JP7756482B2 - Synthetic resin containers - Google Patents

Description

The present invention relates to a synthetic resin container equipped with a vacuum absorption structure at the bottom that absorbs pressure changes inside the container after it has been filled and sealed.

Conventionally, synthetic resin containers have been used in a wide range of applications, including containers for various beverages, seasonings, and other contents, by forming a bottomed, cylindrical preform from a thermoplastic resin such as polyethylene terephthalate, and then molding this preform into a bottle using methods such as biaxial stretch blow molding.

Furthermore, when filling this type of synthetic resin container with contents, a so-called hot pack method is known in which the contents are filled and sealed while still hot after being heat sterilized.
After the contents are filled and sealed using a hot pack, the container is cooled to room temperature and then placed in a reduced pressure state inside. Therefore, containers to be hot packed generally have a plurality of vacuum absorption panels arranged circumferentially around the body of the container. These panels deform inward as the container cools, reducing the volume of the container and absorbing the loss of internal pressure (see Patent Document 1).
In recent years, a bag with a vacuum absorption structure at the bottom has also been proposed (see Patent Document 2).

Japanese Patent Application Laid-Open No. 2003-063516 JP 2010-126184 Public Relations

Incidentally, in the container having a vacuum absorption structure at the bottom proposed in Patent Document 2, a depression (11) is formed on the bottom surface of the bottom (5) by depressing the inner peripheral end of the ground contact portion (16) toward the inside of the container, and further a dome-shaped depression (12) is formed in the center of the depression (11), which is deformed toward the inside of the container to perform the vacuum absorption function.
However, when the container bottom is formed in this manner, the bottom (5) tends to stick to the recessed portion (12) of the bottom mold used to form the bottom during the demolding process after blow molding, and some ingenuity is required to ensure good demolding from the bottom mold.
The reference numerals in parentheses refer to those in Patent Document 2.

The inventors therefore believed that the vacuum absorption structure proposed in Patent Document 2, particularly the dome-shaped recess (12) formed in the center, was preventing good mold release. They conducted extensive research to create a vacuum absorption structure in the bottom that would improve mold release without compromising vacuum absorption performance by making the center flat. As a result, they discovered that insufficient stretching during blow molding near the center of the bottom resulted in reduced heat resistance.

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a synthetic resin container that has a vacuum absorption structure at the bottom that absorbs pressure changes inside the container after it is filled and sealed, and that allows for greater stretching near the center of the bottom during blow molding.

The synthetic resin container of the present invention is a synthetic resin container having a bottom portion with a reduced pressure absorption structure that absorbs pressure changes inside the container after the contents have been filled and sealed, and the bottom portion has legs that include a ground contact portion and extend circumferentially, and a movable bottom plate portion whose outer edge side is connected to the upper end of the inner surface of the legs that rise from the inner peripheral edge of the ground contact portion, and the movable bottom plate portion includes a curved surface that is arranged around the central portion and curves convexly outward from the container in the radial direction , and the curved surface is provided with a plurality of groove portions that are recessed in the radial direction so that the curved surface portion partially protrudes toward the inside of the container, and the groove portions are recessed so that the groove depth gradually increases starting from the outer peripheral edge side of the movable bottom plate portion , and then the bottom surface of the groove portion curves parallel to the curved surface toward the center at a predetermined depth , and ends at the peripheral edge side of the central portion, at the predetermined groove depth.

This invention makes it possible to achieve greater stretching near the center of the bottom of a synthetic resin container equipped with a vacuum absorption structure at the bottom that absorbs pressure changes inside the container after the contents are filled and sealed, during blow molding.

1 is a front view showing an outline of a synthetic resin container according to an embodiment of the present invention. 1 is a side view showing an outline of a synthetic resin container according to an embodiment of the present invention. 1 is a bottom view showing an outline of a synthetic resin container according to an embodiment of the present invention. 1 is a perspective view showing an outline of 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. 1 is an enlarged end view of a main part showing an outline of a synthetic resin container according to an embodiment of the present invention. FIG. 2 is a cross-sectional perspective view showing the cross section BB in FIG. 1. 1 is an enlarged end view of a main part showing an outline of a synthetic resin container according to an embodiment of the present invention. 1 is an enlarged end view of a main part showing an outline of a synthetic resin container according to an embodiment of the present invention.

A preferred embodiment of the present invention will now be described with reference to the drawings.

FIG. 1 is a front view showing an outline of a synthetic resin container according to this embodiment, FIG. 2 is a side view of the same, FIG. 3 is a bottom view of the same, and FIG. 4 is a perspective view showing the bottom 5 side.
5 is an end view taken along line A-A in FIG. 1, FIG. 6 is an enlarged end view showing the main part enclosed by the chain line in FIG. 5, and FIG. 7 is a perspective cross-sectional view taken along line B-B in FIG. 1.
5, 6 and 7, the wall thickness of the container 1 that appears on the cross section is omitted.

The container 1 shown in these figures has a mouth 2, a shoulder 3, a body 4, and a bottom 5, and has a container shape generally referred to as a round bottle, with the body 4 formed in a roughly cylindrical shape.
The container 1 is also provided with a pressure-reducing structure at the bottom 5, which absorbs the pressure loss caused by the container being cooled to room temperature after being filled with the contents and sealed using a so-called hot pack, as will be described later.

Such a container 1 is manufactured by molding a bottomed cylindrical preform using a thermoplastic resin by injection molding, compression molding, or the like, and then molding this preform into the desired container shape by biaxial stretch blow molding, or the like.

When manufacturing container 1, any resin that can be blow-molded can be used as the thermoplastic resin. Specifically, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, amorphous polyarylate, polylactic acid, polyethylene furanoate, or copolymers of these, as well as blends of these resins with other resins, are suitable. Ethylene terephthalate-based thermoplastic polyesters such as polyethylene terephthalate are particularly suitable. Polycarbonate, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene, etc. can also be used.

The mouth 2 is a cylindrical portion that serves as a spout for pouring the contents. A fitting 20 that protrudes annularly along the circumferential direction is provided on the side of the open end of the mouth 2 so that a lid (not shown) can be attached by tapping, but the means for attaching the lid is not limited to this.
The lower end of the mouth portion 2 is connected to a shoulder portion 3 that widens in diameter in a truncated cone shape toward the body portion 4 and connects the mouth portion 2 and the body portion 4.

The body 4 occupies most of the height of the container 1 , and its upper end is connected to the shoulder 3 and its lower end is connected to the bottom 5 .
Here, the height direction refers to the direction perpendicular to the horizontal plane when the container 1 is placed upright on the horizontal plane with the mouth 2 facing upward, and defines the up-down, left-right and length-width directions of the container 1 in this state (the state shown in Figure 1).

Six vacuum absorption panels 40 are arranged at predetermined intervals around the circumferential direction of the body 4 to supplement the vacuum absorption performance of the vacuum absorption structure of the bottom 5. The specific shape of the vacuum absorption panels 40 is not particularly limited, as long as they exhibit the desired vacuum absorption performance in accordance with the vacuum absorption performance of the vacuum absorption structure of the bottom 5.

In this embodiment, an example is shown in which a vacuum absorption panel 40 is provided in the body 4 as an auxiliary measure when the vacuum absorption performance of the vacuum absorption structure provided in the bottom 5 alone is insufficient; the vacuum absorption panel 40 provided in the body 4 can also be omitted if necessary.

The body 4 also has two circumferential grooves 41, 42, and 43 at its upper end and one at its lower end, each extending annularly along the circumferential direction. These circumferential grooves 41, 42, and 43 are provided primarily to increase the load-bearing strength against loads from the lateral direction (direction perpendicular to the height direction), and can be omitted if necessary.

The bottom 5 includes a grounding portion 51 that comes into contact with the horizontal surface when the container 1 is placed upright on the horizontal surface, and has legs 50 that extend annularly along the circumferential direction to enable the container 1 to stand on its own. The width (grounding width) and outer diameter (grounding diameter) of the grounding portion 51 can be designed appropriately so that the container 1 can stand on its own stably, and the legs 50 are connected to the lower end of the body 4 via outer surfaces 52 that rise from the outer peripheral edge of the grounding portion 51.
In the example shown in the figure, the outer surface 52 of the leg 50 is formed so as to rise from the outer peripheral edge of the grounding portion 51 while curving convexly toward the outside of the container, but the outer surface 52 of the leg 50 can be designed appropriately depending on the grounding diameter of the grounding portion 51, etc.

The bottom 5 has a movable bottom plate portion 55 with a flat, disk-shaped central portion 56 and curved surfaces 57 that are curved radially around the periphery of the central portion 56 and convex outward from the container. The outer peripheral edge of the movable bottom plate portion 55 is connected to the upper ends of the inner surfaces 53 of the legs 50 that rise from the inner peripheral edges of the ground contact portion 51, forming a raised bottom.
Although not shown, a rib-like shape or the like may be provided on the outer peripheral edge of the movable bottom plate portion 55 as required.

In this way, as the pressure inside the container decreases after the contents have been filled and sealed with a hot pack, the movable bottom plate portion 55 can move upward while bending as a whole, as shown by the two-dot chain line in Figure 8, and the bottom portion 5 is provided with a pressure reduction absorption structure that absorbs the decrease in pressure inside the container as the movable bottom plate portion 55 moves.
8 is an enlarged end view of the essential part showing the bottom portion 5 side of the end view shown in FIG. 5, and the upwardly moved movable bottom plate portion 55 is indicated by a two-dot chain line.

Furthermore, because the movable bottom plate portion 55 is configured to be movable, when the contents are filled, the entire movable bottom plate portion 55 is deflected and pushed down as shown by the two-dot chain line in Figure 9 depending on the filling pressure and the weight of the contents. If the movable bottom plate portion 55 is pushed down beyond the ground contact portion 51, the container 1 may lose its independence and tip over. For this reason, the inner surface 53 of the leg portion 50 can be appropriately designed so that the height _h50 from the ground contact portion 51 to the upper end where the outer peripheral edge of the movable bottom plate portion 55 is connected (defined as the height of the leg portion 50) is sufficient to accommodate the movement of the movable bottom plate portion 55.
9 is an enlarged end view of the essential part showing the bottom portion 5 side of the end view shown in FIG. 5, and the depressed movable bottom plate portion 55 is shown by a two-dot chain line.

Furthermore, the larger the capacity of the container 1, the heavier the contents become, and the greater the downward pressure of the movable bottom plate portion _55. Therefore, the height h50 of the legs 50 must be appropriately designed according to the capacity of the container 1. However, if the height h50 of the legs ₅₀ is relatively low, for example, if the container 1 filled and sealed with contents is accidentally dropped, and the pressure inside the container increases momentarily due to the impact of the drop, the contents pressurized and forced into the legs 50 will push the inner surface 53 of the legs 50 from the inside, causing it to deform and curl up, which in turn tends to cause the movable bottom plate portion 55 to bulge beyond the ground surface 51. Once such deformation occurs, it is difficult for the container 1 to restore its original shape, making it unable to stand on its own, significantly reducing its commercial value.

In this embodiment, to avoid such a problem, the inner surface 53 of the leg 50 is formed by a plurality of surfaces (two surfaces in the illustrated example) 53a, 53b that are connected vertically and have different inclinations, and an annular ridge portion 53c is formed at the junction of the surfaces 53a, 53b in parallel with the ground contact portion 51. Such ridge portion 53c makes it difficult for the inner surface 53 of the leg 50 to be pushed apart from the inside, resisting the force pushing against the inner surface 53 of the leg 50 from the inside.
Therefore, according to this embodiment, it is possible to prevent the bottom portion 5 from being deformed in a way that would make it unable to stand on its own due to an impact such as being dropped as described above.
The ridge line portion 53c does not necessarily have to be formed parallel to the ground contact portion 51, but may be provided so that the height from the ground contact portion 51 changes periodically along the circumferential direction, for example.

When the inner surface 53 of the leg portion 50 is formed by a plurality of surfaces connected vertically with different inclinations, if the number of surfaces increases, the strength against the increase in internal pressure when dropped or hot packed is improved, but the tendency for the original shape to be restored when deformation occurs increases. For this reason, the number of surfaces forming the inner surface 53 of the leg portion 50 can be appropriately designed according to the height h50 of the leg portion ₅₀ while taking into consideration the balance between resistance to deformation and restorability, but the number of surfaces forming the inner surface 53 of the leg portion 50 is preferably two, as shown in the figure.

The surfaces that form the inner surface 53 of the leg 50 may be formed so that their longitudinal cross sections are linear, but in the example shown, the two surfaces 53a, 53b that form the inner surface 53 of the leg 50 are gently curved with a relatively large radius of curvature (Ra = 12 mm, Rb = 24 mm in the example shown) and connected vertically so that they are convex toward the inside of the inner surface 53. This makes it more difficult for the inner surface 53 of the leg 50 to be pushed apart from the inside.

Furthermore, each surface forming the inner surface 53 of the leg portion 50 preferably forms an angle of 45 to 88 degrees with the horizontal plane in a vertical cross section when the container 1 is held upright on a horizontal surface. If the surface forming the inner surface 53 of the leg portion 50 is gently curved, it is preferable that the angle formed by the horizontal plane and a line connecting the start point and end point of that surface in a vertical cross section be within the above range. If the angle is below this range, deformation due to impact, such as being dropped, tends to occur easily. On the other hand, if the angle exceeds this range, poor demolding of the bottom mold tends to occur during the demolding process after blow molding.

As mentioned above, the movable bottom plate portion 55 moves downward due to the weight of the contents. If the movable bottom plate portion 55 is pressed down by the weight of the contents when the container 1 is sealed, the range over which the movable bottom plate portion 55 can move upward when absorbing reduced pressure becomes larger. As a result, the decrease in pressure inside the container can be absorbed more effectively, improving reduced pressure absorption performance.

Furthermore, in order to suppress deformation due to impacts such as dropping while ensuring the desired vacuum absorption performance, it is preferable that the center portion 56 of the movable bottom plate portion 55 be as high as possible as the outer peripheral edge side connected to the upper end of the inner surface 53 of the leg portion 50, and the curved surface 57 of the movable bottom plate portion 55 is preferably curved along the radial direction so that the height _h57 from the outer peripheral edge of the movable bottom plate portion 55 to the lowest point of the curved surface ₅₇ is 1.0 to 4.0 mm. If the height h57 is below the above range, the volume that can absorb vacuum decreases, and the desired vacuum absorption performance tends to be lessened. On the other hand, if the height _h57 exceeds the above range, the movable bottom plate portion 55 tends to bulge beyond the ground contact portion 51 due to impacts such as dropping, and when filling the container with contents, the movable bottom plate portion 55 tends to be pushed down and tip over beyond the ground contact portion 51.

Furthermore, when the movable bottom plate portion 55 moves up and down while flexing overall, it is stretched radially and deformed so that its length along the circumferential direction is shortened. To absorb this change in circumferential length, the curved surface 57 arranged around the central portion 56 of the movable bottom plate portion 55 is provided with a plurality of recessed grooves 58 that are recessed so that the curved surface 57 is partially raised along the radial direction. By providing such recessed grooves 58 on the curved surface 57 of the movable bottom plate portion 55, the shape restoring ability of the movable bottom plate portion 55 can also be improved.

When providing grooves 58 on the curved surface 57 of the movable bottom plate 55, it is possible to provide the grooves 58 at equal angular intervals around the circumference to ensure uniform deformation of the movable bottom plate 55. However, if the intervals between adjacent grooves 58 are too close, it would be impossible to provide markings such as a model number or lot number on the bottom surface. Taking this into consideration, in this embodiment, an even number of reference grooves 58 (58a) are provided at equal angular intervals (45° in the illustrated example, preferably 22.5 to 90.0°) to ensure uniform deformation of the movable bottom plate 55 while also providing sufficient space for markings. A groove 58 (58b) is added every other time around the circumference between adjacent reference grooves 58 (58a), providing a total of multiple grooves 58 (12 in the illustrated example, preferably 6 to 24) (see Figure 3).

The grooves 58 are recessed so that their depth gradually increases from the outer peripheral edge of the movable bottom plate 55 at a starting point SE, then gradually increases toward the center at a predetermined depth until they reach the peripheral edge of the central portion 56 at a terminal end TE, which has the predetermined depth. By providing the grooves 58 so that the terminal end TE, located on the peripheral edge of the central portion 56, has the predetermined depth and protrudes inward, the container 1 can be more stretched near the peripheral edge of the central portion 56 of the movable bottom plate 55, where the wall thickness tends to be thick. This increases the crystallinity due to stretch orientation and improves heat resistance. As a result, sagging of the central portion 56 during hot packing can be prevented.
As described above, according to this embodiment, it is possible to further stretch the vicinity of the center of the bottom portion during blow molding.

The groove depth at the end TE of the recessed groove portion 58 is preferably 0.5 to 2.0 mm. If it is less than this range, the stretching will be insufficient, and the improvement in heat resistance will likely be lost. On the other hand, if it exceeds this range, the bottom mold will likely not be properly released during the demolding process after blow molding, and there will likely be poor shaping between the recessed groove portions 58.

In addition, by providing groove portion 58 so that its end TE, located on the peripheral side of central portion 56, protrudes inward into the container, and by further extending the area near the peripheral edge of central portion 56, movable bottom plate portion 55 is more likely to move upward in response to a decrease in pressure within the container. Furthermore, if the bottom surface of groove portion 58 were curved so that it convexly protrudes inward into the container, opposite to curved surface 57, there is a concern that this may hinder the movement of movable bottom plate portion 55. However, by having end TE of groove portion 58 protrude inward into the container, the range over which the bottom surface of groove portion 58 is curved approximately parallel to curved surface 57 can be widened, thereby also improving responsiveness to a decrease in pressure within the container.

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 are possible within the scope of the present invention.

In other words, the present invention relates to a container in which the bottom portion 5 includes a ground contact portion 51, leg portions 50 extending circumferentially, and a movable bottom plate portion 55 whose outer periphery is connected to the upper end of the inner surface 53 of the leg portion 50 rising from the inner periphery of the ground contact portion 51. The movable bottom plate portion 55 includes a curved surface 57 arranged around the central portion 56 and curved radially outwardly of the container, and the curved surface 57 is provided with a plurality of grooves 58 recessed along the radial direction. The grooves 58 have a starting end SE on the outer periphery of the movable bottom plate portion 55 and a terminal end TE reaching the periphery of the central portion 56, and are recessed so as to have a predetermined groove depth. Other detailed configurations can be modified as appropriate without being limited to the above-described embodiment. Furthermore, the detailed configurations described in the above-described embodiment can be combined as appropriate.

REFERENCE SIGNS LIST 1 container 5 bottom 50 legs 51 ground contact portion 55 movable bottom plate portion 56 center portion 57 curved surface 58 groove portion SE starting end TE ending end

Claims (2)

A synthetic resin container having a pressure reduction absorbing structure at the bottom that absorbs pressure changes inside the container after the contents are filled and sealed,
The bottom portion is
a leg portion including a ground contact portion and extending in a circumferential direction;
a movable bottom plate portion whose outer periphery is connected to the upper end of the inner surface of the leg portion rising from the inner periphery of the ground contact portion,
the movable bottom plate portion includes a curved surface disposed around the central portion and curved radially outwardly of the container,
The curved surface is provided with a plurality of recessed grooves that are recessed so that the curved surface portion is partially raised along the radial direction and protrudes toward the inside of the container , and
A synthetic resin container characterized in that the groove portion is recessed so that the groove depth gradually increases from the outer peripheral edge side of the movable bottom plate portion , and then the groove bottom surface of the groove portion curves parallel to the curved surface toward the center at a predetermined depth, and the end reaching the peripheral edge side of the central portion has the predetermined groove depth. The synthetic resin container according to claim 1, wherein the curved surface is curved so that the height of the lowest point relative to the outer periphery of the movable bottom plate portion is 1.0 to 4.0 mm.