Pressure relieving closure cap

Claim 1

In a cap for closing a container, a combination comprising first wall means defining an enclosed space; second wall means connected to said first wall means and subdividing said space into a first and a second chamber and including a circular plate formed with an annular elevated portion in the central region thereof facing said second chamber and surrounding a circular depression; means for establishing communication between said first chamber and the exterior of said first wall means; means for establishing communication between said second chamber and the interior of the container; means for establishing communication between said first and second chambers and including at least one aperture in said second wall means radially outwardly of said elevated portion; and means situated in said second chamber and operative for controlling the passage of a gaseous fluid through said aperture and including an elastically yieldable diaphragm having an outer marginal portion fluid-tightly connected with said circular plate and an inner marginal portion bounding a central hole in said diaphragm communicating with said depression, and normally urged by pretension in said diaphragm into contact with said elevated portion, and at least one groove extending in said elevated portion radially outwardly thereof for establishing communication between said depression and said aperture, whereby the gaseous fluid is permitted to pass at least from said second chamber into said first chamber at a first volumetric rate when the pressure in the former exceeds that in the latter, and from said first chamber into said second chamber at a second higher volumetric rate when the pressure in the former exceeds that in the latter to such a degree that said inner marginal portion of said diaphragm is deflected out of contact with said elevated portion of said circular plate.