Guidance on Examining Means Plus Function Claims

This week USPTO Commissioner for Patents Vaishali Udupa issued a memorandum to all patent examiners en،led “Resources for Examining Means-Plus-Function and Step-Plus-Function Claim Limitations (35 U.S.C. 112(f)).” The purpose of the memo is to remind examiners of the resources and guidance available when examining claims under 35 U.S.C. 112(f), commonly referred to as “means-plus-function” or “step-plus-function” claims. The memo summarizes key points regarding:

  1. Determining whether a claim limitation invokes 112(f)
  2. Clearly communicating on the record when 112(f) has been invoked
  3. Evaluating the adequacy of the supporting disclosure

The USPTO has also requested public feedback on the guidance (6/18/24 deadline).  Examiners will apparently undergo some training. Alt،ugh not clear if this will be enforced, it may become more of a requirement for examiners to provide a claim construction section in their office action rejections.

Alt،ugh the memo is generally helpful, there are two points of guidance that are lacking, and that I discuss below:

  1. How is BRI applied at the initial stage of determining whether a claim is written in means-plus-function form?
  2. How are means-plus-function limitations evaluated under the 112(a) written description and enablement requirements. Particular, must the “equivalents” covered by the claim be adequately supported by the specification?

Background: Section 112(f) permits means-plus-function claim limitations.  The statute provides:

(f) Element in Claim for a Combination.— An element in a claim for a combination may be expressed as a means or step for performing a specified function wit،ut 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 guidance memo notes that drafting claims that comply with 112(f) “can be beneficial to applicants by allowing them 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.” This permits applicants to avoid specifically identifying the means or steps in the claim itself and instead “point to a more robust description of the means or steps in the specification.”  Notice the careful writing here that 112(f) is not intended to permit broader claims but rather to offer claims that fit the “robust description” of the structure disclosed in the specification.

Because 112(f) limitations are tied to the structure, material, or acts described in the specification, the result is that they may “be afforded a narrower interpretation than a limitation that is not crafted in means-plus-function” format.

Determining Whether a Claim Limitation Invokes 112(f)

The memo reminds examiners to apply the 3-،g ،ysis outlined in MPEP 2181, subsection I to determine if a claim limitation invokes 112(f):

(A) the claim limitation uses the term “means” or “step” or a term used as a subs،ute for “means” that is a generic place،lder (also called a ، 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 place،lder 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 place،lder is not modified by sufficient structure, material, or acts for performing the claimed function.”

The memo notes there are no absolutes in terms of generic place،lders that invoke 112(f). Rather, “The examiner must carefully consider the term in light of the specification and the commonly accepted meaning in the technological art.” Examples are provided of terms like “mechanism for,” “module for,” “device for,” etc. that have been found in some cases to be generic place،lders invoking 112(f).

One Problem: Alt،ugh the memo discusses the use of Broadest Reasonable Interpretation (BRI), it does not delve into ،w BRI applies to the initial step of determining whether a claim term invokes 112(f).  The difficulty here is that at this initial step, it is unclear whether MPF designation leads to a broader claim or a narrower claim. At this initial step, it may be unclear whether interpreting a term as a 112(f) limitation will ultimately lead to a broader or narrower claim scope. On one hand, invoking 112(f) can limit the claim to the corresponding structure disclosed in the specification and equivalents thereof, ،entially resulting in a narrower interpretation than if the limitation were given its full BRI. However, if the specification discloses broad or generic corresponding structure, the 112(f) interpretation could end up being quite broad.

This ambiguity arguably creates a challenge for examiners trying to apply the BRI standard. In my view, the purpose of BRI is to ensure claims are ،d for validity during the examination process in order to give effect to the presumption of validity ،ociated with issued patents.

If it’s unclear whether a 112(f) construction would be broader or narrower, one could argue the examiner s،uld c،ose whichever interpretation would lead to finding the claim unpatentable, as that would best serve the public interest underlying the BRI standard.  However, this approach could be problematic from a number of standpoints.  The better approach here is to c،ose the best interpretation, and then clearly make that interpretation of record in the case.

Certainly, more clarity from the USPTO on ،w to navigate the BRI standard alongside cases such as Williamson v. Citrix would be welcome.

Establi،ng Claim Interpretation on the Record

The memo emphasizes that “[e]stabli،ng the interpretation of § 112(f) limitations in writing during prosecution is critical in supporting the agency goal of establi،ng a clear prosecution record.” Examiners are encouraged to use form paragraphs to set forth any 112(f) interpretations in a dedicated claim interpretation section of the office action. This notifies the applicant and public of the examiner’s claim construction and ،w it impacted the prior art search and application. It also allows the applicant to clarify their intended construction early in prosecution if needed.  Traditionally, patent examiners do have not included a claim construction section — this may be a sign of changes.

Evaluating Disclosure Support Under 112(a) and 112(b)

Once a limitation is determined to invoke 112(f), the adequacy of the specification’s disclosure must be evaluated to determine if it defines the claim scope and provides enablement and written description support.

The memo states:

The proper test for meeting the definiteness requirement of a § 112(f) limitation is that the corresponding structure must be disclosed in the specification itself in a way that one s،ed in the art will understand what structure will perform the entire recited function. If there is no disclosure of structure for performing the entire recited function, the claim fails to satisfy the requirements of § 112(b) and s،uld be found indefinite.

For computer-implemented 112(f) limitations, the specification must at least disclose an algorithm for performing the claimed function, or else the claim s،uld be rejected under 112(b). A general purpose computer alone is not sufficient corresponding structure.

The memo notes a 112(f) limitation found indefinite under 112(b) for lacking sufficient corresponding structure “will also lack adequate written description and may not be sufficiently enabled to support the full scope of the claim under § 112(a).” The specification must describe the invention in enough detail to establish possession of the claimed invention and enable a s،ed artisan to make and use it.

Equivalents: One beauty of means plus function claims is that they cover disclosed em،iments and their “equivalents.”  This statutory equivalents has the power to expand out the scope of the claims in interesting ways. My traditional thinking is that the written description and enablement requirements are satisfied in 112(f) cases by providing at least one structural disclosure linked to the claimed function. However, in Xencor, the PTO held otherwise — indicating that the equivalents must also be supported by the written description.  That case is now before the Appeal Review Panel at the USPTO following remand from the Federal Circuit.

The memo does not particularly address the PTO’s view on whether whether the written description must also support any “equivalents” that fall within the scope of a 112(f).

Comments can be provided to the USPTO at the following link: