Exhalation valve assembly

Claim 1

A valve assembly for use in a volume ventilator, said valve assembly comprising a valve body having an exterior wall in part defining a pressure chamber, a gas inlet conduit in flow communication with the pressure chamber, said gas inlet conduit forming a discharge port in said pressure chamber, a gas outlet conduit in flow communication with said pressure chamber for directing gas out of said pressure chamber, said outlet conduit being located concentrically around said discharge port, diaphragm means removably disposed in and extending across said valve body, said discharge port, said outlet conduit and said pressure chamber being on one side of said diaphragm means, said diaphragm means including a central portion engageable with said discharge port for selectively closing off said discharge port, said diaphragm means defining the remainder of said pressure chamber and further including an annular arched portion which is spaced radially from said central portion, and a cover having a gas inlet joined to the valve body and extending across the diaphragm means on the opposite side thereof from the pressure chamber, said cover engaging and clamping the outer periphery of said arched portion, said arched portion being spaced in the direction of said opposite side from said central portion and said outer periphery, a generally tubular ring structure joined to said valve body and located concentrically between said discharge port and said exterior wall and within the pressure chamber, said ring structure being separate from said exterior wall by a predetermined distance and extending into said pressure chamber such that the ring structure engages and supports said arched portion of the diaphragm means between the exterior wall and the discharge port and thereby decreases the effective area of the diaphragm means, said ring structure being spaced in the direction of said opposite side from said discharge port and said outer periphery and normally engaging said arched portion when said diaphragm means is in its relaxed position, flow passages being formed between said ring structure and said outer wall and between said ring structure and said discharge port.