1 September 2023
by Alex Kelly, Phillipa Makepeace

Patents and parameters - defining European inventions

Alex Kelly and Philippa Makepeace at Gill Jennings & Every LLP on the challenges of defining inventions using parameters in European patent applications.


© Wright Studio / unsplash

Products and processes in the field of chemistry are often defined using parameters – a directly measurable property (for example, the melting point of a substance, the flexural strength of steel, or the resistance of an electrical conductor), or a mathematical combination of several variables in the form of a formula.

Parameters can be useful tools for defining inventions in European patent applications, but they can also present a significant hurdle to obtaining patent protection if sufficient care is not taken when drafting and prosecuting the applications. With this in mind, we review some of the pitfalls associated with parameters and how these can be avoided in your own applications.

Results to be achieved

Essentially, when the value of the parameter is the desired result of the invention (for example, a material having a high ductility of x to y), the inclusion of the value into a claim must be accompanied by all the other features necessary to achieve it. Otherwise, the European Patent Office (EPO) may assert that the application simply claims the problem the inventor was looking to solve, without providing any details of the solution, such as the specific components of the material or the manufacturing conditions that achieve the claimed parameter. Of course, depending on the facts, it may not always be possible to define an invention more precisely without unduly limiting the scope of the claims. However, this needs to be carefully assessed on a case-by-case basis to ensure that there is not unallowable overreaching with respect to the scope of protection being sought.

Ill-defined parameters

When defining the scope of a claim using a parameter, the EPO requires that a skilled person be able to easily and unambiguously verify whether they are working inside or outside of the scope of the claims.

To help avoid potentially fatal clarity objections, it is therefore vital to ensure that parameters are precisely defined and accompanied by a complete and unambiguous method for measuring them – up-to-date reference standards such as ISO or ASTM standards are particularly beneficial.

In fact, if a parameter is so ‘ill-defined’ that the skilled person is not able to identify the technical measures necessary to solve the problem underlying the application without an undue burden, this can even lead to sufficiency problems.

Unusual parameters

European patent practice accounts for ‘unusual’ parameters. These may arise if an inventor frames an invention in an alternative way to that which is generally recognised, or technology development presents a new property that has not been measured before in the technical field of the invention. For both types of ‘unusual’ parameter, the fundamental question is whether enough information is provided to enable a meaningful comparison with the prior art.

When the parameter frames an invention in an alternative way, is there a straightforward conversion that can be made between the ‘unusual’ parameter and the generally recognised parameter? When a new property, not measured before in a particular field, is recited, can it be established that a skilled person would face no difficulty in realising the exact meaning of the parameter using the information presented in the patent, and be able to make a meaningful comparison with the prior art? These questions need to be considered when drafting an application to ensure sufficient information is included to meet the clarity requirements of the EPO.


Fundamentally, a parameter cannot be used to disguise a lack of novelty. If prior art discloses all the other features of a claim, the EPO will likely consider the parameter to be implicitly disclosed, even if it is not explicitly stated in the prior art, or it was not known at the time that the combination of features achieved the stated result.

However, it may not always be immediately clear whether the prior art defines a structurally identical product. For example, it is often difficult to assess the internal structure of alloys based solely on the amounts and identification of the component mixture. In such cases, an assessment of the manufacturing conditions is necessary, and identifying differences with those detailed in the prior art may be beneficial to support your case that the parameter is not implicitly achieved in the prior art.

In summary, the burden of proof that a parameter is a genuine distinctive feature over the prior art ultimately lies with the applicant. It is, therefore, important to ensure that sufficient information is included in a European patent application to support the parameterised innovation and avoid the issues discussed above. Conversely, if you are challenging a competitor’s application or patent claiming a parameter at the EPO, it is worthwhile investigating whether it falls foul of any of the above issues. 

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Alex Kelly

Gill Jennings & Every LLP

Phillipa Makepeace

Gill Jennings