Introduction to Infringement Under the Doctrine of Equivalents
The Doctrine of Equivalents allows infringement to be found in some cases where the elements of the accused device are substantially equivalent to the corresponding elements of the asserted claim. K-2 Corp. v. Salomon S.A., 191 F.3d 1356, 1366, 52 USPQ2d 1001 (Fed. Cir. 1999). The Doctrine of Equivalents prevents an accused infringer from avoiding infringement by changing only minor or insubstantial details of a claimed invention while retaining the essential functionality of each of those details. Thus, a device that does not literally infringe a claim may nonetheless infringe under the Doctrine of Equivalents if every limitation in the claim is literally or equivalently present in the accused device or method. Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 41 USPQ2d 1865, 1876 (1997). This “all elements” rule of the Doctrine of Equivalents requires that an alleged infringing device have an identical or equivalent element for each limitation contained in the claim of the alleged infringed patent. Loral Fairchild Corp. v. Sony Corp., 50 USPQ2d 1865, 181 F.3d 1313, 1327.
Analyze Individual Elements of the Claim
In analyzing a claim under the Doctrine of Equivalents, it is fundamental that the text of the claim must be closely followed and each element contained in the claim is deemed material to defining the scope of the alleged infringed patent. Thus the Doctrine of Equivalents must be applied to the individual elements of the claim, not to the patent as a whole. K-2 Corp. v. Salomon S.A., 191 F.3d at 1367. Additionally, any claim placed element limitation must be applied because the Doctrine of Equivalents cannot be used to vitiate the limitation of the element from the claim in its entirety. K-2 Corp. v. Salomon S.A., 191 F.3d at 1367.
Forseeable Changes to Claim Limitations
Second, foreseeable changes to claim limitations cannot be reached by the Doctrine of Equivalents. Sage Products, Inc. v. Devon Industries, Inc., 44 USPQ2d 1103, 1107 (Fed. Cir. 1997). In particular, the Federal Circuit has said that “as between the patentee who had a clear opportunity to negotiate broader claims but did not do so, and the public at large, it is the patentee who must bear the costs of its failure to seek protection for this foreseeable alteration of its claimed structure.”
Subject Matter Surrender
Third, the Doctrine of Equivalents cannot be used to reach subject matter surrendered by the patent applicant during prosecution of the patent application, “when there was a substantial reason related to patentability for” making that surrender. Warner-Jenkinson, 41 USPQ2d at 1873. This is generally referred to as the “doctrine of prosecution history estoppel.” There is a rebuttable presumption that the Patent Office had a substantial reason related to patentability for including the limiting element added by amendment. Warner-Jenkinson, 41 USPQ2d at 1873.
Prior Art Limitations
Fourth, the Doctrine of Equivalents cannot be used to reach a claim scope that could not have been obtained literally during prosecution before the Patent Office due to the existence of prior art. Wilson Sporting Goods Co. v. David Geoffrey & Assoc., 14 USPQ2d 1942, 1948 (Fed. Cir. 1990).