The Historic and Modern Doctrines of Equivalents and Claiming the Future: Part I (1790-1870)

Document Type


Publication Date

January 2004


From its beginning, American patent law has extended patent protection beyond the explicitly disclosed examples of an invention described in a patent specification, applying patents to some range of equivalent substituted technologies. From the middle of the 19th Century until 1950, the Supreme Court was careful to limit this historic doctrine of equivalents to products or processes that physically embody the construed language of a patent's claims. In Graver Tank & Manufacturing Co. v. Linde Air Products Co., 339 U.S. 605 (1950), the Supreme Court radically altered the nature of the doctrine of equivalents, expanding patent protection beyond the scope of application of construed claim language in order to protect the value of patents from alleged fraud. In Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997), and Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002), the Supreme Court extended patent protection under this modern doctrine to later-arising technologies not contemplated by the inventor. As discussed in Part I of this article - forthcoming in the Journal of the Patent and Trademark Office Society - the Supreme Court in 1853 stated that patent protection was limited to the scope of application of construed claim language. In the 1870 Patent Act, Congress codified a "distinct claiming" requirement that should have foreclosed the modern doctrine of equivalents. As discussed in Part II - also forthcoming in the Journal of the Patent and Trademark Office Society - until Graver Tank, the Supreme Court consistently limited the doctrine of equivalents under the 1870 Patent Act to the scope of application of construed claim language. In the 1952 Patent Act, Congress neither codified nor impliedly ratified the modern doctrine of equivalents, and did not extend it to later-arising technologies. This article is the second in a series of articles relating to the doctrine of equivalents. These articles seek to encourage and to set the context for future discussions of abolishing the modern doctrine of equivalents and of claiming later-arising technologies. The first article, to be published in the Federal Circuit Bar Journal, describes conflicts among the modern doctrine and prosecution history estoppel and additional implied disclaimer and claim scope doctrines. It explains how the modern doctrine improperly extends patent protection to equivalents that could not validly be claimed. The third article, to be published in the Berkeley Technology Law Journal discusses the lack of theoretical justification for, social costs of, and complexity created by the modern doctrine. It argues that the historic doctrine of equivalents should be restored and that additional limits on claiming later-arising technologies may be needed to promote progress.