JP7451989B2 - Synthetic resin container - Google Patents

Description

The present invention relates to a synthetic resin container, and particularly to a synthetic resin container suitable for use as a pressure-resistant bottle containing a carbonated beverage.

Conventionally, synthetic resin containers are made by forming a preform using thermoplastic resin such as polyethylene terephthalate, and then molding this preform into a bottle shape by biaxial stretch blow molding, etc. It is used in a wide range of fields as containers for contents.

Among these synthetic resin containers, beverage containers containing carbonated beverages have pressure resistance that can withstand the pressure of carbon dioxide gas, and are self-supporting and stable even if the inside of the container becomes positive pressure. It is required that it be able to stand on its own without being damaged. For this reason, for example, a pressure-resistant bottle is known that includes a bottom portion formed in a so-called petaloid shape, as disclosed in Patent Document 1.

JP2014-172625A

By the way, when such a resin container having a petaloid-shaped bottom is filled with liquid and a positive pressure is created inside the container, the bottom may be deformed or cracked.
Patent Document 1 discloses that cracks occur due to gate marks remaining on the bottom of the preform in a resin container formed by biaxial stretch blow molding, and in order to reduce the stress concentration area. , proposes a structure with a smoothly continuous curved part from the center of the bottom to the ground contact part at the tip of the leg.

On the other hand, the petaloid-shaped legs have a complex surface shape that repeats irregularities so that they partially bulge outward from the container from a roughly hemispherical virtual surface, resulting in stress concentration. Easy to have parts. In order to prevent deformation and cracking when the inside of the container becomes positive pressure, it is necessary to avoid such stress concentration.

The present invention has been made in view of the above-mentioned circumstances, and includes a synthetic resin container having a bottom formed in a so-called petaloid shape, in which a carbonated beverage is filled as the content and sealed, and a positive pressure is created inside the container. An object of the present invention is to provide a synthetic resin container that can suppress stress cracks caused by pressure applied to the inner surface of the bottom when the container is heated.

The synthetic resin container according to the present invention includes a bottom portion in which a plurality of legs are rotationally symmetrical around a central axis and radially arranged at equal intervals, and the legs are suspended from an upper end of the bottom portion. The bottom end curves inward in the radial direction and ends, and the outer circumferential surface part whose length along the circumferential direction is narrowed at the bottom end side and slopes downward from the center side of the bottom part toward the outside in the radial direction. A bottom groove portion is formed in the bottom portion and is indented inward of the container between the adjacent leg portions, and both circumferential edges of the outer circumferential surface portion meet side edge portions. The side surface is connected to the continuous side surface while smoothly curving toward the bottom groove, and the side surface edge has a cross section that is convex outward of the container and has a radius of curvature smaller than that of the outer peripheral surface. The length of the outer circumferential surface portion along the circumferential direction of the outer circumferential surface portion is such that, on the upper end side of the leg, both circumferential edges of the outer circumferential surface portion are While gradually narrowing in a symmetrical arc toward the center in the circumferential direction, the length along the circumferential direction at the lower end side of at least 1/2 of the height of the leg portion is The width is narrowed to 20 to 35 % of the length along the circumferential direction at the upper end of the section.

According to the present invention, a synthetic resin container having a bottom formed in a so-called petaloid shape has good shaping properties during blow molding, and the container is filled with a carbonated beverage and sealed, and the inside of the container is When the pressure becomes positive, stress cracks caused by the pressure applied to the inner surface of the bottom can be suppressed.

1 is a front view schematically showing a synthetic resin container according to an embodiment of the present invention. FIG. 1 is a rear view schematically showing a synthetic resin container according to an embodiment of the present invention. FIG. 1 is an enlarged bottom view schematically showing a synthetic resin container according to an embodiment of the present invention. FIG. 2 is an end view taken along the line AA in FIG. 1; FIG. 2 is an end view taken along line BB in FIG. 1; 2 is a CC end view of FIG. 1. FIG. FIG. 4 is an end view taken along line DD in FIG. 3; FIG. 4 is an end view taken along the line EE in FIG. 3; 4 is an FF end view of FIG. 3. FIG. FIG. 4 is an end view taken along line GG in FIG. 3; FIG. 4 is an end view taken along the line HH in FIG. 3; 4 is an II end view of FIG. 3. FIG. FIG. 7 is an explanatory diagram showing FIGS. 7 to 12 overlaid. 4 is an end view taken along the line JJ in FIG. 3. FIG. 4 is a KOJ end view of FIG. 3. FIG. 16 is an enlarged view of the main part of FIG. 15. FIG. 17 is an enlarged view of the main part of FIG. 16. FIG. FIG. 2 is an explanatory diagram showing a state in which strain is applied to the bottom surface of the legs when the inside of the synthetic resin container becomes positive pressure.

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

FIG. 1 is a front view schematically showing the synthetic resin container according to the present embodiment, FIG. 2 is a rear view thereof, and FIG. 3 is an enlarged view of the bottom surface of the synthetic resin container according to the present embodiment. It is an enlarged bottom view showing an outline.

The container 1 shown in these figures has a mouth 2, a shoulder 3, a body 4, and a bottom 5, and the body 4 is generally cylindrical and is generally referred to as a round bottle. It has a container shape.
Note that in FIGS. 1 and 2, a part of the body portion 4 is omitted.

Such a container 1 is made by molding a bottomed cylindrical preform using thermoplastic resin by injection molding, compression molding, etc., and molding this preform into a predetermined container shape by biaxial stretch blow molding, etc. Manufactured by

In manufacturing the container 1, any thermoplastic resin that can be blow molded can be used. Specifically, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, amorphous polyarylate, polylactic acid, polyethylene furanoate, or copolymers thereof, blended with these resins or other resins Preferably. In particular, ethylene terephthalate thermoplastic polyesters such as polyethylene terephthalate are preferably used. Further, polycarbonate, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene, etc. can also be used.

The spout 2 is a cylindrical portion that serves as a spout for pouring the contents, and a lid (not shown) is attached to the spout 2 to seal the inside of the container.
Further, the lower end of the mouth portion 2 is connected to a shoulder portion 3 that expands in diameter toward the body portion 4 in the shape of a truncated cone and connects the mouth portion 2 and the body portion 4 .

The body portion 4 is a portion that occupies most of the height of the container 1, and has an upper end connected to the shoulder portion 3 and a lower end connected to the bottom portion 5.

Here, the height direction refers to the direction perpendicular to the horizontal plane when the container 1 is erected on the horizontal plane with the mouth 2 facing upward. shall specify the vertical and horizontal directions as well as the vertical and horizontal directions.
In addition, although the central axis is indicated by the symbol C in Fig. 1, unless otherwise specified, a cross section cut along a plane including the central axis C is a longitudinal section, and a cross section cut along a plane perpendicular to the central axis C is a transverse section. It is called a surface.

In this embodiment, the container 1 is configured to be suitably used as a pressure-resistant bottle containing a carbonated beverage. Therefore, the plurality of (five in the illustrated example) legs 51 are arranged rotationally symmetrically around the central axis C and at equal intervals so that the self-sustaining stability is not impaired even if the inside of the container becomes positive pressure. It has a so-called petaloid-shaped bottom part 5 arranged radially.

In the bottom part 5 having such a shape, the central part thereof is a bottom plate part 50 which is recessed in a dome shape inward of the container, and legs 51 are arranged around this bottom plate part 50. Between the adjacent leg parts 51, a bottom groove part 56 is formed at the periphery of the bottom plate part 50 and is recessed inward of the container so that the vertical cross section at the deepest part has an arcuate shape convex to the outside of the container. It is formed to extend radially from. In other words, the legs 51 disposed around the bottom plate part 50 are rotated along the circumferential direction from a substantially hemispherical virtual plane consisting of a plane of rotation around the central axis C with the deepest part of the bottom groove part 56 as a generatrix. It is formed so that it partially bulges out at predetermined intervals.

The leg portion 51 hangs down from the upper end of the bottom portion 5 that is connected to the body portion 4 (in the illustrated example, the leg portion 51 hangs down with a slight inclination toward the inside of the container), and the lower end side curves inward in the radial direction while terminating. It has an outer circumferential surface portion 52 whose length (width) along the direction is narrowed at the lower end side. Both circumferential edges of the outer circumferential surface portion 52 are connected to a continuous side surface portion 55 while smoothly curving toward the bottom groove portion 56 .

The width of the outer circumferential surface portion 52 is gradually narrowed on the upper end side of the leg portion 51 so that both circumferential edges of the outer circumferential surface portion 52 draw an arc symmetrically toward the circumferential center of the outer circumferential surface portion 52. The width W at the lower end side of at least 1/2 of the height H of the leg portion 51 is narrowed to 15 to 50%, more preferably 20 to 35%, of the width W ₀ at the upper end of the leg portion 51. It is being

By doing so, the leg portion 51 can be formed so that the side portion 55 connected to both circumferential edges of the outer circumferential surface portion 52 curves smoothly with a larger radius of curvature and continues to the bottom groove portion 56. become. By forming the leg portions 51 in this way, in addition to improving the shapeability during blow molding, the container 1 is filled with carbonated beverage and sealed, and the inside of the container is kept under positive pressure. It is also possible to suppress stress cracks caused by the pressure applied to the inner surface of the bottom portion 5 when

In forming the leg portion 51 so that the side surface portion 55 curves more smoothly and continues to the bottom groove portion 56, an edge portion (hereinafter, “side surface edge portion”) that is connected to the outer circumferential surface portion 52 of the side surface portion 55 is used. 55a is preferably formed in a cross section in the shape of an arc convex to the outside of the container and having a radius of curvature smaller than that of the outer circumferential surface portion 52 (see FIGS. 4 to 6). It is preferable that the radius of curvature of the side edge portion 55a is 10 to 50% of the radius of curvature of the outer circumferential surface portion 52 in the same cross section at least in a portion on the lower end side of 1/2 of the height H of the leg portion 51. preferable.

Here, the radius of curvature in the cross section of the outer peripheral surface portion 52 is approximately equal to the radius of curvature in the cross section of the upper end of the bottom portion 5 (that is, the lower end of the body portion 4), and the portion where the curvature changes in the cross section is the outer peripheral surface portion 52. This is the boundary with the side surface portion 55.
In addition, a portion where the upper end edge of the bottom groove portion 56 is extended in the circumferential direction and connected is defined as a boundary between the body portion 4 and the bottom portion 5.

4 is an AA end view of FIG. 1, FIG. 5 is a BB end view of FIG. 1, and FIG. 6 is a CC end view of FIG. In these figures, the end face of the bottom part 5 in the cross section is shown without the wall thickness, and the boundary between the outer circumferential surface part 52 and the side part 55 is shown by an auxiliary line (dashed line) extending from the center.

Further, the leg portion 51 has a leg bottom surface portion 53 that slopes downward from the center side of the bottom portion 5 toward the outside in the radial direction.

The leg bottom surface part 53 is perpendicular to a plane including the central axis C and a center line that passes through the center of the bottom part 5 and equally divides the leg bottom surface part 53 in the circumferential direction, at least in a region on the center side of the bottom part 5. It is preferable that a cross section cut along a plane parallel to C is formed in an arc shape convex outward from the container. It is preferable that the cross section is formed in a straight line in other parts, and the leg bottom surface part 53 is preferably formed so that there is no part that is convex inward of the container in the cross section (FIGS. 7 to 7). (See Figure 13).

7 is a DD end view of FIG. 3, FIG. 8 is an EE end view of FIG. 3, FIG. 9 is an FF end view of FIG. 3, and FIG. 10 is a G-- 11 is an HH end view of FIG. 3, FIG. 12 is an II end view of FIG. 3, and FIG. 13 is an explanatory diagram showing FIGS. 7 to 12 superimposed. In these figures, the leg bottom section is cut along a plane that is perpendicular to a plane that includes the center line that passes through the center of the bottom section 5 and equally divides the leg bottom section 53 in the circumferential direction and the center axis C, and that is parallel to the center axis C. The end face of 53 is shown with the wall thickness omitted.

By doing this, when the container 1 is filled with a carbonated beverage and sealed, and the inside of the container becomes positive pressure, stress concentration on the center side of the leg bottom portion 53 is avoided, and and stress cracks in the vicinity thereof can be more effectively suppressed.

Further, as shown in FIGS. 14 to 17, the leg bottom surface portion 53 has a straight portion 53a having a linear vertical cross section and connected to the outer peripheral surface portion 52, and a straight portion 53a having a vertical cross section convex to the outside of the container. It has an outwardly convex arcuate portion 53b which is connected to the straight portion 53a.
An inclined surface portion 53c is provided between the outwardly convex arcuate portion 53b and the bottom plate portion 50, and the inclined surface portion 53c has a vertical cross section formed in an arc shape convex inward of the container at least on the side of the outwardly convex arcuate portion 53b. ing.
14 is an end view taken along JJ in FIG. 3, FIG. 15 is an end view taken along K-OJ in FIG. Enlarged view, FIG. 17 is an enlarged view of the main part showing the part surrounded by the chain line in FIG. 15 on an enlarged scale. In these figures, the wall thickness appearing on the end face is omitted.
In FIGS. 16 and 17, the intersection point of the straight portion 53a and the lower end edge 52a of the outer circumferential surface portion 52 (hereinafter referred to as "outer circumferential surface edge portion") which terminates while curving inward to the inside of the container is defined as a. b is the intersection between the portion 53a and the outer convex arcuate portion 53b, c is the intersection between the outer convex arcuate portion 53b and the inclined surface portion 53c, and the arc formed by the outer peripheral surface edge portion 52a is in contact with an imaginary plane that intersects perpendicularly to the axial direction. The contact point is shown with the reference numeral d.

The outer circumferential surface edge portion 52a extends from the radially outer side to the radially inner side beyond a contact point d where the arc formed by the outer circumferential surface edge portion 52a touches an imaginary plane perpendicular to the axial direction, and forms a straight portion 53a. Concatenated.

Further, in this embodiment, the connecting portion 54 between the straight portion 53a and the outer convex arc portion 53b is formed in a circular arc shape that is convex inward in the radial direction (see FIG. 3).

In such a container 1, when the container is filled with contents, sealed, and erected, the arc formed by the outer circumferential surface end edge 52a extends from the vicinity of the contact point d, which is in contact with a virtual plane perpendicular to the axial direction, to the outer circumferential surface. The area up to the vicinity of the intersection a between the edge portion 52a and the straight portion 53a becomes the grounding portion of the leg portion 51 that contacts the ground surface on which the container is installed.

The container 1 of this embodiment has such a leg bottom surface 53, so that when the contents are filled and sealed and the inside of the container becomes positive pressure, the radially outer portion of the leg bottom surface 53 and the leg portion Deformation and stress cracks in and around the ground contact portion of 51 can be more effectively suppressed.

For example, when the inside of the container 1 becomes positive pressure, the side surface portions 55 of the leg portions 51 are deformed so as to take advantage of the outward expansion of the bottom groove portions 56 and to be lifted in a direction where the inclination relative to the leg bottom surface portions 53 becomes gentler. Then, the leg bottom part 53 receives pressure that causes the leg bottom part 53 itself to bulge outward from the container, and also receives pressure that pushes both ends inward as the side part 55 deforms, so that the leg bottom part 53 becomes wrinkled. Stress is generated (see Figure 18). The radially outer portion of the leg bottom 53, which is located on the outer side of the container bottom 5 and has a relatively thin wall, and the ground contact portion connected to the leg bottom 53 are free from the influence of such stress. Easy to accept.
On the other hand, a straight part 53a whose vertical cross section is formed in a straight line and is connected to the outer circumferential surface part 52, and an outwardly convex arc-shaped part 53b whose vertical cross section is formed in an arc shape that is convex inward of the container and which is connected to the straight part 53a. By making the connecting part between the straight part 53a and the outwardly convex arc-shaped part 53b into the leg bottom part 53 formed in a convex arc shape radially inward, the radially outer part of the leg bottom part 53 and , stress acting on the ground contact portion connected to the leg bottom portion 53 can be dispersed.
Thereby, stress cracks and deformation in the radially outer portion of the leg bottom portion 53, the ground contact portion, and the vicinity thereof can be effectively suppressed.

In addition, when the inside of the container 1 becomes positive pressure, as the bottom part 5 is deformed so as to be pushed down, the grounding part moves closer to the center side of the bottom part 5 and is slightly included in the straight part 53a. Although it may deform in this way, if the structure is such that a part of the straight part 53a exists between the ground contact part and the outer convex arcuate part 53b, wrinkles will form in the ground contact part. The influence of the stress that acts like this can be preferably suppressed by the straight portion 53a.

The length of the longest part of the straight part 53a is L, with respect to the distance from the intersection a with the outer circumferential surface edge part 52a to the intersection b with the outer convex arcuate part 53b in a virtual plane 60 perpendicular to the central axis. _1. When the length of the shortest part is L ₂ , for example, the ratio of the height H ₀ to the trunk diameter D (H ₀ /D) is 2.5 to 4.0, preferably 2.8 to 3.8 In the case of the container 1, if L ₁ is formed to be 1.5 to 4 mm and L ₂ is 0 to 4 mm, stress concentration and deformation on the radially outer portion of the leg bottom portion 53 and the ground contact portion can be prevented. Preferable to avoid.
It should be noted that the specific numerical values regarding the shape of the container 1 mentioned hereafter refer to the same conditions regarding the ratio (H ₀ /D) of the height H ₀ and the body diameter D of the container 1 described above.

In addition, the straight portion 53a is designed to prevent stress from being concentrated due to the pressure applied to the inner surface of the bottom portion 5, and to prevent the periphery of the ground contact portion from deforming as if being pushed down. is preferably inclined upward toward the inside in the radial direction at an angle of inclination α of 1 to 6 degrees with respect to the virtual plane 60 perpendicular to the central axis.

In addition, if the outwardly convex arcuate portion 53b is formed in an outwardly convex arc shape of the container so that the radius of curvature of the longitudinal section is 3 to 20 mm, it is possible to avoid creating a stress concentration area and to This is preferable in order to prevent the periphery of the ground contact portion from being pushed down and deformed due to the pressure applied to the inner surface side of 5.

In addition, if the inclined surface portion 53c is formed in an arcuate shape convex inward of the container so that the radius of curvature of the longitudinal section is 15 mm or more at least on the side connected to the outwardly convex arcuate portion 53b, stress will be concentrated at a portion of the inclined surface portion 53c. This is more preferable in that it prevents the periphery of the ground contact portion from being pushed down and deformed due to the pressure applied to the inner surface of the bottom portion 5. Further, it is preferable that the inclined surface portion 53c is formed so as to be smoothly continuous with the outer convex arc portion 53b such that the tangents touching each coincide with each other at the intersection c with the outer convex arc portion 53b.
Note that the longitudinal cross section of the inclined surface portion 53c may be approximately straight as long as it has an arcuate shape convex inward of the container at least on the side connected to the outwardly convex arcuate portion 53b.

Further, when the radius of curvature of the longitudinal section of the outer circumferential surface edge portion 52a is 0.5 to 12 mm, more preferably 2 to 6 mm, the inner surface of the bottom portion 5 can be This is preferable in order to prevent the periphery of the ground contact portion from being pushed down and deformed due to the pressure applied to the ground contact portion.
As the radius of curvature in the longitudinal section of the outer peripheral surface edge portion 52a increases, the connecting portion 54 is formed closer to the center of the bottom portion 5. Therefore, it is not preferable from the viewpoint of self-supporting stability that the radius of curvature in the longitudinal section of the outer peripheral surface edge portion 52a is too large. On the other hand, as the radius of curvature in the longitudinal section of each of the outer circumferential surface edge portion 52a and the outer convex arcuate portion 53b becomes smaller, shaping defects tend to occur more easily. For this reason, if the radius of curvature in the longitudinal section of each of the outer peripheral surface edge portion 52a and the outer convex arcuate portion 53b is too small, there is a risk that the compressive strength will be poor due to insufficient stretching.

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

For example, in the embodiment described above, an example was shown in which five legs 51 were arranged on the bottom 5, but the number of legs 51 arranged on the bottom 5 is not limited to this.
Further, in the embodiment described above, an example is shown in which the shoulder portion 3 is provided with the shoulder portion 3 whose diameter increases from the lower end of the mouth portion 2 toward the body portion 4 in a truncated conical shape, but the present invention is not limited to this. The shoulder portion 3 that connects the mouth portion 2 and the body portion 4 may be formed, for example, in a so-called crane neck shape. Similarly, the form of the body portion 4 is not limited to the illustrated example.

In short, in the synthetic resin container according to the present invention, the leg portions 51 disposed on the bottom portion 5 hang down from the upper end of the bottom portion 5, the lower end side curves inward in the radial direction and ends, and the leg portions 51 extend along the circumferential direction. It has an outer peripheral surface portion 52 whose length is narrowed at the lower end side, and a leg bottom surface portion 53 that slopes downward from the center side of the bottom portion 5 toward the outside in the radial direction, and the length of the outer peripheral surface portion 52 along the circumferential direction. At the upper end side of the leg portion 51, both circumferential edges of the outer circumferential surface portion 52 gradually narrow in a symmetrical arc toward the circumferential center of the outer circumferential surface portion 52. The length along the circumferential direction at the lower end side of 1/2 of the height is narrowed to 10 to 50% of the length along the circumferential direction at the upper end of the leg portion 51. As long as it is formed, the configuration of other details is not limited to the above-described embodiment and can be changed as appropriate.
Furthermore, the detailed configurations described in the embodiments described above can be selected and combined as appropriate.

1 Container 5 Bottom 51 Leg 52 Outer circumference 52a Outer edge 53 Leg bottom 53a Straight portion 53b External convex arc portion 53c Inclined surface 54 Connecting portion 55 Side portion 55a Side edge

Claims (4)

Equipped with a bottom part in which a plurality of legs are rotationally symmetrical around a central axis and arranged radially at equal intervals,
The leg portion is
an outer circumferential surface portion that hangs down from the upper end of the bottom portion, has a lower end curved inward in the radial direction, and has a circumferential length narrowed at the lower end;
and a leg bottom surface portion that slopes downward from the center side of the bottom portion toward the outside in the radial direction,
A bottom groove portion is formed in the bottom portion and is indented inward of the container between the adjacent leg portions,
Both circumferential edges of the outer circumferential surface portion are connected to a continuous side surface portion while smoothly curving toward the bottom groove portion via a side surface edge portion,
The side edge portion has a cross section formed in an arc shape convex to the outside of the container and has a radius of curvature smaller than that of the outer circumferential surface portion;
The length along the circumferential direction of the outer circumferential surface portion is such that, on the upper end side of the leg, both circumferential edges of the outer circumferential surface portion draw an arc symmetrically toward the circumferential center of the outer circumferential surface portion. While gradually narrowing, the length along the circumferential direction at the lower end side of at least 1/2 of the height of the leg is 20 to 35 times the length along the circumferential direction at the upper end of the leg. A synthetic resin container characterized by being narrowed so that the The cross section of the side surface edge has a radius of curvature equal to the radius of curvature of the outer circumferential surface in the same cross section, at least at a portion closer to the lower end than 1/2 of the height of the leg. The synthetic resin container according to claim 1, which has a radius of 10 to 50%. The leg bottom part is perpendicular to a plane including a center line passing through the center of the bottom part and equally dividing the leg bottom part in the circumferential direction, and a center axis, at least in a region on the center side of the bottom part. The synthetic resin container according to claim 1 or 2, wherein a cross section cut along a parallel plane is formed in an arc shape convex to the outside of the container. The leg bottom portion includes a straight portion whose vertical section is formed in a straight line and is connected to the outer circumferential surface portion, and an outwardly convex arc-shaped portion whose vertical section is formed in an arc shape that is convex inward of the container and is connected to the straight portion. The synthetic resin container according to any one of claims 1 to 3, wherein the connecting portion between the straight portion and the outward convex arc portion is formed in a circular arc shape convex inward in the radial direction.

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