Dehydration machine for pulp, sludges or similar fibrous materials

In a dehydration machine for pulp, sludges or similar fibrous material, composed of a lower sieve acting as a support sieve and of an upper sieve operating as a cover sieve, which sieves revolve about support and reversing rolls and are guided jointly through a wedging section arranged vertically or inclined at an acute angle and leading from the bottom to the top, with subsequent reversal of the sieve belts and of pairs of rolls through which is passed the material to be dehydrated coming from a material feed, the improvement wherein said wedging section is formed as a laterally closed support surface as a guide means and, followed directly by a reversal means provided with a lateral seal, and followed by a pressing section provided with a group of rolls comprising first and second pressing rolls arranged next to one another with a third pressing roll mounted above and in contact with said second pressing roll, and including a pressing system for the first pressing roll which selectively makes possible areal pressing from the first pressing roll with an ensuing pressing nip at the second and third pressing rolls, or two linear pressings, one at the first and second pressing rolls, the other at the second and third pressing rolls.