Abstract: A demand regulator for self-contained underwater breathing apparatus has a housing and a cover forming a breathing chamber with a mouthpiece. A diaphragm on the chamber is movable with changes in pressure due to user inhalation demand. An inlet valve coupleable to a supply of pressurized air is responsive to the position of the diaphragm. At least one manually adjustable fin can be retracted or positioned across the air flow path through the chamber, for setting the extent of venturi effects tending to displace the diaphragm and open the valve to free flow in the absence of inhalation demand. The venturi adjustment mechanism has a sealed rotatable arm with a radially extending end in sliding engagement with the fin, and preferably the fin has two resilient strips that are spaced apart by a dimple.

Abstract: An improved pressure regulator (60) is provided with an eductive flow to maintain the outlet pressure at increased flows through the regulator. The improved regulator broadly includes a body (61) provided with a bore. A valve seat (24) is movably mounted in the bore to provide a valve seat. A valve member (68) is mounted in the body bore for controlled movement toward and away from the seat to vary the area of a main orifice through which fluid is adapted to flow from an inlet to an outlet. The body has a sensing passage (73) communicating a portion (76) of the bore with the exit passage (65). The facing surfaces (74, 76) of the bore and valve member are so dimensioned and configured as to provide an elongated open-ended annular space (78) therebetween that extends along the guide passage from its communicative intersection with the exit passage to a point beyond which the sensing passage communicates with the guide passage.