JP2011084315A - Plastic bottle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic bottle capable of improving strength against drop impact even if reduced in weight. <P>SOLUTION: A bottom 6 of the plastic bottle formed by biaxially oriented blow-molding includes a circumference 21 in contact with the ground when the bottle is self-supported, a center part 23 formed to swell from the circumference 21 and a dome 25 protrusively formed so that it further swells higher at the center of the center part 23. Each of a plurality of recessed grooves 27 is formed at least over the circumference 21 and the center part 23 but not formed on the dome 25. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a bottom structure of a plastic bottle formed by biaxial stretch blow molding.

  2. Description of the Related Art As plastic bottles such as PET bottles for beverages, those manufactured by performing a biaxial stretch blow molding or the like on a preform molded by injection molding or the like are known. In recent years, from the viewpoint of consideration for the environment, it has been promoted to reduce the amount of resin used as a bottle material resource as much as possible, thereby reducing the weight of the bottle (for example, see Patent Documents 1 and 2). However, the mechanical strength of the bottle thinned by weight reduction is reduced. For this reason, various ingenuity which gives strength as a commercial value to a lightweight bottle is given. Moreover, the bottle which aimed at the improvement of drop strength is also known (for example, refer patent documents 3-6).

JP 2006-315726 A JP 2009-18840 A JP 2007-30894 A JP 2005-132458 A JP-A-11-227734 JP 2009-137636 A

Design registration No. 1254725

  By the way, the present inventor has found a phenomenon in which, when the contents are cooled and filled in a bottle as described in Non-Patent Document 1, when the bottle falls, a crack is rarely generated at the center of the bottom of the bottle. It was. In addition, it was confirmed that this phenomenon occurs when the bottle falls at an inclination. As a result of examining this phenomenon, as shown in FIG. 6A, when the bottle 1 'is inclined and dropped, the load applied to the outer peripheral edge of the bottle bottom 6' that is first grounded is affected by the radial concave groove 27 '. It was transmitted to the central part 25 'of the bottle bottom part 6' through the above, and the knowledge that the cause of the stress concentration at the central part 25 'was obtained. In particular, the center portion 25 'protrudes in a dome shape into the bottle when biaxial stretch blow molding is used, but is a portion that is not oriented crystallized, so that the other portion of the bottle bottom 6' Compared to Therefore, it is a place where cracks due to stress concentration are likely to occur, and further improvement has been demanded.

  Accordingly, an object of the present invention is to provide a plastic bottle capable of increasing the strength against a drop impact even when the weight is reduced.

  In order to achieve the above object, the plastic bottle of the present invention is a biaxially stretched cylindrical tube having a bottom portion, and the bottom portion is grounded when the plastic bottle is self-supported, and the peripheral portion. A central portion formed so as to protrude from the portion, and a dome portion formed so as to protrude higher at the central portion of the central portion, each formed at least over the peripheral portion and the central portion Is provided with a plurality of concave grooves not formed in the dome portion.

  According to the present invention, even when a load is applied to the peripheral edge of the bottom due to an impact when the bottle is inclined and dropped, the load is suppressed from being propagated through the concave groove to the dome. Thereby, it is possible to avoid the stress concentration at the dome portion and the occurrence of cracks resulting therefrom. Therefore, even when the weight is reduced, it is possible to increase the strength against a drop impact while reinforcing the strength of the bottom with a plurality of concave grooves.

  Such a configuration of the plastic bottle of the present invention is more suitable as it is a so-called lightweight bottle. Here, when a lightweight bottle is defined, for example, the relationship W / V between the capacity V (ml) of a plastic bottle and the amount of resin used W (g) used for molding the plastic bottle is 0.015 or more and 0.035. It is as follows. Bottles with a W / V greater than 0.035 are no longer “light” bottles, and bottles with a W / V less than 0.015 are too thin to function as bottles. Because.

  According to a preferred aspect of the present invention, the plurality of concave grooves may extend so as to be radially centered on the dome portion as a whole. By carrying out like this, the intensity | strength of a bottle bottom part can be reinforced efficiently efficiently not locally.

  Preferably, the distance between one end of each concave groove on the dome portion side and the lower end of the dome portion (hereinafter, a portion between them is referred to as a “non-concave groove portion” in this paragraph) is 1 mm or more, And it is good that it is shorter than the length of each concave groove. If it is less than 1 mm, the load propagating through the concave groove reaches the immediate vicinity of the lower end of the dome portion, so that there is a possibility that stress concentration at the dome portion cannot be effectively suppressed. On the other hand, if the length of the non-concave groove portion exceeds the length of the concave groove, the original reinforcing effect by the concave groove may not be expected. Therefore, by setting the length of the non-concave portion as described above, it is possible to achieve both suppression of stress concentration at the dome portion and reinforcement effect by the concave groove.

  Preferably, each concave groove is formed so that at least one of the depth and width of the one end portion on the dome portion side gradually decreases toward the dome portion side. Contrary to this configuration, if the depth or width of the one end is large, it becomes difficult to extend from the bottom of the preform (for example, a part of the bottom of the bottle after molding). However, with the above configuration, it is possible to ensure the strength in consideration of the moldability of the bottom including the concave groove.

  Preferably, the plastic bottle of the present invention may further include a cylindrical body part and a curved lower peripheral wall part connecting the lower end of the body part and the outer edge of the peripheral part, and at least one of the plurality of concave grooves. May be formed also on the lower peripheral wall portion. By carrying out like this, the reinforcement effect by a concave groove can be brought also to a lower surrounding wall part, and intensity | strength can be raised more.

It is a perspective view of the plastic bottle which concerns on embodiment. It is a figure which shows the preform of the plastic bottle of FIG. 1, (A) is a top view, (B) is front sectional drawing which abbreviate | omitted hatching. It is a figure which shows the bottom periphery of the plastic bottle of FIG. 1, (A) is a front view, (B) is a bottom view, (C) is a perspective view. (A) And (B) is the longitudinal cross-sectional view cut | disconnected by the VIa-VIa line | wire and VIb-VIb line | wire of FIG. 3 (B), respectively, respectively, and shows the outline of a cutting location, omitting hatching. is there. It is a figure which shows the surroundings of the bottom part of the plastic bottle which concerns on a comparative example, (A) is a bottom view, (B) is a perspective view. It is a figure which shows about propagation of the load at the time of inclining and dropping a plastic bottle, (A) is a perspective view around the bottom part of the plastic bottle of FIG. 5 which concerns on a comparative example, (B) is a figure which concerns on embodiment. It is a perspective view around the bottom part of 1 plastic bottle.

A plastic bottle according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.
In the following description, the direction where the bottle bottom is present is the lower side, and the direction where the bottle mouth is present is the upper side. The height means a length along the direction (vertical direction) of the central axis of the bottle. A cross section means the cross-sectional shape in the plane orthogonal to the central axis of a bottle.

  As shown in FIG. 1, the plastic bottle (hereinafter referred to as “bottle 1”) includes a mouth portion 2 and a main body portion 3, and the main body portion 3 includes a shoulder portion 4, a trunk portion 5, and a bottom portion 6 in order from the upper side. Have The mouth portion 2 and the main body portion 3 are integrally formed, and constitute a bottomed cylindrical bottle wall for storing a beverage therein. Examples of the beverage include non-carbonated beverages such as water, green tea, oolong tea, and fruit juice. However, in other embodiments, the contents stored in the bottle 1 may be foods such as carbonated drinks, jelly drinks or sauces.

  The mouth part 2 is open at the upper end and functions as a beverage spout. The opening of the mouth 2 is opened and closed by a cap (not shown). The shoulder 4 has a transverse cross section that gradually expands downward, and the mouth 2 having the smallest diameter in the bottle 1 is connected to the upper end of the body 5 that forms the maximum width in the bottle 1. The shape of the mouth part 2, the shoulder part 4, and the trunk | drum 5 is not specifically limited, It can design suitably. For example, at least one of a constriction for improving ease of holding, a concave rib for improving strength, and a panel for absorbing reduced pressure can be formed in the body portion 5.

  The bottle 1 is molded by a biaxial stretch blow molding method using polyethylene terephthalate (PET). However, in other embodiments, as the resin material of the bottle 1, other plastic resins such as polyethylene and polypropylene can be used.

  An example of the manufacturing process of the bottle 1 will be described. First, polyethylene terephthalate is injected into a mold, and a preform is injection molded. As shown in FIG. 2, the preform 10 includes a mouth portion 12 having the same shape as that of the mouth portion 2 and a bottomed cylindrical portion 14 connected to the lower side of the mouth portion 12. The preform 10 is set in a biaxial stretch blow molding machine, and only the cylindrical portion 14 is heated. Then, a stretching rod is inserted from the mouth portion 12 and abutted against the bottom of the tubular portion 14. The tubular portion 14 is stretched in the longitudinal direction by the stretching rod, and the tubular portion 14 is stretched in the lateral direction by air blow. . The stretched cylindrical portion 14 is pressed against the inner surface of the mold and then solidified. By producing the inner surface of the mold in a shape corresponding to the main body portion 3 of the bottle 1, the main body portion 3 is formed. Thereby, a series of shaping | molding of the bottle 1 is completed.

  As shown in FIGS. 3 and 4, the bottom portion 6 includes a peripheral portion 21 that is grounded when the bottle 1 is self-supported, and a central portion 23 that is formed so as to protrude from the peripheral portion 21 toward the inside of the bottle. And a dome portion 25 formed so as to protrude higher in the central portion of the central portion 23. The bottom 6 is formed with a plurality of concave grooves 27 that function as ribs that reinforce the strength of the bottom 6.

  The peripheral edge portion 21 is formed of a flat narrow portion made of an annular shape. When the bottle 1 is made to stand on the installation surface 28, the only part that the bottle 1 comes into contact with is the peripheral edge 21. The outer edge 21a of the peripheral edge portion 21 is continuous with the lower end 5a of the trunk portion 5 by a lower peripheral wall portion 29 having a predetermined height. The lower peripheral wall portion 29 is formed in a curved shape so that the diameter gradually decreases toward the lower side in order to smoothly connect the body portion 5 and the bottom portion 6 having different sizes. The lower peripheral wall portion 29 can connect the bottom portion 6 having a circular shape in a bottom view as a whole to the trunk portion 5 having a circular cross section, and can also be smoothly connected to the trunk portion 5 having a rectangular cross section.

  The central portion 23 is a portion that is extended upward from the inner edge 21 b of the peripheral edge portion 21 and is raised as a whole and has a larger area than the peripheral edge portion 21. In other words, the central portion 23 has a circular shape as viewed from the bottom as a whole, and is a concave portion with respect to the installation surface 28 so that the central portion is farthest from the installation surface 28. In addition, depending on another embodiment, it is also possible to make the part which consists of the center part 23 and the peripheral part 21 into a bottom view square shape as a whole.

  The dome part 25 is a part formed at the rising apex part of the central part 23, and is formed concentrically with the central part 23 and with a smaller diameter than the central part 23. The dome portion 25 includes a top portion 31 and a peripheral wall portion 33 that protrude into the bottle 1. The top portion 31 is located at the uppermost position in the bottom portion 6 and continues to the upper end 33 a of the peripheral wall portion 33. The peripheral wall portion 33 is formed so as to expand slightly from the upper end 33 a to the lower end 33 b, and the lower end 33 b is continuous with the inner edge of the central portion 23.

  The plurality of concave grooves 27 are eight in total and extend so as to be radially centered on the dome portion 25 as a whole. The number of the concave grooves 27 can be appropriately changed from the viewpoint of the strength of the bottom portion 6, but is preferably at least two, preferably four or more. In addition, the plurality of concave grooves 27 may extend at equal intervals. Each concave groove 27 is formed over the central portion 23, the peripheral edge portion 21, and the lower peripheral wall portion 29, but no concave groove 27 is formed in the dome portion 25. That is, each concave groove 27 extends from one end 27 a in the central portion 23 to the other end 27 b in the lower peripheral wall portion 29 and crosses the peripheral edge portion 21 in the middle, but the one end 27 a Discontinuous.

  The other end 27 b is formed in the middle of the lower peripheral wall portion 29 in the height direction. By forming the other end 27 also on the lower peripheral wall portion 29, not only the strength of the lower peripheral wall portion 29 but also the strength of the corner portion of the lower peripheral wall portion 29 and the bottom portion 6 (that is, the outer edge 21a of the peripheral edge portion 21) is increased. Can be reinforced. However, in another embodiment, the other end 27 b may be positioned at the boundary between the lower peripheral wall portion 29 and the trunk portion 5. Alternatively, the other end 27 b may be positioned on the peripheral edge portion 21 without being positioned on the lower peripheral wall portion 29. For example, all of the plurality of concave grooves 27 may be formed only at the peripheral edge portion 21 and the central portion 23, or a part of the plurality of concave grooves 27 is formed only at the peripheral edge portion 21 and the central portion 23, The remaining at least one concave groove 27 may also be formed in the lower peripheral wall portion 29.

  The length, width, depth, and cross-sectional shape of each concave groove 27 can be designed as appropriate. For example, the width and depth of the concave groove 27 can be constant over the length direction. However, from the viewpoint of easy biaxial stretch blow molding in a lightweight bottle, it is preferable that at least one of the width and depth of the concave groove 27 is variable in the length direction. The reason will be explained. First, in the lightweight bottle, the amount of resin for the preform 10 is reduced. When the width or depth of the portion on the one end 27a side of the concave groove 27 is large, it is difficult to stretch the cylindrical portion 14 of the preform 10 with a small amount of resin. Therefore, in this embodiment, in order to ensure ease of molding in the lightweight bottle, at least one of the width and depth of the concave groove 27 on the one end 27a side, preferably both, are gradually increased toward the one end 27a. It is small. More specifically, the concave groove 27 is formed such that one end 27 c including one end 27 a has a spire shape, and the width and depth gradually increase toward a portion 27 d existing in the peripheral edge 21.

  Here, the lightweight bottle generally refers to a bottle in which the amount of resin used W (g) used in the bottle is reduced with respect to the capacity V (ml) of the bottle. In the present specification, a bottle having a W / V of 0.015 or more and 0.035 or less is defined as a lightweight bottle. This is because a bottle having a W / V exceeding 0.035 is no longer a “lightweight” bottle because the amount of resin used is large. Further, a bottle having a W / V of less than 0.015 has a small amount of resin used, so that the wall thickness becomes too thin to function as a bottle. The bottle 1 of the present embodiment is suitable for a lightweight bottle. As an example of the bottle 1, a capacity V is 500 ml, a resin usage W is 12 g, and W / V is 0.024.

An example of the dimensions of the concave groove 27 and the dome portion 25 in such a preferable example will be given.
First, the width and depth of the concave groove 27 are preferably 1 mm or more and 5 mm or less, and more preferably 3 mm. If it is less than 1 mm, the original reinforcing effect of the concave groove 27 cannot be expected. On the other hand, if it exceeds 5 mm, the thickness of the corner portion of the concave groove 27 becomes thin due to molding, and as a result, a difference occurs in the thickness of the concave groove 27, resulting in partial strength reduction. On the other hand, if it is 1 mm or more and less than 5 mm, it is easy to achieve both a reinforcing effect and good moldability. When the width and depth of the concave groove 27 are variable as described above, these dimensions may be set for the largest portion, and the one end 27a of the concave groove 27 is connected to the flat portion of the central portion 23 with almost no step. Good.

Next, the diameter of the dome portion 25 (the diameter on the upper end 33a side or the lower end 33b side of the peripheral wall portion 33) is preferably 7 mm or more. This is because the top portion 31 of the dome portion 25 is a portion to which the stretch rod is contacted in the biaxial stretch blow molding, and if the length of the portion is less than 7 mm, it becomes difficult to perform the molding.
The height of the dome portion 25 (that is, the distance between the top portion 31 and the lower end 33b of the peripheral wall portion 33) is preferably 1 mm or more. This is because stress concentration is unlikely to occur in the dome portion 25 if it is 1 mm or more.
The distance between the apex of the dome portion 25 and the installation surface 28, that is, the length L ₁ in the vertical direction between the top portion 31 and the peripheral portion 21 is preferably 6 mm or more and 15 mm or less, and more preferably 8 mm. . If it is less than 6 mm, the central portion 23 swells downward due to the internal pressure of the bottle 1 filled with a beverage, and the self-supporting stability of the bottle 1 decreases. On the other hand, if it exceeds 15 mm, the distance stretched from the top portion 31 during biaxial stretch blow molding becomes longer, so that the wall thickness of the peripheral edge portion 21 (particularly the wall thickness of the outer edge 21a) becomes thin and the strength decreases. . On the other hand, if it is 6 mm or more and 15 mm or less, it is easy to make self-supporting stability and good moldability compatible.

In addition, the distance L ₂ (see FIG. 3B) between the lower end 33b of the dome portion 25 and the one end 27a of the concave groove 27 is preferably 1 mm or more and 10 mm or less, and more preferably 3 mm. If it exceeds 10 mm, the central peripheral portion of the central portion 23 that is not reinforced due to the absence of the concave groove 27 becomes large, swells and deforms due to the internal pressure of the bottle 1 as described above, and the self-supporting stability of the bottle 1 decreases. . On the other hand, if it is less than 1 mm, a load propagating through a concave groove 27 described later reaches the lower end 33b of the dome portion 25, and therefore stress concentration at the dome portion 25 may not be effectively suppressed. On the other hand, if it is 1 mm or more and 10 mm or less, it is easy to achieve both self-supporting stability and suppression of stress concentration at the dome portion 25. From the viewpoint of the reinforcing effect by the concave groove 27, the distance L ₂ is preferably shorter than the length of the concave groove 27.

  The effect of the bottle 1 demonstrated above is demonstrated.

  FIG. 5 shows the periphery of the bottom of the bottle according to the comparative example, and the same reference numerals are attached to the same reference numerals for the same components as the bottle 1 of the present embodiment. The main difference from the bottle 1 is that the concave groove 27 ′ is also formed in the dome portion 25 ′ and that the depth and width of the concave groove 27 ′ are constant over the length direction. .

  FIG. 6 shows a case where the bottles 1 and 1 ′ in which the chilled beverages are stored are inclined and dropped. In the case of the bottle 1 ′ shown in FIG. 6A, the impact load from the collision point 40 ′ of the bottom 6 ′ that first contacts the installation surface 28 ′ is close to the collision point 40 ′ as indicated by the arrow 43 ′. It propagates through the concave groove 27 ′ and finally reaches the dome portion 25 ′. As a result, stress concentration occurs at the dome portion 25 '. The influence of this stress concentration becomes larger as the bottle 1 'has a smaller size, for example, a capacity of 500 ml. The dome portion 25 'is a portion that is not oriented and crystallized in the biaxial stretch blow molding, and therefore has a relatively low strength. Therefore, a crack occurs in the dome portion 25' due to stress concentration, and the commercial value of the bottle 1 'is increased. May lower.

  On the other hand, in the case of the bottle 1 shown in FIG. 6B, the impact load from the collision point 40 of the bottom portion 6 is transmitted directly through the concave groove 27 close to the collision point 40 but directly to the dome portion 25. Absent. This is because the concave groove 27 is formed so as not to reach the dome portion 25. In this case, since the impact load is alleviated in the entire central peripheral portion (non-concave groove portion) of the central portion 23 where the concave groove 27 does not exist, stress concentration in the dome portion 25 is suppressed. Thereby, generation | occurrence | production of the crack resulting from stress concentration is suppressed.

  As described above, according to the bottle 1 of the present embodiment, even when it is a lightweight bottle, durability against a drop impact can be improved while exhibiting the reinforcing effect of the bottom portion 6 by the concave groove 27. In particular, the above-described configuration of the present embodiment is useful for suppressing the propagation of the impact load to the dome portion 25 as the bottle 1 has a smaller capacity.

A modification of this embodiment will be described.
Unless the one end 27 a of the concave groove 27 is formed in the dome portion 25, the mode of the central portion 23 can be changed. For example, you may form the part of the center part 23 except the dome part 25 with a step. Further, an annular concave rib may be formed in the central portion 23, and the concave rib may cross a part of the concave groove 27.

  The plurality of concave grooves 27 can take a radial form as long as there are three or more, but the radial form may not be taken. Each concave groove 27 may be formed not only in a linearly extending manner but also in a manner in which a part thereof is curved and extended, for example, in a crescent shape as viewed from the bottom.

  1: bottle, 5: trunk, 6: bottom, 21: peripheral edge, 23: center, 25: dome, 27: concave groove, 27a: one end, 27b: other end, 27c: one end, 28: installation Surface, 29: lower peripheral wall part, 31: top part, 33: peripheral wall part

Claims (6)

In a cylindrical plastic bottle having a bottom formed by biaxial stretch blow molding,
The bottom is
A peripheral portion to be grounded when the plastic bottle is made self-supporting;
A central portion formed so as to protrude from the peripheral portion;
A dome portion formed so as to protrude higher in the central portion of the central portion;
Each of the plastic bottles includes a plurality of concave grooves that are formed over at least the peripheral edge portion and the central portion, but are not formed in the dome portion.   The relationship W / V between the capacity V (ml) of the plastic bottle and the amount of resin used W (g) used in molding the plastic bottle is 0.015 or more and 0.035 or less. Plastic bottle.   The plastic bottle according to claim 1 or 2, wherein the plurality of concave grooves extend so as to be radially centered on the dome portion as a whole.   4. The plastic bottle according to claim 3, wherein a distance between one end of each concave groove on the dome portion side and a lower end of the dome portion is 1 mm or more and shorter than the length of each concave groove.   5. The plastic bottle according to claim 3, wherein each of the concave grooves is formed such that at least one of a depth and a width of one end portion on the dome portion side gradually decreases toward the dome portion side. A tubular body,
A curved lower peripheral wall portion connecting the lower end of the body portion and the outer edge of the peripheral edge portion, and
The plastic bottle according to any one of claims 1 to 5, wherein at least one of the plurality of concave grooves is also formed in the lower peripheral wall portion.

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