Abstract:
A container has features to enable it to withstand pressure filling, including a smooth transition between its sidewalls and vacuum panel, no vertical stiffeners on the edges of the vacuum panels, and a gripping portion having wall either with small radial components or oriented at oblique angles. A pair of windows are included in the field portion of the vacuum panel outside of the gripping portion.

Description:
[0001]     This application claims priority to Provisional Application No. 60/774,168, filed Feb. 16, 2006 and incorporated herein by reference in its entirety. 
     
    
     BACKGROUND  
       [0002]     This invention relates to containers and more particularly to containers suitable for hot filling with perishable foods or beverages.  
         [0003]     Perishable foods, such as juices and soup, are often filled at an elevated temperature in a process generally referred to as “hot-fill.” In a typical hot-fill process, a perishable food or beverage is introduced into a plastic container at approximately 185° F. and a cap is applied to seal the container. Upon subsequent cooling of the contents, a negative pressure (that is, below atmospheric pressure) is formed within the container due to shrinkage of the contents. The container may also shrink upon being subjected to hot-filling temperatures, but the product contents generally shrink by a greater volumetric amount upon cooling than the decrease in container volume.  
         [0004]     In order to withstand the temperatures common to hot-filling, containers typically are formed of a thermoplastic having a relatively high intrinsic viscosity and typically are heat treated. For example, a container may be formed in a heated blow mold, which is maintained at approximately 250° F. to 290° F. A container that is held in a heated blow mold undergoes a decrease in the orientation of the polymer and an increase in its crystallinity, which diminishes the distortion of the container when subjected to hot-fill temperatures.  
         [0005]     Containers suitable for hot-filling applications typically are designed with vacuum panels formed in the container sidewall that flex in response to a decrease in internal pressure. For example, some plastic containers have several, equidistantly spaced vacuum panels that are configured to enable a circular label to be wrapped around the container. Land areas between the panels provide surfaces around which the label may be applied. Inward flexing of the vacuum panels in response to vacuum pressure prevent severe distortion of the land areas. Other plastic containers are configured to have opposing hand-grips that flex to absorb the internal vacuum. Flexing of the hand-grips in response to internal negative pressure prevents severe distortion of the surfaces to the front and to the rear of the hand-grips, which can receive labels.  
         [0006]     Even though hot-fill containers are configured to function under internal vacuum conditions, the containers are sometimes subjected to positive internal pressure during the filling process. For example, some filling equipment subjects the container to internal positive pressure for a brief period. Containers having long stiffening ribs or other long stiff structures (such as structures having a large moment of inertia, in transverse cross section relative to the horizontal axis) may, in response to positive internal pressure, locally bulge outwardly in a kink. And the kink might remain even after the container encounters internal vacuum or the kink may disappear but leave a wrinkle in the plastic wall. Even a wrinkle makes the container unappealing and is considered to be commercially detrimental.  
         [0007]     Typically, the specifications for such processes require the containers to withstand internal positive pressures of up to 3 psi. It is possible, however, for a pressure filling line to stop during the filling process, for example under unexpected or alarm conditions, and subject the container being filled to a filling pressure of greater than 3 psi.  
       SUMMARY OF THE INVENTION  
       [0008]     Provided is a container capable of being hot filled with a product, sealed while the product is hot, and allowed to cool, thereby creating an internal vacuum. The container has improved positive pressure resistance during pressure filling and yet has sufficient vacuum absorption capabilities. The container has an enclosed base, a body having a sidewall that extends upwardly from the base, and an upper portion extending upwardly from the body to a finish on which a closure may be applied. The container also includes a pair of opposing vacuum panels disposed between front and rear portions of the sidewall of the body. The container has relatively smooth transitions between its vacuum panels and the front and rear portions of the sidewall and the container does not have vertical reinforcing ribs such that the radial dimension is small for each portion of the front and rear edges of the panel.  
         [0009]     The vacuum panels have a generally flat field that transitions smoothly into the front and rear portions of the sidewall. Also, the vacuum panels each include a handgrip and a pair of inwardly extending windows formed at least partly in the field generally below the handgrip. The handgrip includes a gripping surface and at least a proximal wall and a distal wall. The gripping surface is adapted to receive a user&#39;s fingers on one of the vacuum panel handgrips and a user&#39;s thumb on the opposing one of the vacuum panel handgrips.  
         [0010]     The proximal wall of the handgrip preferably merges smoothly with the rear portion of the sidewall The distal wall forms an oblique long wall angle A 1  with a vertical line in elevational view and a short wall angle A 2  with the field in transverse cross section. The long wall angle Al is preferably between approximately 10 degrees and approximately 25 degrees. The short wall angle A 2  is preferably between approximately 85 degrees and approximately 115 degrees. Further, where structure having a substantially radial orientation is included, such as in the distal wall of the gripping surface, the radial component preferably has a relatively short vertical length in elevational view and is nearly radially oriented in transverse cross section. The container is designed to preferably achieve a failure mode in the form of a bulge in the handgrip distal wall when the container is subjected to a positive internal pressure. Preferably, the container can withstand and internal positive pressure of between 3.5 and 7.5 psi.  
         [0011]     Also, provided is a method of hot-filling a bottle. According to the method, a bottle that is designed in accordance with the above description of the container is filled with contents at an elevated temperature and at a positive pressure of up to 9.0 psi. Then, the bottle is capped while the contents are still at an elevated temperature and the contents of the capped bottle are allowed to cool, which causes the vacuum panels to deflect inwardly in response to the cooling and shrinking of the contents.  
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0012]      FIG. 1  is a side elevational view of a bottle illustrating features of the present invention;  
         [0013]      FIG. 2  is a front elevational view of the bottle of  FIG. 1 ;  
         [0014]      FIG. 3  is a transverse cross sectional view of the bottle of  FIG. 1  taken through lines III-III in  FIG. 1 ;  
         [0015]      FIG. 4  is an enlarged view of a portion of the bottle shown in  FIG. 1 ;  
         [0016]      FIG. 5A  is a transverse cross sectional view of the container taken through lines V-V in  FIG. 1  and illustrating the bottle bulging in response to positive internal pressure;  
         [0017]      FIG. 5B  is a transverse cross sectional view of the bottle taken through lines V-V in  FIG. 1  and showing the bottle after hot filling;  
         [0018]      FIG. 6  is a graphical representation of a finite element analysis of deflection of the bottle of  FIG. 1  illustrating the bottle bulging in response to positive internal pressure;  FIG. 6  shows the same condition as shown in  FIG. 5A ; and  
         [0019]      FIG. 7  is a graphical representation of a finite element analysis of stress of the bottle of  FIG. 1  illustrating the bottle&#39;s response to internal vacuum. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0020]     A bottle  10  includes an enclosed base  12 , an upper portion  14 , and a body  16  extending between base  12  and upper portion  14 , as best shown in  FIGS. 1, 2 ,  6 , and  7 . Bottle  10  is generally suitable for use in a hot-filling process, in which bottle  10  is filled with a product at an elevated temperature, capped, and allowed to cool. Typically, bottle  10  is formed by an injection blow molding process, but the present invention is not limited by the method of forming the bottle.  
         [0021]     Base  12  preferably is conventional and includes a reentrant portion  20  (shown only in dashed lines in  FIG. 2 ), a standing ring  22 , and a heel  24 . Base  12  terminates in a shoulder  26 . Upper portion  14  includes an upper shoulder  28 , a waist  30 , a dome  32 , and a finish  34 . Finish  34  includes threads for receiving corresponding threads of a closure  36  (shown  FIGS. 6 and 7 ). Upper shoulder  28  is located at the boundary between upper portion  14  and body  16 . Waist  30  is a portion of reduced diameter located above shoulder  28  and below dome  32 . Dome  32  diminishes in diameter as it upwardly extends toward finish  34 . In the figures, dome  32  is illustrated with structural elements, but neither these structural elements nor any other aspect of upper portion  14  is intended to be limiting unless expressly recited in the claims.  
         [0022]     Body  16  includes a sidewall  38  and a pair of opposing vacuum panels  56 . Sidewall  38  generally extends between shoulders  26  and  28  and preferably includes a front portion  42  and a rear portion  44 . Front portion  42  and rear portion  44  preferably include horizontal stiffening ribs  46   a  and  46   b , respectively. Preferably, neither front portion  42  nor rear portion  44  have horizontal stiffening ribs. Front portion  42  preferably a surface capable of receiving a label. The label surface of front panel  42  is generally straight in longitudinal cross section, but it is expected and acceptable for the longitudinal cross section of front portion  42  to deflect slightly in response to internal pressures within bottle  10 . The desired magnitude of the deflection of front panel  42  is governed by label considerations, as will be understood by persons familiar with labeling technology for hot fill containers.  
         [0023]     Stiffening ribs  46   a  and  48   b  are curved to match the curvatures of panels  42  and  44 , respectively, and terminate at ends  48   a  and  48   b , respectively. Preferably, sidewall  38  extends, rearward and arcuately, past ribs ends  48   a  of front portion  42 ; and sidewall  38  extends, frontward and arcuately, past rib ends  48   b  of rear portion  42 ; which portions of the sidewall are referred to a sidewall intermediate portions  50   a  and  50   b , respectively. Preferably, sidewall intermediate portions  50   a  and  50   b  (i) do not have vertical stiffening ribs, or (ii) have ribs that have only a small vertical component (such as curved ribs or ribs forming an oblique angle with a vertical line), or (iii) have only horizontal ribs, or (iv) have stiffening structure that is part of a three dimensional window (described more fully below) and that has a small vertical dimension.  
         [0024]     Each vacuum panel  40  includes a field  56  that is defined by the panel&#39;s front edge  58   a  and its opposing rear edge  58   b .  FIG. 1  and  FIG. 4  show panel edges  58   a  and  58   b  in dashed lines to schematically show the boundaries of the vacuum panel, as the boundary in the physical version of bottle  10  is not pronounced, which is evident in  FIG. 3 . Field  56  is generally planar in its as-molded state, but may also be curved.  
         [0025]     Each panel  40  also includes a handgrip  60  and a pair of inwardly directed first window  90  and second window  96 . Handgrip  60  includes a gripping surface  62  that preferably includes a pair of ribs  64 . Handgrip  60  is defined by a proximal wall  66 , a distal wall  68 , an upper wall  70 , and a lower wall  72 . Walls  66 ,  68 ,  70 , and  72  are joined by transitions  74   a ,  74   b ,  74   c , and  74   d  as shown in  FIG. 4 .  
         [0026]     Gripping surface  60  preferably is flat except for a pair of ribs  64  that protrude outward from the remainder of the surface. Proximal wall  66  preferably is curved in transverse cross section, such as illustrated in  FIGS. 5A and 5B , and preferably is located at the boundary of panel  40  and sidewall rear intermediate portion  50   b . The smooth transition between the surfaces of gripping surface  60  and sidewall  50   b  may comfortably receive a user&#39;s hand and, as described above, forgoes a vertical rib.  
         [0027]     Distal wall  68  is on the opposite side of gripping surface  60  from proximal wall  66  and preferably is inclined at an angle from a vertical line by and angle A 1 , which will be referred to herein as the long wall angle. Preferably, angle A 1  preferably is not 0° (that is, not vertical), preferably is between approximately 10 degrees and approximately 20 degrees, and more preferably, as illustrated in  FIG. 4 , approximately 15 degrees for the particular bottle shown. The upper ends of proximal wall  66  and distal wall  68  are connected by upper wall  70  that, for ease of hand placement, is oriented at an oblique angle to a horizontal reference line, as shown in  FIG. 4 . The lower ends of proximal wall  66  and distal wall  68  are connected by lower wall  72 , which also is oriented at an oblique angle.  
         [0028]     As shown in  FIG. 3 , distal wall  68  is formed by a main wall surface  76  and a pair of curved wall transitions  78   a  and  78   b . An inner wall transition  78   a  merges the inner edge of main wall  76  and gripping surface  62  and; an outer wall transition  78   b  merges the outer edge of main wall  76  and panel field  56 . As shown in  FIG. 3 , main wall surface  76  is oriented relative to gripping surface  60  by an angle A 2  that preferably is approximately 90 degrees. The inventors surmise that angle A 2  may be (preferably) as large as 115 degrees while maintaining the advantage of resisting kinking during position pressure. Angle A 2  may be as small as 85 degrees, as angles smaller than 90 degrees may provide an undercut surface that diminishes local wall thickness upon blowing. As will be clear to persons familiar with container development and design, angle A 2  may vary according to container dimensions, wall thickness, positive pressure design point, and like parameters. Accordingly, the present invention may encompass wall angles A 2  outside of the above range.  
         [0029]     Also, the depth of gripping surface  64  (measured radially from the deepest point of surface  64  to the hypothetical extension of the panel field  46 ), which is shown schematically as dimension D in  FIG. 3  preferably is greater than approximately 0.050 inches, and more preferably greater than approximately 0.100 inches. The depth most preferably is approximately 0.200 inches. Depth D has an inverse relationship with the variables of distal wall length L, such that the preferred length L preferably diminishes with increasing depth D.  
         [0030]     All angle magnitudes provided herein are based on the bottle prior to filling. The wall angles may be chosen according to the overall container and panel size, wall thickness, blow molding parameters, and the like, as will be understood by persons familiar with blow molded bottle engineering.  
         [0031]     Preferably, a first window  90  and a second window  96  are provided in the panel field  56 . First window  90  has substantially straight edges  92  that merge panel field  56  with a window bottom surface  94 . Preferably window bottom surface  94  is substantially flat. Second window  96  has substantially straight edges  98  that merge panel field  56  with a window bottom surface  100 . The window edges  92  may be parallel to form a rectangle or square in elevational view, such as is illustrated by window  90 . As illustrated by second window  96 , the windows are not required to have a rectangular shape, as window  96  includes an extended portion  102  that extends upward to diminish the area of unreinforced field  56 . As shown in the Figures, window  102  may extend outside of boundaries of panel  40 .  
         [0032]     Preferably, the vertical dimension of any radial structure in the panel  40  and vertical components of structure in the intermediate sidewalls  50   a  and  50   b , such as the walls of window  102 , have relatively small dimensions. The overall length L of distal main surface  76  is shown in  FIG. 4 . Preferably, the overall length L is less than 3.5 inches, and more preferably less than 3.0 inches. The lower magnitude of the preferred range of length L is dictated by ergonomic factors, and may be as low as approximately 1.25 inches. Further, the container vertical component L′ of the length L is preferably less than about 3.0 inches, and more preferably less than 2.5 inches. Preferably, the vertical component of all other structures in the panel  40  or sidewall intermediate portions  50   a  and  50   b  is less than length L.  
         [0033]     The dimensions herein are provided for the container shown having a sidewall diameter of approximately 4.5 inches and sidewall height (that it, between shoulders  26  and  28 ) of approximately 5.6 inches such that the container volume is 64 ounces. The dimensions and angles provided are not intended to limit the scope of the invention unless expressly set forth in the claims.  
         [0034]      FIG. 5  graphically shows calculated deformation of the bottle  10  upon internal pressurization, assuming a constant wall thickness and wall temperature of 185 degrees ° F. The bulge or kink forms at or near the gripping surface distal wall  68  at 6.6 psi for a 64 ounce container having the dimensions stated above and weighing approximately 80 to 85 grams. The deformation graphic of  FIG. 5  shows the effectiveness of bottle  10  in deforming relatively uniformly throughout its body except for the grip.  
         [0035]      FIG. 6  graphically shows calculated deformation of the bottle  10  upon vacuum filling at 185 degrees ° F. after the container has cooled to room temperature. As shown, the maximum magnitude of deformation is in field  56 .  
         [0036]     The present invention is illustrated by structure and function disclosed herein, and is not limited to the particular structure and function, but rather is limited according the claims. Further, advantages of the bottle  10  are provided in the context of pressure filling, and the present invention is not limited to any pressure filling process, but rather to any hot fill container having the claimed structure.