JPH068311A - Blow molding device - Google Patents

Abstract

PURPOSE:To obtain a molded article having a uniform wall thickness while reducing the development of burr. CONSTITUTION:At the molding of a hollow container having a constriction in its central part, parison P is pre-formed by being pinched with a pair of insert molds 4 and 5 before mold clamping. In succession to the pre-formed, main molds 2 and 3 are clamped from the directions normal to the actuating directions of the insert molds 4 and 5, resulting in molding a hollow container by utilizing the insert molds 4 and 5, which are restricted by the main molds 2 and 3, as some parts of the main molds 2 and 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow molding device for molding a hollow molded article represented by a hollow container.

[0002]

2. Description of the Related Art When a flat hollow container W having a constricted portion Q as shown in FIGS. 6 and 7 is molded by a blow molding method, a parison extruded from an extruder is clamped in the direction of arrow a. On the other hand, it is basically formed by injecting air into the parison after sandwiching it with a pair of molds, while considering the shape of the hollow container W which is the final product,
As shown in FIG. 8, the diameter of the parison P is preset to the hollow container W.
The diameter of the parison P is set to be slightly smaller than the maximum width dimension of the hollow container W, that is, the width dimension b of the bulging portion S in advance, as shown in FIG. I have to.

Further, as a blow molding device for molding a three-dimensionally bent plastic pipe, there is disclosed in Japanese Patent Laid-Open No.
As shown in Japanese Patent No. 193326, in addition to a pair of main molds, a preliminary mold that moves forward and backward in a direction substantially orthogonal to the mold clamping direction of this main mold is provided, and the parison immediately after extrusion is bent by the preliminary mold. In some cases, the pre-formed parison is held by a main mold while being bent three-dimensionally so as to have a shape of a molded product.

[0004]

However, as shown in FIG. 8, the diameter of the parison P is set to the constricted portion Q of the hollow container W.
If it is set slightly smaller than
The parison P is inscribed on the four sides of the mold in the portion corresponding to the constricted portion Q of the hollow container W, and the parison P is inscribed on the two sides of the mold excluding the bulging portion S in the portion other than the constricted portion Q. The part of the parison P that comes into contact with the mold comes into contact with the mold, cooling is promoted, and the parison P itself becomes difficult to stretch. Therefore, since the portion of the parison P that should become the bulging portion S of the hollow container W is extended to the end, as shown in FIG. 7, the wall thickness t1 at the corner portion of the bulging portion S is the normal portion. The wall thickness is relatively smaller than the thickness t2, which is likely to cause a problem in product strength. If the wall thickness of the parison P itself is increased in order to increase the wall thickness t1 at the corner portion, the weight of the hollow container W is increased, and the weight reduction, which is an advantage of the blow molded product, cannot be realized.

On the other hand, as shown in FIG.
If the diameter is set to be slightly smaller than the width dimension b of the bulging portion S, there will be no local change in wall thickness or weight problem as shown in FIG. Besides, burrs F3 are generated in the portion corresponding to the constricted portion Q, and the number of deburring steps in the subsequent process is increased, which is not preferable.

A relatively large flash formed by crushing a part of the parison P with a mold, such as flash F3 generated in the constricted portion Q, including the upper and lower flashes F1 and F2. Since the strength of the generated part is weaker than that of other parts, there is a demand to reduce the number of burrs generated in the entire product as much as possible. Especially when a multi-layer parison is used as the parison P, the burrs There is a demand to reduce the amount of flash generated as much as possible because it is difficult to recycle. in spite of,
Compared with the method of FIG. 8, the method of FIG. 9 has a larger number of burrs and the amount of burrs generated, and cannot sufficiently meet the desired request.

Further, according to the blow molding apparatus disclosed in Japanese Patent Laid-Open No. 3-193326, it is necessary to return the preliminary mold to a position where it does not interfere with the main mold after the preliminary molding of the parison. Becomes longer. Moreover, when the preliminary mold returns as described above, a phenomenon occurs in which the parison tries to restore its initial shape due to its own weight, etc.When the main mold is clamped, the parison is caught more than necessary in the mating surface between the main molds. It is easy to cause flash.

The present invention has been made in view of the above problems, and in particular, a blow molding apparatus capable of reducing the occurrence of burrs while achieving uniform thickness and shortening the cycle time is provided. It is the one we are trying to provide.

[0009]

A blow molding apparatus according to the present invention comprises an extruder for pushing a parison downward, and the extruder is arranged on both sides of the parison to form a product part space corresponding to a shape of a molded product by a mold clamping operation. A pair of main molds and a parison that is provided on the side of the parison and that can be moved forward and backward in a direction substantially orthogonal to the mold clamping direction of the main mold, and moves forward before the mold clamping operation of the main mold. A part of the mold is preformed into a predetermined shape, and an insert mold that is constrained by the pair of main molds and functions as a part of the main mold when the main mold is clamped.

[0010]

According to this structure, prior to the mold clamping operation of the main mold, the pair of insert molds advance in a direction substantially orthogonal to the mold clamping direction of the main mold to preform the parison immediately after extrusion. Then, the main mold performs the mold clamping operation while the parison is constrained by the pair of insert molds, and the main mold clamps the pair of insert molds at the same time as the parison is sandwiched. This allows the insert mold to function as part of the master mold.

[0011]

2 and 3 are views showing an embodiment of the present invention, in which, on both sides of a parison P extruded from an extruder 1, apart from a pair of main molds 2 and 3 which move toward and away from each other, A pair of insert dies 4 and 5 that move forward and backward in a direction substantially orthogonal to the mold clamping direction of the main dies 2 and 3 are provided. These pair of insert molds 4 and 5 are formed in a shape corresponding to the constricted portion Q of the hollow container W shown in FIGS. It is designed to move backward.

On the other hand, the pair of main molds 2 and 3 has a mold surface 2a for forming a product part space (cavity) R when the mold is clamped.
3a is formed, and a concave portion 2 for receiving the insert molds 4 and 5 continuously on the mold surfaces 2a and 3a.
b and 3b are formed. The main molds 2 and 3 are fixed to the platen 8 or 9.

Therefore, according to the structure of this embodiment, as shown in FIG. 5 in addition to FIGS. 2 and 3, the pair of main molds 2 and 3 are in the mold open state and the pair of insert molds 4 and 5 are in the retracted position P1. The parison P is extruded from the extruder 1 and the lower end of the parison P is inserted into the blow pin 10 and the expand pin 11 in the state. At this time, the diameter of the parison P is set to be slightly smaller than the maximum width dimension b of the hollow container W shown in FIGS.

When the parison P is pushed out by a predetermined amount,
As shown in FIG. 1, the pair of insert dies 4 and 5 advance to the advance position P2 in accordance with the extension operation of the cylinders 6 and 7. By the forward movement of the insert molds 4 and 5, the central portion of the parison P is pushed inward and deformed, and the constricted portion Q of the hollow container W shown in FIGS. 6 and 7 is preformed.
Then, in the part of the parison P that is in contact with the insert molds 4 and 5, heat is taken away by the insert molds 4 and 5 to be cooled, and the wall thickness required for the constricted portion Q is secured.

A clearance C1 is secured between the insert dies 4 and 5 advanced to the advance position P2 and the recesses 2b and 3b on the main dies 2 and 3 side in the forward and backward directions of the insert dies 4 and 5. . As a result, the main molds 2, 3 will be used during mold clamping, which will be described later.
And the insert dies 4 and 5 can be prevented from interfering with each other, and the parison P can be prevented from being caught between the recesses 2b and 3b and the insert dies 4 and 5.

When the pair of insert molds 4 and 5 are advanced to the advance position P2 and the parison P is preformed as described above, the pair of main molds 2 and 3 perform the mold clamping operation as shown in FIG. The pair of main molds 2 and 3 receives the insert molds 4 and 5 in the recesses 2b and 3b thereof, and the mold surfaces 2a and
The parison P is inserted into the product space R formed by 3a. As a result, the pair of insert molds 4 and 5 are constrained by the recesses 2b and 3b of the main molds 2 and 3 and function as a part of the main molds 2 and 3, while the main molds 2 and 3 and the insert mold 4 are inserted. , 5, a gap C2 is secured in the mold clamping direction of the main molds 2, 3.

After that, the rod-side chambers 6a, 7a of the cylinders 6, 7 which are the driving sources of the insert molds 4, 5 are released to the drain side, and the blow pin 10 of FIG. Blow in. As a result, the parison P expands so as to come into close contact with the product space R of the main molds 2 and 3 and is molded into the shape of the hollow container W shown in FIGS. Due to the expansion, it retreats by the above-mentioned gap C1 and the step between the mold surfaces 2a and 3a of the main molds 2 and 3 disappears and smooth alignment is achieved.

After the hollow container W, which is a molded product, has been molded, the hollow container W is evacuated after waiting for a predetermined cooling time, and the pair of insert molds 4 is opened after the main molds 2 and 3 are opened. , 5 are retracted and the hollow container W is taken out.

As described above, according to this embodiment, the portion corresponding to the constricted portion Q of the hollow container W is preliminarily preformed by the insert molds 4 and 5 based on the conventional blow molding method shown in FIG. Therefore, it is possible to eliminate the occurrence of burrs in the portion corresponding to the constricted portion Q.

[0020]

As described above, according to the present invention, a part of the parison is preformed while advancing in a direction substantially orthogonal to the mold clamping direction of the main mold prior to the mold clamping operation of the main mold. By providing an insert mold that functions as a part of the main mold during mold clamping, even when molding a molded product with a constricted central part, the parison diameter is set according to the maximum width dimension of the molded product. As a result, it is possible not only to form a molded product with a uniform thickness without increasing the weight, but also to eliminate the occurrence of burrs in the above constricted parts and greatly reduce the amount of burrs and the number of deburring steps. Can be reduced to

Further, since the insert mold in which the parison is preformed functions as it is as a part of the main mold, the mold of the main mold is different from the conventional method in which the mold involved in the preforming is returned to its original shape. It is possible to eliminate the occurrence of burrs due to the parison being caught in the mating surfaces and to shorten the molding cycle time.

[Brief description of drawings]

FIG. 1 is a horizontal sectional view showing an embodiment of the present invention, showing a state after pre-molding of a parison and before mold clamping.

FIG. 2 is a vertical sectional explanatory view showing a state before preforming according to an embodiment of the present invention.

3 is a sectional view taken along the line AA of FIG.

FIG. 4 is a horizontal sectional view showing a state when the mold is clamped from the state of FIG.

5 is a flowchart showing a molding procedure in the blow molding apparatus of FIG.

FIG. 6 is a perspective view showing the shape of a hollow container as an example of a molded product.

7 is a sectional view taken along the line BB of FIG.

FIG. 8 is an explanatory view showing an example of a conventional blow molding method.

FIG. 9 is an explanatory view showing another example of the conventional blow molding method.

[Explanation of symbols]

 1 ... Extruder 2,3 ... Main mold 4,5 ... Insert mold 6,7 ... Cylinder 10 ... Blow pin P ... Parison P1 ... Retracted position P2 ... Advance position Q ... Constricted portion R ... Product space W ... Hollow container (molding Goods)

Claims (1)

[Claims] 1. An extruder for pushing a parison downward, a pair of main molds arranged on both sides of the parison to form a product part space corresponding to a shape of a molded product by a mold clamping operation, and side parts of the parison. And is capable of advancing and retracting in a direction substantially orthogonal to the mold clamping direction of the main mold and moving forward before the mold clamping operation of the main mold to preform a part of the parison into a predetermined molded product shape. On the other hand, the blow molding apparatus is characterized by further comprising: an insert mold which is constrained by the pair of main molds and functions as a part of the main mold when the main mold is clamped.