The number of squares (containing arrows or T-lines) representing the valve body on the symbol indicates the number of digits. The "number of connections" indicates the number of points (intersecting with arrows and T-lines) on one of the squares.
The meanings of graphic symbols are generally as follows:
(1) Use boxes to represent the working position of the valve. The number of boxes indicates the number of "positions".
(2) The arrow in the box indicates that the oil circuit is connected, but the direction of the arrow does not necessarily indicate the actual direction of the fluid flow;
(3) The symbol “┻” or “┳” in the box indicates that the passage is blocked;
(4) The number of interfaces connected to the outside of the box indicates the number of "connections";
(5) Generally, the oil/air inlet of the valve connected to the system's oil supply or air supply is represented by the letter p; the oil/air return port of the valve connected to the system's oil/air return line is represented by t (sometimes o); and the oil/air port of the valve connected to the actuator is represented by a, b, etc. Sometimes, l is used in the graphic symbol to represent a leakage port;
(6) Directional control valves have two or more operating positions, one of which is the normal position, i.e., the position when the valve core is not subjected to operating force. The middle position in the graphic symbol is the normal position of a three-position valve. For a two-position valve that uses a spring return, the normal position is the passage state within the box closest to the spring. When drawing a system diagram, the oil/air passage should generally be connected to the normal position of the directional control valve.
