| 摘要 |
<p>TITLE OF THE INVENTION Gas Flow Control Valves In a demand valve for breathing apparatus gas flow is controlled by a main valve disc in accordance with the pressure in a control chamber. Gas vents from the control chamber through a bleed orifice at a rate dependent upon the deflection of a diaphragm sensitive to respiration and which controls the spacing of a spring arm from the bleed orifice. The arm has a set spacing from the orifice such as to provide "positive pressure" operation of the valve when the valve is connected into the inlet of an associated breathing mask. A lever on the valve contacts the mask inlet and acts through a pin to bias the arm to its "positive pressure" setting through a second spring arm. When the valve is disconnected the lever drops to allow the two arms to relax so that the first arm moves closer to the control chamber bleed orifice and thereby shuts off gas flow past the main valve disc.</p> |
