In early 2017, the UK Court of Appeal handed down its judgment in the case of Wobben Properties GmbH v Siemens Public Ltd Company & Ors, an appeal from a first instance decision of July 2015 centred around one of Wobben’s wind turbine control patents. Birss J in the Patents Court had found the patent invalid for obviousness and, in any event, not infringed by the activities of Siemens and the other seven defendants, both of which findings Wobben now sought to overturn.
The patent in question, EP(UK) 0 847 496, relates to a method of controlling turbines during high winds. In particular, the invention as claimed lies in a method involving continued operation above a ‘limit’ wind velocity, at which it would ordinarily be shut down altogether for safety reasons, with the power output and rotor speed being continuously reduced in dependence on the rise in wind speed. By ‘ramping down’ the power in this way, the invention means to mitigate the impact on the electricity grid that can result when large numbers of turbines suddenly cease operation in quick succession, while at the same time respecting the need to protect the turbine from the heavy loading that it experiences at high wind speeds.
At first instance, Birss J found that the invention would have been obvious to the skilled person at the 1995 priority date in the light of a single document, a theoretical research study published in 1982. The paper is interested in sudden changes in the power output of wind turbine clusters and their impact on the grid, and it concludes – among other things – that the feasibility of a control strategy in which turbine output is gradually rather than abruptly reduced to zero once the limit wind velocity is reached would be worthy of investigation. The paper does not mention a reduction in the rotational speed of the turbine rotor, which the patent claim requires, simply because turbines operable with a variable rotor speed were not commonly implemented in the industry until after the time at which it was written. Nevertheless, on the basis of evidence presented to him by expert witnesses for both parties, Birss J held that by 1995 it would have been “entirely obvious” to the skilled person to apply the document to a machine designed to operate at varying speeds; and that, in doing so, the skilled person would consider leveraging that technology as a way to implement the gradual power reduction advocated in the prior art. Though not the only option available to him, said Birss J, this would be an obvious approach for the skilled person to put into practice.
Wobben centred its appeal on the submission that Birss J had “wrongly directed himself as to the legal test for obviousness”, and made “fundamental errors” in assessing the expert evidence presented to him. In particular, the judge ought to have found that certain flaws in the approach taken by the witness appearing for Siemens “fatally undermined” the value of his evidence. Further, the judge was “not entitled” to infer as he did that the skilled person, beginning with the prior art, would take steps to perform certain relevant calculations or as to what the results of those calculations would be: there was “no evidence” to support those conclusions.
Giving the leading judgment, Kitchin LJ dismissed these arguments. On the point of the flaws in Siemens’s evidence, he noted (at ) that “there was at the end of the day a degree of common ground” between the opinions of the witnesses on the two sides; and that the judge was not wrong to “step back and consider, as he did, the wider picture”. In the context of the common practice in the industry at the priority date, the skilled person “would naturally consider” the problems that a continued operation above the limit velocity would present, and would know that a reduction in wind turbine rotor speed would provide a corresponding solution.
Regarding the judge’s inferences as to the skilled person’s initiative, Kitchin LJ took the view that those conclusions found proper basis in the common general knowledge prevailing at the priority date of the patent.
This decision is of note for its endorsement of a qualitative approach to the assessment of inventive step. Though a question of fact, where (as in this case) those facts are complex and liable to muddy the fundamental issue of obviousness, then a wider perspective can be both useful and appropriate. It also serves as a reminder that the common general knowledge should not be overlooked in considering what would and would not have appeared obvious to the skilled person at the priority date of an invention.
This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.