The invention relates to containers, and more particularly to an insulated container possessing impact cushioning characteristics with an improved ability to maintain a desired limited cold or hot temperature range for an extended period of time.
The shipment and handling of various goods and commodities, such as blood, drugs, vaccines, frozen foods, catalysts, chemicals, and the like, requires that the shipping container be well suited for cold or hot storage and that it have the ability to maintain the shipped product in a particular environment over a limited temperature range during the course of shipment and handling. In designing such a shipping container, the weight of the empty container is of significance; for instance, many perishable goods travel by air to distant destinations. The size and configuration of the container is also a design consideration, whether ground or air transportation is employed. The materials from which the container is constructed constitute a further factor in its design, since it is desirable to form the container from low cost materials which yield an easily assembled container which, where required, can be quickly disassembled for storage and/or re-shipment. It is further desirable to fabricate the container from materials which are relatively resilient to the customary impact shocks and blows encountered in shipment, and which provides satisfactory protection from damage incurred by the container through rough handling. A shipping container for cold or hot storage must therefore maximize the protection and preservation ability of the container, and minimize the cost and difficulty of construction of the container.
It is well known in the prior art to provide a shipping container with foam insulation as both the means to preserve a cold temperature storage environment within the container as well as protect the enclosed product from damage. In Cline et al, U.S. Pat. No. 3,4l6,692, a cold storage shipping container is disclosed which is semi-rigid and self supporting. The container has walls composed of a flexible and resilient foamed insulating material of an interconnected open-cell type which is enclosed within a fluid impervious casing, possessing a similarily composed cover. Since the walls and bottom of the container are an integral unit, the container cannot be knocked-down for storage or shipment. The container is typical of those types of shipping containers having walls composed of an insulating material encased between outer and inner walls. Such a container, though having flexible walls, is relatively expensive, since the encased insulation assembly is fairly elaborate. Further, this type of container must be purchased in assembled form, and cannot be compactly shipped or stored by the user for later assembly, as needed.
Likewise, it is known in the art to use an open-celled insulating foam material for insulating and protective purposes in containers. Such foam material as used in Cline, U.S. Pat. No. 3,416,692, is of an interconnected open-cell type, such as polyurethane, where the interstices between the foam cells reduce the circulation of gases from the colder interior compartment through to the outer warmer side of the container. However, the ability of such open-celled foam to hold a reduced temperature within a shipping container is far inferior to closed-cell foam such as polystyrene, which material has a relatively low susceptability to internal convective circulation or direct transmission of gases.
Ernst, et al, U.S. Pat. No. 3,890,762, shows a produce shipping container comprised of a common corrugated paperboard box and six closed-cell polystyrene foam panels, the six panels respectively residing in facial engagement with the sides, top, and bottom of the box. The panels are of a rigid foam, however, and thus provide a limited amount of protection to the contained product from damage through shipping and handling. Rigid panels of this type are also subject to chipping and breaking, which effectively degrades the container's ability to maintain a reduced interior temperature, and limits the commercial life of the container itself for re-use where desired.
The temperature preservation ability of the Ernst container further suffers from the employment of a type of closed-cell foam which will conduct the gases in the interior of the container to the ambient atmosphere or vice versa. The absence of an effective barrier to the flow of vapors between the interior and exterior of the container significantly reduces the shipping container's ability to maintain the requisite storage environment. In point of fact, the foam material specified in Ernst was selected for its ability to permit rapid temperature modification of the contained produce through cooling by an external source.
The prior art thus fails to provide an inexpensive and easily assembled light-weight, reusable shipping container having the improved ability to maintain a desired limited cold or hot temperature range over a long period of time while providing adequate cushioning and protection for the contained product.