a pair of adjacent counter-rotating first and second shafts (20, 30) having their axes (X-X, X′-X′), disposed parallel to each other, said shafts (20, 30) each being provided externally with a box-like helical structure (21, 31), each of said helical structures (21, 31) winding in an opposite direction with respect to the helical structure of the other shaft;

a perforated walled filtering cage (4) enclosing said helical structures (21, 31) as an exact fit;

a loading hopper (10) for feeding the fibrous material to the press (1);

a discharge aperture (11) for the exit of the pressed material;

a collection sump (12) positioned externally to said filtering cage (4) to collect the liquid component of the pressed fibrous material,

wherein each of said box-like helical structures (21, 31) comprises a helix (22, 32), each of said helixes having a pitch (P) and a helical element (23, 33), said helical element (23, 33) forming a collection interspace (27, 37) in cooperation with the outer surface of the shaft (20, 30) and comprising at least one perforated surface (24, 34), said perforated surface (24, 34) having a length (L) along the axis (X-X, X′-X′) of the shaft (20, 30) which at every point is less than the pitch (P) of the helix (22, 32) creating an open channel abutting the helix (22, 32) of the first shaft, wherein the helix (32, 22) of the adjacent second shaft (30, 20) is received in the open channel.