Patent ID: 7490623

Claim:
A one-way pressure-relief valve ( 4 ) applicable to a package ( 1 ) which contains a gas releasing product, said package ( 1 ) comprising walls defining a package structure for said product, one of such walls ( 2 ) bearing at least one orifice ( 3 ) for said gases to be expelled, on which orifice the one-way valve ( 4 ) is applied, said valve ( 4 ) comprising a thin flexible bottom sheet ( 5 ) provided with an opening ( 7 ) and a thin flexible top sheet ( 6 ) overlapping said bottom sheet ( 5 ), said valve ( 4 ) characterized in that said bottom sheet ( 5 ) is attached to said top sheet ( 6 ) in a region delimited by the edge of said valve ( 4 ) and a closed perimeter ( 7 ′), said closed perimeter ( 7 ′) being defined on a substantially central region of said valve ( 4 ) surrounding said opening ( 7 ); a portion of said closed perimeter ( 7 ′) being located substantially near a portion of the perimeter of said opening ( 7 ), defining a first sector ( 8 ) within which a gas medium is enclosed, and the remaining portion of said closed perimeter ( 7 ′) being located substantially apart from the remaining portion of said opening perimeter ( 5 ), defining a second sector ( 9 ) within which a fluid medium is enclosed; and in that said top sheet ( 6 ) bears at least one micro-perforation ( 10 ) in a region of the surface thereof which is located above said second sector ( 9 ).