Patent Publication Number: US-2015076163-A1

Title: Reinforced plastic containers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and is a continuation of U.S. patent application Ser. No. 13/720,569, filed Dec. 19, 2012; and claims priority to and is a continuation-in-part of International Patent Application No. PCT/US13/43385, filed May 30, 2013, which is a continuation of U.S. patent application Ser. No. 13/483,249, filed May 30, 2012, now U.S. Pat. No. 8,783,505, the contents of each of which are hereby incorporated by reference in their entireties and priority to each of which is claimed. 
    
    
     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 require reinforcement against deflection as a result of internal volumetric changes or the weight of the contents of the container. 
     2. Description of the Related Technology 
     Plastic containers such as those that are manufactured using the extrusion blow molding process need to possess the requisite strength to limit sidewall and bottom deflection to stay within predetermined tolerances in response to forces that are applied during the filling process and during handling within the supply chain and by the consumer. Hot fill type plastic containers typically include vacuum panel areas having vacuum panels specifically designed to accommodate deflection as a result of the volumetric expansion and contraction that occurs during the filling process. However, it is desirable to minimize deflection in sidewall and bottom portion areas of a hot fill container other than in the vacuum panels in order to preserve the structural integrity of the container. 
     The bottom portion of a plastic container also needs to process sufficient strength to resist deformation as a result of pressurization changes within the container and from the forces that are applied by the weight of the container contents. In hot fill type containers, it is also important for the bottom portion to have sufficient rigidity so that vacuum uptake is directed mainly to the vacuum panels that are designed for such purposes. 
     In certain types of plastic containers, such as those that are manufactured using the stretch reheat blow molding process, a certain amount of reinforcement is inherently provided by the concave shape of the bottom portion. Concavity can also be designed into the bottom portion of an extrusion blow molded plastic container, but this sacrifices space efficiency and increases material costs. The extrusion blow molding process permits the fabrication of the container that has a substantially flat bottom. Extrusion blow molded containers that have a substantially rectangular profile when viewed in transverse cross-section have been manufactured with corrugated substantially flat bottoms for use in limiting the deflection of the bottom of the container as a result of the weight of solid materials within the container. However, to the inventor&#39;s knowledge no such bottoms have been used when the container that is substantially round when viewed in transverse cross-section, or in hot fill applications. 
     A need exists to provide a plastic container that effectively directs vacuum uptake to the intended portions of the container, and that limits deflection of the bottom portion as a result of pressurization changes within the container and the weight of the container contents. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to provide a plastic container that effectively directs vacuum uptake to the intended portions of the container, and that limits deflection of the bottom portion as a result of pressurization changes within the container and the weight of the container contents. 
     In order to achieve the above and other objects of the invention, a hot fill type plastic container according to a first aspect of the invention includes a finish portion defining an opening, a bottom portion and a main body portion having a vacuum panel area with at least one vacuum panel defined therein. The vacuum panel is constructed and arranged to deflect in order to accommodate volumetric expansion and contraction during the hot fill process. The main body portion further includes a circumferentially extending reinforcement groove having reinforcement structure provided therein. The circumferentially extending reinforcement groove is positioned substantially adjacent to the vacuum panel area, whereby dimensional distortion of at least part of the main body portion that is adjacent to the vacuum panel area is minimized during hot fill process. 
     A hot fill type plastic container according to a second aspect of the invention includes a finish portion defining an opening, a bottom portion that is substantially round when viewed in bottom plan and a main body portion having a vacuum panel area with at least one vacuum panel defined therein. The vacuum panel is constructed and arranged to deflect in order to accommodate volumetric expansion and contraction during the hot fill process. The bottom portion is constructed and arranged to include a substantially flat portion having a plurality of alternating parallel ribs and grooves defined therein. As a result, dimensional distortion of the bottom portion is minimized during the hot fill process and deflection as a result of vacuum uptake is directed toward the vacuum panel area. 
     A polypropylene container according to a third aspect of the invention includes a finish portion defining an opening, a main body portion having a vacuum panel area defined therein and a bottom portion that is fabricated from polypropylene and that is substantially round when viewed in bottom plan. The bottom portion is constructed and arranged to include a substantially flat portion having a plurality of alternating parallel ribs and grooves defined therein. As a result, dimensional distortion of the bottom portion is minimized. 
     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 first perspective view of a plastic container that is constructed according to a preferred embodiment of the invention; 
         FIG. 2  is a side elevational view of the plastic container that is shown in  FIG. 1 , 
         FIG. 3  is a longitudinal cross-sectional view taken along lines  3 - 3  in  FIG. 1 ; 
         FIG. 4  is a transverse cross-sectional view taken along lines  4 - 4  in  FIG. 2 ; 
         FIG. 5  is a transverse cross-sectional view taken along lines  5 - 5  in  FIG. 2 ; 
         FIG. 6  is a second side elevational view of the plastic container that is shown in  FIG. 1 ; 
         FIG. 7  is a fragmentary cross-sectional view taken along lines  7 - 7  in  FIG. 6 ; 
         FIG. 8  is a rear elevational view of the container that is depicted in  FIG. 1 ; 
         FIG. 9  is a front elevational view of the container that is depicted in  FIG. 1 ; 
         FIG. 10  is a top plan view of the container that is depicted in  FIG. 1 ; 
         FIG. 11  is a bottom plan view of the container that is depicted in  FIG. 1 ; 
         FIG. 12  is a cross-sectional view taken along lines  12 - 12  and  FIG. 11 ; 
         FIG. 13  is a bottom perspective view of the container that is depicted in  FIG. 1 ; 
         FIG. 14  is a finite element analysis image comparison illustrating the top load performance benefits of the container that is constructed according to the preferred embodiment of the invention; 
         FIG. 15  is a graph depicting the improvement in top load performance that is exhibited by a container that is constructed according to the preferred embodiment of the invention; and 
         FIG. 16  is a table comparison demonstrating the improvement in bottom deflection performance in a container that is constructed according to the preferred embodiment of the invention. 
     
    
    
     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 is preferably fabricated from polypropylene using a conventional extrusion blow molding process. Plastic container  10  in the preferred embodiment is designed for use with a conventional hot fill process. Plastic container  10  includes a finish portion  12  that defines an opening  14  that is in communication with the interior of the container  10 . Plastic container  10  further includes a bottom portion  16 , which will be described in greater detail below. 
     Plastic container  10  also includes a main body portion  18  having a vacuum panel area  20 , each of which includes a vacuum panel  22  having inner portion  24  and an outer portion  26 . The vacuum panel area  20  is preferably recessed with respect to an outer sidewall  28  of the main body portion  18 . As  FIG. 5  shows, the outer portions  26  of the vacuum panels  22  are substantially flat and substantially perpendicular to a radius extending from a longitudinal axis  25  of the container  10 . The inner portions  24  of the vacuum panels  22  are constructed so as to be slightly convex and are designed to flex inwardly when an under pressure exists within the container  10  during the hot fill process. 
     The vacuum panel area  20  further includes transition portions  30  that connect the outer portions  26  of the vacuum panels  22  to the outer sidewall  28  of the main body portion  18 . 
     Plastic container  10  further includes a dome or shoulder portion  32  that connects the finish portion  12  to the main body portion  18 . In the preferred embodiment, the dome portion  32  is provided with a handle  38  that is constructed and arranged to facilitate a single finger grip. 
     Container  10  is preferably a round container, meaning that its outermost surfaces as viewed in transverse cross-section are substantially circular. This may best be seen in  FIGS. 4 and 5 . 
     The main body portion  18  further preferably includes a circumferentially extending reinforcement groove  34  that has reinforcement structure  36  provided therein. The reinforcement groove  34  imparts additional top load strength of the container  10 , as well as hoop strength, meaning that it stabilizes adjacent portions of the sidewall of the container  10  against radial displacement as a result of internal pressurization changes and squeezing forces that may be applied to the container  10  during handling or by a consumer. 
     The circumferentially extending reinforcement groove  34  is preferably shaped and proportioned the same as those that are disclosed in U.S. patent application Ser. No. 13/483,249, filed May 30, 2012, the entire disclosure of which is hereby incorporated by reference as if set forth fully herein. 
     The reinforcement groove  34  is preferably positioned substantially adjacent to the vacuum panel area  20  in order to minimize dimensional distortion of the sidewall of the main body portion  18  adjacent to the vacuum panel area  20  during the hot fill process. Preferably, the reinforcement groove  34  is positioned within a distance L1 of the vacuum panel area  20  that is substantially no greater than about 34 millimeters, more preferably substantially no greater than about 22 millimeters and most preferably substantially no greater than about 14 millimeters. 
     In the preferred embodiment, the reinforcement groove  34  includes a plurality of flutes  40  that are situated within the groove  34 . Each of the flutes  40  preferably has a vertical component, and more preferably is oriented so as to be substantially vertical. The reinforcement groove  34  preferably extends about an entire circumference of the main body portion  18 . 
     As  FIG. 4  shows, the flutes  40  are preferably defined by alternating convex outer surfaces  43  and concave surfaces  42 . The main body portion  18  has a maximum lateral dimension W MAX , as is also shown in  FIG. 4 . The reinforcement groove  34  has a minimum depth D MIN  and a maximum depth D MAX  as measured from the outer sidewall  28 , with a minimum depth D MIN  being defined at the peaks of the convex surfaces  43  and the maximum depth D MAX  being defined at the radially innermost points of the concave troughs that are formed by the concave surfaces  42 . 
     Preferably, a ratio D MIN /D MAX  of the minimum depth of the maximum depth is substantially within a range of about 0.1 to about 0.9, more preferably substantially within a range of about 0.2 to about 0.8 and most preferably substantially within a range of about 0.35 to about 0.65. 
     As  FIG. 7  shows, the circumferentially extending reinforcement groove  34  as viewed in side profile or longitudinal cross-section has a first upper groove sidewall  47  that is angled with respect to a groove bottom  48  at a first angle and a second lower groove sidewall  49  that is angled with respect to the groove bottom  48  that a second angle. In the preferred embodiment, the first and second angles are preferably substantially the same. In addition, the first upper groove sidewall  47  defines a wedge angle A 1  with respect to the second lower groove sidewall  49  that is preferably substantially within a range of about 15° to about 45° and more preferably substantially within a range of about 20° to about 40°. 
     The presence of the circumferentially extending reinforcement groove  34  materially improves both the top load and pressure resistance performance of the container in comparison to a similar container that does not include such a reinforcement groove  34 .  FIG. 14  is a finite element analysis comparison depicting the relative deflections under a top load force between a container, shown on the left, which does not include a reinforcement groove  34  and the container that is constructed according to the preferred embodiment, which is shown on the right. The darker coloration of the container that is shown on the right is representative of a lessened amount of deflection relative to the container on the left. 
       FIG. 15  is a graphical depiction of the relative top load performance of the containers shown on the left and right, respectively, in  FIG. 14 . The horizontal axis in  FIG. 15  represents displacement, while the vertical axis represents a top load force that is applied to the container. The container that is shown on the left in  FIG. 14 , which does not include a profiled reinforcement groove  34 , as indicated as the “original structure” in  FIG. 15 . The container that is shown on the right in  FIG. 14  is constructed according to the preferred embodiment of the invention and does include a reinforcement groove  34 , is indicated as the “final structure” in  FIG. 15 . As  FIG. 15  shows, a significant improvement in top load performance is achieved by the inclusion of the profiled reinforcement groove  34 . 
     Referring now to  FIGS. 11 and 13 , it will be seen that the bottom portion  16  is constructed and arranged to include a substantially flat portion  52  that has a plurality of alternating ribs  56  and grooves  58  defined therein. The presence of the alternating ribs and grooves  56 ,  58  minimize dimensional distortion of the bottom portion  16  during the hot fill process and direct deflection as a result of vacuum uptake to portions of the container  10  that are designed to accommodate such uptake, namely the vacuum panel area  20 . 
     Bottom portion  16  further includes a standing ring  50  that in the preferred embodiment extends continuously about an outer periphery of the bottom portion  16  as viewed in bottom plan. The substantially flat portion  52  is preferably positioned within the standing ring  50  and is substantially centered with respect to the standing ring  50 . The substantially flat portion  52  moreover preferably occupies at least 75% of the space that is defined within the standing ring  50 . A transitional surface  54  is preferably defined between the substantially flat portion  52  and the standing ring  50 . The transitional surface  54  is also preferably shaped so as to be substantially symmetrical about the longitudinal axis  25  of the container  10 . 
     As  FIG. 11  shows, the alternating parallel ribs and grooves  56 ,  58  intersect the transitional surface  54  to form a complex shape that stiffens the bottom portion against deformation. The complex shape is particularly effective in stiffening the bottom portion when the bottom portion  16  is fabricated from polypropylene, as a result of the characteristic material properties of polypropylene. 
       FIG. 16  is a table comparison showing the improved performance of the bottom portion  16  of the container  10  that is constructed according to the preferred embodiment of the invention relative to a similar predecessor container that does not have the alternating parallel ribs and grooves  56 ,  58 . The table on the left in  FIG. 16  depicts the base deflection at various points on the container bottom on the predecessor container. The table on the right in  FIG. 16  depicts the base deflection at analogous points in a container  10  that is constructed according to the preferred embodiment of the invention. The diminution in deflection and resulting enhanced dimensional stability of the bottom portion and a container that is constructed according to a preferred embodiment of the invention is evident from the data that is provided in  FIG. 16 . 
     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.