By Chao Peng, Ph.D.
Patent Agent, Burris Law
Functional claim language that recites what a component does rather than defining specific structure or characteristics, is a claim drafting approach used in patent practice. However, the corresponding claim scope is not determined by the claim language alone.
Recent Federal Circuit decisions underscore an important consideration for patent practitioners: similar functional language in claims can lead to different outcomes. The decisions discussed below highlight how the court continues to scrutinize such language through the lens of the claims, the specification, and the prosecution record.
Case Breakdowns: Similar Language, Different Interpretations
Patent claims can employ similar functional language and still receive different treatment during examination.
To understand how this plays out, the decisions highlighted in this article provide useful insight into how context can shape the meaning and scope of such claim language.
In re HBN Shoe, LLC (2026) and In re Blue Buffalo Enterprises, INC (2026)
Two recent Federal Circuit decisions arising from appeals both involve how functional language is treated during patent examination.
In HBN Shoe, the invention is directed to a cleated shoe that allows plantarflexion and eversion during use. The claims recited a structural feature “configured to” permit these movements. The claims were rejected as obvious. The Board’s reasoning suggested that the functional language “configured to” carried limited weight, since the claim does not define key structural parameters. In addition, on appeal, the appellant did not challenge the interpretation of the claim language itself but instead argued that the prior art structure was incapable of performing the recited function. As a result, the functional language was effectively treated as encompassing structures “capable of” performing the claimed function in this context.
In Blue Buffalo, the invention is directed to a packaging container for wet pet food, which includes deformable side walls for food dispensing and a bottom wall with projections for tenderizing the food. The claims were rejected as obvious. On appeal, Blue Buffalo argued that the claim interpretation was overly broad, contending that the claimed components should be understood as being specifically designed to achieve the stated functions, rather than merely capable of doing so. The court disagreed and affirmed the interpretation that the claim language, particularly phrases such as “configured to,” along with descriptions like “readily” deformable and the projections that “allow … to …,” did not impose a requirement of specific design. As such, the court found that the claims could reasonably be interpreted to cover any structure capable of performing the function.
Aspex Eyewear v. Marchon Eyewear (2012)
An earlier precedential decision, Aspex Eyewear v. Marchon Eyewear, also provides useful context for understanding the arguments raised in the more recent cases.
At first glance, Aspex appears to conflict with the recent Blue Buffalo and HBN Shoe decisions. In Aspex, the court interpreted functional language narrowly as requiring a structure “designed specifically for” the recited function. In contrast, Blue Buffalo and HBN Shoe read similar language more broadly to cover structures simply “capable of” perform the recited function.
Aspex involved a magnetic clip-on eyewear invention, where an auxiliary frame attaches to a primary frame using magnetic components. In the claims, functional language “adapted to” is used to describe what the component does.
Here, the Federal Circuit adopted a narrow interpretation for “adapted to”. Looking to the claims and specification, the court found support for reading “adapted to” as requiring components that are specifically designed to accomplish the stated function, not merely capable of doing so. The specification refers to the magnetic members of the auxiliary frame as being “for engaging” with the magnetic members of the primary frame, indicating an intended design rather than capability. In addition, the court noted that adjacent claims used different functional language, including “capable of” and “adapted to”, in a similar context—suggesting that “adapted to” was intended to carry a different meaning from “capable of”. Taken together, these contextual indicators supported construing the phrase “adapted to” as referring to structures “designed or configured to accomplish the specified objective, not simply capable of doing so.”
Key Takeaways and Practice Tips
These decisions reinforce a simple but critical point: the scope of functional claim language is shaped by the context supporting it.
- The functional language may be interpreted broadly as covering structures capable of performing the recited function when the specification and claims lack sufficient structural detail.
- Practice tip: consider a layered claim strategy. In addition to functional language, include claims that recite specific structural features to help define the intended scope.
- Arguments based on a broad, capability-based interpretation to distinguish prior art may undermine a later position that the claims should be construed more narrowly to require specific design or structural features.
- Practice tip: Address claim construction early. If the examiner adopts an unfavorable interpretation, challenge it directly and explicitly or risk being bound by it later.
- Practice tip: Address claim construction early. If the examiner adopts an unfavorable interpretation, challenge it directly and explicitly or risk being bound by it later.
- Using different but similar terms in adjacent claims in a similar context (e.g., “adapted to,” “configured to,” “capable of”) may be interpreted to have different meanings, even if no distinction was intended.
- Practice tip: Be deliberate and consistent when choosing claim terminology. If different terms are used, make sure the distinction is intentional and supported by the specification; otherwise, consider using consistent language to avoid unintended differences in scope.
About Chao Peng, Ph.D. – A patent agent at Burris Law, Chao Peng has more than 15 years of experience spanning scientific research and intellectual property. He earned his Ph.D. in Polymer Science from the University of Akron and has led the development of innovative materials across chemical, biomedical, hygiene, cosmetics, and agricultural industries. Chao has contributed to multiple patents and publications and brings practical experience in patent drafting and prosecution, with a strong understanding of how IP strategy supports business growth and innovation.