JPH071495A - Injection-molded article - Google Patents

Abstract

PURPOSE:To obtain a resin-molded article good in shape and quality without causing any strain that may curve side walls of the molded article by providing thin-wall recesses in the peripheral edge portion of a bottom wall of the same in a vessel-shaped injection-molded article which is formed of a bottom wall and side walls and whose upper face is open. CONSTITUTION:A case 11 made of resin, which is injection-molded into a vessel shape, consists of a rectangular bottom wall 12 and respective side walls 13 to 16 provided at four sides of the bottom wall 12 and standing in an orthogonal direction from respective side edges thereof, and they are formed into one body. Recesses 17 provided inside the bottom wall 12 to make the thickness (a) thereof thinner are formed discontinuously at predetermined intervals along the side edges of the bottom wall. By forming the thin-wall recesses 17, which accelerate cooling speed, at joint portions between the bottom wall 12 and each of the side walls 13 to 16, where cooling is slowest, shrinkage of the side wall 13 to 16 by cooling occurs almost simultaneously from the upper side edge portions and from the lower side edge portions at the time of air cooling of the case 11 after mold release. By this method, the resin-molded article good in shape and quality can be obtained without causing any strain to the respective side walls 13 to 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection-molded article obtained by molding, for example, a container shape having an opening on its upper side surface by a resin injection means.

[0002]

2. Description of the Related Art For example, as shown in FIG. 1, a container having an upper surface opening composed of a rectangular bottom wall 1 and four side walls 2, 3, 4, 5 standing upright from respective edges of the bottom wall 1. When molding a shaped article by injection molding means using resin as a molding raw material, after closing a predetermined injection molding die, a predetermined resin raw material is injected into the mold, and then the injection molded article is injected from the injection molding die. The product is released from the mold, and the molded product is cooled and cured by the outside air to obtain the desired molded product.

[0003]

However, in such a resin molded product, since the cooling from the outside of the resin molded product is rapid from the outside of the resin molded product during cooling after releasing from the mold, as shown by the solid line in FIG.
Each of the side walls 2 to 5 causes a distortion that bends inward.

That is, considering the cause of the inwardly curved distortion in each side wall, as shown in FIG. 3, a resin molded product having a side wall 5 standing upright from the edge of the bottom wall 1 is formed. When the outside air is cooled after the mold is released, the outer side surface of the side wall 5 has a better heat dissipation effect than the inner side surface, and the outer side surface shrinks more quickly.
Since the cooling of the upper side edge portion b of the side wall 5 is faster than that at the connection portion a with the bottom wall 1, the side wall 5 is distorted as shown by the solid line, which causes a problem that a product defect occurs.

[0005]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to such a conventional problem, and when injection molding a container-shaped resin molded product having an open upper surface, a bottom wall and each side wall are formed. It is an object of the present invention to provide an injection-molded product in which a thin portion for increasing the cooling rate of the corner portion is formed inside the formed corner portion to prevent the occurrence of distortion of each side wall.

More specifically, the present invention is described in detail. A container-shaped container having a bottom wall and a side wall formed upright from the peripheral edge of the bottom wall and having an open top is injection-molded from a resin. At the time of cooling after releasing the container from the mold, in order to cause cooling shrinkage between the upper edge portion of the peripheral wall and the lower side portion of the peripheral wall, that is, the bottom wall connecting portion, at about the same time. In addition, the thin wall portion is provided at each peripheral portion of the bottom wall.

Therefore, by providing the thin portion,
In each side wall, the degree of cooling shrinkage between the upper part of the side wall and the lower part of the side wall is kept balanced, whereby the side wall surface is not distorted, and a resin molded product having good shape quality can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in FIGS.

Reference numeral 11 denotes a container made of resin injection-molded into a container shape. The container 11 has a rectangular bottom wall 12 and four directions standing upright from respective edges of the bottom wall 12 in four directions. It is a vessel-shaped container in which the side walls 13, 14, 15, 16 are integrally formed.

The greatest feature of this embodiment is that the bottom wall 12
A concave portion 17 for thinning the wall thickness a of the bottom wall 12 is formed inside the corner bottom wall 12 formed by the side walls 13, 14, 15, 16 along the edge of the bottom wall 12. It is formed discontinuously at intervals.

Therefore, according to this embodiment, in the resin-molded container 11, at the corners where cooling is slowest when the container 11 is air-cooled after mold release, that is, at the connecting portion between the bottom wall 12 and each side wall. By forming the thin recess 17 for promoting the cooling rate, the side walls 13, 1
In Nos. 4, 15 and 16, the cooling shrinkage from the upper side edge portion and the cooling shrinkage from the lower side edge portion of each side wall occur at substantially the same time, so that the side wall is not distorted. A resin molded product of good quality can be obtained.

In the above-mentioned embodiment, the thin recess 17 is provided discontinuously along the edge, but the invention is not limited to this.
For example, it may have a continuous groove shape.

Further, in the above embodiment, the vessel-shaped resin container 1
Although 1 has been described as a rectangular shape, the present invention is not limited to this, and the same operational effect can be obtained even in the case of a circular container provided with a peripheral wall standing upright on the periphery of a circular bottom wall.

[0014]

INDUSTRIAL APPLICABILITY As described above, the present invention provides a container-shaped injection-molded product having a bottom wall 12 and side walls formed upright from the peripheral edge of the bottom wall 12 and having an open upper surface. Since this is an injection-molded product in which the thin-walled forming portion 17 is provided along the peripheral corner portion, according to this, the injection-molded molded product is removed from the upper edge portion of the peripheral wall during air cooling after release from the mold. It is said that the cooling shrinkage of No. 1 and the cooling shrinkage from the lower side edge portion are generated at substantially the same timing, and thereby the distortion that is curvedly formed on the side wall does not occur, and a resin molded product with good shape quality can be obtained. effective.

[Brief description of drawings]

FIG. 1 is an explanatory view of a conventional injection molded product.

FIG. 2 is an operation explanatory view of a conventional injection molded product.

3 is a partial cross-sectional view taken along the line AA in FIG.

FIG. 4 is a perspective view showing an injection-molded article according to an embodiment of the present invention.

FIG. 5 is an enlarged perspective view of an essential part of the embodiment of the present invention.

6 is a partial cross-sectional view taken along the line BB in FIG.

[Explanation of symbols]

 11 ... Resin container 12 ... Bottom wall 13 ... Side wall 14 ... Side wall 15 ... Side wall 16 ... Side wall 17 ... Thin wall forming part

Claims (1)

[Claims] 1. A container-shaped injection-molded product having a bottom wall (12) and a side wall formed upright from the peripheral edge of the bottom wall (12) and having an open top surface, wherein the peripheral edge angle of the bottom wall (12) is An injection-molded article, characterized in that a thin-walled forming portion (17) is provided along the portion.