Patent ID: 7311104

Claim:
A method of making a filtering face mask that has an exhalation valve secured thereto, which method comprises: (a) providing (i) a valve seat that comprises an orifice, a flap-retaining surface, and a seal ridge that terminates at a seal surface, wherein the orifice allows air to pass therethrough and is surrounded by the seal surface, and (ii) a single flexible flap that has a periphery; (b) supporting the single flexible flap at the flap-retaining surface non-centrally relative to the orifice and operatively relative to the seal surface of the valve seat such that: (i) the flexible flap assumes, in its closed state, a curved profile in a cross-sectional view thereof, which curved profile comprises a curve that extends from a first point where a first stationary portion of the flexible flap is supported on the valve seat to a second point where a second free portion of the flexible flap contacts the seal surface; (ii) the second free portion of the flap is pressed against the seal surface of the valve seat in a closed state of the exhalation valve; (iii) the second free portion of the flexible flap is held in its closed state under any orientation of the valve, at least in part, by virtue of the curved profile thereof; (iv) the second free portion of the flexible flap includes a free segment of the periphery and represents the only free portion of the flap and can flex so as to permit exhaled air to pass through the orifice and to provide an open state of the exhalation valve to make the flexible flap out of contact with the seal surface at the second point while the first portion of the flexible flap includes a stationary segment of the periphery opposite at least part of the free segment and remains essentially stationary at the first point; and (v) the stationary portion of the flexible flap when viewed from the side in cross-sectional profile extends from the first point where the flap is supported on the flap retaining surface to the stationary segment of the periphery of the flap; and (c) attaching the valve seat to a mask body that is adapted to fit over the nose and mouth of a person.