Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co.
Headline: Patent law clarified: Court limits when narrowing patent applications block claims of equivalent copies, rejects complete-bar rule, and affects inventors and competitors deciding what counts as an infringing substitute.
Holding:
- Makes narrowing patent amendments presumptively limit later claims of equivalents.
- Allows inventors to rebut that presumption by showing equivalents were unforeseeable.
- Sends the case back for courts to decide if specific features were surrendered.
Summary
Background
Petitioner Festo Corporation owns patents for a magnetic rodless cylinder and amended its patent applications during review to add limits: two sealing rings with one-way lips and a magnetizable sleeve. A competitor called SMC sold a similar device with a single two-way sealing ring and a nonmagnetizable sleeve. Festo sued for infringement under the doctrine of equivalents; SMC argued Festo had surrendered those alternatives during prosecution.
Reasoning
The Court addressed two questions: which amendments during patent review can create a bar based on the public prosecution record, and whether any such bar blocks all equivalents. The Court held that narrowing amendments made to meet any Patent Act requirement can give rise to a presumption that the patentee surrendered the territory between the original and narrowed claim. The Court rejected a per se rule that bars all equivalents and said inventors can rebut the presumption by showing an equivalent was unforeseeable, only tangentially related, or otherwise could not reasonably have been described.
Real world impact
The decision means competitors may rely on the public prosecution record when designing around patents, but inventors who narrowed claims can still prove particular substitutes were not surrendered. The Supreme Court vacated the Federal Circuit’s judgment and sent the case back for fact-finding about whether the sealing rings and sleeve composition were surrendered. The legal standard set here governs later infringement proceedings.
Dissents or concurrances
The Federal Circuit had split: several judges had urged a complete-bar rule and warned that a flexible approach would create uncertainty, but the Supreme Court chose a presumption-plus-rebuttal framework.
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