According to the operation mode of the solenoid valve, the description of the solenoid valve is classified.

Solenoid valves are the most important components in pneumatic control components. They are flexible and diverse in structure. According to the manipulation mode, there are two types of direct acting and pilot head.
Direct motion
The direct-acting solenoid valve directly uses the electromagnetic force to directly push the valve stem (spool) to reverse. According to the control method of the spool reset, there are two types of single electronic control and double electronic control. The direct-acting solenoid valve is characterized by a simple and compact structure and a high commutation frequency. However, when used in an AC electromagnet, if the valve stem is stuck, there is a possibility of burning the coil. The reversing stroke of the valve stem is controlled by the stroke of the electromagnet suction stroke. Therefore it is only suitable for small valves.
The use of direct-acting double-electromagnetic solenoid valves should pay special attention to the fact that the electromagnets on both sides cannot be energized at the same time, otherwise the electromagnetic coil will be burned out. For this reason, an interlock circuit for preventing simultaneous energization is usually provided on the electric control circuit.
2. Pilot head
The pilot head type solenoid valve is composed of a small solenoid valve and a large air-controlled reversing valve, which is also called an electronically controlled reversing valve. The source of the pilot-type electromagnetic air control can be divided into two types: self-controlled (internal pilot) and other control (external pilot). A valve that directly uses the gas source of the main valve as a gas control signal is called a self-control solenoid valve. The self-control solenoid valve is easy to use, but there is a phenomenon of pressure drop at the moment of commutation, especially when the output flow is too large, which may cause the valve to fail. In order to ensure the reversing performance of the valve or to reduce the minimum working pressure of the valve, the valve that is externally supplied with the air pressure as the main valve control signal is called a control solenoid valve.
According to the principle of the configuration of the pilot head type solenoid valve, there are single electric control, double electric control, two, three, two, three, four and five and cut-off and sliding column structures, etc. The reversing valve is extremely versatile in construction and specifications.