JPS6213887B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection molded plastic container, and more particularly to a method for manufacturing an injection molded plastic container whose bodies are inclined so that they can fit together and which have stacking ribs on the outer peripheral surface of the mouth end.

In such plastic containers, the role of the stacking rib on the outer peripheral surface of the mouth end is to facilitate re-separation of the containers when several containers are stacked on top of each other to reduce the space occupied during transportation or other purposes.
The lower edge of the rib abuts the upper edge of the stacked containers so that a gap exists between the edges of the containers.

Conventionally, however, injection molding of this type of plastic container has been carried out using a mold in which the molding cavity of the body portion including the rim of the container is uniformly sloped, which has caused problems. In other words, in this conventional method, the mouth end of the molded product is deformed in a state where it is warped and squeezed inward from the body part following the mouth end due to cooling shrinkage during molding, and the diameter of the main body part is approximately 80 mm. Even in containers made of plastics with a high shrinkage rate such as polyethylene resin, the narrowed container rim due to the previous deformation is compressed by the body of the overlapping container, making it difficult to easily re-separate the containers. This leads to the inability to do so. Furthermore, even in the case of plastics whose shrinkage rate itself is not large, if the molding cycle is increased too much for economic reasons, the molded product will be released from the mold while cooling is insufficient, resulting in a higher temperature of the released molded product. As a result, large shrinkage and deformation may occur, resulting in the same inconvenience as described above.

For this reason, conventionally, stacking ribs are formed in such a manner that they extend beyond the zone where the inward deformation of the container mouth end occurs, and the stacking ribs are formed so that the inward deformation deformation of the mouth end of the container is located outside the overlapping area of the containers. That's what I do. With such long stacking ribs, containers cannot be stacked to a sufficient depth, and the space occupied by a large number of stacked containers is surprisingly large.

The present invention eliminates the drawbacks of the prior art and provides a method for manufacturing injection molded plastic containers in which short stacking ribs can fulfill their required role, thus requiring less space for stacked containers. It is intended to.

The method for manufacturing an injection molded plastic container of the present invention is a method for manufacturing an injection molded plastic container whose bodies are inclined so that they can fit into each other and which has a stacking rib on the outer peripheral surface of the mouth end, the container having a diameter of 15 to 100 mm.
Injection molding is carried out using a mold in which the molding cavity in the region corresponding to the container mouth end, which extends to a depth of It is characterized by

When a plastic container is molded using a mold with a molding cavity set to a mouth end with a specific depth and a specific angle of outward inclination, the mouth end of the molded product will continue to follow that part even if the shrinkage is large. There is no contraction further inward than the body, and therefore, when the molded containers are stacked together, the lip of the container does not come into contact with the body of the stacked containers. Therefore, the stacking ribs on the outer circumferential surface of the container mouth end can be short enough to accomplish the required role. Incidentally, according to the present invention, at least about 20% of the stacking ribs of conventional containers
It can be shortened.

Embodiments of the present invention will be described below with reference to the drawings. In the figure, 1 is a male mold for injection molding, and 2 is the same female mold as above. These molds have bodies that are inclined so that they can be fitted together, and a stacking rib 3 on the outer peripheral surface of the mouth end for forming a plastic container 4. It has a corresponding molded cavity 5. Container mouth end a of molded cavity 5
The corresponding portion 6 has a depth of 15 to 100 mm and is inclined outward by 1 to 2 degrees with respect to the corresponding portion 7 of the container body b following the portion a. The outward inclination of the portion 6 may be straight or arcuate. It is preferable that the portion 8 corresponding to the container mouth end flange c of the molding cavity 5 be inclined downward with respect to a plane perpendicular to the mold axis, corresponding to the outward inclination of the portion 6, and the angle thereof is 5. ~6 degrees is fine.

By injection molding a molded product according to a conventional method using the male mold 1 and female mold 2 having the molding cavities of the mouth end of the specified depth and the specified angle outward inclination, the container mouth edge is To obtain a plastic container in which the plastic container does not come into contact with the body of the stacked container.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing one embodiment of the present invention, and FIG. 2 is a partially enlarged view of the molded product shown in FIG. 1. 1 is male type, 2 is female type, 3 is stacking rib,
4 is a plastic container, 5 is a molded cavity, 6
7 is a portion of the molded cavity corresponding to the container mouth end; 7 is a portion of the molded cavity corresponding to the body continuing from the container mouth end;
a is the container mouth end, and b is the container body continuing from the mouth end of the container.

Claims (1)

[Claims] 1. A method for producing an injection molded plastic container whose body parts are inclined so that they can fit into each other and which has a stacking rib on the outer peripheral surface of the mouth end, the container having a diameter of 15 to 100 mm.
Injection molding is carried out using a mold in which the molding cavity in the region corresponding to the container mouth end, which extends to a depth of A method for manufacturing an injection molded plastic container characterized by: