Sabaf, an Italian maker of gas cooking components, holds a UK patent for a burner. It took action against its domestic rival, Meneghetti, which it accused of importing burners to the UK for sale by MFI, saying this was an infringement of its UK patent.
The decision involved analysis of gas cooker designs. Gas hobs need to mix the gas with air and push the gas through the holes of the burner in a steady stream. Old gas cookers sat above a tube which had an inlet for air and which increased in diameter along the direction of flow, to slow the stream of gas and, by a conversion of kinetic into potential energy known as the "Venturi effect", increase its pressure. But in older cookers the pipe took up a lot of space beneath the cooker, making it less suitable for hobs. The Sabaf patent's solution was to enable both the air intake and the Venturi effect to take place in the burner, above instead of below the hob.
These features – taking air in from above the hob and using a Venturi effect above the burner – were examined by Lord Hoffman as two separate inventions to which he applied the obviousness test, a method established in a case from 1985.
In that case, Windsurfing International Inc., maker of the first commercial windsurfer, asserted its patent rights against a rival, Tabur Marine. But Tabur successfully argued that the patent was invalid. It was able to show prior art: footage from 1958, at least 10 years prior to the grant of the patent, which showed a 12 year-old boy playing on his homemade windsurfer.
The obviousness test laid down in the Windsurfing case is as follows:
First, identify the inventive concept embodied in the patent.
Second, assume the mantle of the normally skilled but unimaginative person in the art at the priority date and impute to him what was, at that date, common general knowledge in the art in question.
Third, identify what, if any, differences exist between the alleged infringing product and the patented invention.
Finally, the court has to ask itself whether, viewed without any knowledge of the alleged invention, those differences constitute steps which would have been obvious to the skilled man or whether they require any degree of invention.
Lord Hoffman reasoned that both features of the gas burner were obvious.
"Two inventions do not become one invention because they are included in the same hardware," he wrote. "A compact motor car may contain many inventions, each operating independently of each other but all designed to contribute to the overall goal of having a compact car. That does not make the car a single invention."