Pressure relief valve for packing containers

Claim 1

A package for holding contents which emit gas while contained in said package, said package comprising walls defining a container enclosure structure, one of said walls having gas outlet passage means extending therethrough, a valve unit carried on said one wall and in communication with the gas outlet passage means therein, and a covering member disposed over said valve unit and connected with said one wall, said covering member having at least one opening therein with said valve unit being operable to allow gas flow from the interior of said package through said passage means and outwardly through said covering member opening, said valve unit including a porous element impregnated with a relatively low volatility chemically stable liquid insensitive to oxygen, to provide a gas flow blocking layer of said liquid in the pores of said element, said porous element being in sealed fixed relationship around the periphery thereof with said package one wall and said covering member such that gas outflow from the gas outlet passage means through said opening can only occur through said porous element and not around it, the liquid having sufficiently high cohesivity or high surface tension and the porous element having sufficient pore size such that the presence of gas pressure in said container in excess of a predetermined value ruptures the liquid layer in the pores of said element whereby gas outflow occurs through said element, with the liquid layer in said pores restoring when the gas pressure in said container reduces to at least said predetermined value.