Open-ended range claims as seen by the Boards of Appeal of the European Patent Office (02/2014)

Open-ended numerical range wording in product claims are common practice in many fields of technology. Examples are features with wording like “at least 20% of…”, “up to 500ml”, i.e. numerical ranges which are open at least one end of the numerical values.

1. Background:

The latest developments of the decisions of the Boards of Appeal of the European Patent Office have shown that the Boards of Appeal take a more and more severe view as to such language in view of Art. 83 EPC (European analogy of the enablement requirement in the US).

Art. 83 EPC (European Patent Convention) reads:

Disclosure of the invention
The European patent application shall disclose the invention in a manner sufficiently clear and complete for it to be carried out for a person skilled in the art.

While Art. 83 EPC relates to the requirements during the examination stage of pending European patent applications, the corresponding ground for opposition Art. 100(b) has a similar wording.

Relevant decisions of the Boards of Appeal of the EPO:
The issue with open-ended numerical ranges essentially stems from the fact that the requirements of Art. 83 EPC have to be met over the entire range of protection.

2.1 Requirements of Art. 83 EPC have to be met over the entire scope of protection:A landmark decision as to the applicability of Art. 83 EPC to open-ended numerical ranges in product claims is T409/91. This decision related to a claim having the following wording:

Distillated fuel oil … which has a wax content of at least 0.3wt% at a temperature of 10 degrees centigrade below the wax appearance temperature, the wax crystals at that temperature having an average particle size less than 4000nm.

The application did not contain any disclosure enabling a skilled person to obtain fuel oils of the claimed type containing wax crystals of an average particle size of less than 1000nm. The Board decided that the requirements of Art. 83 EPC were not met, as the disclosure of the invention did not allow the person skilled in the art to perform the invention in the whole range that is claimed.

A further case T1008/02 referred to absorbent materials to be used e.g. for diapers. The claim wording assessed by the Board of Appeal had been as follows:

An absorbent composite comprising a porous fiber matrix and an amount of super-absorbent material…
characterized in that said super-absorbent material can absorb at least 27ml/g of an aqueous solution of ….

The Board construed the claim such that “at least 27ml/g” did not impose any upper limit as to the claimed range. No evidence had been produced by the patentee that at the priority date of the patent, other super-absorbents were directly available to the skilled person which met the remaining requirements of the claim and provided an absorption value considerably higher than the claimed minimum value of 27ml/g. Therefore, the Board decided that the patent did not disclose the invention over the entire range claimed and, consequently, the requirements of Art. 83 EPC were not met.

2.2 Claim construction can lead to inherent limitation of the open-end:
The decision T1018/05 gives particular guidance as to the importance of the scope of protection and Art. 83 EPC. In the Board’s view the principle that the requirements Art. 83 EPC have to be met over the entire scope of protection is not to be understood as also referring to those embodiments literally covered by the claim but which the skilled person would exclude as being outside the scope of “practical application of the claimed subject-matter” as the skilled person would construe the claim as not extending to those variants. This is the case with open-ended range claims if it is clear for a skilled person that the open-ended range is limited in practice. Such a claim must be seen as seeking to embrace values of the parameter as high as can be attained above a specified minimum level.

3. Situation in the US:
In a decision by the Federal Circuit, MagSil Corp. v. Hitachi Global Storage Tech., Inc., in 2012, the Court decided on the following product claim wording:

A device forming a junction having a resistance comprising:
a first electrode having a first magnetization direction,
a second electrode having a second magnetization direction, and
an electrical insulator between the first and second electrodes, wherein applying a small
magnitude of electromagnetic energy to the junction reverses at least one of the magnetization directions and causes a change in the resistance by at least 10% at room temperature.

The Court held that the asserted claims were invalid as a matter of law for lack of enablement. The Court found that the open-ended range recited in the independent claim was not enabled because the disclosure provided support for only a small portion of the claimed open-ended range.

4. Prepare fall-back positions for open numerical ranges in product claims:
Obviously, one conclusion of the above cited decision T 409/91 and T 1008/02 is that there should be fall-back positions (dependent claims, description) which allow to limit an open-ended range claim to a claim in which that feature is limited at both ends. This might, however, lead to difficulties if the absolute limit at a lower end or an upper end of a numerical range, which can be achieved with the disclosure of the invention cannot be expressed in hard values.

5. Can product-by-process also be a fall-back position to save open-ended range issues?
The Board of Appeal decision T 1947/11 hints at such a possibility-, which actually is a concrete implementation of the principles laid down in the above-cited T1018/05.
Claim 1 of the underlying European patent had the following wording:

Low-fat confectionery product obtainable by process of claim X consisting of a water-in-oil emulsion comprising up to 20% fat phase…

The opponent had pointed out that “up to 20% fat phase” constitutes an open-ended range wording.
At the same time the opponent established that there are certain low values as to the fat content which did not

use the technology disclosed in the opposed patent
produce a stable water-in-oil emulsion.
On the other hand, the opposed patent disclosed a process which allows obtaining a product having a stable water-in-oil emulsion having a fat phase content falling within the scope of protection, i.e. up to 20%. The examples demonstrated that values substantially lower than 20% could be achieved by the disclosed process.

The Board of Appeal decided that the product-by-process wording “obtainable by process of claim X” constitutes an inherent limitation of claim 1, i.e. claim 1 in the Board’s view is limited to a minimum fat phase amount obtainable by the process of claim X.

Therefore, a product-by-process wording may represent an additional possibility to fall-back positions expressed in hard numbers, in order to preempt problems as to Art. 83 EPC in the examination stage, or later on in the opposition stage.

Claims with open-ended numerical ranges can lead to a conflict with the requirements of Art. 83 EPC
Therefore it is highly advisable to prepare fall-back positions to “close” the open end

A further approach to resolve such a conflict is to argue that the skilled person would construe the claim not in an open-ended manner, but as the open end inherently having a practical limitation

One specific implementation of the latter approach can reside in a product-by-process wording.

By Christian Rupp

Christian Rupp is a partner of Mitscherlich and has experience of more than 230 opposition cases at the EPO in a wide variety of technical fields.