Detailed explanation of the concepts of \"number of positions\" and \"number of ports\" in pneumatic valves

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“\"Throughflow\" and \"position\" are important concepts in pneumatic directional control valves. Different \"through\" and \"position\" configurations result in different types of pneumatic directional control valves. The so-called \"2-position valve\" and \"3-position valve\" refer to directional control valves whose spool has two or three different operating positions. The so-called \"two-way valve\", \"three-way valve\", \"four-way valve\", and \"five-way valve\" refer to directional control valves whose body has two, three, four, or five separate interfaces that can be connected to different air lines in the system. Communication between different air paths is possible only through the opening and closing of the valve ports as the valve core moves. Regarding the term \"several\" mentioned earlier, it depends on how many operating states this valve has; that number indicates how many there are. If there are symbols for pneumatic components, it becomes easier to understand – the number of squares representing the valve body in the diagram (with arrows or T-shaped lines inside) corresponds to the number of operating states. And the “several crossings” referred to later represent the number of points on one of the squares (the points where it intersects with the arrow lines and T-lines); that number is what constitutes the several crossings. The meanings of the graphic symbols are generally as follows: (1) A box is used to indicate the operating position of the valve; the number of boxes indicates the number of \"positions\"” ； (2) The arrow inside the box indicates that the gas path is in an open state, but the direction of the arrow does not necessarily represent the actual direction of gas flow ； (3) The symbols “┻” or “┳” within the box indicate that the path is blocked ； (4) The number of interfaces connected outside the box indicates the number of \"channels\"” ； (5) Generally, the air inlet of the valve that is connected to the system air is denoted by the letter P ； The exhaust port of the valve that is connected to the system’s return air path is denoted by R (sometimes by EA or EB) ； The ports through which the valve is connected to the actuator elements are denoted by A, B, etc. (6) Directional control valves all have two or more operating positions, one of which is the normal position, that is, the position in which the valve spool is when no controlling force is applied. The median in the graphic symbol represents the normal state position of the three-way valve. A two-position valve using spring return has the path state within the box adjacent to the spring as its normal position. When drawing a system diagram, the gas line should generally be connected to the normal position of the directional control valve.