Abstract:
Packaging for a can containing ground roasted coffee packed under atmospheric pressure and having a flexible peel-off lid which is vented to allow the escape of a buildup of carbon dioxide gases. A spacing structure prevents the vent valve in the lid from being closed by contact with the plastic overcap. The spacing structure may include bosses on the overcap which engage the vent valve or a pocket in the overcap which allows the flexible lid to reach a maximum height without engaging the overcap. A permanently opened passageway may be provided between the plastic overcap and the rim of the can to further facilitate the escape of carbon dioxide.

Description:
FIELD OF THE INVENTION 
     This invention relates to a canned product which generates a gaseous pressure buildup, and to an improved arrangement for venting such gases. 
     BACKGROUND OF THE INVENTION 
     Historically, ground roast coffee packaged in a can has been vacuum packed. Recently, it has been found desirable to freshly package roast ground coffee in cans or other rigid or semi-rigid gas impervious packages under atmospheric pressure as contrasted to the prior vacuum packaged cans. Additionally, it has also been found desirable to close off the top of the can with a flexible peel-off easy opening seal or lid, whether the coffee was packed under a vacuum or atmospheric pressure. Examples of such peel-off easy opening lids are shown in the Bolton et al U.S. Pat. No. 5,688,544. 
     Packaged ground roast coffee gives off carbon dioxide which, in a sealed confined space will generate a pressure buildup within the container. In the case of vacuum packed ground roast coffee, this generation of carbon dioxide causes no problem because the pressure buildup simply tended to reduce the negative pressure within the sealed container. However, if the product is freshly packaged initially at atmospheric pressure without extensive degassing, then generated carbon dioxide will cause a pressure buildup in the can above atmospheric pressure. In atmospheric pressure packed ground roasted coffee cans now on the market, this pressure buildup caused by the generated carbon dioxide is dealt with by simply placing a vent valve in the top of the can. If the can is of a type having a flexible peel-off seal, the vent valve will be built directly into the flexible peel-off lid. 
     It is also highly desirable, if not a commercial necessity, to include with any coffee can a plastic overcap which is intended primarily to protect the coffee product within the package after the main airtight seal has been opened. 
     A problem has developed, however, in the case of a ground roast coffee can having a vented peel-off lid and a plastic overcap. It has been found that as the gas pressure builds up within the can it tends to dome the flexible lid upwardly and eventually against the overcap. This creates several problems. First, the constant extension of the flexible lid in its domed condition deforms the flexible lid, causing a wrinkled appearance which is unacceptable to the consumer. Additionally, the materials used to seal the vent valve to the lid, including silicon-based oils, would tend to be expelled from the valve opening and onto the surface of the overcap. This causes a visual blemish which is also unacceptable to the consumer. Additionally, if the valve is sufficiently blocked, the gas within the can can cause the can itself to bulge outwardly, which again is unacceptable to the consumer. 
     While a primary problem has been blockage of the vent valve in the flexible easy-off lid, an additional problem arises in that gases which do escape through the lid may not be able to escape from the space between the lid and the overcap. It is true that the overcap is simply snapped over the chime of the can in a non-airtight manner. However, the surfaces of the overcap which engage the chime of the can, generally along the top and outer periphery of the chime, while not forming a hermetic seal, clearly form a closure which resists escape of any generated gases which might exit from the vent valve into the space between the lid of the can and the overcap. 
     Thus, a need exists for an improved arrangement for venting gases created within a can wherein the product is packed under atmospheric pressure and is of the type which generates gases sufficiently to cause a pressure buildup, especially when such a can is used in combination with an overcap. 
     BRIEF SUMMARY OF THE INVENTION 
     It is a purpose of the present invention to provide a new and improved arrangement for venting gases which build up in a package of the type wherein the product is packaged under atmospheric pressure in a can having a flexible lid with a vent valve and an overcap. More specifically, it is the purpose of the present invention to provide such an improvement for the fresh packaging of ground roast coffee in a can under atmospheric pressure. The term “can” is intended to encompass various types of containers and packages, including the usual cylindrical metallic can as well as rectangular cans, thin metallic cans of any shape and non-metallic cans. 
     In accordance with the present invention, an arrangement is provided for preventing the vent valve to be closed off by contact with the overcap. This arrangement comprises a spacing structure preferably formed in or on the bottom of the overcap, which prevents the vent valve in the lid from being closed by contact with the plastic overcap. In one preferred embodiment, this is achieved by providing bosses on the lower, internal surface of the overcap which will engage the flexible lid as it moves upwardly so as to limit such upward movement to such a height that the vent valve remains unblocked and the vented gases are permitted to flow therethrough. Preferably the bosses engage the vent valve in such a way as to block its upward movement while not occluding the vent valve opening. The bosses can take many different shapes such as thin ribs, rectangular cross sections and the like. 
     In another preferred embodiment, the spacing structure may take the form of a pocket formed in the bottom of the overcap and of such a depth that it allows the flexible lid to reach its maximum height caused by the gas buildup without the flexible lid or the vent valve engaging the overcap. 
     Additionally, the present invention may include a permanently open passageway at the interface between the overcap and the chime of the coffee can which will allow the escape of any built-up gases which have passed through the vent valve into the space between the flexible lid and the overcap. 
     In a preferred embodiment, this permanently open passageway between the overcap and the chime of the can can be provided by providing some raised bosses on the inside surface of the plastic overcap precisely where it engages the chime of the can. A series of such bosses, arranged side-by-side, would thereby provide a permanently open passageway between the bosses. 
     Thus, it is an object of the present invention to provide a new and improved arrangement for venting built-up gases in a can containing a product which generates gases and which can includes a flexible lid and an overcap. 
     It is another object of the present invention to provide a new and improved arrangement for venting gases from a can of the type described which includes a structure for preventing blockage of a vent valve in the flexible lid. 
     It is still another object of the present invention to provide an improved venting arrangement in a package of the type described which includes a structure for forming a permanently open passageway between the interface of the overcap and the chime of the coffee can. 
     These and other objects of the present invention will become apparent from the detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the present invention are illustrated in the accompanying drawings, wherein: 
         FIG. 1  is a cross sectional view through a prior art package illustrating the problem solved by the present invention; 
         FIG. 2  is a plan view of the vent valve on the flexible lid of  FIG. 1 ; 
         FIG. 3  is a greatly enlarged cross sectional view of a vent valve of  FIGS. 1 and 2 , taken along line  3 — 3  of  FIG. 2 ; 
         FIG. 4  is a cross sectional view through a package, similar to  FIG. 1 , but showing the features of the present invention; 
         FIG. 5  is a top plan view of the overcap of  FIG. 4 ; 
         FIG. 6  is a partial cross sectional view taken along line  6 — 6  of  FIG. 5 ; 
         FIG. 7  is a partial cross sectional view taken along line  7 — 7  of  FIG. 5 ; 
         FIG. 8  is a partial plan view of an overcap similar to  FIG. 5  but showing a modification of the present invention; 
         FIG. 9  is a cross sectional view through a package, similar to  FIG. 4 , but showing a modification of the present invention; 
         FIG. 10  is a partial plan view of the overcap of  FIG. 9 ; 
         FIG. 11  is a partial cross sectional view taken along line  11 — 11  of  FIG. 5 ; and 
         FIG. 12  is an enlarged view of the upper right-hand portion of  FIG. 4 , more clearly illustrating certain features of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, like elements are represented by like numerals throughout the several views. 
       FIG. 1  illustrates a conventional can  10  which packages a product  11 , for example ground roast coffee, under atmospheric pressure. The normal condition of the can is shown in solid lines. The top of the can is sealed by a flexible peel-off lid  12  formed of a flexible foil material, which lid is hermetically sealed around its periphery to a ledge  14  which is integral with the can  10 . In a manner known per se, the easy peel-off lid  12  has a pull tab  15 . When a product such as ground roasted coffee is packaged at atmospheric conditions, the carbon dioxide which is naturally given off by the product will cause a gaseous buildup within the interior of the can  10 . It is therefore necessary to provide a vent in the form of a vent valve  16  which will permit the built-up carbon dioxide to escape to the space above the flexible lid  12 . 
     A conventional can includes a chime  13  with inner edge  13   a  and a plastic overcap  20 . The overcap engages the chime at contact lines  21  and  22 . While these contact lines are not intended to provide a hermetic seal, they do to some extent restrict the flow of gas. The primary purpose of the overcap is to provide some protection for the product after the lid  12  has been removed. The overcap  20  also includes a lower part  23  which hangs below the chime and is not in contact with it. 
     The can  10  may be of any suitable material such as metal, plastic, composite materials, cardboard or other suitable materials. Between the time that a can such as that shown in  FIG. 1  is initially sealed, until the time that the consumer removes the lid  12 , carbon dioxide is being generated within the hermetically sealed interior of the can. Initially, as the carbon dioxide tries to escape through the vent valve  16 , the resistance offered by the vent valve  16  would be greater than the resistance offered to upward bending of the flexible lid  12 . Eventually, the condition is reached as shown in dotted lines in  FIG. 1  whereat the flexible lid  12  has been moved up to a domed position  12 ′ and the vent valve  16  has been moved up against the bottom of the overcap  20  as shown at  16 ′. At this point, the downward force of the overcap would tend to close off the vent valve  16 . This presents two problems. First, the lid  12  will remain in the domed position  12 ′ and thus become deformed, causing a wrinkled appearance which is not acceptable to the consumer. Second, if the vent valve  16  includes a silicone-based oil, such oil will be expelled from the valve and onto the overcap  20 . This causes a stain which tends to spread, causing a visual blemish. Additionally, in the case of rectangular cans, thin metallic cans of any shape, and non-metallic cans, a further buildup could cause the sides of the can  10  to bulge outwardly, as represented by dotted lines  10 ′. Such a bulged out can is also unacceptable to the consumer. 
     The vent valve is a commercial product made by Plitek, LLC. Referring to  FIG. 2 , the vent valve is divided into two outer portions  50  which are completely adhered to the top of lid  12  and a central portion  51  which includes a channel therein for the flow of the built-up gases out both ends of the channel, as shown by the arrows in  FIG. 2 . 
     The valve  16  is shown in greater detail in  FIG. 3 . The flexible lid  12  would preferably have openings formed therein in the form of slits  52  of a type as shown in  FIG. 14  of the Bolton U.S. Pat. No. 5,688,544. The width of the slits is highly exaggerated in greatly enlarged  FIG. 3 . In practice, there could be approximately seven small slits, all located in the central portion of the vent valve  16 .  FIG. 2  illustrates a plurality of slit openings in the lid  12  within a central area designated at  60 . Referring to  FIG. 3 , the vent valve  16  includes an upper membrane  53  of metallic polyethylene terephthalate (PET). Below the membrane  53  is a polyethylene terephthalate valve flap  57  which is adhered by synthetic rubber adhesive  54  to a natural PET base  56  which is in turn adhered to the flexible lid  12  by a pressure sensitive adhesive  56 . The inner space between the valve flap  57  and the flexible lid  12  just above the slits  52  is filled with a silicone-based oil with graphite suspension. In practice, gas escaping through the flexible lid  12  will flow through an opening in the valve flap  57  and then outwardly through the ends of central portion  51  between the valve flap  57  and the membrane  53 . The portions  50  and  51  are indicated by vertical dotted lines in  FIG. 3 . 
     Solutions to the problem described above are illustrated in  FIGS. 4–12 . 
     Referring to  FIGS. 4–7 , there is provided an overcap  30 . A vent valve  16  of the type described in  FIGS. 2 and 3  is superimposed in dotted lines on  FIG. 5 . Formed on the underside of the overcap  30  (and referring also to  FIGS. 6 and 7 , there are provided a plurality of thin rib bosses  31 ,  32  and  33 . Referring to  FIGS. 4 and 5 , a highly domed position of the lid  12 , the vent valve  16  will engage the thin rib bosses  31 ,  32  and  33 , thus keeping the vent valve  16  spaced beneath the actual undersurface of the overcap  30 . By providing three bosses  31 ,  32  and  33 , and by placing them at 120° from each other around the center of the overcap, it is assured that at any given rotational position, while one of the thin ribs might well engage and prevent gas from flowing through one end of the central channel portion  51 , the other end thereof will always be unobstructed for the flow of the escaping built-up gases. 
     The rib bosses  31 – 33  are all identical, and one of them is shown in detail in  FIGS. 6 and 7 . In a preferred embodiment, each rib boss would have a thickness of approximately 0.01 inches, a height of 0.04 inches and a width at its bottom of approximately 0.01 inches. 
       FIG. 8  illustrates a modification of the present invention. In this case, there is provided an overcap  40  which differs from the overcap  30  in that the thin rib bosses  31 ,  32  and  33  have been replaced by square cross section bosses as shown at  41 ,  42  and  43  in  FIG. 8 . These could for example have a side dimension of 0.06 inches and a depth, the same as in  FIGS. 4–7 , of approximately 0.04 inches. The bosses may also have other polygonal or round shapes. Referring to  FIG. 8 , it is noted that the three bosses  41 ,  42  and  43  are arranged in a triangular pattern, equiangularly about the axis of the overcap  40 . Here, the vent valve  16  is turned relative to its orientation in  FIGS. 4 and 5 . However, owing to the arrangement of the bosses  41 ,  42  and  43 , even though one of them, in this case  43 , engages the central portion  51 , the other two bosses  41  and  42  are so situated as to permit gas to flow out through the other end of central portion  51 . 
     In the package of  FIG. 4 , the flexible lid  12 , upon original sealing of the can, would be in the downwardly curved position as shown in solid lines in  FIG. 1 . However,  FIG. 4  is intended to illustrate in solid lines only the position when the carbon dioxide has caused sufficient upward movement of the flexible lid  12  to the height whereat the vent valve  16  has engaged the bosses  31 ,  32  and  33 . 
       FIGS. 9 and 10  illustrate another embodiment of the present invention. In this embodiment, an overcap  45  includes a pocket  46  which is sufficiently deep that the vent valve  16 , even in its uppermost domed position, will never engage the bottom of pocket  46  and hence will not engage the bottom of overcap  45 . The location and depth of pocket  46  must be selected so that in the uppermost position of the lid  12  and valve  16 , there is an open passageway through the vent valve  16 , below the edges of the pocket  46  and out toward the periphery of the can. The pocket would preferably have a height of between ⅛ and ¼ inch. 
     As noted above, the contact lines  21  and  22  between the chime of the can and the interior of the overcap  30 ,  40 ,  45 , while not forming a hermetic seal, do offer some resistance to the flow of gases. Referring to  FIGS. 11 and 12 , with the vent valve  16  unblocked (by the use of bosses  31 – 33  or  41 – 43 , or pocket  46 ), permitting free flow of the carbon dioxide out of the can and into the space between the flexible lid  12  and the overcap  30 ,  40 ,  45 , it is possible that the gases can build up to a pressure sufficient to pass beyond contact lines  21  and  22 . However, in order to facilitate the flow of gases out of the space between the overcap  30 ,  40 ,  45  and the lid  12 , the present invention further includes providing a permanently opened passageway from this inner space to the surrounding exterior. For this purpose, raised elongated bosses  35  and  36  are provided on the top and side of the interior of the overcap  30 ,  40 ,  45  where the overcap engages the chime  13  at contact lines  21  and  22 . Gases entering this inner space between lid  12  and overcap  30 ,  40 ,  45  now have a permanently opened passageway for flowing out of this space. This flow from the vent valve  16  up and around the chime  13  is shown by arrows at the upper right hand portion of  FIG. 2  and by arrows A in  FIG. 7 . 
     Although the invention has been described in considerable detail, it will be apparent that the invention is capable of numerous modifications and variations, apparent to those skilled in the art, without departing from the spirit and scope of the invention.