On March 18, 2024, the US Patent & Trademark Office (PTO) issued a memorandum to patent examiners addressing means-plus-function and step-plus-function claim limitations and how to clearly articulate, in the prosecution record, the PTO’s interpretation of such claim limitations. The goal of the memorandum is to ensure consistency in connection with the examination of such limitations, provide both the applicant and the public with notice regarding the claim interpretation used by the patent examiner, and provide the applicant an opportunity to advance a different claim interpretation early in the prosecution.

As stated in 35 U.S.C. §112(f), “[a]n element in a claim for a combination may be expressed as a means or step for performing a specified 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 described in the specification and equivalents thereof.” The memorandum does not suggest any changes in interpretation of the statute.

One aspect of the memorandum is to remind examiners of the resources and guidance available when examining means-plus-function and step-plus-function claim limitations, specifically MPEP §§ 2181-2187 and refresh training. In accordance with the guidance, the primary steps when examining such claim elements include:

• Determining whether a claim limitation invokes § 112(f)
• Ensuring the record is clear with respect to invoking § 112(f)
• Evaluating the description necessary to support a § 112(f) claim limitation under §§ 112(a) and (b).

To determine whether a claim limitation invokes §112(f), the guidance instructs examiners to employ the three-prong analysis set forth in MPEP § 2181, subsection I. Using this analysis, recitation of the terms “means” or “step” in association with functional language, rather than structure, material or acts for performing that function, should be interpreted as claim limitations invoking § 112(f). However, where these terms are accompanied by structure, materials or acts for performing the function, § 112(f) is not invoked. On the other hand, a limitation reciting functional language along with a generic placeholder term instead of “means,” which fails to recite sufficiently definite structure for performing the function, would nonetheless invoke § 112(f), according to a proper analysis. Examples of such generic placeholders include “mechanism for,” “module for,” “device for,” “unit for,” “component for,” “element for,” “member for,” “apparatus for,” “machine for” and “system for.”

An important caveat in the memorandum states that “[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 guidance advises examiners that form paragraphs are available in support of meeting this objective, which serve to inform “the applicant, the public, and the courts . . . as to the claim construction the examiner used during prosecution. This further informs the applicant, the public, and the courts (and the PTO for any post-grant review procedures) as to how the examiner searched and applied prior art based on the examiner’s interpretation of the claim.”

The memorandum further emphasizes the need to evaluate whether claims under §112(f) meet the written description and enablement requirements of § 112(a) and the definiteness requirement of § 112(b). Regarding the latter, the specification must clearly disclose a structure that is clearly linked to or associated with the function, which would be understood by one skilled in the art to perform the entire recited function. Further, “[f]or computer-implemented § 112(f) claim limitations, the specification must disclose an algorithm for performing the claimed specific computer function . . . [and] sufficiency of the disclosure of the algorithm must be determined in light of the level of ordinary skill in the art.”

The memorandum further states that an indefinite § 112(f) claim limitation “based on failure of the specification to disclose corresponding structure that performs the entire claimed function will also lack adequate written description and may not be sufficiently enabled to support the full scope of the claim under § 112(a).” Thus, in any § 112(f) analysis, an examiner must determine whether the specification establishes possession of the claimed invention and whether sufficient information is provided to enable one skilled in the pertinent art to make and use the claimed invention.

For further details, see the memorandum here and the Federal Register notice here.