Opinion ID: 211104
Heading Depth: 3
Heading Rank: 1

Heading: Amendment-based Estoppel

Text: 78 First, EEI argues that the examiner's amendment that added fatty acid wax to one of 22 new claims estopped Conoco's equivalents argument. When a patentee makes a narrowing amendment to a claim, the patent holder has the burden to demonstrate that the reason for the amendment was unrelated to patentability (e.g., to avoid prior art). Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17, 33, 117 S.Ct. 1040, 137 L.Ed.2d 146 (1997). When the record lacks explanation for the amendment, we presume that the PTO had a substantial reason related to patentability for including the limiting element added by amendment. Id.; accord Festo, 535 U.S. at 735, 739, 122 S.Ct. 1831. 79 Yet, this presumption is not an absolute bar, and the patent holder can rebut the presumption that the doctrine of equivalents will not apply. To do so, 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, 535 U.S. at 741, 122 S.Ct. 1831. A patentee may demonstrate this by showing [ (1) ] [t]he equivalent may have been unforeseeable at the time of the application; [ (2) ] the rationale underlying the amendment may bear no more than a tangential relation to the equivalent in question; or [ (3) ] there may be some other reason suggesting that the patentee could not reasonably be expected to have described the insubstantial substitute in question. Id. at 740-41, 122 S.Ct. 1831. 80 Here, there was an examiner's amendment to add the fatty acid wax limitation to one of the claims. Conoco maintains that the amendment was not related to patentability, but instead added merely to correct an obvious omission. We agree and therefore find no error in the district court's finding. 81 Each of the 16 original claims of the '151 patent application limited the partitioning agent to a fatty acid wax directly or through relation to an independent claim. Throughout the prosecution history, the examiner and applicants focused their attention on the meaning of the fatty acid wax limitation as compared to metal stearate partitioning agents. 82 Moreover, once the applicants cancelled the original claims and submitted 22 new claims, all but the first claim lacked the fatty acid wax limitation—presumably making the new claims broader than originally argued. Nevertheless, the examiner and applicants continued to focus their arguments as if the limitation was present, arguing the difference between fatty acid waxes and metal stearates. Such evidence indicates that the amendment was the correction of an inadvertent omission rather than the intentional narrowing of a broad claim for patentability purposes. Thus, the district court did not err by finding that the claim was not amended for purposes of patentability.