Patent ID: 8360067

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 at least one pleat and that is capable of being expanded by at least partially unfolding the at least one pleat; and, at least one stiffening element adjacent at least a portion 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 one pleat, the stiffening element comprising at least one engaging feature in a first location on the stiffening element, wherein the at least one engaging feature is arranged to allow a portion of the porous layer that is adjacent the engaging feature to slidably move past the engaging feature in a first direction during expansion of the at least one porous layer into a cup shape; and, wherein the at least one engaging feature is further arranged to prevent a portion of the expanded porous layer that is adjacent the engaging feature from slidably moving past the engaging feature in a second direction opposite the first direction, while the porous layer is in the cup shape.