Patent Publication Number: US-7712624-B2

Title: Plastic coffee container with top load support by particulate product

Description:
BACKGROUND OF THE INVENTION 
     Containers for particulate products, especially (roast or ground) coffee particulate products, have many unique requirements which need not be considered for other containers. For example, coffee particulates give off gases while being stored, and are deleteriously affected by air. Thus, coffee particulate containers must prevent the ingress of air and hence be air-tight. In addition, such containers must also be suitably robust to withstand a build-up of pressure; or alternatively, the container must vent the built up gases before the pressure thereof damages (miss-shapes or breaks) the container or be subject to an initial vacuum so that any build up of pressure is not excessive. 
     While particulate coffee containers were previously generally made of metal formed into a cylinder with a top and a bottom (which was thus easily made robust and air-tight), new cylindrical and other shaped rigid plastic containers, particularly with layered walls, have now been found to be suitable for containing particulate coffee. However, while such plastic containers have sufficient size to store a desired volume of particulate coffee, typically in the range of 2-4 pounds and have diameters and heights of about 5-7 inches, such containers have been expensive to make. This expense includes the material needed to make the container walls sufficiently strong so that such containers can support a sizable top load, such as from other containers stored thereabove in a pallet during shipping. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with the present invention, a rigid container for a particulate product with enhanced top load support is provided. The rigid container includes a main interior volume formed by a base, a surrounding wall member upstanding from the base, and a top. A particulate product, such as coffee, is provided in the interior volume. This particulate product is flowable and is provided in sufficient quantity to fill the interior volume up to where a predetermined minimum headspace is provided. The predetermined minimum headspace is that headspace which produces a top load ratio of at least 3:1; where the top load ratio is defined as a ratio of the top load force sufficient to cause a 0.30″ deflection in the plastic container when filled to the predetermined minimum headspace over the top load force sufficient to cause a 0.30″ deflection in the plastic container when empty. 
     In a preferred embodiment, the rigid container further includes an enlarged top opening and a flexible closure attached to the top and spanning the top opening. Then, the predetermined minimum headspace is also sufficient so that when a pressure of the main interior volume is about 3 psi less than ambient, which pressure causes the flexible closure to flex inward, more than about 20% of the flexible closure contacts a top portion of the particulate product. 
     In the preferred embodiment, the surrounding wall member has a wall thickness which is greater adjacent the top than adjacent the base. This is preferably accomplished in one embodiment by having the wall thickness of the surrounding wall member change gradually from adjacent the top to adjacent the base. In another embodiment, the thickness of the top half is twice that of the bottom half. 
     In various embodiments, the surrounding wall member is generally curved in cross section (such as being circular or oval) or rectangular (such as square); and is advantageously made of plastic. Preferably, the particulate product is compacted coffee, and the main interior volume holds at least one liter of the coffee therein and is able to vent excess pressure therein to atmosphere through a suitable one-way valve which is most preferably provided in the flexible closure. 
     Also in accordance with the present invention, a method for reinforcing a rigid container for a particulate product against top load forces is provided. This method includes the step of forming a rigid container with a container main interior volume formed by a base, a surrounding wall member which is upstanding from the base, and a top which connects with the surrounding wall member and which includes an opening therein. Next, the main interior volume is filled with a particulate product so that at least a predetermined minimum headspace is provided. This predetermined minimum headspace is that which produces a top load ratio of at least 3:1, as described above. 
     Preferably, after the filling step, a flexible closure is attached to the top and spans the top opening. In addition, the predetermined minimum headspace is also sufficient so that about 20% of the flexible closure contacts a top portion of the particulate product when a pressure of the main interior volume is 3 psi less than ambient and this pressure causes the flexible closure to flex inward. 
     Preferably, the filling step includes the step of vibrating the particulate product, which is preferably coffee. In addition, the flexible closure attached to and spanning the top opening includes a suitable one-way valve provided therein to vent excess pressure in the main interior volume to atmosphere. The rigid container is also preferably made of plastic, with the main interior volume holding at least one liter of the coffee. The wall thickness of the surrounding wall member also preferably reduces in thickness from top to bottom, most preferably gradually or by having the top portion twice as thick as the bottom portion. 
     The surrounding wall member is generally curved in cross section (such as circular or oval) or rectangular (such as square). 
     It is an advantage of the present invention that a rigid container containing a particulate product includes an increased top load strength provided by a predetermined minimum headspace so that the container walls do not need to provide a majority of the top load support. 
     It is also an advantage of the present invention that the container walls can be of reduced thickness, resulting in a savings of raw materials for the container. 
     It is a further advantage of the present invention that a one-way valve for releasing off gases produced by coffee is provided. 
     Other features and advantages of the present invention are stated in or apparent from detailed descriptions of presently preferred embodiments of the invention as discussed in greater detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a cross sectional elevation view of a coffee container according to a first embodiment of the present invention. 
         FIG. 2  is an enlarged view of the portion of the container of  FIG. 1  identified with the broken out section line numbered  2 . 
         FIG. 3  is a graphical representation of the effect of the present invention showing load versus compression for three containers. 
         FIG. 4  is a cross sectional view of an alternative embodiment of a portion of a surrounding side wall member according to the invention. 
         FIG. 5  is a cross sectional view of another alternative embodiment of a portion of a surrounding side wall member according to the invention. 
         FIG. 6  is a schematic perspective top view of a portion of a flexible closure including a one-way valve in accordance with the present invention. 
         FIG. 7  is a schematic bottom view of a container according to the present invention. 
         FIG. 8  is a schematic bottom view of another container according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference now to the drawings in which like numerals represent like elements in the views, a rigid particulate coffee container  10  according to a first embodiment of the present invention is shown in  FIG. 1 . It will be appreciated that container  10  hereafter described is rectangular or actually square in cross section, i.e., as having a basic square footprint of about 6.2″×6.2″ and a height of about 6.5″. However, container  10  could also be of different cross sectional shapes as discussed hereinafter and as disclosed in Ser. Nos. 11/353,091, 11/353,092, and 11/353,093 filed Feb. 14, 2006 by GRUSKIN et al. and Ser. No. 11/498,141 by Scarola (all assigned to the same assignee) which are hereby incorporated by reference; and container  10  is also preferably similar to any one of the containers described those serial numbers. 
     Like the containers described in the above serial numbers, container  10  is designed for containing fresh ground or roast (particulate) coffee  12  or a similar flowable particulate product such as a powdered beverage mix, the particles of which are relatively non-compressible. Similarly, container  10  is also made of a suitable blow-molded plastic, such as high density polyethylene (HDPE), preferably by an extrusion blow molding rotary process or other like process. One preferred layered material of a plastic coffee container includes an EVOH layer and is disclosed in Ser. No. 11/498,140 filed Aug. 3, 2006 by Scarola (and assigned to the same assignee) which is hereby also incorporated by reference. 
     In accordance with the present invention, container  10  includes a generally square base  14  with an integrally formed surrounding square wall member  16  extending upwardly therefrom. In order to allow easy withdrawal of coffee  12  from a main interior volume  18  of container  10  defined by base  14 , surrounding wall member  16  and a top  20 , it will be appreciated that container  10  has a large opening  22  in top  20 . Opening  22  is preferably round and centered in surrounding wall member  16 , and opening  22  has a diameter only slightly less than the diameter of surrounding wall member  16 . Preferably, top opening  22  is at least five inches in diameter; but no matter the shape, opening  22  has a size sufficient for a five inch cylinder to fit therethrough. Such a large opening is considered desirable in order to enable a user to easily remove coffee  12  from container  10 , once the user has removed a flexible closure  24  (as discussed below) typically provided thereon. As known in the art, surrounding wall member  16  can be provided with slightly indented label receiving portions (not shown) to receive a label or labels or the like. 
     Closing top opening  22  is a flexible closure  24 , typically in the form of a thin foil, film plastic or other suitable membrane as well known in the art, adhered to the perimeter of top  20  and removed by the user after purchase. A one-way valve is provided in flexible closure  24 , or alternately if desired in surrounding wall member  16 , to permit controlled release of the build-up in pressure which occurs due to the off-gases generated by coffee  12  as also well known in the art. Such a one-way valve may not be necessary for container  10  if container  10  is packed under a vacuum. Finally, closing top  20  is a flexible plastic cap  26  which is releasably held on the perimeter of top  20  as well known in the art. Cap  26  is used to close top opening  22  after each use, once the consumer has permanently removed flexible closure  24  in order to access coffee  12  therein for the first time. 
     As noted above, one problem with prior art rigid containers is that they can be expensive to make in view of the strong structural top load support which container  10  (and in particular surrounding wall member  16 ) must provide. In particular, after initial filling and during shipping, container  10  can have for example nine or more similar containers  10  supported thereabove in a pallet or the like, creating a substantial top load on the bottommost container  10 . Such a large top load is accommodated by container  10  in accordance with the present invention by having coffee  12  filled to a predetermined minimum headspace  28 , as shown best in  FIG. 2 . 
     The mechanism by which container  10  with a predetermined minimum headspace  28  can support a large top load in accordance with the present invention is not well understood, and must determined by the individual container type which is to be used and the properties of that type of container. However, the predetermined minimum headspace  28  needed is readily determinable by simple trial and error in view of the following. It is also believed that container  10  of the present invention must have some minimum volume in order for the particular product therein to function to provide a sufficient top load, which volume is on the order of one liter or more. 
     When a top load is applied to a rigid container, such as plastic container  10 , container  10  experiences some minor compression due to the plastic material from which it is made and its various other properties. This minor compression is acceptable as it occurs without harm or adverse appearance, and is typically designed into any such container  10  and is on the order of 0.3″. Prior art plastic containers have withstood such large top loads at such a minor compression of 0.3″ by making the surrounding wall member sufficient thick. However, the present invention instead relies on the surprising resistance to compaction that coffee  12  experiences when it is filled into container  10  up to the predetermined minimum headspace  28 . In particular, when container  10  experiences a large top load and container  10  is compressed downwards by some amount (e.g., 0.3″), due to the nature of coffee  12 , the particulates thereof are not easily compressed. Thus, a significant resistance force is generated by coffee  12  before the acceptable 0.3″ compression is reached. 
     In experiments conducted to assess the resistance force offered by coffee  12  (and hence alternatively usable to predetermine what minimum headspace is required in a container), it was found that the resistive force is quite substantial when headspace  28  is sufficiently short. In particular, as shown in  FIG. 3 , a 142 gram weight (standard, for this experiment and typical in the art) container experienced substantial compression when a force advancing at 0.25″/minute was evenly applied (via a piece of wood) across the top. This empty container did not offer much resistance to deformation until destructive deformation occurred (where the line stops). For comparison, with this standard container then filled with what would be a normal amount of coffee (1107 grams) leaving a typical for the art headspace of 1.25″ below the top (where a flexible closure would be), some slight additional resistance to compression was experienced and further compression was tolerated without destructive deformation. However, as shown, when this standard container was filled with coffee to a predetermined minimum headspace below the top, substantial resistance to compression was experienced up to the limit of the testing machine and without destructive deformation of the container. 
     As shown in  FIG. 3 , container  10  with no contents experiences a load of about 191 lbf sufficient for container  10  to be compressed 0.30″, while container  10  with coffee sufficient to fill the container after vibration of coffee  12  up to a predetermined minimum headspace  28  (about ⅜ inch) experienced a load of about 931 lbf sufficient for container  10  to be compressed 0.30″. This graph thus shows a 4.87:1 top load ratio—where the top load ratio is the ratio of the forces applied to produce a 0.30″ compression for a filled container and for an empty container. Such a high top load ratio is a significant advantage as discussed hereafter. It is thus evident that with the present invention over one half, and in fact preferably most, of the top load on a container is supported by the coffee itself contained therein. Thus, it is a feature of the present invention that the container has a predetermined minimum headspace  28  sufficient for a top load ratio of at least 3:1. 
     Experiments were also performed to access the top load capacities of various prior art containers with various particulate products therein. The experiments were conducted with a 0.30″ compression of the top, when the containers first off the shelf or full and then when empty, where the load was applied to an open top (there was no flexible closure present). The results of these experiments are as follows (with the data on the present invention also presented last for easy comparison). 
                                         PRODUCT   EMPTY LOAD   FULL LOAD   RATIO                                                Folgers 1 lb   121.3   182.57   1.51       Folgers 3 lb   172.16   326.17   1.89       Folgers 4 lb   271.75   380.42   1.40       Hills Bros. Coffee   145.45   345.51   2.38       Kool Aid   61.23   81.63   1.33       Coffee Mate   69.12   129.66   1.88       Beef Bouillon   81.55   89.58   1.10       Antacid   65.82   59.63   0.91       Cat Litter   40.5   39.88   0.98       Pistachio Nuts   56.57   130.85   2.31       Garlic Salt   181.8   472.41   2.60       Invention-Coffee   191   931   4.87                    
Other specifics about these tested containers are:
 
                                                 EMPTY   CONTENTS               PRODUCT   WEIGHT   WEIGHT   SIZE   MATERIAL                                                            Folgers 1 lb Coffee   48   g   326   g   5.25″ H, 4″ D   HDPE       Folgers 3 lb Coffee   115   g   1100   g   6.5″ H, 6.5″ D   HDPE       Folgers 4 lb Coffee   163   g   1470   g   8.5″ H, 6.5″ D   HDPE       Hills Bros. Coffee   195   g   1100   g   6.5″ H, 6″ × 6″ B   multilayer       Kool Aid   39   g   19   oz   5″ H, 3.5″ D   HDPE       Coffee Mate   39.98   g   10.2   oz   6″ H, 2.5″ D   HDPE       Beef Bouillon   25.1   g   3.4   oz   5″ H, 1 13/16″ D       Antacid   22.3   g   180   g   5″ H, 2″ × 1.5″ B   PP       Cat Litter   84   g   7   lb   8.75″ H, 6″ × 6″ B   HDPE       Pistachio Nuts   34   g   6   oz   6″ H, 2.5″ D   PETE       Garlic Salt   31   g   9.5   oz   5″ H, 2″ D   PETE       Invention-Coffee   142   g   1275   g   6.5″ H, 6.2″ × 6.2″ B   multilayer                    
It is thus seen that such prior art plastic containers with their provided headspace do not have a minimum headspace sufficient to provide a top load ratio of 3:1 in accordance with the present invention.
 
     As a result of the ability of coffee  12  to provide substantial resistance to a large top load, it is possible to reduce the wall thickness of surrounding wall member  16  since the container need not be sufficiently rigid by itself to withstand such a (or most of a) large top load. This reduction in wall thickness can effect a substantial cost savings for the container, as the cost of the material is often a significant expense. 
     Thus, in one preferred embodiment as depicted in  FIG. 4 , surrounding wall member  16  has a wall thickness A for a top half of surrounding wall member  16 , and a wall thickness B for the lower half. For example, wall thickness A could be twice that of wall thickness B. A thicker wall thickness is needed at the top rather than the bottom because coffee  12  will provide some additional compressive support to surrounding wall member  16   a , which support by coffee  12  will increase the closer it is to the base. 
     In an alternative embodiment depicted in  FIG. 5 , the wall thickness of surrounding wall member  16   b  varies over the height, from a maximum adjacent the top to a minimum adjacent the base. For example, the thickness could vary from 145 mil to 90 mil. 
     The present invention also includes a method of protecting a plastic container for a particulate product against top load forces. In accordance with this method, plastic container  10  is first formed to provide the main interior volume  18  as desired and the large opening  22 . Then, main interior volume  18  of container  10  is filled with particulate coffee  12  so that a minimum headspace  28  is left; after which typically a flexible closure is attached to top  20 . In this preferred embodiment, the flexible closure is flexible closure  24 , but if a flexible closure or the like is not needed or desired, the flexible closure could be whatever closing member, including cap  26 , is used. Cap  26  can be a snap-on type as depicted, or a screw-on cap if desired. 
     Due to the compacting nature of the particulate coffee  12  used, it is desired to compact coffee  12  during filling of and once inside of main interior volume  18 . This compacting is done to make sure that container  10  has an actual headspace slightly smaller than the predetermined minimum headspace  28 , since coffee  12  is likely to further settle during shipping or the like and hence the actual headspace might be increased to the point where the predetermined desired headspace  28  is not provided and hence coffee  12  is not able to contribute significantly to the top load resistance. The amount of further settling that coffee  12  is likely to experience during shipping is relatively small however, and easily determined by those of ordinary skill, so only a little extra filling of coffee  12  above the level of the predetermined minimum headspace  28  is needed. Such a compacting is preferably achieved by vibration, or even by physical force. 
     In order to protect container  10  against the increase in pressure produced by fresh roast or ground coffee  12 , a one-way valve  29  located on flexible closure  24  as schematically depicted in  FIG. 6  and well-known in the art is used. When one-way valve  29  is used, it will also be appreciated that another problem with plastic containers for coffee having a flexible closure  24  is that flexible closure  24  and the remainder of container  10  can be subject to undesirable inward deformation forces. These undesirable deformation forces may occur when container  10  is shipped over a high altitude, and hence experience a low ambient pressure. When such shipping occurs, one-way valve  29  keeps the pressure between the inside of the container  10  and the outside at a relatively set amount such as (positive) 0.1 psi. Consequently, at the peak or greatest vertical height of shipping (lowest ambient pressure), the inside of the container  10  will be only 0.1 psi greater than the outside or ambient pressure. Then, when the container  10  descends from the peak height, there may be a significant difference between the low pressure in the inside of container  10  and ambient, such as almost 6 psi in an extreme case. Such a large difference in pressure may then be sufficient to undesirably bow flexible closure  24  inward and/or undesirably deform container  10 . 
     However, with the use of the minimum headspace of the present invention as described above, flexible closure  24  and the predetermined minimum headspace are designed so that at a known or determined pressure differential, preferably at about 3 psi, at least about 20% of flexible closure  24 , typically the central portion, contacts the top of coffee  12  in container  10 . When this happens, no further deformation of flexible closure  24  at the contacted locations can occur. And as this touching occurs, it will be appreciated that the rest of the container is supported as well by coffee  12  as described above; and in fact, the contact of flexible closure  24  also serves to push against coffee  12 , further tending to resist the tendency of surrounding wall member  16  and base  14  to be pushed inward by the pressure differential. In this manner, even a relatively high pressure differential does not adversely effect container  10 . Of course, the remainder (peripheral portion) of flexible closure  24  not in contact with coffee  12  does experience the pressure differential, but it is believed that as the central portion is supported by coffee  12 , the remainder of flexible closure  24  is better able to withstand the pressure differential. 
     It will also be appreciated that where container  10  has a surrounding wall member with a reduced thickness adjacent the bottom as disclosed above for surrounding wall members  16   a  or  16   b , a pressure differential such as discussed above will also exert a deforming force on the surrounding side wall member. While the surrounding wall member  16   a  or  16   b  of any empty container would readily collapse at the thinner portion, the use of the predetermined minimum headspace  28  of the present invention also assures that sufficient compacted coffee  12  will also be present at the thinner-lower portions of surrounding sidewall members  16   a  and  16   b  with sufficient force to resist the inwardly directed forces of any such pressure differential. Thus, the thinner thickness of surrounding side wall members  16   a  and  16   b  do not present a problem when such a pressure differential is experienced. 
     Depicted in  FIG. 7  is another embodiment of a plastic particulate coffee container  30  according to the present invention. It will be appreciated that container  30  has a circular base  32  as shown with an identical circular surrounding wall member (not shown) extending upwardly therefrom. Other than an circular footprint, container  30  is thus similar to container  10 ; and container  30  could include the same variations thereof as discussed above. 
     Depicted in  FIG. 8  is another embodiment of a plastic particulate coffee container  40  according to the present invention. It will be appreciated that container  40  has an oval base  42  as shown with an identical surrounding oval wall member (not shown) extending upwardly therefrom. Other than a oval footprint, container  40  is thus similar to container  10  (or  30 ), and could include the same variations thereof as discussed above. In fact, container  10  is well suited to be like any of the containers disclosed in the above identified prior applications which have been incorporated by reference. 
     Although the preferred embodiments of the rigid containers have been depicted being made of a plastic material, it will be appreciated that the concept of the present invention could also be used with rigid containers of other materials such as, for example, aluminum or steel cans, paperboard cartons, corrugated cartons, or composite (paperboard with a plastic liner or the like) tubes or cartons. Thus, rigid container of these materials could all be provided with a predetermined minimum headspace to effect increased top load strength as discussed above. 
     While the present invention has been described with respect to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that variations and modifications can be effected within the scope and spirit of the invention.