By Christopher Bearne L‘26
On March 18, Vaishali Udapa, USPTO Commissioner for Patents, sent a memorandum entitled, “Resources for Examining Means-Plus-Function and Step-Plus-Function Claim Limitations (35 U.S.C. 112(f))” (“memo”) to all patent examiners. The memo did not introduce any changes in examiner practices but served to reinforce proper examiner procedure for interpreting means-plus-function claim limitations and outline examiner training opportunities.
Means-plus-function claims involve claiming based on functionality rather than structure, by describing a feature by what it does and not what it is. This is often not a preferred claiming method, and has encountered difficulty in the Federal Circuit, especially for computer-implemented inventions. Although, functional claiming is expressly authorized in 35 U.S.C. § 112(f):
An element in a claim for a combination may be expressed as a means or step for performing a specific function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts describes in the specification and equivalents thereof. (emphasis added)
The memo explains a potential benefit to applicants offered by functional claiming: “allowing [applicants] to recite a function in a claim and rely on the specification for the corresponding structure, material, or acts that perform the function and equivalents thereof.” That is, the ability to claim a function without reciting specific means or steps for performing the claimed function[RC1] [CB2] , and instead pointing to “a more robust description of the means or steps in the specification.” This language reinforces the idea that § 112(f) is not meant to allow for broader claiming, but only claims that are supported by the “robust description” in the specification.
The broadest reasonable interpretation (BRI) of a claim under § 112(f) is “limited to the structure, material, or acts described in the specification as performing the entire claimed function and equivalents to the disclosed structure, material, or acts.” This may result in a narrower interpretation than claims not crafted in means-plus-function language. The memo notes this is an important distinction when searching for and applying prior art. As explained below, the memo does not provide examiners with instruction on the exact application of BRI in the § 112(f) interpretation nor the support required for equivalent structures.
The memo also reminds examiners that all claim types, including product and process claims, should be reviewed for means-plus-function limitations because structural elements may appear in both. But how should examiners interpret these claims to determine whether such limitations are present?
To determine whether to apply § 112(f) to a claim limitation, examiners should apply a 3-prong analysis:
(A) the claim limitation uses the term “means” or “step” or a term used as a substitute for “means” that is a generic placeholder (also called a nonce term or a non-structural term having no specific structural meaning) for performing the claimed function;
(B) the term “means” or “step” or the generic placeholder is modified by functional language, typically, but not always linked by the transition word “for” (e.g., “means for”) or another linking word or phrase, such as “configured to” or “so that”; and
(C) the term “means” or “step” or the generic placeholder is not modified by sufficient structure, material, or acts for performing the claimed function.
Claims are presumed to invoke § 112(f) when they explicitly use the term “means” or “step,” but the presumption may be overcome by including further structure for performing the functions in the claim. On the other hand, if a claim does not use such language, it is presumed not to invoke § 112(f), but reciting function “without reciting sufficient structure . . . for performing that function” invokes § 112(f) limitations. According to Williamson v. Citrix Online, LLC, 792 F.3d 1339, 1349 (Fed. Cir. 2015) (en banc), “[t]he standard is whether the words of the claim are understood by persons of ordinary skill in the art to have sufficiently definite meaning as the name for structure.”
The memo noted that there is not an exhaustive list of terms that invoke § 112(f). Instead, examiners must “consider the term in light of the specification and the commonly accepted meaning in the technological art.” For example, “code” or “user interface” may not be generic terms when a person having ordinary skill in the art (PHOSITA) would understand those terms as describing structure, when combined with the function performed. While “module for” and “machine for,” for instance, have been found to be generic terms invoking § 112(f). The memo emphasized, “[e]stablishing the interpretation of § 112(f) limitations in writing during prosecution is critical in supporting the agency goal of establishing a clear prosecution record.” The memo encourages using form paragraphs to explain § 112(f) analysis in a claim interpretation section of the office action. This suggests that examiners may begin to more consistently describe their claim construction methods in office actions, which they traditionally haven’t.
A problem with this guidance, pointed out by Professor Dennis Crouch, is that it lacks instruction on the application of BRI to the first step of determining whether § 112(f) applies. As the memo points out, means-plus-function language could narrow the scope of claims if the corresponding structure and/or equivalents are described in a constricted way, however, if the specification discloses broader or more generic corresponding structures, this could expand the scope of the claim. Examiners may opt to choose whichever interpretation could invalidate the claim or take another approach, but the memo does not provide explicit instruction.
Another potential problem is that means-plus-function claims cover disclosed embodiments and their “equivalents” – but there remains an open question of whether the written description must support the equivalents. In Xencor, the PTO held equivalents must be supported, but the case is now before the Appeal Review Panel following remand from the Federal Circuit. The memo did not provide instruction regarding equivalent structures and their required support in the specification.
The memo does provide instruction on assessing the adequacy of the supporting disclosure. Invoking § 112(f) allows a claim to “recite a function” and rely on the specification to describe the structure performing the claimed function.
The disclosure is evaluated under §§ 112(a) and (b) to ensure definiteness, adequate written description, and enablement. To be definite, the structure must be described in a way that clearly links it to the claimed function and ensures a PHOSITA would understand the structure performs the entire recited function. For computer-implemented claims, “the specification must disclose an algorithm for performing the claimed specific computer function, or the claim should be found indefinite.” This is from the point of view of a PHOSITA, and only disclosing a generic computer as the structure designed to perform a specific computer-implemented function would not be adequate disclosure of corresponding structure.
An indefinite claim under § 112(b) will also fail the written description requirement and may not enable the full scope of the claim under § 112(a). Examiners must apply the usual written description requirement and enablement analysis, to ensure the specification demonstrates possession of the claimed invention at filing and contains sufficient detail to enable a PHOSITA to make and use the claimed invention.
In a press release entitled, “USPTO advances clarity of patent record by tackling means-plus-function and step-plus-function claim limitations,” the USPTO said that clearer communications, “provide both the applicant and the public with notice as to the claim interpretation used by the patent examiner during prosecution, and if the applicant intends a different claim interpretation, the issue can be clarified early in prosecution.” Kathi Vidal, Under Secretary of Commerce for Intellectual Property, Director of the USPTO, and Penn Law alumnus (L’97), stated the guidance is, “part of [the USPTO’s] continued work to create more robust and reliable intellectual property rights on which patent applicants, inventors, and the public can rely and use to build a stronger economy.” The § 112(f) guidance builds on previous § 101 and recently released § 103 guidance “to ensure the USPTO is using consistent interpretations of the law across the agency.”
The USPTO may consider providing additional guidance on the application of BRI when determining whether means-plus-function limitations apply and whether equivalent corresponding structures must be supported by the specification. Comments may be provided to the USPTO here.