JPH0768586A - Manufacture of setting up type box - Google Patents

Abstract

PURPOSE:To manufacture a setting up type box at a low cost, and enable colors, patterns, characters, textures, and so forth to be varied on the article with ease by forming the setting up type box into a developed planar shape through injection molding or injection compression molding, and folding it along the folding lines for joining respective joint surfaces each other. CONSTITUTION:A mold cavity is made into a configuration corresponding to the developed planar shape of a setting up type box, and with the use of a mold having thinner parts than others in the parts corresponding to the folding parts 12a-12d of the setting up type box, infection molding or infection compression molding is carried out. The semimanufactured item obtained is folded and tentatively fabricated along the folding parts 12a-12d so as subsequently to stick the joint parts such as joint pieces 14, 16 each other and the superimposing surfaces of the main body 12. Besides, with the parts corresponding to the main parts 12 of the mold partially formed into an insertion, patterns, characters, textures and the like formed on the surface of the item can easily be changed by exchanging the insertion appropriately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a prefabricated box.

[0002]

2. Description of the Related Art As a conventional method for manufacturing an assembling box body such as a video cassette storage box, a resin sheet such as a polypropylene sheet having a predetermined wall thickness is prepared for each required color and designated. The colored resin sheet is punched into a predetermined flat plane shape by a punching press, and then the folds of the bent portion, patterns, letters, grain, etc. are pressed into a semi-finished product, and then the bent portion is bent to temporarily assemble, and then By adhering the joints, they are assembled into a three-dimensional box (completed product).

[0003]

However, in the conventional method of manufacturing a prefabricated box as described above, not only is there a large number of working steps, but also a considerable amount of edge is removed from the resin sheet in the first punching press working. Since the material is released, there is a problem that the yield decreases and the product price increases. In addition, it is necessary to recycle the mill ends to protect the environment, which increases the cost of recycling. In addition, a relatively large storage space is required to store the resin sheet for each color, which increases the storage cost of the material. The present invention aims to solve such problems.

[0004]

The present invention solves the above-mentioned problems by injecting a molten resin into a mold cavity corresponding to a predetermined developed plane shape to form a semi-finished product box. That is, according to the method of manufacturing the prefabricated box body of the present invention, the prefabricated box body is formed into a shape corresponding to the developed plane shape, and the portion corresponding to the bent portion of the prefabricated box body is formed thinner than other portions. Injection molding or injection compression molding is performed using a molding die having a mold cavity that has been formed, and then a semi-finished product having a developed plane shape is taken out from the molding die, and the semi-finished product is provisionally assembled by bending along the folds, Next, the joined surfaces of the semi-finished products are joined together to obtain a finished product. The assembly-type box body to be molded is a video cassette storage box, the resin material used is polypropylene of MI20 to MI70, and the gate of the molding die is a pinpoint gate opening toward the center of the mold cavity. , The wall thickness of the bent part of the assembled box is 0.15 mm to 0.3
It is good that it is 0 mm. Furthermore, the injection pressure is 900 kg /
cm ² or more and 2000 kg / cm ² or less and the injection rate is 500 cm ³ / sec or more and 1300 cm ³ / se
It is preferably c or less.

[0005]

[Operation] After injection molding or injection compression molding is performed using a mold having a mold cavity corresponding to a predetermined plane shape, a semi-finished product having a plane shape is taken out from the mold and the gate is formed from this. By separating the parts and the like, bending them along the bending parts to temporarily assemble them, and joining the joining parts, a box body having a predetermined three-dimensional shape is obtained. Recycling costs are low because only small scraps, such as the gate, need to be recycled. The color of the finished product can be changed freely as long as there is a colorless resin raw material and a pigment of the required color. If the molding die has a nesting structure in which the pattern or characters are formed, the design can be easily changed by replacing the nesting. If the assembly-type box body to be molded is a video cassette storage box and the wall thickness of the bent portion is smaller than 0.15 mm, cracks may occur during bending. If the wall thickness of the bent portion is larger than 0.30 mm, it may be difficult to bend. Further, by setting the injection pressure and the injection rate in the above ranges, respectively, a thin sheet-shaped semi-finished product can be stably formed with a high yield.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a development plane of a prefabricated box for carrying out the method of the present invention. Video cassette storage box (assembled box) 1
0 is the main body portion 12, and the joining piece portions 14 and 16 integrated with the main body portion 12.
It consists of The body portion 12 is formed with a plurality of bent portions 10a, 10b, 10c, and 10d, respectively. As will be described later, the main body 12 has
The connection portion with the pin point gate, which serves as the molten resin introduction port of the molding die, is cut to leave a cut mark 12e. The molding die used for injection molding has a cavity shape corresponding to the main body portion 12, the joining piece portions 14 and 16, and has a pin at a position corresponding to the central portion of the main body portion 12 (in the embodiment, the back portion of the box). It is said that a point gate is formed. The installation position of the pinpoint gate is selected so that the cutting trace 12e faces the inside of the box when the box is assembled. As an embodiment of the video cassette storage box 10, the thickness of the main body 12 is 0.4 mm to
0.6 mm, the bent portions 10a, 10b, 10c,
And 10d have wall thicknesses t (see FIG. 2) of 0.
It is desirable to set it to 15 mm to 0.3 mm. That is, the wall thickness dimension of the bent portion may be set to be thinner than the wall thickness dimension of the flat surface portion by 0.25 mm to 0.30 mm. As a result, the molten resin injected into the mold cavity through the pin point gate is
2. The joining piece portions 14 and 16 are integrally formed, and the portions corresponding to the bent portions 10a, 10b, 10c, and 10d are formed in a thin wall shape that is easier to bend than other portions. .

Next, the operation of this embodiment will be described. Injection molding is performed using the above-described molding die. That is, the molten resin is injected from the injection nozzle (not shown) of the injection device into the mold cavity through the pin point gate of the mold. In order to injection-mold a thin-walled shape such as the video cassette storage box 10 with respect to the surface area, the material used is polypropylene with MI (melt index) 20 to 70, and the injection pressure is
900 kg / cm ² or more (2000 kg / cm ² or less)
And the injection rate is 500 cm ³ / sec or more (1300 c
m ³ / sec or less) is desirable. With this setting, as will be described later, a thin sheet-shaped semi-finished product can be stably molded with high yield.
Immediately before the molten resin is completely filled in the mold cavity, it is desirable to reduce the injection pressure below the value at the start of injection or the injection rate below the value at the start of injection (both start injection). It may be lower than the hour value). This makes it possible to prevent burrs and warpage of the molded product. An injection molding method or an injection compression molding method is used as the molding method. In this way, the development plane shape video cassette storage box (semi-finished product) 10 as shown in FIG. 1 is molded. The mold is opened after a pressure-holding / cooling process and the like, and the development plane-shaped video cassette storage box 10 is taken out from the molding die. The gate portion is separated from the main body portion 12 (cutting trace 12e is formed). In a separate step, the semi-finished product is folded and temporarily assembled, and the adhesive is applied to the predetermined surface sides of the joining piece portions 14 and 16 and the predetermined surface side of the overlapping surface of the main body portion 12, respectively. Then, the joining portions are adhered to each other to assemble a three-dimensional video cassette storage box (finished product) 10a as shown in FIG. The gate section separated from the main body section 12 is put into a hopper for a raw material supply section through a predetermined crushing process, and is supplied to a kneading / melting section of an injection device together with raw material pellets for recycling.

(Test Example) Thickness of the flat portion of the finished product is 0.
4mm, using a mold for a video cassette storage box with a mold cavity formed so that the thickness of the bent part is 0.15mm (there are engraved patterns, letters, grain, etc.) The material used is polypropylene with MI = 40, and the injection pressure at the start of injection is 900 kg / cm.
^{2. The} injection rate is set to 500 cm ³ / sec, and the injection pressure and the injection rate are made lower than the above values immediately before the mold cavity is completely filled with the molten resin, and the development plane shape video cassette storage box 10 is provided. Was injection molded. The developed flat video cassette storage box 10 (semi-finished product), which was opened from the mold and opened from the mold, had no defects such as warpage and had a good surface. After cutting the gate part from this semi-finished product, it was bent along the bent part for temporary assembly, and an adhesive was applied to the bonding surface and bonded to complete the video cassette storage box 10a. The completed video cassette storage box 10a has a good appearance in which pictures, characters, grain, etc. are transferred, does not deform over time, and is the same as that manufactured from a resin sheet material. It was

The forming die corresponding to the main body portion 12 can be partially of a nested structure if necessary. By doing so, it is possible to easily change the pattern, characters, grain, etc. formed on the surface of the product by appropriately replacing the nesting portions. Further, in the above description of the embodiment, the video cassette storage box 10 is injection-molded as the assembly-type box body, but any assembly-type box body may be used.
For example, the present invention can be applied to manufacture of a hard case of a book.

[0010]

As described above, according to the present invention,
It is possible to manufacture a prefabricated box at a lower cost than before. It is possible to easily change the pattern, characters, grain, etc. formed on the surface of the assembled box. Unlike the prior art, it is not necessary to stock sheet materials of various colors in order to correspond to the designated color, and it is possible to manufacture a preassembled box body of various colors by a simple color changing operation.

[Brief description of drawings]

FIG. 1 is a diagram showing a video cassette storage box (assembled box body) developed on a plane.

FIG. 2 is a partial cross-sectional view including a bent portion.

FIG. 3 is a diagram showing a completed product of a video cassette storage box.

[Explanation of symbols]

 10 Video cassette storage box (semi-finished product of prefabricated box) 10a Video cassette storage box (finished product of prefabricated box) 12 Main body 12a, 12b, 12c, 12d Bent 12e Pin point gate cutting trace 14 Joining piece Part 16 Joining piece

Claims (3)

[Claims] 1. Molding having a mold cavity formed in a shape corresponding to a developed plane shape of an assembling type box body, and a portion corresponding to a bent portion of the assembling type box body is formed thinner than other portions. Perform injection molding or injection compression molding using a mold, then take out the semi-finished product of the developed flat shape from the molding die and fold it along the folds to temporarily assemble the semi-finished product, and then join the joint surfaces of the semi-finished products A method of manufacturing a prefabricated box body, which is characterized in that a finished product is obtained by joining the above. 2. The assembly type box body to be molded is a video cassette storage box, the resin material used is polypropylene of MI20 to MI70, and the gate of the molding die is a pinpoint opening toward the center of the die cavity. It is a gate, and the wall thickness of the bent part of the assembly type box is 0.15 mm ~
It is 0.30 mm, The manufacturing method of the assembly-type box body of Claim 1 characterized by the above-mentioned. 3. The injection pressure is 900 kg / cm ² or more 20
Less than 00 kg / cm ² and injection rate is 500c
method for producing a prefabricated box body according to claim 2, wherein the m ³ / sec or more 1300cm is ³ / sec or less.