Respirator pressure-demand exhalation valve

A pressure-demand exhalation valve for a respirator facepiece, the valve comprising a case provided with a chamber having spaced end walls surrounded by a side wall, one of said end walls being provided with an inlet port for exhaled air, a valve seat surrounding said port and spaced inwardly from said side wall, a sealing member having one side normally engaging said seat, a rigid disc engaging the opposite side of the sealing member and connected thereto, the diameter of the disc being nearly as great as the diameter of said chamber, a valve stem secured to the central portion of said disc and extending through said port, guide means for the valve stem connected with the case, and a spring in said chamber compressed between said disc and the other end wall of the chamber for normally pressing the sealing member against said seat, the disc being spaced from said one wall of the chamber far enough for the marginal portion of the disc that extends laterally out beyond the valve seat to be inclined toward said one wall but spaced therefrom, the side wall of said chamber being provided with a plurality of exhaust slots extending around said disc and having inner walls adjacent said one wall of the case lying in a plane substantially coinciding with the plane in which lies the edge of the disc that is closest to said one wall of the case, and the space between said valve seat and the side wall of the case always being open to said slots.