JPH018348Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field] This invention relates to a die used when forming a film by an inflation method using an extrusion molding machine.

[Background of the invention and prior art]

In this type of die, the cylindrical outer die is generally called the die body, and the inner die, for example, a spiral mandrel with a spiral groove carved on the outer circumferential surface, is fitted inside the die body, and the space between these two members is cylindrical. The spiral mandrel is further double or triple layered on the inside as necessary, and a cylindrical molten resin path is formed between each spiral mandrel, making it possible to form multilayer inflation films. Generally, an electric heating source is attached to the outer periphery of the outermost die body.

Therefore, when heating the above-mentioned double die (inside and outside), or even more dies, the temperature of the die will be higher as the die is located on the outer side.

Therefore, even if the mounting and fitting parts of each die are precisely machined, not only must tolerances be provided to enable assembly and disassembly, but also the tolerances of the fitting parts must be established due to the heating temperature difference. It is inevitable that the die will become large, and after the die is assembled and heated, the inner and outer dies must be aligned again, and this alignment requires extremely high skill.
If an inexperienced person performs the work, the work will take a long time, and there is a risk that the operating time for film processing will be reduced.Furthermore, if processing is performed with poor alignment, a film with uneven thickness may be processed. Put it away.

〔the purpose〕

Therefore, this idea does not require a high degree of skill, and if you align the inner and outer dies when assembling the dies, there will always be little misalignment between the inner and outer dies even when heated, and alignment work after heating is also extremely easy. This is to enable inflation film processing with extremely little thickness deviation.

〔composition〕

This invention provides a die in which a cylindrical molten resin path is formed between a cylindrical outer die and an inner die fitted inside the die, and in a fitting attachment portion between the outer die and the inner die. One of the inner and outer dies is formed with a tapered surface, and a tapered ring having the same tapered peripheral surface that comes into contact with the tapered surface and whose inner and outer peripheral surfaces fit with the inner and outer dies is interposed. The tapered ring is equipped so that its tapered circumferential surface can be pressed against a die having a tapered circumferential surface in contact with the tapered ring by mechanical pressure means, and the material of the tapered ring is made of a material similar to that of the outer die. This is a centering die that prevents unevenness in thickness, and is characterized by being made of a material having a higher coefficient of thermal expansion than the material of the inner die.

A typical embodiment of this invention will now be described.

[Embodiment 1] As shown in FIG. 1, 10 is a die main body which is an outer die, 11 is an inner die fitted inside this die, and as shown in the figure, a spiral groove 12 is provided on the outer circumferential surface.
A cylindrical molten resin path 13 is formed between these two members, that is, the die body 10 and the spiral mandrel 11, and the downstream end of this path is an annular discharge port 14.

In the fitting attachment portion 15 of the two members, the inner surface of the die body 10, which is one member, is connected to the discharge port 14.
The side has a tapered surface 16 with a narrow diameter, and the fitting attachment portion 15 on the inner spiral mandrel 11 side
The outer peripheral surface is a circular surface 17 having the same diameter over the entire length.

Reference numeral 18 denotes a tapered ring which is brought into contact with the tapered surface 16 and the circular surface 17 on the inside and outside, and this outer circumferential surface is a tapered surface having the same inclination angle as the tapered surface 16. The material for this taper ring is usually a material having a thermal expansion coefficient of about 1.5 to 2 times that of the material of the die body 10 and spiral mandrel 11, such as aluminum bronze alloy, brass, or stainless steel.

Numeral 19 is a tightening bolt for fixing the main body die 10 and the spiral mandrel 11; 20 is a tightening bolt that is screwed onto a part of the spiral mandrel 11 in a direction parallel to this axis, and its tip abuts on the tapered ring 18; Several push screws (usually 3 to 4) are provided at equal intervals.

In addition, reference numeral 21 in the figure represents an electric heating type heating means wound around the outside of the die body 10.

In order to use this embodiment configured as described above, when the die body 10 and the spiral mandrel 11 are at room temperature or at a temperature that is not dangerous for assembly work,
Fit the taper ring 18 to the bolt 5 as shown in FIG. When the setscrews 20 are tightened and the taper ring 18 is pressed, the taper ring 18 will fit into the fitting mounting portion 15 like a wedge.
The tapered surface and die body 1
The axes of the die body 10 and the spiral mandrel 11 are aligned by the tapered surface 16 of zero.

[Effects of Embodiment 1] Next, when the die body 10 and the spiral mandrel 11 are heated by the heating means 21 to a temperature necessary for forming a blown film,
All of these members undergo thermal expansion, and generally the die body 10 is larger than the spiral mandrel 11.
Although the temperature will be slightly higher than that of the taper ring 18, the fitting of the fitting mounting portion 15 will tend to become loose.
has a larger coefficient of thermal expansion than these materials, so due to the heating, it is further pressed against the inner peripheral surface of the tapered surface 16 of the outer die body 10, and the die body 10 and the spiral mandrel 11 due to the thermal expansion are
The tapered ring 18 is restrained on the outside by the die body 10, so its thermal expansion causes internal strain, and the inner diameter of the tapered ring 18 is reduced by heating. The diameter cannot increase, and the inner spiral mandrel 11 also undergoes thermal expansion, so there is almost no difference in the fit between the taper ring 18 and the spiral mandrel 11 even when heated, compared to when it is at room temperature. The cores of the main body 10 and the spiral mandrel 11 are maintained in a matched state.

In addition, the temporary taper ring 18 and the die body 10
Also, even if the fitting portion of the spiral mandrel 11 becomes slightly loose, the press screw 2 serving as the pressure means
Centering can be easily achieved by tightening the 0 again. In this case, it goes without saying that a wrench with a torque limiter is used to keep the tightening force of the set screw 20 constant.

In addition, when disassembling and reassembling the die body 10 and spiral mandrel 11 after discontinuing inflation film forming, the temperature of the outer die may be about 100°C higher than that of the inner die.
If the outer die is heated to facilitate mating assembly, the mating tolerances will increase, respectively;
The alignment state before disassembly may change significantly, but even in such a case, in this embodiment, after assembling the die body 10 and spiral mandrel 11, the set screw 20 can be tightened. It is easy to align the center.

[Embodiment 2] This is shown in FIG. 2, where the same reference numerals as in Embodiment 1 are the same constituent members and have the same functions and effects.

The difference is that in the fitting attachment part 15, the inner peripheral surface 17a of the die body 10 has the same diameter over the entire length, whereas the spiral mandrel 11 has the same diameter.
The fitting attachment part 15 has a tapered surface 16a whose diameter is narrower closer to the discharge port 14, and the tapered ring 1
8a has an inner peripheral surface formed into a tapered surface having the same slope as the tapered surface 16a. The tips of several drawing screws 20a serving as pressurizing means are respectively screwed into the tapered ring 18a, and are respectively inserted into screw holes 22 provided in the spiral mandrel 11.

When assembling the second embodiment, first, the tapered surface of the spiral mandrel 11 is
Fit the taper ring 18a at 6a,
Each draw screw 20a is passed through the screw hole 22 and screwed into the tapered ring 18a. After fitting the die body 10 and the spiral mandrel 11 and tightening the tightening bolts 19 in the same manner as in the first embodiment, tighten the several draw screws 20a to align the tapered ring 18a with the tapered surface 16a. The die body 10 and the spiral mandrel 11 are centered by pressing them together.

[Effects of Embodiment 2] When the heating means 21 is used to heat the die body 10 and the spiral mandrel 11 to the inflation film processing temperature, the effect of Embodiment 1 is achieved.
Similarly, since the expansion line of the tapered ring 18a is larger than the expansion line of the die body 10, there is no gap between them, and since the tapered ring 18 is fixed by the draw screw 20a, the expansion line of the tapered ring 18a is larger than the expansion line of the die body 10. There is no leakage, the inner diameter hardly changes, and the state of fitting with the tapered surface 16a of the inner spiral mandrel 11 hardly changes from before heating, maintaining a good centering state. Furthermore, even if there is loosening between the temporary tapered ring 18a and the tapered surface 16a,
By tightening the several drawing screws 20a, which are the pressure means, again with a wrench equipped with a torque limiter, the gap is eliminated, and alignment can be easily performed by the tapered surface 16a and the tapered ring 18a.

[Effects of this invention]

As constructed as described above, and as described in each embodiment, the core of this invention remains intact even when assembled at room temperature and then heated to the temperature required for inflation film molding. There is almost no misalignment, and even if there is some loosening in the fitted state, accurate alignment can be achieved by simply re-tightening the push screw 20 or pull screw 20a, which is the pressure means. In addition, even when only the outer die is heated significantly and the fit tolerance of the mating part becomes large, alignment can be done easily and accurately.
The operating efficiency of the device is improved by shortening assembly and disassembly work time, and it is possible to consistently form films with less uneven thickness.

In addition, since the tapered ring 18 is interposed in the fitting part 15, even if the tapered ring 18 is damaged due to a collision between the outer die and the inner die and the tapered ring 18, which inevitably occurs during assembly and disassembly, this taper ring 18 It is only necessary to replace the ring 18 with a new one, and even without increasing the fitting accuracy of the fitting part 15 of the inner and outer dies, sufficient fitting accuracy can be maintained by the sliding process with the tapered ring 18, and the die The processing cost can be reduced.

Other taper rings 18 are aluminum bronze alloy,
When a material softer than the inner and outer dies 10 and 11, such as brass or stainless steel, is used, most of the wear and tear due to assembly and disassembly or fatigue over time occurs only on this tapered ring 18 side, which must be replaced with a new one. Then, a good fit can be achieved again.

If the coefficient of thermal expansion of the taper ring 18 is about 1.5 to 2 times that of the inner and outer dies, the internal strain due to heating will not become too large, and there is no risk of deforming the taper ring 18 or the die.
In addition, a suitable binding force can be obtained.

If the taper ring 18 has an inclination of 20° to 70°, preferably 25° to 45°, it will be possible to obtain appropriate restraint, and the movement dimension by the push screw 20 and draw screw 20a will not become large, and assembly and disassembly work will be easy. .

In the embodiment described above, the cylindrical molten resin path 13 is single, but in the case of a multiple cylindrical molten resin path 13, this tapered ring 18 is attached to the fitting attachment part of each die that is fitted sequentially inside and outside. The invention is the same whether it is used for a part of the fitting attachment part or for a part of the fitting attachment part. Furthermore, the spiral groove 12 is not necessarily required on the circumferential surface of the inner die.

In addition, this invention is the same even if the fitting attachment portion 15 with the tapered ring 18 interposed has a fitting shape in which the outer die 10 is located on the inside and the inner die 11 is located on the outside.

[Brief explanation of the drawing]

The drawings show things related to this invention, and FIG. 1 is a longitudinal sectional front view of the first embodiment, and FIG. 2 is a longitudinal sectional front view of the second embodiment. In the figure, 10...outer die, 11...inner die,
15... Fitting mounting part, 18... Taper ring,
20...Push screw.

Claims (1)

[Claims for Utility Model Registration] 1. A die in which a cylindrical molten resin path is formed between a cylindrical outer die and an inner die fitted inside the die, wherein the outer die and the inner die In the fitting attachment part, one of the inner and outer dies is formed into a tapered surface, and has the same tapered circumferential surface that comes into contact with the tapered surface, and the inner and outer circumferential surfaces are fitted with the inner and outer dies. A tapered ring is interposed therebetween, and the tapered ring is equipped so that its tapered circumferential surface can be pressed against a die having a tapered circumferential surface in contact with the tapered ring by mechanical pressure means. The centering die for preventing thickness deviation is characterized in that the material of the outer die and the inner die are made of a material having a higher coefficient of thermal expansion than the materials of the outer die and the inner die. 2. Claim 1 of the utility model, characterized in that the thermal expansion coefficient of the tapered ring is about 1.5 to 2 times that of the outer die and the inner die.
Centering die to prevent uneven thickness as described in section. 3. The centering die for preventing thickness deviation according to claim 1, wherein the angle of the tapered surface with respect to the axis is from 20° to 70°, preferably from 25° to 45°.