Should I care about the exact wording used in my patent claims? Infringement proceedings: prosecution history estoppel versus doctrine of equivalents?

Exacting wording in my patent claims

In Europe, according to the EPC and its Protocol on Interpretation (Protocol herein after), the claims should be interpreted adopting a balanced approach that combines a fair protection for the patent holder with a reasonable degree of certainty for third parties.

In this perspective, the claims should not be interpreted strictly, in the sense of only the dictionary definition of a certain wording. Conversely, these claims should not be treated as mere guidelines, since the claims play a determinative part in deciding on the patent’s scope. The Protocol thus requires a middle ground between the two extremes to guarantee a balance between fairness to the patent holder and giving the public reasonable certainty as to what the claims actually cover.

Doctrine of equivalents

For the purpose of determining the extent of protection conferred by a European patent, the Protocol further requires that due account shall be taken of any element which is equivalent to an element specified in the claims. This is the so-called doctrine of equivalents. This doctrine can be used by the patentee to claim a broader scope of protection in infringement proceedings.

However, no definition of ‘equivalents’ is given in the EPC or the Protocol. In this view, the World Intellectual Property Organization (WIPO herein after) proposed in its ‘Treaty supplementing the Paris Convention as far as patents are concerned (1991)’ the following definition:

An element (“the equivalent element”) shall generally be considered as being equivalent to an element as expressed in a claim if, at the time of any alleged infringement, either of the following conditions is fulfilled in regard to the invention as claimed:

  1. the equivalent element performs substantially the same function in substantially the same way and produces substantially the same result as the element as expressed in the claim, or
  2. it is obvious to a person skilled in the art that the same result as that achieved by means of the element as expressed in the claim can be achieved by means of the equivalent element.

Hence, it is clear that the scope of protection of a patent claim can be extended beyond the literal wordings of the claims through the application of the doctrine of equivalents.

Prosecution history estoppel (PHE)

The Treaty further describes that in determining the extent of protection, due account shall be taken of any statement limiting the scope of the claims made by the applicant or the owner of the patent during procedures concerning the grant or the validity of the patent, respectively.

Now, the question arises to what extent the above paragraph may impact the scope of protection of a patent?

First of all, patent practitioners generally agree that determining the scope of protection of a patent is one of the most challenging topics in patent law and may often result in points of contention.

In determining the protection scope, a patent proprietor may sometimes adopt an ambiguous attitude. On the one hand, it may occur that a patent proprietor insists on a rather limited and more narrow reading of the claims during patent grant or invalidity proceedings in order to avoid one or more novelty and/or inventive step objections and thereby thus increasing the likelihood of a patent right being granted or maintained. However, on the other hand, it may also occur that the same patent proprietor uses in subsequent infringement proceedings a (much) broader claim interpretation to bring certain allegedly infringing acts within the scope of protection of the patent.

In literature, this principle is metaphorically described as the well-known Angora cat paradox whereby, during patent grant or invalidity proceedings, the patentee first acts modestly with respect to the protection sought, while afterwards when interpreting the patent claims for patent infringement, the patentee tries to recapture subject matter which was initially surrendered during patent grant or invalidity proceedings.

To prevent the patentee from taking such a position, the prosecution history estoppel (PHE herein after) was first established in the US. A PHE may limit a range of infringement available under the doctrine of equivalents. Moreover, according to established US patent practice, the PHE prevents a patentee from using the doctrine of equivalents to recapture subject matter which was initially surrendered during patent grant or invalidity proceedings from the scope of a claim.

Specifically, PHE may arise from a variety of acts taken by the patentee during patent prosecution. For example, it is well settled that claim amendments made in response to prior art rejections can result in PHE. In addition, PHE may also be created by arguments and representations made by the patentee to (foreign) patent offices to obtain allowance of a patent right, even without a claim amendment.

In Europe, there is no direct legal basis in the EPC nor in the Protocol to oblige the national courts of the Contracting States for applying the PHE. Additionally, for most Contracting States, there is no PHE provided under their respective national patent laws.

However, for safeguarding the legal certainty of third parties, the PHE is often provided by national jurisprudence. Indeed, for determining patent infringement, a vast majority of the national courts of the EPC Contracting States, such as the courts of Belgium, France and the Netherlands, may take into account arguments raised by the patentee during patent grant or invalidity proceedings.

Hence, it goes without saying that the use of PHE may play an important role when applying the doctrine of equivalents for determining the scope of protection of a European patent and subsequently deciding on any patent infringement.

After all, a patentee, who has limited the literal scope of protection conferred by claims of a granted patent by filing claims that are more limited in scope during prosecution of the patent application, should have no right during subsequent infringement proceedings to obtain protection for subject matter which he is deemed to have abandoned earlier due to the limitation of scope of the claims.

GEVERS and its highly specialized patent attorneys in various technical fields are available to assist you in strategically building, maintaining, and leveraging your intellectual property assets in line with your business objectives. Furthermore, with concern to (pending) patent rights of (competing) third parties, we are dedicated in providing tailor-made validity, non-infringement and freedom-to-operate opinions, hereby closely considering, when applicable, any relevant claim amendments, statements, arguments and representations made to (foreign) patent offices.

Please do not hesitate to contact us for further information!

Olivier Van Der Poorten

Olivier Van Der Poorten – Patent Engineer