JPS6014562Y2 - Molded object - Google Patents

Description

[Detailed description of the invention] This invention is designed to prevent mold collapse (core collapse) during injection molding.
The present invention relates to a laminate that can prevent breakage, deflection, etc.

Generally, laminates such as boxes and cases that are integrally formed from synthetic resin are formed by injection molding.

In this injection molding, heated and molten synthetic resin material is injected into the cavity, a space formed between a stationary mold and a movable mold, at high pressure through a gate, and after cooling, the molded product is formed. Therefore, the quality of injection molded products largely depends on the quality of the mold.
Depending on the shape of the cavity, or in other words, the shape of the molded product, the high-pressure injection force used to inject the molten resin may cause the mold, especially the movable mold itself, to tilt, resulting in so-called core collapse, which can lead to uneven thickness and mold damage. occurs.

To explain this using figures, FIGS. 1a and 1b show a transparent cover for a counter integrally formed by injection molding.

This cover 1 is formed into a box shape consisting of a top plate 2A and four side plates 2B to 2E, all of which have the same wall thickness, and is open only at the bottom, with a concave display section 3 in the center of the top plate 2A.
However, the surface peripheral portion 4a of the top plate 2A is formed to protrude upward, thereby forming a picture frame shape.

Therefore, the inner peripheral edge 4b of the top plate 2A is formed in a concave shape.

2a and 2b show conventional molds used for injection molding the cover 1 shown in FIG. 1, 5 is a fixed side mold, 6 is a movable side mold, and 7 is a double mold. A cavity for molding the cover 1 formed by the molds 5 and 6, 8 is a runner provided in the stationary mold 5, and this runner 8 covers one side of the cavity 7 (for example, the side plate 2C of the cover 1). This runner 8 is located at the center of the lower part of the cavity 7c) to be formed.
and cavity 7 are communicated via gate 9.

In the initial stage, the molten resin injected from the gate 9 flows upward and in the left-right direction (in both directions) inside the cavity 7c forming the side plate 2C of the cover 1.

Therefore, at this initial stage, a pressure difference occurs between the left and right side surfaces of the movable mold 6, causing the movable mold 6 to be tilted to the left as shown by the two-dot chain line in FIG. 2A, causing deflection.

In extreme cases, the movable mold 6 may break.

In order to prevent such core collapse, a launch 8' is provided at the center of the stationary mold 5 as shown by the dotted line, or the number of gates is increased so that the molten resin flows almost simultaneously and uniformly throughout the cavity 7. It is also possible to do so.

However, in the former case, the gate 9' remains in the center of the top plate 2A of the cover 1, which not only causes problems in appearance but also requires many man-hours for finishing the gate.

In particular, in the case of a counter cover, the display part 3 of the top plate 2A
This is not preferable because it deteriorates the finished condition.

The latter method has the drawback that it is troublesome to make the mold and the manufacturing cost is high.

The present invention was developed in view of these circumstances, and has an extremely simple structure in which at least one of the four side plates forming the laminated body is made thicker than the other side plates depending on the gate position. Therefore, the present invention provides a laminated body that can be used without significantly changing the conventional mold structure and prevents the core from collapsing.

Hereinafter, the present invention will be explained in detail based on the drawings.

The laminated body according to the present invention is formed in the same way as the laminated body 1 shown in FIG. This is due to the fact that the side plate in front of the side plate that is last filled with molten resin during molding is made thicker than the other side plates.

That is, the wall thickness of the side plates 2B to 2E is determined by the position of the gate. For example, as shown in FIG. 3, when the gate 9 is shown in FIG. If only one piece is provided at the center of the lower part of the cover 1, the molten resin injected from the gate 9 into the cavity 7C will fill the cavities 7b and 7 that form the side plates 2B and 2D of the cover 1.
d and finally into the cavity 7e that forms the side plate 2E of the cover 1, the gap between the cavities 7b and 7d located immediately in front of this cavity 7e is set larger than that of the other cavities 7c and 7e. As a result, the side plates 2B and 2D of the cover 1 are formed thick.

In this case, if the interval between cavities 7c and 7e is t, then
The distance between cavities 7b and 7d is 1.5t to 2.5t. Set to OL.

Thus, by using such a mold, core collapse, deflection, etc. can be prevented.

That is, the molten resin injected from the gate 9 flows upward and in the left-right direction (both sides) of the cavity 7C, but the injection pressure from the gate 9 causes the movable mold 6 to move at the two points a in FIG. It is pushed to the left as shown by the chain line.

As a result, the resin inflow portion 10 of the cavity 7a forming the top plate 2A of the cover 1 is provided to protrude from the top periphery of the movable mold 6 to form the inner periphery 4b of the top plate 2A of the cover 1. It becomes narrower due to the protrusions 11 that are present.

Therefore, the molten resin flows into the wide cavities 7b, 7d.
It quickly flows into the cavity 7e, increasing the pressure within the cavity 7e, and returning the movable mold 6 to its initial position.

During injection and injection, the movable mold 6 is moved slightly to the left and right in this manner, but ultimately the tilting is prevented and the cavities 7a to 7e having a predetermined interval are maintained.

Therefore, uneven thickness, damage to the mold, etc. can be prevented, and a high-quality laminate can be formed.

FIG. 4 shows another embodiment in which a layered body is formed using a mold in which the gate 9 is provided on the lower side of the cavity 7c.

In this case, the molten resin injected from the gate 9 passes through the cavities 7d, 7e, and 7b, and finally fills the cavity 7c.
Only the distance between the cavity 7b located immediately before the cavity 7c and the other 3
It is set larger than the two cavities 7C97dg 7e.

In such a configuration, the movable mold 6 falls toward the cavity 7c in the initial stage, but since the pressure in the cavity 7c, which has a good vortex flow, quickly rises, the initial core fall is quickly alleviated, preventing deflection and metal molding. Prevent damage to the mold.

Therefore, also in this case, it is possible to obtain a high-quality laminate in which only the side plate 2C is thicker than the other side plates 2B, 2D, and 2E.

As explained above, the laminate according to the present invention is formed into a box shape with one side open, and the surface periphery of the surface facing the opening is formed in a convex shape, the inner periphery is formed in a concave shape, and Of the four side plates, the side plate located immediately in front of the side plate that is filled with molten resin last is made thicker than the other side plates, which prevents injection molding that is likely to occur when there is only one gate. It is possible to prevent the core from collapsing, deflection, and damage to the mold during manufacturing, and it is possible to produce a high-quality laminate.

Further, since the gate is provided on the open end side of one side of the laminated body, the appearance of the laminated body is not impaired, and the mold can be manufactured easily and at low cost.

[Brief explanation of drawings]

FIG. 1 shows an example of a molded article according to the conventional method and the present invention, in which a is a perspective view of the external appearance, b is a sectional view of the main part, and FIG. 2 is an example of the molded article shown in FIG. A conventional mold is shown, where a is a longitudinal cross-sectional view thereof, b is a cross-sectional view thereof, FIG. 3 is a cross-sectional view showing a mold for molding a molded article according to the present invention, and FIG.
The figure is a cross-sectional view showing another embodiment of the mold used for molding the molded article according to the present invention. 1...Cover (molded body), 2A...Top plate, 2B-2E...Side plate, 4a...
・Surface periphery, 4b... Inner periphery, 8...
...Runner, 9...Gate.

Claims (1)

[Scope of utility model registration request] In a box-shaped laminate made of synthetic resin with one side open, the surface of the laminate facing the opening has a convex peripheral edge and a concave inner periphery; Of the four side plates forming the laminate, the side plate immediately before the side plate that is last filled with molten resin and formed is formed to be thicker than the other side plates.