Patent Publication Number: US-2011049083-A1

Title: Base for pressurized bottles

Description:
BACKGROUND 
     The present disclosure is directed to plastic bottles, and particularly to a supporting champagne style base that is unitary with the remainder of the bottle, which improves the perpendicularity of the bottle. 
     Plastic bottles that include a base having a continuous uninterrupted standing ring for supporting the bottle on any underlying surface are sometimes referred to having a champagne style base. The perpendicularity or vertical alignment of such bottles can depend on the evenness of material distribution in the area of the standing ring, particularly when the bottles are subjected to even small internal pressures of 15 psi or less. While small variations from a true vertical alignment can be tolerated, any significant variation may cause problems in subsequent labeling and boxing of such bottles. While a large diameter standing ring is generally thought to provide enhanced stability as a result of the larger foot print, the large diameter standing ring is more flexible as a result of less material being present in the standing ring. As a result, even small variations in material distribution in large diameter standing rings can lead to unacceptable variations in the vertical alignment or perpendicularity of the bottle. This problem has in the past been addressed by forming a preform with significant non-uniform wall thicknesses so that a substantial amount of material is placed in the chime in direct alignment with the standing ring. Examples are to be found in U.S. Pat. Nos. 4,725,464; 4,780,257; 4,889,752 and 6,248,413. 
     A significant disadvantage of using preforms having significant non-uniform wall thicknesses to place additional material in the chime in direct alignment with the standing ring is the additional polymer itself, which increases the cost of the bottle. There is thus a need for a lower-cost solution to enhance the perpendicularity or vertical alignment of blow molded plastic bottles having a champagne style base. 
     SUMMARY 
     A plastic bottle has a base centered on a vertical axis. The base has a continuous standing ring to support the bottle on any underlying support surface. A side wall is formed unitarily with the base and extends from the base upward to an upper end of the side wall. A neck is unitarily connected to the upper end of the side wall that includes a finish adapted to receive a cap to close an opening into the bottle interior. The bottle has a height defined by the distance between the opening and the standing ring, and a maximum width across the bottle. To enhance the vertical alignment or perpendicularity of the bottle, the base standing ring can be defined in vertical cross-section by a continuous curve. The base standing ring can have a diameter less than 80% of the maximum side wall width. The continuous curve of the base standing ring can be bounded on a radial inside by an interior region that includes a plurality of concave domed wedge-shaped sections interspaced with buttress sections having substantially planar inclined outer portions. The continuous curve of the base standing ring can be bounded on a radial outside by a conic section portion centered on the vertical axis. 
     The vertical alignment or perpendicularity of the bottle can be enhanced by limiting the apex angle of the conic section portion to less than 160°. The vertical alignment or perpendicularity of the bottle can be further enhanced by maintaining the width of the conic section portion to at least 0.035 inches (0.889 cm). 
     The vertical alignment or perpendicularity of the bottle can also be enhanced by limiting the standing ring diameter to be more than 70% of the maximum bottle side wall width. The vertical alignment or perpendicularity of the bottle can be further enhanced by limiting the average standing ring thickness to between 1.0 and 1.3 times the thickness of the side wall. The vertical alignment or perpendicularity of the bottle can be further enhanced by limiting variation in the standing ring thickness to less than ±20%. Another feature of the base that can improve the vertical alignment or perpendicularity of the bottle is confining the vertical cross-sectional radius defining the standing ring to between 0.100 inches (0.254 cm) and 0.300 inches (0.762 cm). 
     Another feature of the base that can improve the vertical alignment or perpendicularity of the bottle is limiting the curvature of the concave dome portion to a radius of at least 1.0 times the standing ring diameter. The vertical alignment or perpendicularity of the bottle can be further enhanced by buttress sections that have inclined outer portions that can be inclined at an angle of between 8° and 16° with respect to a plane defined by the base standing ring. The vertical alignment or perpendicularity of the bottle can be further enhanced by providing the angle of tangency at the point of intersection of the concave dome portion and the standing ring vertical cross-section to be at least 45°. 
     Other features of the present bottle base and the corresponding advantages of those features will become apparent from the following discussion of the preferred embodiments of the present container, exemplifying the best mode of practice, 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 features. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional outline of an exterior surface of a bottle. 
         FIG. 2  is a bottom plan view of the base of the bottle in  FIG. 1 . 
         FIG. 3  is a sectional outline view of the base taken along line  3 - 3  of  FIG. 2 . 
         FIG. 4  is an enlarged view of a portion of the left side of  FIG. 3 . 
         FIG. 5  is an enlarged view of a portion of the right side of  FIG. 3 . 
     
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT 
     A bottle  10  is shown in  FIG. 1  and the other Figs that has a generally cylindrical body  12  surrounding a longitudinal axis Y and a closed base  14  that is unitary with the remainder of the bottle. The  14  base has a continuous standing ring  16  to support the bottle  10  on any underlying support surface. The standing ring  16  has a standing ring diameter D. A side wall  18  is formed unitarily with the base  14  and extends from the base upward to an upper end  20  of the side wall  18 . A neck  22  is unitarily connected to the upper end  20  of the side wall  18  by a shoulder portion  21 . The neck  22  includes a finish  24  adapted to receive a cap (not shown) to close an opening  26  into the bottle interior  28 . The bottle  10  has a height H defined by the distance between the opening  26  and the standing ring  16 , and a maximum width W across the bottle  10 . 
     To enhance the vertical alignment or perpendicularity of the bottle  10 , the base standing ring  16  can be defined in vertical cross-section by a continuous curve of radius R S , shown in  FIGS. 4 and 5 , which can be between 0.100 inches (0.254 cm) and 0.300 inches (0.762 cm). The radius R S  is independent of the standing ring diameter D, where the standing ring diameter D is measured at the lowest point on the standing ring  16 . The curve defining the standing ring  16 , being continuous, does not include any flattened portion in the plane X defined by the standing ring, shown in  FIG. 3 . The base standing ring  16  can have a diameter D less than 80% of the maximum side wall width W. The base standing ring  16  can have a diameter D greater than 70% of the maximum side wall width W. 
     The continuous curve of the base standing ring  16  defined by R S  can be bounded on a radial inside, starting about at point or ring  30 , by an interior region  32 . The interior region  32  can include a plurality of concave domed wedge-shaped sections  34  as seen in  FIG. 2 . The concave domed wedge-shaped sections  34  can be formed by a constant inside radius R C  of at least 1.0 times the standing ring diameter D as shown in  FIGS. 3 and 5 . The angle of tangency λ at the point of intersection  30  of the concave dome portions  34  and the curve defining the standing ring  16  measured from the plane X as shown in  FIG. 5  can be between 45°and 55°. The wedge-shaped sections  34  can be interspaced with buttress sections  36 , which can also be wedge-shaped. The buttress sections  36  can have substantially planar inclined outer portions  38 . The planar outer portions  38  can be inclined at an angle θ of between 8° and 16° with respect to a plane X defined by the base standing ring  16  as seen in  FIG. 4 . The buttress sections  36  can include inner portions  40  defined by a concave surface  42  that becomes circumferentially continuous as it approaches a central downwardly protruding portion  44  surrounding the axis Y of the bottle. The lowest surface of the downwardly protruding portion  44  can be spaced above the plane X by a distance H C  of 14% to 20% of the standing ring diameter D. 
     The continuous curve of the base standing ring  16  defined by radius R S  can be bounded on a radial outside by a conic section portion  46  starting at point or ring  48  and extending linearly upwardly and outwardly to point or ring  50  as shown in  FIGS. 4 and 5 . The distance between point or ring  48  and point or ring  50  defines the width of the conic section portion  46 , which is preferably at least 0.035 inches (0.089 cm). The conic section portion  46  is seen to be generated by the rotation around the vertical axis Y of a line generating a conic section having an included apex angle Φ of less than 160° as shown in  FIG. 3 . A base outer portion  52  extending outward from point  50  to the side wall  18  can be formed as a torus segment defined by a constant radius R T  of between about 12% and 20% of the standing ring diameter D. 
     Between the point or ring  30  and the point or ring  48 , the material forming the standing ring  16  preferably has an average thickness of between 1.0 and 1.3 times the thickness of the material forming the side wall  18 . Between the point or ring  30  and the point or ring  48 , the thickness of the material forming the standing ring  16  desirably has a variation that is as small as possible and less than ±20%. 
     By way of example, a bottle  10  as shown in  FIG. 1  can have a height H of 8.813 inches (22.39 cm) and a maximum width W of 2.52 inches (6.40 cm). The standing ring diameter D of the example bottle can be 1.90 inches (4.826 cm). The vertical cross-section radius R S  defining the exterior surface of the standing ring  16  of the example bottle can be 0.150 inches (0.381 cm). The width of the conic section portion  46  of the example bottle can be 0.064 inches (0.163 cm). The average thickness of the material forming the side wall  16  of the example bottle can be 0.014 inches (0.0356 cm) while the average thickness of the material forming the standing ring can be 0.016 inches (0.0406 cm). The inside radius R C  forming the concave surfaces of the domed wedge-shaped sections  34  of the example bottle can be 1.990 inches (5.055 cm). The angle of tangency λ at the point of intersection  30  of the concave dome portions  34  and the curve defining the standing ring  16  measured from the plane X in the example bottle can be 50°. The angle of inclination θ of the planar outer portions  38  of the buttress sections  36  of the example bottle can be 11°. The radius R C  defining the concave surface  40  of the example bottle can be 0.263 inches (0.668 cm). The lowest surface of the central downwardly protruding portion  44  of the example bottle can be spaced above the plane X by a distance of 0.315 inches (0.800 cm). The apex angle Φ of the conic section generating the portion  46  of the example bottle can be 150°. The radius R T  forming the base outer portion  52  of the example bottle can be 0.300 inches (0.762 cm). The example bottle showed a 36% improvement in perpendicularity over a prior design. 
     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.