6.3 Special Claim Formats: Means-Plus-Function & Markush Claims

6.3 Special Claim Formats: Means-Plus-Function & Markush Claims

Patent law permits several specialized claim formats designed to address specific technical situations—including functional combinations under 35 U.S.C. § 112(f), chemical/material groupings via Markush claims, structural products defined by manufacturing methods (product-by-process claims), and improvement inventions (Jepson claims).

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35 U.S.C. § 112(f) Means-Plus-Function & Step-Plus-Function

Under 35 U.S.C. § 112(f) (pre-AIA sixth paragraph):

"An 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 3-Prong USPTO Examination Test (MPEP 2181)

An examiner will construe a claim limitation under 35 U.S.C. § 112(f) if and only if all three prongs of the following test are met:

1. The claim limitation uses the phrase "means for" or "step for" (or a recognized nonce word acting as a substitute for means).
2. The phrase "means for" or "step for" is modified by functional language.
3. The claim limitation does not recite sufficient structure, material, or acts to perform the specified function.

Presumptions and Nonce Words (Williamson v. Citrix)

• The "Means" Presumption: Use of the term "means for" creates a rebuttable presumption that § 112(f) applies. Omitting "means for" creates a rebuttable presumption that § 112(f) does not apply.
• Rebutting the Presumption: In Williamson v. Citrix Online, LLC, 792 F.3d 1339 (Fed. Cir. 2015), the Federal Circuit eliminated the "strongly presumed" standard. If a claim omits "means" but uses a generic nonce word (e.g., module for, mechanism for, unit for, element for, device for) coupled with functional language without reciting structure, the presumption against § 112(f) is rebutted, and § 112(f) applies.

Software & Computer-Implemented Inventions: The Algorithm Requirement

When § 112(f) applies to a computer-implemented function (e.g., "means for processing financial transactions"), disclosing a general-purpose computer or microprocessor in the specification is insufficient.

The Algorithm Requirement: For software claims under § 112(f), the specification must disclose a specific algorithm (expressed as a flowchart, pseudocode, mathematical formula, or sequential steps) to perform the recited function (Aristocrat Techs. v. Int'l Game Tech.).

If no algorithm is disclosed in the specification, the claim is indefinite under 35 U.S.C. § 112(b) because the claim lacks corresponding structure linked to the function!

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Markush Claims (MPEP 2173.05(h) & MPEP 803.02)

A Markush claim defines an element using a closed group of specified alternatives:

$\text{"wherein the material is selected from the group consisting of A, B, and C."}$

Proper Markush Grouping Requirements

To be proper, the members of a Markush group must share:

1. A single structural similarity (e.g., members belonging to a recognized chemical class sharing a common structural core), OR
2. A common utility or physical property.

Improper Markush Rejections & Election of Species

If the members of a Markush group are patentably distinct (e.g., grouping an organic solvent, a digital sensor, and a ceramic brick with no common property), the examiner issues an improper Markush rejection under § 112(b) or requires an Election of Species under 35 U.S.C. § 121, forcing the applicant to select a single species for search.

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Product-by-Process Claims (MPEP 2113)

A product-by-process claim defines a structural product by its method of manufacture (e.g., "A semiconductor wafer produced by the process of steps A, B, and C").

Patentability Standard vs. Infringement

• USPTO Examination Standard (Patentability): During prosecution, a product-by-process claim is evaluated for patentability (§ 102 novelty / § 103 nonobviousness) based on the final physical product itself, NOT the process steps (In re Thorpe). If the resulting physical product is identical to or obvious over a prior art product, the claim is rejected—even if the prior art product was made by a completely different process!
• Litigation Standard (Infringement): For court litigation, the Federal Circuit held in Abbott Labs. v. Sandoz that process terms in a product-by-process claim serve as actual limitations; an accused product only infringes if it was manufactured using the claimed process steps.

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Jepson Claims (MPEP 2129)

A Jepson claim is an improvement claim format that explicitly delineates prior art from the applicant's novel contribution:

1. Preamble: Recites what is old/known in the prior art ("In an automotive braking system having a master cylinder and brake lines...").
2. Transition: "the improvement comprising:"
3. Body: Recites the new structural element ("a ceramic piston disposed within...").

Binding Prior Art Admission: The preamble of a Jepson claim constitutes an implied binding admission by the applicant that the preamble elements are prior art. The applicant cannot later argue during prosecution or litigation that preamble subject matter is novel.