DOCTRINE OF EQUIVALENTS
Posted in Featured Articles, Legal News
This case required the Federal Court of Appeals to address the relation between two patent law concepts, the doctrine of equivalents and the rule of prosecution history estoppel. The Court in an earlier 1997 case had affirmed that a patent protects its holder against efforts of those who would copy the invention and would seek to evade liability for infringement by making only insubstantial changes to the patented invention. This is covered in the law by the Doctrine of Equivalents, which prevents such a practice.
The rule of prosecution history estoppel means in summary that if concessions are made during the process of amending claims to make them allowable, then those concessions limit the meaning of the resulting claims. That is, this prosecution history “estops” him from later arguing that the subject matter covered by the original, broader claim was nothing more than an equivalent.
“When the patentee has chosen to narrow a claim, courts may presume the amended text was composed with awareness of this rule and that the territory surrendered is not an equivalent of the territory claimed. In those instances, however, the patentee still might rebut the presumption that estoppel bars a claim of equivalence. The patentee must show that at the time of the amendment one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent”
FESTO CORP. V. SHOKETSU KINZOKU KOGYOKABUSHIKI CO. (00-1543)
234 F.3d 558.
