have a flat section and that the slits extend through the apex of a continuously arched section of the valve.
Gerber sells two styles of lids that use the valve. One is a cartridge-style valve and the other is a welded-style valve. An engineering drawing of the cartridge-style valve is set forth below. In the cartridge-style valve, the valve membrane is mounted in a valve assembly which is removable from the spout. The valve assembly has an integrally molded spout flange around its base. A friction fit is formed between the exterior surface of the valve assembly and the inner surface of the cup lid. The spout flange around the base of the valve assembly serves as a valve holder that abuts a flange within the spout when theat the location of the slit through the membrane and Gerber's alleged equivalent likewise involves the issue of the shape of the membrane at the location of the intersecting slits. Thus, in this case, unlike in Insituform, the rationale underlying the narrowing amendment (to define the shape of the membrane at the location of the slit) is directly relevant to the alleged equivalent.
In sum, plaintiffs have failed to rebut the presumption that they are estopped from attempting to recapture the surrendered territory of non-planar membranes by virtue of having made a narrowing amendment to distinguish the '347 patent over Coy. The Gerber valve membrane, then, either literally infringes the '347 patent by having a flat, two-dimensional quality at the section where the intersecting slits are located or else