Abstract: One or more vertically oriented cyclones are arranged for treating polluted water by oxygenizing the water and separating polluting particles contained therein. Each cyclone has a conically tapered open-ended elongated chamber having a top and a bottom. The top is exposed to the air and the bottom is submerged below the surface of the water being treated. The cyclone draws water in through a tangential inlet adjacent the bottom end of the cyclone. Upon entering the cyclone the water to be treated is rotationally moved in a spiral upward along the inside surface of the cyclone. A portion of the water being treated exits the top of the cyclone carrying separated polluting particles, while the majority of the water being treated exits the bottom of the cyclone with air entrapped therein.

Abstract: Method for the fabrication of cones of sheet material where the blank includes two curved edges that are circular and have the radius R and r respectively and a common center C. The blank further has two straight lateral edges which are angled in relation to the circular edges. An angle .alpha. between the radius, through a corner and a first straight edge is as great as an angle .beta. between the radius through a second straight edge. A frustum of a cone is obtained from the blank after rolling the cone such that the lateral edges have been united to make a joint that runs helically around the cone.