JPS5854018B2 - Manufacturing method for blow molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a blow-molded product, and in particular to a method for effectively preventing the generation of gaps in a hollow blow-molded product having a metal fitting portion that protrudes to the outside. It's about how to get it.

Traditionally, blow molding has been widely used as a method suitable for manufacturing hollow molded products, and for example, headrest inserts (core bodies) as shown in Fig. 1 have also been manufactured using this blow molding method. ing.

Therefore, in the case of a hollow molded product such as a headrest insert in which a part of the metal fitting 2 protrudes outside from the inside of the molded product main body 1, the metal fitting part and the molded product main body part may separate due to shrinkage of the molded resin after molding is completed. There is a problem that a gap occurs between the two.

That is, as shown in FIG. 2 apb, immediately after blow molding, the metal fitting part 2 and the molded product main body part 1 are in close contact with each other, but after a certain period of time and after the molding resin has shrunk, the metal fitting part A gap A is generated between the molded article body portion 1 and the molded article body portion 1.

This is because it is a molded product with a hollow interior, and the metal fitting 2 to be inserted has a rigidity greater than the shrinkage force of the resin, so it does not deform or move.

In particular, such a gap A becomes conspicuous when a plurality of metal parts 2 protrude from the molded product main body 1 as shown in FIG.

In a molded product with such a gap A, liquid or the like will enter the molded product. For example, in the case of the headrest insert, urethane raw materials may enter during molding of the final product, the headrest. That's what I'm doing.

For this reason, in the past, as a measure to suppress the occurrence of the gap A, attempts have been made to lengthen the cooling time after blow molding to cool the molded product gently, thereby minimizing shrinkage as much as possible. However, this is not an essential measure to eliminate the gap, and results in an increase in molding time.

The gap A between the molded product main body part 1 and the metal fitting part 2, which still occurs even after taking such measures, is filled with a filler or pasted with adhesive tape to prevent liquid from entering. However, such operations inherently increase man-hours and costs, and are unreliable.

The present invention was made against this background, and its purpose is to provide a blow-molded product that can essentially prevent the occurrence of front and rear gaps. .

In order to achieve this objective, the present invention ('!.

When manufacturing a hollow blow-molded product having a metal fitting part protruding to the outside, the outer periphery of the metal fitting part protruding outward from the molded product body is covered over a predetermined length from the molded product body, and the base on the side of the molded product body is Blow molding is performed so that the metal fitting covering part, which has a thinner part, is formed integrally with the molded product body, and the shrinkage of the molded product body that occurs after the molding is completed is absorbed by the deformation of the thin walled part of the metal fitting covering part. However, a gap that communicates the inside and outside of the molded product main body is prevented from occurring in the metal part.

Thus, according to the present invention, the predetermined metal fitting covering portion is integrally blow-molded with the molded product body at the same time as the molded product body, and the metal fitting portion protruding from the molded product body is covered over a predetermined length. Therefore, even if the metal part and the molded product body through which it penetrates are separated due to shrinkage of the molding resin constituting the molded product body, the thin part of the metal fitting covering part will remain intact. is easily deformed and effectively absorbs the shrinkage, so that no gap is created that communicates the inside and outside of the molded product body.

More specifically, as shown in FIG. 3, the present invention provides a metal fitting portion 20 that protrudes outward from the hollow blow-molded product main body 1 and is in close contact with the base outer periphery over a predetermined length and height t. The metal fitting covering portion 3 is provided integrally with the molded product main body 1.

As shown in FIG. 4a, this metal fitting covering part 3 is composed of a thick end part 3a and a thin middle part 3b, that is, a base part on the molded product main body 1 side. The thin part immediately continues to the first part of the molded product body.

In short, the present invention is intended to mold such a metal fitting covering part 3 at the same time as the blow molding of the molded article main body 1, and FIG. 4a shows the state immediately after the blow molding.

However, in the case of a blow molded product provided with such a metal fitting covering part 3, if it is completely cooled after molding, the shrinkage of the molding resin similar to the conventional one will be caused in one part of the molded product body, and the body will shrink. Even if a gap A' is created due to separation between the part and the metal fitting part, the thin part 3b of the metal fitting covering part 3 deforms and absorbs the shrinkage, as shown in FIG. Since it does not extend to the thick part 3a at the tip, the thick part 3a is always in close contact with the periphery of the metal fitting part 2, and there is no gap between the inside and outside of the molded product body. There are no gaps that would allow communication.

The metal fitting covering portion 3 can be easily formed during blow molding by using a mold having a shape corresponding to the shape of the metal fitting covering portion 3.

That is, as shown in FIG. 5, the mating portions of the two-split blow molding molds 5a and 5b on which the metal fittings 2 are inserted and arranged are respectively aligned with the molding side of the molded product body 1 ( It is composed of a thin part forming part 6 a p 6 b % recessed thick part forming part 7 aa7bs which protrudes toward the metal fitting 2 side (downward in the figure), and resin cut parts 8 a and 8 b that are pressed against the metal fitting 2 surface. The two molds 5a and 5b are clamped together, and the parison (resin extrusion) 9 guided around the metal fitting 2 is compressed by these molds to form the target thin-walled part. 3b is the mold 5a.

5b, and the thick portion 3a is similarly formed by the thick portion forming portions 7a and 7b.

Further, FIG. 6 asb shows an example of a blow molding method using the blow molding molds 5a and 5b having the mold mating portion B shown in FIG.

First, in the state shown in FIG. 6a, the parison 9 extruded from a suitable extruder is lowered from above and reaches the position where it wraps around the set metal fitting 2, and as shown in FIG. 5a and 5b will be mold-clamped.

After this mold clamping is completed, air is blown from an air pipe 10 inserted and placed inside the parison 9 at a position different from that of the metal fitting 2, thereby expanding the parison 9 and forming the molds 5a and sb. By being pressed against the product, a molded product main body 1 having a predetermined shape is formed.

Note that the metal fitting covering portion 3 having the thin wall portion 3b according to the present invention
is formed by the above-mentioned mold clamping, and demolding is performed according to a conventional method.

Therefore, if the method of the present invention is followed in which such a metal fitting covering part is molded at the same time, there will be no gap between the metal fitting part 2 and the blow molded product body 1, which communicates the inside and the outside, so that liquid will not flow into the inside of the molded product. Therefore, conventional measures for preventing such intrusion, such as the use of fillers and adhesive tapes, filling and pasting operations, etc., can be completely eliminated, and the process This made it possible to significantly simplify the process.

In addition, according to the present invention, it is not necessary to adopt a long cooling time as in the past in order to reduce shrinkage of the molded product body 1, and the cooling time may be shortened to induce shrinkage. This has made it possible to shorten the time (one cycle) and, in turn, increase productivity.

Furthermore, in the present invention, since the metal fitting covering part is formed from a part of the same material at the same time during blow molding, there is no need to sacrifice special man-hours or use special materials. There are good advantages.

These advantages have made it possible to effectively reduce the cost of hollow blow-molded products, especially headrest inserts, while ensuring reliable and complete protection against liquid intrusion.

In addition to the above-mentioned specific examples, the present invention can be modified and improved in various ways based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

In addition, the length of the metal fitting covering part according to the present invention formed at the base of the metal fitting part protruding from the molded product main body; The length and the like are appropriately determined depending on the amount of shrinkage of the molding resin.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing a conventional headrest insert;
FIG. 2 asb is a sectional view of the main part showing the state immediately after blow molding and after complete cooling, FIG. 3 is a perspective view of the main part of the headrest insert obtained by the method of the present invention, and FIG.
Figures aj and b are sectional views of main parts showing the state immediately after blow molding and after complete cooling, respectively. FIG. 5 is an explanatory cross-sectional view showing -fll of a mold structure capable of forming a metal fitting covering portion, and FIGS. 6 a and 6 b are cross-sectional views each showing an example of a blow molding process according to the present invention. The molded product body, 2: Metal fitting part, 3: Metal fitting covering part, 3a:
Thick part, 3b = thin part, 5 a p5b nib blow mold, 6a, 6b: thin part forming part, 7a, 7b: thick part forming part, 8a, 8b: resin cutting part, 9: parison, 10: air pipe.

Claims (1)

[Scope of Claims] 1. When manufacturing a hollow molded product in which a part of the metal fitting protrudes from the inside of the molded product to the outside by blow molding, The molded product body is formed by blow molding so that the metal fitting covering part that covers the entire length and has a thin base portion on the side of the molded product body is integrally formed with the molded product body, and the molded product body that is formed after the molding is completed. A method for manufacturing a blow molded product, characterized in that the shrinkage of the metal fitting is absorbed by deformation of a thin walled portion of the metal fitting covering portion, so that no gap is generated in the metal fitting portion that communicates the inside and the outside of the molded product body. .