JPH05131530A - Method for supporting parison in blow molding machine - Google Patents

Abstract

PURPOSE:To prevent defect such as generation of molding failure of a parison by inhibiting a supporting member for supporting the parison from the internal and external parts thereof from being directly brought into contact with the parison in the case of molding it into an asymmetrical cross section or a three- dimensional arbitrary shape. CONSTITUTION:A parison 1 is intruded into an open mold 4 from a die 2. After the parison 1 is intruded in a prescribed length, the mold 4 is closed and pressure is exerted to the inside of the parison and gas is blown to obtain the hollow plastic moldings. In this blow molding machine, supporting members 5 whose surfaces are formed of a porous member are provided in the lower part of the die 2. The parison is deformed by compressing or elongating the parison from the internal part or the external part of the parison by the supporting members 5. Moreover gas is spouted through gas feed passages 7 from the insides of the porous members. The parison of molten resin and the supporting members 5 formed of the porous member is made uncontacted with each other and the parison is supported. Thereby the parison is deformed into an asymmetrical cross section or a three-dimensional arbitrary shape in the unadhesive conditions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supporting a parison of a blow molding machine for forming a parison having an asymmetrical cross section or a three-dimensional shape in blow molding for producing a hollow plastic product.

[0002]

2. Description of the Related Art In conventional blow molding, a parison is extruded from a die into an open mold, then the mold is closed to pinch the top and bottom of the parison, and a gas is blown into the parison through a blow pin to form a hollow shape. Molded plastic products. The cross-sectional shape of the parison is mainly a ring shape, but when molding a product having an asymmetric cross-section, as shown in JP-A-3-136827, a non-circular shape for the purpose of uniform thickness, A method of extruding a non-circular, asymmetrical parison using a die 2 having an outflow slit 14 having an asymmetrical cross section is adopted (FIGS. 5 and 6). In addition, 12 is a die lip and 13 is a die core. As means for forming an asymmetrical or three-dimensionally complicated parison, as shown in JP-A-1-145118, a cylindrical parison 1 extruded from a die 2 having a circular slit is provided outside or inside the parison. The means for pre-deforming by using the external supporting means (expander) 15 is adopted (FIG. 7). In addition, 4 is a metal mold | die.

[0003]

[Patent Document 1] Japanese Patent Application Laid-Open No. 3-136827 which blow-molds a non-circular, asymmetric parison with a die 2 having a slit 14 having a non-circular, asymmetric cross-section. In the conventional example shown in FIG. 5 (FIGS. 5 and 6), it was necessary to change the shape of the die slit 14 to a different shape each time the symmetrical product was changed. Therefore, it is not versatile, and since it is a process for a resin flow path that flows under high pressure, it requires strength, and the surface of the flow path needs to be sufficiently finished, so that there is a drawback that the device cost increases. Further, in the conventional example (FIG. 7) disclosed in Japanese Patent Laid-Open No. 1-145118, which has the external supporting means 15 for preliminarily deforming the parison 1 extruded from the die 2, the supporting means 15 directly contacts the parison 1 so that the adhesiveness is increased. With a high resin, the supporting means 15 and the parison 1 adhere to each other.
Therefore, after the parison is pre-deformed, the supporting means 1
When 5 was separated from the parison 1, there was a defect that the parison 1 was dragged by the parison 1 to be out of the target shape or the shape was not stable. Also, this supporting means 1
When 5 is brought into direct contact with the parison 1 and the contact points of both are to be slipped to give a preliminary deformation to the parison having a complicated shape, there is a drawback that the desired shape cannot be obtained because both stick together. The present invention is intended to provide an effective method for solving the above-mentioned conventional problems relating to molding of a parison having an arbitrary cross-section.

[0004]

Therefore, according to the present invention, a parison is extruded from a die into an open mold, the parison is extruded to a predetermined length, then the mold is closed, and pressure is applied to the inside of the parison to blow gas. In a blow molding machine for obtaining a hollow plastic molded product, a supporting member having a surface formed of a porous member is provided at the bottom of a die, and the supporting member deforms by compressing or extending the parison from inside or outside the parison. At the same time, a gas is ejected from the inside of the porous member, and the parison of the molten resin and the supporting member made of the porous member are supported in a non-contact manner so that the parison has an asymmetric cross section or a three-dimensional shape under non-adhesive conditions. This is a method of deforming into an arbitrary shape, which is a means for solving the problem.

[0005]

[Function] A press for preforming the parison so that the parison has an asymmetric cross section or an arbitrary three-dimensional shape by supporting or pressing the parison from the inside or the outside of the parison under the die for extruding the molten resin parison. Alternatively, a portion of the supporting parison supporting member that comes into contact with the parison is formed of a porous member, a gas supply passage is provided inside, and a gas supply pipe is connected to the inlet side of the gas supply passage. The gas supply pipe is connected to a gas supply source via a switching valve capable of supplying or stopping the gas or a gas flow rate / pressure adjusting device. The gas pressure-fed from the gas supply pipe is introduced into a gas supply passage provided inside the parison support member, and jets from the surface of the parison support member through an innumerable fine passage extending from the passage to the surface. The contact surface between the parison support member and the parison is not in contact with the jetted air, and the group of fine passages communicating with the non-contact surface serves as a resistance against the outflow air and enables the air supply to the contact portion. The parison supporting means as described above is matched with the shape of the parison to be preformed, and is moved in the three-dimensional space by the moving means as in the conventional case to perform the preforming.
The parison that has been subjected to this preforming is guided into the mold, and after the mold is clamped, it is blow molded into a product. Press the parison
The number of supporting members to be held may be one or plural, and the movement thereof is one of the axis parallel, the circumferential direction, the radial direction, or a composite direction in which a plurality of them are combined. May be. Further, in the case of molding a more complicated product, the number of pressing / holding members must be plural, and the three-dimensional movement in which the movement directions are combined is required. Furthermore, the parison support means conforms to the shape of the parison to be preformed,
The parison is moved by the moving means as described above to guide the parison in a non-contact manner.

According to the present invention, the surface of the parison contact portion of the supporting member that presses and supports the parison is formed of a porous body, and gas is ejected from the inside, and the molten parison extruded from the die and this supporting member. A thin gas layer is formed between the two, and the adhesion of the parison and the supporting member can be prevented. Therefore, even when there is relative movement between the parison and the support member, such as when the parison support member is moved along the parison surface when the parison is deformed, there is no sticking between the two, so that preparatory deformation and holding of the parison are facilitated. When a gas inflow, stop switching, or gas flow rate / pressure adjustment mechanism is attached, the friction force between the parison support member and the parison can be changed. When there is no slippage at the contact part of the support member, the parison is deformed while stretching in the surface direction, or conversely, the gas flow rate and pressure are increased, and the parison is slid at the contact part of the parison support member, and the radius The degree of freedom of pre-deformation is improved, for example, the direction parison can be deformed. In addition, since the gas is ejected through the porous body and the flow rate and the inflow pressure of the gas can be controlled, it is possible to prevent the parison from shaking and bulging due to the gas flow.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. FIGS. 1 and 2 show an apparatus for carrying out the method of the present invention.
Is provided from the outside and a parison supporting means 3'to support it from the inside is provided, and the parison 1 is pre-deformed by moving means (not shown) to form the pre-formed parison 2.
While 0 is obtained, it is moved and guided to an openable / closable mold 4 for blow molding into a final product shape. The parison supporting means 3 and 3'includes a parison supporting member 5 which is in contact with the parison 1 or 20 and is made of a porous member. A gas supply passage 6 is formed in the parison supporting member 5 and a gas supply pipe 7 is provided at one end thereof.
It is a configuration in which is connected. The pipe 7 is connected to a gas supply source 11 via a flexible portion 18, a switching valve 8 and a gas flow rate adjusting or supply pressure adjusting valve 9. The valve 8,
The valve operation 9 is controlled by the control device 10. Further, the gas supply passage 6 is formed by molding one end of the pipe 7 along the cross-sectional shape of the parison support member 5 and inserting it into the inside to form a hole 19 in the pipe wall.
The structure (FIG. 2 (a)) may be provided, or a part of the pipe end may be inserted into the end of the parison support member 5 to form a gas supply pipe passage 6'provided inside the parison support member 5. They may be communicated (Fig. 2 (b)).

When the parison supporting means 3 and 3'is configured as described above, the gas supplied from the pipe 7 is guided to the gas flow path 6 or 6'of the parison supporting member 5 and innumerable fine particles of the porous member. The parison 1 or 20 is jetted from the surface through the passage 21 and is supported by the support member 5 through a thin film of air. That is, the parison 1 or 20 is non-contact supported by the parison supporting means 3, 3 '. The cross section of the parison supporting member 5 is matched with the shape of the supporting portion of the preformed parison 20, and the parison supporting means 3 and 3'is moved in a three-dimensional space by a moving means (not shown) to support the parison 1 from inside and outside. By doing so, the preformed parison 20 having an arbitrary shape as shown in FIGS. 3A to 3E can be stably obtained.

[0009]

Since the present invention is constructed as described in detail above, the drawdown of the parison can be prevented and controlled, and the parison extruded from the die can be corrected so that the die and the parison are relatively opposed to each other. It is possible to ensure the retention of the parison such as preventing the misalignment, and it is possible to prevent the molding defect due to the product thickness unevenness due to the drawdown of the parison and the defective insertion of the blow pin. In addition, while maintaining a non-adhesive state with the parison support member, it is possible to produce a parison with an irregular cross section or a three-dimensionally complicated shape at a relatively low cost, so it can be applied to blow-molded products of various shapes. It is possible to provide effective means.

[Brief description of drawings]

FIG. 1 is a systematic diagram of an apparatus for carrying out the method of the present invention.

FIG. 2 is a cross-sectional view showing an embodiment of the parison supporting means in FIG.

FIG. 3 is a sectional view showing a shape example of a preformed parison.

FIG. 4 is a perspective view showing one example of the shape of a preformed parison.

FIG. 5 is a vertical cross-sectional view of a conventional variant parison extrusion die.

6 is a sectional view taken along line AA of FIG.

FIG. 7 is a cross-sectional view of a conventional parison preforming apparatus in which a parison supporting means for pressing the outside of the parison is provided at the bottom of a conventional die.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 parison 2 die 3,3 'parison supporting means 4 mold 5 parison supporting member 6,6' gas supply passage 7 gas supply pipe 8 switching valve 9 gas flow rate or pressure adjusting valve 10 controller 11 gas supply source 18 flexible Tube 19 Hole 20 Preformed parison 21 Fine passage

Claims (1)

[Claims] 1. A blow molding machine for extruding a parison into an open mold from a die, extruding the parison to a predetermined length, then closing the mold, and applying gas into the parison to blow a gas to obtain a hollow plastic molded product. In the above, in the lower part of the die, a support member having a surface formed of a porous member is provided, and by the support member, the parison is compressed or expanded from the inside or outside of the parison to be deformed, and the gas is supplied from the inside of the porous member. Is ejected and the non-contact support is provided between the parison of the molten resin and the supporting member made of the same porous member, whereby the parison is deformed into an asymmetric cross section or an arbitrary three-dimensional shape under non-adhesive conditions. Blow molding machine parison support method.