BACKGROUND PRIOR ART
Patents for composite contasiners have been issued since 1920. These containers consist of an outer container that provides structural strength for an inner liner that is normally a flexible type material that may be easily installed inside the outer container. An example of this is disclosed in U.S. Pat. No. 4,466,553. However, the liner in the above patent does not adhere to the outer container, leaving s space between the liner and the outer container. In the packaging or canning of vegetable products, it has been customery to provide a rigid metal container that is corrugated around the cylindrical peripheral intermediate portion to provide rigidity for the container. This featurs allows it to withstand crush pressures as well as resisting collapsing during various phases of packaging and processing of the product therein.
Conventionally, in the packaging of sanitary food products, the metal container must be internally lined to prevent any contamination of the product during processing and storage prior to ultimate use. In the transportation of various articles, many times the articles are stacked in numerous cases upon each other which means that the lower container must be capable of resisting substantial crush pressure from the remaining containers supporterd thereon. It is also possible for the containers to be dropped, and must withstand the forces encountered without collapsing.
Numerous attempts have been made to substitute various types of less expensive and less rigid packages, particularly for food products and an example that has been dealt with for a number of years is what is refered to as a “retort” pouch. In order to meet the various government requirements, the typical pouch construction consists of a layer of polypropylene attached through an adhesive to an aluminum foil layer with a further polyester layer, adhesively secured to the opposite sides of the foil. The aluminum foil provides oxygen barrier resistance that is required for packaging such products, while the polypropylene is used to provide chemical inertness for the product and the polyester layer produces the necessary mechanical strength for the pouch.
One of the main problems with a pouch of this type, when used for packaging food products is the fact that the relatively flexible package slows the filling speeds of the filling line and therefore increases the cost thereof For example, pouches of this type reqwuire a special system that will provide a mechanical support for the pouch during the heating or processing operation for the contents.
A further problem that has been encountered with the pouch type package is the fact that the pouch does not have sufficient rigidity to be self-supporting without collapsing during shipment and display. Thus most pouches that are utilized for packaging particularly food products are of necessity placed in an outer cardboard or other carton for shipment or display purposes, adding to the overall cost of the package.
The art of normal paper container production consists of the following steps:
1. Paper for the side wall is sprayed with Polyethylene or wax, blanked to size, and fed into a cone shaped mandrel on an assembly machine.
2. Paper for the bottom is sprayed with Polyethylene or wax, blanked to the proper size, shaped and attached by vacuum to a mandrel
3. These parts are joined as the rotary indexing dials align. The bottom is blown or sucked onto the mandrel holding the side wall. The side seam, whose ends overlap is ultrasonically sealed as well as the bottom to the side wall.
4. The side wall is pushed into the bottom to secure a bottom seal. See FIG. 1, Patent drawing 1.
5. The top curl is formed on the cup by engaging a heated die set, which permits the curl to be formed.
In the above steps(1 through 4) it is self-evident that flaws exist with the procedure. such as:
1. The side wall must be perfectly aligned with its cone shaped mandrel, lest it does not properly align with the bottom.
2. The bottom must be perfectly aligned on its mandrel, lest it does not properly align with the side wall.
3. If the side wall is erroneously located on its mandrel, the side seam will not be perfectly formed and will not attach properly to the bottom.
4. Any flaw (hole) in either the side wall blank or bottom blank will cause the container to leak.
However, unless protected by Sensors, the container may still be produced with its flaws. All the above conditions, if not properly met will cause leaking at the side seam or bottom, possibly inflicting personal injury. The present invention does not depend on any of the above conditions. The lining of the containers will prevent any leaks to occur, as the lining is attached to the container after the container is formed. The lining is sealed to both the side wall and the bottom, regardless of any flaws to the outer container, and it will hold any ingredients, whether hot or cold. The container supporting the liner is used for structural integrity only.
SUMMARY OF THE INVENTION
According to the present invention, a container has been developed which has less structural requirements than a conventional metal can without sacrificing rigidity such as occur when using flexible contaiers.
The container of the present invention comprises a composite container construction including an outer container that has a bottom wall and a side wall that corresponds substantially in configuration to the outer container and has an open top for receiving a product.
The inner and outer containers are sealed to each other completely from top to bottom. The outer container provides structural rigidity to meet stacking and abuse resistance requirements. Air trapped between the inner and outer containers is removed, before sealing, by the introduction of heat and vacuum.
In one embodiment of the present invention, the container is not detrimentally affected by microwave nor freezing temperatures. The lining, being non-toxic is acceptable for food service.
In another embodiment of the present invention, the Moisture Vapor Transfer Rate has been reduced to acceptable levels for any particular product.
It should be pointed out that all embodiments, the term film is intended to encompass a single sheet, or a composite structure such as a laminated sheet.
While this invention is susceptible of embodiment in many different forms, it must be understood that the present disclosure is to be considered as an examplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated.