Blow Molded Containers

Abstract

To provide a blow-molded container that can reduce buckling deformation by improving buckling strength between its body part and bottom part against the compressive load in the direction perpendicular to the bottom part.SOLUTION: A blow-molded container 1 of the present invention has a mouth part 11, a cylindrical body part 13 connected to the lower part of the mouth part 11, a strength reinforcing part 14 extending downward from the body part 13 and convexly curved outward from the container and a bottom part 15 connected to the strength reinforcing part 14. An outer wall surface 13a at the lower end of the body part 13 is erected in a direction perpendicular to the bottom part 15, and an outer curved surface 14a of the strength reinforcing part 14 is in tangential contact with the outer wall surface 13a of the body 13 to reinforce the buckling strength between the body 13 and the bottom part 15.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a blow-molded container having a hollow, bottomed cylindrical body, and more particularly to a blow-molded container having excellent buckling strength against a compressive load in a direction perpendicular to the bottom. [Background technology]

[0002] Blow-molded containers can be produced, for example, by extrusion blow molding, in which an extruded cylindrical parison is blow-molded (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 the blow-molded container is placed on a horizontal surface, the contact area of ​​the bottom becomes smaller, which reduces the self-standing ability of the blow-molded container.

[0003] To address this issue, it is conceivable to prevent the deterioration of self-standing ability by forming the peripheral edge of the bottom of the blow-molded container into an arc shape with a small radius of curvature in the longitudinal cross section. However, such a blow-molded container has a problem in that the buckling strength against a compressive load applied in a direction perpendicular to the bottom is reduced between the body and the bottom. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-37975 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a blow-molded container that can reduce buckling deformation by improving the buckling strength between the body and the bottom against a compressive load in a direction perpendicular to the bottom. [Means for solving the problem]

[0006] 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 part connected to the lower part of the body and curved convexly outward from the container, and a bottom connected to the strength reinforcement part, wherein 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 part is tangent to the outer wall surface of the body, reinforcing the buckling strength between the body and the bottom.

[0007] The above-described configuration includes a strength reinforcement portion 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 portion is tangent to and continuous with this outer wall surface. This improves the buckling strength between the body and the bottom in a blow-molded container, and prevents or reduces buckling (shape) deformation between the body and the bottom even when a compressive load is applied perpendicular to the bottom.

[0008] In the above configuration, it is preferable that the bottom portion has a flat ground contact surface on its outer periphery, and the outer curved surface of the strength reinforcement portion is tangent to the ground contact surface. When the bottom portion has a flat ground contact surface on its outer periphery, making the outer curved surface of the strength reinforcement portion tangent to the ground 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.

[0009] In the above configuration, the strength reinforcement portion is formed by connecting a plurality of curved portions having 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 having an outer curved surface tangent to the outer wall surface may be larger than the radius of curvature of the curved portion having an outer curved surface tangent to the contact surface.

[0010] In the above configuration, the strength reinforcing 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.

[0011] 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 is 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-supporting ability 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 portion that can impart good buckling strength. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a blow-molded container having improved buckling strength between the body and the bottom against a compressive load in a direction perpendicular to the bottom. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a front view showing a blow-molded container according to a first embodiment of the present invention. [Figure 2] 1 is an enlarged cross-sectional view showing a main part of a blow-molded container according to a first embodiment. [Figure 3] FIG. 2 is a bottom view of the blow-molded container according to the first embodiment. [Figure 4] FIG. 10 is a front view illustrating a blow-molded container according to a second embodiment of the present invention. [Figure 5]FIG. 10 is an enlarged cross-sectional view showing a main part of a blow-molded container according to a second embodiment. [Figure 6] FIG. 3 is an explanatory diagram showing the Mises stress distribution related to the buckling strength of the blow-molded container according to Example 1. [Figure 7] 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. [Figure 8] FIG. 10 is an explanatory diagram showing the Mises stress distribution related to the buckling strength of the blow-molded container according to Example 2. [Figure 9] FIG. 10 is an explanatory diagram showing the Mises stress distribution related to the buckling strength of the blow-molded container according to Example 3. [Figure 10] 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 2. [Figure 11] FIG. 10 is an explanatory diagram showing the Mises stress distribution related to the buckling strength of the blow-molded container according to Example 4. [Figure 12] FIG. 10 is an explanatory diagram showing the Mises stress distribution related to the buckling strength of the blow-molded container according to Example 5. [Figure 13] FIG. 10 is an explanatory diagram showing the Mises stress distribution related to the buckling strength of the blow-molded container according to Example 6. [Figure 14] 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 3. DETAILED DESCRIPTION OF THE INVENTION

[0014] (Embodiment 1) A blow-molded container according to the first embodiment will be described below with reference to Figs. 1 to 3. However, parts unnecessary for the description are omitted, and some parts are illustrated enlarged or reduced to facilitate the description. Fig. 1 is a front view of a blow-molded container according to the present embodiment. Fig. 2 is an enlarged cross-sectional view showing a main part of the blow-molded container. Fig. 3 is a bottom view of the blow-molded container.

[0015] As shown in Fig. 1, the blow-molded container 1 according to this embodiment is a cylindrical container having a mouth 11 as a spout for pouring liquid, a shoulder 12 connected below the mouth 11, a cylindrical body 13 connected below the shoulder 12, a strength reinforcing portion 14, and a bottom 15. The blow-molded container 1 has an internal storage space capable of storing various contents. Note that the axis O shown in Fig. 1 represents the central axis of the blow-molded container 1.

[0016] The mouth 11 is open at the upper end and has a substantially circular opening shape in a plan view. The lower end of the mouth 11 is connected to a shoulder 12. The outer peripheral surface of the mouth 11 may be provided with, for example, a male thread that allows it to be screwed onto a lid. This makes it possible to close the mouth 11 with the lid. Note that the shape of the mouth 11 is not limited to this, and any known structure can be adopted in the present invention.

[0017] The shoulder portion 12 continues from the lower end of the mouth portion 11 to the upper end of the body portion 13. The shoulder portion 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 portion 11 toward the upper end of the body portion 13.

[0018] The body 13 has a cylindrical shape and continues from the lower end of the shoulder 12 to the upper end of the strength reinforcement 14. The outer diameter and inner diameter in 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 in a direction approximately perpendicular to the bottom 15.

[0019] 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 the cross section of the body 13 may be shaped so that it decreases or increases from the lower end of the shoulder 12 to the upper end of the strength reinforcement 14, excluding the lower end 13a. Alternatively, the outer diameter may be shaped so that it decreases or increases from the lower end of the shoulder 12 and the upper end of the strength reinforcement 14 to the center of the body 13, excluding the lower end 13a.

[0020] The strength reinforcing portion 14 functions to reinforce the buckling strength between the body portion 13 and the bottom portion 15. 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" means 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.

[0021] 2, the strength reinforcement portion 14 is continuous from the lower end portion 13a of the body portion 13 to the contact portion 15a of the bottom portion 15 and is composed of a single curved portion having 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 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 contact surface 15c of the bottom portion 15, respectively, the buckling strength can be improved. In this specification, the term "tangent" means that, in the vertical cross section of the blow-molded container 1 taken in a direction perpendicular to the bottom portion 15, the tangents to 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 connecting portion 17. Furthermore, it means that the tangents of the outer curved surface 14a of the strength reinforcing portion 14 and the ground contact surface 15c of the bottom portion 15 coincide at the second connecting portion 18 in the cross-sectional view.

[0022] 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.)

[0023] The bottom portion 15 has a substantially 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 a horizontal surface and a non-grounding portion 15b that is provided inside the grounding portion 15a.

[0024] 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 appropriately within a range that does not impair the ability of the blow-molded container 1 to stand on its own.

[0025] The non-grounding portion 15b has a flat surface 15d formed by depressing the bottom 15 toward the inside of the container (the interior side of the blow-molded container 1), and an inclined surface 15e continuing from the grounding surface 15c to the flat surface 15d. As shown in FIG. 3, the flat surface 15d is substantially circular in bottom view. The flat surface 15d is located higher than the grounding 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. 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 grounding surface 15c, the area of ​​the flat surface 15d, and the like.

[0026] 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, the blow-molded container 1 is released from the mold during blow molding. Furthermore, by setting d to 2 mm or more, it is possible to favorably maintain the self-standing ability of the blow-molded container 1 even if the bottom 15 bulges and deforms.

[0027] In this embodiment, the ground contact portion 15a is not particularly limited as long as the outer contour line 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 substantially circular. For example, the ground contact surface 15c may have recesses that do not come into contact with a 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 line of the ground contact surface 15c will be rectangular corresponding to the shape of the non-ground contact portion 15b. Furthermore, the entire surface of the bottom 15 may be the ground contact surface.

[0028] Furthermore, the ratio of the diameter D1 of the outer wall surface 13b of the body 13 to the diameter of 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. By making the diameter ratio 50% or more, it is possible to prevent the contact area of ​​the contact surface 15c from becoming excessively small when the blow-molded container 1 is placed on a horizontal surface, and to maintain good self-supporting ability of the blow-molded container 1. On the other hand, by making the diameter ratio 90% or less, it is possible to form a strength reinforcing portion 14 between the body 13 and the bottom 15.

[0029] 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 as needed. The thicknesses of the various portions may be the same or different.

[0030] 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.

[0031] The blow-molded container 1 according to this embodiment can be manufactured by a known blow molding method such as extrusion blow molding, injection blow molding, or stretch blow molding.

[0032] (Embodiment 2) A blow-molded container according to embodiment 2 will be described below with reference to Figs. 4 and 5. Fig. 4 is a front view of the blow-molded container according to this embodiment. Fig. 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.

[0033] 4 and 5, the blow-molded container 2 according to this embodiment differs from the blow-molded container 1 according to the first embodiment in that the strength-reinforcing portion 24 is configured by connecting a first curved portion 24a and a second curved portion 24b having different radii of curvature. Even with this structure, the buckling strength between the body portion 13 and the bottom portion 15 against a compressive load in the direction perpendicular to the bottom portion 15 can be improved.

[0034] 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. Furthermore, 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. Here, 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.

[0035] 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 trunk portion 13 are the same as those in the first embodiment, and therefore detailed description thereof will be omitted.

[0036] (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.

[0037] In addition, 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 part of the body portion to the bottom portion 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. [Example]

[0038] Preferred examples of the present invention are described in detail below. However, the materials and blending amounts described in the examples are not intended to limit the scope of the present invention unless otherwise specified.

[0039] 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 the container. The parison's surface temperature during blow molding 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. The resulting blow-molded container had a strength reinforcement consisting of a single curved portion, as shown in Figure 6, and the outer curved surface of the curved portion was tangent to both the outer wall surface of the body and the base surface. The dimensions of the blow-molded container are shown below. Overall height of blow molded container: H: 225mm Blow molded container thickness: 1mm Outer diameter of the body (outer wall): D1: φ100 mm Diameter of outer contour of ground contact surface D2: φ50mm Curvature radius of curved part R1: 25mm Height of reinforced part h: 25mm

[0040] (Comparative Example 1) In this comparative example, the outer curved surface of the curved portion was made tangent only 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 1 (see FIG. 7). Blow molded container height: 225mm Blow molded container thickness: 1mm Outer diameter of the body (outer wall): D1: φ100 mm Diameter of outer contour of contact surface D2: φ51.35mm Curvature radius of curved part R1: 25mm Height of reinforced part h: 20mm

[0041] 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: 225mm Blow molded container thickness: 1mm Outer diameter of the body (outer wall): D1: φ100 mm Diameter of outer contour of ground contact surface D2: φ90mm Curvature radius of curved part R1: 5mm Height of reinforced part h: 5mm

[0042] 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: 225mm Blow molded container thickness: 1mm Outer diameter of the body (outer wall): D1: φ100 mm Diameter of outer contour of contact surface D2: φ52.61mm Curvature radius of curved part R1: 64.6 mm Height of reinforced part h: 50mm

[0043] (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: 225mm Blow molded container thickness: 1mm Outer diameter of the body (outer wall): D1: φ100 mm Diameter of outer contour of contact surface D2: φ54.97mm Curvature radius of curved part R1: 64.6 mm Height of reinforced part h: 25mm

[0044] 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: 225mm Blow molded container thickness: 1mm Outer diameter of the body (outer wall): D1: φ100 mm Diameter of outer contour of contact surface D2: φ90.28mm Curvature radius of curved part R1: 259.75 mm Height of reinforced part h: 50mm

[0045] 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-reinforcing portion, with the first outer curved surface of the first curved portion continuing from the body portion to the second curved portion, and the second outer curved surface of the second curved portion continuing 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: 225mm Blow molded container thickness: 1mm Outer diameter of the body (outer wall): D1: φ100 mm Diameter of outer contour of contact surface D2: φ48.96mm Radius of curvature of the first curved part R2: 64.6 mm The radius of curvature of the second curved part is R3: 5 mm Height of reinforced part h: 50mm

[0046] 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: 225mm Blow molded container thickness: 1mm Outer diameter of the body (outer wall): D1: φ100 mm Diameter of outer contour of contact surface D2: φ81.99mm Radius of curvature of the first curved part R2: 259.75 mm The radius of curvature of the second curved part is R3: 5 mm Height of reinforced part h: 50mm

[0047] (Comparative Example 3) In this comparative example, only the second outer curved surface of the second curved portion was made 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: 225mm Blow molded container thickness: 1mm Outer diameter of the body (outer wall): D1: φ100 mm Diameter of outer contour of contact surface D2: φ88.43mm Radius of curvature of the first curved part R2: 259.75 mm The radius of curvature of the second curved part is R3: 5 mm Height of reinforced part h: 35mm

[0048] (Buckling strength test) A buckling strength analysis was performed on 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.

[0049] 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 vertically 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 10 9 N / m 2 Poisson's ratio: 0.4101 Shear modulus: 3.772 x 10 8 N / m 2 Mass density: 952kg / m 3 Tensile strength: 2.21 x 10 7 N / m 2 Thermal conductivity: 0.461 W / (m K) Specific heat: 1796 J / (kg K) The simulation results, in which the stress generated in each blow-molded container was expressed as a von Mises stress distribution, are shown in Figures 6 to 14, respectively.

[0050] The simulation results confirmed that, in the blow-molded containers according to Examples 1 to 6, the buckling strength between the body and the bottom was improved by making the outer curved surface of the strength reinforcement tangent to both the outer wall surface of the body and the contact surface of the bottom (FIGS. 6, 8, 9, and 11 to 13). In particular, in the blow-molded containers according to Comparative Examples 1 to 3, the buckling (shape) deformation caused by the compressive load spread to the body side in addition to the bottom, whereas in the blow-molded containers according to Examples 1, 3, and 6, the buckling deformation caused by the compressive load was limited to the bottom side, confirming improved buckling strength. [Explanation of symbols]

[0051] 1, 2 Blow-molded containers 11 Mouth 12 Shoulder 13 Torso 13a Lower end 13b Outside wall 14 Strength reinforcement section 14a Outer curved surface 15 Bottom 15a Grounding part 15b Non-grounded part 15c ground plane 15d flat surface 15e Slope 17 First connection part 18 Second connection part 24 Strength reinforcement section 24a First curved section 24b Second curved section 24c 1st outer curved surface 24d 2nd outer curved surface

Claims

1. 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 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.)

2. 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. 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.

4. The bottom has a non-grounding portion inside the grounding 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. A blow-molded container as described in claim 4, wherein the difference in height between the ground surface and the flat surface is 2 mm or more and 4 mm or less.

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