Plastic bottle

Abstract

[Problem] To provide a plastic bottle which can ensure a pressure-reduction absorbing function and enables an attractive design that is lacking in existing bottles. [Solution] A plastic bottle 1 having a body portion 4, wherein the body portion 4 comprises: a pressure-reduction absorbing portion 42 comprising a transverse section in which peak portions 61 and trough portions 62 are alternately repeated in a circumferential direction without a step; an upper-side cylindrical portion 41 which is contiguous with an upper side of the pressure-reduction absorbing portion 42 and has a circular transverse section; and a lower-side cylindrical portion 43 which is contiguous with a lower side of the pressure-reduction absorbing portion 42 and has a circular transverse section. The transverse section of the pressure-reduction absorbing portion 42 varies in a vertical direction so that the pressure-reduction absorbing portion 42 is contiguous with the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43 without a step.

Description

PLASTIC BOTTLECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of Japanese Patent Application No. 2023- 136896, filed August 25, 2023, which is hereby incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] The present invention relates to a plastic bottle (also referred to below simply as a "‘bottle”).BACKGROUND ART

[0003] Plastic bottles are widely used as PET bottles for beverages, and in the case of bottles used for non-carbonated beverages, a plurality of pressure-reduction absorbing panels are generally formed on a body portion, and negative pressure generated after the bottle has been filled with a beverage, etc. is absorbed by the pressure-reduction absorbing panels in order to suppress irregular deformation of the bottle as a whole (see Patent Document 1).

[0004] Pressure-reduction absorbing panels of this type generally comprise window-shaped panels formed as indentations in a side surface of the body portion. For example, window-shaped pressure-reduction absorbing panels comprise a vertically-long rectangular panel bottom surface, and a frame portion raised from a peripheral edge of the panel bottom surface, forming a step between the panel bottom surface and the side surface of the body portion. The plurality of pressure-reduction absorbing panels are then formed at equal circumferential intervals on the body portion, with the parts between the pressure-reduction absorbing panels functioning as supports (parts of higher strength than the panel bottom surfaces). When a reduction in pressure is absorbed, the panels behave in such a w ay that the panel bottom surfaces contract inwardly of the bottle. By this means, the reduction inpressure is absorbed while the shape of the bottle overall is maintained by the supports which do not deform.PRIOR ART DOCUMENTSPatent Documents

[0005] Patent Document 1 JP 2022-132522 A.SUMMARY OF THE INVENTIONProblems to be Solved by the Invention

[0006] The conventional design employing window-shaped pressure-reduction absorbing panels such as these tends to give a mechanical impression, and there is a limit to distinguishing the design from that of other bottles.

[0007] The objective of the present invention lies in providing a plastic bottle which can ensure a pressure-reduction absorbing function and enables an attractive design that is lacking in existing bottles.Means for Solving the Problems

[0008] A plastic bottle according to an embodiment of the present has a body portion, wherein the body portion comprises: a pressure-reduction absorbing portion comprising a transverse section in which peak portions and trough portions are alternately repeated in a circumferential direction without a step; an upper-side cylindrical portion which is contiguous with an upper side of the pressure-reduction absorbing portion and has a circular transverse section; and a lower-side cylindrical portion which is contiguous with a lower side of the pressure-reduction absorbing portion and has a circular transverse section, and the transverse section of the pressure-reduction absorbing portion varies in a vertical direction so that the pressure-reduction absorbing portion is contiguous with the upper-side cylindrical portion and the lower-side cylindrical portion without a step.

[0009] According to this embodiment, the transverse section of the pressure-reduction absorbing portion comprises the peak portions and the trough portions which are alternately repeated in the circumferential direction without a step, and deformation behavior is therefore achieved such that, when there is a reduction in pressure inside the bottle, the diameter in the transverse section of the pressure-reduction absorbing portion decreases uniformly as a result of the reduction in pressure. This makes it possible to absorb the reduction in pressure so that the body portion can be caused to deform in a regular manner.

[0010] Furthermore, in this embodiment, the pressure-reduction absorbing portion is contiguous with the upper-side cylindrical portion and the lower-side cylindrical portion without a step, so the pressure-reduction absorbing portion behaves in such a way that deformation is transmitted to the upper-side cylindrical portion and the lower-side cylindrical portion, and the circular transverse sections of the upper-side cylindrical portion and the lower-side cylindrical portion can also change. Specifically, the transverse sections of the upper-side cylindrical portion and the lower-side cylindrical portions deform from a circular shape to a shape close to the transverse section of the pressure-reduction absorbing portion (a transverse section in which the peak portions and the trough portions are alternately repeated in the circumferential direction without a step), and the diameter can uniformly decrease. This makes it possible to improve the effect of absorbing pressure reductions and to improve regular deformation of the body portion.

[0011] In particular, when there is a reduction in pressure inside the bottle, the trough portions in the transverse section of the pressure-reduction absorbing portion can first of all deform inwardly of the bottle. As a result of this deformation, the peak portions in the transverse section of the pressure-reduction absorbing portion then deform to become narrower, and the peak portions are thereby strengthened. Rather than the parts between pressure-reduction absorbing panels (supports) not being caused to deform, as is the case conventionally, the peak portions which are capable of functioningas supports are caused to deform by the reduction in pressure and are thereby strengthened so that it is possible to promote regular deformation of the body portion as a whole.

[0012] According to an embodiment of the present invention, it is thus possible to widen the scope of bottle designs while ensuring a pressure-reduction absorbing function with a different approach from the conventional window-shaped pressure-reduction absorbing panels.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Fig. 1 is a front view of a plastic bottle according to an embodiment.

[0014] Fig. 2 is an end face view in a longitudinal section of the plastic bottle in fig. 1 .

[0015] Fig. 3A is an end face view in a transverse section of the upper-side cylindrical portion, taken along the line A-A in fig. 2.

[0016] Fig. 3B is an end face view in transverse section of the lower-side cylindrical portion, taken along the line B-B in fig. 2.

[0017] Fig. 4 is an end face view in a transverse section of the pressure-reduction absorbing portion, taken along the line IV-IV in fig. 2.

[0018] Fig. 4A is a diagram in which inflection points, etc. have been added to the end face view of fig. 4 in order to illustrate the transverse section of the pressure-reduction absorbing portion.

[0019] Fig. 5 is a diagram showing deformation behavior of the pressure-reduction absorbing portion of the bottle in fig. 1 when a reduction in pressure is absorbed.

[0020] Fig. 6 is an end face view in a transverse section of the pressure-reduction absorbing portion according to a variant example.

[0021] Fig. 7 is an end face view in transverse section of the pressure-reduction absorbing portion according to a different variant example.

[0022] Fig. 8 is a front view of a plastic bottle according to a different embodiment.

[0023] Fig. 9 is a front view of a plastic bottle according to another different embodiment.EMBODIMENTS OF THE INVENTION

[0024] A plastic bottle according to a preferred embodiment of the present invention will be described with reference to the appended drawings. In the following description, the side where the mouth portion of the bottle is present is referred to as the upper side, and the side where the bottom portion of the bottle is present is referred to as the lower side. A longitudinal section means a cross section on a plane including a center axis of the bottle. A transverse section means a cross section on a plane orthogonal to the center axis of the bottle.

[0025] First EmbodimentAs shown in fig. 1 and 2, a plastic bottle 1 (referred to below as '‘the bottle 1 ”) comprises a mouth portion 2, a shoulder portion 3, a body portion 4, and a bottom portion 5. in that order from the upper side. These parts (2, 3. 4 and 5) are formed as a single piece and constitute a bottomed cylindrical bottle wall for internally holding a beverage. Beverages which are suitably held include non-carbonated drinks such as water, green tea, oolong tea, blended tea, sports drinks and fruit juices. The bottle 1 may also internally hold various types of liquids other than beverages, including detergents, soap, shampoo, and sauces. Furthermore, the bottle 1 is a medium-sized bottle having a capacity of around 500 mL. It should be noted that the contents which are held and the capacity are not limited to those described above.

[0026] The bottle I is molded by means of a stretch molding process such as biaxial stretch blow molding using a thermoplastic resin such as polyethylene, polypropylene, or polyethylene terephthalate as the main material, for example. An example of the process of producing the bottle 1 will be described. The thermoplastic resin is first of all injected into a metal die and a preform is injection molded. The preform comprises a mouth portion having the same shape as the mouth portion 2, and a bottomed cylindricalportion contiguously joined to the lower side thereof. After the injection molding, the preform is set in a blow molding machine and the cylindrical portion of the preform is heated. The cylindrical portion is then stretched in a longitudinal direction by means of a stretching rod, while compressed air is also blown in to stretch the cylindrical portion in a transverse direction. The stretched cylindrical portion part is pressed against an inner surface of the metal die and then allowed to harden. The shoulder portion 3, the body portion 4, and the bottom portion 5 are molded by this means, completing the series of processes for molding the bottle 1.

[0027] The mouth portion 2 is open at an upper end and functions as a spout for pouring the beverage. The opening at the mouth portion 2 is opened and closed by means of a cap which is not depicted. At the shoulder portion 3, a circular transverse section gradually enlarges downwardly, and the shoulder portion 3 connects the mouth portion 2, where the bottle 1 has the smallest diameter, to an upper end of the body portion 4, which constitutes the part of the bottle 1 having the largest diameter. The bottom portion 5 is formed by a bottom wall 21 and a circumferential wall 22. The circumferential wall 22 is a cylindrical part which rises so as to slightly open out upwardly from a circumferential edge of the bottom wall 21 , and is j oined to a lower end of the body portion 4. There are no particular limitations as to the shapes of the mouth portion 2, the shoulder portion 3 and the bottom portion 5. and these shapes may be designed as appropriate.

[0028] The body portion 4 is divided into at least three regions in the vertical direction due to differences in shape in the transverse section. Here, the body portion 4 comprises an upper-side cylindrical portion 41 , a pressure-reduction absorbing portion 42, and a lower-side cylindrical portion 43, in that order from the upper side. The upper-side cylindrical portion 41 and the lower-side cylindrical portion 43 each comprise a circular transverse section, as shown in fig. 3A and 3B. Meanwhile, the pressure-reduction absorbing portion 42 comprises a flower-shaped transverse section as shown in fig. 4 (to be described in detail later).

[0029] The upper-side cylindrical portion 41 comprises a straight portion 51 and a constricted portion 52. The straight portion 51 has, in a front view, the shape of a cylindrical vessel, the outermost shape of which does not change inwardly or outwardly in the vertical direction. A plurality of (in this case two) reinforcing circumferential grooves 54 are formed on the straight portion 51. The shoulder portion 3 is contiguous with the upper side of the straight portion 51, and the constricted portion 52 is contiguous with the lower side of the straight portion 51. The constricted portion 52 has, in a front view, a shape in which an intermediate portion in the vertical direction constricts inwardly. A center portion of the constricted portion 52 constitutes the part of the body portion 4 having the smallest diameter, and a reinforcing circumferential groove 56 is formed here.

[0030] The lower-side cylindrical portion 43 is located between and is contiguous with the pressure-reduction absorbing portion 42 and the bottom portion 5. A reinforcing circumferential groove 58 is formed between the lower-side cylindrical portion 43 and the circumferential wall 22 of the bottom portion 5.

[0031] In another embodiment, the parts of the body portion 4 may have different forms. For example, one or all of the circumferential grooves 54. 56, 58 may be omitted. Furthermore, the shapes and heights of the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43 may also be appropriately modified, provided that the parts which are joined to the pressure-reduction absorbing portion 42 still have a circular transverse section. That is to say, the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43 need not have a circular transverse section at all locations in a height direction (center axis Y-Y direction). One of the straight portion 51 and the constricted portion 52 may be omitted from the upper-side cylindrical portion 41.

[0032] The pressure-reduction absorbing portion 42 has, in a front view, a shape in which the intermediate portion in the vertical direction protrudes outwardly. In a bulging shape such as this, a lateral outline of thepressure-reduction absorbing portion 42, as seen in a front view, forms outward projections between an upper end and a lower end. Here, the height (the length in the center axis Y-Y direction) of the pressure-reduction absorbing portion 42 is greater than the heights of the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43.

[0033] As shown in fig. 4 and 4A, the pressure-reduction absorbing portion 42 comprises a transverse section in which peak portions 61 and trough portions 62 are alternately repeated in a circumferential direction without a step. Here, eight each of the peak portions 61 and the trough portions 62 are arranged alternately in the circumferential direction. That is to say, the transverse section of the pressure-reduction absorbing portion 42 has rotational symmetry of order 8.

[0034] The peak portions 61 and the trough portions 62 are connected via inflection points 63. The inflection points 63 have the same definition as the mathematical definition of inflection points, meaning points where the second derivative changes sign. In a transverse section of the pressure-reduction absorbing portion 42, the peak portions 61 form convex curves in a radial direction seen from inside the bottle, and the trough portions 62 form concave curves in the radial direction seen from inside the bottle, with the convex and concave shapes of the curves switching at the inflection points 63.

[0035] An arc length [3 constituting the peak portions 61 is greater than an arc length a constituting the trough portions 62. The following relationship is then satisfied, for example.0.5 < a / p

[0036] The trough portions 62 are formed by one arc having a center of curvature outside the bottle. The peak portions 61 include an arc having a center of curvature inside the bottle, this arc constituting the outermost shape of the body portion 4 and forming part of one imaginary circle 65. The peak portions 61 may be formed by this one arc alone, or may include different arcs or straight lines joined at the inflection points 63 on both sides of said one arc.If straight lines are then included, the lengths of the straight lines should be sufficiently smaller than the length of the arc, for example 1 mm less.

[0037] The depth of the trough portions 62 is a length corresponding to distance a - distance b. The distance a is a distance between the tip of the peak portions 61 and the center axis Y-Y. and the distance b is a distance between the tip of the trough portions 62 and the center axis Y-Y. The width of the trough portions 62 is a length corresponding to the distance between the inflection points 63 on both sides of the tip of the trough portions 62. The distance a and the distance b satisfy the following relationship, for example.0.05 < (a-b) / a < 0.35

[0038] The transverse section of the pressure-reduction absorbing portion 42 varies in the vertical direction in such a way that the pressure-reduction absorbing portion 42 is contiguous with the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43 without a step.

[0039] Specifically, the depth and width of the trough portions 62 at the intermediate portion of the pressure-reduction absorbing portion 42 in the vertical direction are greater than the depth and the width of the trough portions 62 at vertical end portions of the pressure-reduction absorbing portion 42 (see fig. 1). The depth and width of the trough portions 62 are greatest on the line IV-IV in fig. 2. Furthermore, the depth of the trough portions 62 is no longer present at the vertical ends of the pressure-reduction absorbing portion 42 (at boundaries of the pressure-reduction absorbing portion 42 with the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43). In other words, the transverse section of the pressure-reduction absorbing portion 42 varies so as to converge into a circular transverse section at the boundaries of the pressure-reduction absorbing portion 42 with the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43.

[0040] This change in the transverse cross section can also be described as the pressure-reduction absorbing portion 42 having a flower-shaped transverse section in which the depth and the width of the trough portions 62are greatest at the intermediate portion in the vertical direction. The transverse section of this flower shape may have a predetermined length in the vertical direction. The transverse section of the pressure-reduction absorbing portion 42 gradually changes toward the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43 so as to converge from the flower shape into a circular shape. In this way, the upper end of the pressure-reduction absorbing portion 42 is contiguous with the upper-side cylindrical portion 41 without a step, and the lower end of the pressure-reduction absorbing portion 42 is furthermore contiguous with the lower-side cylindrical portion 43 without a step.

[0041] Fig. 5 is a diagram showing deformation behavior of the pressure-reduction absorbing portion 42 of the body portion 4 when a reduction in pressure is absorbed. Fig. 5 shows the deformation behavior of the peak portions 61 and the trough portions 62 in a transverse section on the line IV-IV in fig. 2. When the body portion 4 absorbs a reduction in pressure, the trough portions 62 deform inwardly of the bottle, and, as a result of this deformation, the peak portions 61 plastically deform so as to become narrower.

[0042] Specifically, when there is a reduction in pressure inside the bottle, the trough portions 62 in the transverse section of the pressure-reduction absorbing portion 42 of the bottle 1 first of all deform inwardly of the bottle (see the arrows 71 in fig. 5). At this time, the plurality of (in this case eight) trough portions 62 in the transverse section deform uniformly toward the center axis Y-Y. As a result of this deformation, the peak portions 61 in the transverse section of the pressure-reduction absorbing portion 42 then deform to become narrower (see the arrows 72 in fig. 5). At this time, the plurality of (in this case eight) peak portions 61 in the transverse section contract uniformly in the circumferential direction (see the arrows 72 in fig. 5). This contraction increases the strength of the peak portions 61. Deformation behavior is thus achieved such that the diameter in the transverse section of the pressure-reduction absorbing portion 42 decreases uniformly asa result of the reduction in pressure.

[0043] When there is a reduction in pressure inside the bottle, the bottle starts to deform inwardly from the location in the pressure-reduction absorbing portion 42 where the trough portions 62 are deepest (the position of the line 1V-1V in fig. 2). This deformation behavior is then steadily transmitted to the upper side and the lower side, and when the deformation is transmitted to the upper end and the lower end of the pressure-reduction absorbing portion 42, it is transmitted to the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43. As a result, the transverse sections of the lower portion of the upper-side cylindrical portion 41 and the upper portion of the lower-side cylindrical portion 43 (that is, both of the parts joined to the pressure-reduction absorbing portion 42) deform from a circular shape into a flower shape, and the maximum diameter decreases uniformly.

[0044] As described above, in the bottle 1 according to this embodiment, the body portion 4 comprises: the pressure-reduction absorbing portion 42 comprising a transverse section in which the peak portions 61 and the trough portions 62 are alternately repeated in the circumferential direction without a step; the upper-side cylindrical portion 41 which is contiguous with the upper side of the pressure-reduction absorbing portion 42 and has a circular transverse section; and the lower-side cylindrical portion 43 which is contiguous with the lower side of the pressure-reduction absorbing portion 42 and has a circular transverse section, and the transverse section of the pressure-reduction absorbing portion 42 varies in the vertical direction so that the pressure-reduction absorbing portion 42 is contiguous with the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43 without a step.

[0045] This embodiment achieves deformation behavior such that, when there is a reduction in pressure inside the bottle 1 , the reduction in pressure causes a uniform reduction in diameter in the transverse section of the pressure-reduction absorbing portion 42. This is mainly because the transverse section of the pressure-reduction absorbing portion 42 is configured so that the peak portions 61 and the trough portions 62 arealternately repeated in the circumferential direction without a step. Furthermore, the deformation behavior afforded by the pressure-reduction absorbing portion 42 is transmitted to the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43 so that the circular transverse sections of the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43 also change. Specifically, the transverse sections of the lower portion of the upper-side cylindrical portion 41 and the upper portion of the lower-side cylindrical portion 43 deform from a circular shape to a flower shape which is close to that of the transverse section of the pressure-reduction absorbing portion 42 (a transverse section in which the peak portions and the trough portions are alternately repeated in the circumferential direction without a step), and a uniform reduction in diameter can be achieved. This is mainly because the pressure-reduction absorbing portion 42 is configured to be contiguous with the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43 without a step. The bottle 1 according to this embodiment is therefore capable of absorbing a reduction in pressure while causing the body portion 4 to deform in a regular manner.

[0046] In particular, when there is a reduction in pressure, the trough portions 62 in the transverse section of the pressure-reduction absorbing portion 42 first of all deform inwardly of the bottle and, as a result of this deformation, the peak portions 61 in the transverse section of the pressure-reduction absorbing portion 42 then deform to become narrower, whereby the peak portions 61 are strengthened. Rather than the parts between pressure-reduction absorbing panels (supports) not being caused to deform, as is the case conventionally, the peak portions 61 which are capable of functioning as supports are caused to deform by the reduction in pressure and are thereby strengthened so that it is possible to promote regular deformation of the body portion 4 overall.

[0047] The bottle 1 according to this embodiment thus makes it possible to widen the scope of bottle designs while ensuring a pressure-reduction absorbing function with a different approach from the conventionalwindow-shaped pressure-reduction absorbing panels. For example, the bulging shape of the body portion 4 (the shape when the pressure-reduction absorbing portion 42 is seen from the front) and the transverse section of the pressure-reduction absorbing portion 42 which has no steps in the horizontal direction or the vertical direction can create a favorable design impression which is rounded overall.

[0048] An embodiment of the present invention was described above with reference to specific examples. However, the present invention is not limited to those specific examples. That is to say, the scope of the present invention also encompasses appropriate design modifications added to the specific examples by a person skilled in the art, provided that any such modifications include the features of the present invention. For example, the components provided in the specific examples above, and arrangements, materials, conditions, shapes and sizes, etc. thereof are not limited to those illustrated, and may be appropriately modified.

[0049] For example, the transverse section of the pressure-reduction absorbing portion 42 is not limited to rotational symmetry of order 8. For example, said transverse section may also have rotational symmetry of order 10, as shown in fig. 6. In this case, the relationship of the distance a and the distance b is 0.05 = (a-b) / a. Furthermore, said transverse section may also have rotational symmetry of order 6 as shown in fig. 7. In this case, the relationship of the distance a and the distance b is 0.35 = (a-b) / a. From the point of view of the effect of absorbing pressure reductions, a greater depth of the trough portions 62 leads to a higher effect of absorbing pressure reductions. If the depth of the trough portions 62 is excessively large, on the other hand, it may be difficult to remove the bottle 1, which has been stretch blow molded from the preform, from the metal die. Furthermore, if there are too many orders of rotational symmetry, there is a reduction in the strength of the peak portions 61 which may make breakage more likely to occur as a result of a reduction in pressure, so the upper limit value for the order of rotational symmetry is preferably 10. Accordingly, the transverse section ofthe pressure-reduction absorbing portion 42 preferably has rotational symmetry of order 5- 10, and more preferably has rotational symmetry of order 6-8, from points of view such as the effect of absorbing pressure reductions, demolding from the metal die, and strength.

[0050] Furthermore, the overall shape of the pressure-reduction absorbing portion 42 is not limited to a bulging shape, as seen in a front view. The pressure-reduction absorbing portion 42 may have, in a front view, a straight shape in which the outermost shape does not change inwardly or outwardly in the vertical direction, as with the bottle la shown in fig. 8, for example. In a straight shape such as this, the lateral outline of the pressure-reduction absorbing portion 42, as seen in a front view, is parallel to the center axis Y-Y between the upper end and the lower end. Furthermore, the pressure-reduction absorbing portion 42 may have, in a front view, a shape in which the intermediate portion in the vertical direction constricts inwardly, as with the bottle lb shown in fig. 9. In a constricted shape (drum shape) such as this, the lateral outline of the pressure-reduction absorbing portion 42 protrudes inwardly between the upper end and the lower end. The conventional window-shaped pressure-reduction absorbing panels are generally provided in the straight shape such as shown in fig. 8, but the pressure-reduction absorbing structure (pressure-reduction absorbing portion 42) according to this embodiment may be applied not only to the straight shape but also to the bulging shape and the constricted shape, making it possible to achieve a balance between a sufficient effect of absorbing pressure reductions and improving the design.

[0051] Furthermore, the height of the pressure-reduction absorbing portion 42 may constitute virtually the entire height of the body portion 4 (see fig. 8 and 9), or may constitute a portion of the body portion 4 in the height direction (see fig. 1). From the point of view of the effect of absorbing pressure reductions, the height of the pressure-reduction absorbing portion 42 is preferably greater than half of the height of the body portion 4.

[0052] The maximum diameter of the bottle 1 should be maintained in atleast two places over the height of the body portion 4 for reasons of “vendability” (suitability for vending machines). In the case shown in fig. 1, for example, the straight portion 51 and the part of the pressure-reduction absorbing portion 42 protruding furthest outward may constitute the maximum diameter of the bottle 1. In the case shown in fig. 8, the whole of the body portion 4, or the upper-side cylindrical portion 41 and lower-side cylindrical portion 43 may constitute the maximum diameter of the bottle l a. In the case shown in fig. 9, the upper-side cylindrical portion 41 and the lower-side cylindrical portion 43 may constitute the maximum diameter of the bottle lb.

[0053] Moreover, relief (a pattern) which does not contribute to the structure or strength may also be formed on the body portion 4. For example, relief (a pattern) having a sufficiently smaller depth than the depth of the trough portions 62 may also be formed on the whole of the body portion 4 or on the pressure-reduction absorbing portion 42.

[0054] Additional notes relating to various embodiments

[0055] Embodiment 1A plastic bottle having a body portion, wherein the body portion comprises: a pressure-reduction absorbing portion comprising a transverse section in which peak portions and trough portions are alternately repeated in a circumferential direction without a step; an upper-side cylindrical portion which is contiguous with an upper side of the pressure-reduction absorbing portion and has a circular transverse section; and a lower-side cylindrical portion which is contiguous with a lower side of the pressure-reduction absorbing portion and has a circular transverse section, and the transverse section of the pressure-reduction absorbing portion varies in a vertical direction so that the pressure-reduction absorbing portion is contiguous with the upper-side cylindrical portion and the low er-side cylindrical portion without a step.

[0056] Embodiment 2The plastic bottle as described in embodiment 1, wherein the transverse section of the pressure-reduction absorbing portion varies so as to converge into a circular transverse section at boundaries of the pressure-reduction absorbing portion with the upper-side cylindrical portion and the lower-side cylindrical portion.

[0057] Embodiment 3The plastic bottle as described in embodiment 1 or 2, wherein the depth of the trough portions varies in the vertical direction so that the depth of the trough portions is no longer present at boundaries of the pressure-reduction absorbing portion with the upper-side cylindrical portion and the lower-side cylindrical portion.

[0058] Embodiment 4The plastic bottle as described in any of embodiments 1 to 3, wherein the depth of the trough portions is greater at an intermediate portion of the pressure-reduction absorbing portion in the vertical direction than at vertical end portions of the pressure-reduction absorbing portion.

[0059] Embodiment 5The plastic bottle as described in any of embodiments 1 to 4, wherein the transverse section of the pressure-reduction absorbing portion has rotational symmetry of order 5-10.

[0060] Embodiment 6The plastic bottle as described in any of embodiments 1 to 5, wherein the peak portions and the trough portions are connected via inflection points

[0061] Embodiment 7The plastic bottle as described in embodiment 6, wherein an arc length constituting the peak portions is greater than an arc length constituting the trough portions.

[0062] Embodiment 8The plastic bottle as described in embodiment 6 or 7, wherein the trough portions comprise one arc having a center of curvature on a bottle outer side.

[0063] Embodiment 9The plastic bottle as described in any of embodiments 6 to 8. wherein the peak portions include an arc having a center of curvature on a bottle inner side, and the arc constitutes the outermost shape of the body portion and forms part of one imaginary circle.

[0064] Embodiment 10The plastic bottle as described in any of embodiments 1 to 9, wherein the pressure-reduction absorbing portion has, in a front view, a shape in which the intermediate portion in the vertical direction protrudes outwardly.

[0065] Embodiment 11The plastic bottle as described in any of embodiments 1 to 9, wherein the pressure-reduction absorbing portion has, in a front view, a shape in which the intermediate portion in the vertical direction constricts inwardly.

[0066] Embodiment 12The plastic bottle as described in any of embodiments 1 to 9, wherein the pressure-reduction absorbing portion has, in a front view, a straight shape in which the outermost shape does not change inwardly or outwardly in the vertical direction.

[0067] Embodiment 13The plastic bottle as described in any of embodiments 1 to 12, wherein the upper-side cylindrical portion has a constricted portion.

[0068] Embodiment 14The plastic bottle as described in any of embodiments 1 to 13, wherein, when the body portion absorbs a reduction in pressure, the trough portions of the pressure-reduction absorbing portion deform inwardly of the bottle, and, as a result of this deformation, the peak portions of the pressure-reduction absorbing portion deform so as to become narrower.Key to Symbols

[0069] 1 , l a, lb... Bottle; 2... Mouth portion; 3... Shoulder portion; 4...Body portion; 5... Bottom portion; 21... Bottom wall; 22... Circumferential wall; 41... Upper-side cylindrical portion; 42... Pressure-reduction absorbingportion; 43... Lower-side cylindrical portion; 51... Straight portion; 52... Constricted portion; 54. 56, 58... Circumferential groove; 61... Peak portion; 62... Trough portion; 63... Inflection point; 65... Circle; 71, 72... Arrow; Y-Y... Center axis

Claims

PATENT CLAIMSClaim 1. A plastic bottle having a body portion, wherein the body portion comprises: a pressure-reduction absorbing portion comprising a transverse section in which peak portions and trough portions are alternately repeated in a circumferential direction without a step; an upper-side cylindrical portion which is contiguous with an upper side of the pressure-reduction absorbing portion and has a circular transverse section; and a lower-side cylindrical portion which is contiguous with a lower side of the pressure-reduction absorbing portion and has a circular transverse section, and the transverse section of the pressure-reduction absorbing portion varies in a vertical direction so that the pressure-reduction absorbing portion is contiguous with the upper-side cylindrical portion and the lower-side cylindrical portion without a step.Claim 2. The plastic bottle as claimed in claim 1, wherein the transverse section of the pressure-reduction absorbing portion varies so as to converge into a circular transverse section at boundaries of the pressure-reduction absorbing portion with the upper-side cylindrical portion and the lower-side cylindrical portion.Claim 3. The plastic bottle as claimed in claim 1 , wherein the depth of the trough portions varies in the vertical direction so that the depth of the trough portions is no longer present at boundaries of the pressure-reduction absorbing portion with the upper-side cylindrical portion and the lower-side cylindrical portion.Claim 4. The plastic bottle as claimed in claim 1 , wherein the depth of the trough portions is greater at an intermediate portion of the pressure-reduction absorbing portion in the vertical direction than at vertical end portions of the pressure-reduction absorbing portion.Claim 5. The plastic bottle as claimed in claim 1 , wherein the transverse section of the pressure-reduction absorbing portion has rotational symmetry of order 5- 10.Claim 6. The plastic bottle as claimed in claim 1, wherein the peak portions and the trough portions are connected via inflection points.Claim 7. The plastic bottle as claimed in claim 6, wherein an arc length constituting the peak portions is greater than an arc length constituting the trough portions.Claim 8. The plastic bottle as claimed in claim 6, wherein the trough portions comprise one arc having a center of curvature on a bottle outer side.Claim 9. The plastic bottle as claimed in claim 6, wherein the peak portions include an arc having a center of curvature on a bottle inner side, and the arc constitutes the outermost shape of the body portion and forms part of one imaginary circle.Claim 10. The plastic bottle as claimed in any one of claims 1 to 9, wherein the pressure-reduction absorbing portion has, in a front view, a shape in which the intermediate portion in the vertical direction protrudes outwardly.Claim 1 1. The plastic bottle as claimed in any one of claims 1 to 9, wherein the pressure-reduction absorbing portion has, in a front view, a shape in which the intermediate portion in the vertical direction constricts inwardly.Claim 12. The plastic bottle as claimed in any one of claims 1 to 9, wherein the pressure-reduction absorbing portion has. in a front view, a straight shape in which the outermost shape does not change inwardly or outwardly in the vertical direction.Claim 13. The plastic bottle as claimed in any one of claims 1 to 9, wherein the upper-side cylindrical portion has a constricted portion.Claim 14. The plastic bottle as claimed in any one of claims 1 to 9, wherein, when the body portion absorbs a reduction in pressure, the trough portions of the pressure-reduction absorbing portion deform inwardly of the bottle, and, as a result of this deformation, the peak portions of the pressure-reduction absorbing portion deform so as to become narrower.

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