JP7413717B2 - Synthetic resin container - Google Patents

Description

The present invention relates to a synthetic resin container with improved vertical compressive strength.

Conventionally, synthetic resin containers are made by forming a cylindrical preform with a bottom using a thermoplastic resin such as polyethylene terephthalate, and then molding this preform into a bottle shape by biaxial stretch blow molding or the like. They are used in a wide range of fields as containers for holding various beverages, seasonings, etc.

In addition, sales formats for beverage bottles that use such synthetic resin containers are diversifying, and during the cold winter months, they are displayed in hot warmers at stores to warm the contents to an appropriate temperature. Sales have also become a familiar form of general sales (for example, see Patent Document 1).

JP 2017-52559 Publication

By the way, the container disclosed in Patent Document 1 includes a bottom portion having a depressed portion located at the center and a grounding portion provided around the depressed portion. This type of bottom shape is a well-known shape not only for containers used for heated sales but also for this type of synthetic resin container, and the grounding part provided around the recessed part is relatively small. They tend to be formed into thin walls.

In other words, during blow molding, a preform set in a blow mold is generally stretched in the axial direction by a stretching rod, and also in the axial and circumferential directions by blow air, and the stretched part is blow molded. By shaping the inner surface of the mold, it is molded into a predetermined container shape. At this time, the bottom side of the stretched preform first contacts the part that forms the depression located at the center of the bottom, and then sequentially contacts the periphery of the part while being further stretched. The bottom shape is formed. For this reason, the ground contact portion provided around the recessed portion is in a more extended state, and is therefore easier to be formed into a thinner wall.

According to studies by the present inventors, the container disclosed in Patent Document 1 has a lower overall height so that it can be displayed in a hot warmer, but a larger body diameter to ensure a predetermined capacity. However, we found that the larger the body diameter, the stronger the tendency for the ground contact part to be formed into a thinner wall. For example, when the contents are filled and sealed and supplied to the market, when they are compressed in the axial direction due to the loading pressure applied when they are stacked in boxes during transportation and storage, buckling occurs starting at the ground contact part. It has been found that deformation may occur.

The present invention has been made in view of the above-mentioned circumstances, and provides a synthetic resin container having a bottom portion having a depressed portion located in the center and a grounding portion provided around the depressed portion. Therefore, it is an object of the present invention to provide a synthetic resin container that has improved longitudinal compressive strength (axial load strength) by suppressing buckling deformation originating from the grounding part when compressed in the axial direction. purpose.

A 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 recessed portion, wherein the grounding portion is located downwardly. A heel portion that is formed of a curved surface that is convex to the outside of the container and whose diameter gradually decreases toward the outside of the container, and an inclined surface portion that slopes downward from the recessed portion side toward the outside in the radial direction, extending along the circumferential direction. A plurality of grooves are formed in a radial pattern intersecting with the ground contact portion , and between the slope portion and the recessed portion, there is a first step surface located on the slope portion side, and a plurality of grooves extending from the first step surface. an annular stepped portion including a second stepped surface located above the groove, and a groove bottom of the groove is formed to be flush with the first stepped surface of the annular stepped portion. .

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

1 is a front view schematically showing a synthetic resin container according to an embodiment of the present invention. FIG. 1 is a bottom view schematically showing a synthetic resin container according to an embodiment of the present invention. 1 is a perspective view schematically showing a synthetic resin container according to an embodiment of the present invention. FIG. 3 is an end view taken along the line AA in FIG. 2; 3 is a BB end view of FIG. 2. FIG. FIG. 6 is an explanatory diagram showing the end surface shown in FIG. 4 and the end surface shown in FIG. 5 superimposed. FIG. 3 is an enlarged end view of main parts of Comparative Example 1. FIG. 6 is an enlarged end view of a 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 schematically showing a synthetic resin container according to the present embodiment, FIG. 2 is a bottom view of the container, and FIG. 3 is a perspective view of the container viewed diagonally from below.

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.

Furthermore, 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 can be displayed in a hot warmer at a store so that it is suitable for heated sales. Taking this into consideration, the design was designed to ensure a certain capacity while keeping the overall height low.

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

As the thermoplastic resin used, any 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 can be used, and in particular, ethylene terephthalate such as polyethylene terephthalate can be used. Thermoplastic 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 formed into a single layer, but can also be formed into a multilayer structure including a gas barrier layer, depending on the characteristics required of the container 1.

The spout 2 is a cylindrical portion that serves as a spout for pouring the contents. A screw thread for attaching a lid (not shown) is provided on the side surface of the opening end of the opening 2.
The shoulder portion 3 is a portion that is connected to the lower end of the mouth portion 2, expands in diameter toward the body portion 4, and connects the mouth portion 2 and the body portion 4. In the illustrated example, the shoulder portion 3 is generally shaped like a truncated cone.
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.
Further, 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 referred to as a longitudinal cross section.

Six-sided pressure adjustment panels 40 that adjust the pressure inside the container by deforming according to changes in the pressure inside the container are arranged on the body 4 at predetermined intervals along the circumferential direction. The specific configuration of the pressure adjustment panel 40 is not particularly limited, and as the pressure inside the container decreases, it deforms inwardly, and as the pressure inside the container increases, it deforms outwards, thereby deforming the container. Any structure is sufficient as long as it can absorb internal pressure changes and thereby prevent uneven deformation of the container 1.

In addition, in order to increase load-bearing strength against loads from the lateral direction (direction perpendicular to the height direction), the body portion 4 is provided with an annular structure along the circumferential direction on each of its upper and lower end sides. Although extending circumferential grooves 41 and 42 are provided, the specific configuration of the body 4 is not limited to the illustrated example.

In this embodiment, the bottom portion 5 has a depressed portion 50 located at the center and a grounding portion 51 provided around the depressed portion 50.

The depressed portion 50 can be formed as a region in which the center portion of the bottom portion 5 is depressed inward of the container in a generally truncated conical shape. In the illustrated example, eight reinforcing ribs 50a projecting outward from the container are provided radially on the side surface of the recessed portion 50 in order to increase the rigidity of the recessed portion 50. The present invention is not limited to the illustrated example as long as deformation of the recessed portion 50 such as storage can be suppressed.

The grounding portion 51 provided around the recessed portion 50 is a portion that comes into contact with the horizontal surface when the container 1 is erected on the horizontal surface, and is a convex portion outward of the container whose diameter gradually decreases downward. It is provided so as to extend along the circumferential direction between a heel portion 52 having a curved surface and an inclined surface portion 53 that slopes downwardly toward the outside in the radial direction from the recessed portion 50 side.

In providing the grounding portion 51 in this manner, as shown in _FIG . It is preferable that the perpendicular line VL ₁ drawn down is formed in the shape of a circular arc passing through the grounding portion 51 and projecting outward from the container. On the other hand, the end edge portion 53a of the inclined surface portion 53 on the side of the grounding portion 51 has a vertical cross section where a perpendicular line _VL2 drawn from the center _O2 along the axial direction passes through the grounding portion 51, and the end edge portion 53a is on the lower end side of the heel portion 52. It is preferable that the container be formed into an outwardly convex arc shape with a smaller radius of curvature than the radius of curvature of the arc forming the end edge portion 52a.
Note that FIG. 4 is an end view taken along the line AA in FIG. 2, in which the wall thickness appearing on the end surface is omitted and the end surface of the main part of the bottom portion 5 is shown in an enlarged manner.

The width (grounding width) and outer diameter (grounding diameter) of the grounding portion 51 can be appropriately designed so that the container 1 can stably stand on its own. In the illustrated example, the perpendicular line VL ₁ and the perpendicular line VL ₂ are separated, the perpendicular line VL ₁ passing through the edge of the grounding part 51 on the side of the inclined surface part 53, and the perpendicular line VL ₂ passing through the edge of the grounding part 51 on the side of the heel part 52. It is designed to pass through the edge (see Figure 4). In other words, the intersection of the perpendicular line _VL2 drawn from the center _O2 of the arc forming the end edge 53a and the arc forming the end edge 52a, and the point below from the center _O1 of the arc forming the end edge 52a. The intersection point between the perpendicular line _VL1 and the circular arc forming the edge portion 53a is located on the same plane perpendicular to the central axis C, and the intersection point is such that it smoothly connects to the edge portions 52a and 53a at these intersection points. , a grounding portion 51 is formed.

Therefore, the distance between the perpendicular line VL ₁ and the perpendicular line VL ₂ is the designed width of the ground contact portion 51. The perpendicular line VL ₁ and the perpendicular line VL ₂ may be designed to be further apart if necessary, but the 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.
Alternatively, the perpendicular line VL ₁ and the perpendicular line VL ₂ may be designed to overlap. 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 grooves 55 arranged at equal intervals along the circumferential direction are formed radially so as to intersect with the ground contact portion 51 extending along the circumferential direction. ing. The groove 55 can be formed so that the grounding portion 51 and its surroundings are partially raised inward of the container. The groove bottom 55a of the groove 55 can be formed into a rectangular shape that is elongated 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 extends from both widthwise edges of the groove bottom 55a. It can be formed to stand up diagonally outward.
In the illustrated example, eight grooves 55 are provided, but the present invention is not limited to this. The number of grooves 55 can be set to, for example, 4 to 16, if necessary. The width of the groove bottom 55a of the groove 55 can be, for example, 1 to 18 mm.

In a container 1 having a bottom portion 5 having a depressed portion 50 located at the center and a grounding portion 51 provided around the depressed portion 50, when compressed in the axial direction, the bottom portion 5 is compressed from the grounding portion 51 as a starting point. Buckling deformation may occur. As a countermeasure against such a case, according to the present embodiment, the grounding part 51 is provided to extend along the circumferential direction, and a plurality of grooves 55 are formed radially to intersect with the grounding part 51. When stress is applied to the ground contact portion 51, a moderate amount of deflection deformation occurs in the groove 55, which can be restored, thereby absorbing the stress. 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.

Furthermore, when the container is sold heated, the contents and the air in the head space expand due to heating, increasing the pressure inside the container. As a result, if the grounding portion 51 is deformed so as to bulge unevenly outward from the container, the self-sustaining stability of the container 1 will be impaired, but according to the present embodiment, such a problem can be effectively overcome. can be avoided.

In order to more effectively exhibit these effects, there is a first stepped surface 54a located on the inclined surface section 53 side and a first stepped surface 54a located above the first stepped surface 54a between the inclined surface section 53 and the depressed section 50. An annular step portion 54 including a second step surface 54b can be provided. It is preferable that the first step surface 54a and the second step surface 54b are on a plane perpendicular to the central axis C, and in order to avoid stress concentration, the longitudinal section is a circular arc-shaped connecting portion that is convex toward the outside of the container. It is preferable that the first step surface 54a and the second step surface 54b are connected to each other via 54c.

As described above, it is preferable that the end edge 53a of the inclined surface part 53 on the side of the grounding part 51 has a vertical cross section formed in an arc shape convex to the outside of the container, but the other part 53b is It is preferable that the vertical cross section is formed in the shape of a circular arc convex inward of the container. In the longitudinal section, the inclined surface portion 53 and the first stepped surface 54a are smoothly continuous so that the tangent to the arc at the intersection of the inclined surface portion 53 and the first stepped surface 54a is on the first stepped surface 54a. Preferably, it is formed so as to. Similarly, the edge portion 53a of the inclined surface portion 53 on the side of the grounding portion 51 and the other portion 53b are formed so as to be smoothly continuous so that tangent lines touching each coincide with each other at the intersection point of the two in the longitudinal section. It is preferable that the
Note that an imaginary line extending the arc formed by the edge portion 53a inward in the radial direction and an imaginary line extending the arc formed by the other portion 53b radially outward are shown as dashed 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, the groove bottom portion 55a of the concave groove 55 is formed in the annular step portion, as shown in FIGS. It can be formed so as to be flush with the first step surface 54a of 54.
Note that FIG. 5 is a BB end view of FIG. 2, and similarly to FIG. 4, the wall thickness appearing on the end surface is omitted and the end surface of the main part of the bottom portion 5 is shown in an enlarged manner. FIG. 6 is an explanatory diagram showing the end surface shown in FIG. 4 and the end surface shown in FIG. 5 superimposed.

Hereinafter, the present invention will be explained in more detail by giving specific examples.

A preform weighing approximately 24 g was injection molded using polyethylene terephthalate resin. After the molded preform was heated to soften it, it was set in a blow mold and biaxially stretched blow molded to create a container 1 having the shape of the container shown in FIGS. 1 to 6.
The capacity of the container 1 is approximately 527 mL, the height H is approximately 171.5 mm, the body diameter D is approximately 73 mm, and the average wall thickness of the container 1 calculated from the weight of the preform is approximately 0.3 mm. Ta. Further, 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., and a lid (not shown) was attached to the mouth 2 and sealed. The headspace volume was approximately 12 mL.
When the container 1, which has been filled and sealed with the contents in this manner, is compressed by pressing the presser from above downward in the axial direction at a compression speed of 50 mm/min, the pressure exceeds about 270 N, and then it touches the ground. Deformation was observed in portion 51, but after confirming the deformation, the load was released and it returned to its original shape.
Further, when the container 1 was compressed until buckling occurred, the vicinity of the connecting portion between the mouth portion 2 and the shoulder portion 3 buckled so as to cave in. The load at that time was approximately 484N.

[Comparative example 1]
As shown in FIG. 7, a container similar to that in Example 1 was created, except that the grounding portion 51C was provided flat over the entire circumference so that the grounding width w was approximately 4 mm and the grounding diameter d was approximately 56 mm. A compressive strength test was conducted 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 surface shown in FIG. 4 of Example 1.

The vertical compressive strength under the condition of filling and sealing the contents in the same manner as in Example 1 was about 283 N, and the ground contact portion and the circumferential groove portion provided at the lower end of the body buckled at the same time.

[Comparative example 2]
As shown in FIG. 8, grooves 55C formed by partially protruding the grounding portion 51C and its surroundings inward of the container are provided with the same groove width as in Example 1, and eight grooves 55C are formed along the circumferential direction. A container similar to Comparative Example 1 was prepared except that the containers were arranged at equal intervals.
Note that FIG. 8 is an enlarged sectional view of a main part of Comparative Example 2, in which portions corresponding to the end faces shown in FIGS. 4 and 5 of Example 1 are superimposed in the same way as FIG. 6.

When a compressive strength test was conducted under the conditions of filling and sealing the contents in the same manner as in Example 1, deformation began at around 270 N or more, and after confirming the deformation, when the load was released, it recovered to some extent. However, when the ground-contact area was observed after restoration, wrinkle-like traces that were thought to be caused by deformation were observed, and as in Example 1, the restoration was not complete.

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 suitable for heating sales was shown, but the invention is not limited to this. In this type of synthetic resin container, the location where buckling occurs when compressed in the axial direction varies depending on the shape of the container, but the present invention provides a recess located in the center and a recess located around this recess. It can be effectively applied as a countermeasure against buckling deformation starting from the grounding part when compressed in the axial direction in a synthetic resin container with a bottom having a grounding part. can.

1 Container 5 Bottom part 50 Recessed part 51 Ground contact part 52 Heel part 53 Inclined surface part 54 Annular step part 54a First step surface 54b Second step surface 55 Concave groove 55a Groove bottom part

Claims (2)

A container made of synthetic resin, comprising a bottom portion having a depressed portion located at the center and a grounding portion provided around the depressed portion,
The ground contact portion is between a heel portion consisting of a curved surface convex to the outside of the container whose diameter gradually decreases downward, and an inclined surface portion that slopes downward from the depressed portion side toward the outside in the radial direction. Extending along the circumferential direction,
A plurality of grooves intersecting with the grounding portion are formed radially,
An annular stepped portion is provided between the inclined surface portion and the recessed portion, and includes a first stepped surface located on the inclined surface portion side and a second stepped surface located above the first stepped surface,
A synthetic resin container, wherein a groove bottom of the groove is formed to be flush with the first step surface of the annular step portion. A container made of synthetic resin, comprising a bottom portion having a depressed portion located at the center and a grounding portion provided around the depressed portion,
The ground contact portion is between a heel portion consisting of a curved surface convex to the outside of the container whose diameter gradually decreases downward, and an inclined surface portion that slopes downward from the depressed portion side toward the outside in the radial direction. Extending along the circumferential direction,
A plurality of grooves intersecting with the grounding portion are formed radially,
An annular stepped portion is provided between the inclined surface portion and the recessed portion, and includes a first stepped surface located on the inclined surface portion side and a second stepped surface located above the first stepped surface,
The ground contact portion and the first step surface are smoothly connected by a curved surface,
In the longitudinal cross-sectional shape,
The arc-shaped cross section on the first stepped surface side of the inclined surface portion and the cross section of the first stepped surface are connected so as to be in contact with each other,
An arc-shaped cross section of the inclined surface portion on the grounding portion side and a cross section of the grounding portion are connected so as to be in contact with each other,
The first step surface and the second step surface are located on a plane perpendicular to the central axis.
A synthetic resin container characterized by:

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