The present invention relates to a hub-profile connection system for axial fan. The same invention further extends to the axial fan provided with this connection system.
Axial fans are commonly used where large amounts of air need to be moved, overcoming even high static pressures, specifically in the systems in which the air is used for cooling by means of heat exchange. In this case, fans are used which may reach-very large diameters, even twenty meters.
In the design of this type of fan, the connection between hub and part of the blade intended to displace the air, hereinafter called profile, is a particularly important issue, because the stresses here reach their maximum and such connection is thus a zone subject to breakage risks.
It is the main object of the present invention to provide a hub-profile connection system for axial fans, which, in relation to the known hinged or flexible rigid constraint connection systems, presents low static and dynamic loads, a better construction simplicity and a-higher resistive moment.
These and other objects are reached by the hub-profile connection system and by the axial fan of claims 1 and 9, respectively. Preferred manners for manufacturing the invention result from the remaining claims.
In relation to the known art, the hub-profile connection system of the present invention offers the following advantages:
Compared with the known rigid, hinged and flexible constraint systems, the system of the invention and the axial fan of the present invention offer lower static and dynamic loads, as well as construction simplicity, with consequent cost saving and vibration abatement. With respect to hinged constraint systems, the present invention offers advantages of a particular construction simplicity, and the possibility of graduating the freedom of movement on the vertical plane as desired and the absence of wear. Unlike flexible constraint connection systems, the present invention also displays a. higher resistive moment and thus the possibility of using more cost effective materials with lower mechanical features, assuming the section being equal. It also displays a higher torsional strength and a higher rigidity on the vertical plane, with consequent solution of the problem of excessive profile lowering in large diameter fans.
These and other objects, advantages and features will result from the following description of a preferred embodiment of the hub-profile connection and the axial fan of the present invention shown, by way of non-limitative example, in the FIGS. of the accompanying drawings, wherein:
For a better understanding of the system according to the present invention,
These forces generate a bending moment and a torque, with static and dynamic loads which are particularly relevant for the structural dimensioning calculations of the fan. A reduction of these moments allows important savings.
Connection 4 between hub 1 and profile 3 of blade 2 of an axial fan is currently mainly made in three ways: with a rigid system, with a hinged system and with a flexible system.
The three cases will be briefly described, indicating the main advantages and the disadvantages thereof, in order to compare them with the invention and highlight its superiority.
In the case of a rigid system connection (
In the known hinged connection systems (
Finally, in the case of flexible connections (
The hub 1 profile 3 connection system made according to the invention, as shown in
The same elements 9,10 on profile 3 side may either come into direct contact or a spacer 13 may be interposed between the same (
Angle δ of lower element 10 may be either positive, or negative as shown in
Furthermore, the two elements may be tapered, have reciprocally different geometries, both in section and in plan, or even be formed by different materials.
The use of two separate and distinct elements, which may be made as above and reciprocally positioned in space as desired, allows to design a hub-profile connection with variable resistance modulus, maximum on hub side and decreasing in the direction of the profile, and thus to obtain that when the profile is subjected to the operating loads, the sections rotate presenting an angle with ever greater increases with respect to the vertical. The longitudinal section of elements 9,10 may have an arc of a circle or parabolic pattern, with maximum curvature on the profile side.
The connection system will allow the profile to incline itself with respect to the horizontal plane, continuously positioning itself in a zone in which the centrifuge force allows the profile to generate a force of entity and direction opposite to that of traction, tending to cancel the bending moment. The system itself will also present a high degree of displacement on the vertical plane, thus reducing both the dynamic and the static loads. The present invention will allow this to occur in extremely controlled manner, as not possible according to the known techniques.
In order to facilitate the understanding of the present invention, the simplest fixing solution of a blade to the hub, i.e. the one in which the blade is not adjustable, is shown in drawings 5, 8 and 9. It is must be underlined that fastening blocks 11 and 12 may also be designed so as to provide the blade with the possibility of being keyed and the invention is applied also to this type of fan.
Number | Date | Country | Kind |
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07425496 | Jul 2007 | EP | regional |
Number | Name | Date | Kind |
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1501201 | Cates | Jul 1924 | A |
6884035 | Young | Apr 2005 | B2 |
20040009064 | Young | Jan 2004 | A1 |
20060024165 | Gajewski | Feb 2006 | A1 |
20060140770 | Liu | Jun 2006 | A1 |
20060278766 | Wang | Dec 2006 | A1 |
Number | Date | Country |
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1 571 345 | Sep 2005 | EP |
Number | Date | Country | |
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20090035139 A1 | Feb 2009 | US |