Before: O'Malley, Reyna, and Hughes. Appeal from the United States District Court for the District of Delaware.

Summary: A parent patent specification of a continuation-in-part child patent constitutes intrinsic evidence for the purpose of claim construction with respect to statements in the parent specification involving common subject matter with the claim terms at issue.

DuPont sued Unifrax I LLC for infringing its ’926 patent covering a flame barrier product. The parties disputed whether the claim term “100% by weight” in the limitation "wherein the inorganic refractory layer comprises platelets in an amount of 100% by weight” allowed for the presence of residual dispersant materials. The district court construed the disputed claim term to allow for the presence of residual dispersant. A jury found the ’926 patent was infringed and not invalid and the district court denied Unifrax’s motions for judgment as a matter of law of non-infringement and invalidity. Unifrax appealed and the Federal Circuit affirmed.

On appeal, the Federal Circuit agreed with the district court's construction of the term "100% by weight." Unifrax argued that the term does not allow for any organic additives in the refractory layer and that the term "100% by weight" meant the platelets are 100% of the inorganic refractory layer based on the plain meaning. The Federal Circuit disagreed based on the context of the patent and other intrinsic evidence. In reaching its conclusion, the Federal Circuit agreed with the district court's finding that a statement in the parent ’027 patent specification explicitly allowing for residual dispersant in the inorganic platelet layer was intrinsic evidence. Although the ’926 patent was a continuation-in-part of the ’027 patent, the Federal Circuit found the relevant excerpt from the ’027 patent specification was common subject matter to the ’926 patent. The Federal Circuit explained that when a parent patent includes statements involving "common subject matter" with the claim term at issue, those statements are relevant to the construction of the claim term in the child patent. The Federal Circuit disagreed with Unifrax's argument that Advanced Cardiovascular Systems, Inc. v. Medtronic, Inc., 265 F.3d 1294 (Fed. Cir. 2001) created a strict requirement that to consider a parent patent as intrinsic evidence, the exact claim term at issue in the child claims must appear in the parent patent's claims.

The Federal Circuit also considered the language of the claims and the specification, which it found supported the conclusion that the claim term “100% by weight” is relative to the carrier material in the refractory layer. Similarly, the Federal Circuit concluded that DuPont did not disclaim embodiments with a refractory layer containing any non-carrier material when DuPont amended the claims to add a platelet percentage term to overcome a prior art rejection.

After adopting the district court’s claim construction, the Federal Circuit found substantial evidence supported the jury's verdict that the patent was infringed and not invalid. Thus the Federal Circuit affirmed the district court’s denial of judgment as a matter of law.

Judge O'Malley dissented, arguing that the construction of "100% by weight" ignores the plain meaning of "100%." Judge O'Malley found the "100% by weight" language coupled to the requirement the platelets are in an inorganic refractory layer means that there can be no organic additives.

This case is: E.I. DU PONT DE NEMOURS & COMPANY V. UNIFRAX I LLC

Edited by: Paul Stewart

Written by: Lindsay Laddaran and Andrea Cheek