US20100089863A1

US20100089863A1 - Plastic bottle with a mouth

Info

Publication number: US20100089863A1
Application number: US12/251,663
Authority: US
Inventors: Kenshi Matsuoka
Original assignee: Coca Cola Co
Current assignee: Coca Cola Co
Priority date: 2008-10-15
Filing date: 2008-10-15
Publication date: 2010-04-15
Also published as: WO2010045325A1; KR20100042242A; CN102186729A

Abstract

To provide a plastic bottle whose weight can be reduced without sacrificing strength of a bottle mouth, the plastic bottle is provided with a bottle mouth having a circumferential wall, including a threaded section formed on an outer circumferential surface of the circumferential wall, a support ring protruding from the outer circumferential surface below the threaded section, and punched sections formed on the circumferential wall.

Description

TECHNICAL FIELD

The present invention concerns the structure of a mouth of a plastic bottle.

BACKGROUND

Plastic bottles represented by PET bottles are produced through biaxial stretching of preforms that are formed through injection molding, etc. In recent years, reduction in the weight of plastic bottles has proceeded out of concerns that include resource conservation and cost reduction. The strength of the bottle must be maintained for its commercial value when reducing its weight.
Japanese Kokai Publication Hei-2001-113589 discloses a bottle in which the body section and shoulder of the bottle overall are thinner while the strength is maintained by reserving essential thickness of the bottle mouth. A threaded section for screw tightening of the cap is formed to protrude at the mouth of the bottle, and a flange-shaped support ring is formed to protrude below the threaded section.
Japanese Kokai Publication Hei-2004-26201 and Japanese Kokai Publication Hei-2008-143588 discuss a bottle in which the tamper evidence is maintained. A bead ring is formed between the threaded section and the support ring in the mouth of such a bottle. The tamper evident band is severed from the entire cap when the cap is manipulated to open this type of bottle, and it is ultimately held so as not to be detached via the bead ring and the support ring.
In recent years, a desire has arisen for weight reduction of the mouth as well from the perspective of resource conservation. Heat resistance is imparted through hot crystallization processing so that the mouth of the bottle disclosed in Japanese Kokai Publications Hei-2004-26201 and Hei-2008-143588 does not deform due to hot fill packing, but this does not contribute to weight reduction. Furthermore, Japanese Kokai Publication Hei-2001-113589 merely discusses weight reduction of the body section but does not adequately reduce the weight of the mouth. In fact, while the body section of the bottle exemplified in Japanese Kokai Publication Hei-2001-113589 is 0.5 mm thick, the mouth is very thick, at 2.2 mm.
If the same method as that applied to the body section were adopted to reduce the weight of the bottle mouth as stated in Japanese Kokai Publication Hei-2001-113589, the strength would decline markedly because the overall mouth would become too thin. Consequently, there is a risk of deformation or splitting of the mouth upon manipulation of the cap to open the bottle. Furthermore, there is a risk of the mouth part that is set in a chuck (for example, the circumferential wall section between the support ring and the bead ring in Japanese Kokai Publications Hei-2004-26201 and Hei-2008-143588) being damaged or the tamper evidence suffering damage if the mouth is set in a chuck in the course of bottle production prior to capping.

SUMMARY

The objective of the present invention is to provide a plastic bottle in which the weight of the bottle mouth can be reduced without sacrificing the strength.
A plastic bottle is provided with a bottle mouth having a circumferential wall, including a threaded section formed on an outer circumferential surface of the circumferential wall, a support ring protruding from the outer circumferential surface below the threaded section, and punched sections formed on the circumferential wall.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an exemplary embodiment of the invention and together with the description, serve to explain the principles of the invention.

FIG. 1 is a front view of a plastic bottle pursuant to an embodiment;

FIG. 2 is an oblique view showing enlargement of the mouth of the plastic bottle of FIG. 1;

FIG. 3 is a front view of the mouth of FIG. 2;

FIG. 4 shows a semi-cutaway view showing the state of closure of the mouth shown in FIG. 2 by a cap; and

FIG. 5 shows a cross-sectional view cut along line V-V in FIG. 3.

DETAILED DESCRIPTION

Reference will now be made in detail to an exemplary embodiment of the invention, which is illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
In one embodiment, a plastic bottle is provided with a bottle mouth having a circumferential wall, including a threaded section formed on an outer circumferential surface of the circumferential wall, a support ring protruding from the outer circumferential surface below the threaded section, and punched sections formed on the circumferential wall.
Since the thickness is reduced in a section in the present invention, the weight can be reduced without sacrificing strength of the bottle mouth in comparison to uniform reduction of the thickness. Furthermore, obstruction of resin fluidity during formation of the bottle mouth is inhibited and the preform molding properties are not damaged.
Preferably, the punched sections would be positioned away from the threads of the threaded section and from the support ring.
More preferably, the punched sections would be positioned between the threaded section and the support ring. By so doing, the thickness would be greater and the weight could be reduced while keeping strength in mind since sections are punched out between the threaded section and the support ring.
Here, use of the following structure would be desirable when the bottle mouth is opened by a cap fitted with a releasable tamper evident band. Specifically, a bead ring should protrude at a position away from the punched section between the threaded section and the support ring on the outer circumferential surface of the circumferential wall. Furthermore, when the bottle mouth is opened by manipulating the cap, the tamper evident band would be severed and would then fall onto the support ring where it should remain on the bottle mouth so as not to be detached via the bead ring and the support ring.
The weight of even a bottle that has tamper evidence can be reduced by punching with such a structure.
More preferably, a maximum diameter section that has a maximum diameter outer circumferential surface at the bottle mouth among the outer circumferential surfaces of the circumferential wall should be provided at the lower edge on the base side of the bead ring as a section engaged by the tamper evident band when the bottle mouth is opened by the cap. The punched sections may be formed from the lower lip of the maximum diameter section to the upper lip of the support ring at the outer circumferential surface of the circumferential wall.
The tamper evidence can be maintained since the strength of the section engaged by the tamper evident band is secured in such a structure. Furthermore, chuck engagement is possible without modifying existing production facilities since the maximum diameter section is located where the chucking is generally engaged in the course of production. Moreover, existing specifications can be used by any shape of the part of the tamper evident band (for example, the tab discussed below) since a maximum diameter section is present. In addition, a die can be easily opened for injection molding in comparison to formation on the inner circumferential surface of the circumferential wall since punched sections are formed on the outer circumferential surface of the circumferential wall.
More preferably columnar sections having the same maximum diameter as that of the maximum diameter section should be formed between the maximum diameter section and the support ring adjacent to the punched sections and the maximum diameter section. The difference between the maximum diameter at the maximum diameter section and the minimum diameter in the punched sections should be not more than 3.0 mm.
Sections that can be engaged by a chuck can be broadly secured stably in such a structure since the columnar sections having the same diameter as the lower side of the maximum diameter section can continue on a given surface. Furthermore, the fluidity of resin can be secured during injection molding of the bottle mouth by setting aforementioned maximum value (3.0 mm). Conversely, there is a high possibility of resin not reaching the columnar sections, resulting in molding failure, when the maximum value is exceeded.
In a separate mode, the punched sections would be formed in line symmetry at uniform intervals in the circumferential direction, and columnar sections having the same maximum diameter as that of the maximum diameter section would be formed adjacent to the maximum diameter section between mutually adjoining punched sections.
Since a plurality of columnar sections in addition to the punched sections have line symmetry in such a structure, centering is easily completed when setting columnar sections in chucks. An additional advantage is that molding balance is improved during injection molding of the bottle mouth because of line symmetry, and molding failure does not occur when opening the die because injection molding is employed.
In another example, the sections that connect each of the punched sections and the columnar sections would adopt an arc whose curvature radius R centers on the inside of the bottle mouth. Damage to the connecting sections accompanying engagement on a chuck can easily be inhibited in such a structure.
In another embodiment, the transverse section of the punched sections would be arc shaped. For example, the concentration of stress at the punched sections due to force in the inward direction of the bottle mouth would occur less in comparison to a trapezoidal shape.
Also, the threaded section may have at least one continuous thread strip about the outer circumferential surface of the circumferential wall. By so doing, the reinforcing effect of the mouth due to the threaded section could be enhanced in comparison to the use of a three strip screw or in comparison to a single non-continuous thread strip having a bent slot or a single strip that does not complete one rotation of the outer circumferential surface of the circumferential wall.
The thickness of the section of the circumferential wall of the bottle mouth where the threaded section is present may be thinner than the thickness of the section below the threaded section. In one example, the thickness of the section of the circumferential wall of the bottle mouth where the threaded section is present may be more than or equal to 0.8 mm and less than or equal to 1.3 mm. Deformation and cracking can be inhibited even with thin pieces since a reinforcing effect is attained with one thread strip in a piece that is thin in order to reduce weight.
The plastic bottle is explained in an embodiment of the present invention with reference to the appended figures. In the following explanation, the direction where the bottle mouth is present is up and the direction where the bottle base is present is down. The height signifies the length along the central axial direction (vertical direction) of the bottle. The transverse section shape represents the transverse section shape along the plane (transverse plane) orthogonal to the central axis.
Plastic bottle 1 (hereinafter abbreviated “bottle 1”) has mouth 2, shoulder 3, body section 4, and base 5 from the top, as shown in FIG. 1. These sections (2, 3, 4, and 5) are formed integrally, and include the bottle wall for holding a beverage within. The beverage could be any non-carbonated beverage including water, green tea, or fruit juice. However, the liquid packed in bottle 1 in other embodiments may be a carbonated beverage or food such as a sauce.
Bottle 1 may consist primarily of thermoplastic resin such as polyethylene, polypropylene, or polyethylene terephthalate, and it may be molded by stretch molding such as biaxial stretch blow molding.
One example of the course of bottle production is explained. First, thermoplastic resin is injected into a die to complete injection molding of a preform. This preform has a mouth having exactly the same shape as that of mouth 2 and a tubular section having a bottom that is connected below the mouth. Injection molding is followed by opening the die for the mouth in the transverse direction, opening the die for the tubular section in the vertical direction, removing the preform and then setting it in a blow molding apparatus. Only the tubular section of the preform is heated in the blow molding apparatus, the tubular section is stretched in the vertical direction by a stretching rod, and the tubular section is stretched in the transverse direction by blowing in compressed air to complete formation of shoulder 3, body section 4, and base 5. Serial molding of bottle 1 is completed by so doing. Subsequently, the bottle is washed, disinfected, and packed with a beverage. Mouth 2 that functions as the injection orifice for the beverage is then sealed with cap 6 (See FIG. 3).
Mouth 2 has cylindrical circumferential wall 10 that opens upward, as shown in FIGS. 2 to 4. Inner circumferential surface 12 of circumferential wall 10 extends without bumps in the vertical direction. On the other hand, threaded section 16, bead ring 18, and support ring 20 protrude on outer circumferential surface 14 of circumferential wall 10. Threaded section 16 exists over the upper half of circumferential wall 10 while bead ring 18 and support ring 20 exist below threaded section 16 at a predetermined separation.
Threaded section 16 can use either two thread strips or three thread strips, but a single thread strip, which is more difficult to loosen and which has higher strength, is structured in this embodiment. The thread crest of threaded section 16 continues at a single height in the lengthwise direction without formation of a so-called bent slot. The length of the thread crest should be more than one rotation of outer circumferential surface 14, specifically, the effective angle should exceed 360°. Here, that would be approximately 720° (for example, 650° for the complete threaded section +70° for the partial threaded section), which is about the length of two circumferences.
Bead ring 18 and support ring 20 protrude outwardly over outer circumferential surface 14 in the circumferential direction. Top 3 a of shoulder 3 is linked to the lower edge of support ring 20 on the base side (See FIG. 4). Bead ring 18 and support ring 20 are also denoted by different terms (for example, flange section, etc.).
Here, seen from the perspective of the magnitude of the thickness of circumferential wall 10, circumferential wall 10 has thin section 10 a and thick section 10 b that is thicker than thin section 10 a, as shown in FIG. 4. Thin section 10 a is the tubular section wherein lies threaded section 16 on the outer circumferential surface while thick section 10 b is the tubular section below threaded section 16. Bead ring 18 exists on the upper edge of thick section 10 b while support ring 20 exists on the lower edge of thick section 10 b. Thin section 10 a and thick section 10 b each have uniform thickness in the vertical direction (See FIG. 4).
The size of each thickness of thin section 10 a and thick section 10 b should satisfy the required strength for mouth 2 overall. When considering the thickness of one, the thickness of the other is determined. In general, since many parts of the circumferential wall between bead ring 18 and support ring 20 are held in chucks in the course of production of bottle 1, the strength must be secured relative to the chucks. In light of this point, mouth 2 in the embodiment secures the strength by constructing the circumferential wall section in question from thick section 10 b while the remaining circumferential wall section is structured from thin section 10 a while maintaining consideration of the securing of strength. The reinforcing effect of thin section 10 a is enhanced by structuring threaded section 16 that exists on thin section 10 a from a single continuous thread strip.
In one example of the dimensions in this structure, the thickness of thick section 10 b preferably would be approximately 2.0 mm while the thickness of thin section 10 a preferably would be 0.8 mm or more and not more than 1.3 mm, more preferably 1.0 mm or more and not more than 1.2 mm. Securing the strength of thin section 10 a solely through the reinforcing effect of threaded section 16 becomes difficult when the thickness of thin section 10 a is under 0.8 mm, but the molding cycle increases and the production efficiency of the preform declines. On the other hand, weight reduction of mouth 2 becomes insufficient when the thickness of thin section 10 a exceeds 1.3 mm. Both securing the strength and weight reduction are realized by setting the thickness of thin section 10 a at 1.0 mm or more and not more than 1.2 mm.
The structure of the punched sections of thick section 10 b whose weight has been reduced by partial thickness reduction is explained next. The punched structure becomes effective through combination with aforementioned structure (demarcating circumferential wall 10 vertically between thin section 10 a and thick section 10 b), but weight reduction is attained even when not combined (specifically, when the thickness of circumferential wall 10 is constant in the vertical direction).
Thick section 10 b has maximum diameter section 22 on the lower edge on the base side of bead ring 18, and a plurality of punched sections 24 as well as a plurality of columnar sections 26 are found on the lower side of maximum diameter section 22. Maximum diameter section 22 is the tubular section with the outer circumferential surface of maximum diameter in outer circumferential surface 14 of circumferential wall 10. For example, it has a height of 1.4 mm. Columnar section 26 is the section having the same maximum diameter and thickness as that of maximum diameter section 22. It continues on a given surface of maximum diameter section 22. Connection section 28 that connects punched section 24 and columnar section 26, as shown in FIG. 5, adopts an arc whose curvature radius R centers on the inside of mouth 2 so as to connect the two in a gently-sloping manner.
A plurality of punched sections 24 are formed on outer circumferential surface 14 with line symmetry at uniform intervals in the circumferential direction from the lower lip of maximum diameter section 22 to the upper lip of support ring 20. Then, columnar sections 26 are formed between adjoining punched sections 24, 24. A total of eight punched sections 24 and columnar sections 26 are alternately aligned in this embodiment, but the number is not restricted to eight.
As shown in FIG. 5, the transverse section shape of punched section 24 has an arc shape curving to the inward direction of mouth 2. R (radius of curvature) of the arc shape of punched section 24 should be in the range of 5 to 50 mm, preferably 30 mm. Undercutting occurs since it is too small when R is under 5 mm, and removal of the preform from the die becomes more difficult. Conversely, an adequate effect of punching for weight reduction is not attained since R is excessively large when it exceeds 50 mm.
The center of punched section 24 is thinnest and it gradually thickens toward both edges. The thinnest section has the section of smallest diameter in punched section 24. The thickness can be equal or equivalent to the thickness of aforementioned thin section 10a. However, the minimum thickness of punched section 24 need not be equivalent to the thickness of thin section 10 a so long as fluidity of resin as well as strength can be secured during molding. The difference between the smallest diameter of punched section 24 and the maximum diameter of maximum diameter section 22 should be not more than 3.0 mm at the diameter, preferably in the range of 1.5 mm to 2.0 mm. Thermoplastic resin may not reach both edges of punched section 24 during injection molding of the preform when it exceeds 3.0 mm. Conversely, the flow of thermoplastic resin during injection molding is not obstructed and molding failure can be avoided if it is not more than 3.0 mm.
Next, cap 6 is explained with reference to FIG. 4.
Cap 6 fits on mouth 2 through rotational manipulation to close the aperture of mouth 2. Cap 6 need not have a tamper evidence property (a function of displaying fraudulent opening), but a tamper evidence property is present in the example explained here.
Cap 6 has cap body 30 and tamper evident band 32. Cap body 30 has round cover section 36 that covers the top of mouth 2 and cylindrical section 38 that covers the sides of mouth 2. Cylindrical section 38 is the section that extends down from the peripheral edges of cover section 36. Threaded section 40 that engages threaded section 16 of mouth 2 is formed on the inner circumferential surface of cylindrical section 38.
Tamper evident band 32 is connected to the lower edge of cylindrical section 38 via severable bridge 42. Tab 44 (engagement section) facing up and inward is formed on the lower inner surface of tamper evident band 32. Tab 44 engages steps that are demarcated by bead ring 18 and maximum diameter section 22.
Removal of cap 6 is prevented by tab 44 that engages bead ring 18 and maximum diameter section 22 in the closed state of mouth 2 by cap 6 shown in FIG. 4. In this state, when cap 6 is turned in the direction of opening, bridge 42 is broken, tamper evident band 32 is severed from cap body 30, and it falls onto the upper surface of support ring 20. The upper edge portion of tamper evident band 32 that had fallen then rests on bead ring 18 and it is held so as not to readily release in the vertical direction by support ring 20 and bead ring 18. In further detail, the downward movement of tamper evident band 32 that remains on mouth 2 after opening is controlled by support ring 20 while its upward movement is controlled by tab 44 that contacts bead ring 18.
Exemplary operating effects of mouth 2 of bottle 1 in the embodiment explained here are explained below.
1. Perspective of Strength and Weight Reduction
Punched sections 24 are formed to partially reduce the thickness of those sections that are often thick in consideration of application of a chuck (the circumferential wall section from bead ring 18 to support ring 20). By so doing, even while weight reduction is realized, the strength of mouth 2 is not sacrificed in comparison to the case in which the overall thickness is reduced. Furthermore, the overall weight of mouth 2 can be reduced while preventing deformation or cracking of thin section 10 a, as stated above, since thin section 10 a, which has a reinforcing effect, is set in mouth 2.
Furthermore, a part having the same thickness as that of the existing mouth can be partially left in mouth 2 since maximum diameter section 22 is found at the section that engages tamper evident band 32. Tamper evident properties can be maintained and an existing cap 6 can be used since the strength of maximum diameter section 22 is secured by so doing.
Furthermore, the concentration of stress at the punched sections 24 due to force acting in the inward direction of mouth 2 accompanying depressurization within 1 would not readily occur since the transverse section shape of punched section 24 is an arc shape. Similarly, even if bottle 1 is pressurized through filling with a carbonated beverage, the concentration of stress at punched section 24 would be resisted. Accordingly, decline in the strength of punched section 24 can be inhibited in comparison to the case in which the transverse section has a trapezoidal shape.
2. Perspective of Chuck Application
Mouth 2 is set on a chuck when a preform is moved along a blow molding apparatus in the course of production of bottle 1. Even if existing production facilities are used unchanged, chucks may be used without deformation of mouth 2 since maximum diameter section 22 is present at the part that the chucking is engaged in many cases.
Furthermore, chuck application can proceed stably even if the chuck should shift in the vertical direction since columnar section 26 continues without steps on the lower side of maximum diameter section 22. In other words, columnar section 26 itself can be utilized as a part that has a chuck applied. Furthermore, centering is easy when columnar section 26 is set on a chuck since a plurality of columnar sections 26 are disposed with line symmetry. In addition, scratching when a chuck is applied can be inhibited since connection section 28 positioned at both edges of columnar section 26 has a radius of curvature R.
3. Perspective of Fluidity of Thermoplastic Resin and Die Release
The fluidity of thermoplastic resin during injection molding of preforms affects the productivity of bottle 1. The fluidity of resin to form punched section 24 is easily secured since punched section 24 is punched in arc shape. Furthermore, obstruction of molding properties during molding of mouth 2 is readily prevented since thick sections are uniformly installed in the direction of resin flow. In addition, opening of the die for mouth 2 in the transverse direction is facilitated since punched sections 24 are formed on outer circumferential surface 14 of circumferential wall 10, in comparison to their formation on inner circumferential surface 12 of circumferential wall 10. Furthermore, the molding balance is improved and mold failure is inhibited when opening the die in the transverse direction since the disposition of punched section 24 and columnar section 26 is in line symmetry. Accordingly, the productivity of bottle 1 can be enhanced.
The design of the structure of aforementioned mouth 2 can be suitably modified so long as it does not deviate from the scope of the present invention. For example, punched section 24 can be formed on the upper side of bead ring 18 instead of on the lower side of bead ring 18. Furthermore, punched sections 24 can be formed in the section that extends outward from the thread crest of threaded section 16, specifically, in the circumferential wall sections of spiral shape between adjacent thread crests. Alternately, punched section 24 may partially engage the end of the thread crest of threaded section 16. These cases would be ideal applications to the formation of circumferential wall 10 of mouth 2 at a single thickness. Furthermore, punched sections 24 can be formed on inner circumferential surface 12 or outer circumferential surface 14 of circumferential wall 10, but formation on outer circumferential surface 14 would be preferable from aforementioned perspective of ease of removal from a die. In addition, heat resistance can be imparted to mouth 2 through heat treatment of mouth 2 involving hot crystallization.
It will be apparent to those skilled in the art that various modifications and variations can be made in the plastic bottle of the present invention without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

1. A plastic bottle, comprising:

a bottle mouth having a circumferential wall, including:

a threaded section formed on an outer circumferential surface of the circumferential wall;

a support ring protruding from the outer circumferential surface below the threaded section; and

punched sections formed on the circumferential wall.

2. The plastic bottle of claim 1, wherein the punched sections are positioned away from threads of the threaded section and from the support ring.

3. The plastic bottle of claim 2, wherein the punched sections are positioned between the threaded section and the support ring.

4. The plastic bottle of claim 3, wherein the bottle mouth is sealed by a cap fitted with a releasable tamper evident band, and wherein the outer circumferential surface is provided with a bead ring protruding at a position away from the punched sections between the threaded section and the support ring, the tamper evident band being configured to be severed and dropped onto the support ring when the bottle mouth is opened by manipulating the cap and to remain on the bottle mouth by the bead ring and the support ring.

5. The plastic bottle of claim 4, wherein the bottle mouth is provided with a maximum diameter section having the largest diameter at the outer circumferential surface below a base side of the bead ring, the maximum diameter section being configured to be covered by the tamper evident band when the bottle mouth is sealed by the cap, and wherein the punched sections are formed on the outer circumferential surface from a lower edge of the maximum diameter section to an upper edge of the support ring.

6. The plastic bottle of claim 5, wherein columnar sections having the same maximum diameter as the diameter of the maximum diameter section are formed between the maximum diameter section and the support ring adjacent to the punched sections and the maximum diameter section, wherein a difference between the maximum diameter in the maximum diameter section and the minimum diameter in the punched sections is not more than 3.0 mm.

7. The plastic bottle of claim 5, wherein the punched sections are formed in line symmetry at uniform intervals in the circumferential direction, and the columnar sections having the same maximum diameter as the diameter of the maximum diameter section are formed adjacent to the maximum diameter section between two adjacent ones of the punched sections.

8. The plastic bottle of claim 4, wherein sections connecting each of the punched sections and the columnar sections are etched with an arc having a center of a radius of curvature located inside of the bottle mouth.

9. The plastic bottle of claim 3, wherein each of the punched sections has an arced cross-sectional shape.

10. The plastic bottle of claim 3, wherein the threaded section includes at least one continuous thread strip around the outer circumferential surface of the circumferential wall.

11. The plastic bottle of claim 10, wherein the bottle mouth has a wall thickness at the threaded section thinner than a wall thickness at a section below the threaded section.

12. The plastic bottle of claim 1, wherein the plastic bottle is formed by a biaxial stretching blow molding.