Common Sense Claim Construction

Claim construction interprets a patent claim based on the words in the claim. Construing a claim, however, does not mean redrafting a claim.

Chef America

In Chef America, Inc. v. Lamb-Weston, Inc., 358 F.3d 1371, 1374 (Fed. Cir. 2004), the patent claimed a process for making baked goods. Id. at 1372. The claim limitation at issue was “heating the resulting batter-coated dough to a temperature in the range of about 400° F. to 850° F.” Id. at 1371. The patentee contended that the claimed temperature range of “400° F. to 850° F.” referred to the temperature of the oven, rather than the temperature of the dough. Id. at 1371–72. The Court, however, held that the claims were unambiguous and declined to replace the term “to” with the term “at,” even though the claim, as written, would lead to the absurd result of burning the dough to a crisp.


In AlterWAN v., Inc., No. 2022-1349, — F.4th — (Fed. Cir. Mar. 13, 2023), however, the Federal Circuit clarified that “Chef America does not require us to depart from common sense in claim construction.” (emphasis added).

The patent-in-suit was directed towards improvements to implementing wide area networks (“WANs”) over the Internet.

The district court had construed the claim term “non-blocking bandwidth” to be a “bandwidth that will always be available and will always be sufficient,” reasoning that the patentee acted as its own lexicographer and that the claim language required that the bandwidth be available even if the Internet was down.

The Federal Circuit, however, held that “the claim language itself does not unambiguously require bandwidth to be available even when the Internet is inoperable.”

It is true that the specification defines “non-blocking bandwidth” as “bandwidth that will always be available and will always be sufficient.” ’478 patent, col. 4 l. 67–col. 5 l. 1. But this statement must be read in context.

            The specification states that “[t]he wide area network technology described herein (referred to as AlterWAN™ network) is an alternative wide area network that uses the internet as a backbone.” ’478 patent, col. 3, ll. 61–63. The specification describes several “quality of service” problems that arise from using the internet as a backbone, including latency problems, that is, “delay on critical packets getting from source to destination.” ’478 patent, col. 3 ll. 20–53. The patent’s solution to the latency problem is to provide “preplanned high bandwidth, low hop-count routing paths between pairs of customer sites that are geographically separated.” ’478 patent, col. 4 ll. 17–19. The specification describes the preplanned routing paths as a “key characteristic that all species within the genus of the invention will share” and details its operation. ’478 patent, col. 4 ll. 15–64. The specification then states: “In other words, the quality of service problem that has plagued prior attempts is solved by providing non-blocking bandwidth (bandwidth that will always be available and will always be sufficient) and predefining routes for the ‘private tunnel’ paths between points on the internet . . . .” ’478 patent, col. 4 l. 65– col. 5 l. 3.

            The specification does not remotely suggest operability when the Internet is unavailable. Claims that are directed to transmission over the Internet cannot require such transmission when the Internet is not working. In light of the specification, “non-blocking bandwidth” is properly understood to address the problem of latency, rather than providing for bandwidth even in the scenario where the Internet is inoperable.

The Federal Circuit did not otherwise construe the meaning of non-blocking bandwidth. The case was remanded back to the district court for further appropriate claim construction.


The patent attorneys at Thomas P. Howard, LLC prosecute patent applications before the USPTO, as well as in enforce patents or defend against infringement in litigation nationwide including in Colorado.