"Pass" and "position" are important concepts of pneumatic reversing solenoid valves. Different "passes" and "positions" constitute different types of pneumatic reversing solenoid valves. Generally speaking, the "two-position valve" and "three-position valve" refer to the valve core of the reversing valve with two or three different operating directions. The so-called "two-way valve", "three-way valve", "four-way valve" refers to the valve body of the reversing valve has two, three, four non-communicative and can be connected with different oil pipes or gas in the system, between different oil ducts/gas paths can only communicate with the valve port switch when the valve core is shifted, you have to see how many operating conditions of this valve, it can be said that it is a few, if there are pneumatic component symbols, it is better to understand, on the symbol on behalf of the valve body of the square (with arrows or T lines) a few is a few. The "passes" in the back represent a few points (points that intersect with the arrow line and the T line) on a square in between.
The meaning of pictorial symbols is generally as follows:
(1) Use a box to indicate the operating direction of the valve, and a few boxes indicate how many "positions";
(2) The arrow in the box indicates that the oil circuit is in the connected state, but the direction of the arrow does not necessarily indicate the actual direction of the liquid flow;
(3) The symbol "┻" or "┳" in the box indicates that the passage is impassable;
(4) The number of interfaces connected to the outside of the box indicates how many "passes";
(5) The oil inlet/air inlet of the general valve and the oil supply circuit or gas connection of the system is indicated by the letter P; The oil/return port where the valve communicates with the oil return/gas path of the system is indicated by T (sometimes O); The oil/port where the valve is connected to the fulfillment element is indicated by A, B, etc. It is sometimes indicated by a |.
(6) The reversing valve has two or more operating directions, one of which is the normal position, that is, the position where the valve core is not subjected to longitudinal force. The median position in the graphical symbol is the normal position of the three-position valve. In the case of a two-position valve that uses a spring return, the normal position is the path condition in the frame close to the spring. The production system diagram shows that the oil/gas circuit is generally connected to the normal position of the reversing valve.
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