JPS6058823A - Molding method of compound container - Google Patents

Abstract

PURPOSE:To mold the mouth rim of a compound container having a plane at a part of the side wall satisfactorily by providing a vacuum suction port at the part contacting the mouth of the side wall plane to perform an injection molding with a blank retained as sucked onto the inner wall of a die. CONSTITUTION:A vacuum suction port 25 is provided in a cavity 20 contacting the mouth at the blank part 13 composing the side wall plane 6 of a container to get the blank portion 13 tight of the inner wall of the cavity with the action of vacuum and then, a resin is injected. The resin is molded and bonded satisfactorily on the inner surface of the blank with little separation of the upper end thereof from the inner wall of the cavity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a composite container integrally formed from a sheet-like material and a resin, and particularly to a method for molding a composite container having a flat side wall portion.

Conventionally, in addition to paper containers and plastic containers, most of the container walls are made of paper or other sheet materials, and the rim,
2. Description of the Related Art Composite containers are known in which a bottom edge, an edge joint of a sheet-like material, and the like are hardened with resin. This composite container is
It is made by punching a sheet material such as paper into a predetermined shape and placing it in a predetermined position in an injection mold, and then injecting molten resin into the mold. Conventional composite containers have a cylindrical shape, a conical shape, etc., and have a circular mouth edge.

The inventors of the present invention made use of such a composite container structure to develop a new composite container in which a part of the side wall is a flat surface. After just injection molding, the resin injection cavity formed at the part corresponding to the rank mouth (upper end) is filled with the injection resin and cooled and solidified, thereby forming the mouth edge of the molded resin adhered to the inner surface of the upper end of the blank. When we prototyped a container equipped with this, we found that some of the resin at the edge of the flat surface of the container side wall also covered the outer surface of the blank and adhered to that area, not only staining the printed area on the outer surface of the blank but also distorting the shape of the container. It has been found that this causes damage to the appearance.

When we investigated the cause of this problem, we found that the upper end of the blank in the mold faces the recess of the core and is not restrained, and as a result, the blank may move away from the inner wall of the cavity on the flat surface, causing the injected resin to reach the outer surface of the blank. It was to go around. In addition, in a conventional container with a circular edge, the upper end of the blank is bent circularly and brought into contact with the inner wall of the cavity, so the restoring force of the blank itself causes the blank to adhere to the inner wall of the cavity, causing resin to be deposited on the outside of the blank. There was no rotation, and the container was well formed.

Accordingly, an object of the present invention is to provide a molding method that can satisfactorily mold a composite container having a flat portion on a portion of the side wall without causing defects on the mouth edge.

The present invention, which has been made to achieve the above object, is a method for molding a composite container with a flat side wall by mounting a sheet-like material blank in a mold and injection molding a molten resin, the method comprising:
It is characterized in that injection molding is carried out in a state in which the part of one mold that contacts the mouth of the side wall flat part is brought into close contact with the mouth by vacuum suction.

Explain.

FIG. 1 shows a composite container 1 made by the method of the invention.

The container 1 has a side wall 2, a bottom surface 3, and a large opening 4 at the upper end, and a flange 5 is formed around the outer periphery of the opening 4. The flange 5 is for joining a lid (not shown), and a projection 5A is formed on the top surface to ensure good joining.

The side wall 2 has an abbreviated horizontal section and is composed of a flat portion 6 and a large curved surface 7. The container 1 has a lip portion surrounding the opening 4, support portions B on both sides of the flat portion 6, and a blood portion C surrounding most of the bottom surface 3, and these portions ASB and C are made of injection resin. The rest is made of blanks of sheet material. FIG. 2 shows a blank 10 of sheet-like material, for example paperboard, from which the container 1 is constructed. The blank 10 is punched out in the shape shown after a predetermined printing, and includes a portion 11 forming the bottom surface 3 of the container and a fold I! A portion 13 that is connected via a line 12 and forms the flat portion 6 of the side wall of the container, and a portion 13 that is connected via a fold line 14 and forms a flat portion 6 of the container side wall;
and a portion 15 forming a curved surface γ of the wall. As shown in FIG. 3, this blank 10 is set at a predetermined position in an injection mold having a cavity 20, a core 21, a stripper plate 22, etc. The portion A1, the support portion BS, and the bottom edge portion C are molded, and at the same time, the mutually adjacent edges of the blank are bonded with molding resin to form the container 1 shown in FIG. 1.

The mouth rim A of the container 1 is formed by the recess 2.3 formed in the part of the core 21 facing the plank ring and the recess 24 formed in the cavity 20, and is therefore joined to the upper end surface and inner surface of the blank. It is something that Hollow 2
3 is formed around the entire circumference of the core 21, and as shown in FIG. 4 and FIG. By the way, since the blank portion 13 is flat as can be clearly seen from FIG. 5, even if the blank is pressed against the inner surface of the cavity 20 by the support surface 23A below the recess 23 as shown in FIG. As shown by the two-dot chain line, there is a depression 2.
3 may tilt inwards and separate from the cavity inner wall. If resin is injected in this state, the resin will also cover the outer surface of the blank and adhere to that area, spoiling the appearance of the finished container. Therefore, in the present invention, a vacuum rJ&σ1025 is provided in the cavity 20 that contacts the mouth of the blank portion 130 that constitutes the side wall flat portion 6 of the container, and a vacuum from an external vacuum source (not shown) is applied to the blank portion 13. It is brought into close contact with the inner wall of the cavity, and resin is injected in this state. In this way, since the blank is suctioned and held on the inner wall of the cavity by the vacuum suction port 25, the upper end of the blank hardly separates from the inner wall of the cavity, and the resin is well molded and bonded to the inner surface of the blank. After injection molding and subsequent cooling and solidification, the vacuum applied to the vacuum suction port 25 is turned off, the core 21 is pulled out from the cavity 20, and the molded container is removed from the core by the stripper plate 22. Here, the position where the vacuum suction port 25 is formed is preferably a position facing almost the center of the mouth of the flat side wall part, but it may be changed as necessary. May be placed.

In the above embodiment, a blank is brought into contact with the cavity 20 and a depression for resin injection is formed in the core, but the present invention is not limited to this, and the present invention may also be applied when a blank is brought into contact with the core and a depression is formed in one cavity. Applicable.

As described above, the present invention provides a vacuum suction port in the part of one mold that contacts the mouth of the flat part of the side wall of the container, and uses the vacuum suction port to suck the blank against the inner wall of the mold while holding the blank. Since it is injection molded, the injected resin does not spread to the back side of the planter and is well adhered to one side, making it possible to manufacture a composite container with a good appearance.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a composite container made by the method of the present invention, Fig. 2 is a front view of a blank used in the composite container of Fig. 1, and Fig. 3 is an injection molding mold used in carrying out the method of the present invention. 4 is an enlarged view of section E in FIG. 3, and FIG. 5 is a sectional view taken along the line FF in FIG. 4. DESCRIPTION OF SYMBOLS 1... Composite container 2... Side wall 3... Bottom surface 4... Opening part 5... Flange 6... Flat part 7... Curved surface 10... Blank 20... Cavity ( #Mold) 21...Core (male mold) 23.24...Indentation 25...Vacuum suction port agent Patent attorney Kyo Matsu 3 Figure 1 2rf! J Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] In a method of molding a composite container with a flat side wall by mounting a sheet material blank in a mold and injecting two molten resins, the portion of one of the molds that contacts the mouth of the flat side wall. A method for molding a composite container, characterized in that a 10" vacuum suction is provided in the mold, and the blank is injection molded in a state in which the blank is brought into close contact with the mold by vacuum suction.