Why is it important to clearly define each term in a patent and have good fallback positions (Application of the Decision G1/24)

On December 11, 2025, the Board of Appeal handling the case that led to Decision G1/24 revoked the patent in question.

The Contested Patent (EP3076804)

The patent was related to “a heated aerosol-generating article for use with an electrically operated aerosol-generating device comprising a heating element” (essentially, an e-cigarette refill).

The main claim as granted for this patent was as follows:

A heated aerosol-generating article (1000, 2000) for use with an electrically-operated aerosol generating device (3010) comprising a heating element (3100), the aerosol-generating article comprising an aerosol-forming substrate (1020, 2020) radially encircled by a sheet of thermally conductive material (1222, 2222), in which the aerosol-forming substrate comprises a gathered sheet of aerosol-forming material circumscribed by a wrapper, the wrapper being the sheet of thermally conductive material which acts as a thermally-conducting flame barrier for spreading heat and mitigating against the risk of a user igniting the aerosol-forming substrate by applying a flame to the aerosol-generating article.

Opposition Grounds

Following the grant of this patent, a Chinese competitor filed an opposition, notably on the grounds of lack of novelty with respect to a prior art document not cited during the examination proceedings. This prior art document, EP2368449 B1 (referred to as D1 in this article), disclosed an article exhibiting features falling within the main claim and in which a tobacco sheet is rolled into a tube.

The patent proprietor argued that the rolled sheet described in the prior art document was not a “gathered sheet”.

This was followed by lengthy debates on the interpretation that a person skilled in the art could make of the term “gathered sheet” (“feuille froncée” in the French translation and “zusammengefasstes Flächengebilde,” which could be translated as a condensed planar structure in the German version of the claims). The opponent raised that the patent description contained a definition of the term “gathered sheet” as a sheet of tobacco material convoluted, folded, or otherwise compressed or constricted substantially transversely to the cylindrical axis of the rod.

The patent proprietor considered that the claims alone determined the scope of the patent and that the term “gathered sheet” had a widely agreed meaning in the tobacco industry, and that upon reading the claims independently of the description, the skilled person would have assumed that this term relates to a sheet which was folded and convoluted to occupy a three-dimensional space. Accordingly, for the patent proprietor, there was no need to consult the description to interpret this term.

The Decision of the Opposition Division

The Opposition Division concluded in favour of the patent proprietor that a rolled sheet as presented in document D1 is not a “gathered sheet” and that, consequently, the set of claims was new in regards to the document D1 cited by the opponent.

Opponent’s Appeal

The opponent appealed this decision, insisting that a person skilled in the art lacked a clear definition of the term “gathered sheet.” Therefore, according to the opponent, the definition of the term provided in the description was the one to be considered, and that this definition included a rolled tobacco sheet.

In its preliminary opinion, the Board of Appeal considered it was essential to know how to interpret the claims before assessing their novelty.

Although Article 84 of the EPC specifies that claims must be clear and concise and based on the description, there is no provision in the European Patent Convention regarding the interpretation of claims in relation to prior art documents.

Article 69 of the EPC specifies that the scope of protection conferred by the European patent or European patent application is determined by the claims. However, the description and drawings are used to interpret the claims.

There is a Protocol on the Interpretation of Article 69 to clarify how to interpret claims for the purpose of establishing the scope of protection of a patent or patent application. However, Article 69 and its interpretative protocol address the scope of protection of the patent or patent application, not the interpretation of claims when assessing the patentability of an invention.

Two opposing approaches have emerged in the case law of the Boards of Appeal:

• a first approach wherein a definition of a term in the description could not be disregarded to establish novelty in relation to the prior art;
• a second approach wherein the description should only be used in exceptional circumstances to interpret the claims, and that if a term was clear, its use in the description was not justified.

Faced with this conflicting case law, the Board of Appeal referred the matter to the Enlarged Board of Appeal to ensure uniform application of the law.

It is worth noting that the Board of Appeal pointed out that a narrow interpretation of the claim, which ignores the definition provided in the description, could conflict with a broad interpretation by a national court or the Unified Patent Court. In other words, the patent proprietor could defend the patentability of their invention by invoking a narrow interpretation of their claims, and in infringement proceedings, the same proprietor could invoke broader protection under the broader definition provided in the description.

Enlarged Board of Appeal’s Decision

The Enlarged Board of Appeal, after receiving observations from third parties and deliberating, concluded in its decision G1/24:

The claims are the starting point and the basis for assessing the patentability of an invention under Articles 52 to 57 EPC. The description and drawings shall always be consulted to interpret the claims when assessing the patentability of an invention under Articles 52 to 57 EPC, and not only if the person skilled in the art finds a claim to be unclear or ambiguous when read in isolation.

Application of Decision G1/24

Following the Enlarged Board of Appeal’s decision, the case was returned to the Board of Appeal.

In its principal request, the patent proprietor continued to defend its claims as granted and considered that Decision G1/24 referred to a first stage of interpreting the claims as such, and a second stage of consulting the description, but that this consideration must be made by the person skilled in the art who had already considered the claims.

The patent proprietor considered that the description as a whole gave more weight to an interpretation according to which the gathered sheet was not a sheet according to document D1 and that the only contrary teaching in the patent description was confined to the definition in paragraph [0035].

In a subsidiary request, the proprietor removed paragraph [0035] from the description, which contained the definition of a gathered sheet, arguing that this had the effect of restricting the scope of the claim by eliminating the possibility that the sheet could be rolled.

After deliberation, the Board of Appeal concluded in the oral proceedings held on 11 December 2025, the following:

• For the main request, the Board of Appeal applied decision G1/24 and considered that the term “assembled sheet” should be interpreted according to the broad definition in paragraph [0035] and that, consequently, the claim lacked novelty in relation to the prior art document D1 cited by the opponent;
• The subsidiary request was contrary to Articles 123(2) and 123(3) EPC:

1 ) Introduction of a new intermediate generalisation between the old definition and the specific example (contrary to Article 123(2): A European patent application or a European patent may not be amended so that its subject matter extends beyond the content of the application as filed);

2 ) removal of an old restriction implicitly contained in the claim (contrary to Article 123(3): A European patent may not be amended to extend the protection it confers.

The patent was therefore revoked.

Lessons Learned

Although it is always easier to draw conclusions after the fact, it is still possible to learn from such a case to anticipate problems in interpreting ambiguous terms.

When drafting patent applications, we recommended:

• Clearly define the desired protection for your product/process.
• Conduct a thorough search of prior art documents.
• Analyse the prior art documents found to position your invention in relation to these documents and to anticipate any objections regarding lack of clarity, novelty, or inventive step;
• Clearly define each term and ensure consistency between the description and the claims.
• Check that each term is not subject to different interpretations.
• Provide a precise description of the essential features of the invention, preferably with the help of drawings. In the present case, the sheet, whose shape seemed to be an essential feature, could have been more clearly detailed and represented, making it easier to distinguish from the prior art.
• Use broad terms that can cover several possibilities and have, for each broad term, one or more fallback positions (in the text or in the claims) converging towards the solution that will be implemented in practice. For example: “a gathered sheet” could have been defined as a sheet of tobacco material rolled, folded, or otherwise compressed or tightened substantially transversely to the cylindrical axis of the stem, preferably a sheet of tobacco material comprising at least one fold.