AP series air operated pinch valve, its patent name is drain pinch valve, and its working principle is as shown in the figure. There is an air chamber between the inner sleeve and the valve body. When the air in the air chamber is at normal pressure, the inner sleeve is in a natural state, and the valve is conductive; When the air chamber is filled with compressed air, the inner bushing is forced to extrude and deform, causing the valve to close; When the compressed air is removed, the inner bushing will recover to its natural state depending on its own elasticity or the pressure in the pipeline, and the valve will be open.