Rotor for a centrifugal fan, particularly for the forced circulation of air in convention cooking ovens

Abstract

A centrifugal fan rotor includes radial blades extending from a disc support connectable to a hub for connection to the rotor's shaft. The blades are produced by stamping metal sheet, each having a corresponding blade surface and opposite attachment projection to the disc support. The rotor includes at least a first group of the blades in which each blade of the first group is provided with respective attachment projections upstream of the corresponding blade surface with respect to a direction of rotation of the rotor, and at least a second separate group of the plurality of blades in which each blade is provided with respective attachment projections arranged downstream of the corresponding blade surface with respect to rotation direction, such that each blade of the first and second groups are mirror-symmetrical to each other with respect to a radial center plane of symmetry between the blades extending through rotation axis.

1 . A rotor for a centrifugal fan comprising a plurality of radial blades extending from a disc support which is configured to be connected to a hub for connection to a rotary shaft of the rotor, said blades being of the type produced by stamping metal sheet, in which a planar sheet of substantially rectangular shape is provided, during stamping, with a sequence of cuts over a thickness of the metal sheet, each cut extending between opposite longitudinal sides of the metal sheet, with the exception of opposite smaller end zones where respective attachment projections of each blade with respect to the metal sheet plane continue to be defined, and in which successive folding of each blade by approximately 90° with respect to the metal sheet plane forms a series of blades, and in which an assembly of said series of blades on the rotor involves folding of the metal sheet carrying the blading into a cylindrical profile, such that the metal sheet is wound about the disc support in order to be locked along a circular profile of the disc support by means of caulking which locks the attachment projections of the blades, extending from the same side of the series, on the disc support, a support ring being provided, axially opposite the disc support, for fixing by caulking of the attachment projections of the axially opposite blades extending from the opposite side of the series, wherein the rotor further comprises at least a first group of said plurality of blades in which each blade of said first group is provided with respective attachment projections arranged upstream of the corresponding blade surface with respect to a direction of rotation of the rotor, and at least a second separate group of said plurality of blades in which each blade is provided with respective attachment projections arranged downstream of the corresponding blade surface with respect to said direction of rotation, such that each blade of the first group is mirror-symmetrical to each blade of the second group with respect to a radial center plane of symmetry between the blades extending through the axis of rotation of the rotor. 
     
     
         2 . A rotor according to  claim 1 , wherein the first and the second group of blades together form the whole blading of the rotor and the first group comprises 25% of the overall number of blades of the rotor. 
     
     
         3 . A rotor according to  claim 2 , wherein, where N indicates the overall number of blades of the rotor, the first and second group of blades each comprise a number of blades N′ having the following values:
 N′=N/2 if N is an even number, or 
 N′=(N/2)+/−0.5 if N is an odd number. 
 
     
     
         4 . A rotor according to  claim 3 , wherein each of the first and second groups is formed by blades adjacent to one another in the series of blades so as to involve a semi-cylindrical portion of the overall cylindrical extent of the rotor. 
     
     
         5 . A rotor according to  claim 4 , wherein each of the first and second groups of blades is formed from a respective and separate metal sheet for stamping of the blades of the corresponding group, each metal sheet being configured to act on a semi-circumferential section of the circular profile of the disc support to which the series of blades is fixed. 
     
     
         6 . A rotor according to  claim 3 , wherein the series of blades is formed by a sequence of blades in which a blade of the first group alternates with a blade of the second group, all the blading of the rotor being formed on a single metal sheet stamped and folded into a cylindrical shape for locking on the disc support. 
     
     
         7 . A rotor according to  claim 1 , configured as a rotor with radial blading.