Patent Claims Scope

Patent claim scope is the legal boundary of what a patent covers — what subject matter the patent owner has the exclusive right to make, use, sell, offer for sale, and import under 35 U.S.C. § 271. Claim scope is determined through CLAIM CONSTRUCTION — the legal interpretation of the claim language, performed by a court (judge) in patent litigation or by the USPTO examiner during prosecution. CLAIM CONSTRUCTION PRINCIPLES: (1) ORDINARY MEANING — claim terms are given their ordinary meaning in the art as of the effective filing date, as understood by a person of ordinary skill in the art (POSITA); (2) SPECIFICATION — the claims are interpreted in light of the specification (the detailed description); the specification is the 'best guide' to the intended meaning of claim terms; however, claim terms should not be limited to specific embodiments disclosed in the specification unless there is express disclaimer or a clear lexicographic definition; (3) PROSECUTION HISTORY — the record of the patent application at the USPTO can narrow claim scope (prosecution history estoppel); statements made to overcome prior art rejections can narrow how broadly a claim term is interpreted; (4) EXTRINSIC EVIDENCE — dictionaries, treatises, and expert testimony can inform claim construction but are less authoritative than the intrinsic record (specification and prosecution history). KEY DECISION: Phillips v. AWH Corp. (Fed. Cir. 2005 en banc) — confirmed that ordinary meaning in light of the specification controls; disfavored over-reliance on dictionaries.

Literal infringement occurs when an accused product or process contains every element of at least one claim, exactly as claimed — with no element missing and no element that doesn't meet the claim limitation. THE ALL-ELEMENTS RULE: A claim is infringed if and only if each element of the claim reads on the accused product or process. If even one element of the claim is missing from the accused product/process, there is no literal infringement of that claim. APPLICATION: to analyze literal infringement, the analyst creates a claim chart — an element-by-element mapping of: Claim Element | Accused Product/Process — and asks for each row: does the accused product have this feature, exactly as the claim describes it? COMMON LITERAL INFRINGEMENT ISSUES: (1) CLAIM INTERPRETATION — the same word may cover more or fewer things depending on construction; e.g., 'a plurality of X' requires at least two X; 'the X' requires that X was previously introduced; 'comprising' is open-ended (additional elements OK); 'consisting of' is closed (no additional elements); (2) MEANS-PLUS-FUNCTION — § 112(f) claims are literally infringed only by the corresponding structure in the specification and its equivalents; (3) METHOD CLAIMS — all steps must be performed by (or attributable to) a single party to find direct infringement; divided infringement is a common defense.

The doctrine of equivalents (DOE) allows a patent to be infringed even when one or more claim elements are not literally met — if the accused element performs substantially the same function, in substantially the same way, to achieve substantially the same result as the claimed element. THE FUNCTION-WAY-RESULT TEST (Graver Tank v. Linde Air Products, S.Ct. 1950): The accused element is equivalent to the claim element if: FUNCTION — it performs the same function as the claimed element; WAY — it performs that function in substantially the same way; RESULT — it achieves substantially the same result. ALTERNATIVE TEST — INSUBSTANTIAL DIFFERENCES (Hilton Davis Chemical v. Warner-Jenkinson, S.Ct. 1997): Is the difference between the claimed element and the accused element insubstantial? DOE LIMITATIONS: (1) PROSECUTION HISTORY ESTOPPEL (Festo Corp. v. Shoketsu, S.Ct. 2002) — if the applicant narrowed a claim to overcome a prior art rejection, the doctrine of equivalents is presumptively barred for the narrowed element; rebuttable if: the equivalent was unforeseeable at the time of prosecution; the amendment was tangential to the narrowing; or there is some other reason; (2) ALL-ELEMENTS RULE UNDER DOE — the doctrine of equivalents cannot eliminate an entire claim element; each element must have a literal or equivalent counterpart in the accused product; (3) DEDICATION TO THE PUBLIC — unclaimed subject matter disclosed in the specification is dedicated to the public (Maxwell v. J. Baker) and cannot be captured by DOE; (4) PRIOR ART LIMITATION — the scope of equivalents cannot extend to subject matter in the prior art.

A claim chart is an element-by-element table that maps each limitation of a patent claim to corresponding features in an accused product, cited prior art reference, or proposed licensed embodiment. CLAIM CHART STRUCTURE: Row 1 — Claim Preamble → Accused product description (or prior art passage); Row 2 — Claim Element 1 → Accused product feature 1; Row 3 — Claim Element 2 → Accused product feature 2; (each limitation of the claim gets its own row; dependent claim elements are often mapped in separate charts). USES OF CLAIM CHARTS: (1) INFRINGEMENT ANALYSIS — mapping claim elements to accused product features to determine whether all elements are met (literal infringement) or substantially met (DOE); the claim chart is the central document in patent litigation damages analysis and licensing negotiations; (2) PRIOR ART / INVALIDITY ANALYSIS — mapping claim elements to a prior art reference to determine whether the reference anticipates (§ 102) or renders obvious (§ 103) the claim; (3) FREEDOM-TO-OPERATE (FTO) ANALYSIS — for a product in development, mapping product features to third-party patent claims to identify potential infringement risks before launch; (4) LICENSING NEGOTIATIONS — demonstrating to a potential licensee which product features are covered by which claims. BEST PRACTICES: cite specific product documentation, source code, user manuals, or technical specifications for each claim chart entry; highlight disputed elements; note whether the analysis is literal or DOE for each element.

Dependent claims are patent claims that incorporate all limitations of an independent claim and add additional limitations. They serve several critical functions: (1) FALLBACK POSITIONS — if the independent claim is found invalid (anticipated or obvious), dependent claims that add patentably distinct limitations may survive; a dependent claim is independently valuable as a fallback position; conversely, if only the dependent claim is infringed (the accused product has all elements of the dependent claim), the dependent claim is stronger evidence of infringement because it's narrower and more specific to the accused product's actual features; (2) PROSECUTION HISTORY LIMITATION — during prosecution, amendments narrowing the independent claim create prosecution history estoppel for DOE; dependent claims that add the same limitation may be less affected because they were always narrow; (3) CLAIM DIFFERENTIATION — a dependent claim implicitly suggests that the independent claim should be interpreted broadly enough that the dependent claim's additional limitation is NOT required by the independent claim; courts use dependent claim differentiation to avoid reading independent claims narrowly; (4) HEDGING BREADTH — independent claims are written broadly to maximize scope; dependent claims hedge by capturing specific commercially important embodiments in narrower language; even if the broad independent claim doesn't survive litigation, the narrower dependent claims covering the key embodiments may; (5) LICENSING VALUE — specific dependent claims covering particular technical features can be licensed to parties whose products incorporate those features, even if the independent claim doesn't technically read on every element of their product.