Alan Nuttall Ltd v Fri-Jado UK Ltd & Anor

Patent claims must be construed purposively, by asking what the skilled person would understand the claim language to mean in the context of the description and drawings. Purpose does not justify adding limitations which the claim does not contain or disregarding deliberate claim features. A patent need not enable every possible device falling within its claims, provided the claimed technical principle is disclosed and enabled. Obviousness requires identification of the skilled person, common general knowledge, the inventive concept, the differences from the prior art and whether those differences would have been obvious. Secondary evidence, copying and commercial success assist only where they are logically relevant to that inquiry.

Alan Nuttall Limited alleged that Fri-Jado UK Limited and Fri-Jado BV infringed claims 1 and 3 of GB 2,348,697, concerning a heated food display cabinet using heated-air circulation and an air curtain. The defendants denied infringement and challenged the patent for insufficiency and obviousness, relying principally on Guibert, Detwiler and common general knowledge. The central issues were the construction of the expressions “outlets over a substantial length”, “draw air from the upper end of the chamber” and “air collection zone”, the sufficiency of the disclosure, and whether the claimed two-fan arrangement was obvious.

1. Construction. The claims were to be construed purposively in accordance with the language used, read in the context of the specification and drawings. Purpose could not be used to imply a limitation which the claim did not contain. Claim 1 did not require the outlets to be the sole means of achieving even heating, nor did it require any particular arrangement for the second fan. The second flow-inducing means had to draw air from the upper end of the food-storage chamber, with the effect of promoting heated-air flow over the uppermost food.
2. “Air collection zone” in claim 3 meant a dedicated zone in which stagnant hot air could accumulate as a buffer available when required. The defendants’ cabinet did not contain such a zone.
3. Infringement. The Mark 2 cabinet had outlets over a substantial length of its duct and its second flow-inducing means drew air from the upper end of the chamber for use in forming the air curtain. Claim 1 was therefore infringed, if valid. Claim 3 was not infringed.
4. Insufficiency. A patent need not teach the skilled person how to make every possible artefact within the scope of its claims. The patent disclosed the same general technical principle as the defendants’ cabinet, even if its drawings did not lead directly to that particular embodiment. The insufficiency attack failed.
5. Obviousness. Applying the structured approach in Pozzoli Spa v BDMO SA [2007] EWCA Civ 588, the relevant inventive concept included separate fans for the food-warming circuit and the air-curtain circuit. Guibert did not make that arrangement obvious, and Detwiler lacked the claimed duct with outlets over a substantial length. Common general knowledge likewise did not supply the claimed concept. The attack on validity failed.

The claim succeeded in respect of infringement of claim 1. The attack on the patent failed.

First-instance decision in the Patents Court. No prior appellate decision is stated in the judgment.