The prior art is replete with shipping and storage containers, many of which are collapsible for one reason or another. For example, U.S. Pat. No. 3,344,831 to Brackett discloses a collapsible container which is supported on or attached to a carrier vehicle. The container has a portable base frame which is expandable automatically upon reception of liquid or grain to be shipped. The container walls are constructed from durable foldable material to ensure safe handling of the substance being shipped and are suitably attached to the base frame along with a pair of framed doors. The container is also sufficiently flexible to allow expansion or contraction without venting which reduces or eliminates spoilage and fume leakage. The collapsed device facilitates easy storage because of its reduced height, which may only be 20% of its expanded height. The collapsed container is also usable as a pallet in its collapsed position.
U.S. Pat. No. 3,840,135 to Bridge discloses a collapsible cargo container having a grill-like metal base, end walls pivoted to opposite ends of the base at different levels to be folded on top of the other and removable sidewalls carried on posts detachably connected to the base and lifted from the top by a harness and lift truck. The posts transfer the lifting loads to the base free from the sidewalls of the container. The side and end walls are in the form of an open framework having cords interlaced there across under tension. Plastic panels may be mounted inside the cords to protect the contents of the container from pilferage.
U.S. Pat. No. 4,557,400 to Clarke discloses a carrier unit that can be converted from a general cargo carrying unit to a bulk material carrying unit. In converting the unit to a bulk carrying unit, a flexible liner is removed from the hopper and pulled to extend the length of the unit's compartment to define a liner compartment for holding bulk materials. The flexible liner conforms to the shape of the compartment as such is defined by the walls, the ceiling and the vertical floor sections of the compartment, etc.
U.S. Pat. No. 3,980,196 to Paulyson et al, discloses a container utilizing a flexible liner bag for carrying bulk cargo such as grain. The liner bag can be formed as a seamless tube of polyethylene about six mils thick, squared and sealed at its ends to provide a 20 or 40 foot long, generally rectangular bag. The bag has two loading apertures through its upper rear wall. The bag is supported by an external support frame. To discharge or unload cargo from the bag, the bag is pierced and cut. The container holding the bag is then tilted to pour the cargo from the container.
U.S. Pat. No. 3,868,042 to Bodenheimer also discloses a container for the transportation of bulk cargo which includes a disposable container liner positioned within the container. The container also includes means for removing air from the container liner as the liner is being filled with bulk cargo.
U.S. Pat. Nos. 4,054,226 to Bjelland et al; and 3,616,957 to Patton also disclose various types of cargo shipping containers.
While the foregoing patents disclose various containers for the shipment of bulk cargo, some of which are collapsible and some of which utilize plastic liners, a need still exists for a flexible, collapsible container that does not require an extensive external support framework. A need also exists for a flexible, collapsible container which is sealable so that material can be transported and stored in the container under either a vacuum or a positively pressurized atmosphere. Such an atmosphere could be; for example, a gaseous nitrogen atmosphere which would be of value in shipping grain since nitrogen is a grain preservative.