Valve Mechanism

Directional control valves encompasses a valve body or valve housing and a valve mechanism which is usually mounted on a sub-plate. In valve mechanism, the ports of the sub-plate are threaded, so as to hold the tube fittings which connects the valve to the fluid conductor lines. This valve mechanism directs the fluid inside the valve body to the selected output ports, or on the other hand, stops the fluid from passing via. the valve. The external signal commands i.e. electrical, manual & pilot pressure, and internal signal commands i.e. pilot pressure, and spring force can be used to move the valve mechanism

Spool, rotary or plug rotary disc mechanisms are most importantly applied for directional control valves, whereas poppet's and balls are mostly preferred mechanisms for checking valves and shuttle or function valves.

Valves which are inclined towards the spring are said to have a normal position. Hence, any external command will progress the valve mechanism to the actuated position. In the case, if there are three-position valve as shown in the figure below, the valve's normal position is the spring-centered position.