JPH0123385B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a plastic container, and more particularly, to a method for manufacturing a plastic container that has a tubular portion around the opening and is manufactured by blow molding.

Generally, in the case of a box-shaped container that is made up of a bottom wall and a peripheral wall and is open on one side, the strength and rigidity of the periphery of the opening are weak, so it is natural to consider reinforcing the periphery of the opening. The same applies to plastic containers, as can be seen in, for example, Japanese Utility Model Application Publication No. 53-6715 and Japanese Patent Application Publication No. 48-12179. The one disclosed in Japanese Utility Model Application Publication No. 53-6715 has a reinforcing structure by bending the opening periphery of the plastic container outward, as shown in FIG. Since the periphery is simply bent outward, the strength and rigidity are not significantly increased.If further strength and rigidity are required, there is a method as disclosed in Japanese Patent Application Laid-Open No. 12179/1983. . That is, as shown in FIG. 7, the opening periphery of the plastic container is bent outward and a reinforcing plate is attached to the opening periphery to create a reinforced structure.
In addition to bending the opening periphery outward, it is necessary to attach a reinforcing plate, which is not only complicated to manufacture, but also
It also makes you look bad.

In view of the above circumstances, the present invention was made as a result of intensive research to find a method for manufacturing a plastic container that has enhanced strength and rigidity around the opening, has a good appearance, and is easy to manufacture. The present invention was completed by applying a double wall blow molding method using thermoplastic plastic.

An example of the method for manufacturing a plastic container according to the present invention will be described below with reference to FIG. The containers in this embodiment are two containers 6 and 7, for example, a storage case such as a document case in which a container body and a lid are connected by a hinge 8 (see Fig. 2). This shows an example in which the connecting hinges 8 are integrally molded.

In FIG. 1A, 9 and 10 are a pair of split-type molding molds, and one of the molds 9 has a concave cavity 9a for forming the outer wall 3a of the containers 6 and 7 to be molded. and the concave cavity 9
Containers 6 and 7 to be molded located on the periphery of a
A peripheral hollow molding cavity 9c for forming the tubular portion 4 is formed at the peripheral edge of the opening. Further, in this embodiment, a compressed portion 9b for forming a hinge 8 for connecting two containers 6, 7 to be molded is formed between the adjacent peripheral hollow molding cavities 9c. .

In addition, the other mold 10 includes the one mold 9 described above.
Inner wall 3b of the container 6, 7 to be molded at a position opposite to the concave cavity 9a in
a convex cavity 10a for forming the convex cavity 10a, and a peripheral hollow molding cavity 9c located at the periphery of the convex cavity 10a in the one mold 9;
By forming a welding part 4c that partially welds the outer wall 3a and the inner wall 3b in the vicinity of the opening periphery of the container 6, 7 to be molded in cooperation with the container 6, 7 to be molded. A peripheral weld molding cavity 10c for forming the tubular portion 4 is formed at the peripheral edge of the opening. Further, in this embodiment, two containers 6 and 7 to be molded in cooperation with the compression part 9b of the one mold 9 are connected between the adjacent peripheral weld molding cavities 10c. A compressed portion 10b is formed for forming the hinge 8.

Then, as shown in FIG. 1A, the two molds 9 and 10 as described above are placed facing each other in an open state, and between the two molds 9 and 10, a plasticized plastic is extruded from an extrusion die 11. A parison 12 (outer diameter 230 mm, wall thickness 3 mm) made of high-density polyethylene is positioned.

Next, as shown in FIG. 1B, both molds 9, 1
0 in the closing direction, insert the parison 12, and insert the blow pin 13 into the parison 12 after changing the mold.
Inject pressurized fluid (6 kg/cm ² compressed air) from
The parison 12 is inserted into the concave and convex cavities 9.
a, 10a, a hollow double-walled container formed along the shape of the hollow space formed by the peripheral hollow molding cavity 9c and the peripheral welding molding cavity 10, and having a partial welded part 4c. 6, 7. Specifically, a semi-finished product is formed, which consists of a hollow double-walled container body and lid each having a partial welded portion 4c, and a hinge 8 that flexibly connects the two. .

Subsequently, after cooling the semi-finished product, both molds 9 and 10 are opened and the semi-finished product is taken out, as shown in FIG. 1C.
Each inner wall 3b is partially welded to the outer wall 3a by a welded portion 4c.
By cutting and removing the main body from the inside with a knife or press, the main body becomes a plastic container having a single wall structure and a tubular part 4 around the opening, that is, a second plastic container.
A container as shown in the figure is obtained.

However, in the above embodiment, a method for manufacturing a plastic container in which two containers 6 and 7 were connected by a hinge 8 was shown, but when manufacturing a plastic container as shown in FIGS. 3 and 4, Of course, split-type molding molds 9 and 10 in which one concave cavity 9a and one convex cavity 10a are formed are used.

In addition, the cavities 9a, 1 of the molding molds 9, 10
By appropriately changing 0a, it is possible to manufacture a container as shown in FIG. B and C have a step 2a inside the opening periphery 4, which is formed by cutting out a part of the inner wall 3b of C, and using this step 2a, the main body Items stored in section 2,
Other members such as a sheet-like molded product or a band for storing the specified article can be secured by welding, screwing, adhesion, etc. Furthermore, although it is desirable that the partial welding of the outer wall 3a and the inner wall 3b to form the tubular portion 4 at the peripheral edge of the opening be performed over the entire circumference, the effects of the present invention can be achieved even if the welding is performed only partially.

The plastic used in the present invention is a blow-molded thermoplastic such as polyethylene, polypropylene, vinyl chloride, ABS, or polystyrene, and two sheets may be used in place of the parison during production. Further, the surface of the container obtained according to the present invention may be subjected to secondary processing such as flocking, lining, painting, coating, etc.

As mentioned above, the present invention is not only easy to manufacture because it is manufactured by the double wall blow molding method, but also
The obtained plastic container has a main body with a single wall structure and a tubular part 4 formed around the opening, so it is lightweight, has excellent rigidity, and strength, and the tubular part around the opening is integrally molded during manufacturing. Furthermore, since the tubular portion around the opening surrounds the opening of the container,
To obtain a plastic container that firmly retains its shape even if the inner wall is cut out, is strong, has no warping or distortion, is lightweight, and has sufficient internal volume.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, in which FIG. 1A is an explanatory diagram of a state in which a parison 12 is arranged between molds 9 and 10, and FIG. 1B is an explanatory diagram with the molds 9 and 10 closed. FIG. 1C is an explanatory diagram of the state in which pressurized fluid is injected from the blow pin 13, FIG. 1C is an explanatory diagram of the state taken out from the molds 9 and 10, and FIGS. Fig. 2 is a perspective view, Figs. 3 and 4 are perspective views and sectional views showing other aspects, and Fig. 5 A, B, C shows the container.
FIGS. 6 and 7 are sectional views showing still other embodiments, respectively, and FIGS. 6 and 7 are perspective views showing conventional plastic containers, respectively. 3a is an outer wall, 3b is an inner wall, 4 is a tubular part, 4c
is a welded part, 6 and 7 are containers, 9 and 10 are molds, 9a
9c is a concave cavity, 9c is a peripheral hollow molded cavity, 10a is a convex cavity, 10c is a peripheral welded part molded cavity, and 12 is a parison.

Claims (1)

[Claims] 1. A concave cavity 9a forming the outer wall 3a of the container 6, 7 to be molded;
Containers 6 and 7 to be molded located on the periphery of a
One mold 9 has a peripheral hollow molding cavity 9c that forms the tubular part 4 at the opening peripheral part of the mold 9, and faces the concave cavity 9a that forms the inner wall 3b of the container 6, 7 to be molded. A convex cavity 10a, and the outer wall 3a and the inner wall 3b near the opening periphery of the container 6, 7 to be molded by cooperating with the peripheral hollow molding cavity 9c located at the periphery of the convex cavity 10a. A peripheral welded part molding cavity 1 that forms a tubular part 4 at the opening peripheral part of the container 6, 7 to be molded by forming a welded part 4c that partially welds the two.
A preform consisting of a parison or two sheets of plasticized thermoplastic is placed between the mold 10 and the other mold 10 with Pressurized fluid is injected into the outer wall 3a and the inner wall 3.
A semi-finished product is formed by forming a hollow double-walled main body portion consisting of b and a tubular portion 4 formed at the periphery of its opening via a partial welding portion 4c, and the semi-finished product is molded into the molds 9 and 10. Take it out from
A method for manufacturing a plastic container having a main body having a single wall structure and having a tubular portion 4 at the opening periphery by cutting the inner wall 3b from the inside of the welded portion 4c of a semi-finished product.