Patent ID: 8074660

Claim:
A flat-folded, pleated face mask that is expandable into a cup shape for fitting over the mouth and nose of a person, comprising: at least one porous layer that comprises first and second major surfaces and that comprises at least two generally parallel, oppositely oriented pleats and that is capable of being expanded by at least partially unfolding the at least two pleats; and, at least one stiffening element adjacent at least a portion of the first major surface of the porous layer and with at least portions of the stiffening element being in overlapping relation with at least portions of the at least two pleats, the stiffening element comprising a sheet-like material comprising an interior area bounded by a perimeter, and wherein engaging features are provided at least at two locations on the perimeter of the stiffening element, wherein each engaging feature is arranged to allow sliding movement of an adjacent portion of the porous layer in a direction generally outward from the interior area of the stiffening element during expansion of the at least one porous layer into a cup shape, and wherein each engaging feature is further arranged to prevent sliding movement of an adjacent portion of the expanded porous layer in a direction generally inward toward the interior area of the stiffening element while the porous layer is in the cup shape.