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Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd.

    Brief Fact Summary. Festo (Plaintiff) claimed patent infringement against Shoketsu (Defendant).  Defendant argued that by narrowing claims to obtain its patents, Plaintiff surrendered all equivalents to the amended claims.

    Synopsis of Rule of Law. The narrowing of an amendment to satisfy any requirement of the Patent Act may result in estoppels.  However, estoppel does not prevent the patentee from claiming infringement against any equivalent to the narrowed element.  The patentee bears the burden of proving that the amendment does not surrender the particular equivalent in question.

    Facts. Plaintiff owns two patents for a magnetic rodless cylinder, a piston-driven device that uses magnets to move objects in a conveying system.  In response to rejection, the prosecution history reveals that both patent applications were amended to reference prior art and new limitations.  There were two new limitations: (1) the inventions are to contain a pair of sealing rings, each having a lip on one side, and (2) the outer shell of the device, the sleeve, is to be made of a magnetizable material.  Defendant then brought a similar device to the market that had a single sealing ring with a two-way lip and a sleeve made of magnetizable alloy.  Plaintiff sued for infringement claiming that although there was no literal infringement, Defendant’s device infringed under the doctrine of equivalents because the devices were very similar.  Defendant argued that Plaintiff was stopped from presenting this argument because of the prosecution history regarding the patents.  The district court held that Plaintiff’s amendments were not made to avoid prior art and did not result in estoppel.  The court of appeals reversed and held that by narrowing a claim to secure a patent, the patentee surrenders all equivalents to the amended claim element.  Prior decisions held that prosecution history estoppels made a flexible bar, foreclosing some, but not all, claims of equivalence, depending on the reason for the amendment and the changes in the text.  Plaintiff appealed.

    Issue. Was it in error that the court of appeals held that (1) estoppel can be applied to every amendment made to satisfy the requirements of the Patent Act and not just to amendments made to avoid preemption by an earlier invention, and (2) when estoppel arises does it prevent every suit against every equivalent to the amended claim element?

    Held. (Kennedy, J.)  (1)  No.  The court of appeals was not wrong in holding that a narrowing amendment made to satisfy any requirement of the Patent Act might result in estoppel.  The scope of a patent is not limited to its literal terms but instead includes all equivalents to the claims described.  Prosecution history estoppel requires that the claims of a patent be interpreted in light of the proceedings in the PTO while the application is being processed.  When the patentee narrows a claim regarding subject matter in response to a denied charge of patent infringement, the patentee may not argue that the surrendered territory was made up of unforeseen subject matter that should be deemed equivalent to the literal claims of the issued patent.  To give up an appeal of rejection and submit an amended claim is an acknowledgement that the invention as patented does not reach as far as the original claim.  Therefore, the patentee is giving up certain subject matter as a condition of receiving a patent.  When an amendment is narrowed to satisfy any requirement of the Patent Act, estoppel may result.  Before a patent can issue, there are statutory requirements that must be met.  When an amendment is made to secure a patent and the amendment narrows the scope of the patent, estoppel results.  If an amendment only concerns the form of the application and not the subject matter of the invention, then it would not narrow the patent’s scope or raise an estoppel.  When a patent’s scope is narrowed by a necessary amendment, estoppel may apply.  (2) Yes.  The court of appeals was wrong in holding that estoppel prevents the inventor from claiming infringement against any equivalent to the narrowed element.  It was incorrect to adopt a complete bar.  The reach of prosecution estoppel requires an examination of the subject matter surrendered by the narrowing amendment.  Such an inquiry would be avoided by a complete bar.  The narrowing amendment may show what the claim is not, but it may not capture what the claim is and therefore equivalents may still exist.  The amended claim is not so perfect in description that no one could create an equivalent.  The patentee should bear the burden of showing that the amendment does not give up the specific equivalent in question.  In some cases the amendment is not reasonably viewed as giving up a particular equivalent.  The equivalent may not have been foreseeable at the time of the application or the reasoning underlying the amendment may bear no more than a comparable relation to the equivalent in question. The patentee must establish that at the time of the amendment, one skilled in the art could not have reasonably been expected to have drafted a claim that would have literally included the alleged equivalent.  In this case, Plaintiff did not deny the presumption that estoppel applies, and the equivalents have been surrendered.  The limitations were made following rejection.  The question then becomes what territory the amendments surrendered, or whether they surrendered the equivalents at issue.  Vacated and remanded.

    Discussion. This was likely the most important commercial case of the 2002-2003 term of the Supreme Court.



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