INJECTION MOLDING MOLD, PREFORM MOLDING METHOD, AND METHOD FOR PRODUCING HOLLOW ARTICLE

Abstract

When a preform is released at an early stage from an injection molding mold, the injection cooling time is shortened before releasing the preform at an early stage from the injection molding mold to shorten the cycle time of molding the preform while the preform trunk portion is prevented from being deformed. A trunk support portion is formed on an outer end inner surface portion of a support ring molding portion in the lip mold and is configured to support a preform trunk portion at a time of releasing the preform in a non-contact manner.

Claims

1. An injection molding mold for use in molding a preform, comprising: 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, a support ring molding portion is provided at a position corresponding to a parting line where the injection cavity mold and the lip mold are superimposed on each other, the support ring molding portion being spaced to form a support ring which projects outwardly from a neck portion of the preform, and a trunk support portion configured to support a preform trunk portion at a time of releasing the preform in a non-contact manner 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 to form a recess in an outer end surface of the support ring.

2. The injection molding mold according to claim 1, wherein the trunk support portion is provided continuously along a circumferential direction of the support ring molding portion.

3. The injection molding mold according to claim 1, wherein the trunk support portion is provided discontinuously along a circumferential direction of the support ring molding portion.

4. The injection molding mold according to claim 1, wherein the support ring molding portion is formed in a substantially square shape in plan view, and the trunk support portion is positioned at corners of the support ring molding portion with the substantially square shape.

5. The injection molding mold according to claim 1, wherein the trunk support portion is provided at any of a position along the parting line and a position close to the parting line.

6. A method for molding a preform comprising: filling a molten resin into the injection molding mold according to claim 1 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.

7. A method for producing a hollow article comprising: filling a molten resin into the injection molding mold according to claim 1 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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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:

[0039] FIGS. 1A and 1B illustrate an injection molding mold in an injection stretch blow molding machine according to the present invention where FIG. 1A is an explanatory view illustrating the injection molding mold in a closed state and FIG. 1B is an explanatory enlarged view illustrating a support ring molding portion;

[0040] FIG. 2 is an explanatory view illustrating a preform that is molded by means of the injection molding mold as seen from the side;

[0041] FIG. 3 is an explanatory view illustrating the same preform as seen from above;

[0042] FIG. 4 is an explanatory view illustrating a state in which the injection molding mold is filled with a resin;

[0043] FIG. 5 is an explanatory view illustrating a state in which the preform is released;

[0044] FIG. 6 is an explanatory view illustrating an example of a blow molded hollow article;

[0045] FIG. 7 is an explanatory view illustrating a lip mold in which a trunk support portion is discontinuously provided;

[0046] FIG. 8 is an explanatory view illustrating an injection molding mold configured to obtain a skirt-shaped support ring portion;

[0047] FIG. 9 is an explanatory view illustrating a preform for obtaining a skirt-shaped support ring portion, and a hollow article;

[0048] FIGS. 10A and 10B illustrate a support ring molding portion of the lip mold, where FIG. 10A is an explanatory view illustrating a state of being closed, FIG. 10B is an explanatory view illustrating a state of being opened;

[0049] FIGS. 11A and 11B illustrate the trunk support portion in a vertical cross-section, where FIG. 11A is an explanatory view illustrating a state in which the trunk support portion is positioned above the parting line and FIG. 11B is an explanatory view illustrating an example in which the trunk support portion is provided along and at the parting line position;

[0050] FIG. 12 is an explanatory view illustrating another aspect of a preform;

[0051] FIG. 13 is an explanatory view illustrating a hollow article molded from the preform of FIG. 12;

[0052] FIGS. 14A and 14B illustrate a conventional preform molding failure when released, where FIG. 14A is an explanatory view illustrating deformation of the preform trunk portion in releasing and FIG. 14B is an explanatory enlarged view illustrating a conventional support ring molding portion; and

[0053] FIG. 15 is an explanatory view showing a preform deformed in the injection cavity mold.

DETAILED DESCRIPTION

[0054] Injection stretch blow molding machine:

[0055] Next, the present invention will be described in detail on the basis of embodiments illustrated in FIGS. 1A to 13. An apparatus for producing a hollow article made of a synthetic resin includes an injection stretch blow molding machine in which a preform is molded using, for example, PET as a resin material, and the preform is stretched and blow molded into a hollow article. The injection stretch blow molding machine includes: an injection molding section in which a molten resin is injected from an injection apparatus to mold a preform; a blow molding section in which the preform transferred from the injection molding section is stretched and blown to form a hollow article; and a ejection section in which the hollow article transferred from the blow molding section is sent out of the apparatus.

[0056] FIGS. 1A and 1B illustrate an injection molding mold 1 that is incorporated into the injection molding section of the injection stretch blow molding machine. The injection molding mold 1 can form a preform forming space 5 thereinside. Specifically, the preform forming space 5 is formed by superimposing a lip mold 3 on an injection cavity mold 2, and inserting an injection core mold 4 from above toward the inside of the injection cavity mold 2 through the inside of the lip mold 3 to place the injection core mold 4 therein.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] FIG. 2 illustrates a preform 11. The preform 11 includes a mouth portion 8 with an outer screw 9 formed therein, and a preform trunk portion 10 below the mouth portion 8. The preform 11 further includes a neck portion 12 connecting the upper end of the preform trunk portion 10 to the mouth portion 8, and a support ring portion 13 which projects outwardly around the neck portion 12. Accordingly, the preform 11 is configured to include a portion below the lower end of the neck portion 12 as a portion to be shaped as an accommodating portion of the hollow article.

[0062] Lip mold:

[0063] 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 FIGS. 1A and 1B. The support ring molding portion 14 is provided at a position corresponding to a parting line 7 where the injection cavity mold 2 and the lip mold 3 are superimposed on each other. The support ring molding portion 14 can function as a space for forming the support ring portion 13 of the preform 11. Note that the lip mold 3 is a mold composed of a pair of split molds that can be integrated and separated in a certain radial direction.

[0064] Trunk support portion:

[0065] As illustrated in FIGS. 1A and 1B, the support ring molding portion 14 in the lip mold 3 has an outer end inner surface portion 15 where a trunk support portion 16 is provided. The trunk support portion 16 is configured to support the preform trunk portion 10 at the time of release of the preform 11 in a non-contact manner. Then, the trunk support portion 16 is integrally provided to the lip mold 3 so as to project in a convex state toward the inside of the lip mold 3 (inside the mold). In this embodiment, the trunk support portion 16 is continuously formed along the circumferential direction of the support ring molding portion 14 with the constant vertical cross-sectional shape.

[0066] 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.

[0067] 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. FIG. 4 illustrates a state in which the molten resin is injected into the injection molding mold 1 to fill the preform forming space 5. Furthermore, FIG. 5 illustrates a state in which the injection core mold 4 is pulled up to be extracted, and the lip mold 3 together with the preform 11 is further pulled up from the injection cavity mold 2 to release the preform 11 from the injection cavity mold 2.

[0068] 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.

[0069] 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.

[0070] In a conventional case, with reference to FIG. 14, when the lip mold 143 is raised, the base portion 146 itself rotates in the vertical direction and deformed so that the support ring portion 145 sags. This deformation causes the preform trunk portion 147 below the support ring portion 145 to be flattened in the horizontal cross-sectional shape. Due to this, the pressing pressure of the preform trunk portion 147, which is in contact with the injection cavity mold 144, against the injection cavity mold 144 is increased, there is a problem that the preform trunk portion 147 stretches or the like to remain in the injection cavity mold 144.

[0071] 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.

[0072] 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.

[0073] FIG. 6 illustrates a hollow article 18 thus produced. A recess 19 formed by the trunk support portion 16 of the lip mold 3 is disposed in the outer end surface of the support ring portion 13 of the hollow article 18. The recess 19 in the illustrated embodiment is a groove continuous along the circumferential direction of the support ring portion 13, and thus, does not impair the appearance of the support ring portion 13.

[0074] Discontinuous trunk support portion:

[0075] 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 FIG. 7 representing another embodiment, the trunk support portion 16 may be discontinuously disposed along the circumferential direction of the support ring molding portion 14.

[0076] Skirt-shaped support ring portion:

[0077] 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.

[0078] FIG. 8 illustrates a support ring molding portion 14 with the injection molding mold 1 partially illustrated in cross-section. The support ring molding portion 14 has a vertical cross-sectional shape provided with a downwardly substantially arcuate part. The vertical cross-sectional shape of the support ring molding portion 14 of the lip mold 3 is a substantially hook shape. The injection cavity mold 2 close to the support ring molding portion 14 has a shape that protrudes upward at the portion corresponding to the base end portion of the support ring portion. See FIG. 8.

[0079] 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.

[0080] The left half of FIG. 9 illustrates a partial cross-section of the preform 11 to be molded from the injection molding mold 1 having the foregoing support ring molding portion 14. The preform 11 is formed to have a shape in which the support ring portion 13 is integrally formed around the neck portion 12 into a skirt shape by the support ring molding portion 14.

[0081] The right half of FIG. 9 illustrates a part of the hollow article 18 obtained by blow molding the preform 11 released at an early stage. The base end of the neck portion 12 is provided so as to expand in diameter at the lower surface position of the support ring portion 13. The trunk support portion 16 is formed discontinuously. Thus, recesses 19 appearing on the outer end surface of the support ring portion 13 are also formed discontinuously.

[0082] Support ring portion with flat shape:

[0083] In the present invention, the planar shape of the support ring portion 13 is not limited to a circle. FIGS. 10A and 10B illustrate a lip mold 3 with a support ring molding portion 14 corresponding to a substantially rectangular support ring portion 13.

[0084] 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. FIG. 10A illustrates a state in which the lip mold 3 is closed, and FIG. 10B illustrates a state in which the lip mold 3 is opened.

[0085] 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 FIG. 11A representing the corners of the support ring forming portion 14 in a vertical cross-section, the trunk support portion 16 is provided at a position above the position corresponding to the parting line 7 so as to protrude toward the center of the mold as in the foregoing embodiments. Further, as shown in FIG. 11B, it is also possible to arrange the trunk support portion 16 at the position of the parting line 7 with the lower surface thereof along the position of the parting line 7.

[0086] 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 FIG. 12 is released. For the preform 11 of the embodiment illustrated in FIG. 12, the lower portion of the support ring portion 13 is designed to have a tapered shape reduced in diameter in the downward direction in order to obtain a hollow article 18 illustrated in FIG. 13. Since the preform 11 is molded by the injection molding mold to which the trunk support portion 16 is provided, the preform shape does not collapse even when the preform 11 is released at an early stage.

[0087] 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.

Reference Signs List

[0088] 1 injection molding mold [0089] 2 injection cavity mold [0090] 3 lip mold [0091] 4 injection core mold [0092] 5 preform forming space [0093] 7 parting line [0094] 8 preform mouth portion [0095] 10 preform trunk portion [0096] 11 preform [0097] 12 neck portion [0098] 13 support ring portion [0099] 14 support ring molding portion [0100] 15 outer end inner surface portion [0101] 16 trunk support portion [0102] 18 hollow article [0103] 19 recess [0104] 141 injection core mold [0105] 142 preform [0106] 143 lip mold [0107] 144 injection cavity mold [0108] 145 support ring portion [0109] 146 base portion [0110] 147 preform trunk portion