The pitfalls of parameters

The European Patent Office (EPO) is well-known for its strict approach to added subject-matter, specifically what the person skilled in the art is considered to be able to derive “directly and unambiguously” from the application as filed. Another, perhaps less well-known, topic where the perceived abilities of the skilled person can hinder applicants and patentees is the use of parameters in claims.

The EPO’s position

The Guidelines for Examination (Part F; Chapter IV; 4.11) set out the EPO’s position regarding the inclusion of parameters in claims:

1. the claims must be clear in themselves when read by the skilled person (not including knowledge derived from the description);
2. the method for measuring a parameter (or at least a reference thereto) must appear completely in the claim itself; and
3. an applicant who chooses to define the scope of the claim by parameters needs to ensure that the skilled person can easily and unambiguously verify whether they are working inside or outside the scope of the claim.

In the absence of a specific definition within the claim, point (ii) may be satisfied if it can be shown that:

1. the measurement method to be employed belongs to the skilled person's common general knowledge, e.g. because there is only one method, or because a particular method is commonly used; or
2. all the measurement methodologies known in the relevant technical field for determining this parameter yield the same result within the appropriate limit of measurement accuracy.

Despite these concession, it is strongly recommended that point (ii) be complied with wherever possible, if only to avoid the later burden of proving that a measurement technique was common general knowledge or that all measurement techniques forming part of the common general knowledge give effectively the same outcome.

Unusual parameters

There are additional concerns for ‘Unusual Parameters’. The EPO considers a parameter to be unusual if (i) it is used instead of a parameter standard in the field, or (ii) it measures a property that was previously unmeasured in the field of the invention.

In the first case, the EPO seeks to prevent applicants from disguising a lack of novelty by redefining features of existing products. To do so, the EPO requires applicants to set out how to convert between the unusual and standard parameter in the application as filed in order to enable a meaningful comparison with the prior art. In addition, should non-accessible apparatus be needed to measure the unusual parameter, the claim will be objected to as unclear regardless.

In the second case, the applicant is required to enable the skilled person to establish the exact meaning of the parameter, to perform the tests needed to measure the parameter, and to make meaningful comparisons with the prior art.

Problems

The principal issue with parameters is that they may introduce a lack of clarity to the claims. If the skilled person cannot “easily and unambiguously” determine whether a product meets a parameter, then the scope of the claim is unclear.

In addition to a potential lack of clarity, parameters may induce a lack of sufficiency and/or inventive step. If the ambiguity surrounding the parameter renders the skilled person unable to identify the technical measures necessary to enact the invention then the claim will lack sufficiency. In the case where the parameter has multiple interpretations, the claim may lack an inventive step if the desired technical effect is not present in any one of the interpretations. These additional considerations are especially important for opposition proceedings where clarity cannot (at least initially) be raised.

Three factors need to be considered when using parameters in claims at the EPO:

What is the parameter that is being defined?

In informal and conversational contexts, many parameters are commonly discussed with truncated terms. For example, in the field of polymers the wordy “weight average molecular weight” (M_w) is often simply referred to as the “mass” of the polymer. However, the latter option is unsuitable for use in a claim as it could be interpreted as being any of the molecular weight measurements, with a typical polymer sample having different values for each. In addition, many applicants employ in-house measurements which they consider to be common, but are unused in more general circles, and so may be considered to be unusual parameters.

How was the parameter measured?

Even if the specific parameter is defined, the parameter can still be unclear if there is no standard measurement technique, or if there are multiple measurement techniques in common use which could give different results. For example, M_w may be determined by Gel Permeation Chromatography or Light Scattering, each giving a different result. Furthermore, certain techniques can give different results depending on the conditions in which the technique is applied. For example, Gel Permeation Chromatography can give radically different results depending on the temperature, solvents, and calibration standards employed.

When was the parameter measured?

Metrology is an active field, with apparatus and techniques being subject to continual refinement. As a result it should be considered whether a measurement technique, or any materials or apparatus it requires, has changed over time such that it produces materially different results. In these cases, a mere reference to the technique is likely to be inadequate. This is a particularly relevant concern for measurements defined by reference to recognised standards (e.g. ASTM or ISO) which are subject to periodic review.

A further complication for inventions defined by parameters is that, should the prior art disclose seemingly relevant products without defining the parameter, as is always the case for unusual parameters, the burden of proof for showing that the disclosed product does not possess the claimed parameter falls on the applicant.

Benefits of parameters

Bearing the above in mind, it is reasonable to question why we want to include parameters in claims at all. Firstly, for certain fields of technology, parameters are difficult to avoid. For example, any invention relating to nanoscience is likely to require a size definition. Secondly, parameters can, in the right circumstances, allow the invention to be differentiated from the prior art in a very clear and effective manner. This is especially true of, and may even be essential for, selection inventions.

Addressing the problems

Avoiding, or overcoming, objections relating to the clarity, sufficiency, and/or inventiveness of parameter claims at the EPO, is usually straightforward if the what, how, and when of the parameter are included in the application:

What – Be clear and precise as to what the parameter is, avoiding generalised terms.

How – Include the method by which the parameter was measured, preferably at different levels of detail by specifying the general technique used before going on to set out more specific details. It may be beneficial, especially for less commonly used parameters, to include the protocol used by the applicant as an example. If applicable, cite the specific industry standard used.

When – Consider if the effectiveness of the measurement technique has changed in the past, or could change in the future, and, if so, include the relevant date or version of any materials, equipment and/or standards used.

The applicant should also be forewarned that, should prior art disclosing relevant products for which the parameter is not defined be discovered, the burden of proof would be on the applicant to provide comparative data demonstrating that the disclosed products do not possess the claimed parameters.

Examples