In Ring & Pinion Service Inc. v. ARB Corporation LTD., [2013-1238] (February 19, 2013), the Federal Circuit held that foreseeable equivalents could be infringing equivalents.  Through stipulations, the parties set up the question perfectly, agreeing that if a foreseeable equivlent at the time of filng could infringe, the patent was infringed, but if a foreseeable equivalent at the time of infringe could not infringe, the patent was not infringed.  The Federal Circuit affirmed the district court, stating: “There is not, nor has there ever been, a foreseeability limitation on the application of the doctrine of equivalents.”

The Federal Circuit noted that it has long been clear that known interchangeability weighs in favor of finding infringement under the doctrine of equivalents, citing Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17, 36 (1997); Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 609 (1950); Abraxis Bioscience, Inc. v. Mayne Pharma (USA) Inc., 467 F.3d 1370, 1382 (Fed. Cir. 2006); Interactive Pictures Corp. v. Infinite Pictures, Inc., 274 F.3d 1371, 1383 (Fed. Cir. 2001); and Corning Glass Works v. Sumitomo Elec. U.S.A., Inc., 868 F.2d 1251, 1261 (Fed. Cir. 1989), and concluding that “[e]xcluding equivalents that were foreseeable at the time of patenting would directly conflict with these holdings that “known interchangeability” supports infringement under the doctrine of equivalents.

COMMENT: The defendant may have been confused by the foreseeability test of Festo Corp. v. Skoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002), which determines the scope of prosecution history estoppel created by a narrowing claim amendment, and thus indirectly the scope of infringing equivlents.  Patent prosecutors can breath easier, but should still strive to write claims broad enough to literally cover foreseeable equivalents.