JPH0688351B2 - Method for manufacturing plastic container having outer sleeve - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a method for manufacturing a plastic container in which an outer sleeve mainly having a trade name, a decorative pattern or the like printed thereon is fitted on the outer peripheral surface. .

[Prior Art] A conventional method for manufacturing a plastic container having an outer sleeve is disclosed in, for example, Japanese Patent Laid-Open No. 47-11037 and Japanese Utility Model Laid-Open No. 61-93415.
As in the method disclosed in Japanese Patent Publication No. JP-A-53-116987, a means for forming a reheat adhesive layer on the inner surface of the outer sleeve and integrally adhering to the container main body at the time of molding the container, as shown in JP-A-53-116987 A means for supporting the container body by the upper and lower ends of the outer sleeve, or JP-B-59-16316 and JP-B-64.
As disclosed in Japanese Patent Laid-Open No. 3745, a means is provided in which a protruding portion that projects outward is provided on the outer peripheral surface of the container body, and the outer sleeve is supported so as not to fall off.

The above-mentioned means for forming the reheating adhesive layer on the outer sleeve or the means for supporting the container body at the upper and lower ends of the outer sleeve increase the cost of the outer sleeve and complicate the mold structure. The means for providing the protrusion on the outer peripheral surface of the main body also has a problem that the mold structure is complicated and the cost is increased, and the common problem is that the production speed cannot be increased.

[Problems to be Solved by the Invention] In view of the current state of the conventional manufacturing method described above, the present invention can use an exterior sleeve having a simple structure without a reheat adhesive coating on the inner surface, and the same. Using a relatively simple upper mold that has a cylindrical wall surface and a lower mold that allows the bottom shape to be designed freely, the outer sleeve inserted into the mold falls off and is displaced at a speed more than double that of conventional manufacturing methods. It is an object of the present invention to provide a method capable of inexpensively manufacturing a high-quality plastic container having an outer sleeve without causing the above problems.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the present invention, with respect to the lower end of an upper mold having a barrel cavity having a cylindrical surface of the same wall, with a draft in the opening direction, The upper end of a lower mold having a stepped portion which is continuous with the body cavity and has a gradually reduced diameter and a bottom cavity continuing from the stepped portion is brought into contact with each other, and at least a minute gap between the parting surfaces of both molds is vacuumed. Leave it as a mouth,
The outer sleeve is lubricated, and the lower end of the outer sleeve has a piece that is folded upward toward the inside. The outer sleeve is inserted into the upper mold and brought into close contact with the body cavity. The lower end of the outer sleeve is folded back at the step of the lower mold. The outer sleeve is supported by the vacuum suction port so that the piece protrudes inward, and the outer sleeve is held in the mold by the suction action.The inner sleeve is formed of only plastic and is continuous with the bottom of the container. The configuration is such that molding is performed to form the plastic body portion, and the configuration in which only the sleeve body side that overlaps the folded piece at the lower end of the exterior sleeve is supported by the lower mold step portion is adopted.

[Operation] Since the present invention employs the above-described configuration, the exterior sleeves having the folded piece formed at the lower end are inserted into the upper and lower molds that are in contact with each other, and are brought into close contact with the body cavity, Moreover, when the lower end of the lower die is supported by the lower die and a negative pressure is applied to the vacuum suction port on the parting surface, the outer sleeve is securely held in the upper die, and after the molding, even if it is integrated into the upper and lower parts for molding. Even if the supposed type is reversed,
It is possible to proceed to the molding process without causing displacement in the mold, dropping out of the mold, and the like, and it is possible to simplify, speed up, and ensure the work of inserting the outer sleeve into the upper and lower molds.

After that, when a plastic container is molded by an ordinary method, the plastic layer is molded from the bottom cavity of the lower mold through the step portion to the inner surface of the folded piece of the outer sleeve and closely to the inner surface of the sleeve main body. , The step of the lower die is in close contact with the inner side of the lower end of the outer sleeve supported by the lower step, and the folded piece of the outer sleeve is the main body of the plastic container from the three directions of the upper edge, the lower edge and the inner peripheral surface. The structure is such that the parts are held and pinched.

The outer peripheral surface of this exterior sleeve is coated with a lubricant such as silicone resin by printing or coating,
Since the slip between the upper mold and the upper mold is good, the mold release after molding is performed quickly even if the draft is small.

As described above, in the method of the present invention, since the folded-up piece at the lower end of the outer sleeve is held by the molded container main body, the outer sleeve with respect to the container main body can be held only by this holding structure. Since it is possible to prevent the positional deviation of the upper and lower parts from being loosened in the vertical direction, it is not necessary to form recesses in the upper mold and the lower mold for molding the protrusions for supporting the outer sleeve. The body cavity can have a smooth single cylindrical surface, which can simplify the mold structure.

Further, since the bottom cavity can be formed in the lower mold which is separate from the upper mold, the freedom of designing the bottom cavity of the lower mold becomes large.

As a result, the upper mold and the lower mold can be simply and separately provided, the die cost can be reduced, the production speed can be improved, and the container cost can be reduced.

INDUSTRIAL APPLICABILITY The manufacturing method according to the present invention can be applied not only to vacuum forming and pressure forming, but also to injection molding, in which case the folded piece of the outer sleeve which is supported by the step portion of the lower die and protrudes inward. Since the core portion located at the lower portion has an undercut shape corresponding to the thickness of the folded piece, the product can be taken out together with the core from the so-called cavity formed by the upper die and the lower die.

[Example] In the illustrated example, an upper mold 1 and a lower mold 2 shown in FIGS. 1 and 2 are used, and a plastic container 4 having an outer sleeve 3 as shown in FIGS. 3 to 5 is used. In this example, the thermoplastic synthetic resin sheet is manufactured by vacuum forming, which is a type of thermoforming.

The above-mentioned upper mold 1 is provided with a barrel cavity 5 which is a cylindrical surface of a single generatrix and has a draft of an angle θ toward the opening direction.

On the other hand, the lower die 2 that abuts the lower end 6 of the upper die 1 has a step portion 7 that is continuous with the body cavity 5 and has a gradually reduced diameter, and a bottom cavity 8 that follows this step portion 7. A minute gap is formed on the parting surface between the upper end 9 of the lower mold 2 and the lower end 6 of the upper mold 1 to form a vacuum suction port 10.

The width W of the stepped portion 7 is the folding piece 12 of the outer sleeve 3.
It is set to be equal to the thickness D of the sleeve main body 13 that overlaps with the sleeve main body 13, and the peripheral wall surface 14 of the bottom cavity 8 is
Is a surface that shares the same generatrix with the inner peripheral surface 15 of the outer sleeve 3 that is in close contact with.

The peripheral wall surface 14 of the bottom cavity 8 is formed by the outer sleeve 3
The width W of the stepped portion 7 becomes larger than the thickness D of the sleeve main body 13 in that case, the width W of the stepped portion 7 may be closer to the center axis direction of the container than the generatrix forming the inner peripheral surface 15.

Further, a lubricant such as silicone resin is applied to the outer surface of the sleeve main body 13 of the outer sleeve 3 by printing, coating or the like, but no reheat adhesive coating or the like is provided on the inner back surface.

FIG. 3 shows an example of the exterior sleeve 3 described above with a part cut away.

In the present invention, the upper mold 1 and the lower mold 2 having the above-described structure are assembled by forming a vacuum suction port 10 on the parting surface as shown in FIGS. 3 is closely fitted to the body cavity 5 and fitted into the upper mold 1, and the lower end 11 of the sleeve 3 is supported by the step 7 of the lower mold 2.
Arrange so that the folded-back piece 12 side protrudes inward.

Next, when a normal vacuum forming process is performed and a negative suction pressure is applied to the vacuum suction port 10, a negative pressure acts on the stepped portion 7 through the vacuum suction port 10, and the thermoplastic synthetic resin sheet becomes the outer sleeve 3 Of the lower end 11 of, close contact with the lower end of the folded piece 12,
The sheet also comes into close contact with the upper end 16 of the folded piece 12, and the folded piece 12 has a height and a depth such that the height of the folded piece 12 formed on the body portion 17 of the plastic container 4 matches the thickness D. The structure is tightly locked in the groove 18, and the outer peripheral surface 19 of the body 17 and the outer peripheral surface 20 below the body formed by the peripheral wall surface 14 of the bottom cavity 8 are formed by a single busbar. It will be located in the same cylinder surface.

Reference numerals 21 and 22 in FIGS. 1 and 2 are vacuum suction ports formed in the lower mold 2.

Although the embodiment described above is an example of vacuum molding, it can be applied to pressure molding in exactly the same manner, and air is satisfactorily discharged from the mold by suction from the vacuum suction port 10.

Of course, the present invention can also be applied to injection molding in which a male core is placed in the upper and lower molds, and in that case, the inwardly projecting portion of the lower end 11 of the outer sleeve 3 becomes an undercut and engages with the core. It is possible to release the molded product from the upper and lower molds by utilizing the pulling-out of the core, and the thickness of the undercut portion is extremely thin. Is easily performed by elastic deformation of.

FIG. 4 is an enlarged cross-sectional view of an essential part of the plastic container 4 molded by the above-described method, showing the inner peripheral surface 15 of the sleeve main body 13 of the outer sleeve 3 through the inner peripheral surface 23 of the folded piece 12. , A series of plastic containers 4 connected to the outer peripheral wall 25 of the bottom 24 of the plastic container 4 is formed.
The folded groove 12 formed in the body portion 17 of the outer sleeve 3 holds and clamps the folded piece 12 of the exterior sleeve 3 from the three sides of the upper and lower ends and the inner peripheral surface 23. Thus, the outer sleeve 3 is prevented from falling out of the plastic container 4 or being displaced.

FIG. 5 shows an example of a longitudinal section of a plastic container molded according to the present invention. The left side of FIG. 5 shows an outer flange 27 formed on the upper end of a body portion 26 of the plastic container. On the right side of the figure, a skirt 29 is formed on the outer edge of the outward flange 28, and the other structures are the same as those shown in FIG.

Needless to say, a stacking prevention structure is added to the rim of the container as needed.

As shown by the chain line in FIG. 2, a vacuum suction port 30 is opened above the body cavity 5 of the upper mold 1, and the sleeve main body 13 of the outer sleeve 3 is vacuum-sucked to thereby make the exterior inside the mold. The position of the sleeve 3 may be held more reliably.

Further, the folded piece formed at the lower end of the outer sleeve may be cut out at the corner portion in the case of molding a rectangular tubular container, for example.

[Advantages] The present invention has the above-described configuration and operation, and supports the lower end of the exterior sleeve at the step of the upper end of the lower mold that abuts the lower end of the upper mold, and the upper and lower parting surfaces. The outer sleeve can be securely held at a fixed position in the mold by the vacuum suction action from the vacuum suction port provided at the position so that the upper and lower molds that are integrally combined are reversed for molding. Even so, there is an effect that the outer sleeve may fall out of the mold or the position may be displaced, so that the work of inserting the outer sleeve into the upper mold can be simplified, speeded up, and ensured.

Further, the support of the lower end of the outer sleeve by the step portion is the support in the state where the folded piece at the lower end of the outer sleeve projects inward of the mold, and when the body of the plastic container is molded,
The folded piece is held and pinched by the concave groove formed in the body portion of the plastic container from the three directions of the upper edge, the lower edge and the inner peripheral surface. There is an effect that it is possible to prevent the outer sleeve from coming off from the plastic container and the occurrence of displacement without adding any additional material.

Further, the lower end of the outer sleeve supported by the step of the lower mold is brought into close contact with the body cavity and the step by the suction action from the vacuum suction port of the parting surface, and between the outer surface of the lower end and the cavity. Since no void is formed, the effect of reliably preventing the plastic from flowing into the outer surface of the outer sleeve can be achieved even when applied to injection molding.

Further, since the outer peripheral surface of the outer sleeve is coated with a lubricant, it is possible to smoothly release from the upper mold, and it is possible to follow high-speed molding even when the draft is small.

As described above, since the outer sleeve and the body of the plastic container are locked only by the folded piece and the groove of the body, the reheat adhesive coating is formed on the inner surface of the outer sleeve. Not only is it unnecessary, but to prevent the exterior sleeve from falling off on the body, there is no need to form a protruding portion that protrudes outward, and it is possible to make the body cavity a smooth cylindrical surface of a single busbar. The use of an upper mold having a simple structure enables the molding speed to be further improved, which in turn makes it possible to further reduce the product cost.

In addition, since the upper mold and the lower mold are used, the degree of freedom in designing the bottom cavity formed in the separate lower mold is increased, and the upper mold and the lower mold are processed by separating them. This also has the advantage that the product cost can be reduced.

INDUSTRIAL APPLICABILITY The method of the present invention has great versatility in that it can be applied to any of the vacuum forming, pressure forming, and injection forming methods. In particular, when applied to injection molding, the folding piece of the outer sleeve is held and sandwiched. By using the undercut structure of the concave groove formed in the body of the plastic container under pressure, the molded product can be taken out together with the core from the so-called cavity consisting of the upper mold and the lower mold, and the molded product of the core can be removed. It also has the advantage that it can be taken out easily.

[Brief description of drawings]

FIG. 1 is an enlarged vertical sectional view showing a molding state of a main part of an embodiment, FIG. 2 is an enlarged vertical sectional view showing an upper die and a lower die shown in FIG. 1, and FIG. 3 is an exterior sleeve. FIG. 4 is an oblique view showing an example as a partial cross section, FIG. 4 is an enlarged vertical sectional view of an essential part of a plastic container molded by the means shown in FIG. 1, and FIG. 5 is another example of the plastic container molded according to the present invention. FIG. 1: Upper mold, 2: Lower mold, 3: Exterior sleeve, 4: Plastic container, 5: Body cavity, 6: Lower end, 7: Step, 8: Bottom cavity, 9: Upper end, 10: Vacuum suction port, 11: Lower end, 13: Mainly sleeve, 15: Inner peripheral surface, 17: Body part, 18: Recessed groove, H: Height, W: Width,
θ: draft.

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Claims (2)

[Claims] 1. A step portion which is continuous with the body cavity and has a gradually reduced diameter with respect to a lower end of an upper die having a body cavity having a cylindrical surface of the same wall and having a draft in an opening direction. When,
The upper end of the lower mold having a bottom cavity following the step is brought into contact, at least the minute gap between the parting surfaces of both molds is used as a vacuum suction port, the outer peripheral surface is lubricated, and the lower end is inwardly upward. The outer sleeve having the folded-back piece is inserted into the upper mold and brought into close contact with the body cavity, and the lower end of the outer sleeve is supported by the step of the lower mold so that the folded-back piece projects inward. After the outer sleeve is held in the mold by the suction action from the suction port, the outer sleeve has an outer sleeve that is formed only on the inner peripheral surface of the outer sleeve and is molded to form a continuous plastic body portion at the bottom of the container. Manufacturing method of plastic container. 2. The method for producing a plastic container having an outer sleeve according to claim 1, wherein only the sleeve main body side of the lower end of the outer sleeve which overlaps the folded piece is supported by the lower mold step.