JPH0230265Y2 - - 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 out from circumferential slits formed in cooling rings stacked in single or multiple stages inside the molten bubble and discharged from the center. When cooling air is blown out from the circumferential slits of the cooling ring, the wind speed becomes too high, causing the bubbles to vibrate up and down or left and right, 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 bubble vibration, the wind speed from the slit must be kept below a certain value, but this limits the amount of cold air and reduces the bubble 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, and uses a large amount of cold air to properly blow the bubbles from the inside without causing the still molten bubbles to vibrate up and down or left and right after being extruded from the extrusion die. 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-mentioned object, this invention provides a device 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 hole groups formed in the tube wall that is guided from the inside, and a central cold air supply channel whose lower end communicates with the die central cold air outlet and whose upper end is closed, sharing an axis within the outer tube. an inner tube forming a
An intermediate tube is provided between the outer tube and the inner tube, the upper end of which opens into the bubble, and the lower end of which communicates with the exhaust suction path of the die to form a cylindrical exhaust passage around the inner tube; These outer tube, middle tube, and inner tube are arranged on the upper surface of the die, and between the outer tube and the middle tube, there is a cold air discharge chamber and an air return chamber that are mutually partitioned by a doughnut-shaped partition plate. The cold air discharge chambers are arranged alternately in the axial direction, and each of the cold air discharge chambers communicates with the inside of the inner pipe through several short pipes arranged radially across the cylindrical exhaust passage. Further, the bubble internal cooling device for inflation film molding is characterized in that several exhaust holes are formed in each intermediate pipe between each air return chamber and the adjacent exhaust passage. It is characterized by

<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 dimension by cold air blown into the interior, and is similarly cooled by cold air from the external cold air ring E and internal cold air, and is then cooled by the guide plate F. The sheet passes through a pair of holding rolls G, is folded into a sheet, and is wound onto a winding drum H. The internal cooling device 10 of the present invention is installed on the die C so as to be located inside the bubble W.

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 formed by forming a metal punching plate having a large number of small holes 11a 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.

Intermediate pipe 1 located between this outer pipe 11 and inner pipe 12
The upper end 15a of the inner tube 5 opens into the bubble W, and the lower end 15b communicates with the exhaust suction passage _C1 of the die C, forming a cylindrical exhaust passage 16 around the inner tube 12.

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

Between the outer tube 11 and the intermediate tube 15, cold air discharge chambers 18 and air return chambers 19 are arranged alternately in the direction of the axis O in such a manner that they are mutually partitioned by donut-shaped partition plates 17. It is set up.

Each of the cold air discharge chambers 18 communicates with the inside of the inner pipe 12 through several short pipes 20 arranged radially across the cylindrical exhaust passage 16, and the cold air from the inner pipe 12 is communicated with the inner pipe 12. is distributed and supplied to each cold air discharge chamber 18 formed hierarchically by these short pipes 20, and forms a path for blowing out toward the inner surface of the bubble W from a group of small holes 11a formed in the tube wall of the outer tube 11.

In addition, the intermediate pipe 15 located between each air return chamber 19 and the adjacent exhaust passage 16 includes:
Several exhaust holes 21 are bored in each, 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 and is returned to each air outlet. A path is formed that returns to the exhaust passage 16 from the exhaust hole 21 via the chamber 19.

The tube wall at the lower end of the outer tube 11 closer to the die C is a blind cylindrical body portion 11b, and a planar ring-shaped space 22 between the blind cylindrical body portion 11b and the lower end 15b portion of the intermediate tube 15 is a space for cooling air. Two inner and outer chambers 22a,
22b, the inner pressure adjustment chamber 22a is
Several short tubes 20b arranged radially in the radial direction similar to the short tubes 20 communicate with the inside of the inner tube 12, and the outer blowing chamber 22b near the blind plate 11b has air in the vicinity of the orifice D of the die C. A blowout annular outlet 22C is formed that opens at the central cold air outlet of the die C.
A portion of the cold air immediately after being blown out from C ₀ flows into the short pipe 20.
b. A passage is formed in which air passes through the inner pressure adjustment chamber 22a, the porous chamber 23, and the outer air outlet 22b in this order in a zigzag pattern, and air is emitted from the annular air outlet 22C. Needless to say, an air return chamber 19 is formed which is partitioned by .

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

<Function> The function of the internal cooling device 10 of the present invention having the above-mentioned configuration will be described below in conjunction 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,
Cool air is supplied through the cooler 1 from the central cold air outlet C ₀ of the die C into the inner tube 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 passes through the short pipe 20b at the lowest position, is dispersed in the radial direction, flows in a zigzag pattern through the pressure adjustment chamber 22a, the perforated plate 23, and the outer blowing chamber 22b, and reaches the vicinity of the orifice D of the die C. The air is blown out from the annular outlet 22c toward the inner surface of the bubble W, and rises along the bubble W and the tube wall of the outer tube 11.Other cold air flows through the short tubes 20 as it rises inside the inner tube 12. The cold air is sequentially distributed and supplied to the cold air discharge chambers 18, and then blown out from each cold air discharge chamber 18 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, whose temperature has risen slightly by contacting the inner surface of the bubble W in a molten and heated state, rises while being bubble-cooled, and flows into the next cold air discharge chamber 1.
8 through a group of small holes 11a provided in the tube wall of the outer tube 11, the air flows upwardly between the bubble W and the outer tube 11, and continues to cool the bubble W.

At this time, the cold air discharged from each cold air discharge chamber toward the inner surface of the bubble W passes through the large number of small holes 11a formed in the tube wall of the outer tube 11. Therefore, the amount of air blown out increases, and a large amount of cold air forms a 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 reaches above the intermediate tube 15 inside the bubble W, and after expanding the bubble W to a desired size, the air flows between the intermediate tube 15 and the inner tube. The air flows in and descends from the upper end of the exhaust passage 16 formed between 12 and 12, is sucked into the blower pump P via the exhaust suction path _C1 of the die C, and is exhausted.

In addition, another part of the air whose temperature has risen slightly by cooling the blow-off bubble W from each cold air discharge chamber 18 is transferred into the adjacent air return chamber 19 through a group of small holes 11a formed in the tube wall of the outer tube 11. and then flow into the radial exhaust channels 16 through the exhaust holes 21, respectively.

The bubble W internally cooled in this way has its outer peripheral surface cooled 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 through a pair of clamping rolls G to form a sheet. It is folded into a shape 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 pipe 20 and is sequentially distributed and supplied to each cold air discharge chamber 18 , and after the speed of the cold air is reduced in the cold air discharge chamber 18 , the cold air flows through the tube wall of the outer tube 11 . A small hole 11a formed in
A large amount of cold air is blown out from the group toward the bubble W over a wide area, and the cold air is flowed between the bubble W and the outer tube 11 to form a flowing air layer between the bubble W and the outer tube 11. The bubble W is reliably supported from the inner surface while being separated from the wall of the outer tube 11, and by making the wall of the outer tube 11 porous as described above, the cold air passage opening of the outer tube 11 is The total area can be increased, and the air volume can be increased even at low speeds. As a result, even if a large amount of cold air is blown from each cold air discharge chamber 18 through the pipe wall of the outer tube 11 onto the inner surface of the bubble W, the cold air will not blow out. The speed itself is not very large, and the bubble W is cooled from inside in a stable state without greatly vibrating vertically or horizontally, and the cooling effect is not only promoted, but the stability of the bubble W is due to uneven thickness. It has the effect of preventing thickening.

Further, a part of the air whose temperature has risen slightly by cooling the bubble W is sequentially released into each air return chamber 19 arranged in the axial direction alternately with the cold air discharge chamber 18 between the outer tube 11 and the middle tube 15. Since the bubbles W enter through the pipe wall of the pipe 11, are collected from the exhaust hole 21 into the exhaust passage 16, and are exhausted to the outside from this internal cooling device 10, the bubbles W are always connected to each cold air discharge over the entire length of this device. Since the bubble W comes into contact with the low temperature air blown out from the chamber 18, the bubble W can be internally cooled well.

Further, the air whose temperature has increased due to cooling of the bubble W passes through each of the air return chambers 19 to the exhaust passage 1.
6, the air that has circulated through the expanded portion of the bubble flows into the exhaust passage 16 from the upper end of the exhaust passage 16. That is, the warmed air passes through the two exhaust system paths and exits the exhaust passage 16 into the bubble W.
It can exhaust air to the outside and can cool films with a thickness of 0.25 mm or more at a sufficiently high speed.

In addition, warm air in an amount that is approximately the same as the amount of cold air blown out from the cold air discharge chamber 18 is taken into the air return chamber 19 and exhausted into the exhaust passage 16, so that the pushed out bubbles W and The amount of cold air between the tube walls of the outer tube 11 is the same everywhere, and the molten bubble W can be uniformly cooled over the entire height of the outer tube 11.

The cold air discharge chamber 18 and the air return chamber 19 are simply constructed by sequentially arranging the donut-shaped partition plates 17 between the outer tube 11 and the intermediate tube 15 at predetermined intervals in the direction of the axis O, and By fixing the ends to the outer circumferential surface of the intermediate tube 15 and the outer circumferential ends to the inner surface of the outer tube 11, they can be formed sequentially and alternately, and the partition plates 17
is a substantially flat plate-shaped material, and there is no need to perform any punching or through-hole processing in the direction of the axis O, and the shape and structure can be simplified, and the overall structure of the internal cooling device 10 can be simplified. , easy to manufacture.

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 20, and pressure loss in these supply systems can be reduced, and cold air at a predetermined pressure at a low speed and high flow rate can be discharged from each cold air discharge chamber 18. I can,
Moreover, since the inner pipe 12, which is a cold air supply pipe, is surrounded by an exhaust suction path and does not come into direct contact with the high-temperature die, the degree to which the cool air supplied into the die is warmed is small.

The intermediate tube 16 is fixedly supported by the inner tube 12 which is fixed and stands upright in the center of the die C through the plurality of short tubes 20, and each short tube 20 serves as a cold air communication tube and as a stay. On the other hand, the outer tube 11 can be fixedly arranged at intervals around the intermediate tube 16 via partition plates 17 arranged in multiple stages in the direction of the axis O, , the outer tube 11, the inner tube 12, and the intermediate tube 16 can be assembled and arranged easily and appropriately so that they are located inside the bubble W.

<Effects of Embodiment> In the above embodiment, the tube wall at the lower end of the outer tube 11 closer to the die C is formed by the blind cylindrical portion 11 having the same diameter.
b, and the central cold air outlet C ₀ of the die C
A part of the cold air, which has just been supplied into the inner pipe 12 from the inner pipe 12, passes through the short pipe 20b, the inner pressure adjustment chamber 22a, the perforated plate 23, and the outer blowing chamber 22b in this order in a zigzag pattern. From the blowout annular port 22c,
The air can be blown onto the entire inner surface of the bubble W immediately after being extruded from the orifice D of the die C, and the bubble W can be internally cooled immediately after being extruded, and the air warmed by the bubble W cooling can be generated along the outer surface of the blind cylindrical portion 11b. The bubble W is guided upward to the upper air return chamber 19 in a stable state, and since low-temperature air is always successively supplied to the inside of the blind cylindrical part 11b, the outside of this part The air flowing through the bubble W is cooled from inside while flowing through this section, making the cooling effect of the bubble W 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 has the ability to cool the inner surface of the bubble W by blowing cold air at a low velocity and a large amount of air. It can be manufactured using simple and inexpensive materials.

The total area of the cold air passage openings in the tube wall of the outer tube 11 facing each of the cold air discharge chambers 18, that is, the small holes 11a.
In an embodiment in which the number of small holes 11a of the same diameter in the tube wall of the outer tube 11 facing the air return 19 is slightly smaller than the number of small holes 11a of the same diameter, the increase in the amount of air due to the expansion of air due to heating can be sufficiently compensated for. Next air return chamber 1
It has an effect that can be recovered in 9.

[Brief explanation of the drawing]

The figures are shown in place of this invention; FIG. 1 is a sectional view of a typical embodiment of the internal cooling device of the invention;
FIG. 2 is a cross-sectional view thereof, and FIG. 3 is a schematic diagram showing a method of forming a blown film using this internal cooling device. Explanation of main symbols in the figure, 10...Internal cooling device, 11...Outer pipe, 12...Inner pipe, 15...Intermediate pipe, 16...Exhaust passage, 18...Cold air discharge chamber, 1
9...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 the die of an extrusion molding machine from the inside, a large number of small holes are formed in the tube wall that guides the bubble from the inside. An outer tube is formed, an inner tube that shares an axis within the outer tube and has a lower end communicating with the die central cold air outlet and an upper end closed to form a central cold air supply path; and the outer tube and the inner tube. An intermediate pipe is located between the inner pipe and the upper end opens into the bubble, and the lower end communicates with the exhaust suction path of the die to form a cylindrical exhaust passage around the inner pipe. and an inner tube are arranged on the upper surface of the die, and between the outer tube and the intermediate tube, cold air discharge chambers and air return chambers, which are mutually partitioned by donut-shaped partition plates, are arranged alternately in the axial direction. Each of the cold air discharge chambers communicates with the inside of the inner pipe through several short pipes arranged radially across the cylindrical exhaust passage. A bubble internal cooling device for inflation film molding, characterized in that several exhaust holes are formed in each intermediate pipe between the chamber and the adjacent exhaust passage. 2. The bubble internal cooling device for inflation film molding according to claim 1, wherein the outer tube comprises a punching plate having a large number of holes. 3. Utility model registration claim 1, wherein the total area of the cold air passage openings in the pipe wall of the outer tube facing each of the cold air discharge chambers is set to be slightly smaller than the total area of the cold air passage openings facing the air return chamber. Bubble internal cooling device for inflation film molding as described in Section 3.