Select pneumatic ball valve
The valve is located at the core of the pneumatic control system, and there are various types of directional control valve (DCV) and ratio control valve for selection. Undoubtedly, directional control valves are commonly used to control the direction of compressed air (or other appropriate fluids), for example, to determine whether the stroke of the cylinder is forward or backward. The valve is identified by the number of its main connections and possible switching positions. For example, a "3/2" valve corresponds to three ports and two switching positions. The mechanical design and functional design of the directional control valve are different from those of the directional control valve. DCV design types include: plug (spherical plug, flat plug), valve shaft, sliding block and rotary sliding block. Different design methods and materials may be applied even in the same type. For example, SpoolValve body may have a seal ring along its valve shaft or replace the seal. The design characteristics affect the service life, flow rate, actuator, driving force, size and price of the valve. When the directional valve is used to perform all switching operations, the proportional valve (PV) regulates the pressure and flow rate. The main feature of the proportional valve is to convert the input signal into a specific output signal. Proportional valves usually include two components - a pilot control and a valve unit. The pilot control consists of two 2/2-way pilot valves or a solenoid, and includes an electronic circuit for evaluation. The valve unit contains only integrated pneumatic functions. (such as 0)~10V voltage or 0~20mA current) acts on the control block connector. Then, the voltage or current is corresponding to the controlled pressure. The actual pressure at the work port is measured by an integrated pressure sensor and sent to the evaluation electronic circuit, which compares the actual pressure with the expected pressure. According to the pressure deviation, the electronic circuit unit immediately switches the operating positions of the pilot valve and the main valve until the expected pressure is reached. For "standard" and directional control valve, there can only be one switch position, but the proportional directional control valve can also have an intermediate position. This means that, for example, except for the "open" or "closed" end point positions, the intermediate position such as "slightly open" is possible. The actuator used to switch the working position is a proportional electromagnetic coil. When the electromagnetic coil is excited by the electronic circuit, the coil voltage will change accordingly, and the position of the control piston will change according to the changing electromagnetic field intensity. Therefore, with the help of the control piston, each air passage is opened or closed at the same time. This not only starts the open loop or closed loop control of the moving direction of the cylinder, but also controls the moving speed of the cylinder. Therefore, the valve has throttling function, and the switching frequency is about 100Hz. This type of valve can achieve quite high dynamic performance. Proportional valve has a wide range of applications. For example, when materials are uncoiled, the application of proportional valve can maintain a constant pneumatic tension during the uncoiling process. The proportional directional control valve has further application in cylinder positioning. In this case, the cylinder is equipped with a displacement encoder, which provides the feedback signal of the actual position of the piston. The control valve controls the volume flow into or out of the cylinder to obtain a specific position.
