Fixed-angle keying piece for blades of axial fans

Abstract: Fixed-angle keying (1) piece for blades (3) of axial fans having an U-shaped cross section the internal surface of which perfectly fits the profile of the blade whilst the external surface of same has a plane side face which rests on a supporting plate (4), the said keying piece being obtained as continuous extruded section which is subsequently cut down in desired sizes.

Description: This invention relates to a fixed-angle keying piece for blades of axial fans, which can be obtained very easily and cheaply as continuous extruded section which is susequently cut down in desired sizes. The keying pieces according to the present invention can be easily substituted in an axial fan with another similar keying piece having a different setting angle. The angles of attack of the blades can therefore be changed by replacing the keying piece which, as said afore, can be made at a very cheap cost. The keying piece according to this invention has an U-shaped cross section the internal surface of which perfectly fits the profile of the blade to be inserted thereinto. The external surface of the U shape has a plane side face which is rested onto the external face of the supporting plate assembled to the hub of the axial fan and has an angle of inclination to the axis of U shape such that the blade gets the desired setting angle. The rounded bottom end of the U shape has a thickness that allows a slight bending thereof in order to make the insertion of the blade into the keying piece as well as the fastening of the blade easier, the fastening being obtained by clamping the sides of the keying piece tightly against the profile of the blade by means of bolts through holes made on assembling, said bolts also fastening the keying piece to the supporting plate. In the figure 1, a keying piece (1) completely assembled is shown (hatched cross section). The figure also shows a through bolt (2) for fastening the blade (3) within the keying piece according to the present invention and for fastening the keying piece onto the supporting plate (4). Obviously, the clamping bolts are at least two per keying piece, radially aligned (see fig. 2). In the figure 2, the keying piece with inserted blade, assembled to the supporting plate, is shown as view from above. In the figure 3 a keying piece having a double supporting base with clamping bolts 2, 2a side by side, is shown. The keying piece according to the present invention can be made of a metal soldable with an extruder, such as aluminum and its alloys. In the attaching brackets of the prior art USP 3.323.711 there is a main body portion (80) presenting a concave surface (82) said body portion having a reversely extending flange (84) which overlies the margin of the body portion. In these prior art attaching brackets the fixing bolts (or rivets) in positions 106, 108 (see fig. 4 and 6 of USP 3.323.711) press directly the blade: this latter is not clamped completely between two opposite sides of the brackets as in the device of the present invention. The device according to the present invention assures an identical setting angle to each blade: it is also very easy to be assembled. As said above, the keying piece according to the present invention has a very low manufacturing cost per piece, chiefly in case of manufacture on a large scale, because it can be manufactured as continuous extrusion.

Claims: A fixed-angle keying piece for a blade of an axial fan, obtained through extrusion as a continuous extruded article which is subsequently cut down into single keying pieces, in which keying piece the fastening is obtained by clamping the sides of the keying piece tightly against the profile of the blade by means of at least two bolts passing through holes made on assembling, said at least two bolts also fastening the keying piece to the supporting plate, and characterized in that it has an U-shaped cross section, the sides of which are substantially the same length, the internal surface of which perfectly fits the front part of the profile of the blade and the external surface of which has a plane side face which rests on an external face of a supporting plate assembled to a hub of the axial fan, and has an angle of inclination to the axis of U shape which corresponds to the desired setting angle of the blade, the rounded bottom end of the U-shaped keying piece having a thickness so as to allow a slight bending thereof for inserting the blade into the keying piece, and that said at least two bolts are the only fastening means required to hold the keying piece and blade in place, and that said at least two bolts are radially aligned with respect to said supporting plate.

Inventors: MOSIEWICZ ANTONIO, MOSIEWICZ, ANTONIO
Applicants: COFIMCO SRL, COFIMCO S.R.L.
Application year: 1988
Main classification: F04D29
IPC codes: F04D29