Background
Honeywell International owned U.S. Patent No. 5,630,976, directed to a process for manufacturing polyethylene terephthalate (PET) yarn used in tire cord reinforcement. The patent claims specified mechanical properties — including melting point elevation (MPE) — that the yarn must achieve at various stages of the production process. The patent required MPE values to fall within defined ranges, measured using a Differential Scanning Calorimeter (DSC).
Honeywell filed a complaint with the International Trade Commission (ITC) under § 337 of the Tariff Act of 1930, alleging that PET yarns imported by Hyosung Corporation of Korea infringed the ‘976 patent. The ITC — which handles complaints about unfair import practices including patent infringement by imported goods — investigated and concluded that Hyosung’s yarns did not infringe and, more significantly, that the ‘976 patent was invalid as indefinite. Honeywell appealed.
The pivotal problem: the patent specified MPE measurement ranges but did not identify which of four known sample preparation methods — the coil, cut, restrained, or ball method — to use when preparing the yarn specimen before placing it in the DSC. Each method produced significantly different MPE readings for the same material. The choice of preparation method determined whether a given yarn fell inside or outside the claimed ranges.
The Court’s Holding
The Federal Circuit affirmed the ITC’s invalidity ruling. Writing for the panel, Judge Linn held that the ‘976 patent claims were “insolubly ambiguous” — the standard for indefiniteness under pre-Nautilus Federal Circuit doctrine — because nothing in the intrinsic record (claims, specification, or prosecution history) told a person of ordinary skill which sample preparation method to use when measuring MPE.
The court considered three possible claim constructions: (1) use only Honeywell’s proprietary but unpublished “ball method”; (2) satisfy the claims if any preparation method yields measurements within the claimed ranges; or (3) require all four methods to produce measurements within the ranges. None of these constructions could be confidently adopted from the claim language and specification. The first would import a secret methodology never published in the patent; the second would allow wildly different products to qualify or not depending on which method was chosen; the third would be nearly impossible to satisfy.
Because the choice of preparation method was critical to determining whether a competitor’s yarn met the patent’s claimed parameters, and the patent gave no guidance on that critical choice, the claims failed to particularly point out and distinctly claim the invention as required by § 112, paragraph 2. Competitors could not reliably determine whether their products would infringe — the hallmark of an indefinite claim.
Key Takeaways
- Patent claims that specify measurement parameters must identify the measurement methodology clearly enough that a skilled artisan can determine whether a product or process falls within the claim — leaving measurement method ambiguous renders claims indefinite.
- “Insolubly ambiguous” claims — those that cannot be given a definite construction from the intrinsic record — are invalid under § 112, paragraph 2.
- The ITC has the authority to find patents invalid in § 337 proceedings, and the Federal Circuit applies the same indefiniteness standard used in district court patent litigation.
- Patentees should specify measurement protocols, test methods, and sample preparation procedures in the patent specification whenever quantitative claim limitations depend on how measurements are taken.
- After Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898 (2014), the Supreme Court replaced the “insolubly ambiguous” standard with a stricter test requiring claims to inform skilled artisans of the invention’s scope “with reasonable certainty.”
Why It Matters
Honeywell v. ITC illustrates a recurring problem in patents involving quantitative specifications: the measured value depends on the measurement technique. In fields like materials science, polymer chemistry, pharmaceuticals, and electronics, different test protocols can produce substantially different numerical results for the same sample. A claim that specifies a numerical range without specifying how to measure it may be fatally ambiguous — leaving competitors unable to know whether their products infringe and leaving courts unable to evaluate infringement at all.
The case is also an important example of ITC patent invalidity proceedings. The § 337 process is designed to provide a faster remedy for domestic industries harmed by infringing imports, but importers can — and regularly do — defend by challenging the asserted patent’s validity. Honeywell v. ITC confirms that the same indefiniteness standard that applies in district court patent litigation applies in ITC investigations, making rigorous claim drafting just as important for patents asserted at the ITC as for those litigated in federal court.