# Chef America v. Lamb-Weston: When Claims Mean Exactly What They Say

> The Federal Circuit read a claim to require heating dough to 400 degrees, an absurd result, because courts construe claims as written.

Topic: Patents  |  Author: Lidiia Levitska  |  Source: Intellectual Property Law (outsideipcounsel.com)
Canonical: https://outsideipcounsel.com/blog/chef-america-v-lamb-weston-dough-to-400-degrees/


*Chef America, Inc. v. Lamb-Weston, Inc.*, 358 F.3d 1371 (Fed. Cir. 2004), decided February 20, 2004, is the patent bar's favorite cautionary tale, the case that proves an unambiguous claim means exactly what it says even when what it says is impossible. The claim called for heating dough "to" a temperature between about 400 and 850 degrees Fahrenheit. Read literally, that instruction would burn the dough to a crisp. The patentee almost certainly meant to heat the dough in an oven set to that range, but the claim used the wrong word, and the Federal Circuit refused to fix it. The court construed the claim as written, held that the accused process did not infringe, and let a drafting error kill the patent's practical value.

The decision is short and its facts are almost comic, but its lesson is deadly serious for anyone who drafts or relies on patent claims. The words of a claim are the metes and bounds of the property right, and courts enforce those boundaries as drawn.

## At a glance

- **Case:** *Chef America, Inc. v. Lamb-Weston, Inc.*, 358 F.3d 1371 (Fed. Cir. 2004)
- **Decided:** February 20, 2004, United States Court of Appeals for the Federal Circuit, affirming summary judgment of noninfringement
- **Holding:** A claim requiring heating dough "to" a temperature of about 400 to 850 degrees means heating the dough itself to that temperature, even though the result is nonsensical, because courts construe claims as written rather than rewrite them.
- **Significance:** The canonical warning that unambiguous claim language controls even when it produces an absurd, patent-killing result.

## The claim and the problem

Chef America owned U.S. Patent No. 4,761,290, titled "Process for making dough products" and directed to a process for producing a dough product, essentially a light, crispy baked good made from batter-coated dough. Claim 1 recited five steps, one of which was "heating the resulting batter-coated dough to a temperature in the range of about 400 F. to 850 F." (Independent claim 8 carried the same limitation.) The intended process almost certainly involved placing the dough in an oven heated to that temperature range, so that the dough would bake to a much lower internal temperature and come out crisp rather than charred. Anyone who has baked understands the difference between the temperature of the oven and the temperature reached by the food inside it.

The claim, however, said "to," not "at." "Heating the dough to 400 to 850 degrees" describes the temperature the dough reaches, not the temperature of the oven that heats it. And dough heated to 400 degrees does not become a light snack; it becomes charcoal. The literal claim thus described a process that would destroy the very product the patent was meant to protect.

## The competing constructions

The dispute reduced to a single preposition. Lamb-Weston, the accused infringer, argued for the literal reading: the claim requires the dough itself to reach 400 to 850 degrees. Under that construction, Lamb-Weston's process, which heated dough in ovens but never raised the dough itself anywhere near 400 degrees, plainly did not infringe. Chef America argued that the claim should be read to mean heating the dough at an oven temperature in that range, consistent with what the inventor obviously intended and with the only reading that makes the process work.

Following a claim-construction hearing under *Markman v. Westview Instruments, Inc.*, 517 U.S. 370 (1996), the district court sided with Lamb-Weston. In a nineteen-page order it looked to the ordinary meaning of the terms, found that the inventor had not given them any special definition, concluded that the claims were unambiguous as written, and held that they clearly referred to the temperature of the dough rather than the oven setting. It granted partial summary judgment on that construction, then granted summary judgment of noninfringement, and Chef America appealed.

## The Federal Circuit's reasoning

The Federal Circuit affirmed and framed the principle bluntly. Courts construe claims as written, not as the patentees wish they had written them. Because the word "to" has an ordinary meaning that unambiguously refers to the temperature to which the dough is heated, the court would not substitute "at" to describe the oven temperature merely because that reading was the only one under which the process worked. The court acknowledged that its construction produced a nonsensical result, saying that dough heated to that range "would be burned to a crisp" and would come out resembling, in one attorney's words, a charcoal briquet, but it held that the absurdity of the outcome did not license the court to redraft the claim. It added a detail the popular retelling usually drops: the prosecution history suggested the patentees had chosen "to" deliberately, since the specification and an original dependent claim used "to" while the worked examples used "at," and Chef America never argued that the word was a draftsman's mistake.

The reasoning rests on the public-notice function of patent claims. Competitors read claims to learn what they may and may not do, and the reliability of that notice depends on courts enforcing the words actually used. If judges could silently rewrite claims whenever the literal language seemed mistaken, the boundaries of patent rights would become unpredictable, and the incentive to draft carefully would collapse. The court distinguished between construing genuinely ambiguous language, where context and the specification legitimately guide meaning, and rewriting language that is unambiguous but unwise. The former is interpretation; the latter is redrafting, and redrafting is not a job for a court asked to construe the claim. The opinion pointed out that the patentees had made no attempt to have any error corrected, either by a certificate of correction from the Patent and Trademark Office under 35 U.S.C. § 255 or by action of the district court. What Chef America could not do was obtain from a court, in the guise of construction, a reading that the claim's plain words would not bear.

## Open questions

*Chef America* draws a firm line, but the line's exact location still generates litigation. The opinion turns on the claim being unambiguous, and later cases wrestle with how much apparent absurdity is enough to make a court find ambiguity in the first place, which would open the door to a saving construction. The relationship between *Chef America* and the doctrine that allows courts to correct obvious errors, as in *Novo Industries, L.P. v. Micro Molds Corp.*, 350 F.3d 1348 (Fed. Cir. 2003), remains a fine one: a court may correct a claim only when the error is evident from the face of the patent and the correction is not subject to reasonable debate, and *Chef America* shows how narrow that safety valve is. Courts also continue to sort out how the specification and prosecution history bear on whether a term is truly unambiguous, since a strong contrary teaching in the specification can sometimes render facially plain words ambiguous under *Phillips v. AWH Corp.*, 415 F.3d 1303 (Fed. Cir. 2005).

## Implications for inventors and businesses

- **Proofread claims against the physics.** *Chef America* shows that a single wrong preposition can render a patent worthless, so applicants should test each claim against how the process or device actually operates before filing.
- **Fix errors while you still can.** The time to correct a drafting mistake is during prosecution or through a certificate of correction, not in litigation, because courts will not save an unambiguous claim from itself.
- **Do not count on judicial rescue.** An accused infringer whose process avoids the literal claim language has a strong noninfringement position even when the patentee clearly meant something else, which makes literal scope a first-order question in any freedom-to-operate analysis.
- **Ambiguity is the only lever.** A patentee stuck with awkward language can argue for a saving construction only if the term is genuinely ambiguous, so the drafting record and specification should be built to support the intended reading from the start.

## Frequently asked questions

**What was the drafting error in Chef America?** The claim recited "heating the resulting batter-coated dough to a temperature in the range of about 400 F. to 850 F." Read literally, that requires raising the dough itself to 400 degrees or more, which would incinerate it. The patentee almost certainly meant heating the dough in an oven set to that temperature, but the claim said "to," not "at."

**Why didn't the court just fix the obvious mistake?** The Federal Circuit held that courts construe claims as written, not as the patentee wishes they had been written. Because the language was unambiguous, the court would not redraft "to" as "at" to rescue the claim, even though the literal reading produced a nonsensical burnt result. Rewriting claims would undermine the public-notice function of patents.

**What is the practical lesson of Chef America?** Precision in claim drafting is not optional. A single wrong preposition can render a patent worthless, because unambiguous claim language controls even when it defeats the invention. Applicants should proofread claims against how the process actually works and fix errors during prosecution rather than hoping a court will read past them.

## Authorities and sources

- [*Chef America, Inc. v. Lamb-Weston, Inc.*, 358 F.3d 1371 (Fed. Cir. 2004) (No. 03-1279) (Public.Resource.Org)](https://law.resource.org/pub/us/case/reporter/F3/358/358.F3d.1371.03-1279.html)
- [*Chef America, Inc. v. Lamb-Weston, Inc.* (FindLaw)](https://caselaw.findlaw.com/court/us-federal-circuit/1419835.html)
- [U.S. Patent No. 4,761,290, "Process for making dough products" (issued Aug. 2, 1988)](https://patents.google.com/patent/US4761290A/en)
- [*Markman v. Westview Instruments, Inc.*, 517 U.S. 370 (1996) (Cornell LII)](https://www.law.cornell.edu/supremecourt/text/517/370)
- [*Phillips v. AWH Corp.*, 415 F.3d 1303 (Fed. Cir. 2005) (en banc) (Public.Resource.Org)](https://law.resource.org/pub/us/case/reporter/F3/415/415.F3d.1303.-1286.03-1269.html)
- [*Novo Industries, L.P. v. Micro Molds Corp.*, 350 F.3d 1348 (Fed. Cir. 2003) (Public.Resource.Org)](https://law.resource.org/pub/us/case/reporter/F3/350/350.F3d.1348.03-1249.03-1230.html)
- [35 U.S.C. § 255 (certificate of correction of applicant's mistake) (Cornell LII)](https://www.law.cornell.edu/uscode/text/35/255)