Multi-function valve for a riser in a sprinkler system

A valve for installation in a riser of a sprinkler system to provide both automatic flow stop and back flow prevention, the valve comprising:

• a main body having a generally cylindrical portion;
• means comprising a circumferential flange projecting from the body for securing the main body in a fixed position within the riser;
• the main body having an inlet end which defines a flow-stop valve seat, an outlet end which defines a back-flow valve seat, means defining a bore extending between the inlet and outlet ends, and channel means in parallel with the bore defining a flow path for water flow during normal sprinkling operations;
• a shaft which extends through the bore and which is movable between opposite end positions;
• a pair of annular members fixed to shaft at spaced-apart locations such that translatory motion of the shaft toward the outlet end causes one of the annular members to be moved into abutment with the flow-stop valve seat and close the flow-stop valve, and such that translatory motion of the shaft toward the inlet end causes the other annular member to be moved into abutment with the back-flow valve seat and close the back-flow valve;
• a spring surrounding the shaft, the spring having opposite ends;
• the main body having a surface bearing against one end of the spring, one of the annular members bearing against the opposite end of the spring;
• the spring having a spring constant such that the spring is forced into limited compression in the presence of normal water flow though the flow path, and such that an abnormally high flow rate causes sufficient compression that the flow-stop valve closes.