Fluid under pressure is continually delivered to the lower end of differential servomotor 1 in which the effective areas above and below the piston differ. When valve spool 3 is shifted downward, fluid delivered to the valve is directed to the upper end of servomotor 1. Owing to the difference in areas, piston 2 of the servomotor moves downward. When valve spool 3 is shifted upward, the upper end of the servomotor is connected to the tank and piston 2 moves upward due to the action of the constant pressure under the piston.
$3750$SHP,Dr$