A recent Board of Appeal decision (T 0903/24) may change the way European patent practitioners think about reference numerals in claims. Traditionally, reference numerals have been regarded as non-limiting, with the EPC stating that reference signs in claims are provided to increase intelligibility of the claim. However, in this decision the Board relied heavily on reference numerals when interpreting the meaning of a term within a claim, ultimately using them to reject the patentee's narrower claim construction. In doing so, the Board demonstrated that reference numerals can play a more significant role in claim interpretation than many practitioners may have expected.
The legal basis for the use of reference signs is Rule 43(7) EPC, which states:
“Where the European patent application contains drawings including reference signs, the technical features specified in the claims shall preferably be followed by such reference signs relating to these features, placed in parentheses, if the intelligibility of the claim can thereby be increased. These reference signs shall not be construed as limiting the claim.”
Rule 43(7) EPC generally requires reference numerals to be included, unless it can be argued that the numerals would not aid intelligibility. In practice, this can be difficult to argue, and EPO examiners will therefore usually require reference numerals to be added if they are omitted. Reference numerals are therefore included at filing or added during prosecution to improve clarity and facilitate comparison with the drawings. This decision suggests that, whilst reference numerals may not limit claim scope directly, they can nevertheless play an important role in how claim language is interpreted.
The patent concerns a household refrigeration appliance, such as a refrigerator or freezer. More specifically, it relates to the construction of a heat-insulating wall for a refrigerator door.
Conventional refrigerator doors comprise a heat-insulating core positioned between inner and outer door surfaces. During manufacture, thermal stresses can arise due to differing thermal expansion characteristics of the materials used. These stresses can lead to distortion of the door, potentially affecting sealing performance and energy efficiency.
The invention sought to improve rigidity whilst avoiding the cost and thermal disadvantages associated with conventional internal reinforcement structures. The proposed solution involved forming portions of a cladding element from several superimposed layers of the same sheet material arranged at the narrow side of the door.
The patent was opposed. The Opposition Division maintained the patent in amended form. The opponent appealed to the Board of Appeal, arguing among other things that the claims lacked novelty over prior art document D2.
Claim 1 under appeal defined that the door has a heat-insulating wall having opposing first and second main surfaces and a narrow side. A first cladding element, formed from a blank of flat material, extends over the first main surface and the narrow side.
The key feature of claim 1 required that:
“the first cladding element on the narrow side has at least locally several superimposed layers (35, 36, 37) of the flat material.”
The dispute centred on the meaning of “superimposed layers”.
The opponent argued that direct contact of the layers was not required. Pointing to the patent’s own usage in claim 7 and to embodiments shown in Figures 5, 6, and 7, the opponent contended that the term only required a local arrangement of layers on top of each other, even if spaced apart. Layers could still be “superimposed” even if another component was positioned between them, and therefore the spaced-apart layers of the interlocking hooks in D2 anticipated the feature.
The proprietor argued that “superimposed layers” meant layers that were in direct contact with one another and supported one another structurally. Relying on paragraphs [0010], [0015], and [0017] of the patent, the proprietor submitted that this support was necessary to provide the wall with stiffening and dimensional stability against stresses. Addressing the embodiments of Figures 6 and 7, the proprietor argued that the specification avoided the claim's exact term for “superimposed” (which in the original German is übereinanderliegend, implying “lying” and therefore mutual support), describing them merely as being “bent” (übereinander gebogen) or “arranged” (übereinander angeordnet) on top of each other. Under this narrow interpretation, the prior art D2 did not disclose the claimed feature.
The Board first considered the ordinary meaning of the language and concluded that “superimposed” did not inherently require direct contact between the layers.
The Board also rejected the proprietor’s argument that the functional purpose of the layers justified a narrow interpretation. The proprietor had argued that to provide the necessary stiffening and thermal stability described in the patent, the layers had to be in direct contact. However, the Board noted that these technical effects are still achieved by spaced-apart layers with an intervening component, like in D2.
The Board also examined how the phrase was used elsewhere in the patent, paying particular attention to dependent claim 7. While claim 1 concerned layers on the narrow side of the core (identified by reference numerals 35, 36, and 37), claim 7 defined a different strip comprising “several superimposed layers (40, 41, 49)”. The Board noted that the term must be interpreted uniformly in these two claims.
Crucially, in the corresponding embodiment (Figure 6), layer 49 is separated from at least one of the other layers by an intervening component.
The proprietor objected to the Board relying on this, arguing under Rule 43(7) EPC that reference numerals merely identify features in the drawings and must not be used to limit the claim.
The Board disagreed. It drew a clear distinction between using reference numerals to restrict claim scope (which is prohibited) and using them to understand what the patentee meant by their own terminology. By explicitly including layer 49 in that grouping despite it being spaced apart from the others, the Board concluded that the patent's own use of the term "superimposed" did not require direct contact. The Board referred to this as an indirect "retroactive effect"—where the numerals point to a figure, and the figure in turn explains the claim language. According to the Board, this is consistent with the purpose of reference numerals under Rule 43(7) EPC, namely to improve the intelligibility of the claim.
Once the Board concluded that direct contact between the layers was not required, the novelty objection succeeded. The main request was therefore found not novel.
The patent ultimately survived because a further limitation contained in an auxiliary request was maintained.
This decision provides a useful practical application of the Enlarged Board's guidance in G 1/24. The Board emphasised that its interpretation did not arise from the reference numerals alone, but from a combined assessment of the ordinary linguistic meaning, the technical function, the description, the drawings, and the reference numerals.
While Rule 43(7) EPC remains unchanged (reference numerals still cannot be used to restrict claim scope) the decision demonstrates their significant role in claim interpretation. Where a claim term is disputed, a Board may use the reference numerals to link that term to specific embodiments, effectively treating them as evidence of the patentee's own usage of the language.
The practical consequence is that applicants and attorneys must think carefully before adding reference numerals to claims.
Although the reference numerals in this case were present from filing, the decision raises interesting questions about the role of numerals added later during prosecution. It is unclear whether a Board would treat such additions in exactly the same way. Nevertheless, once a patent grants, the claims form part of the approved text, and this decision suggests that any interpretative link created between a claim and a particular embodiment may later become relevant. As claim interpretation evolves following G 1/24, this decision highlights that reference numerals can shape how a claim is understood.