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Broad Claims Not Enabled Given Restrictions in Specification

September 23, 2003
Main Ph.D., Denise

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Last Month at the Federal Circuit - October 2003

Judges: Lourie (author), Clevenger, and Rader

In AK Steel Corp. v. Sollac and Ugine, No. 03- 1074 (Fed. Cir. Sept. 23, 2003), the Federal Circuit affirmed the district court’s SJ rulings of noninfringement of U.S. Patent No. 4,800,135 (“the ‘135 patent”) and invalidity of certain claims in U.S. Patent No. 5,066,549 (“the ‘549 patent”).

AK Steele Corporation (“AK Steele”) owns the ‘135 and ‘549 patents, which share identical specifications and concern hot-dip aluminum-coated stainless steel, where a critical characteristic of the invention is “good wetting”, i.e., aluminum adhering or wetting to steel. The accused infringers, Sollac and Ugine (collectively “Sollac”), manufacture stainless steel that is hot-dipped in a molten mixture including aluminum and 8.0%-8.5% silicon.

The district court had construed the claim term “consisting essentially of aluminum” to require that the aluminum contain not more than 0.5% silicon based on the express teachings of the specification. Particularly, the specification teaches that the inventors considered coatings that contain about 10% by weight silicon, but concluded that this type of aluminum coating metal does not wet well with ferritic chromium alloy steel. Accordingly, the inventors stated that silicon content in the coating metal should not exceed about 0.5% by weight.

According to AK Steele, the specification means that the term “consisting essentially of aluminum” should permit silicon in an amount up to but not including 10%.

The Federal Circuit found that the specification clearly teaches against using Type 1 aluminum as a source for aluminum because Type 1 contains about 10% silicon, which is too much to retain good wetting characteristics. Rather, the specification teaches the use of Type 2 aluminum or nearly pure aluminum. In addition, the specification expressly teaches that silicon contents in the coating material should not exceed about 0.5% by weight. As such, the Federal Circuit found that the claims of the ‘135 patent must be interpreted to not permit an excess of 0.5% silicon by weight in the aluminum coating. The Federal Circuit therefore affirmed the district court’s construction of the claim and held that Sollac’s manufacturing practices, which require aluminum containing 8.0% silicon, did not infringe the ‘135 patent.

These same issues of claim construction related to the interpretation of the phrase “the aluminum coating contains up to about 10% by weight silicon” in claims 3 and 7 of the ‘549 patent. This limitation had been added to these claims to address the Examiner’s rejection of the claim as indefinite because it originally stated that “the coating metal is Type 1 aluminum.”

AK Steele argued that the ordinary meaning of “up to” does not include the 10% endpoint (e.g., “painting the wall up to the door”), especially in view of the specification’s clear disclaimer of Type 1 aluminum, which includes the 10% endpoint.

The Federal Circuit rejected AK Steele’s definition for the ordinary meaning of “up to,” noting that when “up to” precedes a numerical limit, it includes that numerical limit. Second, the Federal Circuit found that there was no indication that the amendment was made to narrow claim scope, but, rather, it responded to the examiner’s request for a more precise meaning of Type 1 aluminum. As such, the dependent claims read “up to and including” 10% silicon as well as Type 1 aluminum. Thus, the Federal Circuit affirmed the district court’s claim construction of the ‘549 patent.

The Federal Circuit also agreed that the ‘549 patent claims were not enabled by the specification. According to the Federal Circuit, the phrase “aluminum alloys” in the independent claim, which includes coating metals containing “up to and including 10% silicon,” has no support in the specification, which, contrary to the claims, teaches aluminum containing not more than 0.5% silicon. Thus, the Federal Circuit held that the specification did not enable the claims of the ‘549 patent.