| 摘要 |
A pressure balancing foam valve includes a body having a liquid inlet at one end and a liquid outlet at an opposite end, and having an annular passage therethrough. A first stage pressure regulating assembly is disposed within the annular passage of the valve and includes a shaft that is attached at a first end to the liquid inlet. A one-piece pressure disc is slidably disposed on the shaft. The disc is urged into a seated position against an end portion of the liquid inlet by a spring interposed between the pressure disc and a second end of the shaft. The spring is selected so that the pressure disc is placed into the seated position during low pressure conditions to prevent liquid flow through the valve, and to permit compression by force of the disc from increasing liquid pressure to unseat the disc and permit liquid flow through the valve. A second stage pressure regulator is a venturi-shaped annular passage through a wall portion of the liquid outlet. A high-pressure inlet port is disposed through a wall portion of the liquid inlet, and a foam outlet port is disposed through a wall portion of the liquid outlet. The high-pressure inlet and foam outlet ports are connected to a foam delivery system. The pressure disc and venturi together provide a differential pressure within the valve proportional to changing liquid flow rate and pressure, thereby ensuring a desired degree of foam pressurization and accurate foam delivery into the liquid at low to high volumetric flow rates. |
