Types and symbols of cylinder reversing valves

The cylinder reversing valve is a valve that changes the direction of the air flow by changing the gas path, such as air intake to one end of the cylinder and exhaust from the other end.






Cylinder reversing valves are classified according to control methods:


Electromagnetic control: When the electromagnetic coil is energized, the static iron core generates electromagnetic attraction to the moving iron core to switch the valve to change the direction of the air flow. It is called an electromagnetic control directional valve, or solenoid valve for short.
Air pressure control: A control method that uses air pressure to control valve switching.
Human control: A control method that relies on human power to switch the valve.
Mechanical control: A control method that uses cams, bumpers or other mechanical external forces to switch the valve.







The symbol representation of the control mode of the cylinder reversing valve is as shown in the figure below:








Classification according to the number of ports of the valve:


Two-way valve: has an inlet (indicated by P) and an outlet (indicated by A).
Three-way valve: has one inlet, one outlet and one exhaust port (indicated by O or R);or two air inlets and one exhaust port.
Four-way valve: It has four ports. In addition to P, A, and R, there is also an output port (represented by B). The paths are P>>A, B>>R or P>>B, A>>R.
Five-way valve: It has five ports. In addition to P, A, and B, there are also two exhaust ports (indicated by R and S). The paths are P>>A, B>>S or P>>B, A>>R.







The cylinder reversing valve is represented by the port number symbol as shown in the figure below:









Classification according to valve switching status:


The switching state of the directional control valve is called the position, and the several switching states are called several valves. The rest position of the valve (that is, the state without a control signal) is called the zero position. The zero position of the solenoid valve refers to the state when the power is turned off.





Classification according to valve core structure:


There are lift type and sliding column type
Characteristics of poppet directional valve
Suitable for large traffic situations. Due to the short stroke and small flow resistance of the valve, the cut-off type valve has a smaller appearance than the sliding column type valve with the same diameter specification.
The valve core is always subject to back pressure, which is beneficial to sealing. The requirements for air source purification are lower.
At high pressure or large flow, the required reversing force is larger and the reversing impact force is larger. Therefore, stop valves often adopt a balanced valve core structure. Large diameter stop valves should adopt pilot control.







Characteristics of spool type directional valve
Easy to manufacture and low cost.
Highly versatile. This structure is easy to design into a multi-position multi-way valve.
The requirements for air source purification are relatively high (the filtration precision is 10-20 μm, and compressed air containing oil mist lubrication should be used (unless it is a reversing valve without oil lubrication).







Classification by action:


Pilot type. The pilot type consists of a pilot valve and a main valve. It relies on the air pressure output by the pilot valve to push the main valve core to change directions. It is divided into internal pilot and external pilot.





Classified by sealing form:


Elastic seals, also known as soft seals, use various sealing rings made of synthetic rubber materials between each working chamber to ensure sealing. The manufacturing precision is low, and the requirements for the filtration precision of the working medium are low, no leakage, and sealing Damaged parts can be replaced and are affected by temperature;

Gap seal, also known as hard seal or metal surface seal, relies on the tiny gap between the valve core and the inner hole of the valve sleeve to maintain the seal. It has high manufacturing precision requirements, is sensitive to media, has micro-leakage, has low power, has a wide operating temperature range, and can operate at low pressure.







Classification according to the direction of air flow in the valve:
Reversible directional control valve: A control valve that can change the direction of air flow.
One-way directional control valve: A control valve in which air flow can only flow in one direction.







Classified by control number:
Single control type: means that one working position of the valve is obtained by the control signal, and the other working position is obtained by the reset method (spring return, air pressure reset or hybrid reset) after the control signal disappears.
Double control type: The finger valve has two control signals, and the two-position valve has a memory function.