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Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co.
United States Court of Appeals for the Federal Circuit
493 F.3d 1368, 83 U.S.P.Q.2d 1385 (2007)
Festo Corporation (plaintiff) sued Shoketsu Kinzoku Kogyo Kabushiki Co. and SMC Pneumatics, Inc. (defendants) in federal court for infringement of U.S. Patent No. 4,354,125 (the 125 patent), which claimed a magnetic sleeve. The device accused of infringing the 125 patent was a sleeve made of nonmagnetic aluminum alloy. The initial patent application for the 125 patent did not require the use of a magnetic sleeve, though a sleeve that enclosed magnets was disclosed in the patent specification. The patent application was rejected, and prior art from Germany that was submitted in response to the rejection showed the use of nonmagnetic material to make a sleeve. The 125 patent was amended to require a magnetic sleeve that shielded against magnetic-field leakage. Festo filed a motion for summary judgment of infringement under the doctrine of equivalents. Festo presented evidence related to foreseeability, including evidence that a person of ordinary skill in the art would not have known at the time of patent amendment that an aluminum sleeve would shield against magnetic-field leakage. The district court accepted this assertion but determined that the aluminum sleeve was foreseeable. Festo appealed, arguing that the function-way-result test and insubstantial-differences test should be applied to determine foreseeability.
Rule of Law
Holding and Reasoning (Dyk, J.)
Dissent (Newman, J.)
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