JPH0550495A - Blow molding machine - Google Patents

Abstract

PURPOSE:To facilitate the passage of a large caliber parison and to prevent the thickness deviation of a product in a blow molding machine passing the parison through a closed mold. CONSTITUTION:Movable cores 19, 20 capable of changing the diameter or interval of the parison passage 17 in closed molds 15, 16 to expand the cross-sectional area of said passage are provided to the throttled part 18 having a small cross section of the parison passage 17 and a parison 14 is passed through the parison passage 17. In this case, the movable cores 19, 20 are retracted to expand the throttled part 18 to facilitate the passage of the large caliber parison regardless of the shape of a product. In blow molding after the passage of the parison 14 through the molds 15, 16, the movable cores 19, 20 are set to a product shape position to perform blow molding and the deviation of wall thickness is prevented by the reduction of a blow-up ratio due to the use of the large caliber parison regardless of the size of the throttled part in the molds and the range of a product shape susceptible to blow molding is expanded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a blow molding device for blow molding a parison in a closed mold, which facilitates passage of the parison mold and uses a large diameter parison to prevent uneven thickness. This is something that can be prevented.

[0002]

2. Description of the Related Art There are various methods for blow molding, which is one of the synthetic resin processing techniques. For example, a three-dimensional molded product is formed in which a plurality of cross-sectional shapes are combined and the bent state is not flat. As a method of doing so, unlike the ordinary blow molding, as shown in FIG. 2, the pair of left and right dies 1 and 2 are previously closed, and the parison head 4 sends the parison 5 into the closed passage 3 of the product shape. Then, there is a method in which a gas is blown into the parison 5 passed through the closed passages 3 of the molds 1 and 2 to pass the gas while vacuum suction, and blow molding is performed.

According to the blow molding method in which the molds 1 and 2 are closed at different closing times, the parison 5 having a three-dimensional shape close to the final product can be passed through the molds 1 and 2, and the three-dimensional shape can be obtained. Can be molded without burrs, there is no waste of resin,
The parison 5 has features such as being difficult to be scratched by passing it through the air flow.

[0004]

However, in this blow molding method, the parison 5 is preliminarily closed with the molds 1 and 2 closed.
The diameter of the parison 5 must be smaller than that of the narrowest narrowed portion 6 of the three-dimensionally shaped product in order to pass through. For this reason, parison 5 should be
When gas is blown after it has been passed through, the blow-up ratio is different between the large diameter portion and the small diameter portion of the product, and uneven thickness is likely to occur, and the product shape is naturally limited.

The present invention has been made in view of the above problems of the prior art, and the size of the parison is not restricted by the narrowed portion in the mold that is clamped, and blow molding is performed through the parison having a large diameter. Thus, it is intended to provide a blow molding device which prevents uneven thickness and has less restrictions on the product shape.

[0006]

In order to solve the problems of the above-mentioned prior art, the blow molding apparatus of the present invention vacuum-sucks while delivering the parison into the mold that has been clamped,
In a blow molding device that blows a gas into a parison passed through a mold to obtain a blow-molded product having a predetermined shape, it is possible to expand a passage cross-sectional area to a mold portion that is a narrowing portion of a parison passage in the mold. It is characterized in that a movable core is provided.

[0007]

According to this blow molding apparatus, the diameter of the passage and the interval of the passage can be changed in the narrowed portion of the parison passage in the clamped die to reduce the cross-sectional area of the passage. The core is provided, and when the parison is passed through the parison passage in the mold, the movable core is retracted to increase the diameter of the throttle portion. On the other hand, when the parison is blow molded after passing through the parison passage in the mold, the movable core is moved to a position that matches the shape of the product and blow molded.

By doing so, a parison having a large diameter can be used regardless of the size of the narrowed portion of the parison passage in the mold, uneven thickness of the product can be prevented, and a three-dimensional shape or the like can be formed. There are also fewer restrictions on product shape.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a vertical cross-sectional view of a mold portion according to an embodiment of the blow molding apparatus of the present invention. In this blow molding device 10, the parison 14 delivered from the annular gap between the die 12 and the head core 13 of the parison head 11.
Is designed so that a pair of left and right molds 15, 16 are closed in advance by a mold clamping device (not shown), and the parison passage 17 formed in the molds 15, 16 is passed through. A cap (not shown) is provided below the members 15 and 16 so that the parison 14 can be smoothly passed through by using a flow of air by vacuum suction. In these dies 15 and 16, it is necessary to form a narrowed portion 18 having a small cross-sectional area in the parison passage 17 depending on the shape of the product (blow molded product). Must be passed through with a smaller diameter.

Therefore, the mold 15 corresponding to the narrowing portion 18,
A recess 1 for mounting a pair of movable cores 19 and 20 on 16 parts
5a and 16a are formed and movable cores 19 and 20 are attached, and the passage cross-sectional area is enlarged with respect to the parison passage 17 of the molds 15 and 16 to facilitate passage of the large diameter parison 14, Alternatively, it can be reciprocated so that it can be reduced to the molded state of the product. Piston rods 15c and 16c of pistons mounted in cylinder chambers 15b and 16b formed in the dies 15 and 16 are connected to the backs of the movable cores 19 and 20, respectively, and a working fluid supply (not shown) is provided. By supplying and discharging the working fluid from the exhaust source to the cylinder chambers 15b and 16b via the control valves 21 and 22, the positions of the movable cores 19 and 20 can be changed.

The moving amounts of the movable cores 19 and 20 are determined so that the diameter D of the normal portion of the parison passage 17 formed in the molds 15 and 16 can be secured in the throttle portion 18, and the respective movable portions are movable. Not only when the cores 19 and 20 are moved by the same strokes S1 and S2, for example,
As shown in FIG. 1, the stroke of one movable core 19 is increased by S1 and the stroke of the other movable core 20 is increased by S1.
The strokes S1 and S2 may be changed by reducing 2, for example.

The number of movable cores 19 and 20 installed is
In the case of the embodiment shown in FIG. 1, since the parison passage 17 formed in the molds 15 and 16 has only one throttle portion 18 and the other portions than the throttle portion 18 have the normal diameter D, A pair of movable cores 19 are provided only in the narrowed portion 18 having a small diameter d.
20 is arranged, but when the cross-sectional area of the parison passage 17 changes in a plurality of steps, the parison passage 1
It is possible to arrange a pair of movable cores at a plurality of positions other than the maximum diameter D of 7 to facilitate passage of the parison 14. Further, the shape of the narrowed portion 18 is not limited to the circular cross section, but in the case of an elliptical cross section or a rectangular cross section,
It may be arranged such that the passage cross-sectional area can be enlarged for any cross-sectional shape by, for example, enlarging the portion with a narrow interval.

Blow molding of a product having a three-dimensional shape by the blow molding apparatus 10 having the above-described structure is performed as follows. The three-dimensional shape product as an example of the molding target here is formed by continuously connecting different cross-sectional shapes such as a plurality of circles and flats, and has a narrowed portion having a small cross-sectional area in at least one place, In addition, the central axis of the product is not only on a plane but also three-dimensionally bent, for example, an intake duct of an automobile engine is an example.

First, a pair of molds 1 is formed prior to blow molding.
5 and 16 are closed, and the movable cores 19 and 20 located in the throttle portion 18 are connected to the cylinder chambers 15b and 16
The working fluid of b is discharged through the control valves 21 and 22 to be retracted.

Then, the diameter of the parison passage 17 of the narrowed portion 18 is increased from the narrowed diameter d to D which is equal to the diameter of the other parts of the parison passage 17, and the passage cross-sectional area is also enlarged.

In this state, the parison 14 is pushed out from the parison head 11 and has a diameter that forms a predetermined gap with the diameter D of the parison passage 17, and vacuum suction is performed through a cap (not shown) mounted below the dies 15 and 16. While passing the parison 14 through the molds 15 and 16. At this time, since the narrowed portion 18 of the parison passage 17 is expanded by the movable cores 19 and 20, the parison 14 having a large diameter can be smoothly passed through the parison passage 17 and the air flow accompanying the vacuum suction can be accommodated. As the parison 14 is pulled in, the parison 14 can be passed through without being scratched.

In this way, after the parison 14 is passed to the predetermined position of the parison passage 17 of the molds 15 and 16, the working fluid is supplied into the cylinder chambers 15c and 16c through the control valves 21 and 22, and the movable core 19 is moved. , 20 are advanced to a state corresponding to the product shape. Then, gas is supplied into the parison 14 to inflate it and blow molding is performed.

In this blow molding, the parison 14 has a three-dimensional shape close to the shape of the product, and since the parison 14 having a diameter larger than the diameter d of the narrowed portion 18 is used, it is smaller than the conventional narrowed portion. The blow-up ratio can be reduced as compared with the case of using a parison having a diameter, and uneven thickness can be reduced to improve product quality. Further, even if there is a part having a complicated product shape and a small passage cross-sectional area, the parison 14 can be passed through without any trouble, so that there are few restrictions on the product shape that can be blow-molded, and a wide variety of products can be manufactured. After this blow molding, mold 1
A series of blow molding is completed by opening 5, 16 and taking out the blow molded product.

In the above embodiment, the movable core is moved by the piston rod of the cylinder chamber formed in the mold, but the present invention is not limited to this, and other driving mechanism such as driving from outside the mold is used. You may do it.

[0020]

As described above in detail with reference to the embodiment, according to the blow molding apparatus of the present invention, the cross section of the parison passage in the mold which has been clamped has a small cross section. Since a movable core that can expand the passage cross-sectional area by changing the diameter and spacing is provided, when the parison is passed through the parison passage in the mold, the movable core is retracted and the diameter of the throttle is reduced. On the other hand, when the parison is blow-molded after passing through the parison passage in the mold, the movable core can be moved to a position matching the product shape and blow-molded. Therefore, a parison having a large diameter can be used regardless of the size of the narrowed portion of the parison passage in the mold, and the blow-up ratio can be reduced to prevent uneven thickness of the product. In addition, even if the product has a complicated shape such as a three-dimensional shape with multiple drawing parts, by providing a movable core in the drawing part, it is possible to easily pass a large-diameter parison, and blow molding is possible. The range of can be greatly expanded.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a mold portion according to an embodiment of a blow molding apparatus of the present invention.

FIG. 2 is a vertical sectional view of a conventional blow molding die.

[Explanation of symbols]

 10 Blow Molding Equipment 11 Parison Head 12 Die 13 Head Core 14 Parison 15 Mold 16 Mold 17 Parison Passage 18 Throttling Part 19 Movable Core 20 Movable Core 21 Control Valve 22 Control Valve D Parison Passage Diameter d Throttling Diameter S1, S2 Moving stroke of movable core

Claims (1)

[Claims] 1. A blow molding apparatus for obtaining a blow-molded article having a predetermined shape by vacuum suction while delivering a parison into a mold that has been clamped, and blowing gas into the parison passed through the mold. A blow molding device characterized in that a movable core for enlarging a passage cross-sectional area is provided in a die portion which is a narrowing portion of a parison passage in the die.