Synthetic resin containers

Abstract

To provide a synthetic resin container including a vacuum absorption structure absorbing pressure change in the container after charging and sealing a content at the bottom in which further extension of the area in the vicinity of the bottom center is possible at the time of blow molding.SOLUTION: A container 1 including a vacuum absorption structure absorbing pressure change in the container after charging and sealing a content at the bottom 5 is given in which: a bottom 5 includes a leg part 50 having a ground part 51 and extending in a circumferential direction, and a movable bottom plate part 55 an outer peripheral edge of which is connected with a top edge of an inside surface 53 of the leg part 50 rising up from an inner peripheral edge of the ground part 51; the movable bottom plate part 55 includes a curved surface 57 arranged around a center part 56 and projected to outside of the container in a radial direction; and the curved surface 57 has a plurality of recessed groove parts 58 in which a starting end SE of the recessed groove part 58 is at an outer peripheral edge side of the movable bottom plate part 55 in the radial direction, and a terminating end TE reaching the peripheral edge side of the central part 56 protrudes to inside of the container at the prescribed groove depth.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a synthetic resin container having a pressure reduction absorbing structure at the bottom that absorbs pressure changes inside the container after it has been filled with contents and sealed. [Background technology]

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

[0003] 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 used for hot packing 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, there have also been proposals for bags that have a vacuum absorption structure at the bottom (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-063516 [Patent Document 2] JP2010-126184 Public Relations Summary of the Invention [Problem to be solved by the invention]

[0005] In the container having a vacuum absorption structure at the bottom proposed in Patent Document 2, the bottom surface of the bottom (5) is formed with a depression (11) that is depressed inward from the inner peripheral end of the ground contact portion (16) as a base end, and further, a dome-shaped depression (12) is formed in the center of the depression (11), and these are depressed and deformed inward from 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 smooth demolding from the bottom mold. The reference numerals in parentheses refer to those in Patent Document 2.

[0006] Therefore, the inventors of the present invention considered that the dome-shaped recess (12) formed in the center of the vacuum absorption structure proposed in Patent Document 2 was particularly an obstacle to good demolding, and after extensive research into providing a vacuum absorption structure in the bottom that would improve demolding properties without impairing vacuum absorption performance by making the center flat, they discovered that the heat resistance was reduced due to insufficient stretching during blow molding near the center of the bottom.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a synthetic resin container having a vacuum absorption structure at the bottom that absorbs pressure changes inside the container after the contents are filled and sealed, which allows the area near the center of the bottom to be more stretched during blow molding. [Means for solving the problem]

[0008] The synthetic resin container according to the present invention is a synthetic resin container having a bottom portion provided with a vacuum absorbing structure that absorbs pressure changes inside the container after the container is filled with contents and sealed, the bottom portion including a ground contact portion and having legs extending in a circumferential direction, and a movable bottom plate portion having an outer periphery connected to the upper end of the inner surface of the legs rising from the inner periphery of the ground contact portion, the movable bottom plate portion including a curved surface that is curved radially outwardly of the container and is arranged around the central portion, and the curved surface has、 along the radial direction The curved surface portion is partially raised A plurality of recessed grooves are provided so as to protrude inward of the container, and the recessed grooves are The outer peripheral edge of the movable bottom plate portion is the starting point. Gradually increase the groove depth Then, the groove bottom surface of the recessed groove portion is curved toward the center at a predetermined depth so as to be parallel to the curved surface. , The terminal end of the central portion that reaches the peripheral edge side is The groove depth is set as specified. It is recessed so that It is configured as follows. [Effects of the Invention]

[0009] According to the present invention, in a synthetic resin container having a vacuum absorption structure at the bottom that absorbs pressure changes inside the container after the contents are filled and sealed, it is possible to further stretch the area near the center of the bottom during blow molding. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a front view showing an outline of a synthetic resin container according to an embodiment of the present invention. [Figure 2] 1 is a side view showing an outline of a synthetic resin container according to an embodiment of the present invention. [Figure 3] 1 is a bottom view showing an outline of a synthetic resin container according to an embodiment of the present invention. [Figure 4] 1 is a perspective view showing an outline of a synthetic resin container according to an embodiment of the present invention. [Figure 5] FIG. 2 is a cross-sectional view of the AA end of FIG. [Figure 6] 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. [Figure 7] FIG. 2 is a cross-sectional perspective view showing a cross section taken along the line BB in FIG. 1. [Figure 8] 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. [Figure 9] 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. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0012] 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 AA 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 BB in FIG. 1. 5, 6 and 7, the wall thickness of the container 1 that appears on the cross section is omitted.

[0013] 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. Furthermore, the container 1 has a bottom 5 equipped with a pressure reduction absorbing structure that absorbs the pressure loss inside the container when it is cooled to room temperature after being filled with the contents and sealed using a so-called hot pack, which will be described later.

[0014] 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 a predetermined container shape by biaxial stretch blow molding, or the like.

[0015] When manufacturing the 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 thereof, or blends of these resins with other resins, are preferred. Ethylene terephthalate-based thermoplastic polyesters such as polyethylene terephthalate are particularly preferred. Polycarbonate, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene, and the like can also be used.

[0016] 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.

[0017] The body 4 is a portion that 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).

[0018] 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.

[0019] In this embodiment, an example is shown in which a vacuum absorption panel 40 is provided in the body part 4 as an auxiliary means when the vacuum absorption performance is insufficient with only the vacuum absorption structure provided in the bottom part 5, and the vacuum absorption panel 40 provided in the body part 4 can be omitted as necessary.

[0020] Furthermore, two circumferential grooves 41, 42, and 43 extending annularly along the circumferential direction are provided on the upper end side and one on the lower end side of the body 4. These circumferential grooves 41, 42, and 43 are provided mainly to increase the load-bearing strength against loads from the lateral direction (direction perpendicular to the height direction), and can be omitted as necessary.

[0021] The bottom 5 includes a ground contact 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 (ground contact width) and outer diameter (ground contact diameter) of the ground contact 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 ground contact 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 outward from 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.

[0022] The bottom 5 has a movable bottom plate portion 55, with a flat, disc-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.

[0023] By doing this, as the pressure inside the container decreases after the contents have been filled and sealed using 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.

[0024] Furthermore, since 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 at this time, the container 1 may lose its independence and tip over. For this reason, the inner surface 53 of the leg portion 50 is defined as the height h from the ground contact portion 51 to the upper end where the outer circumferential edge side of the movable bottom plate portion 55 is connected. 50 However, it can be appropriately designed so that the height is sufficient to accommodate fluctuations in 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 indicated by a two-dot chain line.

[0025] Furthermore, the larger the capacity of the container 1, the heavier the contents become, and therefore the more the movable bottom plate portion 55 moves downward. Therefore, the height h of the leg portion 50 changes depending on the capacity of the container 1. 50 The height h of the leg 50 is to be designed appropriately. 50 If the pressure is relatively low, for example, if container 1 filled and sealed with contents is accidentally dropped, and the pressure inside the container increases instantaneously due to the impact of the drop, the contents are pressed into leg portion 50, which causes inner surface 53 of leg portion 50 to be pushed open from the inside, deforming it by curling up, and this tends to cause movable bottom plate portion 55 to bulge beyond ground contact portion 51. Once such deformation occurs, it is difficult to restore the original shape, and container 1 becomes unable to stand on its own, significantly reducing its commercial value.

[0026] 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.

[0027] When the inner surface 53 of the leg part 50 is formed by a plurality of surfaces connected vertically with different inclinations, if the number of surfaces is increased, the strength against the increase in internal pressure when dropped or hot packed is improved, but if deformation occurs, the tendency for it to be difficult to restore to its original shape becomes stronger. For this reason, the number of surfaces forming the inner surface 53 of the leg part 50 is determined by taking into consideration the balance between the resistance to deformation and the restorability, and by determining the number of surfaces that form the height h of the leg part 50. 50 However, it is preferable that the number of surfaces forming the inner surface 53 of the leg portion 50 is two as shown in the figure.

[0028] Each surface forming the inner surface 53 of the leg 50 may be formed so that its longitudinal cross section is linear, but in the example shown, the two surfaces 53a and 53b forming 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 as to be 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.

[0029] Furthermore, each surface forming the inner surface 53 of the leg portion 50 preferably forms an angle of 45 to 88° with the horizontal plane in a longitudinal 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, the angle formed by the horizontal plane and a line connecting the start point and end point of that surface in a longitudinal cross section is preferably 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 in the demolding process after blow molding.

[0030] As described above, the movable bottom plate portion 55 moves downward due to the weight of the contents, and if the movable bottom plate portion 55 is in a state where it 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 during vacuum absorption becomes larger. As a result, the pressure decrease inside the container can be absorbed more effectively, improving vacuum absorption performance.

[0031] In order to suppress deformation due to impact such as dropping while ensuring the desired decompression absorption performance, it is preferable that the center portion 56 of the movable bottom plate portion 55 is as high as possible as the outer circumferential 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 has a height h from the outer circumferential edge of the movable bottom plate portion 55 to the lowest point of the curved surface 57. 57 It is preferable that the height h is curved in the radial direction so that the height h is 1.0 to 4.0 mm. 57 If the height h is less than the above range, the volume that can absorb reduced pressure will be small, and the desired reduced pressure absorption performance will not be exhibited. 57 If the above range is exceeded, the movable bottom plate portion 55 tends to bulge beyond the ground contact portion 51 due to an impact such as being dropped, and when filling the contents, the movable bottom plate portion 55, when pressed down, tends to bulge beyond the ground contact portion 51 and tip over.

[0032] Furthermore, when the movable bottom plate portion 55 moves up and down while bending as a whole, the movable bottom plate portion 55 is deformed so that it is stretched in the radial direction and its length along the circumferential direction is shortened. In order to absorb this change in the length along the circumferential direction, a curved surface 57 arranged around the periphery of 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.

[0033] When providing the grooves 58 in the curved surface 57 of the movable bottom plate portion 55, it is conceivable to provide the grooves 58 at equal angular intervals along the circumferential direction to ensure uniform deformation of the movable bottom plate portion 55. However, if the interval between adjacent grooves 58 is too narrow, it will be impossible to provide markings such as a model number or lot number on the bottom surface. In consideration of this, in this embodiment, an even number of reference grooves 58 (58a) are arranged at equal angular intervals (45° in the illustrated example, preferably 22.5 to 90.0°), and grooves 58 (58b) are added every other time along the circumferential direction between adjacent reference grooves 58 (58a), thereby providing a plurality of grooves 58 (12 in the illustrated example, preferably 6 to 24) (see FIG. 3 ) to ensure uniform deformation of the movable bottom plate portion 55 and to ensure space for markings.

[0034] The grooves 58 are recessed so that their depth gradually increases from the outer peripheral edge SE of the movable bottom plate 55 toward the center at a predetermined depth, and their end TE, which reaches the peripheral edge of the central portion 56, has the predetermined depth. By providing the grooves 58 so that the 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 stretching 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.

[0035] The groove depth at the end TE of the recessed groove portion 58 is preferably 0.5 to 2.0 mm. If the depth is less than this range, the stretching is insufficient, and the improvement in heat resistance tends to be difficult to expect. On the other hand, if the depth exceeds this range, the bottom mold tends to be poorly released in the mold release step after blow molding, and poor shaping between the recessed groove portions 58 tends to occur.

[0036] Furthermore, by providing groove portion 58 so that end TE located on the peripheral side of central portion 56 protrudes inwardly of the container, and by further extending the area near the peripheral edge of central portion 56, movable bottom plate portion 55 can more easily move upwardly in response to a decrease in pressure inside the container. Furthermore, if the bottom surface of groove portion 58 were curved so as to convexly protrude inwardly of 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 making end TE of groove portion 58 protrude inwardly of the container, the range over which the bottom surface of groove portion 58 is curved approximately parallel to curved surface 57 can be widened, which also improves responsiveness to a decrease in pressure inside the container.

[0037] 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.

[0038] That is, in the present invention, the bottom portion 5 includes a ground contact portion 51, leg portions 50 extending in the circumferential direction, and a movable bottom plate portion 55 whose outer periphery is connected to the upper end of an 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 a central portion 56 and curved radially outwardly of the container, the curved surface 57 is provided with a plurality of grooves 58 recessed along the radial direction, and the grooves 58 are recessed so that their starting ends SE are on the outer periphery side of the movable bottom plate portion 55 and their ending ends TE, which reach the periphery side of the central portion 56, have a predetermined groove depth. Other detailed configurations can be modified as appropriate without being limited to those of the above-described embodiment. Furthermore, the detailed configurations described in the above-described embodiment can be selected and combined as appropriate. [Explanation of symbols]

[0039] 1 container 5 Bottom 50 Legs 51 Grounding part 55 Movable bottom plate section 56 Central part 57 Curved Surface 58 Concave groove part SE start TE Termination

Claims

1. 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; and the movable bottom plate portion includes a curved surface that is disposed around the central portion and curves convexly outward from the container along a radial direction, 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.

2. 2. The synthetic resin container according to claim 1, wherein the curved surface is curved so that the height of the lowest point of the curved surface relative to the outer periphery of the movable bottom plate portion is 1.0 to 4.0 mm.

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