JPH11300817A - Manufacture of blow-molded product with hinge and blow-molded product with hinge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing blow-molded products with hinges easily and efficiently. SOLUTION: A resin parison P is suspended in a gap between the split halves of a die with a protrusion part for forming a hinge and these split halves are closed. Then a pressurized air is blown into one of plural hollow parts formed by sectioning with the pressure contact part of the parison P corresponding to the protrusion part for forming the hinge. Further, the pressurized air is sent into the adjacent other hollow part through a communicating hole opened in the pressure contact part. Next, blow-molded products removed from the die are bent at the pressure contact part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a blow molded article having an integrally formed hinge, and a molded article obtained in this manner.

[0002]

2. Description of the Related Art
In order to blow-mold a plastic product in which two or more hollow parts are flexibly connected by a hinge, at the time of molding, one part of the molded product is compressed into a thin wall to form a hollow part, and a needle is blown into each hollow part. (Yokobuki) to send air. Such a thin compression causes molecular orientation, and even with a thickness of 0.3 to 2 mm, a hinge that is extremely resistant to bending and pulling is formed. A mouth is required and a complicated mold must be used. Moreover, it is not easy to completely blow-mold all of the two or more hollow portions by the needle blowing method, and a high defect rate is also an issue.

[0003]

SUMMARY OF THE INVENTION The present invention comprises the following steps: 1) A resin parison is hung between split molds having a projection for forming a hinge, 2) a mold is closed, and 3) a mold for forming a hinge is formed. Pressurized air is blown from one of a plurality of hollow portions separated by a press contact portion of the parison corresponding to the protrusion, and pressurized air is sent to another adjacent hollow portion through a communication hole opened to the press contact portion, Next, 4) It is intended to provide a method of manufacturing a blow-molded product having a hinge by bending a blow-molded product removed from a mold at a pressure contact portion.

[0004] In the method of the present invention, a communication hole is opened in the press-contact portion of the parison corresponding to the hinge portion, and air blown into one hollow portion is sent into the other hollow portion from the communication hole, thereby connecting with the hinge. It has become possible to easily and efficiently blow mold a plastic product having a large number of hollow portions using a simple mold. The communication hole can be opened by inserting a pin at the same time as closing the mold, or can be opened by the wind pressure of pressurized air. Either one may be used, but the latter method is more preferable in terms of simplicity.

[0005] The position and number of communication holes opened in the press-contact portion of the parison are arbitrary, provided that a sufficient amount of pressurized air required for blow molding is supplied to all hollow portions. It can be appropriately selected according to the shape and size of the molded product. However, from the point of strength and operability,
It is preferable that at least one end of the press-contact portion is formed thick, and a communication hole is opened in the thick portion. In order to blow the pressurized air evenly and to perform blow molding successfully, it is more preferable that there are thick portions at both ends of the press contact portion, and a pair of communication holes are opened in those thick portions. In order to provide a thick portion in the press contact portion of the parison, the width of the protrusion provided on one or both sides of the split mold may be reduced.

The size and shape of the communication hole are not particularly limited, provided that the supply of pressurized air required for blow molding is achieved. If the communication hole is relatively small, the resin material in that portion is pushed away from one hollow portion to the other, allowing air to pass through, especially in the central portion. As a result, the same high hinge strength can be obtained as in the conventional method in which the material is compressed and oriented thin. When the communication hole is not opened beforehand, when the pressurized air is blown into one hollow body, the communication hole is usually opened at both ends of the press-contact portion by the wind pressure of the pressurized air. Therefore, it is possible to adjust the size of the communication hole by adjusting the thickness of both end portions. An appropriate size of the communication hole can be appropriately determined by those skilled in the art in consideration of the thickness, the tensile strength, and the bending strength of the hinge. In addition, as the shape of the communication hole, a flat communication hole along the longitudinal direction of the hinge is preferable because it has good flexibility and orientation is likely to occur. When the molded product has been cooled to an appropriate temperature, it is removed from the mold and bent at the hinge to obtain the final product. Although there is no particular limitation on the bending temperature, it is usually in a range of about 40 ° C. from a high temperature immediately after molding in consideration of easy operation,
When the temperature of the communication hole is 60 ° C. to 130 ° C., there is an effect that the orientation is further strengthened by bending, which is preferable. There is not much harm caused by the high temperature, but if it is too low, cracks may occur.

[0007] The present invention also provides a blow molded article having a hinge manufactured by the method of the present invention. Such products include all plastic products that can be manufactured by blow molding, such as tool boxes with hollows, large assembled hollow panels, reclining seats for child seats, and the like. As described above, the product obtained by the method of the present invention has an orientation at the hinge portion and has sufficient strength as in the case of the product manufactured by the conventional method.
The blow-molded article of the present invention has slightly thicker ends at both ends of the hinge, apparently from the manufacturing method. The communication hole in the thick portion may become a trace or disappear in the bending process after molding.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of the method of the present invention will be described with reference to the drawings. In FIG. 1, 1 is an extruder, 2 is a head, and 3 and 4 are a pair of split molds. Mold 3 and Mold 4 have contrasting concave cavities and mold 3
The inside has a suitable width and concave portions 5a at both ends so as to form a thin hinge portion in the cavity when the mold is closed.
And 5b are provided. A blow hole 6 is formed below the mold 3, 7 is a holder, and 8 is a blow port.

First stage: As shown in FIG. 1, a cylindrical parison P made of a molten resin is ejected from the head 2 and the blowing port 8 is raised to a suitable position below the parison P. Second stage: Next, when the molds 3 and 4 are closed as shown in FIG. 2, the parison is pressed against the projection 5 to form a thin hinge portion 9, which is divided into two hollow portions 10 and 11. At both ends of the hinge portion 9, thick portions 9a and 9b corresponding to the concave portions 5a and 5b at both ends of the protruding portion 5 are provided, and pressurized air is blown from a blow port 8 below one hollow portion 10. Communication holes 12a in the thick portions 9a and 9b,
12 b is opened, and pressurized air is blown into the other hollow portion 11.

Third stage: As shown in FIG.
Is opened, and the holding body 7 and the blowing port 8 are lowered, and the thick portions 9a, 9 having the communication holes 12a, 12b opened at both ends thereof.
b, two hollow parts 10, separated by a hinge 9 having b
11 is obtained. Fourth stage: After cooling to about 50 ° C., the mold is removed from the mold, and the upper and lower burrs are removed and bent from the hinge portion. FIG.
FIG. 3 is a perspective view of a molded product before bending. FIG. 5A is an enlarged cross-sectional view taken along the line aa of FIG. 4 passing through the thick portion 9a of the hinge 9 of the molded product, and the communication hole 12a is open. (B)
5 is an enlarged cross-sectional view of the communication hole 12a of the hinge 9 taken along the line bb. (C) is an enlarged view of a portion corresponding to (A) after being bent by the hinge 9. FIG. 6 is a perspective view of the reclining sheet manufactured by the above method.

As a result of comparing the strength of the hinge portion obtained by the above method and the strength of the hinge portion having the same shape and formed by the conventional needle blowing (lateral blowing) method, the following results are obtained.
It turned out that there was little difference.

[Table 1]

[0012]

As is apparent from the above description, according to the present invention, a blow-molded article having any number of two or more hollow parts connected via a hinge can be formed by only one blow-in operation. Since it can be manufactured by blowing pressurized air from the mouth (upper or lower blow), the mold is simple and economical, and blow errors are less likely to occur and the defective rate can be reduced. In addition, when air flows from one hollow portion to the other central portion through the connection hole of the press contact portion of the parison, the resin material in the central portion flows, whereby orientation is generated near the press contact portion, and a high hinge is formed. Strength is obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first stage of the method of the present invention.

FIG. 2 is an explanatory view showing a second stage of the method of the present invention.

FIG. 3 is an explanatory view showing a third stage of the method of the present invention.

FIG. 4 is an explanatory view showing a fourth stage of the method of the present invention.

5 is a partially enlarged view including a communicating hole portion of the hinge of the molded product shown in FIG. 4, (A) is a sectional view taken along aa,
(B) is a bb cross-sectional view, and (C) is a cross-sectional view corresponding to (A) after being bent at a hinge portion.

FIG. 6 is a perspective view of a reclining sheet manufactured by the method of the present invention.

[Explanation of symbols]

 P Parison 3, 4 Mold 5 Projection 9 Hinge 9a, 9b Thick part of hinge 10, 11 Hollow part 12a, 12b Communication hole

Claims (4)

[Claims] 1. The following steps: 1) Resin parison is hung between split molds having a projection for forming a hinge; 2) a mold is closed; 3) Pressing of a parison corresponding to the projection for forming a hinge. Pressurized air is blown from one of the plurality of hollow portions separated by the portion, and the pressurized air is sent into another adjacent hollow portion through a communication hole opened to the press contact portion; A method for producing a blow-molded article having a hinge formed by bending a blow-molded article at a pressure contact portion. 2. The method according to claim 1, wherein the communication hole is opened by wind pressure of pressurized air. 3. The method according to claim 1, wherein at least one end of the pressed portion of the parison is thick, and a communication hole is opened in the thick portion. 4. A blow-molded article having a hinge manufactured by the method according to claim 1.