The spokes of two following discs are shifted one to the other and the discs are separated by an elastic ring put on the spokes. Thus, this ring acts as a spring that tends to open the lip formed by two discs. Ali discs are stacked on a central shaft connected to an helicoidal spring placed in the water inlet box.
Without pressurized water, the helicoidal spring keeps all discs in closed position.
With water under pressure, the spring is compressed and the lip of every disc opens. The opening port is equal for all discs thanks to the elastic rings.
The design of the helicoidal spring is executed in order to have fixed pressure losses for the min. and the max. operation flows. Thus, the spraying is constant for all the range of feed water flows.