Electromagnetic what are the different types of working principle of pneumatic valve

date back the history of the pneumatic valve, electromagnetic pneumatic valve at home and abroad so far, in principle can be divided into three categories: ( I. e. , straight acting, direct acting and pilot operated step by step, and from the pneumatic valve structure and material of different and the difference on the principle is divided into six branches small class ( Diaphragm structure, membrane structure step by step, the forerunner of moving diaphragm structure, straight moving piston structure, step by step the piston structure, the guide piston structure.
　　( A principle, direct acting solenoid pneumatic valve: electricity, electromagnetic coil to produce electromagnetic force to shut off pneumatic seat, pneumatic valve open; Power, the electromagnetic force disappears, the spring force closure pressure in the pneumatic seat, pneumatic valve shut off. Features: in a vacuum, negative pressure, can work properly when the zero pressure, but the general size does not exceed the mm.
　　( Second, step by step direct acting solenoid pneumatic valve principle: it is a direct acting and pilot operated the principle of combining when the inlet and outlet pressure differential or less. Mpa, when electrified, the lead directly to the electromagnetic force small pneumatic valve and main valve closed in turn lift, pneumatic valve to open. When the inlet and outlet pressure difference & gt; 。 Mpa, when electricity, electromagnetic force to open the first pilot small pneumatic valve, the main pneumatic valve inferior vena pressure rising, the cavity pressure drop, which using the differential the main pneumatic valve opened up; Power outages, the forerunner of pneumatic valve and the main pneumatic valve using the spring force or medium pressure push off, move down, to close the pneumatic valve. Features: on the zero differential pressure or vacuum and high pressure, can work reliably, but power is larger, for vertical installation.
　　( Three principle, guiding type solenoid pneumatic valve: electricity, electromagnetic force open the pilot hole, the chamber pressure drops rapidly, in closed form around the high low differential pressure, promote close up, pneumatic valve open; Power off, the spring force to close the guide hole, inlet pressure through by-pass hole quickly into the chamber in closing using pneumatic valves forms around the high pressure difference, promote the close a move down, close the pneumatic valve. Features: high fluid pressure upper limit, but the fluid pressure differential conditions must be met.