Heretofore, containers or "cans" for packaging flowable or pourable materials including liquids, particularly beverages such as fruit juice and other food-stuffs, have been generally formed of glass, tinplate, aluminum and the like. Although these materials are satisfactory from the standpoint of airtighness and strength, difficulty is often encountered in disposing of these materials after use, in a manner consistent with environmental considerations, and a long-felt need has therefore existed for a container which can be so readily disposed of. From the standpoint of economy of resources, it is also desirable that containers be made of inexpensive substitutes for increasingly expensive conventional materials.
In addition, the laws in many jurisdictions require that, in the processing of certain foodstuffs such as fruit or fruit juice, the product be heated or pasteurized at or above a certain temperature before being put in containers and sealed. However, some foodstuffs, for example, beverages, when processed in this manner will often contract upon cooling in the container, thereby creating negative pressure, i.e., a pressure below atmospheric. If such containers are formed of materials having little rigidity such as thin aluminum, synthetic resins or plastics, the negative pressure must be relieved without breaking the seal in order to avoid the buildup of unwanted stress on the container and consequent strain leading to unsightly deformation of the container wall, structural damage or even failure of the unit. Alternatively, if the container is made of laminated paper, kraft paper, cup paper or other like sheet material, it may not only be deformed but also, due to the pressure differential between the interior and the exterior of the container, may rupture at the seal between the lid and side wall, thereby exposing the contents to infection by infiltration from without, e.g., by bacteria, mal-odorants and the like, with resulting curtailment of shelf storage life. For this reason, it has been customary to use materials of such lower rigidity only for containers intended, e.g., for non-pasteurized or carbonated beverages and the like which provide a neutral or positive pressure within the container.
In the past, tinplate has been the material of choice in making blanks for "tin cans" designed to withstand the aforementioned negative pressure due to its greater rigidity, and for airtightness. However, tinplate is relatively expensive compared to cup paper and the newer synthetic resins and the like and also requires greater effort in its disposal after use. Furthermore, even in the case of tinplate, some deformation of the can or container as a result of negative pressure cannot be avoided. In the past, ways of coping with this problem have included the means shown in FIG. 1 of the drawings. In particular, end-closure 2 of can body 1 is not flattened but rather, is provided with, say, two concentric convex circular ribs 3 and 4 to provide flexibility and permit the closure to deform in response to the internal negative pressure and decrease the latter, thereby preventing container wall 5 from being dented. The small degree of deformation permitted in closure cover 2 limits reduction in the negative pressure but is enough in the case of containers made of conventional tinplate. However, in the case of containers or cans made of thin aluminum, plastics, cellulose-based sheet material and the like, this approach has not proven satisfactory and does not contribute to a solution of the problem. Therefore, containers designed for packaging materials which normally tend to develop substantial internal negative pressures have not heretofore been made successfully of these materials. Other previous attempts at solving the foregoing problems, as exemplified in U.S. Pat. Nos. 1,963,795; 1,987,817; 2,012,213; 2,027,430; 2,115,340; 2,623,681; 2,982,457; 3,089,630; 3,105,765; 3,160,302; 3,247,869; 3,400,853; 3,457,130; 3,687,351; and 3,716,435, have likewise not proven adequate for their solution.
Accordingly, it is an object of the present invention to provide a tubular member or element which defines the wall of a fully airtight and easily disposable container for sealingly packaging flowable materials including beverages and other foodstuffs for long-term storage.
Another object is to provide an improved tubular container wall member or element which effectively protects the contents of the container from impregnation by offensive odors and infectious organisms from without, and which is made of relatively inexpensive and easily disposable materials.
Another object is to provide an improved tubular container and a process for hermetically sealing therein a flowable material such as a beverage or other foodstuff, e.g., fruit juice, which are adapted to respond to and relieve internal negative or sub-atmospheric pressure without breaking the seal.
Another object is to provide a container cover or closure member adapted to respond to and relieve internal negative pressure created, for example, by thermal contraction of the contents of the container, without breaking the seal.
Another object is to provide a container cover or closure member designed so that internal negative pressure created, for example, by thermal contraction within the container, causes the closure cover to become depressed inwardly to an extent not exceeding the degree of thermal contraction, thereby substantially relieving such negative pressure.
Yet another object is to provide fully airtight and easily disposable liquid containers made of materials such as thin aluminum, plastic or synthetic resins, laminated paper, kraft paper, cup paper and the like, which containers are defined by a tubular wall member and by two cover or end-closure members at least one of which end-closure members is adapted to relieve negative pressure generated within the container.
These and other objects of the invention as well as a fuller understanding of the advantages thereof can be had by reference to the following description, drawings and claims.