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Recent USPTO Guidance on Claim Interpretation Maintains Course

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On March 18, 2024, the US Patent & Trademark Office (USPTO) issued a memorandum to patent examiners related to resources for examining means-plus-function and step-plus-function limitations under 35 U.S.C. § 112(f).[1] The memorandum seeks to remind examiners of resources available when examining limitations under § 112(f), give applicants and the public deeper insight into the interpretation § 112(f), and emphasize the applicants’ opportunity to define interpretations in the process of drafting claims and specification.  This memorandum also emphasizes the necessity for examiners to create a clear record of the interpretation of the claims.

Using means-plus-function in the claims enables the drafter to claim the functionality of the claim limitation by reciting what the limitation does, rather than what the limitation is.  While a common approach is to draft claims in a way that the claim limitations are given a meaning as they would be understood by one of ordinary skill in the art, a means-plus-function limitation relies on the understanding of one of ordinary skill in the art in view of the specification.  As such, a means-plus-function claim relies on the interpretation solely in view of the structures that define the functionality as described in the specification.  This approach is especially useful when the specification provides different embodiments, where combinations would be hard to capture in the claims without using means-plus-function.  While the means-plus-function language is not necessarily problematic, using such language may potentially limit the scope of the claim to the specific embodiments disclosed in the specification and equivalents.

The first point of the March 18, 2024 memorandum relates to determining whether a claim limitation requires interpretation under § 112(f). The memorandum points out that the first step in determining whether the claim limitation invokes the interpretation under 35 USC § 112(f) is to apply the three-prong analysis outlined in Manual of Patent Examining Procedure (M.P.E.P.) §2181(1). The three-prong analysis requires the use of the term “means,” “step,” or a term used as a generic placeholder for performing the claimed function, the term “means,” “step,” or the generic placeholder being modified by the functional language, and the term “means,” “step,” or the generic placeholder not being modified by sufficient structure, material, or acts for performing the claimed function. More specifically, examiners are instructed to apply interpretation under § 112(f) when the claim limitation explicitly uses the term “means,” “step,” or a non-structural term that is a generic placeholder for performing the claimed function and uses a functional language. Alternately, examiners are instructed not to apply the interpretation rules under § 112(f) when a claim limitation does not use the term “means,” “step,” or the generic placeholder. Additionally, a limitation that recites a function without reciting sufficient structure for performing that function is to be interpreted under § 112(f). 

Although the memorandum emphasizes that an absolute list of the non-structural terms that are considered as generic placeholders does not exist, the practice shows that terms such as “code,” “application,” “program,” and “user interface” are found not to be interpreted as the generic placeholders in cases when a person of ordinary skill in the art would understand the terms as implying the structure when used in combination with the performed function.  However, the terms that, in certain circumstances, may be interpreted as the generic placeholders that invoke § 112(f) are “mechanism for,” “module for,” “device for,” “unit for,” “component for,” “element for,” “member for,” “apparatus for,” “machine for,” and “system for.”

The second point of the memorandum discusses how to clearly communicate on the record when the interpretation rules under § 112(f) have been invoked.  Specifically, establishing the interpretation under § 112(f) in writing during prosecution has been marked a critical task in supporting the USPTO’s goal to establish a clear prosecution record.  As such, the examiners are encouraged to use form paragraphs in which the examiner’s presumptions and clarifying remarks are set forth.  The goal of such an approach is to help with informing the applicant, the public, and the courts on how the examiner interpreted the claim limitations and applied the prior art based on the interpretation.

The third point of the memorandum reiterates the necessity for evaluating the claim limitations, as interpreted under §112(f), in view of the written description and enablement requirements of § 112(a) and the definiteness requirement of § 112(b). With respect to § 112(b), the structure interpreted under § 112(f) needs to be disclosed in the specification in a way that one skilled in the art may understand what structure performs a given function. Examiners are instructed to consider the language in the claims, the specification, and how those of ordinary skill in the art would understand the language in the claims in light of the disclosure. Additionally, in situations in which a claim is ambiguous, examiners are encouraged to further clarify their interpretation on the record. Further, a claim limitation that is found to be interpreted under § 112(f) and indefinite under § 112(b) based on failing to disclose, in the specification, the structure that performs the claimed function, may also fail to be supported by an adequate written description. Such a claim limitation may not be sufficiently enabled by the specification to support the full scope of the claim under § 112(a). Therefore, the examiner is required to perform an analysis to determine whether the specification describes the claimed limitation in sufficient detail to establish possession of the claimed limitation and to enable one skilled in the art to make and use the claimed invention.

Special emphasis is also put on computer-implemented limitations. Specifically, the specification must disclose an algorithm for performing the computer function claimed in the limitation interpreted under § 112(f). The algorithm may be expressed as a mathematical formula, described in prose, in the form of a flow chart, or in any other manner that provides sufficient structure. Providing only a general-purpose computer as the structure designed to perform the function does not qualify as an adequate disclosure to satisfy the requirements under § 112(b).

Although this memorandum serves the purpose of reminding examiners of the available resources and does not provide a change in practice for USPTO personnel, the memorandum may still have useful implications for applicants and practitioners. Specifically, when reciting a function in a claim, applicants and practitioners should ensure the specification contains a detailed description of the structure used to perform the required function. Further, it is desirable to describe in the specification at least two embodiments to support claim limitations. In such cases, during claim construction, the functional limitation can only be “narrowed” so far as it still encompasses both, or all, embodiments—and equivalents thereof. This will avoid scenarios where examiners, or courts, limit the claim to a sole disclosed embodiment, making the claim unduly narrow. 

Having a detailed and precise description of the structure in the specification is important to support the functions claimed and to maintain compliance with the definiteness and enablement requirements while avoiding the pitfalls of § 112(f).


[1] https://www.uspto.gov/sites/default/files/documents/112f-memo.pdf