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The importance of commas

7 February 2023

In a recent decision, T 1473/19, the Board of Appeal of the European Patent Office (EPO) revoked a patent for added matter due to the lack of a single comma in the claims. Patent attorneys are often accused of pedantry when it comes to word selection and grammar. This case is a prime example of why we care so much!

Background of the case

The decision relates to a patent granted for a contactless rotary joint for a CT scanner. During prosecution, claim 1 was amended to add the feature of:

“said [rotary joint] body having a free inner bore holding a capacitive data link”.

Following grant, the patent was opposed on the basis that the above feature contravenes Article 123(2) EPC, which prohibits amendments including subject-matter extending beyond that of the application-as-filed, or “added matter”. Key to the Opponent’s case was the fact that the above phrase could be interpreted to mean that the capacitive data link is held by the free inner bore, rather than by the body, whereas the application as filed has only a single example in which the capacitive data link is held by the body. The Opposition Division disagreed and upheld the patent as granted on the basis that the claim should be interpreted in light of the description and, therefore, should be read as:

“said body, having a free inner bore, holding a capacitive data link”.

The Opponent, however, appealed this decision.

The Board of Appeal, having reviewed the existing law, disagreed.

The Board acknowledged that the interpretation of claims (under Article 69 EPC) indeed requires that account is taken of the description and drawings when interpreting a claim. However, the Board was clear that there are limits to the degree to which the description should be used to interpret the claims. While the description provides context to the claims and can help to make claim interpretation more accurate, the description cannot be considered to have the same weight as the wording of the claims. Only the claims determine the scope of protection. Consequently, in the case of a contradiction between the claims and the description, the words of the claim should be given their normal meaning if the meaning of a claimed feature is understandable on its own and if there is no technical reason to depart from this interpretation.

In this case, the Board was of the view that the feature has two possible interpretations:

  • The capacitive data link is held by the free inner bore; and
  • The capacitive data link is held by the body

The Board agreed with the Appellant that claim 1 should be interpreted in line with interpretation 1), that interpretation being technically sensible and plausible and there being no technical reason to adopt interpretation 2) instead of 1). In view of the disclosure of the application as filed relating only to the arrangement of interpretation 2), the Board concluded that the amendment to claim 1 extended beyond the content of the application-as-filed, contravening Article 123(2) EPC.

The inescapable trap

Not only was the feature deemed to introduce added matter, the Board also decided that there was no way to amend the claim at this stage without contravening Article 123(3) EPC, which prevents claims from being broadened after grant. Were the patentee to amend the claim to include commas and thereby relate to interpretation 2), this would exclude interpretation 1) from the scope of the claims and would, therefore, amount to a broadening of the scope of protection. In other words, the patentee was caught between Article 123(2) EPC (added subject matter) and Article 123(3) EPC (broadening claim scope after grant): the dreaded inescapable trap of Article 123(2)/(3) EPC.

Further, the Board did not allow commas to be added as correction of an error under Article 139 EPC as it was not “an error in a document filed with the European Patent Office”. Interestingly, the offending amendment was actually introduced by the Examining Division in the notice of allowance – Rule 71(3) EPC – communication, which the patentee was deemed to have approved by paying the grant and printing fees.

With no available remedies remaining for the patentee, the decision from the Opposition was overturned and the patent revoked.


This decision highlights the strict approach of the EPO and is a further reminder of the dangers of Article 123(2) EPC objections in Oppositions. If such objections are successful, it can lead to the patentee being caught in a ‘trap’ where the offending feature needs to be removed but to do so will inevitably contravene Article 123(3) EPC.

This decision further illustrates the importance of ensuring that amendments made during prosecution have sufficient basis in the application-as-filed, even (or especially!) if those amendments have been proposed by the EPO. If there is any doubt about whether an amendment might result in added matter, we would recommend erring on the side of caution. This includes pushing back against any amendments proposed by the EPO which might have cause for concern. Even if the concern is as seemingly minor as a missing comma.

Jack Whitfield

Advanced Engineering group

This publication is a general summary of the law. It should not replace legal advice tailored to your specific circumstances.

© Withers & Rogers LLP February 2023