WO2018087586A1

WO2018087586A1 - A centrifugal fan for high temperatures

Info

Publication number: WO2018087586A1
Application number: PCT/IB2016/056841
Authority: WO
Inventors: Marco Forti
Original assignee: Tecnome' S.R.L.
Priority date: 2016-11-14
Filing date: 2016-11-14
Publication date: 2018-05-17

Abstract

A centrifugal fan (1) for high temperatures comprising at least one shaft (2) having an axis of rotation and a fan wheel (3) mounted on the shaft (2), wherein the fan wheel (3) comprises a plurality of blades (53. 54) and at least two constraining elements (10, 11, 18) which substantially at least partly contain between them the blades (53. 54), wherein each blade (53. 54) is connected to at least one constraining element (10, 11, 18) by interlocking connection and wherein the fan wheel (3) is connected to the shaft (2) by interlocking connection.

Description

A CENTRIFUGAL FAN FOR HIGH TEMPERATURES

DESCRIPTION

This invention relates to a centrifugal fan for high temperatures. This invention is intended, in particular, for centrifugal fans used in combustion furnaces for conveying combustion fumes towards the chimney .

Hereinafter explicit reference will be made to that family of fans, although this invention may in any case also apply to fans intended for other uses.

In general, like all fans, even centrifugal fans for high temperatures comprise a rotary shaft on which a fan wheel is fitted, the fan wheel being equipped with a plurality of blades. The various parts are connected to each other either by welding or using assembly means, for example, solid rivets and blind rivets. In order to increase their resistance, to high temperatures and to the consequent mechanical stresses, as well as to chemical attack by the combustion fumes, fans for high temperatures are built using materials that withstand high temperatures, for example special steels .

However, this prior art technology has several disadvantages.

In particular, prior art centrifugal fans for high temperatures on one hand have a range of operating temperatures which are well below the temperatures that can be reached by the combustion fumes, since at higher temperatures the resulting mechanical deformations are such that they prevent fan operation. On the other hand, they are subject to deterioration or breakage after a relatively short period of use, again due to the mechanical stresses to which they are subjected during operation.

In this context the technical purpose which forms the basis of this invention is to provide a centrifugal fan for high temperatures which overcomes the above-mentioned disadvantages.

In particular, the technical purpose of this invention is to provide a centrifugal fan for high temperatures that as a whole is more resistant to high temperatures than the prior art centrifugal fans for high temperatures. A further technical purpose of this invention is to provide a centrifugal fan for high temperatures that is easier to make, and therefore has a lower production cost, compared with prior art centrifugal fans for high temperatures.

The technical purpose specified and the aims indicated are substantially achieved by a centrifugal fan for high temperatures as described in the appended claims.

Further features and the advantages of this invention are more apparent in the detailed description of a preferred, non-limiting embodiment of a centrifugal fan for high temperatures illustrated in the accompanying drawings, in which:

- Figure 1 is an exploded axonometric view of a centrifugal fan for high temperatures made according to this invention;

- Figure 2 is an assembled axonometric view of the fan of Figure 1;

- Figure 3 is a side view of the fan of Figure 2;

- Figure 4 is a cross-section of the fan of Figure 3 according to line IV - IV;

- Figure 5 is an enlarged detail from Figure 4;

- Figure 6 is a front view seen from the right of the fan of Figure 3;

- Figure 7 is a view of the fan of Figure 3 in section according to line VII - VII of Figure 6;

- Figure 8 is an enlarged detail from Figure 7;

- Figure 9 is an enlarged detail from Figure 2;

- Figure 10 shows the detail of Figure 9 before a step of plastic deformation of a projecting element;

- Figure 11 is an axial section of the fan of Figure 2 according to line XI - XI of Figure 6; and

- Figure 12 is an enlarged detail from Figure 11.

With reference to the above-mentioned figures, the numeral 1 denotes in its entirety a centrifugal fan for high temperatures according to this invention.

The centrifugal fan 1 for high temperatures according to this invention comprises at least one shaft 2 having an axis of rotation and a fan wheel 3 mounted on the shaft 2. The fan wheel 3 comprises a plurality of blades 53, 54 and at least two constraining elements 10, 11, 18 which substantially at least partly contain between them the blades 53 , 54 . Each blade 53 , 54 is connected to at least one constraining element 10, 11, 18 by interlocking connection and the fan wheel 3 is connected to the shaft 2 by interlocking connection. As will be more apparent in the detailed description that follows, in the preferred embodiment, also illustrated in the accompanying figures, the interlocking connection between the blades 53 , 54 and the constraining elements 10, 11, 18 is made in such a way as to increase its effectiveness under the effect of the centrifugal force that acts on the fan wheel 3 during operation.

In particular, in the embodiment illustrated in these figures, the fan wheel 3 is constituted of parts which are connected to each other exclusively by interlocking connections. Moreover, advantageously, the fan wheel 3 is connected to the shaft 2 exclusively by interlocking connection.

Such interlocking connections, both of the blades 53 , 54 to the constraining elements 10, 11, 18, and of the fan wheel 3 to the shaft 2 , if used simultaneously, allows a fan 1 to be made which is free of classic assembly means, such as solid rivets and blind rivets, and/or welds. As illustrated in the accompanying figures, which show the preferred embodiment of this invention, both the blades 53 , 54 and the constraining elements 10, 11, 18 of the fan 1 extend mainly flat, and each blade 53 , 54 is positioned substantially perpendicular to the constraining elements 10, 11, 18. Advantageously, the blades 53 , 54 are substantially flat according to a main plane of extension and may have any shape depending on requirements. Also, advantageously, the blades 53 , 54 are made of cut flat sheet metal. Moreover, it is also possible that one or more blades 53 , 54 may have a shape and size different to the other blades 53 , 54 present in the fan wheel 3 . In the preferred embodiment illustrated in the accompanying figures, the blades 53 , 54 comprise a first portion 6 closest to the shaft 2 and narrower than a second portion 7 furthest from the shaft 2 . Those first portions 6 are partly contained between the at least two constraining elements 10, 11, 18. In the embodiment illustrated, apart from several projecting portions described in more detail below, the overall shape of the blades 53, 54 is mainly symmetrical (relative to a plane perpendicular to the axis of rotation of the fan wheel 3) and T-shaped.

Advantageously, the constraining elements 10, 11, 18 may adopt any substantially flat shape and each constraining element 10, 11, 18 may have a shape and size different to those of the other constraining elements 10, 11, 18. However, in the preferred embodiment, the constraining elements 10, 11, 18 are disk-shaped and, if necessary, pierced at the centre.

In the embodiment illustrated in the accompanying figures, each blade 53, 54 of the fan 1 according to this invention comprises at least one hooking element 12, 13, 19 and, for each hooking element 12, 13, 19 at least one constraining element 10, 11, 18 comprises a corresponding counter-hooking element 14, 15, 20, in such a way that each blade 53, 54 is connected to the at least one constraining element 10, 11, 18 by interlocking connection of the hooking element 12, 13, 19 with the corresponding counter-hooking element 14, 15, 20. Advantageously, said hooking element 12, 13, 19 and said counter-hooking element 14, 15, 20 will complement each other and be at least partly shaped to match one another, in order to guarantee a stable interlocking connection.

Although it is also possible that the fan wheel 3 may comprise a first group of blades 53, 54 connected to only one of the at least two constraining elements 10, 11, 18 and a second group of blades 53, 54 connected only to the other of the at least two constraining elements 10, 11, 18, in the preferred embodiment each blade 53, 54 is connected to both of the at least two constraining elements 10, 11, 18. In particular, in the embodiment illustrated in the accompanying figures, the at least two constraining elements 10, 11, 18 comprise a first constraining element 10 and a second constraining element 11, they extend mainly flat and are substantially parallel to each other. Moreover, each blade 53, 54 comprises at least one first hooking element 12 and at least one second hooking element 13, whilst the first constraining element 10 comprises at least one first counter-hooking element 14 for each blade 53, 54 and the second constraining element 11 comprises at least one second counter-hooking element 15 for each blade 53, 54. In this way, each blade 53, 54 is connected to the first constraining element 10 by interlocking connection of the first hooking element 12 to the first counter-hooking element 14 and is connected to the second constraining element 11 by interlocking connection of the second hooking element 13 to the second counter- hooking element 15.

Advantageously, in other embodiments the fan wheel 3 may comprise groups of blades 53, 54 each having a different number of hooking elements 12, 13, 19 per blade 53, 54. Consequently, each constraining element 10, 11, 18 may have a number of counter-hooking elements 14, 15, 20 different compared to another constraining element 10, 11, 18, but the distribution of the counter-hooking elements 14, 15, 20 in the constraining elements 10, 11, 18 must be such that a respective counter-hooking element 14, 15, 20 corresponds to each hooking element 12, 13, 19.

In the embodiment illustrated in the accompanying figures, the at least two constraining elements 10, 11, 18 are two substantially flat disks that are parallel to each other. In this case, a first disk (which in the following description will be labelled "10") will constitute the first constraining element 10 comprising a plurality of first counter-hooking elements 14, and a second disk (which in the following description will be labelled "ll") will constitute the second constraining element 11 comprising a plurality of second counter-hooking elements 15. Therefore, the first portion 6 of each blade 53, 54 is partly contained between the first disk 10 and the second disk 11 and each blade 53, 54 is simultaneously connected to the first disk 10 by interlocking connection of the first hooking element 12 to the corresponding first counter-hooking element 14, and to the second disk 11 by interlocking connection of the second hooking element 13 to the corresponding second counter-hooking element 15.

Advantageously, the fan 1 according to this invention also comprises at least one third constraining element 18 extending mainly flat, which is substantially parallel to the second constraining element 11 and which is positioned adjacent to but spaced from the second constraining element 11. Moreover, at least one group of blades 53, 54 comprises at least one third hooking element 19, the third constraining element 18 comprising at least one corresponding third counter-hooking element 20 for each third hooking element 19, and the blades 53, 54 of said group are fixed to the third constraining element 18 by interlocking connection of each third hooking element 19 to the corresponding third counter-hooking element 20.

That third constraining element 18, as well as increasing the stability of the blades 53, 54 relative to one another and of the fan wheel 3 as a whole, being positioned on the suction side of the fan 1 is designed to protect against high temperatures, by acting as a thermal shield, first the shaft 2 and, second, at least partly, the second constraining element 11 and the second hooking elements 13, connected by interlocking connection to the corresponding second counter-hooking elements 15 located on the second constraining element 11.

Also, advantageously, the second constraining element 11 comprises at least one open portion for allowing all of the third hooking elements 19 present to pass beyond the second constraining element 11 and to reach the corresponding third counter-hooking elements 20 made on the third constraining element 18. In particular, in the embodiment illustrated the at least one open portion is constituted of a hole 22 for each third hooking element 19 and has a shape and a size which allows the corresponding third hooking element 19 to be inserted in the hole 22 and to pass beyond the second hooking element 11. In the embodiment illustrated in the accompanying figures, the second disk 11 comprises a plurality of holes 22, in particular six holes 22, since there are six blades 53, 54 each comprising a third hooking element 19.

In the embodiment illustrated in the accompanying figures, the third constraining element 18 is a third disk (which in the following description is labelled "18") having a smaller diameter than the second disk 11, although it could have any shape that is substantially flat and any size. Moreover, that third constraining element 18 comprises as many third counter-hooking elements 20 as the total number of third hooking elements 19 present on the blades 53, 54 of the fan wheel 3.

Advantageously, the fan wheel 3 may comprise different types of blades 53, 54 which differ according to the number and type of hooking elements 12, 13, 19 present. In the preferred embodiment illustrated in the figures, the fan wheel 3 comprises a plurality of first blades 53, each comprising only the first hooking element 12 and the second hooking element 13, and a plurality of second blades

54, each also comprising the third hooking element 19. Each blade 53, 54 comprises on the first portion 6 two diametrically opposed edges, a first edge 24 resting on the first constraining element 10 and a second edge 25 resting on the second constraining element 11. Each first blade 53 comprises the first hooking element 12 on the first edge 24 and the second hooking element 13 on the second edge 25. Each second blade 54 comprises the first hooking element 12 on the first on the first edge 24 and both the second hooking element 13 and the third hooking element 19 on the second edge 25. The first hooking elements 12 belonging to the first blades 53 and the first hooking elements 12 belonging to the second blades 54 may differ from each other in their shape, size and position on the first edge 24. Similarly, the second hooking elements 13 and the third hooking elements 19, belonging to the first blades 53 or to the second blades 54, may differ from each other in their shape, size and position on the second edge 25.

In a corresponding way, the first counter-hooking elements 14 corresponding to the first hooking elements 12 of the first blades 53 and the first counter-hooking elements 14 corresponding to the first hooking elements 12 of the second blades 54 may differ from each other in their shape, size and position on the constraining element 10, 11, 18. Similarly, the second counter-hooking elements 15 and the third counter-hooking elements 20, corresponding to the related hooking elements 12, 13, 19 of the first blades 53 or of the second blades 54, may differ from each other in their shape, size and position on the constraining element 10, 11, 18.

In the preferred embodiment illustrated in the figures, the hooking elements 12, 13, 19 comprise at least one projecting portion 26 that extends cantilever-style from the related blade 53, 54 parallel to the axis of rotation of the shaft 2. Moreover, the at least one projecting portion 26 comprises on a part of furthest from the axis of rotation of the shaft 2 a projection 27 extending radially outwards relative to the axis of rotation of the shaft 2.

The at least one projecting portion 26 extends, parallel to the axis of rotation, from a zone of it connected to the rest of the blade 53, 54 until it is partly beyond the corresponding counter-hooking element 14, 15, 20, and the related projection 27 is positioned on the opposite side of the counter-hooking element 14, 15, 20 to the zone connecting the projecting portion 26 to the rest of the blade 53, 54 and is superposed on the counter-hooking element 14, 15, 20. In the preferred embodiment illustrated in the accompanying figures, each counter-hooking element 14, 15, 20 comprises an elongate through opening made through the constraining element 10, 11, 18 and a supporting portion 29 of the constraining element 10, 11, 18 surrounding said elongate through opening and on which the projection 27 of the projecting portion 26 of the hooking element 12, 13, 19 is superposed and coupled. The elongate through opening is also advantageously positioned in such a way that it mainly extends along a line that is radial relative to the axis of rotation .

In fact, advantageously, in the interlocking connection between the hooking element 12, 13, 19 and the corresponding counter-hooking element 14, 15, 20, the projecting portion 26 is inserted in the through opening and the projection 27 is resting on the supporting portion 29.

In the preferred embodiment illustrated in the figures, the fan wheel 3 comprises six first blades 53, six second blades 54, the first disk 10, which in turn comprises twelve first counter-hooking elements 14, the second disk 11, which in turn comprises twelve second counter-hooking elements 15 and six holes 22, and the third disk 18 which comprises six third counter-hooking elements 20. Moreover, in the second blades 54, the third hooking element 19 has the projecting portion 26 extending cantilever-style parallel to the axis of rotation for a length greater than the projecting portion 26 of the second hooking element 13, since the projecting portion 26 of the third hooking element 19 in order to make an interlocking connection with the corresponding third counter-hooking element 20 must also pass through the corresponding hole 22 present on the second disk 11.

Advantageously, the projecting portion 26 and the projection 27 present on the projecting portion 26 may have any shape and size suitable for allowing an effective and stable interlocking connection to the corresponding elongate through opening and the related supporting portion 29 included in the counter-hooking element 14, 15, 20. Consequently, the elongate through opening and the supporting portion 29 may have any shape and size, provided that these allow a suitable interlocking connection to the corresponding projecting portion 26 and related projection 27. In the preferred embodiment illustrated in the figures, the elongate through opening of each counter-hooking element 14, 15, 20 is a slot 30 with a substantially rectangular shape and comprises a first short side 31 furthest from the axis of rotation, and a second short side 32 closest to the axis of rotation. The second short side 32 may be closed or open.

In the preferred embodiment illustrated in the figures, each projecting portion 26 is substantially flat (coplanar with the rest of the blade 53, 54) and extends cantilever-style from the related edge of the first portion 6 of the blade 53, 54, parallel to the axis of rotation of the shaft 2. Moreover, the projecting portion 26 comprises on its part that is radially furthest from the axis of rotation a first flank 33 extending substantially parallel to the axis of rotation from which the projection 27 extends cantilever- style .

In the preferred embodiment illustrated in the figures, the first flank 33 is resting on the first short side 31 of the slot 30 and the projection 27 is positioned on the opposite side of the counter- hooking element 14, 15, 20 (and therefore of the constraining element 10, 11, 18) to the first edge 24 or the second edge 25 of the related first portion 6 of the blade 53, 54, and is resting on the part of the supporting portion 29 positioned at the first short side 31 of the slot 30. Moreover, in the preferred embodiment illustrated in the accompanying figures, the projecting portion 26 of the second hooking element 13 also comprises a second flank 34 extending substantially parallel to the third disk 18 and which is resting on the self-same third disk 18. This allows the third disk 18 to be locked in a position adjacent to but spaced at a distance from the second disk 11.

In the preferred embodiment, the shaft 2 of the fan 1 comprises a tubular body 35. Moreover, the shaft 2 comprises a first end 36 and a second end 37, and the fan wheel 3 is mounted on the shaft 2 at the first end 36. The first constraining element 10 comprises a central hole 38 through which the shaft 2 is inserted, whilst the second constraining element 11 comprises a solid central part 39 positioned at the first end 36 of the shaft 2 but spaced from it to allow fluid communication between the inside of the tubular body 35 and an empty space 40 present between the various blades 53, 54. This embodiment allows cold air to be sucked through the tubular body 35, thanks to the fact that during operation a pressure drop is created at the empty space 40 between the blades 53, 54 and between the first end 36 and the second disk 11. That cold air allows cooling both of the shaft 2 and of the second disk 11. However, in other embodiments cooling may even be achieved using other methods. The central hole 38 of the first constraining element 10 may have any shape, but advantageously it is shaped to match the shaft 2. Similarly, the shaft 2 may have any shape, just as the tubular body 35 may have any cross-section. In the embodiment illustrated in the accompanying figures, the solid central part 39 of the second constraining element 11 is constituted of the central part of the second disk 11.

Moreover, in the embodiment illustrated in the accompanying figures, each blade 53, 54 comprises an inner edge 41 parallel to the axis of rotation of the shaft 2 which is substantially resting on the shaft 2. Advantageously, at least one blade 53, 54 comprises on the inner edge 41 a step 42 positioned in contact against the first end 36 of the shaft 2, in order to guarantee correct axial positioning of the fan wheel 3 relative to the axis of rotation. In the embodiment illustrated in the accompanying figures, each second blade 54 comprises the above-mentioned step 42 on the inner edge 41.

Furthermore, in the preferred embodiment, the fan wheel 3 and the shaft 2 comprise, one, a plastically deformed projecting element 43 and, the other, a contact element, and the interlocking connection between the fan wheel 3 and the shaft 2 is obtained at least by coupling the plastically deformed projecting element 43 and the contact element. In particular, the projecting element 43 is advantageously made in at least one blade 53, 54, and the shaft 2 also externally comprises a first channel 45 which constitutes the contact element and which extends annularly around the axis of rotation of the shaft 2. The plastically deformed projecting element 43 is inserted in the first channel 45. That insertion prevents the fan wheel 3 from moving parallel to the axis of rotation of the shaft 2 at least away from the second end 37, as described in more detail below.

In the embodiment illustrated in the accompanying figures, only the six second blades 54 are provided with the plastically deformed projecting element 43. In particular, each of them comprises, at the end of the inner edge 41 furthest from the first end 36 of the shaft 2, a tab (which in the following description will be labelled "43") which constitutes the projecting element 43. Moreover, the first channel 45 comprises two sides, a closed first side 47 facing the second end 37 of the shaft 2 and a second side 48 facing the first end 36 of the shaft 2.

In the preferred embodiment, the shaft 2 externally comprises at least one second channel 49 extending from the first end 36 substantially parallel to the axis of rotation of the shaft 2, and the inner edge 41 of at least one blade 53, 54 is substantially shaped to match the at least one second channel 49 and is inserted in the second channel 49. Advantageously, the shaft 2 externally comprises a plurality of second channels 49 extending from the first end 36 substantially parallel to the axis of rotation of the shaft 2, and the inner edges 41 of a plurality of blades 53, 54 are substantially shaped to match said plurality of second channels 49 and are inserted in the second channels 49. In the embodiment illustrated in the accompanying figures, all of the blades 53, 54 have the inner edge 41 inserted in a corresponding second channel 49.

Furthermore, in the preferred embodiment, at least one blade 53, 54 having the inner edge 41 inserted in a second channel 49 also comprises the plastically deformed projecting element 43 inserted in the first channel 45. In the embodiment illustrated in the accompanying figures, all of second blades 54 have the plastically deformed projecting element 43 inserted in the first channel 45. In the embodiment illustrated in the accompanying figures, the shaft 2 comprises twelve second channels 49 extending from the first end 36 towards the second end 37. Each second channel 49 comprises a first open mouth 50 near the first end 36 of the shaft 2, allowing, during fan 1 assembly, insertion of a blade 53, 54 with blade sliding along an axial line, and a second open mouth 51 leading to the first channel 45, and which, during fan 1 assembly, allows feeding of the blades 53, 54 which also comprise the projecting element 43 until the projecting element 43, not yet plastically deformed, has been positioned in the first channel 45.

In fact, during fan 1 assembly, the inner edge 41 of each second blade 53, 54 which also comprises the tab 43 is inserted in the related second channel 49 starting from the first mouth 50 and then slides until the step 42 makes contact with the first end 36 of the shaft 2. When the inner edge 41 has been inserted in the second channel 49, the tab 43 which has not been plastically deformed is located in the first channel 45 with its main plane of extension coinciding with the main plane of extension of the blade 53, 54 on which it is located (Figure 10) . After plastic deformation of the tab 43, as illustrated in Figure 9, it is no longer coplanar with the main plane of extension of the blade 53, 54 on which it is located, and it is in contact against a closed stretch of the second side 48, thereby preventing the fan wheel 3 from moving along a line parallel to the axis of rotation of the shaft 2 towards the first end 36 of the shaft 2.

Moreover, as illustrated in the accompanying figures, in the preferred embodiment, the tab 43 present on each of the six second blades 54 is located at a part of the first hooking element 12 adjacent to the shaft 2. During fan 1 assembly, to allow the tab 43 which has not been plastically deformed to be inserted in the first channel 45, each slot 30 of the first disk 10, at the six first hooking elements 12 of the second blades 54 each also comprising the tab 43, has the second short side 32 open and in communication with the central hole 38.

In the preferred embodiment, at least one blade 53, 54 having the inner edge 41 inserted in the at least one second channel 49 also comprises an elongate portion 52 extending cantilever-style substantially parallel to the axis of rotation of the shaft 2 towards the second end 37 and resting on the shaft 2. That elongate portion 52 may have any shape or size, and is designed to increase the stability of the fan wheel 3 mounted on the shaft 2 even in the presence of uneven deformations of the fan wheel 3 caused by the greater heat present in the infeed zone for the hot fumes.

In the embodiment illustrated in the accompanying figures, the elongate portion 52 is present for all six of the second blades 54, which also comprise the tab 43, and said elongate portion 52 is in one piece with the first hooking element 12 of said second blades 54. That one piece is fitted between the first short side 31 of the related slot 30 and the shaft 2.

However, in other embodiments, not illustrated, the elongate portion 52 may be present on a plurality of blades 53, 54 which do not comprise the projecting element 43.

Finally, the materials usable for making the fan 1 for high temperatures according to this invention will advantageously be those commonly used for similar applications, such as special steels .

As already indicated, the fan 1 according to this invention does not comprise assembly means, such as solid rivets or blind rivets, or welds. Instead, the fan 1 is built based on interlocking connection of the various parts of which the fan 1 is constituted. In the embodiment illustrated in the accompanying figures, fan 1 assembly initially comprises coupling each hooking element 12, 13, 19 present on each blade 53, 54 to the corresponding counter-hooking element 14, 15, 20 of the first disk 10 and of the second disk 11, in order to position each blade 53, 54 in an angular position that is fixed relative to the other blades 53, 54 and to position the first portion 6 of all of the blades 53, 54 between the first disk 10 and the second disk 11. In particular, the above-mentioned coupling is performed by inserting the projecting portion 26 and the related projection 27 of each hooking element 12, 13, 19 in the corresponding slot 30 of the counter-hooking element 14, 15, 20 until the projection 27 has been brought beyond the constraining element 10, 11, 18. For that purpose, the length of the slot 30 is at least equal to or greater than the total radial height of the projecting portion 26 including the related projection 27 (total radial height measured radially relative to the axis of rotation of the shaft 2 and parallel to the main plane of extension of the blade 53, 54) . Then, according to the embodiment illustrated in the accompanying figures, the projecting portions 26 and the related projections 27 of the third hooking elements 19 (which during the preceding step passed through the related holes 22 of the second disk 11) are similarly inserted in the slots 30 of the third disk 18. Finally, according to the embodiment illustrated in the accompanying figures, the shaft 2 is inserted in the fan wheel 3, interlocking all of the parts. In fact, when the shaft 2 is inserted, the blades 53, 54 are all shifted radially outwards and it becomes impossible to disengage them from the respective constraining elements 10, 11, 18 unless the shaft 2 is removed again. In particular, the first end 36 of the shaft 2 is inserted by axially sliding from the central hole 38 of the first disk 10, with simultaneous insertion by axial sliding of the inner edges 41 of each blade 53, 54 in the second channels 49, until the first end 36 makes contact with the step 42 present on the inner edge 41 of each second blade 54. Simultaneously, each elongate portion 52 is positioned by axial sliding resting on the shaft 2. Insertion of the shaft 2 in the fan wheel 3 is subsequent to shifting of each blade 53, 54 radially relative to the axis of rotation of the shaft 2, with consequent positioning of the first flank 33 of the hooking element 12, 13, 19 resting on the first short side 31 of the slot 30, and positioning of the projection 27 facing the part of the supporting portion 29 of the counter-hooking element 14, 15, 20 that surrounds the slot 30 near the first short side 31 of the self-same slot 30. When the shaft 2 has been inserted, each non-deformed projecting element 43 is inserted in the first channel 45 with its main plane of extension coplanar with the main plane of extension of the second blade 54 in which it is made. To complete the interlocking connection between the fan wheel 3 and the shaft 2, the projecting element 43 is plastically deformed in such a way that it is at least partly facing a closed stretch of the second side 48 of the first channel 45, in order to prevent axial sliding of the fan wheel 3 towards the first end 36 of the shaft 2.

This invention brings important advantages.

First, thanks to the interlocking connection between the blades and the constraining elements that constitute the fan wheel, and the interlocking connection in turn between the fan wheel and the shaft, it is possible to obtain a centrifugal fan for high temperatures that is free of classic assembly means, is particularly stable and resistant to high temperatures.

Second, the above-mentioned interlocking connections allow a centrifugal fan for high temperatures to be obtained that is easier to make and has lower production costs than prior art fans for high temperatures .

Finally, it should be noticed that this invention is relatively easy to produce and that even the cost linked to implementing the invention is not very high.

The invention described above may be modified and adapted in several ways without thereby departing from the scope of the inventive concept .

All details may be substituted with other technically equivalent elements and the materials used, as well as the shapes and dimensions of the various components, may vary according to requirements .

Claims

1. A centrifugal fan for high temperatures comprising at least one shaft (2) having an axis of rotation and a fan wheel (3) mounted on the shaft (2), wherein the fan wheel (3) comprises a plurality of blades (53. 54) and at least two constraining elements (10, 11, 18) which substantially at least partly contain between them the blades (53. 54), wherein each blade (53. 54) is connected to at least one constraining element (10, 11, 18) by interlocking connection and wherein the fan wheel (3) is connected to the shaft (2) by interlocking connection.

2 . The fan according to claim 1, characterised in that the fan wheel (3) is constituted of parts which are connected to each other exclusively by interlocking connections.

3 . The fan according to claim 1 or 2, characterised in that the fan wheel (3) is connected to the shaft (2) exclusively by interlocking connection .

4 . The fan according to any one of the preceding claims, characterised in that each blade (53. 54) comprises at least one hooking element (12, 13, 19), in that for each hooking element (12, 13, 19) at least one constraining element (10, 11, 18) comprises a corresponding counter-hooking element (14, 15, 20), and in that each blade (53. 54) is connected to the at least one constraining element (10, 11, 18) by interlocking connection of the hooking element (12, 13, 19) with the corresponding counter-hooking element (14, 15, 20).

5 . The fan according to any one of the preceding claims, characterised in that the at least two constraining elements (10, 11, 18) comprise a first constraining element (10) and a second constraining element (11), extend mainly flat and are substantially parallel to one another, in that each blade (53. 54) comprises at least one first hooking element (12) and at least one second hooking element (13), in that the first constraining element (10) comprises at least one first counter-hooking element (14) for each blade (53. 54) and the second constraining element (11) comprises at least one second counter-hooking element (15) for each blade (53. 54), and in that each blade (53. 54) is connected to the first constraining element (10) by interlocking connection of the first hooking element (12) to the first counter-hooking element (14) and is connected to the second constraining element (11) by interlocking connection of the second hooking element (13) to the second counter-hooking element ( 15 ) .

6 . The fan according to claim 5, characterised in that it also comprises at least one third constraining element (18) extending mainly flat, which is substantially parallel to the second constraining element (11) and which is positioned adjacent to but spaced from the second constraining element (11), in that at least one group of blades (53. 54) comprises at least one third hooking element (19), in that the third constraining element (18) comprises at least one corresponding third counter-hooking element (20) for each third hooking element (19), and in that the blades (53. 54) of said group are fixed to the third constraining element (18) by interlocking connection of each third hooking element (19) to the corresponding third counter-hooking element (20).

7. The fan according to claims 4 to 6, characterised in that the hooking elements (12, 13, 19) comprise at least one projecting portion (26) extending cantilever-style from the related blade (53. 54) parallel to the axis of rotation of the shaft (2), in that the at least one projecting portion (26) comprises on a part of it which is furthest from the axis of rotation of the shaft (2) a projection (27) extending radially outwards relative to the axis of rotation of the shaft (2), and in that the at least one projecting portion (26) extends, parallel to the axis of rotation, from a zone of it connected to the rest of the blade (53. 54) until it is partly beyond the corresponding counter-hooking element (14, 15, 20), and the related projection (27) is positioned on the opposite side of the counter-hooking element (14, 15, 20) to the zone connecting the projecting portion (26) to the rest of the blade (53. 54) and is superposed on the counter-hooking element (14, 15, 20).

8 . The fan according to claim 7, characterised in that each counter-hooking element (14, 15, 20) comprises an elongate through opening (28) made through the constraining element (10, 11, 18) and a supporting portion (29) of the constraining element (10, 11, 18) surrounding said elongate through opening and on which the projection (27) of the projecting portion (26) of the hooking element (12, 13, 19) is superposed and coupled.

9. The fan according to any one of the preceding claims, characterised in that the shaft (2) comprises a tubular body (35) .

10. The fan according to claim 9, characterised in that the shaft (2) comprises a first end (36) and a second end (37), in that the fan wheel (3) is mounted on the shaft (2) at the first end (36), in that the first constraining element (10) has a central hole (38) through which the shaft (2) is inserted, in that the second constraining element (11) has a solid central part (39) positioned at the first end (36) of the shaft (2) but spaced from it to allow fluid communication between the inside of the tubular body (35) and an empty space (40) present between the various blades (53. 54) .

11. The fan according to any one of the preceding claims, characterised in that the fan wheel (3) and the shaft (2) comprise, one, a plastically deformed projecting element (43) and, the other, a contact element, and in that the interlocking connection between the fan wheel (3) and the shaft (2) is obtained at least by coupling the plastically deformed projecting element (43) and the contact element .

12. The fan according to claim 11, characterised in that at least one blade (53. 54) comprises the plastically deformed projecting element (43), and in that the shaft (2) also externally comprises a first channel (45) which constitutes the contact element and which extends annularly around the axis of rotation of the shaft (2), and in that the plastically deformed projecting element (43) is inserted in the first channel (45) .

13. The fan according to any one of the preceding claims, characterised in that the shaft (2) externally comprises at least one second channel (49) extending from the first end (36) substantially parallel to the axis of rotation of the shaft (2), and in that an inner edge (41) of at least one blade (53. 54) is substantially shaped to match the at least one second channel (49) and is inserted in the second channel (49) .

14. The fan according to claims 12 and 13, characterised in that the at least one blade (53. 54) having the inner edge (41) inserted in the at least one second channel (49) also comprises the plastically deformed projecting element (43) inserted in the first channel (45).

15. The fan according to claim 13 or 14, characterised in that the at least one blade (53. 54) having the inner edge (41) inserted in the at least one second channel (49) also comprises an elongate portion (52) extending cantilever-style substantially parallel to the axis of rotation of the shaft (2) towards the second end (37) and resting on the shaft (2) .

16. The fan according to any one of claims 13 to 15, characterised in that the shaft (2) externally comprises a plurality of second channels (49) extending from the first end (36) substantially parallel to the axis of rotation of the shaft (2), and in that the inner edges (41) of a plurality of blades (53. 54) are substantially shaped to match said plurality of second channels (49) and are inserted in the second channels (49) .

17. The fan according to any one of the preceding claims, characterised in that both the blades (53. 54) and the constraining elements (10, 11, 18) extend mainly flat, and in that each blade (53, 54) is positioned substantially perpendicular to the constraining elements (10, 11, 18).