MEANS-PLUS-FUNCTION CLAIMS: A RETURN TO RELEVANCE?

By Eric L. Maschoff and Mark W. Ford

Some say that trends are like passengers on a carousel: they keep going around. This is particularly true with fashion, where shoes like the Nike Dunk (introduced in 1985) now line the walls of many shoe stores after years of relative retail obscurity. Like the Nike Dunk, patent claims that include at least one means-plus-function limitation also enjoyed a period of popularity before declining. In the late 1980s, more than 50% of issued patents included at least one means-plus-function limitation. Unlike the Nike Dunk, however, the popularity of means-plus-function limitations have not yet seen any sort of comeback. Today, less than 5% of issued patents include such a limitation.

While it is unclear to the authors what inspired the resurgence in popularity of a shoe that we wore in high school, a resurgence in popularity of means-plus-function limitations may be on the horizon due to the Impact Engine, Inc. v. Google LLC case.

History of Means-Plus-Function Claiming

In Halliburton Oil Well Cementing Co. v. Walker[1], the Supreme Court held that a claim that is functional at the point of novelty is, ipso facto, invalid. In response, Congress enacted § 112(f) of the Patent Statute[2], which explicitly enables patentees to express a claim limitation – even at the invention’s point of novelty – by reciting a function to be performed instead of the structure that performs the recited function. These so-called “means-plus-function” (MPF) limitations, however, do not cover all structures, materials, or acts that perform the recited function. Rather, the statute specifies that the scope of a means-plus-function claim is limited to the corresponding structure, material, or acts disclosed in the patent’s specification, and their equivalents. Thus, inventors cannot simply claim any and all possible ways of performing a function—they must describe, in the specification, the specific structures or algorithms that perform the function, and the claim will be limited to those disclosed structures and their equivalents.[3]

Over time, the popularity of MPF limitations declined. This decline has been primarily due to courts’ tendency to (1) narrowly construe the scope of means-plus-function limitations when identifying corresponding structure, and (2) invalidate claims that include MPF limitations when the specification does not adequately identify corresponding structure.

Impact Engine, Inc. v. Google, LLC

The Federal Circuit’s recent decision in Impact Engine v. Google[4] has renewed interest (and some doubt) in the proper treatment of claims containing MPF limitations—including issues relating to patent eligibility and infringement. Interest has intensified in view of Impact Engine’s subsequent petition of the Federal Circuit for en banc review, the outcome of which could vastly alter interest in use of MPF claim strategies.

Impact Engine sued Google alleging infringement of a family of patents that disclose systems and methods for creating, editing, sharing, and distributing media-rich web-based communications such as presentations, banner advertisements, websites, and brochures. At the heart of the dispute are claims that include a “project viewer” element, which the district court construed as a means-plus-function limitation under § 112(f). The project viewer, however, is like a multitool in that it performs several different functions. Indeed, different claims use different “project viewer” MPF limitations to recite four different functions including: (1) rendering a communication; (2) sending a communication; (3) allowing users to view templates; and (4) displaying slides.

The basic approach to construing an MPF claim is to first identify the claimed function, and then identify structure within the specification that is required to perform that specific function. In Impact Engine, the district court identified over 300 lines of disclosure in the specification, which disclosed different algorithms (structures) for performing each of the different recited project viewer functions. Instead of determining which individual algorithm was needed to perform a specific project viewer function, the district court concluded that the entirety of the structure disclosed in the specification was necessary to perform all the various project viewer functions. In other words, if the project viewer was a multitool, the district court’s construction would require the presence of all the multitool structural components (e.g., the knife, the bottle opener, and the screwdriver) regardless of whether the multitool MPF limitation recited a single function, such as “means for cutting.”

After construing the claims in this manner, the district court found one set of project viewer claims ineligible under § 101 based solely on an assessment that the claimed function was directed to a known programing construct and without considering the corresponding structure. The court then found that the remaining project viewer claims were directed to statutory subject matter but were not infringed because Impact Engine’s expert had not shown that the entire 300 lines of structure disclosed was present in the accused device. The expert had instead identified only the particular algorithmic structures from the 300 lines required for the subset of claimed project viewer functions in the accused product. In fact, the court never confronted the issue of whether the accused product included any of the structure—let alone equivalents—identified in the 300 lines of disclosure.

A new future for Means-Plus-Function claims?

In a split opinion, the Federal Circuit affirmed the district court’s rulings. In dissent, Judge Reyna took issue with both the majority’s non-infringement and ineligibility determinations on the basis that they departed from well-established Federal Circuit precedent. He concluded that the district court’s claim construction requiring over 300 lines of structure from the specification regardless of the claimed function was wrong, and this flawed construction necessarily infected the district court’s ineligibility and non-infringement rulings for the “project viewer” claims.

In its petition for rehearing en banc, Impact Engine seeks clarification relating to the patent eligibility of MPF claims. First, it requests that MPF claims limited to specific structure described in the specification be deemed per se patent eligible. Second, and alternatively, that specific structure required to perform a function recited in a MPF claim limitation must be identified before assessing patent eligibility under § 101. Obviously, a Federal Circuit ruling in the affirmative on either of those issues would immediately reinvigorate the patent bar’s interest in means-plus-function claim strategies. In the meantime, there is much to take away from the Impact Engine saga, both in terms of potential advantages of MPF claiming, as well as important practice considerations.

Functional language is often easier to understand. MPF limitations can be useful simply from a practical standpoint, particularly when an invention is complex and claiming structural elements is challenging. A MPF claim limitation can simplify complex elements by focusing on what the element does rather than detailing structural concepts by way of difficult-to-understand claim language. This can be advantageous for a non-technical audience, such as a judge or jury.

MPF limitations can be complementary to structural claims. Using MPF claims alongside structural claims create a more comprehensive claim coverage strategy, adding another layer of protection in the event structural claims face interpretation challenges. Claim breadth can also be maximized. When a supporting specification includes sufficient structural detail, MPF limitations can cover a range of disclosed embodiments, as well as their equivalents.

MPF limitations for software related inventions. When used in the context of software algorithms, MPF limitations can be particularly useful. When a MPF claim is supported by specific algorithms (structure) disclosed in the specification, it highlights the practical, technical implementation of the claimed function. This can show that the claim covers more than just an abstract idea—it covers the way in which the function is achieved, anchoring the claimed function to specific embodiments thereby making it easier to argue that the invention is rooted in a technical field and has a concrete application, distancing it from mere abstract ideas. Impact Engine argues that such evidence should make the claim per se patent-eligible, or at least must be considered before assessing patent eligibility under § 101, which could be helpful in protecting such claims from early dismissal.

MPF limitations help to navigate species restrictions. MPF limitations, by their nature, encompass multiple species or embodiments that perform the same function in different ways. This broader scope can help avoid, or help navigate, restrictions that might arise during prosecution if each species is claimed separately with structural language. At a minimum, use of a MPF limitation might preserve the presence of a generic claim, that might later be used to rejoin restricted species and avoid the need to file divisional applications.

Coverage of “equivalent” structures. Section 112(f) mandates that MPF limitations cover any structure disclosed in the specification, as well as any “equivalents thereof.” This can increase claim breadth: if the accused structure performs the same function and does so in substantially the same way to achieve the same result, it may infringe the claim. Even if an accused structure has differences, it can still be deemed equivalent if those differences do not substantially affect the way the function is performed. This assessment requires factual analysis, technical evidence, and often expert testimony, making it suitable for determination by a jury or fact-finder in a trial setting. Because equivalence involves factual determinations, courts often find that it is not suitable for summary judgment (or dismissal at the pleading stage) if the evidence shows genuine disputes about how the accused structure performs the function or whether differences between structures are insubstantial.

Be clear on your intent to invoke (or not invoke) § 112(f). A practitioner should exhibit a clear intent to invoke § 112(f). To avoid interpretational ambiguity, use trigger language as outlined by the statute itself, specifically “means for” or “step for,” to signal that a claim element is intended to invoke § 112(f). Using these exact terms creates a presumption that the claim should be interpreted under § 112(f). Moreover, clearly articulate a distinct function, and avoid the recitation of any structure needed to perform that function within the claim itself.

            Conversely, a practitioner should avoid any unintentional invocation of § 112(f) if application of the statute is not intended. For example, avoid use of the word means if § 112(f) treatment is not intended. Similarly, avoid use of any so-called “nonce” words—words that do not suggest structure such as “module,” “system,” “unit,” “device,” “software” and the like—that are often interpreted by courts as substitutes for the word “means” and, therefore, can trigger treatment under § 112(f) if only additional function is recited.

Be specific about corresponding structure and be comprehensive. Ensure that the patent specification explicitly links each claimed function to the exact structure needed to perform that function. Impact Engine is illustrative. There, four separate functions were claimed using the same generic claim term: “project viewer.” As such, it was difficult to discern what specific structure was required for a given function. A better approach is to use a separate means-for clause to recite each function, and then specifically align that language to only that structure needed to perform the recited function.

Anticipate equivalence issues. When feasible, include descriptions of known equivalents for the disclosed structures to strengthen the basis for arguing equivalence under § 112(f) during enforcement. Keep in mind the function-way-result (FWR) test when drafting the specification to ensure that disclosed structures and potential equivalents align with this standard. Consult with the inventor, as well as technical experts, to ensure that the disclosed structures are sufficiently detailed and technically accurate, and to identify any known equivalents.

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While we may not all be soon wearing Nike Dunks again, there is the possibility that we again start thinking of drafting at least some claims using means-plus-function limitations. While the outcome of the Impact Engine will be very influential, there are other reasons to consider a possible return to that claiming strategy. Stay tuned and be prepared.

Eric L. Maschoff – Eric co-founded Maschoff Brennan in 2011.  He specializes in building intellectual property portfolios that advance his clients’ business strategies.  Eric provides his clients with advice on the full spectrum of patent portfolio management and strategy as well as IP acquisition and enforcement.

Mark W. Ford -  Mark specializes in representing clients before the United States Patent and Trademark Office in post-grant proceedings. In addition to his post-grant practice, Mark is also an experienced litigator, having represented both plaintiffs and defendants in disputes involving a wide variety of technologies,

About Maschoff Brennan

Maschoff Brennan provides legal counsel and representation to some of the world’s most innovative companies. With over 40 attorneys and offices in the technology-focused regions of Utah, California, and New York, our attorneys are known for having the breadth of experience and the forward-thinking insight needed to handle complex technological and business issues across all industries and geographic boundaries. In addition, we have extensive experience representing clients before the ITC, PTAB, TTAB, and other administrative agencies in Washington D.C.

_{[1] 329 U.S. 1 (1946).}

_{[2] Note that 35 U.S.C. § 112(f) was formerly designated as paragraph 6 of § 112 of the Patent Statute.}

_{[3] 35 U.S.C. § 112(f).}

_{[4] Appeal No. 22-2291 (Fed. Cir. July 3, 2024); not reported in Fed. Rptr., (2024 WL 3287126).}