The cylinder with alveolus allows a separation in two parts of products with different lenght. It is composed by a rotating exetrnal screen on which there are the alveolus, the foreign body which is shorter than the wheat grain, enters the alveolus in order to be eliminated since the diameter of the alveolus is more little than the wheat grain.
These products shorter than the other, due to rotation, are tossed to a point where (by getting out from the alveolus). They are gathered in a vessel in which there is a screw for coaxial extraction with the cylinder.
The vessel is equipped with a device which regulates its inclination around the cylinder axe. So, the right inclination and the right choise of the diameter of alveolus and the rotation velocity of the screen. They allow to fix the point of separation of the the two parts.