Patent Application
20120181246
The present invention is directed to plastic bottles used to contain foods and beverages that are filled and capped at an elevated temperature of at least 160° F., and more typically about 185° F. The present invention is particularly directed to such plastic bottles that are devoid of any vacuum panels in the body and shoulder areas.
Lightweight, thin-walled containers made of thermoplastic materials such as polyester resin are well known in the container industry. For example, polyethylene terephthalate (PET) has a wide range of applications in the field of containers for foodstuffs, flavoring materials, cosmetics, beverages, and so on. PET can be molded, by orientation-blowing, into transparent thin-walled containers having a high stiffness, impact strength and other improved qualities with a high molding accuracy. In the past, some cold-filled carbonated bottles have employed chimes having additional material at the standing ring surface. The formation of such bottles requires either heavy material distribution to blow out the ring or some other non-standard forming process. Examples of such bottles are to be found in U.S. Pat. Nos. 4,780,257; 4,889,752; and 4,927,679. At elevated temperatures, however, such a thickened chime will soften and roll out so such a base is unsuitable for hot-filling.
Strong, transparent and substantially heat resistant containers may be produced by the biaxial-orientation blow-molding process in which a parison is oriented both laterally and longitudinally in a temperature range suitable for such orientation. Heat-set PET containers are particularly heat resistant. Biaxially-oriented blow-molded containers have greater stiffness and strength as well as improved gas barrier properties and transparency. Areas of thick accumulations of material, such as the thickened chimes discussed above, may not be sufficiently oriented to achieve the desired stiffness and strength to resist movement when subjected to hot-filling operations. The desirability of avoiding areas having accumulations of material for bottles intended for use in hot-filling operations is suggested generally by U.S. Pat. Nos. 5,585,065 and 5,735,420. However, both these patents resort to an extensive multi-blow heat-treating operation to achieve the desired product.
Garver et al., U.S. Pat. No. 5,067,622, discloses a bottle made of PET that is expressly configured for hot filled applications. The bottle's body sidewall is rigidized against radial and longitudinal vacuum distortion so that paper labels can be applied to the bottle. The rigidized sidewall is achieved by providing a plurality of radially inward, concave ring segments which are spaced apart from one another and separated from one another by cylindrically shaped flats or land segments. In addition, the amorphous threaded mouth of the bottle is rigidized by gussets molded into the bottle at the junction of the neck and shoulder portion of the bottle to resist deformation when the bottle is capped. To accommodate the post capping vacuum, a bulbous vacuum deformation area is provided in the shoulder adjacent the bottle neck, a plurality of vacuum deformation panels are provided in a frusto-conical portion of the shoulder, and a further vacuum deformation panel is provided in the base. As a result, any post capping vacuum is confined to the specifically designated areas of the bottle and the sidewall remains undistorted. The lack of post capping sidewall distortion is disclosed to be the result of a critical sizing of the ring segments relative to the land segments in combination, to some extent, with the crystallinity level, which is disclosed to be greater than 30%. Other bottles made of PET that have sidewall including spaced ring segments designed to rigidize the sidewall are disclosed, for example, in U.S. Pat. Nos. 6,929,139; 7,051,890 and 7,296,701. Other bottles made of PET that have vacuum responsive panels in the sidewall are disclosed, for example, in U.S. Pat. Nos. 5,704,503; 6,932,230; and 7,243,808.
In the bottles referenced above, the land segments between the spaced indented ring segments are generally formed as right cylindrical or flat surfaces having a constant radius from a vertical axis of the bottle. Such flat surfaces generally perform satisfactorily when the indented ring segments are sufficiently close together. However, the sidewall can experience reduced satisfactory performance when the ring segments become increasingly spaced from each other so that the intervening lands can individually experience an inward deformation resulting in a concavity or crease. As a result, the vertical extent of each of the lands is generally minimized to diminish the area that might be subject to such a concave inward deformation, also known as localized paneling. Additionally, special shapes and relationships have also been adopted for the indented ring segments to minimize the opportunity for such a concave inward deformation of a land portion, which can result in a rippled appearance for any covering label.
Another problem with bottles having a series of indented ring segments with land segments therebetween is the tendency to fail by ovalization under vacuum pressures. Depending on the configuration of the indented ring and transition to each land segment, portions of the indented ring may tend to move radially outward, while other portions of the same indented ring may tend to move radially inward, resulting in a cross-section that appears to be more oval than circular. Ovalization of bottles not only increases the risk of failure, but also can lead to unaesthetic looking bottles. Other attempts have been made to increase the number of indented ring segments along the sidewall. While each indented ring added ridgidizes the sidewall to reduce the risks associated with ovalization and localized paneling, the bottle often experiences axial shortening or compression, like an accordion, for each additional indented ring. This is problematic because it can inhibit the vertical stacking of bottles on top of each other and possibly distort or even tear the label affixed to the sidewall due to such axial movement.
Accordingly, it is an object of the present invention to form a plastic bottle with a sidewall having a plurality of spaced indented ring segments separating lands that will resist any tendency toward ovalization. It is a further object of the present invention to form a plastic bottle with a sidewall having a plurality of spaced indented ring segments that are sized in relation to the lands separated by the ring segments so that the lands will resist any tendency toward a concave inward deformation. It is a further object of the present invention to form a plastic bottle with a sidewall having lands with a preferred geometry and maximum size to further separate indented ring segments to maximize the vacuum resistance of the plastic bottle to ovalization and/or localized paneling.
A molded plastic bottle in its pre-hot fill state can have a base surrounding a vertical axis that is responsive to changes in pressure and vacuum with the bottle. A sidewall can have a lower edge that is coupled to the base. The sidewall can extend upward from the base to a sidewall upper edge. The sidewall can be devoid of any vacuum responsive panels. A shoulder portion can be coupled to the sidewall upper edge. The shoulder portion can lead upward and radially inward to a neck portion. The shoulder portion can also be devoid of any vacuum responsive panels. A finish can be coupled to the neck portion adapted to receive a closure. The finish can surround an opening leading to the plastic bottle interior. The various portions of such a plastic bottle can be molded in a single integral unit by various processes, including two-step reheat stretch blow molding of a preform within a mold defining the outside surface of the various bottle portions.
In one aspect, the base of the plastic bottle can have a continuous seating ring surrounding the vertical axis at a fixed radius. The base can also have at least a first inner surface coupled interiorly to the continuous seating ring that extends upwardly and inwardly from the continuous seating ring. The base can also have a diaphragm surface coupled exteriorly to the continuous seating ring. The diaphragm surface can include an inner edge extending upwardly and outwardly from the continuous seating ring. The diaphragm surface can also include an outer edge extending substantially horizontally outwardly. The base portion can also include a heel portion joining the diaphragm outer edge to the sidewall lower edge. The diaphragm surface can flex upward in response to any drop of pressure within the bottle. Given a sufficient drop in pressure, the diaphragm surface can flex upward at least until the continuous seating ring is situated above the heel portion.
In another aspect, the sidewall of the plastic bottle can be molded to have an outer surface having at least one land segment bounded by vertically spaced indented ring segments. Each land segment can be defined by a vertical arc rotated around the vertical axis to form an outwardly curved surface or outwardly bowed barrel-shaped surface having an outermost surface defining a maximum label diameter DL of the bottle. Each land segment can be formed to resist any tendency toward a concave inward deformation in response to any drop of pressure within the bottle. The distance between the vertical axis and the closest point on the indented ring segments to the axis can be between about 0.8 and 0.9 times the maximum distance between the vertical axis and the outermost surface of the land segments. The vertical dimension of the land segments can be such that there are only two of the land segments and three of the indented ring segments between the sidewall lower edge and the sidewall upper edge. The vertical dimension of each land segment can be at least 0.49 DL. The vertical arc that forms the outwardly curved surface of each land segment can have a vertical radius RA of up to 2.45 DL. The indented ring depth can be a depth of at least 0.08 DL. The vertical radius RB of the inwardly curved surface of the indented ring segments can be up to 0.02 DL. The plastic bottles preferably molded in its pre-hot fill state to have a sidewall geometry with one or more of the aforementioned ratios, such that the plastic bottle can be a lighter weight and/or can have a reduced number of indented ring segments, while having a satisfactory vacuum resistance to localized paneling and/or ovalization.
Other features of the present invention and the corresponding advantages of those features will become apparent from the following discussion of the preferred embodiments of the present invention, exemplifying the best mode of practicing the present invention, which is illustrated in the accompanying drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views.
A bottle 10 is shown in
A base 12, shown in detail in
The base 12, as shown in detail in
The post capping vacuum, which develops as the product-filled bottle cools from the filling temperature to an ambient or even refrigerated temperature, causes the inner portion 40 of the base 12 to move vertically upward along axis Y. The upward movement of the inner portion 40 causes the diaphragm portion 38 to flex from the position shown in
With reference to
The indented ring segments 64 can have arcuate shoulder portions 70 and 72 with a vertical radius RBL separated by a concave ring portion 74 defined by a vertical radius RB. The vertical radii RB and RBL are generally much smaller in absolute value than the vertical radius RA. In one embodiment, the absolute value of the vertical radius RB can be from 0.2% to 1.4% of the absolute value of the vertical radius RA, and the absolute value of the vertical radius RBL can be from 1% to 6.5% of the absolute value of the vertical radius RA and can be greater than RB. The vertical radius RB can be less than or equal to 0.02 DL. The transition 76 from the upper most or lower most indented ring to the respective sidewall upper or lower edges 18, 16 can also be arcuate with a vertical radius RT typically greater than the vertical radius RBL, having an absolute value from 1.5% to 7% of the absolute value of the vertical radius RA. Angle a is the inflection angle of the indented ring segment measured from a horizontal axis that is perpendicular to the vertical axis Y. Angle α can be 0° to about 25° (preferably 20°), with a smaller angle providing more sideload resistance and ovalization resistance.
In another embodiment, the distance DR between the vertical axis Y and the closest point 77 on the indented ring segments 64 to the axis Y can be between about 0.8 and 0.9 times the maximum distance DS between the vertical axis Y and the outermost surface 68 of the land segments 62. The difference between distances DR and DS is known as the ring depth 78 of the indented ring segment 64 relative to the outermost surface 68. A greater ring depth 78 can provide more resistance to ovalization. The ring depth 78 can be equal to or greater than 0.08 DL. The effective ring depth 79 is the distance from the closest point 74 of the indented ring segments 64 to the axis Y to a point 80 that is defined as the outward tangent point of the vertical radius RBL.
The vertical dimension HL is the label panel height measured from the top of the upper most indented ring segment to the bottom of the lower most ring segment, or alternatively, between the steps 20, 22 that define the edges of the label panel 21. The vertical dimension HS of the land segments 62 can be equal to or greater than 0.49 DL. In the illustrated embodiments, the vertical dimension HS of the land segments 62 can be such that there are only two of the land segments 62 and three of the indented ring segments 64 between the sidewall lower edge 16 and the sidewall upper edge 18. It will be appreciated, however that a few additional land segments 62 and indented ring segments 64 could be included having the same described character without departing from the central concept of having only a small number, no more than five, of such land segments 62 separated by the requisite number of indented ring segments 64 to define the sidewall 14. However, in some instances it is preferred to at least minimize the number of indented ring segments and maximize the size of the land segments. For every indented ring segment included in the sidewall, the bottle can undesirably become axially shorter after cooling, and the bottle may have an increase axial springiness, like an accordion. This is problematic because it can inhibit the vertical stacking of bottles on top of each other and possibly distort or even tear the label affixed to the sidewall due to such axial movement. Maximizing the size of the land segments can increase the surface area contact for the label to affix to and may even be more aesthetically pleasing.
Plastic bottles similar to the illustrated embodiments in
Bottles with a 3-inch label height HL were analyzed at various vertical radii RA: 2.069 inches; 2.713 inches; 4.3 inches; 7 inches; and 1000 inches. Bottles with a 3.22-inch label height HL were analyzed at various vertical radii RA: 5.954 inches; 7 inches; 8.388 inches; and 10.812 inches. Bottles with a 3.44-inch label height HL were analyzed at various vertical radii RA: 5.954 inches; 7 inches; 8.388 inches; and 1000 inches. Bottles with a 3.67-inch label height HL were analyzed at various vertical radii RA: 4.3 inches; 5.954 inches; 7 inches; 8.388 inches; 10.812 inches; and 1000 inches. Bottles with a 4.5-inch label height HL were analyzed at various vertical radii RA: 4.3 inches; 5.954 inches; 7 inches; 8.388 inches; 11.899 inches; and 1000 inches. Bottles with a 5-inch label height HL were analyzed at various vertical radii RA: 4.3 inches; 5.954 inches; 7 inches; 8.388 inches; and 1000 inches. Bottles with a 1000-inch vertical radius RA represent substantially flat land segments. The bottles were held in a fixed location along the neck, while the internal vacuum pressure was increased from 0 psig to negative 20 psig. During the analysis, the temperature of the material was maintained at about 72 degrees F. The vacuum was increased until one of two failures occurred: localized paneling along the land segments, or ovalization along the indented ring segments. The vacuum pressure at the instance of failure was then recorded for each bottle.
It was surprising that the bottles, across most of label heights HL, had superior vacuum resistance performance at approximately the same vertical radius RA of about 7 inches. According to the graph 100, there may also be a more preferred aspect ratio (label height HL to label diameter DL), as the vacuum resistance noticeably changes between the 3.22-inch bottles (aspect ratio of 1.13) and the 3.44-inch bottles (aspect ratio of 1.20). The 3.22-inch bottles demonstrated a lower vacuum resistance, which was probably from failure caused by ovalization instead of localized paneling. On the other hand, a high aspect ratio (e.g., 2.3) can make the effective ring depth very shallow, making the bottles more susceptible to ovalization and/or localized paneling. Thus, if the aspect ratio is too high (making the land segments more flat), the container will have a tendency to fail at a lower pressure due to localized paneling. On the other hand, if the aspect ratio is too low (making the land segments more bulbous), the container will have a tendency to fail at a lower pressure due to ovalization. Because the bottles across most of label heights HL had unexpected superior vacuum resistance performance at approximately the same vertical radius RA, the vertical radius RA seems less dependent on the vertical dimensions HS or HL, and more dependent on the label diameter DL.
The graph 100 further reveals that the bottles having land segments with the curved surface had far superior vacuum resistance than the bottles having land segments with a flat surface (i.e., when the vertical radius RA is 1000 inches). Results show a vacuum resistance improvement in the range of about 20% to 55% (average of 38%) of the bottles having the curved land segments over the bottles having the flat land segments.
Accordingly, the bottles described herein have a sidewall that includes land segments with a preferred curved geometry to increase the resistance to localized paneling, as well as including indented ring segment configurations sufficient to maintain the resistance to ovalization. Within a more desirable aspect ratio range, the vertical radius RA of the curved surface of each land segment can be less than or equal to 2.45 DL because a larger ratio may cause the bottle to be more susceptible to localized paneling at a lower vacuum pressure. The vertical dimension HS of the land segments can be equal to or greater than 0.49 DL because a smaller ratio may result in land segments that are so short that that the bottles are more prone to failure at a lower vacuum pressure caused by ovalization than by localized paneling. The ring depth can be equal to or greater than 0.08 DL because a smaller ratio may cause the bottle to be more susceptible to ovalization at a lower vacuum pressure.
In one example, a 20-ounce bottle plastic bottle (with a 3-2 design) having an overall vertical distance of 7.663 inches; a label diameter DL of 2.862 inches; a ring depth 78 of 0.223 inches; an indented ring segment vertical radius RB of 0.056 inches; an arcuate shoulder vertical radius RBL of 0.259 inches; an effective ring depth of 0.207 inches; an inflection angle of 20 degrees; a vertical radius RT of 0.283 inches; a land segment height HS of 1.516 inches; a label height HL of 3.670 inches; a land segment vertical radius RA of 7.000 inches; and a wall thickness between 0.011 inches to 0.02 inches. The plastic bottle with these dimensions has a relatively light weight of about 31 grams, yet still has a sufficiently high vacuum failure pressure between 6 to 8 psi. Comparable 20-ounce bottles having similar vacuum resistance performance are known to weigh at least 37 grams, primarily from the added material thickness along the sidewall to strengthen it for satisfactory vacuum failure resistance. Accordingly, the plastic bottles described herein having a sidewall geometry with one or more of the ratios above can permit the plastic bottle to have a lighter weight and/or a reduced number of indented ring segments, while having a satisfactory vacuum failure resistance. The lighter weight (about 16% lighter) of the plastic bottle further reduces the material cost per bottle.
While these features have been disclosed in connection with the illustrated preferred embodiment, other embodiments of the invention will be apparent to those skilled in the art that come within the spirit of the invention as defined in the following claims.
The present application is a continuation of PCT/US2010/033082 filed Apr. 30, 2010, which in turn claims benefit to U.S. provisional application 61/175,506 filed May 5, 2009.
| Number | Date | Country | |
|---|---|---|---|
| 61175506 | May 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2010/033082 | Apr 2010 | US |
| Child | 13324384 | US |
