Seb SA v Societe De'longhi Spa

For inventive step under the Patents Act 1977, obviousness is a legal standard applied to facts. The four-stage Windsurfing analysis is appropriate, but the court need not recite every stage in every judgment. Common general knowledge must be assessed through the normally skilled but unimaginative person or team and distinguished from information known only to some. Known features may nevertheless form an inventive combination, although failure of earlier designers to find the same solution does not itself establish inventiveness. An appellate court should not interfere with the trial judge’s evaluation absent an error of principle. A claim requiring an air space to be closed need not require hermetic sealing where its purpose is to prevent dangerous hot-air escape.

SEB, a patentee, sued De’ Longhi for infringement by 21 deep-fat fryer models. De’ Longhi denied infringement and challenged validity for obviousness based on common general knowledge and Toshiba, and for insufficiency. Pumfrey J dismissed the action, holding the Patent obvious, although it would have been infringed if valid, and rejecting insufficiency. SEB appealed the obviousness finding. De’ Longhi sought to uphold the result on additional grounds, including Toshiba, claim construction and insufficiency. The appeal concerned obviousness over common general knowledge or Toshiba, whether the rings closed the air space for claim 1, and whether the Patent sufficiently disclosed the invention.

Appeal dismissed. The Court of Appeal upheld the finding that the Patent was invalid for obviousness.

1. The statutory question under the Patents Act 1977 is whether the invention was obvious to a person skilled in the art having regard to the relevant state of the art. The four-stage approach in Windsurfing International Inc. v Tabur Marine (GB) Ltd [1985] RPC 59 remains appropriate: identify the inventive concept, adopt the mantle of the normally skilled but unimaginative addressee, identify the differences between the state of the art and the invention, and ask whether those differences would have been obvious without hindsight. There is no requirement that every judgment visibly recite each stage.
2. Obviousness involves applying a legal standard to facts. An appellate court should be very cautious before differing from the trial judge’s evaluation, particularly where the issue is one of degree. No error of principle had been shown.
3. Common general knowledge had to be assessed through the skilled design team. The judge was entitled to find that the team knew the relevant properties and uses of metals and plastics, the increasing use of plastics in domestic appliances, the operation of heating appliances, and the use of insulating rings, gaskets and spacers. Material not fairly characterised as common general knowledge had to be excluded.
4. The fact that individual features were known did not make their combination automatically obvious. Nevertheless, on the evidence, incorporating an insulating ring to permit the use of inexpensive polypropylene for the skirt was obvious. The fact that earlier design teams had not reached the same solution did not establish an inventive step. Claim 9 added nothing material.
5. The Toshiba objection did not require determination because the Patent was already obvious over common general knowledge.
6. Although unnecessary to the result, the court upheld the construction of feature 8. “Closed” was contextual and functional. It did not require hermetic sealing, but required closure sufficient practically to prevent convective cooling and the escape of hot air creating a risk of burning. On the judge’s finding that air flow was practically negligible, the fryers would have infringed if the Patent had been valid.
7. The insufficiency objection also failed. The Patent disclosed the invention clearly and completely enough for it to be performed.

• Court of Appeal (Civil Division) — On 4 July 2003, the appeal was dismissed. The court upheld the finding of obviousness and did not determine the Toshiba issue.
• High Court of Justice, Chancery Division, Patents Court — Pumfrey J ordered on 26 July 2002 that the action be dismissed because the Patent was obvious. He held that the alleged fryers would have infringed if the Patent had been valid and rejected the insufficiency objection.