UNIDIRECTIONAL FLUID VALVE

摘要

Filtering face mask 10 has a mask body 12 and an exhalation valve 14. The mask body 12 is adapted to fit over the nose and mouth of a person, and the exhalation valve 14 is attached to the mask body 12. The exhalation valve 14 has a valve seat 26 and a single flexible flap 24. The valve seat 26 includes a seal surface 31 and an orifice 32. The orifice 32 is circumscribed by the seal surface 31. The single flexible flap 24 has a fixed portion 28 and one free portion 38. The one free portion 38 has a free end, and the fixed portion 28 is located off-center of the flexible flap 24 away from the free end and is secured to the valve seat 26 outside the orifice 32. The one free portion 38 is pressed toward the seal surface 31 when the wearer is neither inhaling or exhaling. The free portion 38 can be lifted from the seal surface 31 during an exhalation. Because the flexible flap 24 is mounted to the valve seat off-center and outside the orifice 32 and yet is pressed towards the valve seat 26 when the wearer is not inhaling or exhaling, the face mask 10 can demonstrate a lower air flow resistance force during an exhalation which enables the exhalation valve 14 to open easier, and it can remain closed under any static orientation of the valve 14 to prevent contaminants from entering the mask interior.