Insituform again, Tangential Festo.

Under the "absolute bar" of the 2000 CAFC Festo case, the patentee lost. Now, the patentee wins under the tangential prong of the 2002 Supreme Court Festo.

From the 2004 Insituform case:

For their part, defendants note that claim 1, as originally filed, covered a process using single or multiple cups at any location downstream of the resin front. See Insituform I, 99 F.3d at 1108. They also note that we construed claim 1, as amended, to cover a single vacuum cup, which inherently creates a discontinuous vacuum. Id. at 1106. Defendants thus argue that accused Process 1 falls squarely within the territory surrendered by the narrowing amendment.

For the reasons which follow, we hold that plaintiffs have rebutted the Festo presumption that a narrowing amendment made for a reason of patentability surrenders the entire territory between the original claim limitation and the amended claim limitation. See Festo II, 535 U.S. at 740-41. We reach this conclusion because we conclude that the prosecution history establishes that “the rationale underlying” the amendment narrowing the scope of literal claim coverage from multiple cups to a single cup bears “no more than a tangential relation to the equivalent in question,” accused Process 1. Id. Therefore, application of the doctrine of equivalents in this case was not barred. Accordingly, we again affirm the judgment of the district court that Process 1 infringed claim 1 of the ‘012 patent under the doctrine of equivalents.
In Insituform I, we construed claim 1 of the ‘012 patent as limited to “a process using only one vacuum cup which inherently creates a discontinuous vacuum.” Id. at 1106. Based upon that construction, we affirmed the district court’s JNOV that Firstliner’s Process 1, employing multiple cups beyond the resin, did not literally infringe claim 1. Id. As noted, we also held, however, that Insituform was not barred by prosecution history estoppel from asserting that Process 1 infringed claim 1 under the doctrine of equivalents. Id. at 1109. In so holding, we first looked at the original claims in Insituform’s application. Of those, only the first four are relevant to this appeal.

(...)
In our view, Insituform has rebutted the Festo presumption. The prosecution history and our discussion of that history in Insituform I and II compel the conclusion that the amendment limiting the literal scope of claim 1 to a single cup process bears “only a tangential relation,” if that, “to the equivalent in question,” a process using multiple cups. The question we must address is “whether the reason for the narrowing amendment was peripheral, or not directly relevant, to the alleged equivalent.” Festo III, 344 F.3d at 1365. As the discussion above indicates, the narrowing amendment in this case was for the purpose of distinguishing the invention over Everson. Insituform made it clear that the difference between its process and Everson was that its process did not have the disadvantage of the Everson process of a large compressor at the end of the liner. There is no indication in the prosecution history of any relationship between the narrowing amendment and a multiple cup process, which is the alleged equivalent in this case. Thus, we hold that plaintiffs have successfully rebutted the Festo presumption by establishing that the amendment narrowing the claimed invention from multiple cups to a single cup was tangential to accused Process 1, which used multiple cups attached at different points along the liner tube. We therefore affirm the judgment of infringement under the doctrine of equivalents.

[Hmmm, after showing rebuttal of the presumption, doesn't the CAFC have to perform another step, showing that the accused element IS an equivalent of the claimed element? See also my earlier article: Insituform: Festo for the Festophile? in Intellectual Property Today.]