Wagner International AG & Ors v Earlex Ltd

For patent validity, added matter exists where an amendment presents the skilled person with technical teaching that is not directly and unambiguously derivable from the application as filed. A feature may be implicit only where it is genuinely disclosed, not merely an obvious way of implementing the disclosure. A public display of a product anticipates only if the skilled person can derive the claimed invention clearly and unambiguously, with disclosure and enablement established. For obviousness, the structured Pozzoli approach is applied. Evidence that a skilled person could recreate a product is not enough by itself: the relevant question is whether doing so, including routine adjustments, required invention.

The claimants alleged that Earlex’s HVLP paint-spray gun infringed claims 1 and 13 of European Patent (UK) No 0596939. Earlex denied infringement and counterclaimed for revocation on added matter, lack of novelty and obviousness.

The alleged invention used selectively blocked paint-shaping passages and venting passages in an air cap to relieve back pressure. The court considered two Earlex air-cap designs, a public demonstration of a Wagner FineCoat sprayer at the March 1991 Home Center Show, and other alleged prior disclosures. The central issues were construction, infringement, added matter, anticipation and inventive step.

1. Disposition. Neither the Original Design nor the Modified Design infringed claim 1 or claim 13. The patent was invalid for added matter and for obviousness over the disclosure at the Home Center Show. It was unnecessary to determine the documentary prior-art attacks.
2. Construction and infringement. “Venting passage” was a functional expression. It did not require the passage to be angled away from the air-cap axis. The passage had to achieve venting without altering the shape of the paint-spray pattern. The evidence did not establish that the Original Design’s venting holes had no material effect on the spray pattern. The Modified Design satisfied the relevant feature, but the claimants failed to prove the required relationship between the venting and shaping air flows.
3. Added matter. Under Patents Act 1977, section 72(1)(d), the relevant question was what the skilled person would derive directly and unambiguously from the application as filed, using common general knowledge. The expressions “blocking means” and “shape of the paint spray” did not add matter. By contrast, the application did not disclose, expressly or implicitly, equal or substantially equal venting and shaping air flows, or sealed fluid communication. Those features therefore added matter.
4. Novelty and inventive step. The public demonstration disclosed a device falling within the claims, but did not clearly and unambiguously disclose how the venting holes were connected to the air supply or whether the venting air interfered with the paint spray. It therefore did not anticipate the claims. Nevertheless, a skilled person who examined and operated the device could recreate the arrangement and make routine trial-and-error adjustments to avoid interference with the spray. The claimed invention was consequently obvious.
5. Prior use. The field trials were too insecure a foundation for validity attacks because public conduct and freedom to use the information had not been established on the balance of probabilities.