The doctrine of equivalents is fundamental for achieving a balance between the rights of patent owners and those of the market. The doctrine forms the basis of the patent system and was codified in the original version of the Protocol on the Interpretation of Article 69 of the European Patent Convention.

Article 69 sets out that the rule on the scope of patent protection:

should not be interpreted as meaning that the extent of the protection conferred by a European patent is to be understood as that defined by the strict, literal meaning of the wording used in the claims, the description and drawings being employed only for the purpose of resolving an ambiguity found in the claims. Nor should it be taken to mean that the claims serve only as a guideline and that the actual protection conferred may extend to what, from a consideration of the description and drawings by a person skilled in the art, the patent proprietor has contemplated. On the contrary, it is to be interpreted as defining a position between these extremes which combines a fair protection for the patent proprietor with a reasonable degree of legal certainty for third parties.

In reality, the point of balance between the two interests in the patent field – namely, providing certainty to third parties on the one hand and ensuring that patent holders are not unreasonably denied or limited protection on the other – can be traced to the following rules:

  • according to the first rule, patent claims must have a meaning that appears appropriate in light of the patent description and prior art (in particular, common general knowledge).
  • under the second rule, the scope of patent protection includes obvious substitutions of elements of an invention, especially in the application of the doctrine of equivalents.

These rules respond to the same rationale – namely, to strike a balance between these two different interests based on the essential role of claims, which are the reference point for third parties. In both cases, an evaluation cannot be carried out in an abstract manner, but should be done concretely, drawing on the knowledge and expertise of a person skilled in the art. This is fundamental for a correct interpretation of the doctrine of equivalents.

Essential and non-essential features

In this context, it is clear that the distinction between an invention's essential and non-essential features must be rejected. This distinction has been used to argue that even the partial reproduction of elements that make up an invention can constitute infringement if the elements reproduced represent the inventive idea underlying the patent. The classic example of this is whether a product (or process) that replicates only features a+b+c of an invention identified by features a+b+c+d constitutes patent infringement.

However, this interpretation – which reconstructs the scope of protection by subtraction, eliminating features even if they are expressly claimed as inessential – is clearly erroneous in light of the rationale mentioned above, as it fails to consider one or more features of an invention, thus eliminating a number of limitations from the scope of protection. As a result, the claim is frustrated, the protection rationale is contradicted and the balance of interests outlined above is not achieved.(1)

Determining equivalence

In order to strike a balance between these different interests, equivalence must be determined based on what a patent owner has chosen to protect. Therefore, this doctrine may extend the scope of patent protection to all solutions equivalent to the idea of said solutions as claimed, not as reconstructed ex post (ie, all solutions implemented through non-inventive substitutions of one or more elements of the invention for which the patent owner has requested protection).(2)

Thus, even in determining the boundaries of counterfeiting for equivalents, patent protection remains anchored to an objective fact that is known to third parties.

These prescriptions would instead be disregarded (and the balance of interests achieved by them would be compromised) if equivalence were evaluated in relation to a supposed general idea of uncertain identification, obtained ex post, rather than the features claimed.

This solution is now codified in the new version of Article 69 of the European Patent Convention (the Protocol on the Interpretation), which aims to meet the need to achieve this balance of interests through the constant reference to claims.

However, these criticisms would appear to conceal a misunderstanding, as the substitution of elements is allowed only insofar as they perform a different general function regarding the solution to the objective technical problem that the invention provides. Therefore, the problem and solution must be expressly considered in the evaluation of equivalence so that the proposed contrast between the element-by-element approach and the consideration of the invention as a whole appears to be artificial and misleading.

In other words, the obviousness of a substitution must be evaluated within the overall framework of the claimed invention, in the sense that the substitution of the feature referred to in the claim must appear obvious in relation to the specific role that the replaced element played in the context of the invention. Whether the substituted feature has an additional function to that claimed is irrelevant. Similarly, where there is a plurality of (obvious) substitutions, it must be clarified whether they allow the same synergy as the elements specifically claimed to solve the problem faced, in line with the problem-and-solution approach used to determine whether a patent implies an inventive step.(3)

Equivalence is therefore determined on the basis of the obviousness of the substitution itself in the eyes of the expert in the field (ie, the same subject used as a parameter for judging the existence of an inventive step). When this happens, it is insufficient to exclude the existence of infringement if the obvious substitution of patented features leads to better (or worse) results in the solution of the technical problem compared with those obtained with the implementation of the invention as literally claimed. However, on the basis of this rationale, patent infringement should be recognised only to the extent that the improvement (or deterioration) achieved involves the patent's implementation – and therefore reproduces, directly or by equivalent means, the features claimed as a solution to the technical problem that is the patent's object – while adding further elements thereto.

These conclusions leave open the question of whether a judgement on the obviousness of a substitution should be made on the basis of the knowledge of an expert when the offence was committed or the patent owner filed the patent application. In Europe, different solutions have been followed in different countries, which creates uncertainty that the Unified Patent Court will have to address.

If an equivalence examination were carried out on the basis of knowledge that arose after a patent application had been filed, protection could also be granted to creations that were made after the application had been filed and which were not part of the patent teaching, thus unduly extending its protection.(4) A variant that was not obvious when a patent was filed could have later been independently patented without giving rise to a relationship of dependence between the two titles, as the second was an alternative solution, albeit with a common part, rather than a derivation. The fact that the patenting process was not carried out (perhaps because, in the meantime, the replacement had been disclosed and it was therefore no longer new) does not permit the owner of the first patent to profit from it, extending ex post the scope of its exclusive right.(5)

Triple test

The above considerations cannot be refuted by applying the so-called 'triple test', which was specifically coined by the US courts for this purpose. Under the triple test, equivalence holds when the substituted element performs substantially the same function in substantially the same way to obtain the same result. If applied in a simplistic way, this test would exclude equivalence in most cases. However, this is not the test's real purpose.

This conclusion is confirmed by US case law on the triple test, which sets out that 'working in the same way' does not mean working in an identical manner (which by definition is excluded when there is no literal infringement). Rather, it means that each element of an invention must be substituted with another substantially equivalent element. If this happens, the allegedly infringing device should be considered to work 'in substantially the same way'.(6)

More generally, in the application of the triple test, it has never been argued that an infringer's introduction of changes to a product or patented procedure alone necessarily implies that it works 'in a different way' and that equivalence should therefore be ruled out. On the contrary, it has been clarified (eg, in German case law) that even if this test is applied, infringement by equivalence exists if the infringer uses "modified but objectively equivalent means".(7) Similarly, US case law has suggested that, in order to decide whether an infringing product or procedure works in the same way as claimed by a patent, it must be ascertained if the substitution is obvious for a person skilled in the art.(8) As a result, this test should focus on the substitution's obviousness, with reference to the technical problem solved by the invention as claimed.


All criteria used to ascertain infringement by equivalence if applied according to the rationale underlying patent protection lead to the same conclusion. Above all, this conclusion outlines a consistent balance between exclusivity and competition. In particular, the problem-solution approach adopted by the European Patent Office, which attributes central importance to the objective problem solved by a patent in assessing inventive step and identifying the priority art relevant for these purposes, is a fundamental tool for objectifying a judgement on inventive step, reducing as much as possible the risk that the ex post knowledge that is inevitably available to those making this judgement will interfere with the investigation. At the same time, the centrality of claims in the assessment of infringement allows each patent to be given balanced protection, rewarding those who have created it, but not hindering those who intend to use the information and ideas contained therein to find alternative solutions and create new progress and knowledge.

From this point of view, the imminent creation (Brexit permitting) of the European Unified Patent Court will be decisive. The establishment of a supranational court, with judges from all EU countries that have joined the system in both the central and regional divisions will be a great opportunity for ensuring uniformity of application and an exchange and comparison of ideas and experiences.

For further information on this topic please contact Cesare Galli at IP Law Galli by telephone (+39 02 5412 3094) or email ( The IP Law Galli website can be accessed at


(1) See Galli, "Per un approccio realistico al diritto dei brevetti", in IDI, 2010, 133 ff; and Franzosi, "Non ovvietà", in Studi Vanzetti, Milano, 2004, 561 ff, who both criticise this approach.

(2) See the Supreme Court of Cassation's decision of 13 January 2004 (257) which stated that:

In order to assess whether the realization accused of counterfeiting can be considered equivalent to the patented one, it is necessary to ask whether, in order to achieve the same final result, it has an original character, offering a non-trivial, nor repetitive, answer to the previous one: and such is the one that exceeds the competence of the average technician who finds himself facing the same problem. Only in this case it can be considered that the solution is outside the idea of a protected solution.

(3) See Galli-Bogni, "L'ambito di protezione del brevetto", in Galli-Gambino, Codice commentato della Proprietà Industriale e Intellettuale, Torino, 2011.

(4) See Court of Rome, 9 September 2004 and Guglielmetti, "La contraffazione del brevetto per equivalenti", in RDI, 2000, I 112 ff.

(5) See Galli-Bogni, "L'ambito di protezione del brevetto", in Galli-Gambino, Codice commentato della Proprietà Industriale e Intellettuale, Torino, 2011.

(6) See for example Pennwalt Corp v Durand-Wayland, which states that:

when an element is entirely missing, that is, when the accused device does not contain either the exact element of the claim or its equivalent, there is no infringement. Conversely, an element is not 'missing' if an equivalent has been substituted.

Further, the Court of Appeals for the American Federal Circuit stated that when "all parts of the invention as claimed have been appropriated at least equivalently can it be found that the accused infringement works 'in substantially the same way" (Pennwalt Corp v Durand-Wayland, Inc, 833 F 2d 949, 1987).

(7) German Bundesgerichtshof decision of 12 March 2002, X ZR 168/00, in GRUR, 2002, 511 et sequitur, and in 34 IIC, 2003, 302 et sequitur.

(8) See the US Supreme Court decision in Graver Tank & Mfg Co v Linde Air Products Co, (339 US 605, 608 (1950). The case entailed substitution of magnesium silicate with manganese silicate – which, unlike the former is not an alkaline-earth metal – while the claim was expressly limited to the latter. This was recognised in the decision as a case of infringement by equivalents.

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