JPS6285924A - Mold for blow molding for plastic container - Google Patents

Abstract

PURPOSE:To prevent the occurrence of breakage and accumulation of a material near a hinge, by dissolving a poor molding due to the shortage of an expanding pressure resulting from the breakage of a parison near the compressing area of a mold. CONSTITUTION:A projection cavity surface 15A forming inner walls 2A, 3A of a main body 2 and a cover 3 and a compressing part 16A forming a hinge 4 are formed in a half mold 13. A recess cavity surface 15B forming outer walls 2B, 3B of a main body 2 and a cover 3 and a compressing part 16B forming a hinge 4 are formed in the other half mold 14. A jointing surface of a container 6 and the hinge 4 are formed on a parting line 9 of a mold 12. A parting 9' connecting the hinge 4 and the jointing surface of the container 6 is inclinedly formed to widen toward the outer direction of the jointing surface of the mold. The compressing part 16A forming the hinge 4 of the half mold 13 projects in a trapezoidal shape having an edge in a tapering-off shape and the compressing part 16B forming the hinge 4 is recessedly set having an edge spreading out in a fan-shape. Excellent hinge strength can be obtained and the occurrence of breakage and accumulation of a material can be prevented by this constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] 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, a plastic container 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 is disclosed in Japanese Patent Publication No. 49-18748. It is publicly known as shown in the official gazette.

[Problem to be solved by the invention]

However, conventional blow-molded plastic containers have the following drawbacks. In other words, since the hinge base formed on the parting line during blow molding is configured on the same line as the mating surface of the container, excessive stress is applied to the hinge when the container is used, and the hinge base on the main body side Since the hinge width up to the hinge base on the lid body side is formed 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 above-mentioned factors, conventional containers are inferior in the 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 distant from the mating surface of the container and by forming the hinge width to be large. but,
The manufacturing method for such plastic containers is as follows (11,
This resulted in new problems such as (2) and (3).

(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. At that time, among the cavity surfaces for molding the vicinity of the hinge of the plastic container, - the compression part 2 for hinge molding of the man's hand mold 23;
There is a risk that the parison 21 may be torn at the end 30 of the mold 6A, or at the hinge side end 40 of the container mating and solid-formed part 27A of the other half mold 24, or that the parison 21 may be torn due to shearing force at the opposing ends 30 and 40. This caused molding defects.

(2) As the material sheared and compressed by the opposing ends 30 and 40 moves just before the mold is closed, creases may occur near the container mating surface of the molded plastic container or at the hinge. This may cause poor appearance.

(3) When removing the edges formed on both ends of the hinge of a molded plastic container, when moving a blade such as a cutter along the parting line, the resistance between the edge at the hinge end and the edge on the container mating surface is extreme. Because of this, the cuffer could not be moved smoothly, and there was a risk of notches, etc., making it difficult to perform deburr removal work stably.

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

[Means for solving problems]

The present invention extrudes a plasticized parison of plastic and closes a set of molds with a convex cavity surface of one mold half protruding into a 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 side 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 on one half of the mold, and a recessed compression part having a widening end on the other half. to form a hinge,
After removing the molded product from the mold, the molded container is closed and the edge of the hinge formed at the end of the compression part is removed along the inclined parting line. The present invention relates to a method for manufacturing a plastic container.

[Effect]

In the present invention, when the mold is closed, a protruding compression part with a tapered beveled end of one mold half and a recessed compression part with a flared beveled end of the other mold half are used. Since the approximately middle part of the parison is evenly clamped and compressed between the parts, there is no risk of the parison contacting the inner surface of the mold very locally and being torn. Since the movement timing of the clamped parison is almost the same as the movement timing of the parison clamped at the compression part other than the end, abnormal material movement of the parison may occur near the molded hinge or container mating surface. Excellent formability with no creases.

Further, when removing the ribs formed at both ends of the hinge of a molded plastic container, the ribs 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 lid side of the container to the container mating surface changes rapidly. Since the resistance applied to the cutter blade and the like during deburr removal does not change drastically, the deburr removal work can be carried out smoothly. [Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show a plastic container 1 manufactured by blow molding according to the present invention.
is made of a single plastic material, for example, a thermoplastic such as polyethylene, polypropylene, vinyl chloride, ethylene-vinyl acetate copolymer, holamide, etc., and includes a main body 2, a lid 3, and the main body 2 and lid 3. It is composed of hinges 4 that are compressed and thinned to be integrally connected. The hinge 4 is compressed with a compression of 2 to 40 times, preferably 5 to 30 times, and has a compression ratio of 0.211III to 1.0 Im11.
Preferably, the thickness is 0.3 to 0.8 mm. Note that compression is the ratio of the wall thickness of the parison before compression to the wall thickness after compression. The main body 2 and the lid 3 each have a double wall structure with inner walls 2A, 3A and outer walls 2B, 3B, 5 is a storage section, 6 is a mating surface of the container, and 7 is a separate item attached. It is a locking tool. The hinge base 8 of the hinge 4 is formed on the parting line during blow molding, and extends approximately 1 mm to 15 ff1 outward from the mating surface 6 of the container.
m is preferably formed at a position 81 away from 2mn+. 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 manufacturing 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 such as polyethylene, and 12 is a This is a split mold consisting of a half mold 13 and a half mold 14.

One half mold 13 is formed with a convex cavity surface 15A forming the inner walls 2A and 3A of the main body 2 and the lid 3, and a compressed portion 16A forming the hinge 4. The other half mold 14 has a main body 2. A concave cavity surface 15B forming the outer walls 2B and 3B of the lid 3 and a compressed portion 16B forming the hinge 4 are 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 formed on the parting line 9 of the mold 12, and the parting line 9' connecting the hinge 4 and the mating surface 6 of the container is approximately 10 degrees. Formed at an angle of 70 degrees from the half mold 13
The compressed portion 16A forming the hinge 4 of the half mold 14 protrudes in a trapezoidal shape with a tapered end, and the compressed portion 16B forming the hinge 4 of the half mold 14 is tapered to widen toward the end. It is recessed so as to have a

Next, to explain the manufacturing method of the plastic container l according to the present invention, first, a thermoplastic such as polyethylene is melt-kneaded by an extruder (not shown), and a plasticized cylindrical parison 11 is produced by an extrusion head 10. Extruded as The parison 11 is an open mold 12 or half mold 13.
14 and then protruding into the convex cavity surface 15B of one half mold 13, the pair of molds 12 is closed, and the parison 11 is clamped. At this time, the parts connecting the hinge 4 and the mating surface 6 of the container, that is, the parting lines 9' located at both ends of the compression parts 16A and 16B, are formed at an angle, so that when the mold 12 is closed, the parison 11
There is no fear that it will break.

That is, when closing the mold, a protruding compression section 16A having a tapered end on one mold half 13 and a recessed compression section 16A having a tapered end on the other mold half 14 are formed. Since substantially the middle of the parison 11 is evenly pinched and compressed by the portion 16B, there is no risk that the parison 11 will come into contact with the inner surface of the mold locally and break. In addition, by evenly compressing the compressed parts 16A and 16B, the movement timing of the parison 11 (at the parting line 9') clamped at the inclined ends of the compressed parts 16A and 16B and the compressed parts 16A other than the end parts can be adjusted.
, 16B are moved to the parison 11 (at the parting line 9) at almost the same time, so there are folds near the molded hinge 4 and the container mating surface 6 due to abnormal material movement of the parison. Excellent moldability with no occurrence of

Next, pressurized fluid such as compressed air is blown into the parison 11 from the blowing nozzle 17 to form the main body 2 and the lid 3 through the convex cavity 15A and the concave cavity 15B, and the parison 11 is formed using the compression parts 16A and 16B. By compressing the intermediate portion, a compressed and thinned hinge 4 is formed.

Next, after cooling the molded article formed from the parison 11, the mold 12 is opened, the molded article is taken out, and the excess paris is removed, thereby producing a container 1 as shown in FIGS. 1 and 2. Manufactured.

In addition, when removing the edges formed on both ends of the hinge 4 of a molded plastic container, it is necessary to remove the sloped ends of the hinge 4 with the molded container 1 closed, as shown in FIG. Remove the Paris F along the cutting lines 9.9', 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 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. and 9' and 9 does not change suddenly, the resistance applied to the cutter blade etc. during deburring does not change drastically, so deburring can be carried out smoothly. .

Incidentally, FIG. 5 shows the other side 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. container 1
In order to form both ends 4' of the hinge 4 to be curved inward as shown in FIG. 5, a blade such as a cutter is cut along the inclined parting line 9' with the container closed. It can be easily formed by moving obliquely to the outer surface of the container and removing the edges, and since the hinge base 8 is formed longer than the center, the bending strength of the hinge 4 can be greatly increased.

The present invention provides, as described above, - a plastic container manufactured by blow molding comprising a main body made of a single plastic material, a lid, and a compressed thin hinge connecting the main body and the lid together; The base of the hinge, which is formed on the parting line during blow 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, it has excellent protection for stored items. You can get a container. Furthermore, since the parting line connecting the hinge base and the mating surface is formed at an angle, the blow moldability is excellent, and the removal of pars is reliable and easy, so that a container with excellent appearance characteristics can be obtained.

We also extrude the plasticized parison of plastic,
A pair of molds, in which the convex cavity surface of one mold half protrudes into the concave cavity surface of the other mold half, is closed so as to sandwich the parison, and the compression part formed in the mold is used to compress the parison. In a method for manufacturing a plastic container in which a hinge is formed by compressing the approximate middle part and a parison in a mold is expanded, when the mold is closed, approximately the middle of the parison is compressed in a compressed part with inclined parting lines at both ends. Since clamping and compression is performed, problems such as insufficient expansion pressure caused by the parison being torn near the compressed portion can be solved, and problems such as uneven thickness and folded thickness can also be solved, making it possible to obtain a plastic container with excellent appearance characteristics. Furthermore, since the hinge of the container is formed at the compressed part where the parting lines at both ends are inclined, when removing pars with the container closed after forming, it is extremely easy to remove along the inclined parting lines. be able to.

The plastic container of the present invention may have a main body and a lid having a hollow double wall structure, or may have a double wall structure in which an inner wall and an outer wall are joined. Further, 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 being torn near the compression part in the mold are solved, and the blow moldability is excellent, and the removal of paris is also reliable and easy. has.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway side view of a plastic container according to the present invention, FIG. 2 is a back view of the same as above, FIG. 3 is a sectional view of a mold showing one manufacturing process of the plastic container according to the present invention, and FIG. 4 3 is a cross-sectional view taken along the line A-A in FIG. 3, FIG. 5 is a top view of the main parts of the blow-molded plastic container according to the present invention showing the other side with the lid open, and FIG. 6 is a diagram showing the deburring process of the present invention. FIG. 7 is a perspective view of the main parts near the hinge to be explained, and FIG. 7 is a cross-sectional view of the return mold with compression part just before the mold is closed to explain the conventional manufacturing method. 1... Plastic container 2... Main body 3... Lid 4... Hinge 6... Container mating surface 9... Parting line

Claims (1)

[Claims] A plasticized parison of plastic is 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, the method includes compressing approximately the middle of the parison in a compression part formed in the mold to form a hinge, and expanding the parison in the mold,
When closing the mold, a protruding compression section with a tapered beveled end on one mold half and a recessed compression section with a flared end on the other mold half close the parison. A hinge is formed by evenly compressing approximately the middle, and after removing the molded product from the mold, the end of the molded hinge is tilted at the end of the compressed part with the molded container closed. A mold for blow molding plastic containers, which is characterized by removing burrs along the parting line.