JPS6027563B2 - How to make plastic containers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a substantially rectangular plastic container in which a main body and a lid having a double wall structure are integrally connected by a hinge.

As shown in FIG. 2, a convex cavity 14a is formed from the subordinate
, 15a and the concave cavities 14b, 15b, and pressurized fluid is blown into the parison 12 to form the main body and the lid, and the compression cap in the mold 13 is extruded. A method for manufacturing a plastic container in which a thin hinge is integrally formed by compressing a parison sandwiched between tees is already known, as disclosed in Jikko No. 49-18748.

Since the main body and lid of the plastic container obtained by the above manufacturing method are constructed with double walls, the plastic container has excellent protection for stored articles and is used as a variety of packaging containers. However, when attempting to obtain a substantially rectangular plastic container using the sub-bottom manufacturing method, the following problems arise.

1 When the parison is extruded and the mold is closed, the parison 12 is bent with the interval Hz between the convex cavity 14a side wall and the concave cavity 14b side wall being extremely narrow, and the parison 12 at the bent portion is fused. However, it becomes difficult to expand the parison 12 into a shape that corresponds to the cavity, and even if the parison 12 is molded, there is a risk that uneven thickness may appear on the container.

This problem becomes particularly noticeable when trying to obtain a container with narrow opposing inner and outer walls. 2. When extruding the parison and closing the mold, the parison 12 does not contact the concave cavity 14b which initially contacts the convex cavity 14a, so the blow ratio of the parison on the convex cavity 14a side and the concave cavity 14b is lower. In addition, since the outer wall of the container is formed by a parison having a length of L2, there is a phenomenon that the inner wall of the obtained container is thick and the outer wall is thin.

This problem is particularly noticeable when trying to obtain square containers or deep-bottomed containers. However, in order to take advantage of the hollow double-walled structure and increase the protection of stored items, it is preferable to form the inner wall thin, and to increase the strength of the container, it is preferable to form the outer wall thick. , the above-mentioned tendencies are completely contrary. In addition, when the parison comes into contact with the cavity, the parison sticks and does not slide to the corner of the concave cavity where the blowing ratio is high. Become.

The present invention solves the problems of the above-mentioned subordinate columns, and provides a substantially rectangular structure in which a main body with a double wall structure consisting of an inner wall and an outer wall and a lid body are integrally connected by a hinge. In a method for manufacturing plastic containers, the inner surface of one of the molds has a substantially triangular cross section with the long side of the mold fitting, and the short side is concave from the mold matching surface. A compression cavity is arranged between the two concave cavities, upper and lower, and a compression cavity is arranged between the concave cavities. A parison is extruded between a split-type mold having two convex cavities and a compression cavity disposed between the convex cavities, and as the mold is closed, the parisons are extruded between opposing convex cavities at approximately equal intervals. The parison is deformed along the space surrounded by the shaped cavity and the concave cavity, and the parison is advanced to the vicinity of the corner portion which is approximately the center of the concave cavity, and the concave cavity where the tips of the convex cavities face each other. The mold is closed so that it is located at the corner, which is approximately the center of the Regarding the manufacturing method of plastic containers in which the main body and the lid of the double-walled structure are formed by a convex cavity and a concave cavity that face each other, the parison does not unexpectedly fuse when the mold is closed. The purpose is to form the inner and outer walls with uniform thickness without appearing on the container.

The details will be explained below based on the drawings.

FIGS. 1A and 1B are process diagrams showing the manufacturing method of the present invention, in which 1 is an extrusion head, 2 is a parison, and 3 is a split mold. Two upper and lower concave cavities 4b recessed from the mold mating surface, which have a substantially triangular shape with the mating surface as the long side, and the short side is inclined at an angle of approximately 45 degrees to the mold mating surface, for example; 5b, and a compression cavity 6b is arranged between the concave cavities 4b, 5b, and the concave cavities 4b, 5b are arranged on the inner surface of the other mold.
Concave cavity 4b from the mold mating surface corresponding to the shape of
, 5b side has two convex cavities 4a, upper and lower.
, 5a and a compression cavity 6a between the convex cavities 4a, 5a to form a split-type mold 3.

Furthermore, when the mold is closed, the tips of the convex cavities 4a, 5a are located at the corners, which are approximately the centers of the opposing concave cavities 4b, 5b. Further, 7 is a blowing needle. Next, the manufacturing method of the present invention is illustrated in FIGS. 1 and 2.
This will be explained based on the diagram.

As shown in FIG. 1, a thermoplastic plastic such as polyethylene or polypropylene melt-kneaded by an extruder (not shown) is extruded from an extrusion head 1 as a cylindrical parison 2, and then a mold 3 is closed. At this time, if the lower end of the extruded parison 2 is sealed and a pressurized fluid such as compressed air is injected into the parison 2 from inside the extrusion die 1 and pre-blown, the parison 2 will be closed. 2 will not unexpectedly fuse when the mold is closed, and the inner and outer walls can be formed to have a uniform thickness. As the mold is closed, the parison 2 is divided into convex cavities 4a, 5a and concave cavities 4a facing each other at approximately equal intervals.
, 5a along the space surrounded by the parison 2.
Enter the concave cavities 4b, 5b to the vicinity of the corners, which are approximately the centers of the concave cavities 4b, 5b. Close the mold. Therefore,
The interval between the tips of the convex cavities 43, 5a and the upper ends of the opposing concave cavities 4b, 5b does not become extremely narrow, and the parison 2 is closed along the opposing cavities at approximately equal intervals. To go. Furthermore, since the cavities 4a, 4b, 5a, and 5b are constructed in an oblique manner, the length L of the parison 2, which is gripped by the cavities, can be made longer than the length L2 of the conventional parison 12. This prevents the outer wall corners of the manufactured approximately rectangular container from becoming extremely thin. Next, as shown in FIG. 1B, after the parison 2 is closed with a mold 3, the parison 2 located in the spaces of the opposing cavities 4a, 4b and 5a, 5b is heated with compressed air or the like from the blowing needle 7. Pressurized fluid is injected, and the parison 2 expands into a shape corresponding to the cavity, forming the main body 9 and the lid 10.

Also, the parison 2 sandwiched between the opposing compression cavities 6
is compressed to form a hinge 11 whose thickness is less than the thickness of the adjacent parison wall. After cooling, the mold 3 is opened, the molded product is taken out, excess burrs are removed, and the manufacturing process is completed. 3A and 3B show a substantially rectangular plastic container obtained by the manufacturing method of the present invention, and the plastic container 8 consists of a main body 9 and a lid 10 having a double wall structure, and the mating surfaces thereof are arranged diagonally. In addition, the main body 9 and the lid 1 are integrally connected by a bendable hinge 11 formed by compressing the adjoining wall thinner. Incidentally, the inner recesses 9a and 10a of the main body 9 and the lid 10 can be arbitrarily formed into a shape corresponding to the external shape of the stored article. Furthermore, as shown in FIGS. 3A and 3B, the mating protrusion 16 may be integrally provided on one outer wall 10b of the mating surface facing the hinge 11 via the hinge, and the competing member 17 may be integrally provided on the other outer wall 9b. Out. As described above, according to the manufacturing method of the present invention, the parison does not unexpectedly fuse when the mold is closed, and it is possible to obtain a substantially rectangular plastic container with uniform inner and outer wall thicknesses.

[Brief explanation of the drawing]

Figures 1A and B are cross-sectional views of a mold showing the manufacturing method of the present invention, Figures 2 A and B are cross-sectional views of a mold showing the manufacturing method of a subordinate column, and Figures 3 A and B are cross-sectional views of a mold showing the manufacturing method of the present invention. FIG. 2 is a perspective view and a cross-sectional view of a plastic container obtained in . 1...Extrusion head, 4a, 5b...Convex cavity, 2...Parison, 4b, 5b...
...Concave cavity, 3...Divided mold,
6... Compression cavity. Figure 1 (A) Figure 1 (B) Figure 2 (A) Figure 2 B) Figure 3 (A) Figure 3 (B)

Claims (1)

[Claims] 1. In a method for manufacturing a substantially rectangular plastic container in which a main body and a lid having a double-walled structure consisting of an inner wall and an outer wall are connected together with a hinge, the inner surface of one of the molds has a metal cross section. Two concave cavities (upper and lower) recessed from the mold mating surface, each having a substantially triangular shape with the mold mating surface as the long side and the short side inclined with respect to the mold mating surface, and a compression cavity between the concave cavities. A split type mold with two upper and lower convex cavities protruding from the mold mating surface corresponding to the shape of the concave cavity and a compression cavity arranged between the convex cavities on the inner surface of the other mold. extruding a parison between molds; as the mold is closed, deforming the parison along a space surrounded by a convex cavity and a concave cavity that face each other at substantially equal intervals;
The parison is advanced to the vicinity of the corner, which is approximately the center of the concave cavity, and the mold is closed so that the tip of the convex cavity is located at the corner, which is approximately the center of the opposing concave cavity. The parison sandwiched between the compression cavities is compressed to form a thin-walled hinge, and pressurized fluid is blown into the parison, and the convex cavity and concave cavity facing each other form a double-walled main body and lid. A method for producing a plastic container, characterized by forming a plastic container.