Archimedes screw for use in conveyors, compactors and the like

1. An archimedes screw ( 1 ) for use rotating internally of a containing structure, the archimedes screw being located within the containing structure and comprising a shaft ( 2 ) and a helix ( 3 ), the helix ( 3 ) being coupled to the shaft ( 2 ), the shaft ( 2 ) comprising a central pin, wherein the archimedes screw ( 1 ) further comprises a plurality of sections which are threaded coaxially and solidly in rotation on the central pin, each of which plurality of sections exhibits different constructional and functional characteristics from others of the plurality of sections, wherein at least one of the sections ( 4 b ) located immediately upstream of a final section ( 4 a ) of the archimedes screw is made completely of metal, wherein at least some of the sections comprise a metal central sleeve ( 5 ) which couples with the shaft, which metal central sleeve ( 5 ) is sunk in a plastic material so that a portion of the helix ( 3 ) of the section is made of the plastic material in which the metal central sleeve ( 5 ) is sunk, wherein at least one of the first sections of the archimedes screw, located in proximity of a most upstream part of the archimedes screw, comprises a first portion of helix made of a softer plastic material than a plastic material with which a portion of helix of another section is made of, which first portion of helix is conformed such that, during a rotation of the screw, the first portion comes into contact with an internal wall of the containing structure.

2. The archimedes screw of claim 1 , wherein the first portion of helix has a greater diameter than a diameter of the internal wall of the containing structure in which the archimedes screw rotates.

3. The archimedes screw of claim 1 , wherein the final section ( 4 a ) of the archimedes screw, located on a terminal part of the archimedes screw, has a tip which is tip-shaped and directs, according to directions defined by a shape of the tip, the material transported by the helix of the archimedes screw.

4. The archimedes screw of claim 1 , wherein the tip has an at least partially diverging shape.

5. The archimedes screw of claim 1 , wherein the tip has an at least partially converging conical shape.

6. The archimedes screw of claim 5 , wherein the tip comprises a helix arranged about the converging conical part.

7. The archimedes screw of claim 3 , wherein the tip has an at least partially cylindrical shape.

8. The archimedes screw of claim 7 , wherein the tip comprises a diverging terminal part applied at an end of the cylindrical part.

9. The archimedes screw of claim 1 , wherein at least one of the first sections of the archimedes screw comprises flexible bristles positioned on an outermost surface of a portion of helix, which bristles come into contact with the internal wall of the containing structure in which the archimedes screw rotates.

10. The archimedes screw of claim 1 , wherein at least one of the first sections of the archimedes screw comprises protuberances, fashioned on an outermost surface of a portion of helix, which come into contact with the internal wall of the containing structure in which the archimedes screw rotates.

11. A method for compacting mixtures containing liquids, comprising the steps of: introducing the mixture in a sieve-conformed containing structure; and advancing the mixture along the sieve-conformed containing structure by means of an archimedes screw according to claim 1 .

12. A method according to claim 11 , wherein the step of advancing the mixture along the sieve-conformed containing structure is performed by means of said at least one of the first sections of the archimedes screw.