Abstract:
A container is disclosed having an outwardly protruding bulge in its neck that expands in response to an increase in internal container pressure, thereby partially relieving the internal pressure increase, which benefits the label appearance and adherence characteristics, and enables the base to be reduced in weight.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/300,844 filed Jun. 25, 2001, which is incorporated by reference herein. 
    
    
     BACKGROUND 
     The present invention relates to plastic containers, and more particularly to plastic containers for holding carbonated or like products that expand after sealing or capping. 
     Plastic bottles are in widespread use for containing beverages and food products. A particular type of bottle, which is filled with products at elevated temperatures, is designed to accommodate internal vacuum pressure developed upon cooling of the products after sealing. Often, hot fill bottles include panels formed in the container sidewall that inwardly flex or deform in response to formation of an internal vacuum. For example, U.S. Provisional Patent Application No. 60/295,911, filed Jun. 4, 2001, entitled “Hot-Fillable Container With Grip” discloses a bottle in which inward, vacuum-induced deformation is distributed outside of the handgrip panel. 
     Another type of plastic bottle that contains carbonated beverages (or like products that exhibit increased internal bottle pressure—that is, compared with the internal pressure upon or soon after capping or sealing) is designed to accommodate internal positive pressure (that is, pressure greater than the ambient atmosphere). Such bottles, which will be referred to herein as “pressurized bottles,” are typically formed of blow-molded PET that is capable, upon orienting, of containing an internal bottle pressure of several atmospheres, which may occur when carbonated contents within a bottle are exposed to elevated temperatures, such as 100 degrees F. to 120 degrees F. Such temperatures may be encountered during storage or during transport while the bottle is not in an air-conditioned environment, or like circumstances. 
     Plastic bottle production is, of course, a competitive industry in which weight-reducing techniques produce significant costs savings, especially in light of the vast quantity of bottles produced worldwide. However, the high internal pressures that pressurized bottles must contain provides a constraint against bottle weight reduction. 
     U.S. Pat. No. 6,176,382, entitled “Plastic Container Having Base with Annular Wall and Method of Making the Same,” discloses a conventional beer bottle shape that may be subject to high internal pressures due to the carbonated (or otherwise pressurized, such as for example by nitrogen) beverage contained therein being exposed to elevated temperature. In this regard, as in most conventional beer bottles and many other pressurized bottles, the exemplary bottle  110  shown in FIG. 7 (PRIOR ART) has a tapered neck  112  extending above a right circular body  116 . A shoulder  118  is disposed between neck  112  and body  116 . A label panel  120  is defined by at least a portion of body  116 . Neck  112  may also receive a label (not shown in the Figures). 
     Neck  112  has a continuous taper so as to form a frustum of a right circular cone. In this regard, a neck diameter D-PA 1  near an upper end of neck  12  is less than a diameter D-PA 2  near a lower end of neck  12 . Another conventional glass bottle shape (not shown in the Figures) has an upper neck diameter that is the same as the lower neck diameter such that the neck substantially forms a cylinder having a circular cross section. In this regard, the term “straight” or “straight portion” will be employed to refer to a sidewall or a sidewall portion, respectively, that is rectilinear or not curved in longitudinal cross section. 
     Referring again to FIG. 7, the straight sidewalls of neck  112  and body  116  deform in response to an increase in internal pressure, as indicated diagrammatically by the dashed lines in FIG.  7 . The maximum radial expansion is indicated by Δ-PA-neck and Δ-PA-body, respectively. Typically, the volumetric expansion of the neck is less than the volumetric expansion of the body and/or the base. 
     Often, a plastic bottle is developed to replace a corresponding glass container with economic advantages that are apparent. In some circumstances, technical problems must be solved to make a plastic bottle that is commercially satisfactory. For example, a plastic bottle containing a carbonated (or otherwise pressurized) product inherently yields more than a corresponding glass container in response to an increase in internal pressure. Thus, a label panel of a plastic pressurized bottle may deform in response to an increase in internal pressure. Such label panel expansion is undesirable for aesthetic reasons and because the label may tend to separate from the label panel. Further, the bottle base may tend to bulge or “roll out” in response to such internal pressure, thereby making the base unstable. 
     In order to produce a bottle that is sufficiently strong to withstand such internal pressure without unacceptable label expansion and/or base expansion or roll-out, bottles formed of oriented thermoplastic are designed with a sidewall and base of sufficient thickness and weight. In general, there is a need for pressurized bottles that have improved expansion characteristics, and/or reduced weight. 
     SUMMARY 
     A bottle is provided that includes a neck that expands volumetrically in response to an increase in internal bottle pressure. In this regard, such a plastic container comprises a body, a base extending from the body and enclosing a lower end of the container, a finish disposed at an upper end of the container, and a neck disposed between the finish and the body. The neck includes an outwardly convex portion that radially expands in response to positive internal pressure, whereby the maximum magnitude of the radial expansion is less than a maximum magnitude of radial expansion for a frusto-conical neck of like dimension. 
     Further, the bottle may include a waist that is outwardly concave such that the convex portion of the neck extends upwardly from and smoothly yields from the waist. Thus, the waist may form a hinge point relative to the convex portion. According to another aspect, the neck&#39;s convex portion expansion may diminish expansion of the body straight sidewall, thereby enhancing the appearance and adherence of the label. Also, such expansion may enable the total weight of the bottle to be reduced. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a perspective view of a bottle according to an embodiment of the present invention; 
     FIG. 4 is a bottom view of the bottle of FIG. 1; 
     FIG. 3 is a top view of the bottle of FIG. 1; 
     FIG. 4 is a top bottom of the bottle of FIG. 1; 
     FIG. 5 is an enlarged longitudinal cross sectional view of a portion of the bottle of FIG. 1; 
     FIG. 6 is an enlarged longitudinal cross sectional view of a portion of a bottle according to another embodiment of the present invention; and 
     FIG. 7 (PRIOR ART) is a perspective view of a bottle having a conventional neck shape. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     As shown in FIGS. 1,  2 , and  5  according to a first embodiment of the present invention, a bottle  10  includes a neck  12 , a base  14 , and a body  16 . Body  16  is formed by a cylindrical sidewall that preferably is circular in transverse cross section (such transverse cross section is not shown in the Figures, although the circular shape of body  16  is evident from FIG.  3 ). Base  14  extends from a lower portion of body  16  so as to enclose the lower portion of bottle  10 . Base  14 , on an underside of bottle  10 , preferably includes a conventional base, such as the champagne-style base shown in dashed lines in FIG.  2  and as shown in FIG.  4 . Such a champagne-style base is well known and in widespread use. The present invention, however, is not limited to any particular base design, but rather encompasses any base configuration. A conventional finish  22  is disposed above an upper end of neck  12 . 
     Body  16  may have, as shown in the Figures, shoulders  18   a  and  18   b  disposed at an upper and lower end thereof, respectively, so as to define a label panel  20  therebetween. For bottles that lack such shoulders, the label panel may be defined by any portion that is capable of receiving a label. Thus, label panel  20  is shown as cylindrical with a circular transverse cross section, although any shape capable of receiving a label may be employed. 
     A waist  24  smoothly extends upwardly from shoulder  18   a , or alternatively from body  16  directly (not shown in the Figures). Waist  24  is defined by a radius R- 24  such that the diameter of waist  24  is less than a diameter of shoulder  18   a  and a portion of neck  12 . The particular configuration of waist  24  or radius R- 24  may depend upon the particular aspects of the application in which the present invention may be employed. 
     Neck  12  extends upwardly from waist  24 . According to an aspect of the present invention, neck  12  includes a bulge  26 . Bulge  26  protrudes radially outwardly relative to a straight line between drawn between a point on a relatively lower portion of neck  12  and a point on a relatively upper portion of neck  12 . Thus, bulge  26  encompasses a configuration such that the bulging portion forms substantially all of the neck (as in the Figures) and configurations in which any portion of the neck forms a bulge. Further, the present invention encompasses any configuration in which the neck is employed to expand in response to increased internal pressure. 
     Referring to FIG. 5, a dashed line illustrates the relative magnitude of the deformation of neck  12 . The dashed line of FIG. 5 is diagrammatic such that the deformation illustrated by the dashed line is not to scale, but rather is enlarged for illustration and for clarity. The dimensions ΔA 1 , ΔA 2 , and ΔA 3  indicate an upper, middle, and lower deformation from an initial state to a deformed state, thus reflecting, for example, radial deformation from an internal pressure condition at ambient temperature or cold storage temperature to an internal pressure condition at an elevated internal pressure, such as that which may be encountered upon exposure of the product to common elevated temperatures. Deformation dimension ΔA 2  is taken at the position at the widest point of bulge  26 . 
     According to another embodiment of the present invention, as illustrated in FIG. 6, a bottle  10 ′ includes a neck  12 ′ that extends upwardly from a shoulder  18   a ′ without a transition waist. Thus, shoulder  18   a ′ smoothly yields to bulge  26 ′ such that, in longitudinal cross section, the tangents at all points from the upper portion of shoulder  18   a ′ throughout bulge  26 ′ form an angle with a horizontal line H (that is, a line perpendicular to longitudinal centerline C) that is equal to or less than  90  degrees. Such an angle is illustrated by angle A 2  in FIG.  6 . The present invention, however, is not limited to such a configuration. In this regard, the first embodiment bottle  10 , as shown in FIG. 5, has an angle defined by a tangent of a portion of neck  12  where waist  24  yields to bulge  26  that is greater than 90 degrees. Such an angle is illustrated by angle A 1  in FIG.  5 . 
     It has been found that bulge  26  or  26 ′ promotes volumetric expansion of neck  12  or  12 ′ in response to an increase in internal pressure, thereby diminishing the deformation of label panel  20  and/or base  14 . Such beneficial neck expansion, compared with conventional expansion illustrated by the dashed line in FIG. 7, may result from any one or combination of factors. For example, waist  24 , in the first embodiment  10 , or the transition from shoulder  18   a ′ to bulge  26 ′ in the second embodiment  10 ′, may provide a hinge point or a hinge line or area that promotes deformation of bulge  26  or  26 ′. In this regard, the magnitude of radial deformation ΔA 2  or ΔB 2  may be less than a corresponding maximum deformation Δ-PA-neck (illustrated in FIG. 7) of a conventional frusto-conical neck. The present invention, however, is not limited to such relative deformation (that is, ΔA 2  or ΔB 2  being less than Δ-PA-neck). Rather, such relationship is described merely to provide one possible explanation of the beneficial aspects of employing bulge  26  or  26 ′. 
     In this regard, the radial deformation at the bulge mid-point ΔA 2  or ΔB 2  is greater than the radial deformation of the corresponding upper and lower points ΔA 1 , ΔA 3 , ΔB 1 , and ΔB 3 . However, it is anticipated that radial deformation ΔA 2  will be relatively close to radial deformations ΔA 1  and ΔA 3 , and that radial deformation ΔB 2  will be relative close to radial deformations ΔB 1 , and ΔB 3  (that is, such the radial deformations of the embodiments of the present invention will be relatively small compared with the difference between the magnitude of radial deformation Δ-PA-neck and the magnitude of deformation near corresponding upper and lower points of the conventional neck  112 ). 
     Neck  12  or  12 ′ may be formed with particular dimensions according to the desired application, considering such parameters as bottle volume, maximum expected pressure, overall bottle design weight, and the like, as will be understood by persons familiar with bottle design technology in light of the present disclosure. Further, the present invention encompasses a bulge  26  or  26 ′ having any cross sectional configuration. 
     For a sixteen ounce capacity bottle, which generally has the shape shown in FIG. 1, that was subjected to 4.5 atmospheres at 100 degrees F., the radial deformation ΔA 2  was approximately 0.005 inches to 0.007 inches (that is, 0.010 inches to 0.014 inches change in diameter). The distribution of the deformation, as described above, was such that neck  12  was still suitable for receiving a label thereon. 
     Bulge  26  or  26 ′ may be formed according to the present invention by employing either a preform that is configured specifically for such a neck  12  or  12 ′ or a preexisting preform configuration employed for producing bottles having the conventional neck of FIG.  7 . In the latter case, a conventional preform would be blown into the shape of bulge  26  or  26 ′ such that the sidewall thickness of the bulge  26  or  26 ′ would be less than the corresponding prior art sidewall thickness. In this regard, bulge  26  or  26 ′ may provide greater volumetric expansion than prior art (straight-walled) neck configurations because of its geometry (as described above) or because of its diminished wall thickness relative b a prior art neck, or both in combination. 
     Thus, the present invention encompasses employing a bulge  26  or  26 ′ in such a configuration in which the waist  24  (or transition structure, including shoulder  18   a ′, in the second embodiment) does not act as a hinge. Similarly, the present invention encompasses employing a bulge  26  or  26 ′ in which the bulge sidewall does not have a sidewall that is relatively thin. Rather, the present invention encompasses a sidewall that provides the volumetric expansion characteristics disclosed herein, regardless of the particular structure. 
     Several, and to some extent alternative, advantages flow from the present invention. Under some configurations, label panel  20  may undergo less deformation because of the volumetric expansion capacity provided by the bulge  26  or  26 ′. Such diminished label panel deformation may enhance the appearance of the label and/or enhance the adherence of the label to panel  20 . Under other configurations, the bottle may be reduced in weight. In this regard, a bottle having a conventional neck, as roughly shown in FIG. 7, was modified so as to be configured with a neck  12  as shown in FIG.  1 . The bottle having the conventional neck weighed approximately 35 grams. Employing a neck  12  on such an otherwise conventionally-shaped bottle enabled the weight of base  14  to be reduced by approximately one gram while maintaining a maximum total diameter change of body  16  under 2.5% (for a bottle held at 3.5 atmospheres at 100 degrees F.). 
     Bottles containing beer is an application to which the present invention may be employed. In general, converting beer containers from glass to plastic was problematic because of the poor oxygen barrier properties of blow-molded PET and the sensitivity of beer to oxygen exposure. However, recent development has employed an oxygen scavenging layer that provides excellent oxygen protection for a commercially suitable period. 
     In this regard, an oxygen scavenger is disclosed in U.S. Pat. No. 5,021,515, entitled “Packaging,” which is incorporated herein by reference in its entirety. Oxygen barrier layers are also well known, although some multiple layers tend to separate upon repeated exposure to deformation. In this regard, the present invention may be employed with such oxygen scavenger or oxygen barrier materials or layers. Bulge  26  or  26 ′may also diminish layer separation in circumstances in which the maximum deformation ΔA 2  or ΔB 2  is less than Δ-PA-neck. 
     The present invention is illustrated by disclosing particular embodiments. The present invention, however, is not limited thereto, but rather encompasses other embodiments that will be clear to persons familiar with design of pressurized bottles. For example, necks  12  and  12 ′ have a bulge  26  and  26 ′ formed substantially over the entire length of neck  12  and  12 ′, respectively. Other embodiments encompassed by the present invention are referred to in the above description. The present invention also encompasses a bulge that is formed only on a portion of the corresponding neck, a neck that has a bulge interspersed with straight or flat sections, and the like. 
     Further, the bulge  26  and  26 ′ are shown having a radius of curvature (in longitudinal cross section) that varies along the length or height of neck  12  and  12 ′. The present invention also encompasses employing bulges that have a single radius of curvature, or any other combination of radii of curvature to form any shape in longitudinal cross section or transverse cross section. More than one bulge may be employed, including a series of small bulges. Such bulges may be disposed on the neck such that one bulged is disposed above an adjacent bulge. Further, the present invention encompasses bulges formed into an accordion-like or bellows-like configuration, bulges that are not circumferentially continuous, and bulges that are not rounded.