EPO Enlarged Board to extinguish uncertainty on patent claim interpretation

EPO Enlarged Board to extinguish uncertainty on patent claim interpretation

In oral proceedings held today, on 10 April 2024, the EPO Technical Board of Appeal confirmed it will ask the Enlarged Board of Appeal whether content in the description should be used to interpret the claims (in T 439/22, board 3.2.01).

The appeal concerns a decision by the opposition division to uphold European Patent No. 3076804 owned by Philip Morris Products S.A. The patent relates to so‑called ‘heat-not-burn' tobacco products. While heat-not-burn products aim to avoid combustion, this referral looks set to ignite the long-running debate on the role of the description in claim interpretation at the EPO.

This appeal hinges on the interpretation of a key term in the claims – this wording is arguably clear on its face, whereas the patent description suggests that a broader interpretation may be needed. A broader interpretation could mean the patent is invalid, so the patent proprietor favours the narrower interpretation.
To address this uncertainty, the Board has indicated in the oral proceedings that they will refer questions to the EPO Enlarged Board of Appeal for their decision on the matter.


The key issue in the appeal proceedings is the interpretation of the claim term "gathered" in the context of a "gathered sheet" in a tobacco product, and whether a “spirally wound” material in the prior art would anticipate this “gathered sheet”.

The opponent argued for a broad interpretation of the term based on the definition provided in the description, which includes (among other things) various ways of compressing or constricting the sheet. This arguably means that the “gathered” terminology should be interpreted broadly as encompassing any way of bringing together the material, such as by spirally winding in the prior art.

The proprietor argued the term “gathered” already has a clear and unambiguous meaning in the art and on its face, and therefore the description should not be consulted to broaden that interpretation.

Divergent law

The referral to the Enlarged Board of Appeal highlights a divergence in the approach to claim interpretation among the EPO's Technical Boards of Appeal. Two distinct lines of case law have emerged, as exemplified by decisions T 1473/19 and T 169/20.

In T 1473/19, the Board held that the description should be taken into account when interpreting claim terms, even if the wording appears clear. Conversely, in T 169/20, the Board considered the description should only be relied upon for interpreting claims in exceptional cases where the claimed subject-matter or technical context needs clarification. If the skilled person considers the wording of a claim to be clear on its face, especially when the term has a well-established meaning in the relevant field, then consulting the description for interpretation is deemed unnecessary and unjustified.

There is also a question of whether the approach of ignoring the description could lead to a divergence in the way claims are interpreted by the EPO (e.g. in pre-grant examination or post-grant opposition proceedings) when compared with post-grant revocation and infringement proceedings by national courts and before the UPC. In these post-grant national/UPC proceedings, several territories regularly consider the description when interpreting claim terms, though this is an area of law which is not harmonised in Europe.

Harmony is coming?

At today’s oral proceedings, the Board confirmed it will ask the Enlarged Board of Appeal how this area of law should be interpreted with a view to ensuring uniform application of the law (at least as far as EPO proceedings are concerned).

This referral poses interesting questions about how the scope of patent claims should be interpreted in both pre- and post-grant proceedings. It would appear odd that, post-grant, one could essentially broaden the scope of their claims by reference to the description at a national court (or before the UPC), whereas the EPO is arguably confined to considering a narrower scope (based on the definition of a term on its face alone) during examination and opposition proceedings.

Indeed, this point was raised during the hearing today, with a few notable references to the famous “Angora cat” paradox, mentioned many years ago by Lord Justice Jacob in the Court of Appeal. This is a metaphor about how a patent proprietor might try to argue for a broad claim scope during infringement (like a fluffy, dry Angora cat with a large, expansive appearance) while simultaneously arguing for a narrower claim interpretation when assessing the patent's validity in view of the prior art (akin to a wet Angora cat which looks much smaller and more constricted in size). That said, some jurisdictions prevent proprietors from using contradictory claim constructions through the doctrines of file-wrapper or patent prosecution estoppel.

Regardless of the outcome of the referral, the hearing today underpins the ongoing need for applicants and proprietors in Europe to make sure their description and claim scope are aligned. While we await the decision of the Enlarged Board, we should also be aware of the possible broader interpretations of claim terms at the EPO, as influenced by the description.

Get in touch

We will be closely monitoring the situation and providing updates once we hear news and the questions to be referred, and any other updates as this case develops.

If you have any questions or would like to discuss the potential impact on your cases, please contact Tom Hailes, James Snaith, or your usual Kilburn & Strode advisor.

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