US Patent 7175100 Fail-safe proportional mixing valve

A fail-safe proportional mixing valve is provided that tempers a hot fluid supply by proportional flow from a hot fluid inlet and a cold fluid inlet. The valve includes a fail-safe mechanism disposed within the body of the valve to isolate flow from the hot fluid inlet in the event the temperature of the mixed fluid exceeds a predetermined set point. The valve also includes a check valve in the fluid inlets to prevent backflow in case of failure of a fluid supply. In a further aspect, the cold fluid inlet includes an adjustment set screw to adjust the cold fluid flow into the mixing valve, thereby adjusting the maximum mixed fluid temperature that can be discharged from the valve assembly.