Abstract: Described herein is a blade unit for industrial fans, which comprises: a blade; and a tubular bar, fixed on which is said blade and which has a root portion configured for being engaged by means for connecting said bar to the rotor of a fan. The unit is characterized in that it comprises a further bar mounted within said first tubular bar so as to present a first portion axially constrained to said first bar, and a second portion that is, instead, able to slide with respect to said first bar, in a condition of sliding friction, following upon a deformation due to bending of said first bar.

Abstract: An axial fan comprises a hub and a plurality of blades extending from the hub; wherein each blade comprises a main blade portion and a secondary blade portion and the secondary blade portion has a leading edge adjacent to a leading edge of the main blade portion and forms a flap for the main blade portion; wherein a fluid passage is defined between the leading edge of the main blade portion and the leading edge of the secondary blade portion; wherein the main blade portion has a main chord and the secondary blade portion has a secondary chord; and wherein the main chord and the secondary chord form a relative attack angle comprised between 5° and 35°.

Abstract: A hollow extruded axial flow fan blade which includes two internal longitudinal reinforcing elements (ribs) perpendicular to the blade profile and in which are inserted through bolts for fastening the blade to a round supporting bar inserted longitudinally in the blade. The fastening bolts are completely internal to said blade being parallel to the plane of revolution of the blade while passing diametrally and perpendicularly through the round supporting bar.

Abstract: The present invention relates to fixed-angle keying pieces for blades of axial fans each having a U-shaped cross section, the internal surface of which perfectly fits the profile of the blade while the external surface of the same has a plane side face which rests on a supporting plate, the keying piece being obtained as a continuous extruded section which is subsequently cut to a desired size.

Abstract: According to the invention an increase of the effective displacement of air in an axial propeller, whose blades are not twisted, is achieved by applications of tab, substantially rigid, at the trailing edge of the blade, the maximum width of the tab being at the blade internal end.