Patent Publication Number: US-8109398-B2

Title: Multi-panel plastic container with asymmetric vacuum panels

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to the field of plastic containers, and more particularly to plastic containers that are designed to accommodate the volumetric expansion and contraction that is inherent to the hot-fill packaging process. 
     2. Description of the Related Technology 
     Many products that were previously packaged using glass containers are now being supplied in plastic containers, such as containers that are fabricated from polyesters such as polyethylene terephthalate (PET). 
     PET containers are typically manufactured using the stretch blow molding process. This involves the use of a preform that is injection molded into a shape that facilitates distribution of the plastic material within the preform into the desired final shape of the container. The preform is first heated and then is longitudinally stretched and subsequently inflated within a mold cavity so that it assumes the desired final shape of the container. As the preform is inflated, it takes on the shape of the mold cavity. The polymer solidifies upon contacting the cooler surface of the mold, and the finished hollow container is subsequently ejected from the mold. 
     Hot fill containers are designed to be used with the conventional hot fill process in which a liquid product such as fruit juice is introduced into the container while warm or hot, as appropriate, for sanitary packaging of the product. After filling, such containers undergo significant volumetric shrinkage as a result of the cooling of the product within the sealed container. Hot fill type containers accordingly must be designed to have the capability of accommodating such shrinkage. Typically this has been done by incorporating one or more vacuum panels into the side wall of the container that are designed to flex inwardly as the volume of the product within the container decreases as a result of cooling. 
     Typically, the vacuum panel regions of conventional hot fill containers are characterized by having surfaces that are designed to deflect inwardly when the product within the sealed container undergoes shrinkage. In some instances, an island may be defined in the middle of the vacuum panel in order to provide support for an adhesive label that may be placed over the container. In other instances, ribs may be molded into the vacuum panel area in order to provide an enhanced grip surface or to enhance the strength of the vacuum panel area. Grippability for the consumer is an important consideration in the design of many containers. In containers that have vacuum panels with gripping structure, the technology for optimizing the efficacy of the gripping structure and the dimensional stability of the container while it is being gripped while at the same time permitting sufficient flexibility to accommodate volumetric changes within the container is still evolving. Minor changes in curvature and geometry may be important to such optimization. Top load strength and efficient utilization of plastic material are also important design considerations for such containers. 
     Vacuum panels of conventional hot-fill containers, including those vacuum panels that are provided with structure to enhance gripping, typically are designed to be substantially symmetrical about a central vertical axis as viewed in side elevation. PCT Publication WO 2007/041422 discloses such a container having four vacuum panels. In hot-fill container designs that have an even number of vacuum panels, opposing panels are also typically shaped to be substantially symmetrical about the center axis of the container. 
     A need has existed for an improved hot fill container design that possesses optimal capacity to accommodate volumetric expansion and contraction, grippability and dimensional stability while being gripped. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to provide an improved hot fill container design that possesses optimal capacity to accommodate volumetric expansion and contraction, grippability and dimensional stability while being gripped. 
     In order to achieve the above and other objects of the invention, a plastic container according to a first aspect of the invention includes a bottom portion and a sidewall portion. The sidewall portion has a maximum outer diameter, and further includes a first pair of opposing first vacuum panels, the first vacuum panels each having a first substantially constant radius of curvature as measured in a horizontal plane, the first substantially constant radius of curvature being substantially constant from an upper end of each of the respective first vacuum panels to a lower end, and wherein a ratio of the first substantially constant radius of curvature to the maximum outer diameter is within a range of about 0.3 to about 2.5; and a second pair of opposing second vacuum panels, at least one of the second vacuum panels including gripping structure, the second vacuum panels each having a second substantially constant radius of curvature as measured in a horizontal plane, the second substantially constant radius of curvature being substantially constant, excluding the gripping structure, from an upper end of each of the respective second vacuum panels to a lower end, and wherein a ratio of the second substantially constant radius of curvature to the maximum outer diameter is within a range of about 0.2 to about 2. 
     According to a second aspect of the invention, a plastic container includes a bottom portion; and a sidewall portion, the sidewall portion having a maximum outer diameter, and wherein the sidewall portion further includes a first pair of opposing first vacuum panels; and a second pair of opposing second vacuum panels, at least one of the second vacuum panels including gripping structure and being shaped so as to be asymmetric about a central vertical axis when viewed in side elevation. 
     These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevational view of a container that is constructed according to a preferred embodiment of the invention; 
         FIG. 2  is a first side elevational view; 
         FIG. 3  is a second side elevational view; 
         FIG. 4  is a cross-sectional view taken along lines  4 - 4  in  FIG. 1 ; 
         FIG. 5  is a cross-sectional view taken along lines  5 - 5  in  FIG. 1 ; and 
         FIG. 6  is a cross-sectional view taken along lines  6 - 6  in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring in particular to  FIG. 1 , a plastic container  10  that is constructed according to a preferred embodiment of the invention includes a bottom portion  12  and a sidewall portion  14 . Container  10  also preferably includes a neck portion  11  and a threaded finish portion  13 , as is typical in containers of this type. The sidewall portion  14  is preferably molded in a single unitary piece with the bottom portion  12  and the rest of the container  10  out of a plastic material such as PET, using an industry-standard process such as stretch blow molding. 
     Container  10  is adapted for use in hot-fill applications, but could potentially be used for other applications, and in particular those applications for which significant changes in internal container volume as a result of pressure and temperature differences are anticipated. 
     Sidewall portion  14  is preferably generally cylindrical and has a maximum outer diameter, D MAX , as is shown in  FIG. 1 . At the location of the maximum outer diameter D MAX , sidewall portion  14  is generally circular when viewed in horizontal cross-section. Sidewall portion  14  is preferably constructed so as to define a first pair of opposing first vacuum panels  16 ,  18 . 
     The first vacuum panels  16 ,  18  each preferably are shaped so as to define a first substantially constant radius of curvature R 1 , as measured in a horizontal plane, that is substantially constant from an upper end  24 ,  28  of each of the respective first vacuum panels  16 ,  18  to a lower end  26 ,  30  of the respective vacuum panels  16 ,  18 . 
     Preferably, a ratio of the first substantially constant radius of curvature R 1  to the maximum outer diameter D MAX  is within a range of about 0.3 to about 2.5. More preferably, the ratio of the first substantially constant radius of curvature R 1  to the maximum outer diameter D MAX  is within a range of about 0.4 to about 1.5. Most preferably, the ratio of the first substantially constant radius of curvature R 1  to the maximum outer diameter D MAX  is within a range of about 0.6 to about 0.9. 
     Sidewall portion  14  also preferably defines a second pair of opposing second vacuum gripping panels  20 ,  22 . As will be discussed in greater detail below, at least one of the second, gripping vacuum panels  20 ,  22  preferably includes gripping structure for facilitating secure gripping of the container  10  by a consumer. In the preferred embodiment, vacuum panel  20  is provided with a plurality of generally horizontally oriented concave grooves  42 ,  44 ,  46 ,  48  and  50 . Additionally, vacuum panel  22  is preferably provided with a plurality of generally horizontally oriented protruding ribs  52 ,  54 ,  56 ,  58  and  60  that are shaped and spaced so as to fit between the fingers of a typical consumer. 
     The second vacuum panels  20 ,  22  are each shaped in areas not including the ribs  52 ,  54 ,  56 ,  58  so as to define a second substantially constant radius of curvature R 2  as measured in a horizontal plane. The second substantially constant radius of curvature R 2  is substantially constant, excluding the above-described gripping structure, from an upper end  32 ,  36  of each of the respective second vacuum panels  20 ,  22  to a lower end  34 ,  38  of the vacuum panels  20 ,  22 . 
     Preferably, a ratio of the second substantially constant radius of curvature R 2  to the maximum outer diameter D MAX  is within a range of about 0.2 to about 2. More preferably, the ratio of the second substantially constant radius of curvature R 2  to the maximum outer diameter D MAX  is within a range of about 0.3 to about 1.5. Most preferably, the ratio of the second substantially constant radius of curvature R 2  to the maximum outer diameter D MAX  is within a range of about 0.5 to about 0.7. 
     In addition, the vacuum panels  16 ,  18 ,  20  and  22  are preferably shaped so that a ratio of the first substantially constant radius of curvature R 1  to the second substantially constant radius of curvature R 2  is within a range of about 0.15 to about 12.5. More preferably, the ratio of the first substantially constant radius of curvature R 1  to the second substantially constant radius of curvature R 2  is within a range of about 0.25 to about 5. Most preferably, the ratio of the first substantially constant radius of curvature R 1  to the second substantially constant radius of curvature R 2  is within a range of about 0.85 to about 1.8. 
     According to another aspect of the invention, at least one of the second, gripping pair of vacuum panels  20 ,  22  may be shaped so as to be asymmetric about a central vertical axis  62  when viewed in side elevation, as is shown in  FIGS. 2 and 3 . As will be described below, such asymmetry may advantageously correspond to the inherent asymmetry of the human hand when it is used to grip such a container. In addition, at least one of the second pair of vacuum panels  20 ,  22  may be shaped so as to have a width W U  as viewed in side elevation at its upper end  32 ,  36  that is different than the width W L  of the respective vacuum panel  20 ,  22  at its lower end  34 ,  38 . In the preferred embodiment, both of the vacuum panels  20 ,  22  are shaped so as to be asymmetric about their central vertical axis  62  when viewed in side elevation, and both are shaped so as to have a width W U  as viewed in side elevation at their upper ends  32 ,  36  that is different than the width W L  of the respective vacuum panel  20 ,  22  at its lower end  34 ,  38 . 
     In the preferred embodiment, both of the vacuum panels  20 ,  22  are wider at their upper ends than at their lower ends. Referring to  FIG. 3 , which is a side elevational view showing vacuum panel  22 , a ratio of the width W L  of the vacuum panel  22  at its lower end to the its width W U  at the upper end is within a range of about 0.35 to about 0.9. More preferably, the ratio of the width W L  as viewed in side elevation at the lower end to the width W U  at the upper end is within a range of about 0.45 to about 0.85. Most preferably, the ratio of the width W L  as viewed in side elevation at the lower end to the width W U  at the upper end is within a range of about 0.55 to about 0.75. 
     As was briefly described above, vacuum panel  20  is provided with a plurality of generally horizontally oriented concave grooves  42 ,  44 ,  46 ,  48  and  50 . Additionally, vacuum panel  22  is preferably provided with a plurality of generally horizontally oriented protruding ribs  52 ,  54 ,  56 ,  58  and  60  that are shaped and spaced so as to fit between the fingers of a typical consumer. As  FIG. 3  shows, respective first ends of the protruding ribs  52 ,  54 ,  56 ,  58  and  60  are preferably substantially aligned within a substantially vertical plane  64 . However, all of the protruding ribs  52 ,  54 ,  56 ,  58  and  60  are not of equal width. In the illustrated embodiment, the width of the protruding ribs becomes progressively less from the upper end  36  of the vacuum panel  22  to the lower end  38  of the vacuum panel  22 . This structure corresponds to the general reduction in finger length of the typical consumer from the forefinger to the little finger. 
     In addition, the protruding ribs  52 ,  54 ,  56 ,  58  and  60  are sized and spaced so that respective smooth spaces are defined therebetween for comfortably receiving the fingers of the typical consumer. A minimum vertical space L F  is therefore defined between adjacent ribs, which is preferably at least 0.5 inch, but is more preferably at least 0.55 inch. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.