JPH0230268Y2 - - 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, the bubbles, which 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 the bubbles are expanded into the desired shape. It is molded to the film width dimension of . 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. There is.

<Problems to be solved by this invention> In a conventional example of a bubble internal cooling device using this type of cold air, as shown in FIG. The cold air from the air supply pipe D of the die C is sequentially supplied into each ring A through the vertical short pipes E to G, and the slit-shaped slits protruding from the outer peripheral surface of each ring A are arranged vertically. Cold air is blown out from the cold air discharge lip H to the inner surface of the bubble, but since the inside of the upper and lower rings A are communicated with each other through the vertical short pipes E, F, and G, the cold air is blown out from the upper ring A. Assuming that the supplied air volume is reduced compared to the one in the lower tier and is slightly insufficient, and the area of each lip H is constant,
The speed of the cold air blown out from these becomes weaker in the upper stages.
The velocity of the cold air from the lip H of the ring A at each stage becomes non-uniform, and the bubble cooling effect of the cold air cannot be made constant even at all height positions, causing the bubble to vibrate vertically or horizontally.

In order to improve such drawbacks, a conventional technique in which the cross-sectional area of the vertical pipes E, F, and G in each stage is made larger toward the lower stage is described in Japanese Patent Publication No. 7854/1983, but the setting However, it is difficult to manufacture and has a complicated structure, so there is still room for improvement.

Further, the cold air blown from the lip H of each ring A passes through a cylindrical air guide path I having a short axial length between each ring A, and then passes through the central pipe K forming the central exhaust passage J and the ring A. Since the air is sucked into the annular suction passage L formed between the inner walls and rises, the pressure inside this air guide passage I becomes a negative pressure state lower than atmospheric pressure, and the bubbles being cooled internally are cooled by the cold air. There is a risk that some of the air may be sucked into the internal cooling device side at the position of this air guide path I, that is, the position between the upper and lower rings A, and come into close contact with the internal cooling device. This results in vertical vibration, which tends to cause uneven thickness in the bubble when the bubble is wound up, and in the worst case, the bubble may break, reducing the efficiency of film forming.

These matters can be pointed out as problems.

This invention improves the problems of the prior art,
The main objective is to provide a device that internally cools bubbles uniformly without vibration.

<Means for solving the problem> This invention is a bubble internal cooling device devised to solve the above-mentioned main purpose. A bubble internal cooling device for inflation film molding that cools from the inside with cold air includes an inner tube whose upper end is closed and whose lower end communicates with the central cold air outlet of the die to form a central cold air supply path; an inner intermediate tube opening into the bubble and having a lower end communicating with an annular exhaust port of the die to form a cylindrical air exhaust passage around the inner tube; An outer intermediate tube that is closed by a plate and forms a cylindrical rising air passage around the inner intermediate tube is disposed concentrically on the upper surface of the die, sharing the same axis, and is arranged concentrically on the upper surface of the die, Several sets of upper and lower ring-shaped members are fixed adjacently at intervals in the axial direction.
A flat ring-shaped cold air discharge chamber is formed by the pair of upper and lower mold members of each set and the circumferential surface of the outer intermediate pipe.
A circumferentially slit-shaped cold air discharge groove is formed between the outward facing lip piece of the upper mold material and the inward facing lip piece of the lower mold material in each cold air discharge chamber and communicates with the cold wind discharge chamber. The chambers and the central cold air supply passage communicate with each other through a number of horizontal short pipes arranged radially across the air exhaust passage and the rising air passage, and between the upper and lower adjacent cold air discharge chambers. , a cylindrical body with a large number of small holes is stretched flush with the tip surface of the cold air discharge groove; A cylindrical air return chamber is formed, and the outer intermediate pipe between the air return chamber and the rising air passage is provided with a large number of communication holes, and the upper end of the inner intermediate pipe is provided with a passageway from the rising air passage. This bubble internal cooling device for inflation film molding is characterized in that a ring-shaped prevention plate is attached to prevent mixing of blown air and air flowing into the upper end of an air exhaust passage.

<Embodiment> Next, a typical embodiment of this invention will be described based on FIGS. 1 and 2.

1 and 2, 10 is the bubble internal cooling device of the present invention, and its inner tube 11 is
The upper end is closed by a cap-shaped end plate 12, and the lower end is a central cold air outlet 14 provided in the die 13 of the extrusion molding machine.
, and forms a central cold air supply path 15. The upper end of the inner intermediate pipe 16 surrounding this inner pipe 11 opens into the bubble W, and the lower end communicates with the annular air exhaust port 17 of the die 13, forming a cylindrical air exhaust passage 18 around the inner pipe. do. Furthermore, this inner intermediate pipe 1
The upper end of the outer intermediate tube 19 surrounding the inner intermediate tube 16 opens into the bubble W, and the lower end thereof is closed by a ring-shaped end plate 20 to form a cylindrical rising air passage 21 on the outer periphery of the inner intermediate tube 16. .

These inner tube 11, inner intermediate tube 16, and outer intermediate tube 19 share the same axis and are arranged concentrically on the die 12.

A pair of upper and lower ring shaped members 22, 2 are provided on the outer peripheral surface of the outer intermediate tube 19 at intervals in the axial direction.
3 are fixed adjacent to each other, and a planar ring-shaped cold air discharge chamber 24 is formed by the pair of upper and lower ring shaped members 22, 23 of each pair and the circumferential surface of the outer intermediate pipe 19. Inner profile 22 in chamber 24
A circumferentially slit-shaped cold air discharge groove 25 is formed between the outward facing lip piece 22 a of the outer mold member 23 and the inward facing lip piece 23 a of the outer mold member 23 and communicates with the cold air discharge chamber 24 . The central cold air supply passage 11 radially connects the air exhaust passage 1 in a radial direction.
8. They communicate with each other by horizontal short pipes 26 arranged so as to straddle the rising air passage 21, and the cold air supplied to the central cold air supply path 15 is sent to each air discharge chamber through the group of short pipes 26. 24, and a path is formed through which cold air is blown toward the inner surface of the bubble W from the slit-shaped air discharge groove 25 in the circumferential direction of each air discharge chamber 24.

A cylindrical body 28 in which a large number of small holes 27 are bored is stretched between the upper and lower adjacent cold air discharge chambers 24 so as to be flush with the tip surface of the cold air discharge groove 25.
A cylindrical air return chamber 2 is formed by the shapes 22 and 23 and the outer circumferential surface of the outer intermediate pipe 19, which are spaced apart from each other.
9 is formed.

That is, the cold air discharge chamber 24 and the air return chamber 29 are separated from each other by the shapes 22 and 23, and are alternately arranged in a ring shape on the circumferential surface of the inner intermediate tube 19 in the axial direction.

A large number of communication holes 3 are provided in the peripheral wall of the outer intermediate pipe 19 between each air return chamber 29 and the rising air passage 21.
0 is bored, and the air flowing into each air return chamber 29 through the group of small holes 27 of the cylinder body 28 is passed through these communication holes 30.
A path is formed through which the air is guided into the cylindrical rising air passage 21, raised, and blown out into the bubble W from its upper end.

In order to prevent the air blown into the bubble W from the upper end of the rising air passage 21 from mixing with the air flowing into the air exhaust passage 18 from the upper end, the inner intermediate pipe 1
A ring-shaped prevention plate 31 is attached to the upper end of 6.

A cylindrical body 32 is arranged between the lowest air return chamber 29 and the upper surface of the die 13.
A cylindrical cold air blowing chamber 33 is formed between the inner surface and the circumferential surface of the inner intermediate pipe 16.

This air blowing chamber 33 is divided into a concentric inner chamber 33a and an outer chamber 33b by a wire mesh cylindrical partition wall 34, and this inner chamber 33a and a central cold air supply path 15
are connected to each other by two pairs of upper and lower second short pipes 35 disposed radially across the air exhaust passage 18, and an upwardly directed circular air outlet 33c is provided at the lower end of the outer chamber 33b. Bubble outlet 36 of die 13
is formed close to.

<Function> The function of the present bubble internal cooling device 10 having the above configuration will be described below.

The first blower P ₁ connected to the central cold air outlet 14 of the die 13 and the second blower P ₂ connected to the annular exhaust port 17 of the die 13 are started, and the present bubble internal cooling device is discharged from the central cold air outlet 14. Cold air is supplied into the central cold air supply path 15 of 10.

A portion of the cold air, which has just been supplied and still has a high cooling capacity, is passed through the second short pipe 35, the inner chamber 33a, the cylindrical partition wall 34, and the outer chamber 33b in a zigzag manner, and is then passed through the annular outlet 33c into the bubble of the die 13. Cold air is blown from the discharge port 36 toward the inner surface of the extruded bubble W in a molten state to cool the bubble W.

The air whose temperature has risen slightly by cooling the bubble W in this manner rises along the inner surface of the bubble W, and a portion of the air flows into the upper air return chamber 29 through the many small holes of the cylindrical body 28. The air flows through the group 27, is sucked into the rising air passage 21 through the communication hole 30, rises along the rising air passage 21, and blows out into the bubble W from the upper end.

In addition, the remaining cold air rising through the central cold air supply path 15 sequentially passes through the short pipes 26 and each cold air discharge chamber 2.
4, the air is blown out toward the inner surface of the bubble W from the circumferentially slit-shaped cold air discharge groove 25,
After cooling the inner surface, the slightly warmed air rises upward, and this air layer supports the bubble in a state slightly separated from the outer peripheral surface of the bubble internal cooling device 10, while supporting the inner surface of the bubble W. At the same time, a portion of the rising air is passed through the numerous small holes 2 of the cylinder body 28 into each upper air return chamber 29.
After the air flows in from 7, it passes through the communication hole 30 and enters the rising air passage 2.
The air is sequentially drawn into the bubble W, and is blown up into the bubble W from the upper end of the rising air passage 21.

This blown air rises along the inner surface of the bubble W and merges with the air discharged from between the outer circumferential surface of the present bubble internal cooling device 10 and the inner circumferential surface of the bubble W,
The bubble W cooled from the inside by the bubble internal cooling device 10 of the present invention is blown into a desired diameter all at once.

The air that has been blown and expanded in this way is reversed within the bubble W by the suction action of the second blower _P2 , and descends toward the air exhaust passage 18.
Air flows into the air passage 18 from this upper end, and the die 12
The air is exhausted to the outside of the bubble W through the annular exhaust port 17 of the bubble W.

At this time, the ring-shaped mixing prevention plate 31 provided at the upper end of the inner intermediate pipe 16 prevents the air exhaust passage 18
This prevents the air flowing in and the air blowing up from the rising air passage 21 from mixing.

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

The cold air is supplied to each cold air discharge chamber 24 through the inner pipe 11.
Since the structure is such that the cold air rising through the cylindrical cold air supply path 15 formed by the cylindrical cold air supply path 15 is distributed and distributed from the radial direction by a large number of short pipes 26 arranged radially, the short pipes 26 of the same size are Even if used, the same amount of cold air can be distributed and supplied to each of the cold air discharge chambers 24 spaced apart in the axial direction, and with a simplified structure, the same amount of air and the same speed of cold air can be distributed to each of the cold air discharge chambers 24. The cold air can be blown toward the inner surface of the bubble W from the slit-shaped cold air discharge groove 25, and the bubble W can be uniformly cooled from inside in a stable state without vertical or horizontal vibration, and uneven thickness can be prevented.

A part of the air blown out from each slit-shaped cold air blowing groove 25 toward the bubble W and slightly warmed by the cooling of the bubble W rises along the inner surface of the bubble W, passes through the group of small holes 27 of the cylinder body 28, and returns to each air return. Because it flows into the chamber 29, most of the warm air can flow into the air return chamber 29 without increasing its inflow speed at once.
Due to the presence of the air return chamber 29, a large amount of warm air can be guided to the air rising passage 21 through the communication hole 30 while maintaining the pressure inside the air return chamber 29 at approximately atmospheric pressure without making it negative pressure. , the bubble W can be prevented from coming into close contact with the circumferential surface of the cylindrical body 28 at the position of the air return chamber 21, and the bubble W can be kept separated from the outer circumferential surface of the internal cooling device 10 by the cold air rising along the inner surface of the bubble W. Supports internal cooling.

Since the central cold air supply path 15 is formed by the inner pipe 11, a large amount of cold air can be supplied at once from the central cold air outlet 14 of the die 13 to each of the cold air discharge chambers 24 through each short pipe 26. In addition to being able to reduce pressure loss in the system and blowing cold air at a predetermined pressure toward the bubble W, this inner pipe 12
Since it is surrounded by the air exhaust passage 18 and does not come into direct contact with the high-temperature die 13, the degree to which the cold air supplied into the die 13 is warmed is small.

The ring-shaped mixing prevention plate 31 provided at the upper end of the inner intermediate pipe 16 allows the air blown up from the upper end of the rising air passage 21 to mix with the air flowing from inside the bubble W into the air exhaust passage 18 from its upper end. The bubble can be blown to a desired diameter without excessive flow, and the air can be smoothly exhausted to the outside of the bubble W.

<Effects of the Embodiment> Immediately after being extruded from the bubble outlet 36 of the die 12, the entire inner peripheral surface of the bubble W has a cooling capacity from the blowout annular opening 32c formed in the outer blowing chamber 32b near the cylindrical body 32. A portion of high-temperature cold air can be blown, and the bubble W can be internally cooled immediately after extrusion molding, and the air warmed by bubble cooling can be guided upward along the outer peripheral surface of the cylindrical body 32 to return the upper air. Since the bubble W can be guided to the chamber 29 in a stable state and low-temperature air is always sequentially supplied to the inside of the cylindrical body 32, the air flowing on the outer circumferential surface of this part will not flow inside while flowing through this section. The bubble cooling effect can be further enhanced.

If the cylindrical body 28 is formed by forming a pasting plate in which a large number of small holes 27 are formed into a cylindrical body, the manufacture of the cylindrical body 28 becomes simple.

In addition, for convenience of assembly, the mold materials 22 and 23 are
It is divided into two parts.

The position of the circumferentially slit-shaped cold air discharge groove 25 is set relative to the connection position between the short pipe 26 and the cold air discharge chamber 24, that is, the position where the cold air is supplied from the short pipe 26 into the cold air discharge chamber 24, and the bubble W is sent out. In an embodiment in which the cold air is disposed upstream in the axial direction, that is, shifted upward in the axial direction, the pressure of the cold air supplied to the cold air discharge chamber 24 is adjusted in this cold air discharge chamber 24, and the cold air is spread uniformly in the circumferential direction. Afterwards, since the cold air is blown out uniformly from the entire circumference of the discharge groove 25, the cold air is not blown out at an increased speed.
That is, the entire circumference of the bubble W can be uniformly cooled from the inside without vibrating the bubble W.

[Brief explanation of the drawing]

The figures relate to this invention; FIG. 1 is a longitudinal sectional view of a typical embodiment of this invention, FIG. 2 is a cross-sectional view taken in the cold air discharge chamber of FIG. 1, and FIG. , is a vertical cross-sectional view showing a conventional example. Code in the figure: 10...Bubble internal cooling device, 14
...Central cold air outlet, 15...Central cold air supply path,
18... Air exhaust passage, 21... Rising air passage,
24...Air discharge chamber, 25...Air discharge groove, 29
...Air return chamber, 30...Communication hole.

Claims (1)

[Claims for Utility Model Registration] 1. In a bubble internal cooling device for inflation film molding that cools the inner surface of a bubble extruded from a die of an extrusion molding machine from the inside with cold air, the upper end is closed and the lower end is closed off from the die. an inner pipe communicating with the central cold air outlet to form a central cold air supply passage; and a cylindrical air exhaust passage around the inner tube, the upper end of which opens into the bubble and the lower end of which communicates with the annular exhaust port of the die. an inner intermediate tube forming a bubble, and an outer intermediate tube opening into the bubble at its upper end and closed at its lower end by a ring-shaped end plate, forming a cylindrical rising air passage around the inner intermediate tube. They are arranged concentrically on the upper surface, sharing the same axis line, and around the outer intermediate tube, several sets of upper and lower ring-shaped members are fixed adjacently at intervals in the axial direction, and each set is A flat ring-shaped cold air discharge chamber is formed by a pair of upper and lower mold members and the circumferential surface of the outer intermediate pipe. A circumferential slit-shaped cold air discharge groove is formed between the lip pieces and communicates with the cold air discharge chamber, and each cold air discharge chamber and the central cold air supply passage are radially connected to the air exhaust passage and the rising air passage. A tube in which a large number of small holes are drilled flush with the tip surface of the cold air discharge groove between upper and lower adjacent cold air discharge chambers. A cylindrical air return chamber is formed by the cylindrical body, the shaped material arranged at a distance from each other, and the peripheral surface of the outer intermediate tube, and a cylindrical air return chamber is formed between the air return chamber and the rising air passage. The outer intermediate pipe has a large number of communication holes, and the upper end of the inner intermediate pipe has a ring-shaped prevention ring that prevents the air blown up from the rising air passage from mixing with the air flowing into the upper end of the air exhaust passage. A bubble internal cooling device for inflation film molding, characterized in that a plate is attached. 2. A bubble internal cooling device for inflation film molding according to claim 1, wherein the cylindrical body is formed by molding a punching plate having a large number of small holes into a cylindrical body. 3. Utility model registration claim 1, characterized in that the position of the cold air discharge groove is located higher in the axial direction with respect to the connection position between the short pipe and the cold air discharge chamber.
Bubble internal cooling device for inflation film molding as described in Section 3.