The Doctrine of Equivalence in Patent Law - A Comparative Study in Different Jurisdictions

Abstract: In the field of patent law, the doctrine of equivalence extends the scope of a patent beyond its literal language to cover inconsequential variations of a patentable invention. This doctrine is arguably one of the most important aspects of patent law. The protection a patent confers is meaningless if its scope is determined to be so narrow that trivial changes to a device bring it out of the bounds of the patent. One of the greatest challenges courts and legislatures therefore face in patent law is to create rules for determining patent scope that maintain the protection a patent is meant to confer while still keeping the patent monopoly within reasonable bounds. Despite the general unity in patent laws among developed countries, the difficulty of this task has led to different results in different jurisdictions. Many jurisdictions have chosen to determine patent scope under a doctrine of equivalence, while others have maintained the position that adequate scope can be found within the meaning of a patent's claim. Even jurisdictions which agree that a doctrine of equivalence should apply differ significantly in its application. This thesis provides an examination of the doctrine of equivalence from the perspective of three different jurisdictions – The United States, Germany and the United Kingdom – and their separate answers to the question of patent scope.