ES2960028T3 - Plastic bottle - Google Patents

Abstract

This plastic bottle is provided with recessed sections 422 in a bottom part 4, wherein the recessed sections 422 protrude inwardly from the bottom part 4 towards the interior of the plastic bottle, and have a flat hexagonal recessed shape having four corners. convex, the interior whose angles are acute, and two concave vertices, whose interior angles are greater than 180 degrees and less than 360 degrees, and the two vertices adjacent to a convex vertex comprise a convex vertex and a concave vertex, and the two vertices adjacent to a concave vertex comprise two convex vertices. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Plastic bottle

Technical field

The present invention relates to a plastic bottle including a bottom having at least two rows of depressions, each formed by a plurality of depressions in a row.

Previous technique

Plastic bottles filled with beverages can be deformed in a disadvantageous manner as a result of a change in the internal pressure of the plastic bottles during production and distribution. Examples of a pressure change that can produce such deformation include (i) a change in internal pressure produced by expansion and contraction due to a change in temperature and (ii) the application of a liquid pressure greater than atmospheric pressure when the plastic bottles are filled with drinks. Various efforts have been made to strengthen the bottom of a plastic bottle.

As an example of such efforts, Patent Literature 1 describes a plastic bottle having (i) a recessed portion that is depressed from the bottom surface of the plastic bottle toward the interior of the plastic bottle and (ii) a plurality of substantially spherical ribs that are arranged radially and that are depressed from the most inwardly depressed part of the plastic bottle. Since the plastic bottle has substantially spherical ribs, the bottom is capable of resisting deformation caused by thermal contraction or the self-weight of the contents.

Patent Literature 2 describes a plastic bottle including a bottom portion having a movable wall portion with a plurality of ribs. The plastic bottle is arranged so that the movable wall portion deforms by rapidly responding to a change in the internal pressure of the plastic bottle. This effectively prevents deformation of the remaining parts of the plastic bottle. The plastic bottle is arranged so that the movable wall part, which has a plurality of ribs, is capable of absorbing a change in pressure more effectively. Patent literature 3 describes a plastic bottle according to the preamble of claim 1.

Appointment list

Patent bibliography

Patent Bibliography 1

Japanese Patent Application Pending Examination Publication, Tokukaihei, No. 7-112729

Patent Bibliography 2

International publication No. 2012/43362

Patent Bibliography 3

Document WO 2015/189127 A1

Compendium of the Invention

technical problem

While techniques such as those in Patent Publications 1 and 2 allow a plastic bottle to sufficiently resist deformation resulting from a pressure change spontaneously caused, for example, by a change in temperature or self-weight, the techniques do not allow A plastic bottle sufficiently resists a major pressure change such as a pressure change due to a mechanically applied liquid pressure when the plastic bottle is filled with a beverage. Consequently, a bottle can be deformed so that the bottom is pushed down by internal pressure. This requires that the liquid pressure applied to the beverage during a filling step be limited so that the plastic bottles do not deform. Such a limit may decrease efficiency in beverage production.

The above circumstances have led to the demand for a plastic bottle capable of more effectively resisting deformation resulting from a change in internal pressure.

Solution to the problem

The present invention is defined in the claims. A plastic bottle according to one or more embodiments of the present invention comprises: a bottom provided with at least one depression, wherein at least one depression is in a direction from the bottom towards the interior of the plastic bottle, at least A depression has, in plan view, the shape of a concave hexagon with (i) four acute vertices that have respective interior angles, each of which is acute and (ii) two reentrant vertices that have respective interior angles that are each greater than 180° and less than 360°, the acute vertices are each adjacent to another of the acute vertices and to one of the reentrant vertices, and the reentrant vertices are each adjacent to two of the acute vertices.

With the previous arrangement, the depression is capable of being deformed both by a load along the central axis and by a load perpendicular to the central axis, in such a way that it follows said loads in those directions. This allows an excellent ability to absorb a change in pressure.

The following description deals with preferred embodiments of the present invention. The preferred embodiments described below as examples do not limit the scope of the present invention.

A plastic bottle as a preferred embodiment of the present invention is arranged so that the respective interior angles of the four acute vertices are equal to each other, and the respective interior angles of the two reentrant vertices are equal to each other.

With the previous arrangement, the depression has a flat shape with a high degree of symmetry. This allows the depression to deform with high symmetry when following a load and therefore allows for an improved ability to absorb a pressure change.

A plastic bottle as a preferred embodiment of the present invention is arranged so that at least one depression includes at least one row of depressions formed by a plurality of depressions at the bottom.

With the above arrangement, a plurality of depressions operate together. This allows for an improved ability to absorb a pressure change.

A plastic bottle as a preferred embodiment of the present invention is arranged such that the plurality of depressions in at least one row of depressions are adjacent to each other, such that the respective central axes of the plurality of depressions coincide with each other. , each of the central axes being an extension of a central line of a corresponding one of the plurality of depressions, the central line connecting respective central points of two opposite sides of the corresponding one of the plurality of depressions, each of the central points between two of the acute vertices of the concave hexagon, and at least one row of depressions includes at least two rows of depressions having respective central axes parallel to each other.

With the above arrangement, a plurality of depressions included in a plurality of rows of depressions operate together. This allows for an even improved ability to absorb a pressure change.

A plastic bottle as a preferred embodiment of the present invention is arranged such that at least two rows of depressions include a first row of depressions and a second row of depressions that are adjacent to each other, the first row of depressions and the second row of depressions are offset from each other in one direction along the respective central axes of the first row of depressions and the second row of depressions, the width of the displacement is 40% to 60% of the length of each of the depressions. central lines, and one of the acute vertices, of a first depression included in the first row of depressions and one of the acute vertices of a second depression included in the first row of depressions, which second depression is adjacent to the first depression, being adjacent to each other, are located, in a plan view, outside one of the reentrant vertices of a depression included in the second row of depressions in a pattern such that they fit into said one of the reentrant vertices in the plan view.

With the above arrangement, the adjacent depressions have a mutually fitting arrangement. This reduces the movement of the depressions along the bottom surface and therefore prevents the bottom from warping. As a result, the above arrangement allows the plastic bottle to resist a load that might otherwise cause deformation, and advantageously prevents the entire plastic bottle from being easily deformed.

A plastic bottle as a preferred embodiment of the present invention is arranged so that the respective interior angles of the acute vertices are each greater than 60° and no greater than 80°.

The depression, if it has a flat shape defined by the above range, allows for an improved ability to absorb a change in pressure.

A plastic bottle as a preferred embodiment of the present invention is arranged so that at least one depression has a dimension of 0.5 mm to 2.5 mm in the direction from the bottom towards the inside of the plastic bottle.

The depression, if it has a depth within the above range, allows for an improved ability to absorb a change in pressure.

A plastic bottle as a preferred embodiment of the present invention is arranged so that the concave hexagon has diagonals, the longest of which has a length of 3 mm to 8 mm.

The depression, if it has a flat shape defined by the above range, allows for an improved ability to absorb a change in pressure.

A plastic bottle as a preferred embodiment of the present invention is arranged such that the bottom portion includes a dome portion that sinks into the interior of the plastic bottle as the dome portion extends from a portion of floor of the plastic bottle radially toward the interior of the plastic bottle and at least one depression is in a direction from the dome portion most toward the interior of the plastic bottle.

With the above arrangement, the plastic bottle benefits from both the pressure resistance of the dome part and the ability to absorb pressure changes from the depression. This allows the plastic bottle to resist pressure more effectively.

Additional features and advantages of the present invention will become clearer by describing the following exemplary and non-limiting embodiments, which are described with reference to the drawings.

Brief description of the drawings

Figure 1 is a front view of a plastic bottle.

Figure 2 is a front cross-sectional view of a plastic bottle.

Figure 3 is a cross-sectional view taken along the line MI-MI of Figure 1.

Figure 4 is a cross-sectional view taken along line IV-IV in Figure 1.

Figure 5 is an enlarged front view of a body part of a plastic bottle.

Figure 6 is a cross-sectional view taken along line VI-VI in Figure 5.

Figure 7 is a cross-sectional view taken along line VII-VII of Figure 5.

Figure 8 is a bottom view of a bottom part of a plastic bottle.

Figure 9 is an enlarged view of the bottom depressions in a bottom of a plastic bottle.

Description of realizations

The following description refers to a plastic bottle as an embodiment of the present invention with reference to the drawings. The present embodiment is a plastic bottle 100 including, as illustrated in Fig. 1, (i) a mouth portion 1 as a liquid spout, (ii) a shoulder portion 2 continuous with the mouth portion 1 and having a diameter that gradually increases towards the lower surface, (iii) a body part 3 continuous with the shoulder part 2 and having a cylindrical shape, and (iv) a lower part 4 like the bottom of the bottle of plastic 100. In the following description, the "depth" of a structure on the surface of the plastic bottle 100 means how much the surface of the plastic bottle 100 is recessed inward.

The plastic bottle 100 as the present embodiment can be produced with a thermoplastic resin such as polyethylene, polypropylene or polyethylene terephthalate as the main material and integrally molded by a stretching and molding method such as biaxial stretch blow molding. The 100 plastic bottle can have any capacity. The capacity can be approximately 200 mL to 2 L, such as 280 mL, 350 mL or 500 mL, like that of a common plastic bottle. The 100 plastic bottle can be filled with any liquid. Examples include (i) beverages such as drinking water, tea, fruit juice, coffee, cocoa, soft drinks, alcoholic beverages, dairy drinks and soups and (ii) liquid condiments such as Worcester sauce and soy sauce.

[Ribbing structure]

The body part 3 is provided, in an upper region 3a thereof, with a main circumferential rib 31 in the form of a depression. The body part 3 is also provided, in the upper region 3a and in a lower region 3c thereof, with subcircumferential ribs 32, each in the shape of a depression. As illustrated in Fig. 2, the main circumferential rib 31 has a depth and dimension in the top-to-bottom direction that are greater than those of each subcircumferential rib 32.

As illustrated in Fig. 3, the main circumferential rib 31 has a wavy horizontal cross-sectional shape with a depth that varies continuously in the circumferential direction of the plastic bottle 100. The depth has a maximum value of 4.5 mm. and a minimum value of 3.5 mm. The main circumferential rib 31 has seven points of greater depth 31a and seven points of lesser depth 31b. The horizontal cross-sectional shape of the main circumferential rib 31 is a wavy shape formed by connecting the points of greater depth 31a and the points of lesser depth 31b smoothly and alternately one after another. In other words, the shape of the horizontal cross section is formed with a closed curve protruding towards the outside of the plastic bottle around each point of greatest depth 31 a, protruding towards the inside of the plastic bottle around each point of lesser depth 31b, and having an inflection point between each point of greater depth 31a and each point of lesser depth 31b adjacent thereto.

The main circumferential rib 31 has a dimension in the top to bottom direction of (i) 8.0 mm at each point of greatest depth 31a and (ii) 7.2 mm at each point of least depth 31 b.

As illustrated in Figs. 1 and 2, the body part 3 may be provided with a plurality of subcircumferential ribs 32. The present embodiment involves three subcircumferential ribs 32 in the upper region 3a and two subcircumferential ribs 32 in the lower region 3c. The present embodiment is arranged so that each of the subcircumferential ribs 32 has a circular horizontal cross-sectional shape with a depth of 1.5 mm and a dimension in the top-to-bottom direction of 4.9 mm.

A horizontal load on the plastic bottle 100 may deform the plastic bottle 100 such that the horizontal cross-sectional shape becomes elliptical. However, the plastic bottle 100 of the present embodiment, which has a main circumferential rib 31 with a wavy horizontal cross-sectional shape, is structured so that the load on the plastic bottle 100 is not easily concentrated. Therefore, horizontal loading does not easily deform the plastic bottle 100.

A load on the plastic bottle 100 in the top-down direction can also deform the plastic bottle 100 in the top-down direction. However, the plastic bottle 100 like the present embodiment, which has a main circumferential rib 31 and subcircumferential ribs 32 with different depths and dimensions in the direction from top to bottom, allows those ribs to function together as a spring to relieve the load. in the direction from top to bottom. Therefore, loading in the up-down direction does not easily deform the plastic bottle 100.

[Panel structure]

The body part 3 is provided, in a middle region 3b thereof, with a plurality of (for the present embodiment, six) panels 33 which are sunken in the radial direction and which are arranged in the circumferential direction of the middle region 3b at regular intervals. As illustrated in Fig. 5, each of the panels 33 is shaped to extend in the top-down direction of the middle region 3b, and each is also twisted in shape in the circumferential direction of the plastic bottle 100 with the central axis of the plastic bottle 100 as the center. Each of the panels 33 is surrounded by a body part reference surface 34.

As illustrated in Figs. 5 to 7, each of the panels 33 includes a first panel depression 33a, a second panel depression 33b and panel projections 33c. The first panel depression 33a has a flat shape and recesses from the reference surface of the body part 34 towards the interior of the plastic bottle 100. The second panel depression 33b is present in the circumferential center of the first depression of panel 33a and sinks in the direction from the first depression of panel 33a further into the interior of the plastic bottle 100.

At the panel projections 33c, the opposite ends of the first panel depression 33a in the top-to-bottom direction each have the shape of a curved surface projecting from the first panel depression 33a toward the outside of the plastic bottle. 100 over the entire circumferential width of the first panel depression 33a. Each of the panel projections 33c has a dimension in the top-to-bottom direction whose dimension is smallest at the opposite circumferential ends of the panel projection 33c and largest at the circumferential central portion of the panel projection 33c.

Two body part reference surfaces 34 extending from two different first panel depressions 33a join together at a ridge part 34a. The body part reference surfaces 34 are separated from the central axis of the plastic bottle 100 by the largest distance at the ridge parts 34a.

Conventional plastic bottles include reduced pressure absorbing parts that suffer from the following strength problems: the reduced pressure absorbing parts are easily deformed radially outward when the bottle is pressurized for filling with a beverage, and are easily depressed due to shrinkage. (called a shrink mark) when the bottle is molded. The plastic bottle 100 as the present embodiment includes panels 33, each reinforced with panel projections 33c, and does not easily suffer from the above problematic deformation.

[Bottom structure]

As illustrated in Figs. 5, 8 and 9, the bottom part 4 includes (i) a floor part 41 configured to come into contact with a placing surface of a table or the like and (ii) a dome part 42 that is recessed towards the interior of the plastic bottle 100 (upward in Fig. 5) as it extends from the floor portion 41 radially inward. The dome portion 42 includes (i) in a central portion thereof a flat dome central portion 421 and (ii) a plurality of bottom depressions 422 (which are an example of a "depression") present over an area extending from the outer side of the central dome part 421 to the inner side of the floor part 41. The depressions of the bottom part 422 are depressed from the dome part 42 further into the interior of the plastic bottle 100.

As illustrated in Fig. 9, the bottom depressions 422 are, in plan view, each shaped like a concave hexagon (the so-called bow-tie shape) with four sharp vertices 422a, each of which has a interior angle of 70° and two reentrant vertices 422b each having an interior angle of 220°. Each acute vertex 422a is adjacent to another acute vertex 422a and a reentrant vertex 422b, while each reentrant vertex 422b is adjacent to two acute vertices 422a. The concave hexagon has sides of 3 mm each and diagonals of which the longest measure 6 mm in length. The depressions in the bottom 422 each have a depth of 1.2 mm.

As illustrated in Figs. 8 and 9, the bottom depressions 422 form rows of bottom depressions 423 (which are an example of a "row of depressions") each formed by a plurality of bottom depressions 422 arranged in a row. The rows of bottom depressions 423 are each formed by a plurality of bottom depressions 422 adjacent to each other such that the respective central axes CA of the plurality of bottom depressions 422 coincide with each other, being each of the central axes<C a>an extension of the center line<C l>of the corresponding depression of the bottom 422, connecting the center line<C l>connecting the respective center points of two opposite sides of the corresponding depression of the lower part 422, each of the central points being present between two acute vertices 422a.

As illustrated in Figs. 8 and 9, the plurality of rows of bottom depressions 423 have respective central axes parallel to each other. Two rows of adjacent bottom depressions 423a and 423b (which are an example of "first row of depressions" and an example of "second row of depressions") are offset from each other along each central axis<C a, >and the width of the offset is 2.6 mm, which is half the length (5.2 mm) of the center line<C l .>The term "offset" as used herein means that a plurality of rows of bottom depressions 423 are present such that there is no coincidence between (i) a straight line connecting the two reentrant vertices 422b of each bottom depression 422 included in a first row of bottom depressions 423a and (ii) a straight line connecting the two reentrant vertices 422b of each bottom depression 422 included in a second row of bottom depressions 423b adjacent to the first row of bottom depressions 423a. The term "offset width" indicates the distance between these two straight lines.

Furthermore, three bottom depressions 422 adjacent to each other are arranged in a pattern such that two sharp vertices 422a and a reentrant vertex 422b are close to each other. Stated another way, two respective sharp vertices 422a of two adjacent bottom depressions 422 included in the row of bottom depressions 423a whose sharp vertices 422a are adjacent to each other are located, in plan view, outside a reentrant vertex. 422b of a bottom depression 422 included in the row of bottom depressions 423b in a pattern such that the sharp vertices 422a are nested in the reentrant vertex 422b in a plan view (see part A in Fig. 9 ). Such a socket arrangement is formed by any three depressions of the bottom 422, adjacent to each other.

The plastic bottle 100 as the present embodiment, having bottom depressions 422 with a mutual interlocking arrangement as described above, reduces the movement of the bottom depressions 422 along the bottom surface. This prevents the bottom part 4 from deforming. This allows the plastic bottle 100 to resist a load that could otherwise cause deformation, and advantageously prevents the entire plastic bottle 100 from easily deforming.

[Other realizations]

Finally, the following description refers to plastic bottles as other embodiments of the present invention. The arrangement described below for any embodiment may be combined with the arrangement described for any other embodiment unless such combination causes any convenience.

The embodiment described above is an exemplary arrangement that includes a single main circumferential rib 31. However, the present invention is not limited to such an arrangement. The plastic bottle according to the present invention may alternatively include a plurality of circumferential ribs. For a better effect of relieving a load in the direction from top to bottom, the plastic bottle, as in the embodiment described above, preferably includes a single main circumferential rib, preferably includes at least one subcircumferential rib in addition to the main circumferential rib, more preferably it includes at least five subcircumferential ribs in addition to the main circumferential rib.

The embodiment described above is an exemplary arrangement in which the main circumferential rib 31 has seven points of greater depth 31a and seven points of lesser depth 31b. However, the present invention is not limited to said provision. The main circumferential rib may have any number of points of greater depth and any number of points of lesser depth as long as these numbers are equal to each other and each of them is two or more. For a better effect of preventing the concentration of a horizontal load, the main circumferential rib preferably has six to nine points of greatest depth and six to nine points of shallowest depth.

The embodiment described above is an exemplary arrangement in which the main circumferential rib 31 has a maximum depth of 4.5 mm and a minimum depth of 3.5 mm. However, the present invention is not limited to said provision. The circumferential rib may have a maximum depth of 4.0 mm to 5.5 mm and a minimum depth that is 0.5 mm to 1.5 mm less than the maximum depth. The circumferential rib has a maximum depth preferably of 4.1 mm to 5.2 mm, more preferably of 4.2 mm to 5.0 mm. The circumferential rib has a minimum depth that is preferably 0.6 mm to 1.4 mm less than the maximum depth, more preferably 0.7 mm to 1.3 mm less than the maximum depth.

The embodiment described above is an exemplary arrangement in which the main circumferential rib 31 has a dimension in the top-to-bottom direction of 8.0 mm at each deepest point 31 a and 7.2 mm at each deepest point. shallower depth 31b. However, the present invention is not limited to said provision. The circumferential rib may have a dimension in the top-to-bottom direction of 6 mm to 9 mm. The circumferential rib preferably has a dimension in the top-to-bottom direction of 6.2 mm to 8.8 mm, more preferably 6.5 mm to 8.5 mm.

The embodiment described above is an exemplary arrangement in which two body part reference surfaces 34 extending from two different first panel depressions 33a are joined together at a ridge part 34a. However, the present invention is not limited to such an arrangement and may be arranged, for example, so that two reference surfaces of body parts join each other in a region having a planar connecting portion.

The embodiment described above is an exemplary arrangement in which each of the first panel depressions 33a has a planar shape. However, the present invention is not limited to said provision. The first panel depression may have, for example, a rib to reduce pressure absorption.

The embodiment described above is an exemplary arrangement in which the acute vertices 422a each have an interior angle of 70°, and the reentrant vertices 422b each have an interior angle of 220°. However, the present invention is not limited to said provision. The acute vertex may have an interior angle greater than 60° and no greater than 80°. The acute vertex preferably has an interior angle of no less than 63° and no more than 87°, more preferably no less than 65° and no more than 75°.

The embodiment described above is an exemplary arrangement in which the concave hexagon has diagonals of which the longest have a length of 6 mm. However, the present invention is not limited to said provision. The longest diagonals can be from 3 mm to 8 mm in length. The longer diagonals preferably have a length of 4 mm to 7 mm, more preferably 5 mm to 7 mm.

The embodiment described above is an exemplary arrangement in which the bottom depressions 422 each have a depth of 1.2 mm. However, the present invention is not limited to said provision. The depression at the bottom can have a depth of 0.6 mm to 2.4 mm. The bottom depression preferably has a depth of 0.5 mm to 2.5 mm, more preferably 0.7 mm to 2.3 mm.

The embodiment described above is an exemplary arrangement in which the width of the offset between two rows of bottom depressions 423a and 423b adjacent to each other is 2.6 mm, which is half the length (5, 2 mm) from the center line CL. However, the present invention is not limited to said provision. The offset width can be 40% to 60% of the centerline length. The offset width is preferably 45% to 55%, more preferably 48% to 52%, especially preferably 50% of the length of the center line.

Embodiments of any arrangement other than the above set forth herein are also merely examples in all respects and do not limit the scope of the present invention. One skilled in the art will readily understand that the embodiments may be modified as appropriate without departing from the scope of the appended claims.

Industrial applicability

The present invention is applicable, for example, to a container for a soft drink.

List of reference signs

100 Plastic bottle

1 Mouth part

2 Shoulder part

3 Body part

3rd Upper region of the body part.

3b Middle region of the body part.

3c Lower region of the body part.

31 Main circumferential rib

32 Subcircumferential rib

33 Panel

33rd First panel depression

33b Second panel depression

33c Panel projection

34 Body part reference surface

34th Part of ridge

4 Bottom

41 Floor part

42 Dome part

421 Central part of dome

422 Bottom Depression

422a Acute vertex of the depression in the lower part.

422b Reentrant vertex of the bottom depression.

423 (423a, 423b) Row of bottom depressions

central box

Cl Center line

A Part of mutual lacing of the depressions of the bottom

Claims (9)

1. A plastic bottle (100), comprising: a mouth part (1) like a spout for liquid, a shoulder part (2) continuous with the mouth part (1) and having a diameter that gradually increases towards the lower surface, a body part (3) continuous with the shoulder part (2) and having a cylindrical shape, and a lower part (4) on the opposite side of the mouth part (1) provided with a plurality of depressions (422), where each of the depressions (422) is in a direction from the bottom (4) towards the interior of the plastic bottle (100), characterized in that each of the depressions (422) has, in a plan view, the shape of a concave hexagon with (i) four acute vertices (422a) that have respective interior angles, each of which is acute and (ii ) two reentrant vertices (422b) that have respective interior angles that are each greater than 180° and less than 360°, the acute vertices (422a) are each adjacent to another of the acute vertices (422a) and to one of the reentrant vertices (422b), and The reentrant vertices (422b) are each adjacent to two of the acute vertices (422a), where the depressions (422) are provided with a mutually engaging arrangement. 2. The plastic bottle (100) according to claim 1, wherein the respective interior angles of the four acute vertices are equal to each other, and the respective interior angles of the two reentrant vertices are equal to each other. 3. The plastic bottle (100) according to claim 1 or 2, wherein the depressions (422) include at least one row of depressions (423) formed by a plurality of depressions (422) at the bottom ( 4). 4. The plastic bottle (100) according to claim 3, wherein the plurality of depressions (422) in at least one row of depressions (423) are adjacent to each other in such a way that the respective central axes (C<a>) of the plurality of depressions coincide with each other, each of the axes being centers (C<a>) one an extension of a center line (C<l>) of a corresponding of the plurality of depressions (422), connecting the center line (C<l>) respective center points of two opposite sides of the corresponding one of the plurality of depressions (422), each of the central points being present between two of the acute vertices (422a) of the concave hexagon, and at least one row of depressions (423) includes at least two rows of depressions (423a, 423b) having respective central axes (C<a>) parallel to each other. 5. The plastic bottle (100) according to claim 4, wherein at least two rows of depressions (423a, 423b) include a first row of depressions (423a) and a second row of depressions (423b) that are adjacent to each other, The first row of depressions (423a) and the second row of depressions (423b) are offset from each other in a direction along the respective central axes (C<a>) of the first row of depressions (423a) and of the second row of depressions (423b), a width of the offset is 40% to 60% of the length of each of the central lines (C<l>), and one of the acute vertices (422a) of a first depression (422) included in the first row of depressions (423a) and one of the acute vertices (422a) of a second depression (422) included in the first row of depressions (423a) whose second depression (422) is adjacent to the first depression, being adjacent to each other, are located , in a plan view, outside one of the reentrant vertices (422b) of a depression (422) included in the second row of depressions (423b) in a pattern such that they fit into said one of the reentrant vertices (422b) in the plan view. 6. The plastic bottle (100) according to any one of claims 1 to 5, wherein the respective interior angles of the acute vertices (422a) are each greater than 60° and no greater than 80°. 7. The plastic bottle (100) according to any one of claims 1 to 6, wherein each of the depressions (422) has a dimension of 0.5 mm to 2.5 mm in the direction from the bottom part (4) towards the inside of the plastic bottle (100). 8. The plastic bottle (100) according to any one of claims 1 to 7, wherein the concave hexagon has diagonals, the longest of which measures between 3 mm and 8 mm in length. 9. The plastic bottle (100) according to any of claims 1 to 8, wherein The bottom portion (4) includes a dome portion (42) that sinks toward the interior of the plastic bottle (100) as the dome portion (42) extends from a floor portion (41) of the plastic bottle (100) radially towards the interior of the plastic bottle (100), and The depressions (422) are in a direction from the dome portion (42) further into the interior of the plastic bottle (100).