| 摘要 |
<p>The exhalation valve (14) of a respiratory face mask (10), while taking up only a small area, can afford extraordinarily low pressure drop for easy breathing if constructed with a valve seat (16) having a seal edge (18) that defines an orifice (21) and also forms a parabola in the plane bisecting the mask (10). Preferably the seal edge (18) forms a rectangle as viewed against the direction of composite fluid flow (34) through the valve (14), and a flexible flap (24) is attached to a bridge (19) across the center of the orifice at the apex of said parabola, each end of the flap (24) being free to be lifted to allow fluid to flow through the valve (14).</p> |
