Hydraulic servo system for machine tool - utilises Bernoulli effect force on valve piston to maintain constant output velocity

摘要

A toll is positioned by a double acting hydraulic cylinder which is supplied through two electro-hydraulic control valves. The control valve pistons are moved against springs by solenoids which receive input signals according to the desired position and velocity of the tool. The strength of the signal supplied to the solenoids of the main control valve is adjusted so that the valve piston is moved a limited amount against the centering springs. This opens the ports by an amount which produces a hydraulic force to keep the piston in a position which maintains a constant velocity of the tool.