JP2023075708A - Synthetic resin container and preform - Google Patents

Abstract

To provide a synthetic resin container capable of reducing the resin amount of a mouth part while effectively avoiding oblique capping when seaming a cap to the mouth part and screwing up, in the synthetic resin container having the mouth part, a shoulder part, a belly part, and a bottom part.SOLUTION: A synthetic resin container has a screw thread 21 which spirally goes around a side face of a mouth part 2. In the mouth part 2, the screw thread diameter is reduced while a thread root diameter gradually changes so that a thread root 21v between screw threads 21 is gradually deepened from a threading start portion side close to an opening end of the mouth part 2 up to one turn of the mouth part 2, or so that a thread root 21v between screw threads 21 becomes a constant depth after is gradually deepened. At a region lower than the screw thread 21, the container has a diameter reduction part 2dr which is reduced in diameter with respect to an outer diameter of the mouth part 2 of a region higher than the screw thread 21 and where the thread root 21v between screw threads 21 is continuous to its outer peripheral surface.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a synthetic resin container and a preform for manufacturing a synthetic resin container by blow molding.

Conventionally, thermoplastic resins such as polyethylene terephthalate are used to produce cylindrical preforms with bottoms by injection molding or compression molding, and these preforms are molded into bottles by biaxial stretch blow molding. The container made of the product is used in a wide range of fields as a container containing various beverages, various seasonings, and the like.

In this type of container, in many cases, a helical screw thread is provided at the mouth of the container. The filled container is sealed and then marketed (see, for example, Patent Document 1).

Japanese Unexamined Patent Application Publication No. 2012-12101

For this type of container, attempts have been made to make the container as thin as possible in order to reduce the weight and reduce the cost by reducing the amount of resin used. In recent years, the demand for such thinning has become more and more severe, but it is unavoidable that the more thinning the container becomes, the lower the rigidity of the container becomes.

Accordingly, the present inventors have made extensive studies to meet the demands for weight reduction and cost reduction of the container by reducing the amount of resin in the mouth portion of the container so as not to affect the rigidity of the container.

However, as a result of studies by the present inventors, it has been found that simply making the container mouth thin in order to reduce the amount of resin in the container mouth causes problems when the lid is rolled up and screwed. I came to the knowledge that. That is, as pointed out in Patent Document 1, it is not preferable to change the inner diameter of the container opening in relation to the mandrel for conveying the preform. On the other hand, if an attempt is made to reduce the outer diameter of the container opening to make it thinner, the gap between the screw thread on the lid side and the outer peripheral surface of the container opening becomes larger. As a result, the lid body rattles at the start of seaming, and the lid body is screwed obliquely without being coaxially tightened with the mouth of the container, or a load is applied to the tamper-evident band of the lid body. It may be broken (bridging breakage) by being caught, resulting in a problem that the commercial value is significantly impaired.

Therefore, the present inventors regard such a problem as oblique covering when the lid is wound and screwed onto the container mouth, and effectively avoid this, while reducing the amount of resin in the container mouth. The present invention was completed as a result of earnest studies to reduce it.

A synthetic resin container according to the present invention is a synthetic resin container comprising a mouth portion, a shoulder portion, a body portion, and a bottom portion. is provided, and the thread root between the screw threads gradually deepens while the screw thread makes one turn of the mouth from the side of the threading start portion near the open end of the mouth, or After gradually increasing in depth, the diameter is reduced while the thread root diameter gradually changes so that the depth is constant, and the above-mentioned It is configured to have a diameter-reduced portion that is reduced in diameter with respect to the outer diameter of the mouth portion and that the thread root and the outer peripheral surface are continuous.

Further, a preform according to the present invention is a preform for manufacturing a synthetic resin container by blow molding, and is molded into a bottomed cylindrical shape having a mouth portion at one open end side, and the opening of the mouth portion is formed. A helical screw thread is provided on the side surface of the end side, and the screw thread extends from the thread cutting start side near the opening end of the mouth to the time it turns around the mouth. , so that the thread root between the thread ridges gradually becomes deeper, or so that the thread root diameter gradually changes and then becomes a constant depth, and the diameter is reduced from the thread root of the mouth portion. At a portion lower than the screw thread, a diameter-reduced portion having a diameter smaller than the outer diameter of the mouth portion at a portion higher than the screw thread is provided so that the root and the outer peripheral surface are continuous.

According to the present invention, in a synthetic resin container having a mouth, a shoulder, a body, and a bottom, the mouth is effectively prevented from being obliquely covered when the lid is tightened and screwed to the mouth. By reducing the amount of resin, the weight of the synthetic resin container can be reduced.

1 is an explanatory view schematically showing the relationship between a preform set in a blow molding die and a container molded into a predetermined container shape from this preform in the blow molding die in an embodiment of the present invention; FIG. It is a normal perspective view of the mouth part in embodiment of this invention. It is a front view of the mouth part in embodiment of this invention. FIG. 4 is a plan view of the mouth in the embodiment of the present invention; FIG. 5 is a cross-sectional view taken along line AA of FIG. 4; FIG. 5 is a cross-sectional view taken along the line BB of FIG. 4; FIG. 5 is a cross-sectional view taken along line CC of FIG. 4; FIG. 5 is a cross-sectional view taken along line DD of FIG. 4; FIG. 7 is an end view of a main part showing an enlarged area surrounded by a dashed line in FIG. 6;

Preferred embodiments of the present invention are described below with reference to the drawings.

FIG. 1 shows a preform 1 set in a blow mold BM indicated by a two-dot chain line in the figure, and this preform 1 is molded into a predetermined container shape in the blow mold BM by biaxial stretch blow molding or the like. 1 is an explanatory diagram schematically showing the relationship with a container 10 to be processed. FIG.

In the present embodiment, the preform 1 can be formed into a bottomed cylindrical shape having a mouth portion 2 at one open end by injection molding, compression molding, or the like using a thermoplastic resin. The other end side of is closed by a bottom portion 3 formed in a hemispherical shape.

Any resin that can be blow-molded can be used as the thermoplastic resin to be used. More specifically, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, amorphous polyarylate, polylactic acid, polyethylene furanoate, or copolymers thereof can be used. A terephthalate-based thermoplastic polyester can be preferably used. Two or more of these resins may be mixed, or other resins may be blended. Polycarbonate, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene and the like can also be used.
Moreover, the preform 1 is not limited to being formed in a single layer, but can be formed in multiple layers including a gas barrier layer and the like according to the properties required for the container 10 .

The preform 1 is heated as necessary to be softened so that blow molding can be performed, and then set in the blow mold BM. While being stretched in the axial direction (longitudinal direction) by the stretch rods, the preform 1 is stretched in the axial direction and the circumferential direction (lateral direction) by blow air blown into the preform 1 . The stretched portions of the preform 1 are then formed into the shoulder portion 30 , body portion 40 and bottom portion 50 of the container 10 .

Here, in this embodiment, the vertical and horizontal directions of the preform 1 are defined in the state shown in FIG. Up, down, left, right, and vertical and horizontal directions are defined with 2 facing up.

As shown in FIG. 1, the mouth portion 2 of the preform 1 is not stretched by blow molding and becomes the mouth portion 2 of the container 10 as it is, and is indicated by the same reference numerals in the figure. The mouth portion 2 of the preform 1, and by extension the mouth portion 2 of the container 10, serves as an injection port for the contents. A screw thread 21 for winding and screwing a non-removable lid body is provided so as to spirally go around.

In the following description, unless otherwise specified, the opening 2 of the preform 1 and the opening 2 of the container 10 are not distinguished from each other, and are described as common parts.

The mouth portion 2 is provided with an annular neck ring 22 protruding outward along the circumferential direction. The preform 1 is normally stretched from the portion immediately below the neck ring 22 to the shoulder portion 30, the body portion 40 and the bottom portion 50 of the container 10 as described above. molded.

A bead ring 23 is annularly provided along the circumferential direction between the screw thread 21 of the mouth portion 2 and the neck ring 22 . A flap or hook formed on a tamper-evident band of a lid (not shown) is engaged with the bead ring 23 .

Here, FIG. 2 is a perspective view focusing only on the mouth portion 2, FIG. 3 is a front view of the same, FIG. 4 is a plan view of the same, FIG. 4 is a sectional view taken along line BB of FIG. 4, FIG. 7 is a sectional view taken along line CC of FIG. 4, and FIG. 8 is a sectional view taken along line DD of FIG.

In the example shown in these figures, the mouth portion 2 has a screw thread 21 of approximately 1.8 turns (approximately 650° around the central axis C) spirally circling the side surface of the mouth portion 2 . The thread root diameter Dv is gradually increased so that the thread root 21v between the threads 21 gradually deepens and then reaches a constant depth from the thread cutting start portion near the end until the mouth portion 2 makes one turn. It is formed so as to reduce in diameter while changing.

More specifically, the screw thread 21 is traced from the thread cutting start side, and at a portion (hereinafter referred to as "effective thread start end") 21se (see FIG. 4) where the thread diameter Dm begins to become constant, the screw The root 21v begins to deepen (begins to become deep so as not to cause a step in the thread root 21v), and from there, the thread root 21v gradually deepens to a portion advanced by 90° around the central axis C, and then the screw. The thread root diameter Dv is gradually reduced so that the thread root diameter Dv is gradually changed so that the thread root 21v has a constant depth so as to smoothly connect the root 21v so as not to generate a step (FIG. 6). , FIGS. 7 and 8).

Furthermore, in the illustrated example, a portion (screw The diameter is reduced with respect to the outer peripheral diameter D2 of the mouth portion 2 at the portion located above the first turn of the thread 21), and the diameter is continuously reduced so that the thread root 21v between the screw threads 21 and the outer peripheral surface are smoothly connected. A mouth portion 2 is formed to have a portion 2dr.

According to this embodiment, the weight of the container 10 can be reduced by reducing the amount of resin in the mouth portion 2 while effectively avoiding oblique covering when the lid body is wound and screwed onto the mouth portion 2. can be improved.

More specifically, the outer circumference diameter D2 of the portion above the screw thread 21 of the mouth portion 2 is set so that the gap between the screw thread on the lid side and the outer peripheral surface of the mouth portion 2 at the start of winding is reduced. By ensuring , rattling of the lid at the start of tightening is suppressed, and as a result, oblique covering when tightening and screwing the lid is suppressed (for example, the opening 2 Regarding the part higher than the screw thread 21, it is assumed that the conventional design that does not cause the problem of oblique covering), on the other hand, the screw root 21v between the screw threads 21 By partially forming the lower portion to be thin, the amount of resin in the mouth portion 2 can be reduced as much as possible.

In this embodiment, in order to reduce the amount of resin in the mouth portion 2, the number of turns of the thread 21 is reduced to the extent that the screwing of the lid is not hindered, and the overall length of the thread 21 is shortened. It is preferable to More specifically, the number of turns of thread 21 is preferably 1.6 to 2.2.
Further, it is effective to reduce the amount of resin in the mouth portion 2 by providing a recessed groove 24 between the bead ring 23 and the neck ring 22 along the circumferential direction. .

In the illustrated example, the thread root 21v between the screw ridges 21 gradually deepens and then reaches a constant depth. It is also possible to adjust the extent to which the amount of resin in the mouth portion 2 is reduced by reducing the thread root diameter Dv so that the thread 21v is gradually deepened. Although not specifically shown, the threads 21 can also be provided with discontinuities as so-called vent slots. In this case, the discontinuity is arranged such that the outer peripheral surface of the mouth portion 2 and the thread root 21v are smoothly connected to each other. It is preferable to form

Also, when starting to tighten, the threads on the lid side may be well guided by the thread valleys 21v between the threads 21 of the mouth portion 2 so that the two can be properly screwed together. , is effective in avoiding oblique covering when the lid body is wound and screwed onto the mouth portion 2 . From this point of view, in the present embodiment, the thickness T of the tip of the thread 21 at the effective thread start 21se of the thread 21 is 30 to 60% of the thread pitch P of the thread 21. 21 and more preferably the thickness T of the tip of the thread is 30-55% of the thread pitch P of the thread 21 . More specifically, the thickness T of the tip portion of the thread 21 at the effective thread start end 21se is preferably 1.0 to 1.7 mm.

Here, the thickness T of the tip portion of the screw thread is the screw that intersects a vertical line parallel to the central axis C in contact with the tip of the screw thread 21 in the longitudinal section of the screw thread 21 (the cross section cut along the plane including the central axis C). The distance between the intersections of the extension line of the crest upper surface 21t and the extension line of the thread lower surface 21b (see FIG. 9).
Further, the screw pitch P of the screw thread 21 is generally designed according to the standardized screw pitch of the cover-side screw ridge, and the standardized screw pitch of the cover-side screw ridge is usually 3.18 mm. degree.

In order to ensure that the screw threads on the lid side are well guided by the screw roots 21v between the screw threads 21 of the mouth portion 2 at the start of winding, the elevation angle of the upper surface side of the screw threads 21 (relative to the horizontal plane Preferably, the thread 21 is designed such that the upward angle θe is between 15 and 25°.

On the other hand, the depression angle (downward angle with respect to the horizontal plane) θi of the lower surface side of the screw thread 21 does not greatly affect the guidance of the screw thread on the lid side. Therefore, by designing the screw thread 21 such that the depression angle θi on the lower surface side of the screw thread 21 is smaller than the elevation angle θe on the upper surface side of the screw thread 21, the resin amount of the mouth portion 2 is further reduced. is also possible. More specifically, the depression angle θi on the lower surface side of the thread 21 is preferably 5 to 15°.

Although the present invention has been described above with reference to preferred embodiments, it goes without saying that the present invention is not limited to the above-described embodiments, and that various modifications can be made within the scope of the present invention. Nor.

For example, whether the container 10 is a so-called round bottle or a rectangular bottle is arbitrary, and the specific shape of each part of the container 10, such as the shoulder portion 30, the body portion 40, and the bottom portion 50, and the capacity of the container 10. can be designed arbitrarily.
Moreover, the filling method for filling the contents into the container 10 is also arbitrary, and may be either so-called hot filling or aseptic filling.

1 Preform 10 Container 2 Mouth 2dr Diameter reduction portion 21 Thread 21v Thread root 21se Effective thread starting end 30 Shoulder 40 Body 50 Bottom Dv Thread root diameter D2 Peripheral diameter T of the mouth at a portion higher than the thread Thread tip thickness P Thread pitch θe Elevation angle on the top side of the thread θi Angle of depression on the bottom side of the thread

Claims (8)

A synthetic resin container comprising a mouth, a shoulder, a body, and a bottom,
A helical screw thread is provided on the side surface of the mouth on the open end side,
While the thread makes one turn of the mouth from the threading start side near the open end of the mouth, the root of the thread between the threads gradually deepens, or after it gradually deepens. The diameter is reduced while the thread root diameter gradually changes so that the depth is constant,
At a portion lower than the screw thread of the mouth,
A synthetic resin container, comprising a diameter-reduced portion having a reduced diameter with respect to an outer peripheral diameter of the mouth portion at a portion higher than the screw thread and connecting the thread root and the outer peripheral surface. 2. The synthetic resin container according to claim 1, wherein the thickness of the tip of the thread at the effective thread start end of the thread is 30 to 60% of the thread pitch of the thread. 3. The synthetic resin container according to claim 1, wherein the elevation angle of the upper surface of the thread is 15 to 25 degrees. The synthetic resin container according to any one of claims 1 to 3, wherein the angle of depression on the lower side of the thread is smaller than the angle of elevation on the upper side of the thread. A preform for manufacturing a synthetic resin container by blow molding,
Molded into a bottomed cylindrical shape with a mouth on one end of the opening,
A helical screw thread is provided on the side surface of the mouth on the open end side,
The screw thread gradually deepens or gradually deepens the thread root between the screw threads from the side of the threading start part near the open end of the mouth part to the time when the mouth part is wound around the mouth part. After that, the diameter is reduced while the thread root diameter gradually changes so that it becomes a constant depth,
At a portion lower than the screw thread of the mouth,
A preform comprising a diameter-reduced portion having a reduced diameter with respect to an outer peripheral diameter of the mouth portion at a portion higher than the thread ridge and connecting the thread root and the outer peripheral surface. 6. The preform according to claim 5, wherein the thickness of the tip portion of the thread at the effective thread start end of the thread is 30 to 60% of the thread pitch of the thread. 7. The preform according to claim 5, wherein the elevation angle of the upper surface side of the thread is 15 to 25 degrees. The preform according to any one of claims 5 to 7, wherein the depression angle of the lower surface of the thread is smaller than the elevation angle of the upper surface of the thread.

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