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In a previous post, I wrote about the new Swift wind turbine, developed by Scottish energy products and solutions company Renewable Devices Swift Turbines Ltd. (RDST) for use in densely populated areas. Last month RDST obtained a patent for its turbine:  U.S. Patent No. 7,550,864 issued June 23, 2009.
RDST’s design overcomes the problem of wind turbine noise by using a circular diffuser (21) that rings the turbine blades. In operation, when the airflow reaches the ends of the blades, it contacts the diffuser and proceeds in a circumferential path instead of flowing off the ends of blades.
The Swift turbine also has a furling device (50) with tailfins (53, 54).  When the airflow exceeds a certain speed, the furling device rotates the rotor to maintain the direction of the airflow in line with the turbine’s rotational axis. In excessively high winds, the turbine rotor can be rotated out of the airflow altogether. These measures reduce the vibrations of the turbine assembly components.Â
Finally, the Swift turbine has a mounting structure that includes a rubber core to absorb vibrations before they spread upward to the moving parts of the turbine assembly.
RDST overcame rejections by the U.S. Patent & Trademark Office that its patent claims were obvious over two prior art patents by using a host of arguments, including some of the so-called “secondary considerations” of non-obviousness.
Independent claim 1, as amended during prosecution (and as ultimately issued) recited:
A rotor for a roof-mounted wind turbine comprising a plurality of radial blades and a ring-shaped diffuser connected to the outer tips of the blades, wherein the diffuser is an aerofoil diffuser and is configured such that it inhibits the partly axial and partly radial airflow from the blades, said airflow becoming circumferential when it contacts the aerofoil diffuser, thereby reducing acoustic emissions.
Thus, the claimed turbine rotor contained the following mechanical components:Â a rotor, a plurality of blades, and a ring-shaped diffuser, wherein the diffuser is an aerofoil diffuser.
The U.S. Patent & Trademark Office (PTO) viewed this iteration of claim 1 as a combination of known elements and rejected the claim as obvious over two prior art patents, one of which disclosed a rotor, blades and a diffuser and another that taught an aerfoil diffuser. According to the patent examiner, it would have been obvious to combine the aerofoil diffuser of reference two with the rotor blades and diffuser of reference one to achieve a reduced noise level.
RDST successfully overcame this rejection by pointing out deficiencies in the cited prior art and by using a host of non-obviousness arguments. For instance, RDST argued that the prior art taught away form attaching a large mass to the ends of rotor blades, that the degree of noise reduction was an unexpected result and that competing designs had failed to achieve comparable noise reduction.
Finally, to tie it all together for the patent examiner, RDST submitted audiovisual evidence of the its quiet turbine in action.
