Patent Publication Number: US-2003221987-A1

Title: Container with stackable base

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] This invention relates to a container having a stackable base and a complementary closure. More particularly, the invention is a base for a heat processable plastic container having a stacking ring to engage a complementary protrusion on a closure of a second container.  
       [0003] 2. Description of the Related Art  
       [0004] Known containers include bottles, jars, tubs and pails. Closures for such containers include screw caps and press-fit lids, and may be one structural piece or made of a plurality of structural component pieces, exclusive of sealing rings and/or liners. Such closures may include a raised peripheral ring around the top to provide improved strength. Ribbed closures are known and have a raised peripheral ring with vertical striations on the skirt to facilitate gripping by a user. Ribbed closures may be made as one piece structures or structures having a plurality of pieces. Closures may include protective liners and sealing means including but not limited to gaskets and liners.  
       [0005] One piece closure structures include screw caps and press-fit lids, and may be employed to close bottles, jars, tubs, and pails filled with foodstuffs and other consumer products. Two piece closure structures include screw caps and lids, and have an outer ring and an inner portion such as a disc. The outer ring may be threaded and generally has an upper flange in which the inner portion is seated. Examples of two piece closure structures include the well-known canning jar lid and vacuum sealable lids seated in ribbed rings. Complex closure structures include caps and lids and may additionally include valves and measuring means. An example of a complex closure is a laundry liquid container provided with a screw cap fitted with a press valve.  
       [0006] Known containers can be stacked but stability of the stacked containers is often inadequate because resistance to being tilted is poor.  
       [0007] Accordingly, it is an object of the present invention to provide a container, which can be stacked with similar or dissimilar containers to provide a stable stack having greater resistance to being tilted.  
       [0008] It is another object of the present invention to provide a method for improving stackability of a plurality of containers.  
       SUMMARY OF THE INVENTION  
       [0009] The above and other objects of the invention can be accomplished by an embodiment of a stackable, heat processable, blow molded, plastic container having a body that has top and bottom ends and a tubular sidewall. The container also has a dome with a finish having an opening. The dome is connected to the top end of the body and the finish is adapted to engage a first closure. The container has a base connected to the bottom end of the body. The base is contoured to engage a portion of a protrusion on a second closure.  
       [0010] In another embodiment, a stack of heat processable, blow molded, plastic containers includes a first container having a body with top and bottom ends and a tubular sidewall. The first container has a dome with a finish having an opening. The dome of the first container can be connected to the top end of the body. The first container also has a base connected to the bottom end of the body. The base is contoured to engage a portion of the protrusion of a second closure on the second container. The stack further includes the second container having a body having top and bottom ends and a tubular sidewall. The second container also has a dome connected to the top end of the body with a finish having an opening. The second container has a closure having a protrusion and being adapted to engage a finish of the second container, and a base connected to the bottom end of the body. The base of the first container has a stacking ring contoured to engage a portion of the protrusion of the closure of the second container. To be stackable, the stacking ring of the first container is adapted to engage the protrusion on the closure of the second container.  
       [0011] In yet another embodiment, a stackable, blow molded plastic container has a body, dome and base. One of the body, dome and base has a distortion resistant structural element that is capable of resisting distortion caused by subsequent hot-fill, retort, or pasteurization processes.  
       [0012] Yet another embodiment provides a method for manufacturing a plastic container adapted for use with filling processes which are conducted at elevated temperatures such as hot-fill processing, retort processing, pasteurization, and the like. The method includes the steps of providing a body, dome and base of the container. The base includes a stacking ring that is contoured to engage a closure of a second container. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013]FIG. 1 shows an exemplary embodiment of a stackable, heat processable, blow molded, plastic container according to the present invention;  
     [0014]FIG. 2 is a perspective view of an exemplary embodiment of a base of a plastic container according to the present invention;  
     [0015]FIG. 3 is a detailed view of an exemplary embodiment of a base of a plastic container according to the present invention;  
     [0016]FIG. 4 is a detailed view of an exemplary embodiment of a base of a plastic container according to the present invention;  
     [0017]FIG. 5 illustrates an exemplary embodiment of a stacking arrangement according to the present invention;  
     [0018]FIGS. 6A, 6B,  6 C,  6 D, and  6 E are partial cross-sectional views showing alternative embodiments of container bottoms having bases with the stackable contoured structure of the invention mated with protrusions of a closure of a second container having contour variations in which:  
     [0019] the base shown in FIG. 6A has an indented angled cross-section mated with a protrusion shown as an angled protrusion;  
     [0020] the base shown in FIG. 6B has an indented rectangular cross-section mated with a protrusion shown as a rectilinear protrusion; and  
     [0021] the base shown in FIG. 6C has an indented frustoconical cross-section mated with a protrusion shown as a rectilinear protrusion;  
     [0022] the base shown in FIG. 6D has an indented triangular cross-section mated with a protrusion shown as a triangular protrusion;  
     [0023] the base shown in FIG. 6E has an indented semi-circular cross-section mated with a protrusion shown as a semi-circular protrusion;  
     [0024]FIG. 7 illustrates an exemplary embodiment of a stacking arrangement according to the present invention;  
     [0025]FIG. 8A shows an exemplary embodiment of a closure according to the present invention;  
     [0026]FIG. 8B shows an exemplary embodiment of a closure according to the present invention; and  
     [0027]FIG. 9 shows a perspective view of an exemplary embodiment of a plastic container according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0028] Heat processable, blow molded containers are designed to withstand the rigors of filling processes including without limitation: hot-fill processing, retort processing and pasteurization. The use of plastic, particularly blow molded polyethylene terephthalate (PET), in the manufacture of such containers has become commonplace and presents opportunities for creating unique design characteristics. However, design restrictions imposed to allow for heat-processing simultaneously presents particular challenges for achieving useful modifications. This is true with most of the other common materials used to make such plastic containers, for example polyolefins.  
     [0029] The hot-fill process is the procedure by which containers are filled with a beverage or some other liquid at a high temperature and capped soon thereafter. As the beverage or liquid cools within the container, stresses and strains develop in the container due to changes in the volume of the contents.  
     [0030] In retort processing, a container is filled at ambient temperature and capped, heated to high temperatures, for example, 260° F. at super-baric pressures (i.e., up to 45 psi) and then cooled back to ambient temperatures.  
     [0031] Pasteurization involves filling a container with a liquid or other substance that has an elevated temperature, for example, 140° F., and then raising the temperature to high temperatures, such as, 220° F. to 240° F. and then allowing the container and its contents to cool to ambient temperature.  
     [0032] Heat processable containers are subjected to varying internal pressures and volumetric changes (depending on the heat process used) due to higher processing temperatures, and therefore, expansion of the contained products and associated vapors. Without structural support, heat processing can cause plastic containers to distort in a commercially-unacceptable manner. Improved base construction can prevent the base of a plastic container from undergoing excessive outward deflection, i.e., deflection below the container standing ring.  
     [0033] These improved bases typically include, at least, a standing ring and a central concavity, known as a push-up, to prevent distortion. The presence of a standing ring and a push-up in the heat processable container may reduce the container&#39;s stackability because there is not a large surface area in the base of the container to make contact with another container. Stackability may be further reduced if the container has an upper end or closure or the like that also fails to provide a large surface area to mate with the base of another container. In that situation, the surface areas of the base and the upper portion of another container must align for the containers to stack.  
     [0034] In such an arrangement, although the containers are stackable, they are not likely to be capable of being tilted. To improve the tiltability of such a stack of containers, the base of the container, more particularly, the portion of the standing ring that mates with closure of another container can be contoured so as to straddle a closure of another container.  
     [0035] As used herein, the phrase straddle is intended to include essentially any straddling engagement, i.e., surface area engagement, since an engagement of even about 1% of the protrusion by the base is somewhat effective to improve stackability of such containers. In exemplary embodiments, the engagement is greater than about 50% of the protrusion and can be near 100%.  
     [0036] For example, in embodiments where a first container is a tubular jar and is stacked in mating engagement on a protrusion of round screw cap of a second container, the percent of straddling engagement, i.e., surface area engagement, would be determined as follows. In this example, the base of the tubular jar has the contour of an indented annular ring in a bottom view having inner and outer diameters and having the radial cross-section of a rectangle of 2 mm by 4 mm which is open on one of the 4 mm sides so as to straddle the peripheral rim of the screw cap. In this example, the protrusion of the screw cap has inner and outer diameters which are approximately equivalent to those of the indented annular ring contour of the base, has about a 4 mm difference between its outer and inner diameters, and is raised about 2 mm from a central flat portion of the screw cap. Thus, the percent of straddling engagement, i.e., surface area engagement, of the indented annular ring of such a base on such a protrusion would be approximately 100%, that is, a substantial mating engagement. In other exemplary embodiments, the indented annular ring in the container base and protrusion on the closure may have dimensions of about 2 mm×6 mm. Variations from substantial mating engagement may be due to (a) differences in the radial cross-sectional shapes of the base and the peripheral rim, (b) differences in respective diameters, (c) differences in the completeness with which the base covers the periphery of the protrusion; and (d) varying tolerances during the manufacturing process.  
     [0037] Referring now to the figures, FIG. 1 shows an exemplary embodiment of a stackable, heat processable, blow molded container  10  that can include a base  16  (and complementary closure) for improving the stackability and tiltability of a stack of containers. Container  10  can have a body  11  formed by sidewall  12 . Body  11  can have a width W measured by the width of sidewall  12  at its widest point. Sidewall  12  can be tubular. As referred to herein, tubular means non-tapered and can include cross sections which may be substantially cylindrical, square, or other shapes. For example, as shown in FIG. 1, sidewall  12  is substantially cylindrical. As shown in FIG. 9, sidewall  12  can be substantially square. This and other exemplary embodiments can be shown in further detail in U.S. patent application Ser. No. 10/366,617, which is incorporated herein by reference in its entirety and is owned by the assignee of the present invention.  
     [0038] Sidewall  12  can include a pair of flex panels  73   a  and  73   b  (as shown in FIG. 7) that can be opposite one another in body  11  and each flex panel  73   a  and  73   b  can be planar. Sidewall  12  can also include a plurality of sidewall ribs  74  (as shown in FIG. 7). Sidewall ribs  74  can be horizontal or vertical (not shown). Particular embodiments of body  11  that include flex panels  73   a ,  73   b  and sidewall ribs  74  are shown in U.S. Pat. No. 6,439,413, which is incorporated herein by reference in its entirety and is owned by the assignee of the present invention.  
     [0039] Container  10  can also have a dome  13  that can merge with sidewall  12 . Dome  13  can have a finish  14  that can define an opening  15  for filling and pouring the contents of container  10 . Dome  13  can be a conventional dome, meaning dome  13  narrows sidewall  12  to finish  14 . Finish  14  can be adapted to receive closure  50  (shown in FIG. 5) as discussed in detail below.  
     [0040] Container  10  can also have a base  16  that can be contoured so as to straddle closure  50  of another container as shown in FIGS. 5 and 7. As shown in FIG. 2, base  16  can have standing ring  20  for contact with a horizontal surface (not shown) on which the container can rest. Base  16  can also have bottom wall  26  that defines a central concavity  26   a  known as a push-up. Stacking ring  23  can be interposed between standing ring  20  and bottom wall  26 . Stacking ring  23  can be a continuous ring, but in another exemplary embodiment, stacking ring  23  need not be complete and may have gaps. In yet another embodiment, stacking ring  23  can have an incomplete radial cross-section because stacking ring  23  can adjoin flat portion  28  of labeling lug  29 . As shown in FIG. 3, stacking ring  23  can have a diameter D 2  that extends across stacking ring  23  on center. In an exemplary embodiment, sidewall width W greater than stacking ring diameter D 2 .  
     [0041] Standing ring  20  can have outer portion  21  that can merge base  16  with sidewall  12 . Standing ring  20  can also have inner portion  22  that can merge with outer wall  24  of stacking ring  23 . Stacking ring  23  can include inner wall  25  that can merge with bottom wall  26 . In an exemplary embodiment, at least a portion of outer wall  24  and inner wall  25  can be vertical, i.e., substantially parallel to sidewall  12 . Push-up  26   a  can have a plurality of support ribs  27  extending radically from the central concavity. Support ribs  27  can have a base disposed upwardly into the central concavity and an apex disposed downwardly towards stacking ring  23 .  
     [0042] As shown in FIG. 3, support ribs  27  can have a trapezoidal shape. In an alternative support ribs  27  can have a pyramidal shape. In yet an alternative exemplary embodiment, push-up  26   a  does not include support ribs  27 . This and other exemplary embodiments of base  16  are shown in U.S. patent application Ser. No. 10/366,574, which is incorporated herein by reference in its entirety and is owned by the assignee of the present invention.  
     [0043]FIG. 4 shows a detailed cross-section of stacking ring  23 . In an exemplary embodiment, stacking ring  23  can be angled downward at an angle α from outer wall  25  to inner wall  24 . Angle α can be between 1° and 15° from horizontal. More particularly, angle α can be approximately 7° from horizontal.  
     [0044] As shown in FIG. 5, stacking ring  23  can mate with protrusion  51  of closure  50  to provide the desired stackability and tiltability. Closure  50  can mate with stacking ring  23  by aligning protrusion  51  with stacking ring  23 . In such a mating engagement, the stacking ring  23  of container  10  can straddle the protrusion  51  of closure  50 . Specifically, standing ring  20  can surround peripheral wall  52  of closure  50 . Closure  50  can have a diameter D 3  that is measured across the center of protrusion  51 . In an exemplary embodiment, closure diameter D 3  is approximately equal to stacking ring diameter D 2 .  
     [0045] In an exemplary embodiment, closure  50  can be one contiguous piece (as shown in FIG. 5), such as a press-fit or screw-on lid or the like, and protrusion  51  can form a peripheral ring around closure  50 . In another exemplary embodiment, as shown in FIG. 8B, closure  50  can be a two-part closure. Closure  50  can have inner disc portion  82  and a ring  81 . In this embodiment, protrusion  51  can be formed on ring  81 . In another embodiment, as shown in FIG. 8A, protrusion  51  can be formed on inner disc portion  82 . In either embodiment, ring  81  can have a substantially vertical skirt  84  with internal threads (not shown) to threadedly engage a finish of another container. Skirt  84  can have external vertical striations  83  to aid gripping.  
     [0046]FIGS. 6A, 6B,  6 C,  6 D and  6 E are partial cross-sectional views showing alternative embodiments of container  10  having bases  16  with the stackable contoured structure of the invention mated with protrusions  51  of closure  50  having contour variations. Stacking ring  23  of base  16  shown in FIG. 6A has an intended angled cross-section mated with protrusion  51  shown as an angled protrusion. Stacking ring  23  of base  16  shown in FIG. 6B has an intended rectangular cross-section mated with protrusion  51  shown as a rectangular protrusion. Stacking ring  23  of base  16  shown in FIG. 6C has an indented frustoconical cross-section mated with protrusion  51  shown as a rectilinear protrusion. Stacking ring  23  of base  16  shown in FIG. 6D has an indented triangular cross-section mated with a protrusion  51  shown as a triangular protrusion. Stacking ring  23  of base  16  shown in FIG. 6E has an indented semi-circular cross-section mated with protrusion  51  shown as a semi-circular protrusion. As will be appreciated by persons skilled in the art, the configurations illustrated in FIGS.  6 A- 6 E are non-limiting and other configurations can be used. Further, it will be appreciated that the objects of the invention can be achieved without the stacking ring  23  and protrusion  51  having identical shapes. For example, the rectangular protrusion  51  (FIG. 6B) can mate with an angled stacking ring  23  (FIG. 6A).  
     [0047]FIG. 7 shows an exemplary embodiment of a stack  70  of containers  71 ,  72  according to the present invention. Stack  70  can include top container  71  and bottom container  72 . Top container  71  can include base  16  that is contoured, thus forming a stacking ring as described in FIGS.  2 - 6 , to straddle a protrusion on closure  50  of bottom container  72 , as described in any of FIGS. 5, 6 and  8 . In the mating arrangement shown in FIG. 7, sidewall width W is greater than stacking ring diameter D 2  and stacking ring diameter D 2  is equal to closure diameter D 3 , thus causing the top container to straddle the bottom container. This straddling has the effect of improving stackability and tiltability.  
     EXAMPLE  
     [0048] The significantly improved resistance to tilting of a stack of containers according to the present invention was demonstrated in the following tests conducted on containers, which were bottles fitted with two piece screw caps. The containers were equivalent except that the “control containers” did not have a base according to the present invention defined in their bottoms. The “stackable containers” according to the invention had bases as illustrated in FIGS.  2 - 5  and  6 A.  
     [0049] A two-piece 63 mm ribbed closure was employed which included a plastic ring having a peripheral rim with a raised annular section with a 65.9 mm outer diameter and a 54 mm inner diameter, and a metal disk positioned within and retained by the ring. The raised annular section had a radial cross-sectional shape, which was generally rectangular and extended vertically above the plane of the metal disk by about 2 mm. The width of the longer leg of the rectangle was about 6 mm. Containers according to the invention which were provided with a base had a complementary radial cross-sectional shape and not only engaged and straddled the peripheral rim of the container below it in a stack but featured a mating engagement because of the complimentary shapes, dimensions, and diameters.  
     [0050] A plastic jar weighing 50 grams±1 gram and having an overflow volume of 705 cc±20 cc was modified to have a stackable base according to the invention, i.e., “stackable container”. Unmodified jars provided the “control containers”. Water weighing 686 grams at ambient temperature was filled into both types of containers.  
     [0051] The empty and water-filled containers were stacked 2, 3, or 4 high on a horizontal surface and each stack&#39;s resistance to being tilted was tested by tilting the surface in a controlled manner. Table 1, which follows gives the degree from vertical, tolerated by each stack before the top container fell from the stack. As a practical matter, the falling of one container was generally accompanied by toppling of the entire stack.  
               TABLE 1                          Comparison of Degrees from Vertical Tolerated by the Stack Indicated                             Control Containers:   Stackable Containers:                                 Number/Stack   Empty   Filled   Empty   Filled                                         2   15   20   30   35       3   12   15   25   28       4   9   10   17   22                  
 
     [0052] As can be readily seen from the data of Table 1, a stack of “stackable containers” according to the invention had a significantly a greater resistance to toppling when tilted than a stack of “control containers” whether empty of filled with water. Such improved stackability is clearly advantageous to retailers in general and grocers in particular.  
     [0053] It is understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of the present invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description set forth above but rather that the claims be construed as encompassing all of the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those skilled in the art to which the invention pertains.