When the water level in reservoir becomes low, the chamber connecting with pilot valve inside of body becomes in the condition of atmospheric pressure as opening pilot valve. At this time the power which subtracts the weight of piston assembly paying regard to buoyancy and the reaction force of spring from the power which multiply the difference of width(A-B) by the pressure of fluid supply lifts up piston and fluid can flow toward outlet.
CLOSE
When the water level in reservoir reaches to high water level just, pilot
valve will automatically close. In this point, the chamber pressure inside
of body is the same with the pressure of inlet by water route through
the chamber and the liquid room of inlet, fluid flowing toward outlet
will close since disc closes valve seat as moving downward by the weight
of piston assembly and the power of spring. At this time, liquid pressure
by the area of valve seat is total power of valve closing.
Control
Shaft
Since flow rate out will be adjusted by the cycle height of piston moving,
the cycle height of piston can control using control shaft same as the
figure and can control flush out pressure and meeting spot condition.