Abstract
We discuss the characteristics of a flapper-nozzle system for water hydraulic servovalves. High-pressure water at the supply port is used for the first time as the working fluid for the hydrostatic bearings supporting the spool. Spool valve adhesion induced by poor lubrication with water is thus avoided. The fluid is then led to the ends of the spool and is used as the working fluid of the flapper-nozzle system. In this flapper-nozzle system the circumferential clearance of the spool becomes a laminar restriction that replaces the fixed orifice used in conventional servovalves. The linearity in the pressure-displacement relationship of the new flapper-nozzle system is better than that of conventional fixed orifice systems.
