JPH0839659A - Blow molding method using stretchable core - Google Patents

Abstract

PURPOSE:To easily obtain a molded product having definite wall thickness by also introducing compressed gas into a stretchable core while expanding a parison by blow air immediately after the parison suspended from a die is clamped by female and male molds. CONSTITUTION:In a blow molding machine 1, a parison P is suspended to the gap between a pair of a male mold 8a having a smooth cavity surface and a female mold 8b equipped with a plurality of stretchable cores 12 by a die head 2, a mandrel 3 and an extruder 4. Each of the stretchable cores 12 is composed of material quality having stretchability. Compressed gas (e.g. 5-15kg/cm<2>) is supplied to the stretchable cores 12 from a compressed gas source through a conduit 14 and the gas introducing ports 13 provided in the female mold 8b. The stretchable plugs 12 are expanded up to a desired size by introducing the compressed gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow molding method using a stretchable core.

[0002]

2. Description of the Related Art In blow molding in which a hollow resin product is made from a parison that is cylindrically injected or extruded from a die head, the parison is injected or extruded from the dice head and pre-blown into a bag-shaped parison by a parison pinch. After inflating slightly, put it in an open mold and close the mold, and after degassing the gas in the cavity formed by the mold and parison, a vacuum pump device from a small air vent hole leading to the mold surface After sucking air through the, the high pressure air is blown into the parison to form the parison into a predetermined shape based on the cavity and then cooled by a mold to complete the molding. In this way, the molded resin product is taken out by opening the mold. The thing shown in FIG. 10 shows the conventional blow molding machine.

In FIG. 10, the molten resin is used for the die head 2
2 shows a so-called side-feed type blow molding machine 1 which is supplied from one side side, and the resin in a high-temperature molten state pressed by the extruder 4 is fed to the die head 2 and the mandrel 3 via the resin supply port 2a. The parison P is formed by being discharged from the lowermost annular space passage 7 through an annular passage provided between The core 3a is connected to the paricon rod 6a penetrating the mandrel 3 and is slightly moved up and down in the vertical direction by the operation of the paricon cylinder 6 to control the wall thickness of the parison P (gap). ) Can be adjusted.

On the other hand, as shown in FIG. 11, a resin is molded into a panel shape having a bag-shaped air space inside to be used as a building material such as a door (gate) or a simple wall material (partition wall). However, it has come to be considered to use it for floors such as formwork for concrete pouring and simple piers, but these molded products have considerable structural strength despite their light weight,
It has the feature of being strong against deformation.

[0005]

However, when a panel-shaped molded article having such a bag-shaped space inside is manufactured by blow molding, for example, when a tack-off core is used, tack-off occurs. A hydraulic drive unit must be used to move the child forward and backward, which not only complicates the structure of the mold, but also increases the thickness of the mold, resulting in poor maintainability.

The present invention has been made in view of the above conventional problems, and provides a blow molding method capable of easily obtaining a molded product having a constant wall thickness.

[0007]

In order to achieve the above object, a parison hung from a die using a male die having a smooth surface and a female die having a plurality of expandable telescopic cores is used. Immediately after closing the mold with the female mold and the male mold, the parison was molded by inflating the parison with blow air while introducing compressed gas into the expansion core.

[0008]

[Function] At the same time as clamping the parison hung from the die with a pair of left and right dies, at the same time introducing compressed gas into the expansion core provided on the female die side to expand it, introducing blow air into the parison. Then, when the back surface of the panel is lightly pressed against the front surface of the parison that closely adheres to the cavity surface of the male mold, the parison naturally follows the cavity surface of the female mold and obtains a molded product with a constant wall thickness without local expansion. be able to.

[0009]

EXAMPLES Specific examples of a blow molding method using an expandable core according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an overall vertical sectional view of a blow molding machine, FIG.
Shows a state immediately after the parison is clamped by both molds, FIG. 3 shows a state in which compressed gas is introduced into the expansion core and the parison, and FIG. 4 is a cross section taken from A to A of FIG. Fig. 5, Fig. 5 is a diagram in which the expansion and contraction of the expansion core is completed, and Fig. 6 is BB
Sectional view seen from above, FIG. 7 is a perspective view of a panel-shaped molded product, and FIG.
9 is a plan view of an expansion / contraction core according to another embodiment of the present invention.
FIG. 9 is a partially enlarged plan view of a panel-shaped molded product manufactured using the expandable core shown in FIG. 8.

As shown in FIG. 1, a blow molding machine 1 includes a die head 2, a mandrel 3, an extruder 4 and a Parison cylinder 6 which have the same structure as a conventional structure and forms a parison (particularly a flat parison) P into a pair of left and right dies 8. Droop between. In the blow molding machine 1 of the present invention, the mold 8 is different from the conventional structure and is formed by a male mold 8a having a smooth cavity surface and a female mold 8b having a plurality of expandable cores 12. ing.

The elastic core 12 is preferably made of a material having elasticity and heat resistance, such as silicone rubber or fluororubber.

If such a material is used, the heat resistance is 3
It can be up to 00 ° C and elongation rate of 600%.

Compressed gas (for example, 5 to 1) to the expandable core 12
5 kg / cm ² ) is supplied from a compressed gas source (not shown) through a conduit 14 through a gas introduction hole 13 provided in the female mold 8b. Thereby, the expandable core 12 can be expanded to a desired size.

Both molds 8a and 8b are connected to the back of a platen (not shown) so that they can be opened and closed (movable forward and backward).

A blow molding method using the mold having the above structure will be described.

In the blow molding machine 1 having the mold configured as described above, both dies 8a and 8b are opened and the parison P having a circular cross section (preferably having a major axis in the lateral width direction of the mold). After hanging a substantially elliptical flat parison) and making it stand still, a mold clamping cylinder (not shown) attached to the outside of the left and right molds 8a and 8b is operated to perform mold clamping (FIG. 2).

Immediately after the mold is clamped, the blow pin 5
While blowing a blow air 16 of 7 kg / cm ² and introducing a compressed gas 15 such as compressed air for expanding the expandable core 12, the male mold 8a and the female mold 8a are expanded while being expanded from inside and outside the parison P. The mold 8b is imprinted (FIG. 3).

If this state is further continued, the expansion / contraction core 12 expands to a predetermined size and the panel back surface 24 becomes the panel front surface 2.
It comes into light contact with the backside of 2 (Fig. 7). Compressed gas 1
Although N2 gas may be used for 5, the cooling time can be shortened by introducing the cooled compressed gas 15 halfway in the state where the shaping of the parison P is completed.

In the present embodiment, the expandable core 12 has a cylindrical outer shape as shown in FIG. 4, but the invention is not limited to this, and the expandable core 12 shown in FIG. A core 12 may be used to obtain a panel molded product 10 as shown in FIG.

Simultaneously with the completion of blowing the blow air 16, the blow air 16 in the molded product 10 is rapidly removed, and then the compressed gas 15 in the expandable core 12 is also removed.

Since the expandable core 12 from which the compressed gas 15 has been removed becomes small in this way, the mold is opened as it is, and the molded product 10 that has been cooled and solidified is taken out.

[0023]

As is apparent from the above description, according to the present invention, a male die having a smooth surface and a female die having a plurality of expandable telescopic cores are used, and the male die is suspended from a die. While the parison was expanded with blow air immediately after the parison was closed with the female mold and the male mold, compressed gas was also introduced into the expansion core to mold the parison. Tack on the front, back and peripheral surfaces
Since it is turned off, the strength of the molded product increases.

[Brief description of drawings]

FIG. 1 is an overall vertical sectional view of a blow molding machine according to an embodiment of the present invention.

FIG. 2 is a diagram showing a state immediately after mold clamping in which a parison is sandwiched by both molds.

FIG. 3 is a view showing a state in which a compressed gas is introduced into the expandable core and the parison.

4 is a cross-sectional view as seen from AA of FIG.

FIG. 5 is a view showing that the expansion and contraction of the elastic core has been completed.

6 is a cross-sectional view as seen from BB of FIG.

FIG. 7 is a perspective view of a panel-shaped molded product.

FIG. 8 is a plan view of an expandable core according to another embodiment of the present invention.

9 is a partially enlarged plan view of a panel-shaped molded product manufactured using the expandable core shown in FIG.

FIG. 10 is an overall vertical sectional view of a conventional blow molding machine.

FIG. 11 is a perspective view of a conventional panel-shaped molded product.

[Explanation of symbols]

 1 Blow Molding Machine 2 Die Head 2a Resin Supply Port 3 Mandrel 3a Core 4 Extruder 6 Paricon Cylinder 7 Annular Space Passage 8 Mold 8a Male Mold 8b Female Mold 9 Cavity 10 Molded Product 12 Expansion Core 13 Gas Introduction Hole 14 Conduit 15 Compressed gas 16 Blow air 22 Panel surface 24 Panel back surface P Parison

Claims (1)

[Claims] 1. A male mold having a smooth surface and a female mold having a plurality of elastic cores are used, and a parison hanging from a die is used as the female mold and the male mold. A blow molding method using an expansion core, wherein the parison is molded by introducing compressed gas into the expansion core while expanding the parison with blow air immediately after the mold is closed.