Graham Packaging issued US patent for 'Reinforced retortable plastic containers'
February 20, 2014
(Life Science Weekly)
– According to news reporting originating from Alexandria, Virginia, by NewsRx journalists, a patent by the inventor Yourist, Sheldon E. (York, PA), filed on May 10, 2012, was published online on February 11, 2014 (see also Graham Packaging Company, L.P.).
The assignee for this patent, patent number 8646646, is Graham Packaging Company, L.P. (York, PA).
Reporters obtained the following quote from the background information supplied by the inventors: "This invention relates generally to the field of packaging, and more specifically to the field of retortable plastic containers. More specifically, the invention relates to an improved retortable container that is more dimensionally stable during the sterilization process than conventional predecessor containers.
"Certain products require sterilization during the packaging process in order to inhibit the growth of bacteria. Products requiring sterilization include foods such as milk, yogurt and various sauces, as well as certain pharmaceutical products. Thermal processing, sterilization, canning and retorting are all terms referring to the process of taking a food product, already sealed in its container, and heating it to a specific temperature for a specific time. The objective is to kill spoilage organisms and pathogenic bacteria, thus preserving the food and allowing it to be stored unrefrigerated for extended lengths of time.
"There are multiple designs for retorting food containers, including batch systems and continuous systems. In a batch system, containers are placed in crates or baskets, which are then loaded into a vessel into which the heating medium is introduced. This method is the oldest and most traditional and also the most versatile in the range of products and container sizes it can handle. In a continuous retort system, a conveyor is used to continuously transport the containers to be sterilized through a heating chamber that contains the heating medium. There are advantages to each method depending on individual processing operations and, just as important, the type of food being processed.
"Traditionally, products that require heat sterilization have been packaged in glass containers, which are relatively stable at elevated temperatures and pressures. However, in recent years plastic retortable containers have come into use. Plastic containers tend to be less expensive than glass containers and safer in many respects because they will not shatter when dropped. Unfortunately, plastic containers may lack the column strength that is necessary to avoid deformation of the sidewall of the container when a number of containers or palettes of containers are stacked during transportation or in packaging or retail facilities. While it is possible to increase the strength of a plastic container by increasing the thickness of the sidewall, doing so also increases manufacturing costs by increasing the amount of plastic material that is required. Lightweighting is an important consideration in the design of plastic containers, including plastic cans, because plastic material tends to be relatively expensive.
"Many plastic containers also lack the requisite circumferential or hoop strength that is required to avoid excessive deformation when the contents of the container becomes pressurized, such as during a heat sterilization process.
"The most common commercial procedure for heat sterilizing canned foods is a retort process in which filled but unsterilized sealed cans are placed in a retort chamber that is injected with steam and held at a predetermined elevated temperature (typically between about 210.degree. F. to about 260.degree. F.) for a predetermined period of time. Conventional plastic containers have been considered unsuitable for packaging applications in which heat sterilization is required, because the heat and pressurization that is inherent to such processes has the tendency to cause irreversible damage and deformation to the sidewall of the plastic can.
"The temperatures of the retort process are elevated enough to temporarily increase the internal pressurization of the container. Plastic retortable containers accordingly have been designed to permit limited and reversible controlled flexure of one or more surfaces in order to accommodate the internal volumetric changes that are inherent to the retort sterilization process. U.S. Pat. No. 5,217,737 to Gygax et al. discloses a retortable plastic container that has a flexible bottom portion to accommodate internal volumetric changes. Other retortable containers that have been in commercial use have a champagne style bottom portion that is designed to permit a certain amount of flexure. However, when using a continuous retort process the flexure of retortable plastic containers must be limited so that it will not interfere with the process of conveying the container through the continuous retort system. Typically, such conveyors require at least two dimensionally stable points of contact on the container.
"A need accordingly exists for an improved retortable container that exhibits improved dimensional stability and strength during the retort process without significantly adding to material costs."
In addition to obtaining background information on this patent, NewsRx editors also obtained the inventor's summary information for this patent: "Accordingly, it is an object of the invention to provide an improved retortable container that exhibits improved dimensional stability and strength during the retort process without significantly adding a material costs.
"It is further an object of the invention to provide a plastic container that has sufficient column strength and hoop strength to replace a glass or metal container, and that has sufficient rigidity and stability under elevated pressures and temperatures to permit heat sterilization without experiencing excessive deformation.
"In order to achieve the above and other objects of the invention, a plastic container according to a first aspect of the invention includes a bottom portion and a main body portion connected to the bottom portion. The main body portion has a plastic sidewall fabricated from a plastic material that is suitable for heat sterilization applications. The sidewall includes a plurality of circumferentially extending first sidewall portions and a plurality of circumferentially extending second sidewall portions, each of the second sidewall portions being interposed between two adjacent first sidewall portions. Each of the second sidewall portions includes a plurality of circumferentially spaced vertical columns, and wherein adjacent second sidewall portions are rotationally staggered with respect to each other so that the vertical columns on one second sidewall portion are not aligned with the vertical columns of an adjacent second sidewall portion.
"A reinforced retortable plastic container according to a second aspect of the invention includes a bottom portion and a main body portion. The main body portion has a plastic sidewall fabricated from a plastic material that is suitable for heat sterilization applications and is connected to the bottom portion. The main body portion has a reinforced sidewall area that includes a plurality of first sidewall portions and a plurality of second sidewall portions that are respectively interposed between the first sidewall portions. Each of the second sidewall portions is shaped to define a plurality of circumferentially spaced structures that are selected from the group consisting of indentations and projections.
"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."
For more information, see this patent: Yourist, Sheldon E.. Reinforced Retortable Plastic Containers. U.S. Patent Number 8646646, filed May 10, 2012, and published online on February 11, 2014.