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Wobben Properties GmbH v. Siemens plc & Ors, UK, High Court (Patents Court), Birss J, 20 July 2015, Neutral Citation Number: [2015] EWHC 2114 (Pat)

Wobben’s patent in suit concerned a method of operating a pitch-controlled wind turbine.  The inventive concept of the claimed invention was to allow operation of wind turbines at wind speeds above the ordinary shut down wind speed (the speed at which a wind turbine is otherwise compulsorily shut down in high winds) so as to extend the operating window and potentially increase power yield as well as network compatibility.  This continued operation involved progressively reducing the power and rotor speed of the turbine as the wind speed increased. The patent was held to be invalid for lack of inventive step over one of the cited pieces of prior art, and even if valid would not have been infringed by the defendants’ wind turbines.

The claimed invention allowed for a continuous reduction in turbine operating speed and power above the shutdown wind velocity rather than complete shutdown.  The patent contained a schematic figure for the claimed invention demonstrating operating speed and power versus wind velocity, including above what would otherwise be shutdown velocity, with a continuous reduction in power and rotor speed with increased wind speed above that velocity.  No worked examples were disclosed in the patent.  Nor were the claims limited to any particular embodiment of the inventive concept claimed other than by pitch control (i.e. adjustment of tilt of the rotor blades).

The defendants alleged that the patent was not novel over one of the prior art citations.  The judge, Birss J, rejected this attack.  One notable feature of the judge’s approach is that although a figure in the prior art patent appeared to disclose exactly the same method as that in figure 1 of the patent, the judge held that the prior art figure had to be read in context of the disclosure of the document as a whole.  As a result, the prior art disclosure did not anticipate the patent.  The judge noted that the prior art document had to be read as at its date of publication, and that reading the prior art as disclosing the approach in the patent in suit involved hindsight.

On inventive step, the judge held that the lack of disclosure in the patent in suit might be relevant to an invalidity attack based on insufficiency or lack of plausibility, but not to the classic inventive step analysis of the English courts, which requires the court to judge the invention as defined in the claim. 

As a first step in the classic Windsurfing/Pozzoli analysis for obviousness, the judge was of the view that there was no need to spend time identifying an inventive concept over and above the words of the claim (see the earlier report on VPG Systems v Air-Weigh on whether the Court should identify the inventive concept or merely construe the claim).  However, he did go on to identify the “heart of the invention”, being the concept of running a variable speed, variable pitch (VSVP) turbine in high winds so as to reduce both speed and power “in dependence on" the rise in wind speed. The second prior art citation disclosed a means of gradual ramping down of power in a constant speed turbine, whereas the patent claims required a reduction in both power and operating speed of the turbine. 

The judge held that it required no inventive activity for the skilled person to think seriously about how to implement the proposal in the prior art document in VSVP turbines, thus arriving at the claimed inventive concept, given that the focus of the industry at the priority date was on VSVP turbines.  Although it was not the only way to put the prior art teaching into practice in a VSVP turbine, it was an obvious approach.  Reducing the speed of the rotor had an obvious advantage in terms of loading and fatigue. On infringement, the judge held that the process operated by the defendants’ wind turbines reduced rotor speed “in dependence on” a rise in the modulus of rotor acceleration in order to protect the turbine from dynamic loads associated with rotor accelerations and decelerations.  The judge held that rotor acceleration was not used as a surrogate for wind speed. As a result, the rotor speed of the defendants’ VSVP turbines was not reduced as a function of wind velocity as required by the patent claims.

The judge also commented in passing on foreign judgments concerning the patent in suit that had been drawn to the Court’s attention even if neither party was said to place reliance on them.  The Opposition Division of the EPO had rejected an opposition by a third party, but Birss J noted that the Division did not have in front of it the prior art over which he had held the patent obvious.  In German infringement proceedings before the Düsseldorf District Court, the Court dismissed the patentee’s claim for infringement against one of the defendants in the English case, whereas proceedings in Spain against a third party, the Spanish Court held the patent valid and infringed.  In the judge’s view, the key prior art in question was not cited in the Spanish case and it was not clear whether the turbines in dispute operated in the same way as those of the defendants in the English case.

Read the decision here.  

Headnote: Gregory Bacon, Bristows.  Siemens is represented by Bristows LLP in the above dispute, but the author has had no involvement.