JPS6152782B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a plastic container, which is manufactured by blow molding and includes a main body, a lid, and a hinge that connects them together.

[Conventional technology]

Conventionally, plastic containers manufactured by blow molding consisting of a main body made of a single plastic material, a lid, and a compression-thinned hinge that integrally connects the main body and the lid have been disclosed in Japanese Patent Publication No. 49-1983.
This is known as shown in Japanese Patent No. 18748.

[Problem to be solved by the invention]

However, conventional blow-molded plastic containers have the following drawbacks. That is,
The hinge base, which is formed on the parting line during blow molding, is aligned with the mating surface of the container, so excessive stress is applied to the hinge when the container is used. Since the width of the hinge up to the base of the hinge is small, the hinge strength is poor, and this drawback is particularly noticeable in containers made of polyolefin plastic materials such as polyethylene. Due to the factors described above, conventional containers have poor repeated bending characteristics of the hinge, and the life of the container itself has to be shortened. The applicant came up with the idea of forming a hinge with a large width as a means to solve the above-mentioned drawbacks, but even if the hinge was formed in this way, a gap would be created between the mating surfaces of the container, resulting in a container with poor protection properties for stored items. Ta. Therefore, an attempt was made to solve the above-mentioned drawbacks by forming the hinge base formed on the parting line during blow molding at a position farther from the mating surface of the container and by forming the hinge width larger. However, this method of manufacturing plastic containers has caused new problems such as (1), (2), and (3) below.

(1) As shown in Fig. 7, as the mold consisting of one half mold 23 and the other half mold 24 is closed, the parison 21 inside the mold deforms along the mold cavity surface. To go. At this time, among the cavity surfaces that mold the vicinity of the hinge of the plastic container, the compressed part 26A for hinge molding of one half mold 23 is
or the hinge side end 40 of the container mating surface molding part 27A of the other half mold 24, or the opposite end 3
0.40, there was a risk that the parison 21 would be torn due to shearing force, causing molding defects.

(2) As the material that has been sheared and compressed by the opposing ends 30 and 40 moves just before the mold is closed, it may break near the container mating surface of the molded plastic container or at the hinge. This may cause the appearance of meat to deteriorate.

(3) When removing burrs formed on both ends of the hinge of a molded plastic container, moving a cutter or other blade along the parting line will cause
Since the resistance between the burr at the end of the hinge and the burr at the container mating surface changes drastically, the cutter cannot be moved smoothly and there is a risk of notches, making it difficult to perform the burr removal work stably.

The present invention provides a method for manufacturing a plastic container that has excellent blow moldability and allows reliable and easy removal of burrs.

[Means for solving problems]

The present invention extrudes a plasticized parison of plastic and closes a set of molds in which the convex cavity surface of one mold half projects into the concave cavity surface of the other mold half so as to sandwich the parison; In a method for manufacturing a plastic container, in which a compression section formed in a mold compresses approximately the middle of a parison to form a hinge, and the parison in the mold is expanded, one half is compressed when the mold is closed. Approximately the middle of the parison is evenly sandwiched and compressed by a protruding compression part having a tapered end of the mold and a recessed compression part having a divergent end of the other mold half. After forming the hinge and removing the molded product from the mold, with the molded container closed, burr the end of the hinge formed at the end of the compression part along the inclined parting line. The present invention relates to a method of manufacturing a plastic container, which is characterized by removing the plastic container.

[Function] In the present invention, when the mold is closed, one half of the mold has a protruding compression part having a tapered end and the other half has a flared end. Since the recessed compression part evenly pinches and compresses the parison approximately in the middle, there is no risk of the parison contacting the inner surface of the mold in a very local area and breaking it.
By evenly clamping and compressing, the movement timing of the parison clamped at the inclined end of the compression part and the movement timing of the parison clamped at the compression part other than the end part are almost the same, so that the molding is not possible. There is no bending caused by abnormal material movement of the parison near the hinge or container mating surface, resulting in excellent formability. Furthermore, when removing burrs formed on both ends of the hinge of a molded plastic container, the burrs are removed along the inclined parting line at the end of the hinge while the molded container is closed. At this time, the distance between the parting line formed from the hinge base on the container body side to the container mating surface and the parting line formed from the hinge base on the container lid side to the container mating surface changes rapidly. Since there are no burrs, the resistance applied to the cutter blade etc. during burr removal does not change drastically, so burr removal work can be carried out smoothly.

〔Example〕

An embodiment of the present invention will be described below based on the drawings. 1 and 2 show a plastic container 1 manufactured by blow molding according to the invention, which container 1 is made of a single plastic material, such as polyethylene, polypropylene, vinyl chloride, ethylene-vinyl acetate. It is made of a thermoplastic such as a copolymer or holamide, and includes a main body 2, a lid 3, and a compressed thin hinge 4 that connects the main body 2 and the lid 3 together. The hinge 4 is compressed with a compression of 2 to 40 times, preferably 5 to 30 times, and 0.2 mm to 1.0 mm, preferably 0.3
It is formed with a wall thickness of ~0.8mm. Note that compression is the ratio of the inner thickness of the parison before compression to the inner thickness after compression. The main body 2 and the lid 3 have a double-walled structure with inner walls 2A, 3A and outer walls 2B, 3B, respectively, 5 is a storage section, 6 is a mating surface of the container, and 7
is a locking tool made by attaching a separate item. Hinge 4
The hinge bases 8 are formed on the parting line during blow molding, and are spaced outward from the mating surfaces 6 of the container by approximately 1 mm to 15 mm, preferably 2 mm to 8 mm. Note that the mating surface 6 of the container and the hinge base 8 are molded so as to be arranged substantially parallel to each other. A parting line 9 connecting the hinge base 8 and the mating surface 6 is inclined at an angle of about 10 degrees to 70 degrees.

3 and 4 show an apparatus for producing a blow-molded plastic container 1 according to the present invention, in which 10 is an extrusion head, 11 is a cylindrical parison made of plasticized thermoplastic plastic such as polyethylene,
Reference numeral 12 denotes a split mold consisting of a half mold 13 and a half mold 14. One half mold 13 has a convex cavity surface 15 that forms the inner walls 2A and 3A of the main body 2 and the lid 3.
A compressed portion 16A forming the hinge 4 is formed. The other half mold 14 has a concave cavity surface 15 forming the outer walls 2B and 3B of the main body 2 and the lid 3.
A compressed portion 16B forming the hinge 4 and the hinge 4 is formed. Note that 17 is a blowing nozzle. As shown in FIG. 4, the mating surface 6 of the container and the hinge 4 are
The parting line 9', which is formed on the parting line 9 of 2 and connects the hinge 4 and the mating surface 6 of the container, is inclined at an angle of about 10 degrees to 70 degrees, and is formed on the parting line 9 of the half mold 13. The compression part 16A forming the hinge 4 of the half mold 14 projects in a trapezoidal shape with a tapered end, and the compression part 16B forming the hinge 4 of the half mold 14 has a tapered end. It is recessed.

Next, to explain the manufacturing method of the plastic container 1 according to the present invention, first, thermoplastic plastic such as polyethylene is melt-kneaded in an extruder (not shown), and a plasticized cylindrical parison 11 is produced from the extrusion head 10. Extruded as parison 11
is placed between the opened mold 12, that is, the half molds 13 and 14, and then closes the pair of molds 12 protruding into the convex cavity surface 15B of one half mold 13, and the parison 11 is held between them. . At this time, the portion connecting the hinge 4 and the mating surface 6 of the container, that is, the compression portion 16A, 1
Since the parting lines 9' located at both ends of the mold 6B are formed to be inclined, there is no fear that the parison 11 will be torn due to the mold 12 being closed.

That is, when closing the mold, one half mold 13
Approximately the middle of the parison 11 is evenly sandwiched and compressed by a protruding compression part 16A having a tapered end and a recessed compression part 16B having a widening end of the other half mold 14. Therefore, there is no risk that the parison 11 will partially contact the inner surface of the mold and break. Furthermore, by evenly pinching and compressing, the movement timing of the parison 11 (at the parting line 9') held at the inclined ends of the compression parts 16A and 16B and the compression parts 1 other than the ends are also determined.
6A and 16B are moved to the parison 11 (at the parting line 9) at almost the same time, so the formed hinge 4 and the vicinity of the container mating surface 6 are bent due to abnormal material movement of the parison. Excellent moldability with no buildup.

Next, pressurized fluid such as compressed air is blown into the parison 11 from the blowing nozzle 17 to form the convex cavity 15.
A and the concave cavity surface 15B form the main body 2 and the lid 3, and the compressed parts 16A and 16B.
By compressing approximately the middle of the parison 11, a thinned hinge 4 is formed. Next, after cooling the molded product formed from the parison 11, the mold 12 is opened, the molded product is removed, and excess burrs are removed, thereby producing a container 1 as shown in FIGS. 1 and 2. . In addition, when removing the burrs formed on both ends of the hinge 4 of the molded plastic container 1, it is necessary to remove the slanted part of the end of the hinge 4 with the molded container 1 closed, as shown in FIG. The burr F is removed along the cutting lines 9, 9', and 9. At this time, parting lines 9, 9', 9 are formed from the hinge base 8 on the main body 2 side of the container 1 to the container mating surface 6, and parting lines 9, 9', 9 are formed from the hinge base 8 on the lid 3 side of the container 1 to the container mating surface 6. Since the distance between the parting lines 9, 9', and 9 that have been formed does not change suddenly, the resistance applied to the cutter blade etc. during burr removal does not change drastically, so burr removal work can be carried out smoothly. .

FIG. 5 shows another example of the plastic container according to the present invention, in which both ends 4' of the hinge 4 are curved inward. The hinge base 8 formed on the parting line during blow molding is formed at a position away from the mating surface 6 of the container, and the parting line 9' connecting the hinge base 8 and the mating surface 6 is formed at an angle. In order to curve both ends 4' of the hinge 4 inwardly as shown in FIG. It can be easily formed by moving the blade obliquely to the outer surface of the container and removing burrs, and since the hinge base 8 is formed longer than the center, the bending strength of the hinge 4 can be greatly increased.

As described above, the present invention is a plastic container manufactured by blow molding, which includes a main body made of a single plastic material, a lid, and a compression thinned hinge that integrally connects the main body and the lid. The base of the hinge, which is formed on the parting line during molding, is formed at a position farther from the mating surfaces of the container, so the hinge has excellent strength, and since there is no gap between the mating surfaces of the container, the container has excellent protection for stored items. can be obtained. Furthermore, since the parting line connecting the hinge base and the mating surface is formed at an angle, blow moldability is excellent, and burrs can be removed reliably and easily, so that a container with excellent appearance characteristics can be obtained.

The plasticized parison of the plastic is also extruded and a set of molds is closed, with the convex cavity surface of one mold half protruding into the concave cavity surface of the other mold half, so as to sandwich the parison. In a method for manufacturing a plastic container, in which a compression part formed in a mold compresses approximately the middle of the parison to form a hinge, and the parison in the mold is expanded, the approximately middle of the parison is compressed when the mold is closed. Since the parting lines at both ends are clamped and compressed at the inclined compression parts, problems such as lack of expansion pressure caused by the parison tearing near the compression parts can be solved, and problems such as uneven thickness and folded thickness can also be solved, resulting in improved appearance. A plastic container with excellent properties can be obtained. Furthermore, since the hinge of the container is formed at the compression part where the parting lines at both ends are inclined, when removing burrs with the container closed after forming, it is extremely easy to remove burrs along the inclined parting lines. be able to.

The plastic container of the present invention may have a hollow double-wall structure in which the main body and the lid have a hollow double-wall structure, or may have a double-wall structure in which an inner wall and an outer wall are joined. Furthermore, the plastic container of the present invention can be used as a container for storing calculators, typewriters, measuring instruments, cameras, radios, binoculars, tanks, bottles, tools, etc., or various housing members, and its uses are not limited in any way.

〔Effect of the invention〕

According to the present invention, problems such as poor molding due to lack of expansion pressure caused by the parison breaking near the compressed part in the mold are solved, and the blow moldability is excellent, and burrs can be removed reliably and easily. has.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view of a plastic container according to the present invention, FIG. 2 is a rear view of the same, FIG. 3 is a sectional view of a mold showing one manufacturing process of the plastic container according to the present invention, and FIG. is a sectional view taken along line A-A in Figure 3,
FIG. 5 is a top view of main parts in an open state showing another example of the blow-molded plastic container according to the present invention; FIG. 6 is a perspective view of main parts near the hinge to explain the burr removal process of the present invention; FIG. The figure is a cross-sectional view of a mold near the compressed part immediately before the mold is closed, illustrating a conventional manufacturing method. 1...Plastic container, 2...Main body, 3...
Lid body, 4... Hinge, 6... Container mating surface, 9
...parting line.

Claims (1)

[Claims] 1 Extrude a plasticized parison of plastic, close a pair of molds with a convex cavity surface of one mold half protruding into a concave cavity surface of the other mold half, and clamp the parison; In a method for manufacturing a plastic container, in which a compression section formed in the mold compresses approximately the middle of the parison to form a hinge, and the parison in the mold is expanded, when the mold is closed, one half of the mold is compressed. The hinge is formed by evenly sandwiching and compressing approximately the middle of the parison between a protruding compression part having a tapered end of the mold and a recessed compression part having a divergent end of the other half. After forming and removing the molded product from the mold, remove burrs from the end of the hinge molded at the end of the compression part along the inclined parting line with the molded container closed. A method for manufacturing a plastic container characterized by the following.