Case Law Review: Volume 11, No. 3
Although “comprising” is typically an open-ended, inclusive term, the Federal Circuit held that claim scope can be narrowed when the specification consistently describes a material in a specific form. In this case, repeated references to elemental tungsten — not tungsten compounds — controlled the construction, rendering the broader PTAB interpretation erroneous. The court nevertheless affirmed the obviousness finding, concluding the error was harmless.