Grain-cleaning machine

A grain-cleaning machine for obtaining grains having a desired size which is greater than a lower value and less than or equal to an upper value, the grain-cleaning machine comprising

• a housing having an inlet opening,
• an arrangement of sieves disposed internally of the housing,
• a vibration system configured to oscillate the arrangement of sieves,
• the arrangement of sieves comprising
• at least two main sieve levels positioned overlapping each other and having an inclination to the horizontal from a high side to a low side, each main sieve level comprising a respective fine sieve followed by a respective grain sieve, wherein a respective fine-carrying channel is arranged below each fine sieve (141) in communication with at least one first residues outlet and below each grain sieve is disposed a respective grain carrying channel in communication with at least one grain outlet,
• at least one lower sieve level comprising a respective lower grain sieve, wherein a lower grain-carrying channel is arranged below the lower grain sieve in communication with at least one grain outlet,
• the at least one lower sieve level being positioned below the main sieve levels, and inclined to the horizontal from a high side to a low side, wherein the low side of each main sieve level is in communication with the high side of the at least one lower sieve level through a vertical passage and the low side of the lower sieve level is in communication with at least one second residues outlet,
• wherein each fine sieve has a first mesh provided with openings having an opening size which is equal to said lower value and wherein each grain sieve and each lower grain sieve have a second mesh provided with openings having an opening size which is equal to said upper value.