Wolf-mouth shutter “EBL” is used for the extraction of sliding materials that come out of silos or hoppers without the aid of moving parts (i.e. atomized clay). The extractor is opened and closed thanks to an electro-pneumatic cylinder. Flow rate adjustment is achieved by adjusting the cylinder position. An electronic card manages the movements and allows to open for a predetermined time all the shutter in order to facilitate the discharge of any lumps of material (washing phase). The presence of sensors allows checking the correct operation of EBL.