CAFC Decides Patent Reissue was Improperly Broadened Based on Previous Markman Definition
Yesterday, in ArcelorMittal France v. AK Steel Corp. (CAFC 2015), the CAFC considered the impact of a reissue of U.S. Patent 6,296,805 on a previous appeal decision. The ‘805 patent, directed to rolled steel, recited the claim limitation “very high mechanical resistance.” In an earlier infringement suit between the parties, the district court found this terminology to define “a tensile strength greater than 1500 MPa.” This construction was upheld by the CAFC on appeal, and the case as remanded as to other issues.
Ostensibly, the USPTO did not consider 1000MPa limitation as broadening relative to the specification of the ‘805 patent. On the other hand, the CAFC found “greater than 1000MPa” to be broadening based upon the district court’s previous construction that the scope of “very high mechanical resistance” was greater than 1500MPa. This difference in construction highlights the potential incongruity between USPTO and district court claim construction practices.