Doctrine of Equivalents Must Not 'Vitiate' Limitation

In Freedman Seating Company v. American Seating Company, et al. (Fed. Cir.; August 11, 2005), the court again reversed a summary judgment of infringement under the doctrine of equivalents that had the effect of "vitiating" a limitation of the claims:

The parties agree that all of the claims [in U.S. Patent No. 5,492,389 (above, left)]
require a support member having “a moveable end slidably mounted to” [in red] the seatbase. It is also not disputed that the moveable end of the EZ Fold’s support member is rotatably mounted, not slidably mounted, to the seatbase. Therefore, while the moveable end of the EZ Fold’s support member [above, right] has the ability to rotate, it cannot slide or otherwise move along the seatbase. It is confined to a fixed location. We think that this structural difference in the mounting of the moveable end to the seatbase is not a “subtle difference in degree,” but rather, “a clear, substantial difference or difference in kind.” Ethicon, 149 F.3d at 1321.

Freedman argues that the slider crank claimed in the ’389 patent and the fourth link mechanism used in the EZ Fold function in the same way to produce identical results. Freedman asserts that this is because “[b]oth the infringing seat and the claimed structure of the ’389 patent provide the moveable end of the support member with both translational and rotational motion relative to the seatbase.” The problem, however, is that taken to its logical conclusion, Freedman’s argument would mean that any support member capable of allowing translational and rotational motion would be equivalent to a support member “slidably mounted to said seatbase,” which reads “slidably mounted” completely out of the claims. This is the precise type of overextension of the doctrine of equivalents that the claim vitiation doctrine is intended to prevent. Indeed, we rejected this same type of argument in Tronzo. See 156 F.3d at 1160 (holding that finding all shapes to be equivalent structure would entirely vitiation the limitation requiring a “generally conical shape”).

Freedman’s theory of infringement also suffers from some of the same problems we addressed in Sage Products. In particular, though elegant, the subject matter claimed by the ’389 patent involves relatively simple and well-known technologies. The patentees also stated that they were aware of other types of four bar mechanisms. Yet, they chose to specifically limit the claims to slider-crank mechanisms vis-à-vis the “slidably mounted” moveable end limitation. Members of the public were therefore justified in relying on this specific language in assessing the bounds of the claim. Accordingly, we think that to now say the claims include other four bar mechanisms under the doctrine of equivalents would unjustly undermine the reasonable expectations of the public. See Sage Prods., 126 F.3d at 1425 (“Given a choice of imposing the higher costs of careful prosecution on patentees, or imposing the costs of foreclosed business activity on the public at large, this court believes the costs are properly imposed on the group best positioned to determine whether or not a particular invention warrants investment at a higher level, that is, the patentees.”); see also Conopco, Inc. v. May Dep’t Stores Co., 46 F.3d 1556, 1562 (Fed. Cir. 1994) (“The doctrine of equivalence cannot be used to erase ‘meaningful structural and functional limitations of the claim on which the public is entitled to rely in avoiding infringement.’” (citation omitted)).

In sum, we hold that the district court’s finding of infringement entirely vitiated the “slidably mounted” limitation of the ’389 patent. We therefore reverse the court’s grant of summary judgment and remand with instructions to enter judgment of non-infringement in favor of American Seating.

In contrast to the Patently-O Blog, I don't think that "Every defendant now has an arguable vitiation position — since, by definition, the DOE is only applied against products that do something different than what is required by the claims." Rather, the decision merely confirms that the Doctrine can not be used to avoid a claimed linkage between two structural elements that would otherwise destroy its effect.

For more about "elements," "linkages," and "effects" in patent claims (and the resulting importance of "claim-type differentiation") check out the slides (and/or audio) for my November 2003 APLF Roundtable. Or, better yet, contact me for a live presentation of those ideas (and/or others) to your organization.