Abstract: A ventilator exhalation valve for controlling the exhalation flow rate and pressure is disclosed. The valve includes a free-floating diaphragm which is biased against a fixed valve seat in an inhalation configuration of the valve so as to prevent flow through the valve in the reverse direction. As flow in the forward direction passes through the valve, the bias urging the diaphragm onto the valve seat is overcome and the diaphragm is separated from the valve seat, so as to contact a poppet affixed to a shaft. The shaft includes a ferromagnetic portion and is attached to linear actuator which is retained by substantially frictionless suspension system including a pair of substantially planar spring flexures. As the poppet moves in response to flow between the fixed valve seat and the diaphragm, ferromagnetic portion of the shaft is displaced relative to a fixed coil thereby inducing a current in a coil. The current is monitored to provide a feedback signal corresponding to the velocity of the poppet.

Abstract: An apparatus for detecting fluid flow by obtaining a differential pressure across an obstruction in a fluid conveying channel. The obstruction is hingably connected to the housing of the channel. The connection is of a width substantially less than the periphery of the channel so as to reduce the collection of contaminants which decrease the accuracy of the apparatus. Because the orifice defined by the area between the obstruction and the periphery of the channel is variable according to the fluid flow, the pressure differential versus flowrate relationship is different from the square-law relationship of a fixed orifice, and provides a relatively high pressure differential at low flowrates and a relatively low pressure differential at high flowrates.