Synthetic resin containers and preforms

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]

[0001] The present invention relates to a synthetic resin container and a preform for producing a synthetic resin container by blow molding. [Background technology]

[0002] Conventionally, synthetic resin containers have been used in a wide range of fields as containers for various beverages, seasonings, and the like, by producing a bottomed cylindrical preform using a thermoplastic resin such as polyethylene terephthalate by injection molding, compression molding, or the like, and then molding this preform into a bottle shape by biaxial stretch blow molding.

[0003] In many cases, this type of container has a spirally circumferential screw thread at the container mouth, and the container filled with the contents is sealed by wrapping and screwing a lid onto the container mouth before being put on the market (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-12101 Summary of the Invention [Problem to be solved by the invention]

[0005] In the past, attempts have been made to mold this type of container as thin as possible in order to reduce the weight and cost by reducing the amount of resin used. In recent years, the demand for thinner walls has become increasingly strict, but the thinner the walls become, the lower the rigidity of the container inevitably becomes.

[0006] Therefore, the inventors have conducted extensive research to meet the demand for lighter and less costly containers by reducing the amount of resin in the container mouth so as not to affect the rigidity of the container.

[0007] However, as a result of research by the inventors, we have come to the realization that simply thinning the container mouth to reduce the amount of resin in the container mouth results in problems when tightening and screwing the lid. Specifically, as pointed out in Patent Document 1, changing the inner diameter of the container mouth is undesirable due to its relationship with the mandrel used to transport the preform. On the other hand, reducing the outer diameter of the container mouth to make it thinner results in a larger gap between the threads on the lid and the outer periphery of the container mouth. This can result in the lid rattling when tightening begins, preventing the lid from being tightened coaxially with the container mouth, resulting in the lid being screwed on at an angle, or the tamper-evident band of the lid being subjected to stress and breaking (bridge breakage), resulting in significant loss of commercial value.

[0008] Therefore, the inventors recognized this problem as an oblique overlap when the lid body is wrapped around and screwed onto the mouth of the container, and after extensive research to effectively avoid this while reducing the amount of resin at the mouth of the container, they were able to complete the present invention. [Means for solving the problem]

[0009] The synthetic resin container according to the present invention is a synthetic resin container having a mouth, a shoulder, a body, and a bottom, and a spirally circumferential screw thread is provided on the side surface of the opening end of the mouth, and the screw thread Screw Valley Between However, the thread cutting start side near the opening end of the mouth Part of from Following the threads The thread root diameter gradually decreases as it becomes deeper, or gradually becomes deeper and then reaches a constant depth, and the portion of the mouth portion below the thread of the screw is reduced in diameter relative to the outer diameter of the mouth portion above the thread, and the thread root and the outer circumferential surface are continuous.

[0010] The preform according to the present invention is a preform for producing a synthetic resin container by blow molding, and is molded into a bottomed tubular shape with an open end serving as a mouth portion, and a spirally circumferential screw thread is provided on the side surface of the open end of the mouth portion, and the screw thread Screw Valley Between However, the thread cutting start side near the opening end of the mouth Part of from Following the threads The thread root diameter gradually decreases as it becomes deeper, or gradually becomes deeper and then reaches a constant depth, and the portion of the mouth portion below the thread of the screw is reduced in diameter relative to the outer diameter of the mouth portion above the thread, and the thread root and the outer circumferential surface are continuous. [Effects of the Invention]

[0011] According to the present invention, in a synthetic resin container having a mouth, shoulder, body, and bottom, the weight of the synthetic resin container can be reduced by effectively avoiding diagonal overlap when the lid body is wrapped around and screwed onto the mouth, while reducing the amount of resin in the mouth. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an explanatory diagram showing a schematic relationship between a preform set in a blow molding die and a container formed in a predetermined container shape from the preform in the blow molding die in an embodiment of the present invention. [Figure 2] FIG. 2 is a front perspective view of a mouth portion according to an embodiment of the present invention. [Figure 3] FIG. 2 is a front view of the mouth portion according to the embodiment of the present invention. [Figure 4] FIG. 2 is a plan view of a mouth portion according to an embodiment of the present invention. [Figure 5] 5 is a cross-sectional view taken along the line AA in FIG. 4. [Figure 6] 5 is a cross-sectional view of FIG. 4 taken along line B-B. [Figure 7] 5 is a cross-sectional view taken along CC in FIG. 4. [Figure 8] FIG. 5 is a cross-sectional view taken along the line DD in FIG. 4. [Figure 9]7 is an enlarged end view of the main part of the area enclosed by the chain line in FIG. 6. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is an explanatory diagram that shows the relationship between a preform 1 set in a blow molding mold BM, indicated by a two-dot chain line in the figure, and a container 10 formed from this preform 1 into a predetermined container shape within the blow molding mold BM by biaxial stretch blow molding or the like.

[0015] In this embodiment, the preform 1 can be molded using a thermoplastic resin by injection molding, compression molding, or the like into a bottomed cylindrical shape with one open end serving as a mouth portion 2, and the other end of the preform 1 is closed by a bottom portion 3 molded into a hemispherical shape.

[0016] The thermoplastic resin used can be any resin that can be blow molded. More specifically, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, amorphous polyarylate, polylactic acid, polyethylene furanoate, or copolymers thereof can be used, and ethylene terephthalate-based thermoplastic polyesters such as polyethylene terephthalate are particularly suitable. Two or more of these resins can be mixed, or blended with other resins. Polycarbonate, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene, etc. can also be used. Furthermore, the preform 1 is not limited to being molded into a single layer, but can also be molded into multiple layers including a gas barrier layer or the like depending on the properties required for the container 10.

[0017] The preform 1 is heated as needed to soften it to a state where it can be blow-molded, and then set in the blow mold BM, and the portion from just below the mouth 2 to the bottom 3 is stretched in the axial direction (longitudinal direction) by a stretch rod as needed, and is also stretched in the axial and circumferential directions (lateral directions) by blown air blown into the preform 1. The stretched portions of the preform 1 are then molded into the shoulder 30, body 40, and bottom 50 of the container 10.

[0018] In this embodiment, the up / down, left / right and length / width directions of the preform 1 are defined in the state shown in FIG. 1 with the mouth portion 2 facing up, and similarly, the up / down, left / right and length / width directions of the container 10 are defined in the state with the mouth portion 2 facing up.

[0019] As shown in Fig. 1, the mouth 2 of the preform 1 is not stretched by blow molding and becomes the mouth 2 of the container 10 as is, and is indicated by the same reference numeral in the figure. The mouth 2 of the preform 1, and by extension the mouth 2 of the container 10, is the portion that serves as the injection outlet for the contents, and a screw thread 21 for tightening and screwing a lid (not shown) is provided spirally around the side surface of the opening end of the cylindrically formed mouth 2.

[0020] In the following description, unless otherwise specified, the mouth portion 2 of the preform 1 and the mouth portion 2 of the container 10 will not be distinguished from each other, and will be described as a common portion.

[0021] An annular neck ring 22 that protrudes outward in the circumferential direction is provided at the mouth 2. The preform 1 is usually formed into the shoulder 30, body 40, and bottom 50 of the container 10, as described above, by extending the portion of the preform 1 below the neck ring 22, starting from the portion directly below the neck ring 22.

[0022] A bead ring 23 is provided in a circumferential direction in the region between the thread 21 of the mouth portion 2 and the neck ring 22. A flap or a hook formed on a tamper-evident band of the lid (not shown) is engaged with the bead ring 23.

[0023] Here, Figure 2 is an oblique view focusing only on the mouth portion 2, Figure 3 is a front view of the same, Figure 4 is a plan view of the same, Figure 5 is a cross-sectional view taken along line AA in Figure 4, Figure 6 is a cross-sectional view taken along line BB in Figure 4, Figure 7 is a cross-sectional view taken along line CC in Figure 4, and Figure 8 is a cross-sectional view taken along line DD in Figure 4.

[0024] In the examples shown in these figures, the mouth portion 2 is formed so that the thread 21, which has approximately 1.8 turns (approximately 650° around the central axis C) spiraling around the side of the mouth portion 2, gradually deepens and then becomes a constant depth as it turns around the mouth portion 2 from the thread cutting start side near the open end of the mouth portion 2 until it turns around the mouth portion 2 once, and the thread root diameter Dv gradually decreases.

[0025] More specifically, if you follow the thread 21 from the start of thread cutting, at the point 21se (hereinafter referred to as the ``starting point of the effective thread'') where the thread diameter Dm begins to become constant (see Figure 4), the thread valley 21v begins to deepen (it starts to deepen so that there is no step in the thread valley 21v), and from there, the thread valley 21v gradually deepens up to the point 90° around the central axis C, and then the thread valley 21v smoothly connects so that there is no step in the thread valley 21v, and the thread valley diameter Dv is gradually reduced so that the depth of the thread valley 21v becomes constant (see Figures 6, 7, and 8).

[0026] Furthermore, in the example shown in the figure, the mouth portion 2 is formed so that it has a reduced diameter portion 2dr in the portion below the thread 21 of the mouth portion 2, between the thread 21 and the bead ring 23, which is reduced in diameter compared to the outer diameter D2 of the mouth portion 2 in the portion above the thread 21 (the portion located above the first turn of the thread 21), and which continues so that the thread valleys 21v between the threads 21 and the outer surface are smoothly connected.

[0027] According to this embodiment, it is possible to effectively avoid diagonal overlap when wrapping and screwing the lid body onto the mouth portion 2, while reducing the amount of resin in the mouth portion 2, thereby making the container 10 lighter.

[0028] More specifically, by ensuring an outer diameter D2 of the part above the threads 21 of the mouth portion 2 so that the gap between the threads on the lid body and the outer peripheral surface of the mouth portion 2 is small when tightening begins, rattling of the lid body is suppressed when tightening begins, and as a result, diagonal overlap when tightening and screwing the lid body is suppressed (for example, the part above the threads 21 of the mouth portion 2 remains in the conventional design that does not cause diagonal overlap problems), and at the same time, by partially forming the thread valleys 21v between the threads 21 and the part below the threads 21 of the mouth portion 2 to be thin-walled, the amount of resin in the mouth portion 2 can be reduced as much as possible.

[0029] In this embodiment, when reducing the amount of resin in the mouth portion 2, it is preferable to reduce the number of turns of the thread 21 to a degree that does not interfere with the screwing of the lid body, thereby shortening the overall length of the thread 21. More specifically, it is preferable that the number of turns of the thread 21 be 1.6 to 2.2 turns. Furthermore, it is also effective in reducing the amount of resin in the mouth portion 2 to provide a recessed groove 24 as shown in the figure between the bead ring 23 and the neck ring 22 along the circumferential direction to remove weight.

[0030] In the illustrated example, the thread roots 21v between the threads 21 gradually become deeper and then reach a constant depth, but it is also possible to adjust the degree to which the amount of resin in the neck portion 2 is reduced by reducing the thread root diameter Dv so that the thread roots 21v between the threads 21 gradually become deeper until they reach the end of the threads 21. Although not particularly shown, discontinuities can also be formed in the threads 21 as so-called vent slots. In this case, it is preferable that the discontinuities be formed so that the outer peripheral surface of the neck portion 2 and the thread roots 21v are smoothly connected, and that, when the threads 21 have more than two turns, the thread roots 21v adjacent above and below are also smoothly connected.

[0031] Furthermore, when tightening begins, ensuring that the threads on the lid body side are well guided into the thread valleys 21v between the threads 21 of the mouth portion 2 so that they are properly screwed together is also effective in avoiding oblique overlap when tightening and screwing the lid body onto the mouth portion 2. From this perspective, in this embodiment, it is preferable to design the thread 21 so that the thickness T of the thread tip at the effective thread start end 21se of the thread 21 is 30 to 60% of the thread pitch P of the thread 21, and it is more preferable that the thickness T of the thread tip is 30 to 55% of the thread pitch P of the thread 21. More specifically, the thickness T of the thread tip at the effective thread start end 21se of the thread 21 is preferably 1.0 to 1.7 mm.

[0032] Here, the thickness T of the tip of the thread refers to the distance between the intersection of an extension line of the upper surface 21t of the thread that intersects with a vertical line parallel to the central axis C that touches the tip of the thread 21 and an extension line of the lower surface 21b of the thread in a longitudinal section of the thread 21 (a section cut at a plane including the central axis C) (see Figure 9). In addition, the thread pitch P of the screw thread 21 is generally designed according to the thread pitch of the standardized thread on the lid body side, and the thread pitch of the standardized thread on the lid body side is usually about 3.18 mm.

[0033] In addition, in order to ensure that the threads on the lid side are well guided into the thread valleys 21v between the threads 21 on the mouth portion 2 when tightening begins, it is preferable to design the threads 21 so that the elevation angle θe (upward angle with respect to the horizontal plane) on the upper surface side of the threads 21 is 15 to 25°.

[0034] On the other hand, the depression angle θi (a downward angle relative to the horizontal plane) on the lower surface of thread 21 does not significantly affect the guiding of the thread on the lid side. For this reason, it is possible to further reduce the amount of resin in neck portion 2 by designing thread 21 so that the depression angle θi on the lower surface of thread 21 is smaller than the elevation angle θe on the upper surface of thread 21. More specifically, the depression angle θi on the lower surface of thread 21 is preferably 5 to 15°.

[0035] The present invention has been described above by showing preferred embodiments, but it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

[0036] For example, the container 10 can be a so-called round bottle or a rectangular bottle, and the specific shapes of the shoulder 30, body 40, and bottom 50 of the container 10, as well as the capacity of the container 10, can be designed as desired. Furthermore, the method of filling the contents into the container 10 is also arbitrary, and may be either so-called hot filling or aseptic filling. [Explanation of symbols]

[0037] 1 Preform 10 containers 2 Mouth 2dr reduced diameter section 21 threads 21v screw valley 21se Effective thread start 30 Shoulder 40 Torso 50 bottom Dv Thread root diameter D2: The outer diameter of the mouth above the thread T Thread tip thickness P thread pitch θe Elevation angle of the top side of the screw thread θi Depression angle on the underside of the screw thread

Claims

1. A synthetic resin container having a mouth, a shoulder, a body, and a bottom, A side surface of the opening end of the mouth portion is provided with a spirally circumferential screw thread, The thread root diameter gradually decreases so that the thread root between the threads gradually deepens from the thread cutting start portion side near the open end of the mouth portion along the thread, or gradually deepens and then becomes a constant depth, At a position below the thread of the mouth portion, A synthetic resin container characterized in that it has a reduced diameter portion that is reduced in diameter relative to the outer diameter of the mouth portion at a position above the screw thread, and where the screw root and the outer peripheral surface are continuous.

2. 2. The synthetic resin container according to claim 1, wherein the thickness of the tip of the thread at the start of the effective thread of the thread is 30 to 60% of the thread pitch of the thread.

3. 3. The synthetic resin container according to claim 1, wherein the angle of elevation of the upper surface of the screw thread is 15 to 25 degrees.

4. 4. The synthetic resin container according to claim 1, wherein the depression angle on the lower surface side of the screw thread is smaller than the elevation angle on the upper surface side of the screw thread.

5. A preform for manufacturing a synthetic resin container by blow molding, The opening end is formed into a cylindrical shape with a bottom and a mouth portion. A side surface of the opening end of the mouth portion is provided with a spirally circumferential screw thread, The thread root diameter gradually decreases so that the thread root between the threads gradually deepens from the thread cutting start portion side near the open end of the mouth portion along the thread, or gradually deepens and then becomes a constant depth, At a position below the thread of the mouth portion, A preform characterized in that it has a reduced diameter portion that is reduced in diameter relative to the outer diameter of the mouth portion at a portion above the thread, and in which the thread root and the outer peripheral surface are continuous.

6. 6. The preform according to claim 5, wherein the thickness of the tip of the thread at the start of the effective thread of the thread is 30 to 60% of the thread pitch of the thread.

7. 7. The preform according to claim 5, wherein the angle of elevation of the upper surface of the thread is 15 to 25 degrees.

8. The preform according to any one of claims 5 to 7, wherein the depression angle on the lower surface side of the thread is smaller than the elevation angle on the upper surface side of the thread.

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