April 17, 2019

Federal Circuit Gives a Master Class in Claim Construction

By Bryan K. Wheelock, Principal

In E.I. du Pont de Nemours & Co. v. Unifrax I LLC, [2017-2575] (April 17, 2019), the Federal Circuit affirmed the district court’s determination that the claims of U.S. Patent No. 8,607,926 on a Composite Flame Barrier Laminate for a Thermal and Acoustic Insulation Blanket were not invalid and were infringed.

The ’926 patent claims composite laminates that are incorporated into thermal-acoustic blankets installed on the interior of airline fuselages to shield passengers from flames and reduce noise. At issued was the term “100% by weight” in the claims. Unifrax argued that the “100% by weight” term does not allow for any amount of organic additives in the refractory layer. According to Unifrax, “‘100%’ means one hundred percent.” The Federal Circuit considered whether the context of the entire patent and other intrinsic evidence supports such an interpretation and concluded it did not.

The Federal Circuit began with the language of the claims:

That claim 1 recites a residual moisture content of up to “[10%] by weight” in addition to “100% by weight” platelets in the refractory layer undercuts Unifrax’s plain meaning argument that “‘100%’ means one hundred percent.” Unifrax’s position would require that the term “100% by weight” be considered alone, without reference to the surrounding claim language. The claim’s reference to both “100% by weight” platelets and 10% residual moisture, however, supports the conclusion that “100% by weight” is relative to carrier material. It would be nonsensical if the total percentage of components comprising the inorganic refractory layer exceeded 100%.

The Federal Circuit then turned to the specification, which described “preferably at least 85% of the layer comprises platelets” with the remainder being “some residual dispersant.” The Federal Circuit found that this language supports the district court’s conclusion that the disclosed embodiments, including the 100% platelet embodiment, allow for some amount of residual dispersant.

Unifax argued that all 24 of the examples had 100% by weight inorganic platelets with no residual dispersant, but the Federal Circuit noted that the specification also listed other “suitable materials” that contain a residual dispersant, and thus, less than 100% inorganic material for the refractory layer.

The Federal Circuit also rejected Unifax’s argument that it was improper to use the specification of the patent’s parent in construing the claims in the continuation-in-part patent at issue, noting that the subject matter in the parent was common to the continuation-in-part application.

Finally the Federal Circuit rejected the argument that the patent owner limited the scope of the claims during prosecution. During prosecution the patentees amended the claims to add the 100% limitation to distinguish prior art with a 70% concentration. The Federal Circuit found that in making the amendment, the patent owner did not disclaim the presence of non-carrier materials such as dispersants.

Based upon the claim language itself, the specification, the specification of related cases, and a careful examination of the prosecution history, the Federal Circuit concluded that the district court’s interpretation of “100% by weight” was not erroneous.

Having affirmed the district court’s claim construction, the Federal Circuit went on to affirm the finding of infringement.

Takeaway

The case was a tutorial in claim construction, giving a practical example of how claim terms are construed in light of the surrounding language, how the entire specification and not just the examples are used in determining the meaning of claim terms; how the specifications of related applications are used in determining the meaning of claims terms; and even how the prosecution history is used in determining the meaning of claim terms.