Fletcher YoderA district court must construe all disputed claim terms when the meaning of the terms affects the scope of the claims. The doctrine of equivalents does not apply if the objectively apparent reason for a narrowing amendment is not tangential to an alleged equivalent as indicated by clear claim language.
Question of law is presented by issue of whether patentee, having made narrowing claim amendment for substantial reason related to patentability, has successfully rebutted presumption that it has surrendered all territory between original claim limitation and amended limitation, since prosecution history estoppel is equitable in nature, and whether such estoppel applies presents question of law.