US Patent 7131550 Food storage containers

A lid for a food storage container includes a lid body with a vacuum sense opening and a vent opening extending through the lid body, a releasable cover disposed over the vent opening, and a pressure-indicating protrusion. The cover impedes air flow into the container through the vent opening until the cover is released. The pressure-indicating protrusion, which has a cavity in it, is in hydraulic communication with the container through the vacuum sense opening. The pressure-indicating protrusion contracts toward the vacuum sense opening in response to negative container pressure.