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Doctrine of equivalents

Definition : Doctrine of equivalents

The doctrine of equivalents in patent law is a principle that allows the scope of protection of a patent law to be extended beyond the exact wording of the patent claims as written in the patent. In other words, even if a product or process is not exactly described by the terms of the patent claims, it can still be considered to infringe the patent if it is equivalent to what is claimed. The doctrine of equivalents is based on the idea that the patented invention protects the technical essence of the invention, and not just its literal description. If a person uses a solution that, although not identical to the claimed solution, functions in the same way and obtains the same result in a substantially equivalent manner, this may constitute an infringement. The application of the doctrine of equivalents varies from one jurisdiction to another, but in general, for an element to be considered equivalent, three criteria are often examined :
  1. Equivalent function: The substitute element in the infringing product or process must perform the same technical function as the element described in the patent claims.
  2. Equivalent means : The substitute element must use a different means or mechanism, but one that is “equivalent” to that of the patent, in the sense that it provides the same technical solution.
  3. Equivalent result : The infringing product or process must produce the same result as the patented invention.

There are significant limitations to the application of the doctrine of equivalents :

  • The test of the person skilled in the art: The central question is to know if a “person skilled in the art”, i.e. an expert in the technical field, would have recognized that the substitute element in the product or process is equivalent to the element described in the patent.
  • The disclosure and scope of the claims : If the equivalent element was already known and visible to the person skilled in the art at the time the patent was drafted, it cannot be used to extend protection by the doctrine of equivalents.
  • “Scope of protection” doctrine : The doctrine must not allow the protection of a patent to be extended excessively, i.e. beyond what the inventor could legitimately have obtained on the basis of his claims.

The doctrine of equivalents therefore makes it possible to protect the invention against imitations which, although they do not reproduce the claimed solution in an identically worded manner, provide an equivalent technical solution. It aims to prevent counterfeiters from finding loopholes by making small modifications to the patented invention that do not alter its overall technical impact.

In short, this doctrine is essential for maintaining robust protection of inventions while allowing a certain flexibility in the application of patents.

For a detailed analysis, see our article The doctrine of equivalents in patent law: a comparative law approach and key case law.