This application claims priority to Japanese Patent Application No. 2020-105330, filed Jun. 18, 2020, entitled “INJECTION MOLDING MOLD PREFORM MOLDING METHOD, AND METHOD FOR PRODUCING HOLLOW ARTICLE”, the entirety of which is incorporated herein.
The present invention relates to an injection molding mold for obtaining a preform from a molten resin, a preform molding method using the injection molding mold, and a method for producing a hollow article.
Conventionally, various products have been distributed which have been produced by blow molding an injection molded preform to produce a hollow article, and filling the hollow article with a content and attaching a cap thereto. Then, as is often found in a beverage container such as a PET bottle, a support ring portion extending outward is integrally provided in a hollow article which has been produced by blow molding a preform.
For example, as illustrated in
In a beverage container or the like using a PET bottle, a cap having a tamper evidence ring is attached for the purpose of preventing tamper opening. Then, when the beverage container is opened, the tamper evidence ring is engaged with a coupler, so that the tamper evidence ring is allowed to remain on the neck portion of the container. The support ring portion also serves to receive the tamper evidence ring so that the resealed cap and the tamper evidence belt are not separated away from each other too much.
Some products have been designed to prevent tampering by capping the mouth of a container with an ordinary cap, and then covering the top surface of the cap over the support ring portion below the cap with a shrink film and shrinking the shrink film. In these products, when the opening operation is performed without removing the shrink film, the shrink film is detached from the support ring portion, so that one can visually confirm that the opening operation has been performed.
When the support ring portion is gripped with a dedicated tool for the purpose of conveying, transferring, capping, and the like on the filling line of the content, burrs tend to be generated on the lower surface of the support ring portion by sliding the dedicated tool thereunder. Patent Literature 2 shows a device as a measure against this problem where the burr is made inconspicuous by forming a step on the lower surface of the support ring portion.
As described above, the support ring portion is used at the time of conveying the hollow articles or capping, or as a portion for receiving the tamper evidence belt or catching the shrink film as described above.
However, the use applications of the support ring portion are not limited to particular ones.
Patent Literature 1: Japanese Patent Application Laid-Open No. 2007-099381 (in particular, see
When a molten resin is injected into an injection molding mold to mold a preform and the resulting preform is blown to produce a hollow article, an injection molding mold is used although it is not limited to the production of a PET bottle. Such an injection molding mold is formed by superimposing a lip mold on an injection cavity mold and placing an injection core mold in the injection cavity mold through the lip mold.
In the injection molding mold, a support ring molding portion for molding the support ring portion may be provided at a predetermined height position inside the lip mold. Further, in order to ensure the strength of the mold, a parting line where the lip mold and the injection cavity mold are superimposed on each other is often set at the position of the support ring molding portion.
Incidentally, a technique of increasing the production efficiency of a hollow article has been adopted. The technique includes shortening the injection cooling time at the stage of molding a preform to release the preform, of which the resin is kept in a softened state at a high temperature, at an early stage from the injection molding mold. In the production of the hollow article with this technique performed, an injection molding mold in which the parting line is set at the position of the support ring molding portion may sometimes be adopted.
When a preform which is kept in a softened state at a high temperature is released at an early stage from the above-mentioned injection molding mold, the base portion of the support ring portion is easily deformed by insufficient cooling. This insufficient cooling is due to the too large wall thickness of the base portion of the support ring portion of the preform—that is, the too thick neck portion of the preform. Therefore, the following problems may occur.
When a preform 142 as illustrated in
When the base portion 146 of the support ring portion 145 moves to the center side of the preform 142 to be recessed and deformed, the trunk portion 147 of the preform 142 is deformed to be substantially oval in a horizontal cross-sectional shape as illustrated in
To avoid problems caused by insufficient cooling of the base portion 146 of the support ring portion 145, it would be necessary to extend the injection cooling time. Therefore, at present, it is impossible to shorten the cycle time of molding the preform.
In view of the above-mentioned circumstances, in order to solve the problem in which, when a preform in a state where the preform is easily deformed due to higher heat amount of the resin within an injection molding mold is released at an early stage from the injection molding mold by shortening the injection cooling time, the preform trunk portion is easily deformed, an object of the present invention is to shorten the injection cooling time before releasing the preform at an early stage from the injection molding mold to shorten the cycle time of molding the preform.
The present invention has been made in consideration of the aforementioned problems, and can provide an injection molding mold including an injection cavity mold, a lip mold to be superimposed on the injection molding mold, and an injection core mold to be placed inside the lip mold and the injection cavity mold. The injection molding mold is for use in molding a preform. This injection molding mold includes a support ring molding portion at a position corresponding to a parting line where the injection cavity mold and the lip mold are superimposed on each other, and further includes a trunk support portion configured to support a preform trunk portion at a time of releasing the preform in a non-contact manner. The trunk support portion is formed on an outer end inner surface portion of the support ring molding portion in the lip mold to protrude inward the injection molding mold. As a result, the foregoing problems can be solved. The ‘outer end inner surface portion’ corresponds to an inner surface (inner periphery) of an outer end in a radial direction of the support ring molding portion (support ring molding space) in the rip mold.
In the injection molding mold of the present invention, the trunk support portion may be provided continuously along the circumferential direction of the support ring molding portion.
Alternatively, in the injection molding mold of the present invention, the trunk support portion may be provided discontinuously along the circumferential direction of the support ring molding portion.
In the injection molding mold of the present invention, the support ring molding portion can be formed in a substantially square shape in plan view, and the trunk support portion can be positioned at corners of the support ring molding portion with the substantially square shape.
In the injection molding mold of the present invention, the trunk support portion may preferably be provided at a position along the parting line or at a position close to the parting line.
Another aspect of the present invention is to provide a method for molding a preform including filling a molten resin into any of the forgoing injection molding molds to mold a preform with a support ring portion integrally formed therewith, and releasing the preform from the injection cavity mold in a state of the trunk support portion of the lip mold receiving the support ring portion of the preform from below and supporting the preform trunk portion in a non-contact manner. As a result, the foregoing problems can be solved.
Still another aspect of the present invention is to provide a preform molded by the foregoing method for molding a preform. The preform is configured to include a recess formed at an outer end of a support ring portion by the trunk support portion of the lip mold. As a result, the foregoing problems can be solved.
Still another aspect of the present invention is to provide a method for producing a hollow article including filling a molten resin into any of the forgoing injection molding molds to mold a preform with a support ring portion integrally formed therewith, releasing the preform from the injection cavity mold in a state of the trunk support portion of the lip mold receiving the support ring portion of the preform from below and supporting the preform trunk portion in a non-contact manner, and blow molding the released preform to form a hollow article. As a result, the foregoing problems can be solved.
According to the injection molding mold of the present invention, the trunk support portion provided on the outer end inner surface portion of the support ring molding portion of the lip mold is disposed on a side closer to the parting line away from the inner top surface of the support ring molding portion, so that the preform to be injection molded is configured to have a jaw-shaped portion riding on the trunk support portion.
Then, when the injection core mold is extracted from the injection cavity mold and the lip mold after a required time has passed since the molten resin was filled as well as the lip mold is released from the injection cavity mold, the trunk support portion of the lip mold supports the support ring portion of the preform. Since the support ring portion is not deformed to sag downward, the base portion of the support ring portion is not deformed due to rotation or the like.
Since the support ring portion is prevented from sag downward or the base portion is prevented from being deformed in this manner, a change of flattening of the cross-section in the horizontal direction does not occur in the preform trunk portion. Furthermore, the lip mold can maintain the shape of the preform trunk portion without being in contact with the preform trunk portion while the support ring portion of the preform is interposed therebetween. Therefore, the preform trunk portion does not remain in the injection cavity mold, so that the entire preform is properly released.
According to the injection molding mold of the present invention, the trunk support portion is provided continuously along the circumferential direction of the support ring molding portion. Thus, it is possible to more reliably maintain the shape of the preform trunk portion in the circumferential direction.
Alternatively, according to the injection molding mold of the present invention, the trunk support portion is provided discontinuously along the circumferential direction of the support ring molding portion. Thus, it is possible to more reliably maintain the shape of the preform trunk portion in the circumferential direction.
According to the injection molding mold of the present invention, the support ring molding portion is formed in a substantially square shape, and the trunk support portion is configured to be positioned at the corners of the support ring molding portion. Thus, even when the support ring portion of the preform to be molded is formed in a substantially square shape in plan view, it is possible to reliably maintain the shape of the preform trunk portion in the circumferential direction.
According to the injection molding mold of the present invention, the resin thickness on the upper side of the trunk support portion is not reduced, and thus, even when the trunk support portion supports from below when releasing the preform, the resin portion riding on the trunk support portion can be prevented from being deformed.
Further, according to the method for molding a preform of the present invention, when the injection core mold is extracted from the injection cavity mold and the lip mold as well as the lip mold is released from the injection cavity mold, the trunk support portion supports the support ring portion of the preform from below. At that time, free movement in the base portion of the support ring portion is restricted, and the trunk support portion can maintain the shape of the preform trunk portion in plan view without being in contact with the preform trunk portion.
Therefore, when the preform together with the lip mold is released from the injection cavity mold, the preform trunk portion becomes properly separated from the injection cavity mold, so that releasing of the preform is properly performed. That is, in the conventional technology, a portion of the preform, of which the resin is kept in a softened state at a high temperature, is in abut contact with the inner surface of the injection cavity mold to be caught, and thereby a part of the preform trunk portion has remained in the injection cavity mold. Such a conventional problem does not arise.
According to the preform of the present invention, a portion in which the trunk support portion of the lip mold has been located is formed as a recess at the outer end of the support ring portion. Thus, since the recess is disposed at the outer end of the support ring portion, the appearance of the support ring portion is not seriously impaired.
Further, according to the method for producing a hollow article of the present invention, the preform can be released at an early stage even in a state in which the time for injection cooling the preform is shortened, so that the cycle time of molding the preform is shortened. Therefore, the production efficiency of the hollow article can be increased.
A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:
Injection stretch blow molding machine:
Next, the present invention will be described in detail on the basis of embodiments illustrated in
The injection cavity mold 2 includes a gate at its lower portion (bottom), where a runner nozzle 6 of a hot runner apparatus is disposed. A not-shown injection apparatus can inject a molten resin into the preform forming space 5 via the hot runner apparatus.
The injected molten resin in the injection molding mold 1 is cooled to complete the molding of the preform. Then, in the injection stretch blow molding machine, the injection molding mold 1 which has been closed is opened so that the preform is transferred from the injection molding section to the blow molding section in a state of being held by the lip mold 3.
The preform is stretched in the blow mold at the blow molding section while being blown with compressed air, thereby stretch blow molding the preform into a hollow article. After that, the hollow article is transferred from the blow mold to the ejection section in a state where the mouth portion of the hollow article is held by the lip mold 3. In this ejection section, the lip mold 3 is opened to release the mouth portion of the hollow article, so that the hollow article is sent out of the apparatus.
In the injection molding section, when the preform is molded in the injection molding mold 1, the injection core mold 4 is pulled up, and the preform is released at an early stage by pulling up the lip mold 3 from the injection cavity mold 2 together with the preform. As a result, the preform in a state in which a core layer of the preform (the portion sandwiched between the inner and outer skin (surface) layers of the preform) is kept at a high temperature is transferred to the blow molding section, where the preform is stretched and blow molded into the hollow article.
Lip mold:
The lip mold 3 of the injection molding mold 1 configured to mold the preform 11 includes a support ring molding portion 14 (space for molding the support ring portion 13) as illustrated in
Trunk support portion:
As illustrated in
Further, the trunk support portion 16 is disposed in the lip mold 3 at a position proximate to the parting line 7 of the lip mold 3, i.e., a position proximate to the lowermost surface position. Thus, a gap is formed between the trunk support portion 16 and the top surface 17 of the support ring molding portion 14. Needless to say, the gap between the trunk support portion 16 and the top surface 17 is a space into which the molten resin properly enters at the time of injection.
When the preform is molded with this injection molding mold 1, a molten resin is injected and the preform is released at an early stage by shortening the cooling time.
In a general preform including the preform 11 of the present embodiment, the preform trunk portion 10 including a base portion 131 of the support ring portion 13 as the upper end side is a portion to be shaped (stretch blow molded), and therefore, the wall thickness is large. In the case of releasing at an early stage, the inner and outer skin layers of the preform trunk portion 10, i.e., the resin layer on the inner surface side and the resin layer on the outer surface side, have a hardness capable of maintaining the shape of the preform trunk portion 10. On the other hand, the intermediate layer (core layer) between the inner and outer skin layers is softened at a high temperature to maintain a low viscosity molten state.
As described above, since the base portion 131 of the support ring portion 13 of the preform is thick, the heat amount of the intermediate layer thereof is large. Thus, when the preform is released at an early stage, heat from the intermediate layer is transmitted toward the inner and outer skin layers, and the base portion 131 becomes likely to be deformed.
In a conventional case, with reference to
In this embodiment, the trunk support portion 16 of the lip mold 3 receives the support ring portion 13 from below, so that a change such as sagging of the support ring portion 13 can be prevented, and the rotation of the base portion 131 in the vertical direction can be suppressed. That is, the trunk support portion 16 can support the preform trunk portion 10 through the support ring portion 13 in a non-contact manner so as not to deform the preform trunk portion 10. Therefore, the shape of the preform trunk portion 10 is not impaired, and the preform can be released properly. Since the support is achieved in a non-contact manner, there is no disadvantage that the support mark is attached to the inner and outer skin layers of the preform trunk portion 10.
The injection stretch blow molding machine transfers the preform 11 released at the injection molding section to the blow molding section. In this blow molding section, the preform 11 is blow molded into the hollow article 18. The obtained hollow article 18 is transferred from the blow molding section to the ejection section. As described above, the hollow article 18 is sent out of the apparatus, in the ejection section.
Discontinuous trunk support portion:
In the lip mold 3 in the foregoing embodiment, the trunk support portion 16 has been described to be continuous along the circumferential direction of the support ring molding portion 14. However, as illustrated in
Skirt-shaped support ring portion:
The support ring molding portion 14 in the above-described embodiment has been described to mold the support ring portion 13 which is formed in a substantially flat plate shape and protrudes from the periphery of the neck portion 12 of the preform 11. However, the present invention is not limited to the support ring portion 13 in a flat plate shape in a vertical cross-section. The vertical cross-sectional shape of the support ring portion 13 may take shapes other than the flat plate shape as necessary.
The outer end inner surface portion 15 of the support ring molding portion 14 of the lip mold 3 includes the trunk support portion 16 formed discontinuously along the circumferential direction of the support ring molding portion 14 in the same manner as in the foregoing embodiment.
The left half of
The right half of
Support ring portion with flat shape:
In the present invention, the planar shape of the support ring portion 13 is not limited to a circle.
As shown in a state in which the lip mold 3 is viewed from below, in this embodiment, the support ring molding portion 14 has a substantially rectangular planar shape. The support ring molding portion 14 is formed so that a set of parallel side portions of the support ring molding portion 14 is parallel to the split direction of the lip mold 3. Trunk support portions 16 are positioned in respective four corners of the support ring molding portion 14.
For example, when the trunk support portion 16 is designed to be set at the corners of the support ring molding portion 14 having a substantially rectangular planar shape, as illustrated in
The trunk support portion 16 of the aforementioned embodiment also has a role of maintaining the shape of the preform trunk portion 10 so as not to collapse when the preform 11 with the shape illustrated in
Although the trunk support portion 16 is disposed so that a set of side portions thereof is parallel to the split direction of the lip mold 3 in the foregoing embodiments, the trunk support portion 16 may be disposed so that the diagonal direction thereof is aligned with the split direction of the lip mold 3.
Number | Date | Country | Kind |
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2020-105330 | Jun 2020 | JP | national |