The Importance of Specifying Measurement Methods in Your Patent Application

When drafting a patent application, the meaning of each word, value and unit needs to be clear. One might think that a number is less likely to be misinterpreted than a word, but a recent decision from the Boards of Appeal of the European Patent Office (EPO) tells us otherwise. Our Patent Consultant Tiolina Östergren shares the key take aways.

Article 84 of the European Patent Convention (EPC) states that the claims of a patent application shall define the matter for which protection is sought and that they shall be clear, concise and supported by the description. This is to ensure that the scope of protection defined by the claims is clear to any third parties, such that they may determine whether they are working within the scope of the claims or not. In situations where different measurement methods may give different results for a given value of a claimed feature, e.g. size, pH or electrical potential, the claims may be unclear without a specification of the measurement method by which the value was obtained.

Decision from the EPO Board of Appeal

In T0005/17 (30 April 2020), claim 1 of the application in question concerned a mineral “having a mean particle size of between 100 nm and 20 µm”. At first instance, the examining division decided that this did not comply with the requirements of Article 84 EPC, because neither the claim nor the description specified any method for measuring the mean particle diameter. The applicant made several arguments as to why the claim should be considered clear. 

The applicant argued that, while differing results between measurement methods might be relevant in view of very small particle sizes, it was highly unlikely that the measurement methods would give a significant difference for the claimed range. They further argued that there are two commonly known methods for defining particle size for this kind of particle, according to a document cited in the description. As these are acknowledged to be effective in the claimed range, there was no indication that the results would be different. The examining division however found several different techniques in the cited document and no specific argument for why these would yield the same results.

The applicant also argued that the skilled person in this case would be someone using a readily available material. They would not measure the particle size themselves, as they would trust that the material supplier provided an accurate product. The examining division however stated that the skilled person must be familiar with techniques for measurement of the parameters of a claim and that the physical characterisation must be unambiguous and cannot be substituted with information provided by suppliers, which could be based on any available measuring technique.

Furthermore, the examining division stated that the expression “mean particle size” was ambiguous, as “mean” refers to an average, and it was not specified in the claim which type of average (volume, surface, number, etc.) was intended. Whilst this may be regarded as implied by the use of a unit of length (m), this was not deemed sufficient by the examining division as the prior art cited in the application used different units for particle size. 

In addition to T0005/17, a body of decisions from the Boards of Appeal exists regarding reliance on the description and cited documents for interpreting claims. These decisions state that the claims must be clear in themselves when being read by the person skilled in the art, without including any knowledge derived from the description of the patent application. Therefore, a reference in the description can generally not render an otherwise unclear claim clear. This is especially so if the feature in question is required for distinguishing the invention from the prior art.

What can we take away from this?

When drafting a patent application including claims that rely on measured values, it is important to ensure that it is clear what is measured and how. Failing to do so in the drafting stage could lead to a rejection of the whole application. If there is no generally accepted measurement method in the art, or even if there is, it may be suitable to refer to a standard such as an ISO/ASTM/DIN/ANSI/IEC standard or similar, to avoid any uncertainty. It may not be enough to merely refer to another document, especially if there are several measurement methods or units used in that document. No matter how clear the description may be in terms of measurement methods, the claims themselves must clearly specify the characteristics of the matter for which protection is sought.

We would recommend obtaining counsel from a patent attorney if there are any doubts regarding whether or not your application will meet the clarity requirements of the EPO or other relevant patent office.