool air is supplied from C ₀ into the inner pipe 12 of the internal cooling device 10 of the present invention located inside the bubble W.

A part of the cold air supplied in this way is dispersed in the radial direction through the short pipes 27 in the two lowermost stages, respectively, and flows in a zigzag pattern through the inner pressure adjustment chamber 25a, the perforated plate 26, and the outer blowing chamber 25b. It is blown out toward the inner surface of the bubble W from the blowout annular opening 25c near the orifice D of the die C, and rises along the bubble W and the tube wall of the outer tube 11, while other cold air rises inside the inner tube 12. , each cold air discharge chamber 2 via the short pipe 23
1, and then distributed to each cold air discharge chamber 21.
The air is blown out toward the bubble W through a group of small holes 11a formed in the tube wall of the outer tube 11, and rises along the bubble W.

The cold air rising between the outer tube 11 and the bubble W is
A part of the air that comes into contact with the inner surface of the heated bubble W and cools it, and whose temperature rises slightly due to cooling,
The bubble continues to cool while rising, joins with the cold air blown from the next cold air discharge chamber 21 through the small hole group 11a provided in the tube wall of the outer tube 11, and moves upward between the bubble W and the outer tube 11. Bubble W
continue to cool.

At this time, the cold air discharged from each cold-air discharge chamber 21 toward the inner surface of the bubble W is discharged from a large number of small holes 11a formed in the tube wall of the outer tube 11, so the amount of air blown out increases. A large amount of cold air is supplied between the bubble W and the outer tube 11 over a relatively wide area.

Finally, the air that comes out from between the bubble W and the outer tube 11 is transferred to the two intermediate tubes 15 and 1 inside the bubble W.
6, and after expanding the bubble W to a desired size, this air flows in and descends from the upper end of the exhaust passage 17 formed between the inner intermediate pipe 15 and the inner pipe 12, and flows into the blower pump P through the die C. is sucked in and exhausted through the exhaust suction path _C1 .

In addition, a part of the air whose temperature has risen slightly by cooling the blowing bubble W from each cold air discharge chamber 21 is transferred into the adjacent upper air return chamber 22 through a group of small holes 11a formed in the tube wall of the outer tube 11. A part of the air, which is guided and then rises in the air rising passage 19 and whose temperature has risen slightly at the upper end of the air rising passage 19, passes through the hole 15 provided near the upper end of the inner intermediate pipe 15.
The air flows into the exhaust passage 17 from group c, and is sucked into the blower pump P together with the air that flows in and descends from the upper end of the exhaust passage 17, and is exhausted.

The remaining warmed air is sucked out from the upper end of the air rising passage 19, joins with the air rising between the bubble W and the outer tube 11, and adjusts the bubble W immediately after exiting the internal cooling device 10 to a desired diameter. The air is rapidly expanded and inflated, and at this time, the air mixing prevention ring 30 prevents the air blowing out from the upper end of the air rising passage 19 and the air flowing into the exhaust passage 17 from the upper end from mixing immediately.

The bubble W cooled internally in this way is also cooled from the outside by the cold air blown out from the external cold air ring E, expands and solidifies to a predetermined width, and then passes from the guide plate F to the pair of clamping rolls G. It is folded into a sheet and wound onto a winding drum H.

<Effects> The internal cooling device 10 of the present invention, which is constructed and operates as described above, has the following effects.

The cold air supplied into the inner pipe 12 passes through the short pipes 23 in two stages, upper and lower, and is sequentially distributed and supplied to each cold air discharge chamber 21, and after the speed of the cold air is reduced in this cold air discharge chamber 21, it is transferred to the outer tube 11. A large amount of cold air is blown out over a wide area toward the bubble W from the small hole group 11a formed in the tube wall of the tube, and the bubble W and the outer tube 11 are
By flowing cold air between them and forming a flowing air layer between the bubble W and the outer tube 11, the outer tube 11
The bubble W is reliably supported from the inner surface while being separated from the tube wall of the outer tube 11, and by making the tube wall of the outer tube 11 porous as described above, the total area of the cold air passage opening of the outer tube 11 is increased. As a result, even if a large amount of cold air is blown from each cold air discharge chamber 21 through the pipe wall of the outer tube 11 and onto the inner surface of the bubble W, the blowing speed of the cold air itself is low. It is not that big, the bubble W does not vibrate greatly vertically or horizontally, the bubble W is cooled from inside in a stable state, and the cooling effect is not only promoted, but the stability of the bubble W prevents uneven wall thickness. be effective.

In particular, each cold air discharge chamber 21 has two sets of upper and lower short pipes 2.
Since the third group communicates with the inside of the inner pipe 12, a large amount of cold air can be supplied at once from the upper and lower positions from the inner pipe 12 to each cold air discharge chamber 21 through the short pipe 23 groups arranged in two stages, upper and lower. Therefore, the overall height of the internal cooling device 10 of the present invention that cools the bubble W in a molten state can be increased without increasing the volume of each cold air discharge chamber 21 and increasing the number of cold air discharge chambers 21 arranged in the axial direction. The height can be lowered and the structure can be simplified.

The cold air discharge chamber 21 and the air return chamber 22 are constructed by simply inserting the donut-shaped partition plate 20 into the outer tube 11 and the outer intermediate tube 1 at a predetermined interval in the direction of the axis O.
By sequentially arranging the partition plates 20 between 6 and 6, the partition plates 20 can be formed sequentially and alternately, and since each partition plate 20 is a substantially flat plate-like material, there is no need to perform any punching or through-hole processing in the direction of the axis O. , its shape and structure can be simplified, the structure of the entire internal cooling device 10 can be simplified, and it is easy to manufacture. Note that this partition plate 20 is composed of two divided bodies for convenience of assembly.

Since the central cold air supply path 13 is formed by the inner pipe 12, the central cold air outlet of the die C
A large amount of cold air can be supplied from C ₀ to each cold air discharge chamber 18 from each short pipe 23, and pressure loss in these supply systems can be reduced. In addition, since the inner tube 12 is surrounded by an exhaust suction path and is not in direct contact with the high-temperature die C, the degree to which the cool air supplied into the die C is warmed is small.

The inner and outer intermediate tubes 15 and 16 are fixedly supported by the inner tube 12 fixed and standing upright at the center of the die C via the plurality of short tubes 23, and each short tube 23 serves as a cold air communication tube. On the one hand, the outer tube 11 can be fixedly arranged at intervals around the outer intermediate tube 16 via partition plates 20 arranged in multiple stages in the direction of the axis O. Therefore, the outer tube 11, the inner tube 12, and the inner and outer intermediate tubes 15 and 16 can be easily and appropriately assembled and arranged on the upper surface of the die C so as to be located inside the bubble W.

The air mixing prevention ring 30 allows the air blown out from the upper end of the air rising passage 19 to mix with the air rising between the bubble W and the outer tube 11 without mixing with the air flowing into the exhaust passage 17 from the upper end. , the bubble W can be mixed with the air rising between the outer tube 11, and the bubble W can be expanded to a desired diameter by a large amount of air pressure.

Furthermore, a hole 15 provided at the upper end of the rising air passage 19
c, a portion of the air in this passage 19 can be sucked into the exhaust passage 17 by a bench pull action, and in turn, the warm air can be sucked and raised along this passage 19 via the air return chamber 22.

<Effects of Embodiment> In the embodiment described above, the tube wall at the lower end of the outer tube 11 closer to the die C is a blind cylindrical portion 11b having the same diameter, and the central cold air outlet of the die C
A portion of the cold air, which still has a high cooling capacity, immediately after being supplied into the inner pipe 12 from C ₀ flows into the short pipe 27 in two stages, upper and lower.
The bubble W passes through the group, the inner pressure adjustment chamber 25a, the porous plate 26, and the outer blowing chamber 25b in this order in a zigzag pattern, and is sprayed from the blowing annular opening 25c to the entire inner circumference of the bubble W immediately after being extruded from the orifice D of the die C. The bubble W can be internally cooled immediately after extrusion molding, and the bubble W can be cooled along the outer surface of the blind cylindrical part 11b.
Air warmed by cooling is guided upward, the bubble W is guided to the upper air return chamber 22 in a stable state, and low-temperature air is always sequentially supplied to the inside of the blind cylindrical portion 11b. Therefore, the air flowing outside this section is cooled from the inside while flowing through this section, making the cooling effect of the bubble more pronounced.

In an embodiment in which the outer tube 11 is formed of a cylindrical punching plate having a large number of holes 11a, the outer tube 11, which has the ability to cool the inner surface of the bubble W by blowing low-velocity and large-volume cold air, is simplified. , can be manufactured from inexpensive materials.

The total area of cold air passage openings in the tube wall of the outer tube 11 facing each of the cold air discharge chambers 21, that is, the small holes 11a.
In an embodiment in which the number of small holes 11a having the same diameter in the wall of the outer tube 11 facing the air return chamber 22 is slightly smaller than the number of small holes 11a having the same diameter, the increase in the amount of air due to the expansion of air due to heating can be sufficiently compensated for. This has the effect that the air can be recovered in the next air return chamber 22.

[Brief explanation of the drawing]

The figures relate to this invention; FIG. 1 is a longitudinal cross-sectional view of a typical embodiment of the internal cooling device of the present invention, FIG. 2 is a cross-sectional view of FIG. 1, and FIG. FIG. 2 is a schematic diagram showing a method of forming an inflation film using this internal cooling device. Explanation of main symbols in the figure, 10... Internal cooling device, 11... Outer tube, 12... Inner tube, 15, 16...
...Inner and outer intermediate pipes, 17...Exhaust passage, 21...Cold air discharge chamber, 22...Air return chamber.

Claims (1)

[Claims for Utility Model Registration] 1. In a device that cools the inside of a bubble made of a synthetic resin tube extruded from a die of an extrusion molding machine from the inside, a group of small holes are formed in the tube wall that guides the bubble from the inside. an inner tube that shares an axis within the outer tube and whose lower end communicates with the die central cold air outlet and whose upper end is closed to form a central cold air supply path; and the outer tube and the inner tube. Two intermediate tubes, an inner and an outer tube, are arranged concentrically on the upper surface of the die, and the upper end of the inner intermediate tube opens into a bubble, and the lower end thereof is connected to the exhaust suction of the die. A cylindrical air exhaust passage communicating with the inner tube is formed around the inner tube, the upper end of the outer intermediate tube opens into the bubble, the lower end thereof is closed, and the cylindrical air ascending air passage is connected to the inner intermediate tube. A cold air discharge chamber and an air return chamber are formed around the tube, and are alternately arranged in the axial direction between the outer tube and the outer intermediate tube, and are partitioned from each other by a donut-shaped partition plate. Each of the cold air discharge chambers communicates with the inside of the inner pipe through a group of several short pipes arranged in a radial pattern that radially crosses the exhaust passageway and the ascending ventilation passageway. In addition, several exhaust holes are bored in each of the outer intermediate pipes between each air return chamber and the adjacent air ascending passage,
This air rising passage becomes an exhaust passage near the top end,
They communicate through a group of holes drilled in the inner intermediate tube, and the upper end of the inner intermediate tube located above the small hole group is located higher than the upper end of the outer intermediate tube, and has a ring for preventing mixing of rising air flow. A bubble internal cooling device for inflation film forming. 2. The bubble internal cooling device for inflation film molding according to claim 1, wherein the outer tube comprises a metal punching plate with a large number of holes. 3. The total area of the cold air passage openings formed by the small holes formed in each cold air discharge chamber of the outer pipe is equal to the total area of the cold air passage openings formed by the small holes formed in each air return chamber. 2. The bubble internal cooling device for inflation film molding according to claim 1, wherein the bubble internal cooling device is set to be slightly smaller than the total area of the return air passage openings.