JPH02116531A - Extruder die for tubular body - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a mold for extruding a tubular body.

(Prior Art) In a conventional extrusion mold for a tubular body, an inner mold is generally fixed inside an outer mold with a spider, and an annular resin flow path is formed between the outer peripheral surface of the inner mold and the inner peripheral surface of the outer mold. is formed. The mold is attached to the tip of the barrel of the extruder and rectifies and shapes the molten resin extruded from the extruder into an annular shape in a resin flow path to form a tubular body. However, because the inner mold is fixed to the outer mold and the width of the resin flow path is determined, it is difficult to mold tubular bodies with different wall thicknesses and outer diameters.
It was necessary to replace the mold attached to the extruder. Therefore, it takes time to replace the mold, and extrusion of the resin must be stopped each time the mold is replaced, resulting in material loss.

In addition, as described in Japanese Patent Publication No. 58-1654, the inner peripheral surface of the outer mold forming the outer periphery of the resin flow path is formed into a conical surface whose diameter decreases in the extrusion direction, and a part of the inner mold is A movable part that can move forward and backward with respect to the outer mold is used, and the interval between the exits of the resin flow path can be adjusted depending on the position of this movable part, so that tubular bodies with different wall thicknesses can be molded with one mold. Things are also known.

Furthermore, as described in Japanese Patent Application Laid-Open No. 61-163825, a large diameter portion and a small diameter portion are formed on the outer peripheral surface of the inner mold that forms the inner periphery of the resin flow path, and the outer mold is moved forward. It is also known that a tubular body having the same outer diameter and different wall thickness can be molded with one mold by adjusting the interval between the exits of the resin flow path depending on the position of the outer mold. There is.

(Problem to be solved by the invention) However, the above-mentioned Japanese Patent Publications Nos. 58-1654 and 61
Although it is possible to mold tubular bodies with different wall thicknesses using a single mold for extrusion molding of tubular bodies such as No. 163825, when molding tubular bodies with different outer diameters, Since the mold needs to be replaced, there is a problem in that the above-mentioned time loss and material loss are unavoidable.

The present invention focuses on the above-mentioned problems, and with one mold,
The objective is to develop an extrusion mold that can mold two or more types of tubular bodies with different outer diameters and wall thicknesses. The object of the present invention is to solve this problem and provide a mold for extruding a tubular body that reduces time loss and material loss.

(Means for Solving the Problems) In order to solve the above problems and achieve the above objects, the mold for extruding a tubular body of the present invention has an inner mold fixed inside the outer mold by a spider, In a mold for extruding a tubular body in which an annular resin flow path is formed between the outer peripheral surface of the inner mold and the inner peripheral surface of the outer mold, the portion of the resin flow path from the spider to the outlet is formed in the extrusion direction. It is formed by a restrictor part parallel to the extrusion direction, a diameter reducing part whose diameter is reduced in the extrusion direction, and a parallel part near the exit parallel to the extrusion direction, and the ratio of the length of the restrictor part to the gap width (2□/ 2) is larger than the ratio (ε1/11) of the length of the parallel portion near the exit to the gap width (ε1/11).

(Function) The mold for extruding a tubular body of the present invention is attached to the tip of the barrel of an extruder. Then, the molten resin extruded from the extruder is rectified and shaped into an annular shape in a resin flow path, and extruded as a parison from the outlet of the resin flow path. Note that the extruded parison is guided to a forming device and shaped into a predetermined outer diameter or inner diameter.

When the molten resin passes through the resin flow path, it is subjected to the memory effect of elastic deformation in the spike part and the restrictor part,
The memory of elastic deformation is alleviated in the parallel portion near the exit.

If the memory relaxation of elastic deformation in the parallel portion near the exit is not sufficient, a balancing effect appears in which the parison extruded from the resin flow path expands in the radial direction.

In conventional molds, the parallel part near the exit was formed long in order to sufficiently alleviate the memory of elastic deformation, and the mold was configured to prevent the ballast effect as much as possible, but in the mold of the present invention, the restrictor I22/12 of the portion is made larger than β, /l of the parallel portion near the exit, so that the balance effect is enhanced. That is, in the mold of the present invention, the back pressure that is reduced due to the shortening of the parallel part near the exit is
The back pressure of the mold does not decrease because it is compensated by the restrictor part. For this reason, sufficient crosstalk occurs, and the separation surfaces are sufficiently refused by the spider, resulting in a higher expansion rate of the parison than in the past. Therefore, when forming the forming device C parison, the outer diameter can be freely set within a wide range in which the parison expands. It becomes possible to mold the body.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, the configuration of the embodiment shown in FIGS. 1 and 2 will be explained.

In the mold A for extrusion molding a tubular body of this embodiment, an inner mold 2 is fixed inside an outer mold 1, and an annular resin flow path 3 is formed between the outer peripheral surface of the inner mold 2 and the inner peripheral surface of the outer mold 1. is formed.

The outer mold 1 includes an outer cylindrical portion 41 of the goo body 4 and the outer cylindrical portion 4.
1 and a gui ring 12. Further, the inner mold 2 is composed of an inner cylinder part 42 of the goo body 4 and a mandrel 2I fixed to the inner cylinder part 42, and the inner mold 2 is formed at multiple locations above and below the goo body 4. The outer mold 1 is created by the spider 43
Fixed.

The gouia adapter 11 is a part for connecting the goo body 4 and the barrel tip of the extruder B, and the flange part 111 formed at one end of the gou body 4 is connected to the port 11.
It is fixed at 2.

The gouilling 12 is a part that forms the space between the spider 43 and the outlet of the resin flow path 3 together with the mandrel 21, and the flange portion 121 formed at one end is connected to the bolt 122 with respect to the gou body 4, similar to the gouia adapter 11. is fixed.

In addition, in the resin flow path 3, a portion between the spider 43 and the outlet formed by the inner circumferential surface of the Guiling 12 and the outer circumferential surface of the mandrel 21 has a restrictor portion 31 parallel to the extrusion direction, and a restrictor portion 31 parallel to the extrusion direction. Reduced diameter part 3 that reduces in diameter in the direction
2, and a parallel portion 33 near the exit parallel to the extrusion direction.

Note that the average diameter and wall thickness of the spider 43 are larger than the average diameter and gap width of the restrictor portion 31 and the average diameter and gap width of the outlet vicinity parallel portion 33. Also,
The gap width of the reduced diameter portion 32 is formed to be larger than the gap width of the restrictor portion 31 and the outlet vicinity parallel portion 33.

Further, 122/t 2 of the restrictor section 31
2 of the parallel portion 33 near the exit. /β1.

The length I22 and gap width t2 of the restrictor portion 31 and the length 2 of the parallel portion 33 near the outlet. And the gap width t1 is set by the dimensional ratio of the spider 43 and the outlet vicinity parallel part 31. For example, the length I21 and the gap width t1 of the parallel part 33 near the exit are such that a/1+ is 20 or less, preferably 5 to
It is desirable to set it to 15. In addition, the length Q2 and the gap width t2 of the restrictor part 31 are calculated using the approximate formula % formula for back pressure calculation in the case of a vinyl chloride resin pipe. P: Back pressure Q: Extrusion amount L: Length D: Diameter t: Using the wall thickness, D and t are designed so that the sum of the back pressure of the parallel part 33 near the outlet and the back pressure of the restrictor part 31 is almost equal to the sum of the back pressure of the normal mold, but ρ2/ 12 is 20-5
It is desirable to set it to 0.

A tension bar 22 is inserted through the center of the mandrel 21 in the extrusion direction, and the mandrel 21 is fixed to the goo body 4 by this tension bar 22.

Next, the operation of the embodiment will be explained.

Mold A is attached to the tip of the barrel of extruder B.

Then, the molten resin extruded from the extruder B into the resin flow path 3 is rectified and shaped, and the parison C is extruded from the outlet of the resin flow path 3. Note that the extruded parison C is guided into a forming device, cooled, and shaped into a predetermined outer diameter. The product is then completed as a molded product.

To explain in more detail, the molten resin that has flowed from the extruder B into the resin flow path 3 of the mold A spreads throughout the resin flow path 3 while spreading in an annular shape. After that, the molten resin is transferred to Spider 4
3, the annular shape is broken and the ring is separated, but since the restrictor part 31 has a sufficient length in the extrusion direction, high internal pressure and shear force are generated when passing through the restrictor part 31. It then returns to its ring shape. That is, the parison C that has further passed through the reduced diameter part 32 and the parallel part 33 near the outlet, has been rectified and extruded, has no trace of having passed through the spikes 43.

Further, when the molten resin passes through the resin flow path 3, it is subjected to the memory effect of elastic deformation in the spider 43 and the restrictor part 31, and the memory of elastic deformation is relaxed in the parallel part 33 near the exit. However, in the mold A of this embodiment, the spikes 43 and the restrictor part 3
Compared to the memory effect of elastic deformation in 1, the memory relaxation effect of elastic deformation in the parallel portion 33 near the exit is extremely weak, so the ballast effect appears extremely strong. That is, the expansion rate of the parison C is much higher than that of the conventional one.

Therefore, when forming the parison C using a forming device, the outer diameter can be freely set within a wide range in which the parison C expands. A tubular body can be formed.

In addition, D in Fig. 2 shows the forming device, and the dotted line indicates the position when forming a small-diameter tubular body, and the dashed-dotted line indicates the position when forming a large-diameter tubular body. It shows. That is, when molding a tubular body with a small diameter size, a forminking device for small diameter size is prepared, and the population of the forming device and the outlet of the resin flow path 3 of the mold A are placed close to each other, so that the balance effect can still be achieved. The parison C immediately after being extruded from the resin flow path 3 in which the resin has not fully appeared is led to a forming device, where it is cooled and shaped. In addition, when molding a large-diameter tubular body, a forming device for large-diameter sizes is prepared, and the inlet of the forming device and the outlet of the resin flow path 3 of mold A are separated from each other, and the balance is The parison C, which has expanded sufficiently due to the effect, is led to a forming device, where it is cooled and shaped.

As mentioned above, in the mold A of this embodiment, two or more types of tubular bodies with different outer diameters can be molded with one mold, so that time loss and material loss can be reduced. Can be done.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention may be modified without departing from the gist of the present invention. included.

For example, by using a foaming device with a small diameter,
Therefore, it is also possible to shape and mold the parison into a tubular body having a smaller diameter than the outlet of the resin flow path.

(Effects of the Invention) As explained above, in the mold for extruding a tubular body of the present invention, two or more types of tubular bodies having different outer diameters can be molded with one mold. It is possible to reduce time loss due to mold exchange and material loss due to scrap generation.

In addition, in the mold of the present invention, two parts of the restrictor part
□/lz is β1/l of the parallel part near the exit.

In other words, compared to conventional molds, the restrictor part is quite long, and the parallel part near the exit is quite short, so the back pressure that is insufficient due to the shortening of the parallel part near the exit is This means that there is no shortage of crosstalk, and the separation surfaces are sufficiently refused by the spider, making it possible to obtain a product without any quality problems.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing a mold for extruding a tubular body according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a main part showing the usage state of the mold according to the example. 33...Parallel part near the exit 43...Spider patent application Sekisui Chemical Co., Ltd. Representative Hiroshi 1) Kaoru A...Mold 1...Outer mold 2...Inner mold 3...・Resin flow path 31...Restrictor part 32...Reduced diameter part FIG. 1A...Mold 1...Outer mold 2...-Inner mold 3...Resin flow path 31...Restrictor Part 32... Reduced diameter part 33... Parallel part near the exit 43... Spider

Claims (1)

[Claims] 1) A mold for extruding a tubular body in which an inner mold is fixed inside the outer mold by a spider, and an annular resin flow path is formed between the outer peripheral surface of the inner mold and the inner peripheral surface of the outer mold. A portion of the resin flow path from the spider to the outlet is formed by a restrictor portion parallel to the extrusion direction, a diameter-reduced portion whose diameter is reduced in the extrusion direction, and a parallel portion near the outlet parallel to the extrusion direction, and Ratio of restrictor length to gap width (l_2/t_2
) is the ratio of the length of the parallel part near the outlet to the gap width (l_1
/t_1) A mold for extruding a tubular body.