Means-plus-function claiming under 35 U.S.C. § 112(f) remains a powerful drafting tool for patent applicants and litigants, but it carries significant risks. While the statute permits a claim element to be defined by the function it performs rather than by specific structure, the claim is limited to the corresponding structure disclosed in the specification and its equivalents. When the specification fails to disclose adequate corresponding structure, the claim may be held indefinite and therefore invalid.
The Federal Circuit’s decision in Gramm v. Deere & Co., No. 2024-1598, slip op. (Fed. Cir. Mar. 11, 2026), reinforces that courts must identify corresponding structure by focusing on the function actually recited in the claim—not additional functionality described elsewhere in the specification. The decision is particularly relevant for patent owners and accused infringers litigating software- or controller-based claim limitations.
Means-Plus-Function Claiming and Indefiniteness
Section 112(f) permits a claim element to be expressed as a “means” for performing a specified function without reciting supporting structure. In exchange for this flexibility, the claim “shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.” 35 U.S.C. § 112(f). If the specification fails to disclose sufficient corresponding structure, the claim is indefinite and therefore invalid.
The Federal Circuit’s en banc decision in Williamson v. Citrix Online, LLC established the modern framework for analyzing means-plus-function limitations. 792 F.3d 1339 (Fed. Cir. 2015) (en banc). Although there is a presumption that § 112(f) does not apply when a claim does not use the word “means,” that presumption may be overcome if the claim term fails to recite sufficiently definite structure or merely recites a function without adequate structural support.1 In particular, Williamson recognized that generic or “nonce” words—such as “module,” “mechanism,” “device,” “element,” and similar placeholders—often do not connote sufficiently definite structure to a person of ordinary skill in the art and may therefore invoke § 112(f) despite the absence of the word “means.”
Once § 112(f) applies, courts undertake a two-step inquiry: first, identifying the function recited in the claim; and second, determining what structure disclosed in the specification corresponds to that function. The Federal Circuit has explained that the intrinsic evidence must “clearly link[] or associate[]” the disclosed structure with the claimed function. Williamson, 792 F.3d at 1352.
Particular challenges arise when the disclosed structure includes a computer or microprocessor. Under WMS Gaming, Inc. v. International Game Technology, where the disclosed structure is a computer or microprocessor programmed to perform the claimed function, the corresponding structure is limited to the algorithm disclosed in the specification. The Federal Circuit has explained that a general-purpose computer may be programmed in many different ways, and therefore an algorithm is required to provide the corresponding structure necessary under § 112(f). Failure to disclose the required algorithm can render a claim indefinite.
Importantly, an algorithm need not be disclosed in source code. A description of the steps performed, expressed in words, may be sufficient if it would convey adequate structure to a person of ordinary skill in the art.2
At the same time, the Federal Circuit has repeatedly cautioned against importing limitations from preferred embodiments or other portions of the specification into the means-plus-function analysis. As the court explained in Williamson, corresponding structure is limited to that which performs the claimed function and its equivalents—not additional features disclosed elsewhere in the specification. 792 F.3d at 1347.
The Federal Circuit’s Decision in Gramm v. Deere
The patent at issue in Gramm concerned a system for maintaining a crop harvester header at a designated height above the ground. After related litigation and inter partes review proceedings, the dispute before the Federal Circuit centered on a claim limitation reciting a “control means” for raising and lowering the header in response to sensor input.
The parties agreed that the limitation invoked § 112(f) and further agreed that the claimed function was raising and lowering the header to maintain a designated height above the soil. The dispute arose during the second step of the analysis—identifying the corresponding structure.
The specification disclosed a controller interface, a head controller, and a hydraulic control system. It further stated that, in one embodiment, the head controller was incorporated into a Deere combine and was “conventional in design and operation.” The record reflected that several commercially available Deere controller systems existed at the relevant time, including one version that used circuitry to control header height and later versions that used microprocessors.
Deere argued that only the microprocessor-based controllers qualified as corresponding structure because the specification described controlling both header height and lateral position. According to Deere, the circuitry-based controller could not be corresponding structure because it lacked the ability to control lateral positioning. In other words, Deere sought to limit the corresponding structure to embodiments capable of performing both the claimed height-control function and the unclaimed lateral-position function. Because the microprocessor-based controllers would require disclosure of an algorithm and the patent did not disclose one, Deere argued that the claim was indefinite.
The district court accepted Deere’s position and held the claim invalid.
The Federal Circuit reversed. Applying the two-step framework articulated in Williamson, the court first identified the claimed function and then determined the structure disclosed in the specification that corresponded to that function. Gramm, at 8–10. The court emphasized that the claimed function was limited to raising and lowering the header. Although the specification discussed lateral-position control, that functionality was not recited in the claim. The court concluded that the district court improperly relied on an unclaimed function when determining corresponding structure. In doing so, the Federal Circuit relied on prior precedent rejecting efforts to narrow corresponding structure by importing unclaimed functionality from the specification.
The key point was that a disclosed structure is not excluded merely because it performs fewer functions than other embodiments described in the specification, so long as it performs the function actually recited in the claim. Because the circuitry-based controller performed the claimed height-control function, it qualified as corresponding structure.
That conclusion proved dispositive. Unlike the microprocessor-based embodiments, the circuitry-based controller did not trigger the algorithm-disclosure requirement applicable to computer-implemented means-plus-function limitations. The Federal Circuit noted that the rationale underlying the algorithm-disclosure requirement does not apply where the claimed function is implemented through circuitry rather than a general-purpose computer or microprocessor.3 As a result, the court held that the claim was not indefinite and reversed the judgment of invalidity.
Practical Takeaways
For patent prosecutors and litigators, Gramm offers several practical lessons.
First, practitioners should be deliberate when deciding whether to invoke § 112(f). Although means-plus-function claiming can provide flexibility and may help distinguish prior art, it also ties claim scope directly to the specification and may create indefiniteness risk if corresponding structure is not adequately disclosed. Generic or “nonce” terms such as “module,” “mechanism,” “device,” or “component” may unintentionally trigger § 112(f) if they fail to convey sufficient structure.
Second, specifications involving computers, processors, or software should describe not only the components that perform a claimed function, but also the steps or logic by which the function is performed. Although an algorithm need not be disclosed as source code, the specification should provide sufficient detail regarding how the claimed function is performed. Failure to do so may leave the claim vulnerable to an indefiniteness challenge if the limitation is later construed under § 112(f).
Third, Gramm reinforces that corresponding-structure analysis must remain tethered to the claimed function. Courts should not import additional functions from preferred embodiments or other portions of the specification when determining whether adequate structure exists. A disclosed structure need only perform the function recited in the claim.
Finally, the case serves as a reminder that multiple embodiments can provide corresponding structure. Even if one disclosed embodiment would be inadequate because it depends on an undisclosed algorithm, another embodiment that performs the claimed function without requiring algorithmic disclosure may be sufficient to preserve validity.
Gramm underscores that § 112(f) analysis remains highly claim-specific. For prosecutors, the decision highlights the importance of aligning claim language with disclosed structure. For litigators, it provides a useful reminder that indefiniteness arguments must remain tethered to the function actually claimed.
About the Authors
Alena Vackova Marconi is a shareholder in Brooks Kushman’s Patent Prosecution practice, focusing on domestic and foreign patent prosecution in the chemical, materials science, green tech, and mechanical arts. She counsels clients of all sizes on patent portfolio management and strategy, with experience spanning polymers, coatings, fuel cells, batteries, catalytic converters, packaging, additives, and environmental remediation. Alena’s technical background is especially valuable to clients in the Automotive and Mobility Brands & Technology, Battery Technology, Chemistry & Chemical Sciences, and Green Technology & Sustainable Solutions industries. She holds a B.S. in Chemistry and Materials Technology from Tomas Bata University, an M.S. in Chemistry from Oakland University, and a J.D., magna cum laude, from Western Michigan University Cooley Law School.
Patrick F. Leonard is a registered patent agent in Brooks Kushman’s Patent Prosecution practice, focusing on the preparation and prosecution of patent applications relating to vehicle systems, internet software, and lasers. He brings more than 30 years of experience designing and developing sensor systems for medical imaging, military applications, and industrial processes, including work as a Senior Staff Scientist at Electro Scientific Industries and as founder of Dark Data LLC. Patrick’s technical depth is especially valuable to clients in the Automotive and Mobility Brands & Technology, Electrical & Computer Technology, and Information Technology Services & Software industries. He holds bachelor’s and master’s degrees in Computer, Information, and Control Engineering from the University of Michigan.
Francesca Cusumano-Gibson is an associate whose practice focuses on Intellectual Property Litigation and Patent Prosecution, helping clients protect and enforce valuable intellectual property assets. She advises businesses on patent enforcement strategies and intellectual property disputes involving complex technologies, while also supporting patent portfolio development and protection efforts. Francesca’s technical background in chemistry and experience across industrial technologies make her particularly valuable to clients in the Automotive and Mobility Brands & Technology, Battery Technology, and Chemistry & Chemical Sciences industries. She works closely with clients to develop practical, business-focused intellectual property strategies that align with their innovation and growth objectives.
About Brooks Kushman P.C.
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