JPH03274119A - Hollow molded resin form and hollowly molding method - Google Patents

Abstract

PURPOSE:To prevent generation of a thick-walled part in a molded form and to hold light weight and necessary strength by connecting both the flat side and the bent sides of a molded resin body via the turned parts and providing the hollow parts wherein thickness of resin is made nearly uniform to this molded resin body and providing partitions for comparting the respective hollow parts between the flat side and the bent sides to the turned parts. CONSTITUTION:A molded form 1 is formed into a square dish shape by equipping a plurality of bent sides 2 and bending the side ends of a nearly rectangular flat side 3 in one direction via the turned parts 7. Therefore a cavity having the square dish shape is provided to a mold. Resin is injected into this cavity and simultaneously gas is blown into this resin. Introduction of gas is performed from not only a gas introducing port 4 provided to the flat side 3 but also the gas introducing ports 5 provided at the end parts of the respective bent sides 2. Therefor the hollow parts 6 are uniformly formed in the whole molded form and the thick-walled layer of the molded form is uniformed. In other words, the thick-walled part is eliminated and sink is not caused at a time for cooling and solidification. Further the partitions 8 are naturally formed between the hollow part 6 of the flat side 3 and the hollow parts 6 of the bent sides 2 and contribute to increase of strength of the turned parts 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a hollow resin molded product in which a hollow portion is formed by injecting gas during injection molding, and to improvements in blow molding.

(Prior Art) Conventionally, when forming a hollow part in a resin molded product such as plastic, a molding method is known in which the hollow part is formed by injecting gas during injection molding. In this method, immediately after the resin is injected into the mold, gas is blown into the resin, and the portion into which the gas is blown is made into a hollow portion.

(Problem to be Solved by the Invention) However, in the conventional case, the shape of the molded product is such that a plurality of bent sides 52 are connected to a flat side 53 via a bent part 55 as shown in FIG. Sometimes, because the gas inlet 54 is located at one point in the center, the gas does not spread throughout the molded product 51, and the end portion 52a, which is not filled with gas, becomes particularly thick, which causes sink marks when it cools and solidifies. was there.

Furthermore, in order to avoid sink marks, restrictions have been placed on the shape, size, etc. of the molded product. Further, there was also a problem that the strength of the bending portion 55 of the hollow molded product 51 formed in this manner was not sufficient.

(Means for Solving the Problem) In order to solve the problem, the present invention provides a resin molded body in which a flat side and a bent side are connected via a bent part, with a hollow part in which the resin has a substantially uniform thickness. In the bending part, a partition wall was provided to partition each hollow part of the flat side and the bent side. In addition, in the forming method, gas injection ports are provided at the ends of each bent side, and gas is injected from these gas injection ports to form the structure.

(effect) The strength of the bending portion can be increased by the action of the partition wall.

Furthermore, by making the wall thickness substantially uniform, it is possible to reduce the weight. Also, by injecting gas from each corner edge, the wall thickness becomes uniform and no sink marks occur. Furthermore, the degree of freedom in selecting the shape of the molded product is increased, and even large-sized molded products can be molded.

(Example) An example of the method for blow molding a resin molded product of the present invention will be described based on the attached drawings.

FIG. 1 and FIG. 2 are a perspective view and a sectional view showing a state in which a hollow portion is formed according to the improved invention. That is, the molded product 1 to which the present invention is applied has a plurality of bent sides 2, and in the case of this embodiment, the side ends of the substantially rectangular flat sides 3 are bent in one direction via the bending part 7. It is bent into a rectangular plate shape. For this purpose, a mold (not shown) is provided with a rectangular plate-shaped cavity.

At the same time as the resin is injected into this cavity, gas is blown into the resin.
This is carried out not only from the gas inlet 4 of , but also from the gas inlet 5 at the two ends of each bent side. Therefore, as shown by the chain line in FIG. 1, the hollow portion 6 is formed uniformly over the entire molded product, and the thickness of the molded product is made uniform. In other words, compared to the conventional gas filling range, which was located at the chain line in Figure 3, this has been greatly improved.
There are no thick parts and no sink marks occur during cooling and solidification.

In addition, when formed in this manner, a partition wall 8 is naturally formed between the hollow part 6 of the flat side 3 and the hollow part 6 of the bent side 2, which contributes to increasing the strength of the bent part 7.

Further, in the case of the present invention, since there is no thick wall portion, the molded product is lightweight, and the cooling solidification of the molded product is also promoted. Therefore, productivity can be improved.

(Effects of the Invention) As described above, the hollow resin molded product of the present invention is lightweight and can sufficiently maintain necessary strength. In the blow molding method, the gas injection port is injected from each bent side, so no thick wall portions are formed in the molded product, and no sink marks occur during cooling and solidification.

Further, in the conventional blow molding method, the size of the molded product was limited to a certain size, but according to the present invention, it is possible to produce molded products of relatively large size, and the degree of freedom in shape design has also increased.

Furthermore, the cooling effect is enhanced, contributing to improved productivity.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a workpiece to which the present invention is applied, Fig. 2 is a cross-sectional view showing a state in which a hollow portion is formed according to the present invention, Figs. 3 and 4 show a conventional example, and Fig. 3 is a diagram of a workpiece. FIG. 4 is a perspective view and a sectional view showing a state in which a hollow portion is formed. In the figure, 2 and 52 indicate the bent side 4, 5.54 indicates the gas Z main population, 7.55 indicates the bent section, 6 indicates the hollow section, and 8 indicates the partition wall.

Claims (2)

[Claims] (1) A resin molded body in which a flat side and a bent side are connected via a bent part is provided with a hollow part in which the thickness of the resin is approximately uniform, and the bent part is provided with a hollow part on each of the flat side and bent side. A hollow resin molded product characterized by having a partition wall that partitions the parts. (2) In a hollow injection molding method in which a hollow part is formed by injecting gas during molding of a resin molded article having a plurality of bent sides, this method includes a hollow injection molding method in which a hollow part is formed at the end of each of the bent sides. A method for blow molding a resin molded product, characterized in that a hollow portion is formed by injecting gas from each gas injection port.