JP2011020687A - Pressure-resistant bottle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-resistant bottle which suppresses any deformation of a bottom when the pressure inside the bottle is made positive, and prevents a consumer from misunderstanding its content since its appearance shape is close to that of a general bottom. <P>SOLUTION: The pressure-resistant bottle 10 includes a mouth 11, a barrel 12, and a bottom 20. The bottom 20 has a plurality of legs 21 extending from a center 20a to a peripheral edge 20b, and projecting downward, and a flat surface 22 extending downward from the center 20a to the peripheral edge 20b is formed between the legs 21. A ground contact surface 21a of each leg 21 is formed in a curved surface shape in the section from the center 20a to the peripheral edge 20b, and a groove 51 directed from the center 20a side to the peripheral edge 20b side through the ground contact surface 21a is formed in the leg 21. Thus, when the pressure inside the pressure-resistant bottle 10 is positive, any deformation of the bottom 20 can be suppressed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pressure-resistant bottle made of, for example, polyethylene terephthalate, which is used with a positive pressure inside, and more particularly to a pressure-resistant bottle having high strength when the inside of the bottle is set to a positive pressure.

  In recent years, it has been desired to reduce the weight of plastic bottles by reducing the amount of plastic material used in the plastic bottles. However, when the bottle is lightened, the strength of the bottle is weakened. For this reason, it is necessary to reduce the number of stacked cardboard boxes when the bottles are packed in the cardboard boxes and the cardboard boxes are loaded and stored in the warehouse.

  In addition, when selling bottles with vending machines, there is a tendency that the bottles cannot be normally discharged from the vending machine or the bottles are recessed during storage or discharging in the vending machine. In order to solve this, there is a technique of filling a bottle with an inert gas such as nitrogen immediately after filling the bottle with the content liquid in the process of manufacturing the bottle beverage, and closing the bottle. Thereby, the inside of a bottle becomes a positive pressure and it is possible to raise the intensity | strength of a bottle. In addition, filling the inside of the bottle with an inert gas such as nitrogen as described above also has an effect of preventing the content liquid (for example, green tea) from being oxidized.

  Further, when natural foaming water (sparkling water) or oxygen water is filled in the bottle, the inside of the bottle is slightly positive. Alternatively, when the bottle is filled with a content liquid such as green tea or coffee and the bottle is heated, the inside of the bottle becomes positive pressure due to thermal expansion of the content liquid or the air inside.

  Thus, when the inside of the bottle has a positive pressure, when a bottle 100 having a bottom 101 having a general shape as shown in FIG. 9 is used, the bottom 101 swells due to the inside of the bottle 100 becoming a positive pressure. The total height of 100 becomes high. Or the unevenness | corrugation of the bottom part 101 will be reversed (buckling), and the bottle 100 will not stand upright.

  For this reason, in order to give a bottle pressure resistance, it is common practice to make the bottom part a petaloid shape. In addition to the technique of making the bottom part a petaloid, there is a technique of providing the reinforcing groove 102 in the bottom part 101 as shown in FIG. 10 or making the bottom part the shape shown in Japanese Patent Publication No. 3-39897 (Patent Document 1).

Japanese Patent Publication No. 3-39897

  Since plastic bottles having a petaloid-shaped bottom are excellent in pressure resistance, many of them are used for filling and selling carbonated beverages. For this reason, consumers have a strong image that a plastic bottle having a petaloid-shaped bottom is filled with a carbonated beverage. Therefore, it is practically difficult to use a plastic bottle having such a petaloid-shaped bottom as a container of green tea or coffee in order to avoid misunderstanding the contents by the consumer. In addition, since the petaloid-shaped bottom has a shape in which a plurality of legs protrudes, there is a problem that deformation such as a dent is likely to occur due to external force.

  Moreover, since the bottle shown in FIG. 10 and Japanese Patent Publication No. 3-39897 (patent document 1) is inferior in pressure | voltage resistant performance, the pressure in a bottle cannot be made very high.

  The present invention has been made in consideration of these points, and can reduce deformation when the inside of the bottle is made positive pressure. Further, it is difficult to deform even by external force, and the consumer misunderstands the contents. An object of the present invention is to provide a pressure-resistant bottle whose appearance is close to that of a general bottle.

  The pressure-resistant bottle includes a mouth portion, a trunk portion, and a bottom portion. The bottom portion extends from the central portion to the peripheral portion and protrudes downward, and includes a plurality of legs each including a grounding surface. And a flat surface extending downward from the central portion toward the peripheral portion is formed between the leg portions, and the ground contact surface of each leg portion is formed in a curved shape in a cross section from the central portion to the peripheral portion, and at least 1 The pressure-resistant bottle is characterized in that a groove is formed in one leg portion from the central portion side to the peripheral portion side through the grounding surface.

  The present invention is the pressure resistant bottle characterized in that the number of grooves formed in each leg portion is 1 to 6.

  The present invention is the pressure-resistant bottle, wherein the depth of each groove is 0.05 mm to 3 mm.

  The present invention is a pressure-resistant bottle characterized in that at least two grooves are formed in each leg portion, and the interval between the grooves is equal to or greater than the width of each groove.

In the present invention, the length of each groove is 1 mm when the length from the lowest point of the ground plane toward the peripheral side is L ₁ and the length from the lowest point of the ground plane toward the center side is L _2. ≦ L ₁ ≦ 10 mm and 0.5 mm ≦ L ₂ ≦ 7 mm.

  The present invention is the pressure-resistant bottle characterized in that a reinforcing groove extending from the central portion side to the peripheral portion side and retracting upward is formed on each flat surface.

  The present invention is a pressure-resistant bottle characterized in that a recess that is retracted upward is formed in the center of the bottom.

  The present invention is a pressure-resistant bottle characterized in that a concave portion that is retracted upward is formed at the center of the bottom portion, and the bottom surface of the concave portion and the bottom surface of the reinforcing groove are flush with each other.

  The present invention is the pressure-resistant bottle, wherein each flat surface constitutes a part of a concave curved surface that curves upward in a cross section from the central portion toward the peripheral portion.

  The present invention is the pressure-resistant bottle characterized in that the projecting height of each leg from the flat surface on the ground contact surface is 1 mm to 3 mm.

  According to the present invention, the bottom portion has a plurality of leg portions extending from the central portion to the peripheral portion and projecting downward, and a flat surface extending downward from the central portion toward the peripheral portion is formed between the respective leg portions. The grounding surface of each leg is formed in a curved shape in a cross section from the central part to the peripheral part, and a groove is formed in at least one leg part from the central part side to the peripheral part side through the grounding surface. . This can reduce deformation when the pressure bottle is made positive. Even when the pressure-resistant bottle is thin, the strength of the bottom can be increased. For this reason, even if an external force is applied to the bottom of the bottle, deformation such as a dent is unlikely to occur.

  Further, according to the present invention, since the bottom leg portion is not conspicuous when viewed from the outside of the pressure bottle, the appearance is similar to that of a general bottle, and the consumer may misunderstand the contents of the pressure bottle. There is no.

FIG. 1 is a front view showing a pressure-resistant bottle according to an embodiment of the present invention. FIG. 2 is a perspective view showing the bottom of a pressure-resistant bottle according to an embodiment of the present invention. FIG. 3 is a bottom view showing the bottom of the pressure-resistant bottle according to one embodiment of the present invention (viewed in the direction of arrow III in FIG. 1). FIG. 4 is a vertical sectional view (sectional view taken along line IV-IV in FIG. 3) showing the bottom of the pressure-resistant bottle according to one embodiment of the present invention. FIG. 5 is a partial cross-sectional view (cross-sectional view taken along the line V-V in FIG. 3) showing the leg portion of the pressure-resistant bottle according to the embodiment of the present invention. FIG. 6 is an enlarged side view (viewed in the direction of the arrow VI in FIG. 3) showing the legs of the pressure-resistant bottle according to the embodiment of the present invention. FIG. 7 is a schematic cross-sectional view showing a change in bottom shape when an internal pressure is applied to a bottle as a comparative example. FIG. 8 is a perspective view showing the bottom of a pressure-resistant bottle according to a modification of the embodiment of the present invention (a diagram corresponding to FIG. 2). FIG. 9 is a view showing the bottom of a conventional bottle. FIG. 10 is a view showing the bottom of a conventional bottle.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 8 are views showing an embodiment of the present invention.

  First, an outline of a pressure-resistant bottle according to the present embodiment will be described with reference to FIGS. In the present specification, “flat surface” is used to mean a smooth surface having no irregularities on the surface. However, even if it has fine irregularities such as wrinkles, it is regarded as a “flat surface”. In the present specification, “upper” and “lower” refer to the upper and lower sides in the state where the pressure-resistant bottle 10 is erected (FIG. 1), respectively.

  As shown in FIG. 1, the pressure-resistant bottle 10 includes a mouth portion 11, a body portion 12 provided below the mouth portion 11, and a bottom portion 20 provided below the body portion 12.

  This pressure-resistant bottle 10 is a biaxially stretched blow molded preform formed by injection molding polyethylene terephthalate (hereinafter abbreviated as PET). In addition, as a material of the preform, that is, the pressure-resistant bottle 10, polypropylene (PP), polylactic acid (PLA), or various other thermoplastic resins can be used in addition to PET.

  The preform may have a multilayer structure, and at least one of them may be a gas barrier layer. As a gas barrier layer, the structure which laminated | stacked gas barrier resin layers, such as saponified ethylene-vinyl acetate copolymer (henceforth EVOH) and MXD6 (polymetaxylylene adipamide), can be taken. In the case of blend molding of two or more synthetic resins, the gas barrier property can be improved by, for example, blending a gas barrier resin such as MXD6 with PET and injection molding the preform. Also, oxygen barrier properties can be improved by blending an oxygen absorbent in addition to the synthetic resin into PET.

  Furthermore, by depositing an inorganic oxide such as silica or alumina or amorphous carbon on the inner wall of the bottle container, the gas barrier property can be improved while maintaining transparency. When coating means are used, gas barrier properties are improved by coating thermosetting cross-linked coating films of aromatic polyhydric epoxy compounds reacted with metaxylenediamine and epichlorohydrin and polyhydric amines, EVOH, etc. Can be made. When EVOH is coated, gas barrier properties are reduced due to moisture absorption. Therefore, it is preferable to coat a moisture-proof resin such as a polyolefin resin thereon. Any one kind of such gas barrier property improving means may be used, but the gas barrier property can be further improved by combining two or more means.

  As shown in FIGS. 1 to 6, the bottom portion 20 has nine (a plurality of) leg portions 21 that extend from the central portion 20a to the peripheral edge portion 20b and project downward.

  Three or more leg portions 21 are preferably provided in order to stably erect the pressure-resistant bottle 10, but the upper limit is about 15 from the viewpoint of formability. In order to effectively prevent buckling, the number of leg portions 21 is preferably an odd number.

  As shown in FIGS. 2 and 3, the nine leg portions 21 are arranged at equal intervals along the peripheral edge portion 20 b of the bottom portion 20.

  Further, as shown in FIGS. 3 and 4, each leg 21 includes a grounding surface 21a, an inner inclined surface 21b extending upward from the grounding surface 21a toward the central portion 20a, and a peripheral portion 20b side from the grounding surface 21a. And an outer inclined surface 21c extending upward. Among these, the grounding surface 21a is formed in a curved surface in a cross section from the central portion 20a to the peripheral edge portion 20b (see the vertical sectional view of FIG. 4). The inner inclined surface 21b has a substantially triangular shape when viewed from the bottom surface direction (see FIG. 3).

  On the other hand, between each leg part 21, the flat surface 22 extended downward toward the peripheral part 20b from the center part 20a is formed. Each flat surface 22 constitutes a part of a concave curved surface that curves upward in a cross section from the central portion 20a to the peripheral edge portion 20b (see FIG. 4).

  Further, a groove 51 is formed in each leg portion 21 from the central portion 20a side (inner inclined surface 21b) through the ground contact surface 21a toward the peripheral edge portion 20b side (outer inclined surface 21c). In the present embodiment, two grooves 51 are formed in all the leg portions 21. However, the present invention is not limited to this, and the grooves 51 may be provided only in specific (one or more) leg portions 21.

  The number of grooves 51 is not limited, but is preferably 1 to 6 with respect to one leg 21. However, if the number of grooves 51 formed in each leg portion 21 is one, the effect of the present embodiment to be described later is reduced, and if the number is five or more, the moldability of the leg portions 21 may be slightly deteriorated. . For this reason, it is more desirable that the number of grooves 51 formed in each leg portion 21 is two to four.

  Each flat surface 22 is formed with an elongated reinforcing groove 23 extending from the central portion 20a side to the peripheral edge portion 20b side and retracting upward. That is, the bottom portion 20 has nine reinforcing grooves 23 that are radially spaced from the central portion 20a.

  Further, a recess 24 having a circular shape as viewed from the bottom surface is formed in the center of each flat surface 22 while being retracted upward. The concave portion 24 is formed continuously with the reinforcing groove 23, and the bottom surface 24a of the concave portion 24 and the bottom surface 23a of the reinforcing groove 23 are flush with each other (see FIG. 4).

  Furthermore, a bottom inner side surface 25 is formed in a planar region surrounded by each leg portion 21, the reinforcing groove 23, and the concave portion 24. The bottom inner side surface 25 is formed continuously with the flat surface 22 and is flush with the flat surface 22.

The size of the pressure-resistant bottle 10 is not limited and may be any size bottle. For example, in FIG. 4, when the capacity of the pressure-resistant bottle 10 is 500 ml, the diameter 12 of the trunk portion 12 is set to 60 mm to 70 mm, and the protruding height h ₁ of the ground contact surface 21a of each leg portion 21 from the flat surface 22 is 1 mm. It is preferable to set to 3 mm. Further, it is preferable that the bottom depth of the bottom portion 20 (that is, the distance between the ground contact surface 21a of each leg portion 21 and the bottom surface 24a of the recess 24) h ₂ is 7 mm to 22 mm.

For example, when the capacity of the pressure-resistant bottle 10 is 350 ml or less, the diameter φ of the body 12 is 50 mm to 68 mm, and when the capacity is 1000 ml, the diameter 12 of the body 12 is 70 mm to 90 mm. It is preferable that the diameter φ is 80 mm to 100 mm, the protruding height h ₁ of the ground contact surface 21a of each leg 21 from the flat surface 22 is 1 mm to 3 mm, and the bottom depth h ₂ of the bottom 20 is 7 mm to 22 mm. .

In the cross section from the central portion 20a to the peripheral portion 20b, it is preferable that the radius of curvature R of the ground contact surface 21a of each leg portion 21 is 3 mm to 8 mm. Furthermore, it is preferable that the thickness t ₁ of the body portion 12 is 0.1 mm to 0.5 mm.

  In FIG. 5, the depth d of each groove 51 is preferably 0.05 mm to 3 mm, and more preferably 0.8 mm to 1.2 mm. When the depth d of the groove 51 is too shallow, the effect of providing the groove 51 is reduced, and when the depth d of the groove 51 is too deep, the moldability of the leg portion 21 may be slightly deteriorated.

In FIG. 5, the length of each groove 51 is L ₁ , which is the length from the lowest point 21d of the ground surface 21a toward the peripheral edge 20b (outside inclined surface 21c), and the lowest point 21d of the ground surface 21a. If the length toward the central portion 20a side (inner inclined surface 21b side) was L ₂ from, it is preferable to 1mm ≦ L ₁ ≦ 10mm and 0.5 mm ≦ L ₂ ≦ 7 mm. If the length of the groove 51 is too short, the effect of providing the groove 51 is reduced. On the other hand, if the length of the groove 51 is too long, the moldability of the leg portion 21 may be slightly deteriorated.

  In FIG. 6, the width b of each groove 51 is preferably 0.2 mm to 5 mm. Further, when two or more grooves 51 are formed in each leg portion 21 as in the present embodiment, it is desirable that the interval a between the grooves 51 be equal to or greater than the width b of each groove 51 (b ≦ a). This is because, if the distance a between the grooves 51 is smaller than the width b of the grooves 51 (b> a), the moldability may be deteriorated, and the area of the ground contact surface 21a is reduced. This is because there is a risk of adversely affecting the independence of the bottle 10 for use.

  Next, the operation of the present embodiment having such a configuration will be described.

  First, the pressure-resistant bottle 10 is filled with a content liquid such as green tea, and then an inert gas such as nitrogen is filled in the head space and then closed. At this time, the inside of the pressure-resistant bottle 10 becomes a positive pressure (for example, 20 to 40 kPa) by the filled inert gas or content liquid.

  When the inside of the pressure-resistant bottle 10 becomes a positive pressure, a force from the inside to the outside of the pressure-resistant bottle 10 acts, and pressure is applied from the upper side to the lower side at the bottom 20.

  On the other hand, in the present embodiment, the bottom portion 20 has nine leg portions 21 extending from the central portion 20a to the peripheral edge portion 20b and projecting downward, and between the leg portions 21, the central portion 20a extends to the peripheral edge portion. A flat surface 22 extending downward toward 20b is formed. Each flat surface 22 constitutes a part of a concave curved surface that curves upward in a cross section from the central portion 20a to the peripheral edge portion 20b. Therefore, even if the pressure bottle 10 has a positive pressure and a downward force is applied to the bottom portion 20, the bottom portion 20 is not easily deformed because the stress hardly concentrates on the bottom portion 20. Furthermore, since the adjacent leg portions 21 and the flat surface 22 located between the leg portions 21 form a rib structure, this also acts to prevent the deformation of the bottom portion 20. The reinforcing groove 23 and the recessed part 24 of the bottom part 20 also play the role which prevents the deformation | transformation of the bottom part 20 by the same effect | action.

  The ground contact surface 21a, which is a surface to which the pressure-resistant bottle 10 is grounded, is formed in a curved surface in a cross section from the central portion 20a to the peripheral portion 20b. Accordingly, even if the pressure in the pressure bottle 10 is increased and the flat surface 22 and the bottom inner surface 25 are deformed downward, the total height change amount of the pressure bottle 10 is suppressed to be small.

  Furthermore, when the pressure inside the pressure-resistant bottle 10 becomes positive, a force is applied to cause the radius of curvature R of the ground contact surface 21a of the leg 21 to increase, but the groove 51 provided in the leg 21 The deformation of the radius of curvature R can be suppressed. As a result, the total height change amount of the pressure-resistant bottle 10 is further reduced. Moreover, not only can the change in the overall height of the pressure-resistant bottle 10 be suppressed, but it can also be prevented that the legs 21 are deformed and wrinkled due to the positive pressure.

That is, as shown in FIG. 7 as a comparative example, if the ground contact surface 31 at the bottom of the bottle is a flat horizontal surface, when the pressure inside the bottle increases and the bottom of the bottle deforms, the outer edge of the ground contact 31 The angle α ₁ of the portion 31 a and the angle α ₂ of the inner edge portion 31 b of the ground contact surface 31 are deformed in directions that increase respectively (imaginary line (two-dot chain line) in FIG. 7). For this reason, the ground contact surface 31 is deformed so that the inner edge portion 31b is directed downward, so that the total height change amount of the bottle is increased.

  On the other hand, in the present embodiment, as described above, the ground contact surface 21a is formed in a curved shape in a cross section from the central portion 20a to the peripheral edge portion 20b, and is formed on the leg portion 21 from the central portion 20a side. Since the groove 51 is formed through the ground contact surface 21a toward the peripheral edge 20b, the radius of curvature R of the ground contact surface 21a of each leg 21 hardly increases when the pressure inside the pressure resistant bottle 10 increases. Thereby, the total height change amount of the pressure-resistant bottle 10 can be suppressed small.

  As described above, according to the present embodiment, the bottom portion 20 has the plurality of leg portions 21 extending from the central portion 20a to the peripheral edge portion 20b and protruding downward, and between the leg portions 21, the central portion 20a extends to the peripheral edge portion. A flat surface 22 extending downward toward 20b is formed. Each flat surface 22 constitutes a part of a concave curved surface that curves upward in a cross section from the central portion 20a to the peripheral edge portion 20b. Accordingly, the strength of the bottom portion 20 is increased, and deformation (buckling or the like) of the bottom portion 20 can be prevented when the inside of the pressure-resistant bottle 10 is set to a positive pressure.

  Further, according to the present embodiment, the reinforcing groove 23 extending from the central portion 20 a to the peripheral edge portion 20 b and retracting upward is formed on each flat surface 22, and the concave portion 24 retracting upward is formed in the central portion 20 a of the bottom portion 20. ing. As a result, the strength of the bottom portion 20 is increased, and deformation of the bottom portion 20 can be further suppressed.

  Further, according to the present embodiment, the ground contact surface 21a of each leg portion 21 is formed in a curved shape in a cross section from the central portion 20a to the peripheral edge portion 20b, and is in contact with the leg portion 21 from the central portion 20a side. Since the groove 51 passing through the ground 21a toward the peripheral edge portion 20b is formed, the total amount of change in the pressure bottle 10 can be reduced when the pressure bottle 10 is positively pressurized.

  Further, the grooves 51 provided in the respective leg portions 21 can prevent the leg portions 21 from being deformed and causing wrinkles when the inside of the bottle is made positive. Further, the leg 21 may have a dent or the like due to vibration when transporting the pressure-resistant bottle 10 filled with the content liquid, dropping the pressure-resistant bottle 10 by mistake, or dropping impact when selling with a vending machine. Although deformation may occur, since the leg portion 21 is reinforced by the groove 51, such deformation can be prevented. Even if the leg portion 21 is deformed, there is an effect that the deformation is not conspicuous because of the groove 51.

  Furthermore, according to the present embodiment, since the leg portion 21 of the bottom portion 20 is not conspicuous when viewed from the outside of the pressure-resistant bottle 10, the appearance shape of the pressure-resistant bottle 10 is close to the appearance shape of a general bottle, and the consumer There is no possibility of misunderstanding the contents of the pressure-resistant bottle 10.

  The pressure-resistant bottle 10 has an appearance shape close to that of a general bottle, so that the inside of the pressure-resistant bottle 10 can be used as a non-positive pressure. For example, in some cases, green tea is filled and then nitrogen is filled to make the pressure bottle 10 positive pressure so that it becomes a product for a vending machine. In other cases, the same pressure bottle 10 is filled only with green tea and is not automatic. It is also possible to make a product for a vending machine. Therefore, it is not necessary to prepare two types of bottle molds, and therefore there is no need to replace the molds in the bottle production factory, so that there is a secondary effect that the mold investment cost and the replacement time can be saved.

(Modification)
In addition, when the intensity | strength requested | required with respect to the pressure | voltage resistant bottle 10 is low, it is not necessary to provide the reinforcement groove | channel 23 in the bottom part 20 like the modification shown in FIG. Further, although not shown, the reinforcing groove 23 may be provided in the bottom portion 20 and the concave portion 24 may not be provided. Alternatively, neither the reinforcing groove 23 nor the recess 24 may be provided in the bottom portion 20.

DESCRIPTION OF SYMBOLS 10 Pressure-resistant bottle 11 Mouth part 12 Body part 20 Bottom part 20a Center part 20b Peripheral part 21 Leg part 21a Grounding surface 21b Inner inclined surface 21c Outer inclined surface 22 Flat surface 23 Reinforcement groove 24 Recessed part 25 Bottom inner side surface 51 Groove

Claims (10)

In pressure-resistant bottles,
The mouth,
The torso,
With a bottom,
The bottom portion extends from the central portion to the peripheral portion and protrudes downward, and has a plurality of leg portions each including a grounding surface, and a flat surface extending downward from the central portion toward the peripheral portion is formed between the respective leg portions. ,
The ground contact surface of each leg is formed in a curved surface in a cross section from the central part to the peripheral part,
A pressure-resistant bottle characterized in that a groove is formed in at least one leg portion from the central portion side to the peripheral portion side through the grounding surface.   The pressure-resistant bottle according to claim 1, wherein the number of grooves formed in each leg portion is 1 to 6.   The pressure-resistant bottle according to claim 1 or 2, wherein the depth of each groove is 0.05 mm to 3 mm.   The pressure-resistant bottle according to any one of claims 1 to 3, wherein at least two grooves are formed in each leg portion, and an interval between the grooves is equal to or greater than a width of each groove. The length of each groove is 1 mm ≦ L ₁ ≦ L ₁ when the length from the lowest point on the ground plane toward the peripheral side is L ₁ and L ₂ is the length from the lowest point on the ground plane toward the center side. The pressure-resistant bottle according to claim 1, wherein 10 mm and 0.5 mm ≦ L ₂ ≦ 7 mm.   The pressure-resistant bottle according to any one of claims 1 to 5, wherein a reinforcing groove extending from the central side to the peripheral side and retracting upward is formed on each flat surface.   The pressure-resistant bottle according to any one of claims 1 to 6, wherein a concave portion that is recessed upward is formed in a central portion of the bottom portion.   7. A pressure-resistant bottle according to claim 6, wherein a concave portion that is recessed upward is formed at a central portion of the bottom portion, and the bottom surface of the concave portion and the bottom surface of the reinforcing groove are flush with each other.   9. The pressure-resistant bottle according to claim 1, wherein each flat surface constitutes a part of a concave curved surface that curves upward in a cross section from the central portion toward the peripheral portion.   The pressure-proof bottle according to any one of claims 1 to 9, wherein a protruding height of each leg portion from the flat surface on the ground surface is 1 mm to 3 mm.

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