A device includes a rotary portion, which is mounted so as to rotate on a support structure around a rotation axis (X-X) between an angularly moved away condition and an angularly moved close condition relative to an outlet mouth. A shutter portion pivots relative to the rotary portion around a pivoting axis (Y-Y) lying on a plane that is transverse relative to the rotation axis (X-X). An actuating apparatus moves the rotary portion between the moved away condition and the moved close condition. The shutter portion is suited to pivot around the pivoting axis (Y-Y) from an open position, in which the shutter portion is spaced apart from the outlet mouth, to a closed position, in which the shutter portion lies against the outlet mouth, when the rotary portion shifts from the moved away condition to the moved close condition.