Patent ID: 7399263

Claim:
A method of making a plurality of containers, said method comprising the steps of: manufacturing a plurality of container structures, each container structure having an opening therein, separately manufacturing a plurality of valves, each valve comprising a vent layer which is pervious with respect to expected gasses and a sealable area, aligning each of the valves with the opening in a container structure so that the sealable area forms a sealed passageway between the vent layer and the container structure, and securing the aligned valves to the container structures; wherein the valve manufacturing step comprises the steps of: providing a vent material which is pervious with respect to expected gasses, cutting the vent material into shapes corresponding to the shape of the vent layer, providing a cover material which is impervious with respect to the expected gasses, overlaying the vent material and the cover material so that the outer surface of the vent material is adjacent an inner surface of the cover material, and securing the outer surface of the vent material to the inner surface of the cover material; wherein the cover material is also cut during said cutting step and the valves also each include a cover layer and an area between the vent layer and the cover layer.