<P> Directional control valves are one of the most fundamental parts in hydraulic machinery as well as pneumatic machinery . They allow fluid flow into different paths from one or more sources . They usually consist of a spool inside a cylinder which is mechanically or electrically controlled . The movement of the spool restricts or permits the flow, thus it controls the fluid flow . </P> <P> The spool (sliding type) consists of lands and grooves. The lands block oil flow through the valve body . The grooves allow oil or gas to flow around the spool and through the valve body . There are two fundamental positions of directional control valve namely normal position where valve returns on removal of actuating force and other is working position which is position of a valve when actuating force is applied . There is another class of valves with 3 or more position that can be spring centered with 2 working position and a normal position . </P>

Function of directional control valve in hydraulic system
find me the text answering this question