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Claim amendments can affect the doctrine of equivalents

As a patent holder, you have the right to prevent sale, use, or manufacture of a discovery or invention if it employs substantially the same means to achieve substantially the same results in substantially the same way as the limitations recited in your claims.  This is a right you may assert under the “doctrine of equivalents.”   The scope of a patent is not limited to the literal terms, but instead embraces all equivalents to claims described.  See Festo v. Shoketsu, 535 U.S. 722 (2002).

Amendment of your claims during patent prosecution may bar a claim for infringement under the doctrine of equivalents.  Prosecution history estoppel occurs when the claims are amended to avoid prior art or to satisfy requirements of the Patent Act during prosecution of the application.  In other words, if your claims are narrowed to overcome prior art cited by the Examiner, the scope of your patent may be restricted to the exact or literal wording of the amended claims instead of any equivalents.  

Amendment of your claims does not always preclude you from a claim for infringement under the doctrine of equivalents.  The patent holder has the burden of proving that the amendment does not relinquish the equivalent being imposed.  So, when reviewing the draft Office Action Response prepared by your patent lawyer, make sure the scope of the claims adequately cover the invention.   Discuss all claim amendments with your patent lawyer to make sure you are both clear on what coverage is needed and retained throughout the patent prosecution.

Written by
Dan Cotman
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