Adjustment during the development process of pneumatic valve in the form of classification, 3)

a, concentric butterfly pneumatic butterfly valve of the pneumatic valve to the structure characteristics of pneumatic valve stem axis, the butterfly plate center, center of ontology in the same position. Simple structure, convenient manufacturing. Common line with rubber butterfly pneumatic valve which belongs to and so on. Defect is due to the butterfly plate remain the state of extrusion, scraping and pneumatic valve seat, is apart from the big, fast wear. To overcome the extrusion, scratches, ensure the sealing performance, pneumatic seat basically use the elastic material such as rubber or ptfe, but also on the use is limited by temperature, which is why people traditionally butterfly pneumatic valve is not the cause of the high temperature resistant. Second, single eccentric butterfly pneumatic valve to solve the problem of concentric butterfly butterfly plate of pneumatic valve and pneumatic seat extrusion problems, creating a single eccentric butterfly pneumatic valve, the structure characteristics of pneumatic valve rod axis deviation from the center of butterfly plate, so that the butterfly plate up and down side is no longer a rotary axis, scattered, reduced the butterfly plate side and up and down pneumatic seat excessive compression. But as a result of single eccentric structure butterfly plate in the process of the whole pneumatic valve switch with pneumatic seat scratches phenomenon did not disappear, on the application scope and concentric butterfly pneumatic valve is the same, is not much. Three, double eccentric butterfly pneumatic valve in single eccentric butterfly valve on the basis of the further improvement of molding is currently the most widely used double eccentric butterfly pneumatic valve. Its structure characteristics is in the center of the pneumatic valve stem axis deviation both disc and deviating from the center of ontology. The effect of the double eccentric butterfly plate can immediately after pneumatic valves are open from pneumatic valve seat, greatly eliminates the butterfly plate and pneumatic seat unnecessary phenomenon of excessive extrusion, scratches, reduce the opening distance, reduces the abrasion resistance, improve the pneumatic seat life. Scraping slash, but also makes the double eccentric butterfly pneumatic valve can also use a metal pneumatic valve seat, improves the butterfly pneumatic valve in the field of high temperature applications. But because its sealing principle position belongs to the sealing structure, namely the butterfly plate and pneumatic valve seat sealing surface for the line contact, through the butterfly plate extrusion pneumatic seat sealing effect caused by the elastic deformation, therefore the high requirement of closed position ( Especially the metal pneumatic valve seat, low bearing capacity, which is why people traditionally butterfly pneumatic valve leakage in high pressure resistance, no major reasons. Four, three eccentric butterfly pneumatic valve to high temperature resistant, hard seal must be used, but the large amount of leakage; To zero leakage, must use the soft seal, but it is not resistant to high temperature. In order to overcome the double eccentric butterfly pneumatic valve this contradiction, and for the third eccentric butterfly pneumatic valve. The structure characteristics of the double eccentric pneumatic valve rod eccentric axis position at the same time, make the butterfly plate type sealing face of the cone axis deflection in the cylindrical axis of ontology, that is to say, after the third eccentric, butterfly plate sealing section is no longer true circle, but the ellipse, and so the seal face shape asymmetry, tilt to the center line of the ontology, on the other side is parallel to the centerline of ontology. The biggest characteristic of the third eccentric is fundamentally changed the seal structure and seal position is no longer, but the torque seal, namely not rely on the elastic deformation of pneumatic valve seat, but entirely on pneumatic seat contact pressure to achieve sealing effect, thus solve the metal pneumatic seat the problem of zero leakage, and because of the contact pressure and the medium is proportional to the pressure, resistance to high pressure high temperature is solved.