Patent ID: 8870442

Claim:
A plasticating screw ( 1 ), comprising: a shank ( 2 ) extending along a rectilinear axis ( 3 ), a feeding region ( 4 ) for supplying a product to be plasticated, a plastication region ( 5 ) placed immediately downstream of the feeding region ( 4 ), relative to a main feeding direction (S) of the product along the axis ( 3 ) of the shank ( 2 ), at least one primary thread ( 7 ) extending in a helical development around the shank ( 2 ) at least in the plastication region ( 5 ), following a predetermined winding direction (V), at least one secondary thread ( 10 ) extending in a helical development around the shank ( 2 ) in the same way as said predetermined winding direction (V), in at least part of the plastication region ( 5 ), wherein said primary thread ( 7 ) and secondary thread ( 10 ) each have a varying pitch (p 1 , p 2 ); the pitch variation (p 2 ) of the secondary thread ( 10 ) being greater than the pitch variation (p 1 ) of the primary thread ( 7 ), wherein the pitch (p 1 ) of the primary thread ( 7 ), in at least part of the plastication region ( 5 ), increases at each turn carried out by the helical development of the primary thread ( 7 ) around the shank ( 2 ), away from the feeding region ( 4 ), wherein the pitch (p 2 ) of the secondary thread ( 10 ), in at least part of the plastication region ( 5 ), increases at each turn carried out by the helical development of the secondary thread ( 10 ) around the shank ( 2 ), away from the feeding region ( 4 ).