Abstract:
A plastic container includes a plastic body having a polygonal sidewall contour with rounded corners on a cylinder of revolution and flat panels extending between the corners chordally of the cylinder of revolution. In the preferred embodiments of the invention, a label is disposed on an exterior surface of at least one of the flat panels, and most preferably extends circumferentially around the exterior surface of the container sidewall. Upon filling the container with hot liquid and capping the container, the flat panels bow radially inwardly as the liquid cools. However, any labeling placed on the container, either before or after cooling, is secured to the panels as well as the rounded corners, and does not wrinkle or crinkle during storage or use.

Description:
[0001]    The present invention is directed to hot-fill container packages, and more particularly to a container, a package and a method making the package, which are particularly well suited for hot-fill applications.  
         BACKGROUND AND SUMMARY OF THE INVENTION  
         [0002]    In so-called hot-fill packages, a container is filled with hot liquid product and capped while the liquid product is still hot. As the liquid cools, the reduction in liquid volume creates a vacuum within the package (i.e., an internal pressure that is less than the surrounding atmospheric pressure). A label may be applied to an exterior surface of the container either before or after filling.  
           [0003]    When the container is of relatively rigid construction, such as glass construction for example, the hot-fill process does not present a problem relative to distortion of the container because the container sidewall is strong enough to withstand the forces resulting from the pressure differential between the container exterior and interior. However, when the container is of less rigid construction, such as molded plastic for example, the container sidewall distorts inwardly as the liquid cools. It has been proposed to provide vacuum panels in the container sidewall to absorb the distortion as the liquid product cools, leaving the remainder of the sidewall relatively undistorted. However, the corner or post areas in containers of this type tend to be relatively weak, and can become dented during the production process. Furthermore, any label applied to the container undesirably “crinkles” in a user&#39;s hand because of the absence of contact and adhesion entirely around the container sidewall. It is therefore an object of the present invention to provide a container, a closure and container package and a method of making such a package, which are particularly adapted for use in hot-fill applications, which accommodate creation of the vacuum within the container as the product cools without substantially distorting the overall package envelope, and in which any labeling on the container remains secured to the container without wrinkling or crinkling during use.  
           [0004]    The present invention embodies a number of different aspects, which can be implemented separately from or more preferably in combination with each other.  
           [0005]    A plastic container in accordance with a first aspect of the invention includes a plastic container body having a polygonal sidewall contour with rounded corners on a cylinder of revolution and flat panels extending between the corners chordally of the cylinder of revolution. The polygonal sidewall contour preferably is selected from the group consisting of square and pentagonal. A label may be located on an exterior surface of at least one of the panels, and extends circumferentially around an exterior surface of the sidewall. When the container is filled with hot liquid and thereafter cools, the flat panels bow radially inwardly. However, any labeling on the flat panels, placed before or after filling, is in contact and adheres to a smooth continuous surface, and does not wrinkle or crinkle during use.  
           [0006]    In accordance with a second aspect of the present invention, a plastic container includes a plastic body having a polygonal sidewall contour with rounded corners on a cylinder of revolution and flat panels extending between the corners chordally of the cylinder of revolution. In the preferred embodiments of the invention, a label is disposed on an exterior surface of at least one of the flat panels, and most preferably extends circumferentially around the exterior surface of the container sidewall, either before or after filling. Upon filling the container with hot liquid and capping the container, the flat panels bow radially inwardly as the liquid cools. However, any labeling placed on the container remains secured to the flat panels as well as the rounded corners, and does not wrinkle or crinkle during storage or use.  
           [0007]    A filled closure and container package in accordance with a third aspect of the invention includes a plastic container having a body and a finish, a liquid product within the interior of the container body, and a closure applied to the finish. The body interior is under vacuum and sealed by the closure. The container body has a cross section that includes rounded corners and concave panels extending between the corners. A label is adhered to an exterior surface of at least one of the container sidewall panels, either before or after filling the container, and assumes the concave contour of the panel exterior surface. In the preferred embodiments of the invention, the label comprises a sheet label extending entirely around the exterior surface of the container body and being adhered to the corners and the concave panels.  
           [0008]    A method of making a package in accordance with yet another aspect of the invention includes providing a container having a plastic body with a polygonal sidewall, rounded corners on a cylinder of revolution and flat panels extending between the corners chordally of the cylinder of revolution. The container is filled with hot liquid, capped and allowed to cool so that the flat panels distort radially inwardly due to creation of a vacuum as the liquid cools within the container. A label is adhesively applied to the container sidewall, either before filling the container with hot liquid or after filling and the contents cool, such that the label is adhered to an exterior surface of the corners and the panels. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The invention, together with additional objects, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:  
         [0010]    [0010]FIG. 1 is a side elevational view of a labeled closure and container package in accordance with one exemplary but presently preferred embodiment of the invention;  
         [0011]    [0011]FIG. 2 is an elevational view of the container in FIG. 1 prior to filling and capping;  
         [0012]    [0012]FIG. 3 is a perspective view of the container illustrated in FIG. 2;  
         [0013]    [0013]FIG. 4 is a sectional view taken substantially along the line  4 - 4  in FIG. 2;  
         [0014]    [0014]FIG. 5 is a schematic diagram of the container cross section in FIG. 4 illustrating forces applied thereto during cooling of the package contents;  
         [0015]    [0015]FIG. 6 is a schematic sectional view similar to that of FIG. 5 but showing distortion of the container sidewall during cooling;  
         [0016]    [0016]FIG. 7 is a sectional view taken substantially along the line  7 - 7  in FIG. 1 showing the final cross sectional contour of the closure and container package after cooling;  
         [0017]    [0017]FIG. 8 is a perspective view of an unlabeled and unfilled container in accordance with another aspect of the present invention;  
         [0018]    [0018]FIG. 9 is a sectional view of the container sidewall in FIG. 8;  
         [0019]    [0019]FIG. 10 is a view, similar to that of FIG. 6, of the container in FIGS.  8 - 9  after filling;  
         [0020]    [0020]FIG. 11 is a sectional view, similar to that of FIG. 9, but illustrating another embodiment of the invention; and  
         [0021]    [0021]FIG. 12 is a sectional view, similar to that of FIG. 10, but of the embodiment of FIG. 11. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]    [0022]FIG. 1 illustrates a closure and container package  20 , in accordance with one exemplary embodiment of the invention, as including a container  22  and a closure  24 . Container  22  is of molded plastic construction, such as blow-molded PET construction, and includes a shoulder portion  25 , a bottom or heel portion  26  and a sidewall  28  extending entirely around the container between the shoulder and bottom portions. Shoulder and bottom portions  25 ,  26  may be of any suitable construction, preferably having a circular contour as viewed from the axial direction to operate as “bumpers” during handling of the container and package. Closure  24  may be of any suitable construction, such as molded plastic construction, for sealing the interior of container  22 . A sheet label  30  extends around the exterior surface of container sidewall  28 .  
         [0023]    FIGS.  2 - 3  illustrate container  22 , prior to filling and capping, in accordance with one exemplary embodiment of the invention. Shoulder and bottom portions  25 ,  26  and sidewall  28  form a container body  32  from which a finish  34  extends for securement of closure  24  (FIG. 1). The geometry of finish  34  illustrated in FIGS. 2 and 3 is strictly exemplary. As viewed in diametric cross section (FIG. 4) prior to filling, sidewall  28  is of polygonal contour, preferably either pentagonal as shown or square. The contour of sidewall  28  includes angularly spaced rounded posts or corners  34  and flat panels  36  that extend between corners  34 . Rounded corners  34  lie on a cylinder of revolution  38  (FIG. 5), and flat panels  36  extend chordally across such cylinder of revolution. Container sidewall  28  preferably is of substantially uniform wall thickness entirely around the sidewall. There is a smooth transition from corners  34  to panels  36 , which is to say that there are no ribs or channels that separate these portions of the sidewall. In the embodiment of the invention illustrated in FIGS.  2 - 4 , label  30  is exteriorly applied to container sidewall  28  prior to filling. Label  30  preferably is in the form of a rectangular sheet that extends entirely around sidewall  28 , and may comprise a pressure-sensitive self-adhesive sheet label that is rolled onto the container. However, as will be described later, label  30  may be applied to the container after filling, either before or after cooling of the container contents. It is also within the scope of the present invention in its broadest aspects, although not presently preferred, to employ spot labels applied to one or more of the panels  36  only.  
         [0024]    [0024]FIG. 5 illustrates force vectors acting on container sidewall  28  following filling and capping of the container and as the container contents cool. Stress forces F act entirely around the container sidewall due to the pressure differential between the container exterior (normally ambient pressure) and the container interior as the liquid product cools. At panels  36 , these stress forces F are perpendicular to the plane of each panel. At the corners  34 , however, the forces F are divided into geometric components, each of which is less than F. As a result, the centers of the panels collapse under vacuum, and the volume reduction from the panel collapse eliminates the vacuum within the container and preserves the geometries of the corners. Thus, sidewall panels  36  assume an outwardly concave contour  36  illustrated in FIG. 6, while the corners  34  move radially inwardly a slight amount from the original or first cylinder of revolution  38  to a final or second cylinder of revolution  40 . Panels  36  have a uniform radius of curvature  41 , all panels  36  and radii  41  preferably being identical. Label  30 , being adhered to the exterior surface of the container sidewall, follows the inward movement of the container corner and panel areas, stretching as required to accommodate inward flexing of the container sidewall panels but without becoming separated from the container sidewall panels or corners. The amount of radially inward flexure is dependent upon a number of factors, including initial product temperature, sidewall strength, overall container geometry, etc. FIG. 7 illustrates the final contour of container sidewall  28  with attached label  30  and container contents  42 .  
         [0025]    As noted above, FIGS.  2 - 4  illustrate label  30  having been applied to empty container  22 , such as by the container manufacturer. Label  30  may be a self-adhesive pressure-sensitive label that is rolled onto the sidewall of the container following the molding operation. As an alternative, the label may be applied by the packager after filling and capping of the container, but before the container contents have an opportunity substantially to cool, so that the container sidewall geometry remains substantially the same as the original geometry and has not yet had an opportunity to distort toward the geometry of FIGS. 6 and 7. When the label is applied by the product packager, a roll-on pressure-sensitive label or a heat-shrinkable label sleeve may be employed. It is also envisioned that individual spot labels may be applied to the flat panels of the container sidewall, although this would not be preferred because of additional expense. As another alternative, which is presently preferred, the label may be applied by the packager after filling, capping and washing, when the container is at or near room temperature and the panels have bowed inwardly. A heat-shrinkable sleeve label is preferred for this application. This alternative has the advantage that the label will not become damaged or dirty during shipping and handling of the empty container, or during filling, capping and washing of the container.  
         [0026]    FIGS.  8 - 9  illustrate a container  22   a , which is similar to container  22  of FIGS.  1 - 7  but is unlabeled. In this embodiment, the label (not shown) is heat-shrunk onto the container after it is hot-filled, capped and washed, and after the filled container cools to room temperature (FIG. 10) and the panels have bowed inwardly.  
         [0027]    FIGS.  11 - 12  illustrate a square container  50  having corners  52  on a circle of revolution  54  and flat panels (as molded)  56  that extend between the corners chordally of cylinder  54 . After filling with hot product  42  (FIG. 12), corners  52  move to a smaller cylinder of revolution  58 , and panels  56  bow radially inwardly. Panels  56  have a uniform radius of curvature  60 , all panels  56  and radii  60  preferably being identical. A label (not shown) may be applied before filling (FIG. 11), or more preferably after filling, capping, washing and cooling (FIG. 12) when the panels have bowed inwardly.  
         [0028]    Container sidewall panels  36 ,  56  have been described as “flat,” which is the preferred configuration of these panels as molded. That is, the panels  36 ,  56  as initially molded should be substantially flat or planar, without substantial concavity or convexity. If the panels  36 ,  56  have substantial outward convexity, radial inward bowing of the panels as the package cools would apply outward forces to the corners of the container, tending to expand rather than contract the container sidewall and possibly leading to buckling and formation of waves in the sidewall panel contours. Likewise, substantial concavity in the panels  36 ,  56  as molded would make it difficult to apply labels to the containers without trapping air beneath the labels, which would create the wrinkles and crinkle-feel in the labels which the present invention seeks to eliminate. It should also be noted that the inward bending of the sidewall panels  36 ,  56  under internal vacuum pressure may become permanent in whole or in part due to creep of the plastic material of the sidewall, which would have no effect upon the present invention.  
         [0029]    There have thus been disclosed a container, a package and a method of making a package that filly satisfy all of the objects and aims previously set forth. The invention has been described in conjunction with presently preferred embodiments thereof, and a number of modifications and variations have been discussed. Other modifications and variations will readily suggest themselves to persons of ordinary skill in the art. The invention is intended to embrace all such modifications and variations as fall within the spirit and broad scope of the appended claims.