Air valve for a breathing system

Claim 1

An emergency air valve for a system for administering an anesthetic gas comprising: a circular plate having a flat top surface and a bottom surface and a central opening therethrough for the passage of a gas, and a resilient diaphragm overlying the top surface of the plate and having a central opening aligned with the opening in the plate, said diagragm having an upper surface, a lower surface, an outer annular region and a flat intermediate region surrounding said central opening, said diaphragm capable of assuming a first undistorted position in which said intermediate region remains flat and a second distorted position in which said intermediate region is flexed, said diaphragm further includes a circular portion with a sharp edge depending from said lower surface and surrounding said central opening, said sharp edge adapted to contact the top of the plate surrounding the opening in the plate to effect a seal between the diaphragm and the top of the plate, said sharp edge being lower than the bottom surface of the diaphragm when said diaphragm is in its first position, cap means mounted on the plate and bearing on the outer annular region of the diaphragm for securing the outer region of the diaphragm to the top surface of the plate at a substantial distance from said depending portion thereby distorting said intermediate region and urging the sharp edge toward the top surface of the plate and forming with the diaphragm a closed chamber above the diaphragm, said plate also forming with the diaphragm in its second distorted position a chamber below the diaphragm, said plate having at least one other opening therethrough communicating the chamber below the diaphragm to the atmosphere.