Patent Infringement After Duncan Parking Technologies: Doctrine of Equivalents, Claim Construction

Description

Patent practitioners strive to secure valid and enforceable U.S. patent claims that have the scope intended by the inventor, whether in litigation or before the Patent Trial and Appeal Board (PTAB). To this end, it is sometimes desirable to have claims, even independent claims, of different scopes. In practice, claim construction--based on the specification, the language of the claims themselves, and the prosecution history (Phillips)--is often determinative of infringement.

Drafting patent claims and specifications to secure infringed claims is not easy. Care is to be taken throughout prosecution, from the initial drafting to the winning arguments to the examiner, to obtain claims of varying scope, as desired. Counsel and clients must envision what competitors are likely to do and how to prove infringement. Leaving the public unsure of whether their activity is infringing or not can lead to an invalid or unpatentable claim for indefiniteness.

Sometimes, however, the claim is definite, but the claim construction frustrates a patent owner by leading to a conclusion that the claims are narrower than desired. Our review will identify pitfalls. For example, in Duncan Parking Techn. v. IPS Group (Fed. Cir. 2019), the Federal Circuit limited the claims to the patent's preferred embodiment. It declined to apply the doctrine of equivalents, concluding the allegedly infringing device did not work in the same way as the claimed invention. Duncan Parking also reinforces the timeless wisdom of Wahpeton Canvas Co. v. Frontier (Fed. Cir. 1989); if independent claims aren't infringed, very rarely are claims dependent thereon infringed either.

Generally, if the claims, as construed, do not cover the inventor's preferred embodiments, such claim constructions are not favored. Indeed, in Duncan Parking, the Federal Circuit found the district court had improperly read the preferred embodiment out of a different independent claim and deprived the patent owner of the "full scope of its claim language." But, we will also discuss cases where the claims do not cover the preferred embodiments.

Prosecutors should ensure that, if desired, the broadest independent claim covers more than the preferred embodiment--that other disclosures from the specification support it. As noted above, Wahpeton may work to severely limit claims if the most comprehensive independent claim covers only a single embodiment. The patent practitioner should strive that each independent claim recites only that which is required to practice the invention. Unnecessary limitations may inadvertently narrow patent rights for independent claims and all claims dependent thereon.

Listen as our authoritative panel of experienced patent attorneys examines the law of infringement, both literal and the doctrine of equivalents, and claim construction and prosecution estoppel/prosecution history estoppel. The panel will discuss the lessons learned from Duncan Parking and patent prosecutors' impact on later claim construction.