JP2021066460A - Synthetic resin container - Google Patents

Abstract

To provide a container 1 including a bottom 5 having a recess 50 positioned at the center and a ground part 51 provided in the periphery of the recess which improves a longitudinal compression strength by suppressing generation of buckling deformation with the ground part as a starting point when being compressed in an axial direction.SOLUTION: A ground part 51 annularly extending in a circumferential direction is provided between a heel part 52 composed of a curved surface being convex outward of the container gradually decreased in diameter downward, and an inclined plane part 53 inclined downward from a recess 50 side toward the outside in a radial direction, and a plurality of recessed grooves 55 crossing the ground part 51 are radially formed.SELECTED DRAWING: Figure 2

Description

The present invention relates to a synthetic resin container having improved longitudinal compressive strength.

Conventionally, a container made of synthetic resin, which is formed by forming a bottomed tubular preform using a thermoplastic resin such as polyethylene terephthalate and then molding this preform into a bottle shape by biaxial stretching blow molding or the like. It is used in a wide range of fields as a container containing various beverages and various seasonings.

In addition, the sales form of bottles for beverages using such synthetic resin containers is also diversifying, and in the cold season of winter, they are displayed on hot warmers in stores to warm the contents to an appropriate temperature. Being sold has also become familiar as a general sales form (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-25559

By the way, the container disclosed in Patent Document 1 includes a bottom having a recessed portion located at the center and a ground contact portion provided around the recessed portion. Such a bottom shape is a well-known shape not only in containers used for heated sales but also in this type of synthetic resin container, and the ground contact portion provided around the depressed portion is relatively large. It tends to be molded thin.

That is, in the case of blow molding, in general, the preform set in the blow molding mold is stretched in the axial direction by the stretching rod, and is stretched in the axial direction and the circumferential direction by the blow air, and blow molding is performed on the stretched portion. By shaping the inner surface shape of the mold, it is molded into a predetermined container shape. At this time, the bottom side of the stretched preform first contacts the portion forming the depressed portion located in the center of the bottom, and then sequentially contacts the periphery of the portion while being further stretched. The bottom shape is shaped. For this reason, the ground contact portion provided around the depressed portion is in a more stretched state, and it is easy to form a thin wall by that amount.

According to the study by the present inventors, in the container disclosed in Patent Document 1, the overall height is lowered so that it can be displayed on a hot warmer, but the body diameter is increased so that a predetermined capacity can be secured. However, it was found that the larger the body diameter, the stronger the tendency for the ground contact portion to be formed thinner. Then, for example, when the contents are filled and sealed and supplied to the market, when the contents are compressed in the axial direction by the load pressure applied when the contents are packed and sealed during transportation and storage, the buckling starts from the ground contact portion. It has been found that deformation may occur.

The present invention has been made in view of the above circumstances, and is a synthetic resin container having a bottom portion having a recessed portion located at the center and a ground contact portion provided around the depressed portion. To provide a synthetic resin container with improved longitudinal compressive strength (axial load strength) by suppressing buckling deformation starting from the ground contact portion when compressed in the axial direction. The purpose.

The synthetic resin container according to the present invention is a synthetic resin container having a bottom portion having a recessed portion located at the center and a grounding portion provided around the depressed portion, and the grounding portion is downward. Extends along the circumferential direction between the heel portion formed of a curved surface that is convex outward of the container that gradually reduces in diameter toward the container and the inclined surface portion that inclines downward in the radial direction from the depressed portion side. It has a configuration in which a plurality of concave grooves intersecting with the ground contact portion are formed radially.

According to the present invention, in a synthetic resin container having a bottom portion having a recessed portion located at the center and a grounding portion provided around the depressed portion, the grounding portion is provided when compressed in the axial direction. The longitudinal compressive strength can be improved by suppressing the occurrence of buckling deformation as the starting point.

It is a front view which shows the outline of the synthetic resin container which concerns on embodiment of this invention. It is a bottom view which shows the outline of the synthetic resin container which concerns on embodiment of this invention. It is a perspective view which shows the outline of the synthetic resin container which concerns on embodiment of this invention. It is the AA end view of FIG. It is a BB end view of FIG. It is explanatory drawing which shows the end face shown in FIG. 4 and the end face shown in FIG. 5 superimposed. It is an enlarged end view of the main part of Comparative Example 1. It is an enlarged end view of the main part of Comparative Example 2.

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

FIG. 1 is a front view showing an outline of a synthetic resin container according to the present embodiment, FIG. 2 is a bottom view thereof, and FIG. 3 is a perspective view showing a perspective view from diagonally below.

The container 1 shown in these figures includes a mouth portion 2, a shoulder portion 3, a body portion 4, and a bottom portion 5, and the body portion 4 is formed in a substantially cylindrical shape, and is generally referred to as a round bottle. It has a container shape.

In addition, the container 1 shown in these figures has a capacity of about 527 mL, a height H of about 171.5 mm, and a body diameter D of about 73 mm, and should be displayed on a hot warmer in a store so as to be suitable for heated sales. In consideration of the above, a predetermined capacity can be secured while lowering the overall height.

In such a container 1, a bottomed tubular preform is formed by injection molding, compression molding, or the like using a thermoplastic resin, and this preform is formed into a predetermined container shape by biaxial stretching blow molding or the like. Manufactured by

As the thermoplastic resin to be used, any resin capable of blow molding can be used. Specifically, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, amorphous polyarylate, polylactic acid, polyethylene furanoate or copolymers thereof can be used, and in particular, ethylene terephthalate such as polyethylene terephthalate can be used. Polyplastic polyesters are preferably used. Two or more of these resins may be mixed, or other resins may be blended. Polycarbonate, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene, etc. can also be used. The preform is not limited to being molded into a single layer, but can also be molded into multiple layers including a gas barrier layer and the like, depending on the characteristics required for the container 1.

The mouth portion 2 is a cylindrical portion that serves as a spout for the contents. A screw thread for attaching a lid (not shown) is provided on the side surface of the mouth portion 2 on the opening end side.
The shoulder portion 3 is a portion that connects to the lower end of the mouth portion 2 and expands in diameter toward the body portion 4 to connect the mouth portion 2 and the body portion 4. In the illustrated example, the shoulder portion 3 is formed in a substantially truncated cone shape.
The body portion 4 occupies most of the height direction of the container 1, and the upper end is connected to the shoulder portion 3 and the lower end is connected to the bottom portion 5.

Here, the height direction means a direction orthogonal to the horizontal plane when the container 1 is upright on the horizontal plane with the mouth portion 2 facing up, and the container 1 is in this state (the state shown in FIG. 1). The vertical and horizontal directions and the vertical and horizontal directions of the above shall be specified.
Further, although the central axis is indicated by reference numeral C in FIG. 1, the cross section cut by the surface including the central axis C is referred to as a vertical cross section unless otherwise specified.

Six-sided pressure adjusting panels 40 for adjusting the pressure inside the container by deforming according to the change in pressure inside the container are arranged on the body 4 at predetermined intervals along the circumferential direction. The specific configuration of the pressure adjusting panel 40 is not particularly limited, and the container is deformed inward as the pressure inside the container decreases, while deformed outward in the container as the pressure inside the container increases. It suffices if it is configured so as to absorb the pressure change in the container 1 and thereby suppress the non-uniform deformation of the container 1.

Further, in order to increase the load-bearing strength against a load from the lateral direction (direction orthogonal to the height direction), the body portion 4 is annularly formed along the circumferential direction on each of the upper end side and the lower end side thereof, for example. Although extending peripheral groove portions 41 and 42 are provided, the specific configuration of the body portion 4 is not limited to the illustrated example.

In the present embodiment, the bottom portion 5 has a recessed portion 50 located at the center and a ground contact portion 51 provided around the depressed portion 50.

The depressed portion 50 can be formed as a portion in which the central portion of the bottom portion 5 is recessed inward in the container in a substantially truncated cone shape. In the illustrated example, eight reinforcing ribs 50a projecting outward from the container are radially provided on the side surface of the recessed portion 50 in order to increase the rigidity of the depressed portion 50, but the independence of the container 1 is impaired. As long as the deformation of the recessed portion 50 can be suppressed, the example is not limited to the illustrated example.

The ground contact portion 51 provided around the recessed portion 50 is a portion that comes into contact with the horizontal plane when the container 1 is upright on the horizontal plane, and is convex outward of the container that gradually shrinks in diameter downward. It is provided so as to extend along the circumferential direction between the heel portion 52 formed of a curved surface and the inclined surface portion 53 inclined downward from the depressed portion 50 side toward the outside in the radial direction.

In this way, the provision of the ground portion 51, as shown in FIG. 4, the lower end side of the edge portion 52a of the heel 52 contiguous with at least a ground portion 51, longitudinal section, along the center O ₁ in the axial direction It is preferable that the vertical line VL ₁ drawn down is formed in a convex arc shape outward of the container passing through the ground contact portion 51. On the other hand, the edge portion 53a on the ground contact portion 51 side of the inclined surface portion 53 has a vertical cross section in which a perpendicular line VL _{2 descending from the center O 2} along the axial direction passes through the ground contact portion 51 and is on the lower end side of the heel portion 52. It is preferable that the arc shape is convex outward of the container, which has a radius of curvature smaller than the radius of curvature of the arc forming the edge portion 52a.
Note that FIG. 4 is an end view of AA of FIG. 2, in which the wall thickness appearing on the end face is omitted and the end face of the main part of the bottom 5 is enlarged and shown.

The width (grounding width) and outer diameter (grounding diameter) of the grounding portion 51 can be appropriately designed so that the container 1 can be stably self-supported. In the illustrated example, the perpendicular line VL ₁ and the perpendicular line VL ₂ are separated from each other, the perpendicular line VL ₁ passes through the edge of the ground contact portion 51 on the inclined surface portion 53 side, and the perpendicular line VL ₂ is the end of the ground contact portion 51 on the heel portion 52 side. It is designed to pass through the edge (see Figure 4). In other words, under the intersection of the arcs forming the arc center O perpendicular VL ₂ beat from ₂ and edge 52a which forms an edge portion 53a, from the center O ₁ of the arc forming the edge 52a The intersection of the perpendicular line VL ₁ and the arc forming the edge portion 53a is located on the same plane orthogonal to the central axis C, and at these intersections, the intersections are smoothly connected to the edge portions 52a and 53a. , The ground contact portion 51 is formed.

Therefore, _{the separation distance between the perpendicular line VL 1} and the perpendicular line VL ₂ is the width of the design ground contact portion 51. The perpendicular line VL ₁ and the perpendicular line VL ₂ may be designed to be separated from each other as necessary, but _{the separation distance between the perpendicular line VL 1} and the perpendicular line VL ₂ is preferably 4 mm or less, more preferably 3 mm. It is as follows.
Further, the perpendicular line VL ₁ and the perpendicular line VL ₂ may be designed to overlap each other. In this case, the ground contact portion 51 is provided on the boundary line between the heel portion 52 and the inclined surface portion 53.

Further, in the illustrated example, eight concave grooves 55 arranged at equal intervals along the circumferential direction are formed radially so as to intersect the ground contact portion 51 extending along the circumferential direction. ing. The concave groove 55 can be formed so that the ground contact portion 51 and its periphery are partially raised inward of the container. The groove bottom portion 55a of the concave groove 55 can be formed in a rectangular shape long in the radial direction, and the side wall portion 55b connected to the heel portion 52, the ground contact portion 51, and the inclined surface portion 53 has a width from both end edges in the width direction of the groove bottom portion 55a. It can be formed so as to stand diagonally outward in the direction.
In the illustrated example, eight concave grooves 55 are arranged, but the present invention is not limited to this. The number of recessed grooves 55 arranged can be, for example, 4 to 16, if necessary. The width of the groove bottom portion 55a of the concave groove 55 can be, for example, 1 to 18 mm.

In the container 1 having a bottom portion 5 having a recessed portion 50 located at the center and a grounding portion 51 provided around the depressed portion 50, when compressed in the axial direction, the grounding portion 51 is used as a starting point. Buckling deformation may occur. As a countermeasure in such a case, according to the present embodiment, the ground contact portion 51 is provided so as to extend along the circumferential direction, and a plurality of concave grooves 55 intersecting the ground contact portion 51 are formed radially. When stress is applied to the ground contact portion 51, an appropriate amount of bending deformation that can be restored is generated in the concave groove 55, whereby the stress can be absorbed. As a result, buckling deformation starting from the ground contact portion 51 can be suppressed, and the longitudinal compressive strength of the container 1 is improved.

In addition, when the product is sold by heating, the air in the contents and head space expands due to the heating, and the pressure inside the container increases. As a result, if the ground contact portion 51 is deformed so as to bulge unevenly to the outside of the container, the self-sustaining stability of the container 1 is impaired, but according to the present embodiment, such a defect is also effective. Can be avoided.

In order to exert these effects more effectively, the first stepped surface 54a located on the inclined surface portion 53 side and the first stepped surface 54a located above the first stepped surface 54a are located between the inclined surface portion 53 and the depressed portion 50. An annular step portion 54 including the second step surface 54b can be provided. The first stepped surface 54a and the second stepped surface 54b are preferably on a plane orthogonal to the central axis C, respectively, and in order to avoid stress concentration, an arc-shaped connecting portion whose vertical cross section is convex outward of the container. It is preferable that the first stepped surface 54a and the second stepped surface 54b are connected to each other via the 54c.

As described above, it is preferable that the end edge portion 53a of the inclined surface portion 53 on the ground contact portion 51 side has a vertical cross section formed in an arc shape that is convex outward of the container. It is preferable that the vertical cross section is formed in an arc shape that is convex inward of the container. Then, in the vertical cross section, the inclined surface portion 53 and the first stepped surface 54a are smoothly continuous so that the tangent line of the arc at the intersection of the inclined surface portion 53 and the first stepped surface 54a is on the first stepped surface 54a. It is preferably formed so as to. Similarly, the edge portion 53a on the ground contact portion 51 side of the inclined surface portion 53 and the other portion 53b are formed so as to be smoothly continuous so that the tangents in contact with each other coincide with each other at the intersection of the two in the vertical cross section. It is preferable that it is.
A virtual line in which the arc formed by the edge portion 53a is extended inward in the radial direction and a virtual line in which the arc formed by the other portion 53b is extended in the radial direction are shown by chain lines in FIG. 4, respectively.

In this way, when the annular step portion 54 is provided between the inclined surface portion 53 and the depressed portion 50, as shown in FIGS. 5 and 6, the groove bottom portion 55a of the concave groove 55 is the annular step portion. It can be formed so as to be flush with the first stepped surface 54a of 54.
Note that FIG. 5 is a view of the BB end face of FIG. 2, and as in FIG. 4, the wall thickness appearing on the end face is omitted, and the main end face of the bottom portion 5 is enlarged and shown. FIG. 6 is an explanatory view showing the end face shown in FIG. 4 and the end face shown in FIG. 5 superimposed.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

A preform weighing about 24 g was injection-molded using a polyethylene terephthalate resin. After the molded preform was heated and softened, it was set in a blow molding mold, and the container 1 was prepared so as to have the container shape shown in FIGS. 1 to 6 by biaxial stretching blow molding.
The capacity of the container 1 is about 527 mL, the height H is about 171.5 mm, the body diameter D is about 73 mm, and the average wall thickness of the container 1 calculated from the weight of the preform is about 0.3 mm. It was. The average wall thickness of the container 1 calculated from the weight of the preform was about 0.23 mm.

The obtained container 1 was filled with about 515 mL of water at about 85 ° C. as a content, and a lid (not shown) was attached to the mouth 2 and sealed. The volume of headspace was about 12 mL.
When the presser was pressed downward in the axial direction from above against the container 1 filled and sealed with the contents in this way and compressed at a compression rate of 50 mm / min, it touched down from around 270 N. Deformation was observed in the portion 51, but after confirming the deformation, the original shape was restored when the load was released.
Further, when the container 1 was compressed until buckling occurred, the container 1 buckled so that the vicinity of the connecting portion between the mouth portion 2 and the shoulder portion 3 was depressed. The load at that time was about 484 N.

[Comparative Example 1]
As shown in FIG. 7, a container similar to that of the first embodiment was prepared and carried out except that the ground contact portion 51C was provided flatly over the entire circumference so that the ground contact width w was about 4 mm and the ground contact diameter d was about 56 mm. A compressive strength test was carried out in the same manner as in Example 1.
Note that FIG. 7 is an enlarged end view of a main part of Comparative Example 2 showing a portion corresponding to the end face shown in FIG. 4 of Example 1.

The longitudinal compressive strength under the condition that the contents were filled and sealed in the same manner as in Example 1 was about 283N, and the ground contact portion and the peripheral groove portion provided on the lower end side of the body portion buckled at the same time.

[Comparative Example 2]
As shown in FIG. 8, a concave groove 55C formed by partially raising the ground contact portion 51C and its periphery inward in the container is provided with the same groove width as in the first embodiment, and eight concave grooves 55C are provided along the circumferential direction. A container similar to that of Comparative Example 1 was prepared except that the containers were arranged at equal intervals.
Note that FIG. 8 is an enlarged cross-sectional view of a main part of Comparative Example 2 in which the portions corresponding to the end faces shown in FIGS. 4 and 5 of Example 1 are overlapped in the same manner as in FIG.

When the compressive strength test was carried out under the condition that the contents were filled and sealed in the same manner as in Example 1, the deformation started from around 270 N, and after confirming the deformation, it was restored to some extent when the load was released. However, when the ground contact portion after restoration was observed, wrinkle-like traces which were considered to have been caused by deformation were observed, and as in Example 1, the restoration was not completely performed.

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

For example, in the above-described embodiment, an example suitable for heated sales is shown, but the present invention is not limited to this. In this type of synthetic resin container, the location where buckling occurs when compressed in the axial direction differs depending on the shape of the container, but the present invention provides the recessed portion located in the center and the periphery of the recessed portion. In a synthetic resin container having a bottom having a grounded portion, it can be effectively applied as a countermeasure against buckling deformation starting from the grounded portion when compressed in the axial direction. it can.

1 Container 5 Bottom 50 Depressed part 51 Grounding part 52 Heel part 53 Inclined surface part 54 Circular stepped part 54a First stepped surface 54b Second stepped surface 55 Concave groove 55a Groove bottom

Claims (3)

A synthetic resin container having a bottom portion having a recessed portion located in the center and a ground contact portion provided around the depressed portion.
The ground contact portion is formed between a heel portion formed of an outwardly convex curved surface that gradually reduces in diameter downward and an inclined surface portion that inclines downward in the radial direction from the depressed portion side. Extending along the circumferential direction,
A synthetic resin container characterized in that a plurality of concave grooves intersecting the ground contact portion are formed in a radial pattern. An annular stepped portion including a first stepped surface located on the inclined surface portion side and a second stepped surface located above the first stepped surface is provided between the inclined surface portion and the depressed portion. The synthetic resin container according to claim 1. The synthetic resin container according to claim 2, wherein the groove bottom portion of the concave groove is formed so as to be flush with the first step surface of the annular step portion.

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