Abstract:
A plastic bottle has a champagne base that includes a planar standing ring located between a lower margin of a convex heel of the base and a lowermost portion of a central concavity within the standing ring. By making the inside vertical radius of the convex heel lower margin and central concavity lowermost portion sufficiently small, the bottle is shown to exhibit increased top load strength without any increase in plastic. The bottle also has a larger standing ring diameter leading to a more stable bottle.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is directed to plastic bottles having a champagne style bottom structure closing the bottle lower end. The phrase champagne style is in reference to a base having an outside surface rotationally symmetric about a longitudinal axis of the bottle including a convex heel having an upper margin integrally formed with the lower end portion of the bottle sidewall, and a central concavity separated from the convex heel by a continuous standing ring that supports the bottle on any underlying surface. 
         [0003]    2. Description of the Prior Art 
         [0004]    Bottle bases having a standard champagne dome have long been employed with glass bottles. Consumers have become accustomed to such base configurations, particularly when the bottles contain wine, whether a sparkling wine or a non-sparkling wine. In glass bottles, the champagne dome distributes forces exerted thereon by any internal pressure of the bottle. The standard champagne base also provides for a stable presentation of the bottle on a continuous standing ring. In glass bottles, the champagne base provides an adequate support during capping operations as well as during shipment. While the use of a champagne base is desirable from a consumer point of view, the application of such a base to plastic bottles has provided difficulties to the plastic bottle industry. 
         [0005]    Global trade in wine has increased rapidly in recent years and is currently estimated to exceed ten billion US dollars annually. Reports of health benefits and rising global incomes have spurred this increasing demand for wine. Together, the United States and the European Union accounted for over 60% of global imports of wine. The wine industry is considering the adoption of plastic bottles to lower both packaging and transportation costs. However the consumer still requires that the bottles have the base configuration to which they are accustomed. For reasons of efficiency and cost, the plastic bottle industry has embraced the conventional technique of blow molding plastic bottles from plastic preforms. The preforms are desirably made with the least amount of plastic that will still permit the finished bottle to satisfactorily perform in the intended manner. The industry often uses polyethylene terephthalate (“PET”) or polypropylene (“PP”) to construct plastic bottles due, in part, to the ability to reclaim and recycle such bottles. A barrier layer can be included to inhibit the migration of gases such as oxygen as well as moisture into or out of, the bottle. The barrier layer can be an intermediate extruded or injection formed layer made, for example, from ethylene vinyl alcohol (“EVOH”), or an interior layer such as a barely perceptible layer of glass, applied by plasma after the bottle is formed. In order to provide a plastic bottle constructed of PET or PP with desirable clarity characteristics, it is generally desirable to impart bi-axial stretching to the plastic material forming the bottle. 
         [0006]    A standard practice used to blow mold plastic bottles having a champagne base is to slightly increase the thickness of a majority of the base relative to the thickness of the remainder of the bottle. Preforms used to construct a bottle having such a base are known and do not require complex configurations. However, other attempts to blow mold an acceptable plastic bottle have placed material concentrations in specific predetermined areas of the base to increase the amount of stress that can be withstood without failing. One such prior art base configuration uses a stepped base to increase the thickness of the dome to a thickness that is substantially thicker than the dome of a standard base. Another prior art plastic bottle having a champagne base designed for enhanced pressure within the bottle includes a reinforced hoop to deter the champagne dome from inverting due to the enhanced internal pressure of the bottle. However, an intricate preform is required to direct material concentrations to the necessary areas of the base to form the reinforced hoop. This configuration increases material consumption and increases the difficulty of constructing the preforms. Because plastic bottles are desirably produced in extremely high volume, economies of scale make these configurations prohibitive. 
         [0007]    There is therefore an unsatisfied need for a low-cost plastic bottle for containing wine having an acceptable appearance from the consumer point of view, which is stable on planar supporting surfaces and withstands the top load requirements experienced during the bottling and capping operation as well as during transport of the filled bottles. 
       SUMMARY OF THE INVENTION 
       [0008]    In one aspect, a plastic bottle has a sidewall and a bottom structure closing the bottle at a lower end portion of the sidewall, the bottom structure providing superior resistance to failure when the bottle is subjected to a vertical load. The bottom structure has an outside surface that is rotationally symmetric about a longitudinal axis of the bottle. The bottom outside surface can include a convex heel having an upper margin of diameter D integrally formed with the lower end portion of the sidewall. A lower margin of the convex heel can lead to a continuous planar standing ring lying in a plane perpendicular to the longitudinal axis of the bottle that can support the bottle on any underlying surface. A central concavity is provided inside the standing ring. The central concavity can include a first surface defined by a circular cone inclined with respect to the plane of the standing ring, with the first surface having a lower most portion smoothly joining the standing ring. The inside vertical radius of curvature of the lower margin of the convex heel and the lower most portion of the first surface can be suitably dimensioned in relation to the diameter D to achieve the desired enhanced top load failure resistance. 
         [0009]    In one aspect, the lower margin of the convex heel can have an inside vertical radius of less than 0.11D. The lower margin of the convex heel leading to the planar standing ring can have an inside vertical radius of between 0.039D and 0.067D. A portion of the convex heel above the lower margin of the convex heel can have a vertical inside radius of curvature of between 1.26D and 1.42D. 
         [0010]    In yet another aspect, the lower most portion of the first surface can have an inside vertical radius of less than 0.10D. The lowermost portion of the inside concavity first surface can have an inside vertical radius of between 0.055D and 0.084D. A portion of the inside concavity first surface above the lowermost portion of the first surface can be inclined at an angle of between 35° and 40° with respect to a plane formed by the standing ring. 
         [0011]    In the various aspects of the present invention, the central concavity can also include a second surface joined to an upper margin of the first surface by a concave ring. The second surface can be a downwardly convex dome centered on the longitudinal axis of the bottle. The inside concavity second surface can have a radius of curvature of between 0.23D and 0.27D. The inside concavity second surface can have a lowermost nadir situated between 0.14D and 0.16D above the standing ring. The concave ring joining the inside concavity first surface to the inside concavity second surface can have an outside vertical radius of between 0.059D and 0.066D. 
         [0012]    In the various aspects of the present invention the planar standing ring of the bottle can have a width of between 0.015D and 0.021D. The planar standing ring should have a diameter as large as possible to enhance bottle stability. With the preferred configurations the standing ring can have an inner diameter of between 0.73D and 0.82D. The planar character of the standing ring helps assure the bottle will remain upright on any underlying supporting surface. 
         [0013]    Each of these features contributes to a low gram weight bottle especially designed for containing wine having superior resistance to failure when subjected to a vertical force. For example, following these features one can form a one-liter bottle capable of withstanding a vertical force of 180 kg with only 54 grams of plastic. On the other hand a somewhat similar 750 ml bottle made with the same amount of plastic and having features that differed in only small respects, detailed below in the comparative example, failed when subjected to a vertical force of less than 165 kg. 
         [0014]    Further, by adopting smaller values for the vertical inside radius for both the lowermost portion of the inside concavity first surface and the lower margin of the convex heel, one can achieve satisfactory performance with a greater standing ring diameter which contributes to enhanced bottle stability. 
         [0015]    Other features and advantages of the present invention will become apparent to those skilled in the art from the following disclosure of preferred embodiments of the present invention exemplifying the best mode of practicing the invention. The following disclosure references the accompanying drawings illustrating the preferred embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a side elevation view of a bottle. 
           [0017]      FIG. 2  is a sectional outline of the exterior surface of the base of the bottle shown in  FIG. 1  taken through the axis of the bottle. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0018]    A plastic bottle  10  is shown in  FIG. 1  to have a base  12 , which will be detailed below. A sidewall  14  extends upward from the base  12 . For the purpose of this disclosure, the diameter of the bottle  10  at the junction of the base  12  and sidewall  14  is given the dimension D. While the sidewall  14  is shown to have a right cylindrical configuration, other configurations for the sidewall  14  are also contemplated. A shoulder  16  unitarily joins the top of the sidewall  14  to a neck  18 . A finish portion  20  is provided at the top of the neck  18  to which a suitable closure, not shown, can be applied to seal an opening  22  that is present at the top of the bottle  10 . While the finish portion  20  is shown to include a threaded portion  24  and an optional tamper evident ring receiving portion  26 , other configurations for the finish portion  20  are also contemplated. The bottle  10  has an overall height H, and is generally symmetric about a vertical axis Y extending from the center of the base  12  to the center of the opening  22 . 
         [0019]    The base  12  of the bottle  10  is shown in detail in  FIG. 2  to include a convex heel  24  extending downward from the sidewall  14 . An upper portion  26  of the heel  24  is defined by an inside vertical radius R 1 , while a lower portion  28  of the heel  24  is defined by a smaller inside vertical radius R 2 . A continuous planar standing ring  30  joins the heel lower portion  28  to a central concavity  32  situated within the standing ring  30 . The standing ring  30  has a horizontal surface of width W and an inner diameter S. The standing ring  30  lies in a horizontal plane X that is generally perpendicular to the longitudinal axis Y of the bottle  10 . The central concavity  32  includes a first surface  34  having a lowermost portion  36 . The first surface lowermost portion  36  is defined by a vertical inside radius R 3  and smoothly joins the standing ring  30  to a portion  38 , which can be conical. The conical portion  38  can extend upward from the lowermost portion  36  at an angle β with respect to the plane X. An upper margin of the conical portion  38  can be joined to a second surface  40  by a concave ring  42 . The second surface  40  can be defined by a vertical inside radius R 4  that can be centered on the vertical axis Y. The nadir  44  of the second surface  40  can be aligned with the vertical axis Y at a distance C above the plane X. The concave ring  42  can be defined by a vertical outside radius R 5 . 
         [0020]    However, every bottle  10  having the general configuration shown in  FIGS. 1 and 2  will not have the top load strength deemed minimally satisfactory. Table I provides the various dimensions for both a comparative example bottle  1 A that failed to perform satisfactorily and some working examples of bottles that did perform satisfactorily. All of the bottles reported in Table I were made from preforms having approximately 55 grams of plastic, including bottle  3 . 1 A, which is designed to contain 1 liter of liquid while the remaining bottles of Table I are designed to contain only 750 ml. It will be noted that certain of the dimensions overlap for both satisfactory bottles and un-satisfactory bottles while other dimensions identify a clear separation between success and failure under the top load test. 
         [0021]    For example, it will be noted that the inside vertical radius R 1  of the upper portion of the heel  26  in the failing bottle  1 A has the same dimension as in two bottles that were successful. It will be further noted that the radius R 1  can have a range of values that are successful. The radius R 1  for satisfactory bottles can have a range of values from 1.42D down to 1.26D. When radius R 1  is increased much beyond 1.42D, the base has a tendency to fold under itself under below-standard top loads. When the radius R 1  is reduced much below 1.26D, some difficulty is observed in the complete formation of the heel. 
         [0022]    It will also be noted that the inside vertical radius R 4  of the second surface  40  in successful bottles can be larger, smaller or the same size as the failing bottle  1 A. The radius R 4  can have a range of values from 0.23D to 0.27D. The radius R 4  may be able to assume values even outside this range. 
         [0023]    It will also be noted that the outside vertical radius R 5  of the ring  42  joining the conical portion  38  to the second surface  40  in successful bottles can be larger, smaller or the same size as the failing bottle  1 A. The radius R 5  can have a range of values from 0.059D to 0.066D. The radius R 5  may be able to assume values even outside this range. 
         [0024]    It will be further noted that the width W of the standing ring  30  in the failing bottle  1 A has the same dimension as in two bottles that were successful. It will be further noted that the width W can have a range of values that are successful. The width W for satisfactory bottles can have a range of values from 0.021D down to 0.016D. The width W may be able to assume values even outside this range. 
         [0025]    It will be further noted that the height C of the nadir  44  of the second surface portion  40  above the standing ring  30  for successful bottles can be larger, smaller or the same size as the failing bottle  1 A. The height C for satisfactory bottles can have a range of values from 0.159D down to 0.143D. The height C may be able to assume values even outside this range. 
         [0026]    One dimension that clearly separates successfully performing bottles from unsuccessful bottles is the vertical inside radius R 2  of the lowermost portion  28  of heel  24 . Distinctly smaller radius values for radius R 2  perform satisfactorily while larger radius values appear to contribute to failure. The radius R 2  should have a value of less than 0.11D, and should preferably have a value between 0.039D and 0.067D. 
         [0027]    Another dimension that separates successfully performing bottles from unsuccessful bottles is the vertical inside radius R 3  of the lowermost portion  36  of the central concavity first surface  34 . Distinctly smaller radius values for radius R 3  perform satisfactorily while larger radius values also appear to contribute to failure. The radius R 3  should have a value of less than 0.10D, and should preferably have a value between 0.055D and 0.084D. 
         [0028]    Another dimension that separates successfully performing bottles from unsuccessful bottles is the diameter S of the standing ring  30 . Greater values for the diameter S are preferred over smaller values as they contribute to enhanced stability for the bottle. The diameter S can have a value of greater than 0.74D, and should preferably have a value between 0.75D and 0.82D. This greater diameter S can only be achieved through the adoption of the smaller values for R 2  and R 3  as discussed above. 
         [0029]    From the forgoing description of the structure and operation of a preferred embodiment of the present invention, it will be apparent to those skilled in the art that the present invention is susceptible to numerous modifications and embodiments within the ability of those skilled in the art and without exercise of the inventive facility. Accordingly, the scope of the present invention is defined as set forth of the following claims. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE I 
               
               
                   
               
               
                 Examples 
                 R1 
                 R2 
                 R3 
                 R4 
                 R5 
                 W 
                 S 
                 C 
                 β 
               
               
                   
               
             
             
               
                 1A 
                 1.42D 
                 0.111D 
                 0.104D 
                 0.250D 
                 0.063D 
                 0.021D 
                 0.733D 
                 0.150D 
                 40° 
               
               
                 (comp.) 
               
               
                 1AA 
                 1.42D 
                 0.067D 
                 0.083D 
                 0.250D 
                 0.063D 
                 0.021D 
                 0.758D 
                 0.150D 
                 35° 
               
               
                 2AA 
                 1.42D 
                 0.067D 
                 0.083D 
                 0.250D 
                 0.063D 
                 0.021D 
                 0.758D 
                 0.150D 
                 35° 
               
               
                 3.1A 
                 1.27D 
                 0.040D 
                 0.056D 
                 0.238D 
                 0.060D 
                 0.016D 
                 0.818D 
                 0.143D 
                 35° 
               
               
                 5A 
                 1.37D 
                 0.043D 
                 0.060D 
                 0.257D 
                 0.064D 
                 0.017D 
                 0.803D 
                 0.154D 
                 35° 
               
               
                 6A 
                 1.41D 
                 0.044D 
                 0.062D 
                 0.265D 
                 0.066D 
                 0.018D 
                 0.797D 
                 0.159D 
                 35°