JP7807784B2 - Blow Molded Containers - Google Patents

Description

The present invention relates to a blow-molded container having a hollow, bottomed cylindrical body, and more specifically to a blow-molded container with excellent buckling strength against a compressive load in a direction perpendicular to the bottom.

Blow-molded containers can be produced, for example, by extrusion blow molding, in which an extruded cylindrical parison is blown (see, for example, Patent Document 1). Here, the larger the radius of curvature of the peripheral edge of the bottom of the blow-molded container in the longitudinal cross section of the blow-molded container (the longitudinal cross section of the blow-molded container in the direction perpendicular to the bottom), the better the adhesion to the internal shape of the mold when the parison is blow-molded. As a result, the moldability of such blow-molded containers can be improved. However, when a blow-molded container is placed on a horizontal surface, the contact area of the bottom is reduced, resulting in a decrease in the blow-molded container's ability to stand on its own.

For this reason, it is conceivable to prevent a decrease in self-standing ability by making the peripheral edge of the bottom of a blow-molded container into an arc shape with a small radius of curvature in vertical cross section. However, with such blow-molded containers, there is a problem in that the buckling strength against a compressive load applied in a direction perpendicular to the bottom decreases between the body and the bottom.

Japanese Patent Application Laid-Open No. 2021-37975

The present invention was developed in consideration of the above-mentioned problems, and its purpose is to provide a blow-molded container that can reduce buckling deformation by improving the buckling strength between the body and bottom when subjected to a compressive load in a direction perpendicular to the bottom.

In order to solve the above-mentioned problems, the blow-molded container of the present invention is a blow-molded container having a hollow, bottomed cylinder, and has a mouth, a cylindrical body connected to the lower part of the mouth, a strength reinforcement connected to the lower part of the body and curved convexly outward from the container, and a bottom connected to the strength reinforcement, and the outer wall surface of the body is erected perpendicular to the bottom at least at the lower end of the body, and the outer curved surface of the strength reinforcement is tangent to the outer wall surface of the body, reinforcing the buckling strength between the body and the bottom.

The above-described configuration includes a strength reinforcement section that extends from the body to the bottom and is curved convexly outward from the container. The outer wall surface of the body is erected perpendicular to the bottom at least at its lower end, and the outer curved surface of the strength reinforcement section is tangent to and continues from this outer wall surface. This improves the buckling strength between the body and bottom in a blow-molded container with the above-described configuration, and prevents or reduces buckling (shape) deformation between the body and bottom even when a compressive load is applied perpendicular to the bottom.

In the above configuration, it is preferable that the bottom portion has a flat contact surface on its outer periphery, and that the outer curved surface of the strength reinforcement portion is tangent to the contact surface. When the bottom portion has a flat contact surface on its outer periphery, making the outer curved surface of the strength reinforcement portion tangent to the contact surface can further improve the buckling strength between the body portion and the bottom portion against a compressive load in a direction perpendicular to the bottom portion.

In the above configuration, the strength reinforcement portion is formed by connecting multiple curved portions with different radii of curvature in a longitudinal cross section of the blow-molded container in a direction perpendicular to the bottom, and the radius of curvature of the curved portion with an outer curved surface tangent to the outer wall surface may be larger than the radius of curvature of the curved portion with an outer curved surface tangent to the ground surface.

Furthermore, in the above configuration, the strength reinforcement portion may consist of a single curved portion having an arbitrary radius of curvature in a vertical cross section of the blow-molded container in a direction perpendicular to the bottom portion.

In the above configuration, it is preferable that the ratio of the diameter of the outer contour line of the contact surface to the diameter of the outer wall surface be 50% or more and 90% or less. By making the diameter ratio 50% or more, it is possible to prevent the contact area of the contact surface from becoming excessively small when the blow-molded container is placed on a horizontal surface, and to maintain good self-standing of the blow-molded container. On the other hand, by making the diameter ratio 90% or less, it is possible to form a strength reinforcement section that can impart good buckling strength.

The present invention provides a blow-molded container with improved buckling strength between the body and bottom against a compressive load applied in a direction perpendicular to the bottom.

1 is a front view illustrating a blow-molded container according to a first embodiment of the present invention. 1 is an enlarged cross-sectional view showing a main part of a blow-molded container according to a first embodiment. FIG. FIG. 2 is a bottom view of the blow-molded container according to the first embodiment. FIG. 10 is a front view illustrating a blow-molded container according to a second embodiment of the present invention. FIG. 10 is an enlarged cross-sectional view showing a main part of a blow-molded container according to a second embodiment. FIG. 2 is an explanatory diagram showing the von Mises stress distribution related to the buckling strength of the blow-molded container according to Example 1. FIG. 10 is an explanatory diagram showing the Mises stress distribution related to the buckling strength of the blow-molded container according to Comparative Example 1. FIG. 10 is an explanatory diagram showing the von Mises stress distribution related to the buckling strength of the blow-molded container according to Example 2. FIG. 10 is an explanatory diagram showing the von Mises stress distribution related to the buckling strength of the blow-molded container according to Example 3. FIG. 10 is an explanatory diagram showing the von Mises stress distribution related to the buckling strength of the blow-molded container according to Comparative Example 2. FIG. 10 is an explanatory diagram showing the von Mises stress distribution related to the buckling strength of the blow-molded container according to Example 4. FIG. 10 is an explanatory diagram showing the von Mises stress distribution related to the buckling strength of the blow-molded container according to Example 5. FIG. 10 is an explanatory diagram showing the von Mises stress distribution related to the buckling strength of the blow-molded container according to Example 6. FIG. 10 is an explanatory diagram showing the von Mises stress distribution related to the buckling strength of the blow-molded container according to Comparative Example 3.

(Embodiment 1)
A blow-molded container according to the first embodiment will be described below with reference to Figures 1 to 3. However, parts unnecessary for the description are omitted, and some parts are illustrated enlarged or reduced to facilitate the description. Figure 1 is a front view of a blow-molded container according to the present embodiment. Figure 2 is an enlarged cross-sectional view showing a main part of the blow-molded container. Figure 3 is a bottom view of the blow-molded container.

As shown in Figure 1, the blow-molded container 1 according to this embodiment is a cylindrical container having a spout 11 for pouring liquid, a shoulder 12 extending below the spout 11, a cylindrical body 13 extending below the shoulder 12, a strength reinforcement portion 14, and a bottom 15. The blow-molded container 1 has a storage space therein capable of containing various contents. Note that the axis O shown in Figure 1 represents the central axis of the blow-molded container 1.

The mouth 11 is open at the upper end and has a generally circular opening shape in a plan view. The lower end of the mouth 11 is connected to a shoulder 12. The outer surface of the mouth 11 may be provided with, for example, a male thread that allows it to be threadedly engaged with a lid. This allows the mouth 11 to be closed by the lid. Note that the shape of the mouth 11 is not limited to this, and any known structure can be used in the present invention.

The shoulder 12 extends from the lower end of the mouth 11 to the upper end of the body 13. The shoulder 12 has a shape in which the diameter in a cross section (transverse cross section) perpendicular to the axis O increases from the lower end of the mouth 11 to the upper end of the body 13.

The body 13 has a cylindrical shape and extends from the lower end of the shoulder 12 to the upper end of the strength reinforcement 14. The outer and inner diameters of the cross section of the body 13 are formed to be approximately the same from the lower end of the shoulder 12 to the upper end of the strength reinforcement 14. The outer wall surface 13b of the body 13 is formed to stand approximately perpendicular to the bottom 15.

The present invention is not particularly limited as long as the outer wall surface 13b of the body 13 is erected perpendicular to the bottom 15 at least at the lower end 13a. Therefore, for example, the outer diameter in a cross section of the body 13 may be shaped to decrease or increase from the lower end of the shoulder 12 toward the upper end of the strength reinforcement 14, excluding the lower end 13a. Alternatively, the outer diameter may be shaped to decrease or increase from the lower end of the shoulder 12 and the upper end of the strength reinforcement 14 toward the center of the body 13, excluding the lower end 13a.

The strength reinforcing portion 14 functions to reinforce the buckling strength between the body portion 13 and the bottom portion 15. Here, in this specification, "buckling (deformation)" means that when a compressive load is applied to the blow-molded container 1 in its axial direction (a direction perpendicular to the bottom portion 15), the blow-molded container 1 will collapse or be crushed due to buckling deformation (plastic deformation). Furthermore, "buckling strength" refers to the limit compressive load at which the blow-molded container 1 will buckle (deform) when a compressive load is applied to the blow-molded container 1 in the axial direction, and can also be referred to as axial compressive strength.

2, the strength reinforcement portion 14 extends from the lower end 13a of the body portion 13 to the ground contact portion 15a of the bottom portion 15, and consists of a single curved portion with an arbitrary radius of curvature R1. Furthermore, the outer curved surface 14a of the strength reinforcement portion 14 is tangent to the outer wall surface 13b of the body portion 13 and the ground contact surface 15c of the bottom portion 15 (details will be described later). By providing the strength reinforcement portion 14 tangent to the outer wall surface 13b of the body portion 13 and the ground contact surface 15c of the bottom portion 15, respectively, buckling strength can be improved. In this specification, "tangent" refers to a state in which, in a vertical cross section of the blow-molded container 1 taken in a direction perpendicular to the bottom portion 15, the tangents of the outer wall surface 13b of the body portion 13 and the outer curved surface 14a of the strength reinforcement portion 14 coincide at the first connection portion 17. Furthermore, this means that the tangents of the outer curved surface 14a of the strength reinforcement portion 14 and the ground contact surface 15c of the bottom portion 15 coincide at the second connection portion 18 in the cross-sectional view.

The radius of curvature R1 of the strength reinforcement portion 14 can be set as appropriate, but by increasing the value of the radius of curvature R1, it is possible to improve the adhesion of the parison to the shape inside the mold when blowing it to produce the blow-molded container 1 by blow molding. As a result, the moldability of the blow-molded container 1 is improved. The radius of curvature R1 is preferably set to satisfy the following formula. In addition, in this embodiment, the height h of the strength reinforcement portion 14 is equal to the radius of curvature R1.
R1 (mm) = (D1 (mm) - D2 (mm))/2
(In the formula, D1 represents the outer diameter of the lower end 13a (outer wall surface 13b) of the body 13, and D2 represents the diameter of the outer contour line of the contact surface 15c.)

The bottom portion 15 has a generally circular outer shape when viewed from the bottom. As shown in Figures 2 and 3, the bottom portion 15 has a grounding portion 15a that contacts the horizontal surface and a non-grounding portion 15b located inside the grounding portion 15a.

The grounding portion 15a extends along the outer peripheral edge of the bottom portion 15. The grounding portion 15a also has an annular grounding surface 15c that contacts the horizontal surface when the blow-molded container 1 is placed upright on the horizontal surface. The area where the grounding surface 15c is formed can be set as appropriate as long as it does not impair the ability of the blow-molded container 1 to stand on its own.

The non-ground contact portion 15b has a flat surface 15d formed by depressing the bottom 15 toward the inside of the container (the interior of the blow-molded container 1), and an inclined surface 15e that connects the ground contact surface 15c to the flat surface 15d. As shown in Figure 3, the flat surface 15d is approximately circular in bottom view. Furthermore, the flat surface 15d is located higher than the ground contact surface 15c, so that it does not come into contact with the horizontal surface when the blow-molded container 1 is placed on the horizontal surface. Furthermore, the inclined surface 15e is annular in bottom view. The inclination angle of the inclined surface 15e in a vertical cross section is not particularly limited and can be set appropriately depending on the height position of the flat surface 15d relative to the ground contact surface 15c, the area of the flat surface 15d, etc.

The difference in height d between the contact surface 15c and the flat surface 15d (or the height of the flat surface 15d relative to the horizontal plane) is not particularly limited, but can be set, for example, in the range of 2 mm to 4 mm. In this case, by setting d to 4 mm or less, it is possible to reduce or prevent scratches on the blow-molded container 1 when, for example, releasing the blow-molded container 1 from the mold during blow molding. Furthermore, by setting d to 2 mm or more, it is possible to maintain the self-standing ability of the blow-molded container 1 even if the bottom 15 bulges and deforms.

In this embodiment, the ground contact portion 15a is not particularly limited as long as the outer contour of the ground contact surface 15c (the boundary line between the ground contact surface 15c and the outer curved surface 14a of the strength reinforcement portion 14) is approximately circular. For example, the ground contact surface 15c may have recesses that do not come into contact with the horizontal surface at two locations located on an extension of the parting line PL of the bottom 15. Furthermore, the non-ground contact portion 15b may be rectangular in bottom view. In this case, the inner contour of the ground contact surface 15c will be rectangular corresponding to the shape of the non-ground contact portion 15b. Furthermore, the entire bottom 15 may be a ground contact surface.

Furthermore, the ratio of the diameter D1 of the outer wall surface 13b of the body 13 to the outer contour line D2 of the contact surface 15c is preferably 50% or more and 90% or less, more preferably 60% or more and 90% or less, and particularly preferably 70% or more and 80% or less. Setting this diameter ratio to 50% or more prevents the contact area of the contact surface 15c from becoming excessively small when the blow-molded container 1 is placed on a horizontal surface, thereby maintaining good self-supporting ability of the blow-molded container 1. On the other hand, setting this diameter ratio to 90% or less makes it possible to form a strength reinforcement portion 14 between the body 13 and the bottom 15.

Furthermore, the overall height H of the blow-molded container 1 is not particularly limited and can be set as appropriate. The thicknesses of the mouth portion 11, shoulder portion 12, body portion 13, strength reinforcement portion 14, and bottom portion 15 are also not particularly limited and can be set as appropriate and necessary. The thicknesses of each portion may be the same or different.

The material of the blow-molded container 1 is not particularly limited, and known resin materials such as high-density polyethylene (HDPE), polypropylene (PP), and polyethylene terephthalate (PET) can be used.

The blow-molded container 1 according to this embodiment can be manufactured using known blow molding methods, such as extrusion blow molding, injection blow molding, and stretch blow molding.

(Embodiment 2)
A blow-molded container according to embodiment 2 will be described below with reference to Figures 4 and 5. Figure 4 is a front view of the blow-molded container according to this embodiment. Figure 5 is an enlarged cross-sectional view of a main part of the blow-molded container according to this embodiment. In the blow-molded container according to embodiment 2, components that have the same configuration as the blow-molded container 1 according to embodiment 1 are given the same reference numerals and their description will be omitted.

As shown in Figures 4 and 5, the blow-molded container 2 according to this embodiment differs from the blow-molded container 1 according to embodiment 1 in that the strength reinforcement portion 24 is formed by connecting a first curved portion 24a and a second curved portion 24b, each having a different radius of curvature. Even with this structure, the buckling strength between the body portion 13 and the bottom portion 15 can be improved against a compressive load applied perpendicular to the bottom portion 15.

As shown in FIG. 5, the first curved portion 24a of the strength reinforcement portion 24 continues from the lower end portion 13a of the body portion 13 to the second curved portion 24b and has a radius of curvature R2. Furthermore, the first outer curved surface 24c is tangent to the outer wall surface 13b of the body portion 13. The second curved portion 24b of the strength reinforcement portion 24 continues from the first curved portion 24a to the bottom portion 15 and has a radius of curvature R3. Furthermore, the second outer curved surface 24d is tangent to the contact surface 15c of the bottom portion 15. The present invention is not particularly limited as long as the radius of curvature R2 of the first curved portion 24a and the radius of curvature R3 of the second curved portion 24b are set so that R2 is greater than R3.

The difference in height between the contact surface 15c and the flat surface 15d (or the height of the flat surface 15d relative to the horizontal plane) d, and the ratio of the diameter D2 of the outer contour line of the contact surface 15c to the diameter D1 of the outer wall surface 13b of the body 13 are the same as in embodiment 1. Therefore, detailed description thereof will be omitted.

(Other matters)
In the above-described embodiments, the outer curved surface of the strength reinforcement is tangent to the outer wall surface of the body and also to the contact surface of the bottom. However, the present invention is not limited to this configuration. For example, the outer curved surface of the strength reinforcement may be tangent only to the outer wall surface of the body. Even in this configuration, the present invention can improve the buckling strength between the body and the bottom against a compressive load in a direction perpendicular to the bottom.

Furthermore, in each embodiment, the strength reinforcement portion has been described as consisting of one curved portion or two curved portions with different radii of curvature. However, the strength reinforcement portion of the present invention is not limited to the form of each embodiment, as long as it connects from the lower portion of the body to the bottom and has a shape that is convexly curved outward from the container. For example, the strength reinforcement portion may have three or more curved portions.

The following provides a detailed description of preferred embodiments of the present invention. However, unless otherwise specified, the materials, compounding amounts, etc. described in these embodiments are not intended to limit the scope of the present invention to those materials alone.

Example 1
In this example, high-density polyethylene (HDPE) was used as the constituent material, and a blow-molded container as shown in Figure 6(a) was produced by extrusion blow molding. Specifically, a molten tubular parison made of HDPE was fed into a mold, and the parison was pinched off and fused between the molds. Compressed gas was then blown into the parison to expand it into the shape of a container. During blow molding, the parison's surface temperature was 170°C, the pressure was 0.6 MPa, and the blow molding time was 10 seconds. After cooling, the mold was opened, and the blow-molded container was removed. As shown in Figure 6, the resulting blow-molded container had a strength reinforcement portion consisting of a single curved portion, and the outer curved surface of the curved portion was tangent to both the outer wall surface of the body and the contact surface of the bottom. The shape and dimensions of the blow-molded container are shown below.
Overall height of blow molded container H: 225 mm
Thickness of blow molded container: 1 mm
Outer diameter D1 of the body (outer wall): φ100 mm
Diameter D2 of the outer contour of the ground contact surface: φ50 mm
Curvature radius R1 of curved part: 25 mm
Height of reinforced part h: 25 mm

(Comparative Example 1)
In this comparative example, the outer curved surface of the curved portion was made tangent only to the bottom contact surface, and the shape and dimensions were changed as follows: A blow-molded container according to this comparative example was produced in the same manner as in Example 1 (see FIG. 7).
Blow molded container height H: 225 mm
Thickness of blow molded container: 1 mm
Outer diameter D1 of the body (outer wall): φ100 mm
Diameter D2 of the outer contour of the ground contact surface: φ51.35 mm
Curvature radius R1 of curved part: 25 mm
Height of the strength reinforcement part h: 20 mm

Example 2
In this example, the shape and dimensions were changed as follows: A blow-molded container according to this example was produced in the same manner as in Example 1 (see FIG. 8).
Blow molded container height H: 225 mm
Thickness of blow molded container: 1 mm
Outer diameter D1 of the body (outer wall): φ100 mm
Diameter D2 of the outer contour of the ground contact surface: φ90 mm
Curvature radius R1 of curved part: 5 mm
Height of the strength reinforcement part h: 5 mm

Example 3
In this example, the outer curved surface of the curved portion was made tangent only to the outer wall surface of the body portion, and the shape and dimensions were changed as follows: A blow-molded container according to this example was produced in the same manner as in Example 1 (see FIG. 9 ).
Blow molded container height H: 225 mm
Thickness of blow molded container: 1 mm
Outer diameter D1 of the body (outer wall): φ100 mm
Diameter D2 of the outer contour of the ground contact surface: φ52.61 mm
Curvature radius R1 of curved part: 64.6 mm
Height of the strength reinforcement part h: 50 mm

(Comparative Example 2)
In this comparative example, the outer curved surface of the curved portion was not tangent to either the outer wall surface of the body or the contact surface of the bottom, and the shape and dimensions were changed as follows: A blow-molded container according to this comparative example was produced in the same manner as in Example 1 (see FIG. 10 ).
Blow molded container height H: 225 mm
Thickness of blow molded container: 1 mm
Outer diameter D1 of the body (outer wall): φ100 mm
Diameter D2 of the outer contour of the ground contact surface: φ54.97 mm
Curvature radius R1 of curved part: 64.6 mm
Height of the strength reinforcement part h: 25 mm

Example 4
In this example, the outer curved surface of the curved portion was made tangent only to the outer wall surface of the body portion, and the shape and dimensions were changed as follows: A blow-molded container according to this example was produced in the same manner as in Example 1 (see FIG. 11 ).
Blow molded container height H: 225 mm
Thickness of blow molded container: 1 mm
Outer diameter D1 of the body (outer wall): φ100 mm
Diameter D2 of the outer contour of the ground contact surface: φ90.28 mm
Curvature radius R1 of curved portion: 259.75 mm
Height of the strength reinforcement part h: 50 mm

Example 5
In this example, a blow-molded container was produced in which a first curved portion and a second curved portion were formed as a strength reinforcement portion. That is, the strength reinforcement portion was formed so that the first outer curved surface of the first curved portion continued from the body portion to the second curved portion, and the second outer curved surface of the second curved portion continued from the first curved portion to the contact surface of the bottom. Furthermore, the first outer curved surface was tangent to the outer wall surface of the body portion, and the second outer curved surface was tangent to the contact surface of the bottom portion. Other than these, the blow-molded container of this example was produced in the same manner as in Example 1 (see FIG. 12 ). The shape and dimensions of the blow-molded container of this example are shown below.
Blow molded container height H: 225 mm
Thickness of blow molded container: 1 mm
Outer diameter D1 of the body (outer wall): φ100 mm
Diameter D2 of the outer contour of the ground contact surface: φ48.96 mm
Radius of curvature R2 of the first curved portion: 64.6 mm
Radius of curvature of second curved portion R3: 5 mm
Height of the strength reinforcement part h: 50 mm

Example 6
In this example, the shape and dimensions were changed as follows: A blow-molded container according to this example was produced in the same manner as in Example 5 (see FIG. 13).
Blow molded container height H: 225 mm
Thickness of blow molded container: 1 mm
Outer diameter D1 of the body (outer wall): φ100 mm
Diameter D2 of the outer contour of the ground contact surface: φ81.99 mm
Radius of curvature R2 of the first curved portion: 259.75 mm
Radius of curvature of second curved portion R3: 5 mm
Height of the strength reinforcement part h: 50 mm

(Comparative Example 3)
In this comparative example, only the second outer curved surface of the second curved portion was tangent to the contact surface of the bottom, and the shape and dimensions were changed as follows: A blow-molded container according to this comparative example was produced in the same manner as in Example 5 (see FIG. 14 ).
Blow molded container height H: 225 mm
Thickness of blow molded container: 1 mm
Outer diameter D1 of the body (outer wall): φ100 mm
Diameter D2 of the outer contour of the ground contact surface: φ88.43 mm
Radius of curvature R2 of the first curved portion: 259.75 mm
Radius of curvature of second curved portion R3: 5 mm
Height of reinforced part h: 35 mm

(Buckling strength test)
A buckling strength analysis was performed on the 3D-CAD models (models created using software named SolidWorks, manufactured by Dassault Systèmes) corresponding to the blow-molded containers of each Example and Comparative Example using the strength analysis simulation SimulationXpress analysis wizard, and the degree of buckling deformation was confirmed.

Specifically, a strength analysis simulation was performed on the 3D-CAD model of each blow-molded container, with a compressive load of 100 N applied perpendicularly to the bottom of each blow-molded container. The application of the compressive load also fixed the mouth and shoulder of each blow-molded container so that they would not buckle. The resin materials and their physical properties for each blow-molded container were as follows:
Resin material type: High density polyethylene (HDPE)
Elastic modulus: 1.07 x ¹⁰⁹ N/ ^m2
Poisson's ratio: 0.4101
Shear modulus: 3.772 x ¹⁰⁸ N/ ^m2
Mass density: 952kg/ ^m3
Tensile strength: 2.21 x ¹⁰⁷ N/ ^m2
Thermal conductivity: 0.461 W/(m·K)
Specific heat: 1796 J/(kg K)
The simulation results were expressed as a von Mises stress distribution for the stress generated in each blow-molded container, and are shown in Figures 6 to 14, respectively.

The simulation results confirmed that in the blow-molded containers of Examples 1 to 6, the buckling strength between the body and bottom was improved by making the outer curved surface of the strength reinforcement tangent to both the outer wall surface of the body or the outer wall surface of the body and the contact surface of the bottom (Figures 6, 8, 9, and 11 to 13). In particular, in the blow-molded containers of Comparative Examples 1 to 3, the buckling (shape) deformation caused by the compressive load extended to the body side in addition to the bottom, whereas in the blow-molded containers of Examples 1, 3, and 6, the buckling deformation caused by the compressive load was limited to the bottom side, confirming improved buckling strength.

1, 2 Blow molded container 11 Mouth part 12 Shoulder part 13 Body part 13a Lower end part 13b Outer wall surface 14 Reinforcement part 14a Outer curved surface 15 Bottom part 15a Ground contact part 15b Non-contact part 15c Contact surface 15d Flat surface 15e Slope surface 17 First connection part 18 Second connection part 24 Strength reinforcement part 24a First curved portion 24b Second curved portion 24c First outer curved surface 24d Second outer curved surface

Claims (5)

A blow-molded container having a hollow, bottomed cylindrical body,
The mouth portion and
a cylindrical body portion connected to a lower portion of the mouth portion;
a strength reinforcing portion that is connected to the lower portion of the body portion and curved convexly outward from the container;
a bottom portion connected to the strength reinforcing portion and having a flat ground contact surface on an outer circumferential edge ,
the outer wall surface of the body portion is erected in a direction perpendicular to the bottom portion at least at a lower end portion of the body portion,
The strength reinforcing portion is
In a longitudinal section of the blow-molded container in a direction perpendicular to the bottom, the blow-molded container has one curved portion having an arbitrary radius of curvature,
an outer curved surface of the strength reinforcement portion is tangent to the outer wall surface of the body portion and the ground surface ;
The radius of curvature R1 of the strength reinforcing portion satisfies the following relational expression:
A blow-molded container that reinforces the buckling strength between the body and the base.
R1 (mm) = (D1 (mm) - D2 (mm))/2
(where D1 represents the outer diameter of the lower end of the body, and D2 represents the diameter of the outer contour of the contact patch.) A blow-molded container having a hollow, bottomed cylindrical body,
A mouth portion and
a cylindrical body portion connected to a lower portion of the mouth portion;
a strength reinforcing portion that is connected to the lower portion of the body portion and curved convexly outward from the container;
a bottom portion connected to the strength reinforcing portion and having a flat ground contact surface on an outer circumferential edge,
the outer wall surface of the body portion is erected in a direction perpendicular to the bottom portion at least at a lower end portion of the body portion,
The strength reinforcing portion is
a first curved portion and a second curved portion having mutually different radii of curvature are provided in series in a longitudinal section of the blow-molded container in a direction perpendicular to the bottom,
an outer curved surface of the first curved portion is tangent to the outer wall surface of the body portion, and an outer curved surface of the second curved portion is tangent to the ground surface;
The radius of curvature of the first curved portion is larger than the radius of curvature of the second curved portion,
A blow-molded container that reinforces the buckling strength between the body and the base. 3. The blow-molded container according to claim 1, wherein the ratio of the diameter of the outer contour line of the contact surface to the diameter of the outer wall surface is 50% or more and 90% or less. the bottom portion has a non-grounded portion inside the grounded surface,
The blow-molded container according to any one of claims 1 to 3, wherein the non-ground contact portion has an inclined surface that is continuous with the ground contact surface, and a flat surface that is continuous with the inclined surface and is located at a height higher than the ground contact surface. 5. The blow-molded container according to claim 4, wherein the difference in height between the contact surface and the flat surface is 2 mm or more and 4 mm or less.