AUTOMATIC DRAIN VALVE FOR PNEUMATIC PLANTS

Drain valve (1) for tanks of pneumatic systems, comprising: a valve body (2) defining a cavity, and comprising: an inlet (4), whereupon compressed air contained in the tank is intended to act; an outlet (6), adapted to be put in communication with the outside of the tank; a chamber (3) intended to be filled with air coming from the inlet (4), and wherein such air is intended to exit the chamber (3) through said outlet (6). There is a shutter device comprising: a first piston (8) adapted to slide in said cavity and adapted to selectively close said outlet (6), the first piston (8) being subject to the pressure of the air coming from the inlet (4); a second piston (9) adapted to slide in said cavity and subject to the pressure of the air coming from the inlet (4). The first and second pistons (8, 9) are configured to take: a closed configuration, in which they prevent air from flowing to and from the chamber (3); an intake configuration, in which air can flow into the chamber (3) from the inlet (4), and air is prevented from flowing from the chamber (3) through the outlet (6); an ejection configuration, in which air is prevented from flowing into the chamber (3) from the inlet (4), and air can flow from the chamber (3) through the outlet (6).