What Is Means-Plus-Function Claiming?
Means-plus-function claiming is a way of writing a patent that describes what something does, not how it does it. For example, describing a machine that opens a jar, rather than describing all the parts—a motor, a gripper, and how they work together—you just say: “A means for opening a jar.” This is to say you want to protect whatever part does the opening of the jar, without naming the exact part.
Why Structure Still Matters in Functional Patent Claims
However, the actual parts, the structure, must be described elsewhere in the patent. This is a way to write less in the claims, but the downside is that if it doesn’t describe how it works well enough, the claim might be invalid.
Section 112(f): The Legal Framework for Means-Plus-Function Claims
Section 112(f) addresses means-plus-function claiming. The courts apply a two-step analysis for such claims.
The Two-Step Court Analysis Under § 112(f)
First, the court determines whether the claim limitation is drafted in a means-plus-function format, which would invoke Section 112(f). Second, if it is, the court identifies what structure, if any, disclosed in the specification corresponds to the claimed function.
Claim Indefiniteness and Section 112(b)
In cases lacking disclosed structure, the claim is invalid under Section 112(b), which deals with claim definiteness. In simple terms, a patent must clearly tell others what is being claimed so they know the boundaries of the invention.
Why Vague Functional Claims Risk Invalidation
Clear claims can be understood, competitors can avoid infringement, and courts can enforce the patent consistently. Vague or ambiguous claims can be ruled invalid for indefiniteness, which is especially relevant in means-plus-function claims. If the patent application doesn’t describe the structure that performs the function, it may be invalid.
Federal Circuit Spotlight: Fintiv v. PayPal
At the heart of the case were terms like “payment handler” and “payment handler service,” found in Fintiv’s asserted patents.
These terms were intended to cover components that interface with various payment APIs. However, the court found they lacked inherent structural meaning and instead described what the component does rather than what it is.
Functional Claim Language Without Structural Support
At the heart of the case were terms like “payment handler” and “payment handler service,” found in Fintiv’s asserted patents. These terms were intended to cover components that interface with various payment APIs. However, the court found they lacked inherent structural meaning and instead described what the component does rather than what it is.
Why “Payment Handler” Failed as a Structural Term
This triggered the court’s application of the means-plus-function analysis under Section 112(f), even though the word “means” was not used.
Why the Court Rejected Fintiv’s Arguments
Fintiv argued that “payment handler” had a recognized meaning in the art, citing dictionaries, examples from the patent, and even the Internet Open Trading Protocol. The court was unconvinced. It found that the terms merely recited functions—such as wrapping APIs or exposing common interfaces—without explaining how those functions were implemented.
The specification did not help. Instead of disclosing a specific algorithm or structure, it restated the functional goals. According to the court, that was not enough under Section 112(f). A person of ordinary skill in the art would not be able to implement the invention based solely on the description provided.
Lessons for Software Patent Drafting
Functional terms, even when they sound technical, can lead to invalidation if the specification does not back them up with structure. For software patents, that structure usually means an algorithm. Avoiding the word “means” does not automatically avoid means-plus-function treatment. Courts look at substance, not form.
Key Takeaway: Substance Beats Form in Means-Plus-Function Analysis
If a claim recites a function, the patent must explain how that function is performed. Without that disclosure, the claim risks being found indefinite and invalid.