Patents Form No 5 Our Ref MH501584
NEW ZEALAND
PATENTS ACT 1 953
Complete After Provisional No 329093 Filed 3 November 1 997
COMPLETE SPECIFICATION
INTELLECTUAL PROPERTY OFFICE OF NZ
2 2 OCT 1933 RECEIVED
FAN BLADE
We, WINDSOR ENGINEERING GROUF LIMITED, a New Zealand company of 18 Cashew Street, Grenada North, Wellington, New Zealand hereby declare the invention, for which We pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement
MH SU PT0527079
) 1
The present invention relates to improvements in and relating to a fan blade and including methods of manufacturing same
At the present time, fan blades are generally cast
This manufacturing technique results in blades which are comparatively heavy and costly Casting also takes more care and nondestructive testing What is required is uniform mass distribution, good surface finish and good structural integrity
It will be appreciated that blades which are heavy, increase the risk of severe damage to surrounding components when the blade fails Also, that a non-uniform mass distribution will require the resultant blade to be properly balanced before use Additionally, a heavy blade will tend to have lower natural or resonant frequencies and so is more likely to be affected by vibration and resonance problems
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a fan blade and/or methods of manufacturing same which will avoid or at least obviate at least some of the above difficulties or which at least will provide the public with a useful choice
Further objects of this invention will become apparent from the following description
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is thus provided a reversible extruded fan blade of an which is substantially hollow and symmetrical axis, the direction of rotation of the fan blade
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BACKGROUND OF THE INVENTION " "
/ 1
reversed to provide a substantially equal flow in either direction
According to a further aspect of the present invention, there is provided a method of manufacturing a reversible extruded fan blade including utilising an at least semi-rigid and extrudable material and extruding it into a substantially hollow fan blade of a required profile and including the step of twisting the fan blade symmetrically about its central axis to enable the fan blade in use to be reversed to provide a substantially equal flow in either direction
According to a further aspect of the present invention, there is provided a method of manufacturing a fan blade substantially as herein described
According to a further aspect of the present invention, there is provided a fan blade when manufactured by the method of either of the two immediately preceding paragraphs
According to a further aspect of the present invention, there is provided a fan blade substantially as herein described and/or with reference to the accompanying drawings
Further aspects of this invention which should be considered in all its novel aspects will become apparent from the following description given by way of example of possible embodiments thereof and in which reference is made to the accompanying drawings
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows very diagrammatically a side view of a fan blade according to one possible embodiment of the invention, and
Figure 2
shows an end view of the fan blade of Figure 1
3
DESCRIPTION OF PREFERRED EMBODIMENTS
The fan blade of the present inv^ n is manufactured from an at least semi-rigid and extrudable matenal such as metal or plastics or any other material that is at least semi-rigid and capable of extrusion may be alternatively be used
The extrusion may be substantially hollow so as to substantially reduce the weight of the resultant fan blade
The shape and dimensioning of the fan blade will depend on its required operational characteristics The fan blade may be twisted about is central axis to a required degree The fan blade may be symmetrical or with a zero camber to enable the direction of rotation of the fan blades to be reversed to provide substantially equal air flows in either direction
It is envisaged that in providing a uniform or non-uniform twist along the length of the fan blade, this may be achieved by fixing one end and applying torsion to either the other end of the blade, progressively along the blade, or possibly by rolling the fan bade longitudinally
In providing a fixing for the fan blade, it is evisaged that a cast boss, or a boss from solid bar, allowing pitch angle adjustment, may be utilised with the boss then being bolted, bonded and/or welded to the extruded fan blade
Referring to Figures 1 and 2 of the accompanying drawings, it is seen that an extruded fan blade referenced by arrow 1 has respective longitudinal edges 2 and 3 extending between end portions 6 and 7 In this instance, the fan blade 1 has been provided with a twist about its substantially central axis 4 by an amount indicated between the arrows
4
It is seen that the extruded fan blade 1 is substantially hollow but with extruded material being present in this example about the central axis 4 and, in the form of ribs or webs or the like, at intermediate portions 5 between the central and edge portions
It will be appreciated that by using a substantially hollow extrusion, a substantially lighter fan blade 1 can result which inherently may reduce the potential for out of balance forces to be created during the operation of the fan blade
Additionally, in the extrusion of the fan blade 1, a much more uniform distribution of mass of material can be achieved, compared to a cast fan blade, which again assists in avoiding out of balance forces
The ability of the fan blade 1 of the present invention to be much lighter than a cast fan blade also provides higher natural or resonant frequencies and so reduces the possibility of failure due to blade resonance Additionally, of course, by utilising less material for the extruded fan blade 1, there is reduced cost and it has been found that an extrusion operation can provide for a better surface finish It has also been found in testing that a much greater structural integrity can be obtained through the extrusion of the fan blade 1 rather than the use of alternative manufacturing techniques
It will be further appreciated that by the ability to achieve a lighter fan blade, the fan structure can have improved performance, both in respect of durability and in enabling faster rotational speeds to be achieved
Where in the foregoing description reference has been made to specific components or integers of the invention having known equivalents then such equivalents are herein incorporated as if individually set forth
Although this invention has been described by way of example and with reference to possible embodiments thereof it is to be understood that modifications or improvements may be made thereto without departing from the scope of the invention as defined in the appended claims