JPH0536661Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention relates to an inflation film molding device, and is particularly concerned with a resin annular discharge port of a molding die that blows cold air into the inside of a bubble to cool the inside. The present invention relates to a mounting structure for an internal heating device.

(Prior art and problems) In recent years, thick films (≒150 to 200 microns) of low-density polyethylene have been used to make rice bags and fertilizer bags. Therefore, an internal cooling device installed in a duct or bubble to blow cooling air inside the annular resin discharge port is essential. Because of the duct, the heat inside the resin path in the die is radiated to this duct, causing a drop in the temperature of the molten resin, so it is necessary to supply heat to the inside of the resin path in the molding die.

Therefore, in conventional molding dies of this type with an annular discharge opening of 250 mm or more,
A belt-shaped electric heating zone 1 extending in the inner circumferential direction is formed into a ring shape, and the diameter of the ring-shaped heating zone 1 can be expanded by using a mounting screw 2 having an axis in the circumferential direction. This is attached to the inner peripheral surface of an internal annular die that forms the inner lip of the annular discharge port (see Fig. 6).

However, since the axis of the mounting screw 2 is located in the circumferential direction within the internal annular die, this screw 2
A space is required to engage and rotate a tightening tool such as a box spanner or other wrench in order to rotate the annular outlet around its axis, and this space is insufficient if the annular outlet has a diameter of 250 mm or less. Therefore, conventionally, this internal heating device has not been installed at all in devices with a diameter of 250 mm or less.

Furthermore, even if the die has a diameter of 250 mm or more, the installation space is still narrow.
Installing the heating device was quite troublesome and required skill.

(Problems to be Solved) This invention is based on an inflation film molding die in which a bubble internal cooling duct or an internal cooling device connected thereto is installed, and an internal heating device installed inside a resin annular discharge port is connected to the annular resin discharge port. To enable it to be easily attached regardless of the diameter, especially to something with a small diameter, and to be able to firmly press against the inner circumferential surface of an internal annular die,
The purpose is to provide the market with a device that satisfies these problems.

(Means for Solving the Problems) This invention consists of a hollow interior for attaching an internal cooling device extending into a bubble inside the internal annular die constituting the inner wall of the resin annular discharge port in a die for molding a blown film. In the device provided with a cooling device support member, the inner circumferential surface of the inner annular die and the outer circumferential surface of the support member are concentric with the annular discharge port, and the gap between the inner annular die and the support member is It has a shape in which the radial dimension becomes narrower toward the inside from the outer end surface that is almost flush with the outlet, and a band-shaped electric heating zone extending in the circumferential direction in the gap, and a band-shaped electric heating zone located inside the electric heating zone. A cylindrical wedge member having a slightly variable shape is inserted, and the cylindrical wedge member is press-fitted into the gap from its outer end surface by an axial tightening screw, and the electric heating zone The problem was solved by providing an inflation film forming apparatus characterized in that the outer circumferential surface is pressed against the inner circumferential surface of the inner annular die.

(Effects) In this device constructed as described above, the tightening screw tightens the cylindrical wedge member in the axial direction of the die and from almost flush with the annular discharge port, so a wrench is not required. It is easy to use a wrench or a wrench.
Since these operating handles can be operated at a location away from the die, even if the gap for inserting the temporary heating band or cylindrical wedge member is narrow, tightening and replacement work can be done easily and reliably. Since the wedge member is made of a material that has a slightly variable formability, its outer diameter changes when it is press-fitted into the gap by the tightening screw, and an electric heating type is formed between this wedge member and the inner circumferential surface of the inner annular die. After firmly holding the heating zone and attaching it, the electric heating zone in the circumferential direction is brought into close contact with the inner peripheral surface of the internal annular die by the cylindrical wedge member, and the heat is effectively transferred to the annular discharge opening. conducted to the resin.

As a result, the heating of this heating zone effectively prevents the resin melting temperature from decreasing due to heat dissipation to the cooling air duct, and the resin melting temperature can be maintained at a predetermined molding temperature, allowing the film to be inflation-molded to a predetermined diameter. can.

(Embodiment) This invention will now be specifically explained based on a representative embodiment shown in the drawings.

In FIG. 1, reference numeral 10 denotes a die for forming a blown film, and an inner circumferential surface 13a of an internal annular die 13 forming a part of the forming die 10 forms a lip 12 inside the annular discharge port 11. are formed to have the same diameter in the axial direction. A duct 15 for cooling the inside of the bubble is provided in the center of the molding die 10, and the inner annular die 13
A hollow internal cooling device support member 17 is fixed to the molding die 10 with a slight gap 16 inside thereof and concentric therewith. The radial dimension of the gap 16 is formed to be narrower toward the back of the gap 16, that is, toward the upstream side with respect to the resin flow at the annular discharge port 11 portion. In other words, a tapered portion 18 is formed in which the outer diameter of the hollow cooling device support member 17 increases toward the upstream side.

Reference numeral 19 denotes a wedge member having a generally cylindrical shape that is press-fitted into the gap together with the electric heating zone 1, which has a split 20 in the axial direction, an outer circumferential surface 21 of which is cylindrical or gutter-shaped, and an inner circumferential surface. is an inner circumferential tapered portion 22 that matches the tapered portion 18, and several tightening screw holes 23 are bored in the axial direction, and even if the cylindrical wedge member 19 is a single component, Even if it can be divided into several pieces as shown in FIG. 4, the invention is the same.

When the cylindrical wedge member 19 is made of a material having a slightly variable shape, such as glass fiber, asbestos, or a heat-resistant synthetic resin molded product, the split 20 is not necessarily required.

When the cylindrical wedge member 19 is made of a fragile material such as ceramic or stone, the above-mentioned split 20 is provided so that the wedge member 19 can be made into several split members, making it somewhat variable.

Reference numeral 24 denotes a tightening screw that passes through each of the tightening screw through holes 23 of the cylindrical wedge member 19 and is screwed into a part of the molding die 10.

The electrothermal heating zone 1 includes the inner annular die 13
It has a length that approximately corresponds to the inner circumference length of.

(Embodiment - How to Use) In this embodiment configured as described above, if the cylindrical wedge member 19 is a single member (see Fig. 3), the circumference of this outer peripheral surface 21 The cylindrical wedge member 19 is inserted into the gap 16 between the inner annular die 13 and the cooling device support member 17 so that the inner peripheral tapered portion 22 is connected to the tapered portion of the support member 17. When the cylindrical wedge member 19 is inserted so as to match the slope of the cylindrical wedge member 18, and then the several tightening screws 24 are passed through the screw through holes 23 and tightened against the forming die 10, the cylindrical wedge member 19 is slightly bent. The tapered portion 18 of the support member 17 has deformability.
The heating zone 1 on the outside is pressed and fixed to the inner circumferential surface of the inner annular die 13 by being guided by the inner annular die 13 and its outer diameter expands.

When the cylindrical wedge member 19 is divided into several parts as shown in FIG.
It is inserted into the gap 16 in the same manner as in the previous embodiment, and is press-fitted into the gap 16 by the tightening screw 24. In this case, the gaps 20 are between the individual wedge members 19 that are flared toward the end.

The cylindrical wedge member 19 may be press-fitted into the gap 16 by tightening with the tightening screw 24 passing through the cylindrical wedge member 19 in the axial direction as in the above-mentioned example.
This invention is the same even if it is a set screw 24a as shown in the figure.

The reference numeral 25 designates a donut-shaped guide plate for internal cooling air guidance and heat reflection, which is attached to the inside of the upper bubble after the electrothermal heating zone 1 and the cylindrical wedge member 19 are attached.

(Effects Unique to Embodiments) Each embodiment has the same effects as this invention, and in the case where the cylindrical wedge member 19 is made of a heat insulating material, the electric heating zone 1 is provided on the cylindrical wedge member 19 side. Heat is effectively transferred to the resin at the annular discharge port 11 via the internal annular die 13 without much heat escaping. Therefore, at the same time, heating of the cold air supplied into the internal cooling duct due to the heat radiation of the electric heating zone 1 can be minimized. becomes more prominent.

In addition, in an embodiment in which the cylindrical wedge member 19 is made of a deformable material such as glass fiber or asbestos, it can be formed seamlessly around the entire circumference, so that the electric heating zone 1 can be uniformly attached to the inner annular die 1 over the entire circumference.
Can be pressed against the inner peripheral surface of No.3. Furthermore, the structure is simple, and the installation and replacement work of the electric heating zone 1 is easy.

In addition, in the case where at least one slit 20 is provided in the axial direction to make it variable, the cylindrical wedge member 19 can be made of a weak material such as ceramic or stone.

The tightening screw is a set screw 24a as shown in FIG.
In this embodiment, even if the cylindrical wedge member 19 is thin and does not have a screw hole, it can be press-fitted, and even a resin annular discharge port 11 with a small diameter can be equipped.

[Brief explanation of drawings]

The drawings show what is related to this invention.
Fig. 1 is a half-cut vertical front view of a typical embodiment of this invention, Fig. 2 is a half-cut vertical front view with the cylindrical wedge member removed, and Fig. 3 is a partially vertical perspective view of the cylindrical wedge member. , FIG. 4 is a plan view of another embodiment of the cylindrical wedge member, FIG. 5 is a half-cut vertical front view showing another embodiment of the press-fit structure of the cylindrical wedge member, and FIG. 6 is a conventional electric heating zone. FIG. Main symbols in the diagram: 1...Electric heating zone, 10...
... Molding die, 11 ... Annular discharge port, 13 ... Internal annular die, 17 ... Internal cooling device support member, 1
8... Tapered portion, 19... Cylindrical wedge member, 24
...Tightening screw.

Claims (1)

[Claims for Utility Model Registration] 1) A hollow internal cooling device support for mounting an internal cooling device extending into a bubble inside an internal annular die constituting the inner wall of a resin annular discharge port in a die for molding a blown film. The inner circumferential surface of the inner annular die and the outer circumferential surface of the supporting member are concentric with the annular outlet, and a gap between the inner annular die and the supporting member is formed with the annular outlet. It has a shape in which the radial dimension becomes narrower toward the inside from the almost flush outer end surface, and there is a band-shaped electric heating zone extending in the circumferential direction in the gap, and a slight electric heating zone located inside the electric heating zone. A cylindrical wedge member having a variable shape is inserted, and the cylindrical wedge member is press-fitted into the gap from its outer end surface by an axial tightening screw, and the outer peripheral surface of the electric heating zone is pressed into the gap. is pressed against the inner circumferential surface of the inner annular die. 2) The cylindrical wedge member is made of one type of a single cylindrical body or a divided cylindrical body consisting of several gutter-like bodies whose circumference is divided into several pieces. Inflation film forming apparatus according to scope 1). 3) The blown film forming apparatus according to item 1 of the utility model registration, wherein the cylindrical wedge member is made of a slightly deformable heat insulating material such as glass fiber, asbestos, or heat-resistant synthetic resin. 4) The variable nature of the cylindrical wedge member is defined by forming a split in at least one location in the axial direction.
2. Inflation film forming apparatus as described in Section 1.