Fire fighting foam mixing system

In a fire fighting system for proportioning injection of foaming agent in to a fluid stream, having

• a primary fluid delivery conduit having an inlet and an outlet;
• a foaming agent reservoir;
• means for conducting foaming agent from said reservoir to said fluid conduit adjacent the outlet thereof and;
• means for pressurizing said reservoir to expel foaming agent therefrom through said foaming agent conducting means including:
• a secondary fluid conduit between said primary fluid conduit adjacent the inlet thereof and said reservoir;
• the improvement comprising;
• a common means in said primary fluid delivery conduit for maintaining the fluid pressure adjacent the inlet thereof above the fluid pressure adjacent the outlet thereof and for varying the flow of fluid through said secondary fluid conduit;
• said
• means for varying the flow of fluid through said secondary fluid conduit including automatically operating adjustable means for constricting said conduit.

In a fire fighting system for proportioning injection of foaming agent into a fluid stream, having

• a primary fluid delivery conduit having an inlet and an outlet;
• a foaming agent reservoir;
• means for conducting foaming agent from said reservoir to said conduit adjacent the outlet thereof and;
• means for pressurizing said reservoir to expel foaming agent through said foaming conducting means including;
• a secondary fluid conduit between said primary fluid delivery conduit adjacent the inlet thereof and said reservoir;
• the improvement comprising;
• valve means in said primary fluid delivery conduit separating said conduit into inlet and outlet cavities;
• said valve means comprising;
• a first valve plate having a passage therethrough;
• a first spring means urging said first plate into a position separating said cavities;
• a second valve plate;
• a second spring means urging said second plate into a position closing said passage in said first valve plate;
• said first and second spring means being so proportioned in strength that, in response to rising pressure in said inlet cavity said second valve plate first will be moved out of its position closing said passage in said first plate, following which said first plate will be moved out of its position separating said cavities.