T 1977/22: Can an open-ended range be enabled across its whole scope?

In T 1977/22 the Board of Appeal (the Board ) reviewed the question of the scope of protection of an open-ended range, wherein the Board discussed relevant cases related to the issues at stake. The Board dealt with allegedly divergent case law wherein open-ended ranges were deemed acceptable in some instances and not in others. 

Background

According to common understanding an open-ended range refers to a numerical range that explicitly defines one end value, while omitting the other. The main request of the patent in suit reads as:

1. An inorganic composite oxide material, comprising:

(a)   from 25 to 90 pbw Al2O3; 

(b)   from 5 to 35 pbw CeO2;

(c)   (i) from 5 to 35 pbw MgO, or 

(c)   (ii) from 2 to 20 pbw Pr6O11, or

(c)   (iii) from 5 to 35 pbw MgO, and from 2 to 20 pbw Pr6O11; and

(d)   optionally up to 10 pbw of a combined amount of oxides of one or more dopants selected from transition metals, rare earths, and mixtures thereof, and exhibiting a BET specific surface area:

•    of greater than 150 m2/g after calcining at 900°C for 2 hours; or

• of greater than 85 m2/g after calcining at 1000°C for 4 hours; or
• of greater than 40 m2/g after calcining at 1100°C for 5 hours.

The Opposition Division had revoked the patent for insufficiency of the main request in view of there being no upper limit to the indicated surface areas specified by the claims (feature (d)). The decision was appealed by the proprietor. 

In its preliminary opinion, the Board expressed its view that the invention according to the claims as granted was sufficiently disclosed. The Respondent (Opponent) disagreed, and requested that the question of whether a claimed product including a physical parameter defined by means of an open-ended range satisfied the requirements of Article 83 EPC, be referred to the Enlarged Board of Appeal (EboA). The appellant (proprietor) responded with the submission of auxiliary requests, and the proviso that should any of the requests not meet the requirements of Articles 83 and 123(2) EPC, they agreed that the question, as presented above, be referred to the EBoA. 

The Appeal

The Board first considered that although open-ended ranges were under review, the discussion was equally applicable to ranges with a theoretical upper and lower boundary, such as cases where the purity of a substance is defined as greater than X%, thus limited by a theoretical upper boundary of 100%, and including numerous values very close to 100%. 

General criteria for enablement

The Board considered the general criteria for assessing the requirement of reproducibility of an invention over the whole claimed scope with reference to T 435/91, T 292/85, T 226/85, T 409/91 and G1/03, which have particular reference to claims which define a desideratum (i.e. a result to be achieved, function, or technical effect) using an open-ended range. It was summarized that from the case law, the skilled person should be enabled to achieve the result, the desideratum, over the whole scope of the claim, which is also intended to ensure that the breadth of the claimed invention is commensurate with the technical contribution of the patent. This assessment being carried out on a balance of criteria, such as avoiding unrealistic requirements, while ensuring all essential features for achieving the desideratum are included.

The balance of these criteria in the case law dealing with open-ended ranges and sufficiency of disclosure was discussed largely with an emphasis on the “surrounding circumstances”. 

Additional parameters, examples and common general knowledge

These circumstances were discussed to include additional parameters in the claim, where interrelated parameters or structural features can, in practice, implicitly impose an upper boundary on the open-ended range (T 487/89; T 398/19), in addition to the evidence provided in the examples of the patent. In the latter case, the number of examples included in the application was held to have a bearing on an open-ended range, where in one case, only two products having two parametric values at the lower end of a range were considered to provide insufficient support for defining the invention using an open-ended range (T 1008/02). Analysis of the teachings in the patent as a whole and the common general knowledge were also determined to be relevant when considering if parametric values falling within the open-ended range are achievable. 

Non-working embodiments

The Board considered that the complication is then determining if that information is sufficient to enable the skilled person to reach all, or a reasonable amount of, the parametric values within a range with no specific upper/lower limit. The Board admitted that often claims defining a desideratum encompassed an unlimited number of possibilities (T 292/85) or at least a large number of conceivable alternatives (G 1/03), so an excessively formalistic interpretation would be unrealistic and sufficiency does not require that all non-working embodiments be excluded or that every working embodiment within the scope of the claim be enabled.

Scenarios

Scenario that the open range is not limited

With this in mind the Board presented two scenarios. First, where the element defined in terms of an open-ended range desideratum is not restricted by any structural and/or process features. Such an invention can generally not be enabled, unless it is demonstrated that the open-ended parameter can be easily adjusted within the claimed area using common knowledge. 

Scenario that the open range is limited indirectly by other features

Second, where the claim or the element defined in terms of an open-ended range desideratum is further restricted by structural and/or process features, and without undue burden, the breadth of the open-ended range will be effectively restricted to the values achievable by applying the teachings of the patent and/or common general knowledge. Said ranges are then equivalent to a closed range or have sufficient conceptual limitations. It was also discussed that this view also conformed with the case law the on novelty and inventive step of selection inventions, i.e. claims specifying selected higher parameter values falling within an open range will be novel, and potentially inventive. 

Conclusion on the scenarios

Therefore, the Board concluded that the key criterion for enabling a technically challenging open-ended range desideratum over the whole scope of the claim is the provision of teachings demonstrating that, by operating within the scope of specific (essential) structural and/or process features, the skilled person would be in a position to achieve multiple variants of the invention without undue effort i.e. embodiments with different parametric values falling within the open-ended range. If this condition is met, an invention that defines both the open-ended range desideratum and the essential structural and/or process features required to achieve it may, in principle, be considered reproducible over the whole scope (at least with regard to the reproducibility of the open-ended range itself), irrespective of how far the numerical values can be extended beyond the lower end of the open-ended range. Concluding so, the Board explained that any earlier perceived divergence in the case law was in fact primarily due to case-specific factors. 

Decision of the Board

The Board decided that in the current case, the claims were enabled across their entire scope because of the inclusion of the specific criteria of the claim and the application. It was said that the evidence in the patent thus indicates that the components and concentrations of the metal oxides forming the two shown composite oxides constitute the essential parameters for adjusting and enhancing the specific surface area after calcination to achieve values within the defined range. Moreover, in view of the results in the two examples, the Board is convinced that by making (trivial) adjustments to the components and their concentrations, the skilled person would be able to achieve different parametric values over the open-ended range. The requirement of sufficiency of disclosure under Article 83 EPC was met. The question was not referred to the Enlarged Board and the case was remitted to the first instance for further prosecution. 

Summary written by the NLO EPO Case Law Team