“The sole issue specifically before us is whether Festo can rebut the presumption that the filing of narrowing amendments for the two patents in suit surrendered all subject matter between the original claim limitations and the amended claim limitations.”
“[W]e conclude that Festo cannot overcome that presumption by demonstrating that the rationale underlying the narrowing amendments bore no more than a tangential relation to the accused equivalents or by demonstrating that there was ‘some other reason’ such that the patentee could not reasonably have been expected to have described the accused equivalents.”
