BLOGS: The High-Tech Patent Agent: A View from the Trenches in Silicon Valley

Monday, April 22, 2013, 10:37 AM

Rebutting a Presumption of Surrender of Equivalents

How might we retain patent rights to equivalents?  In a previous blog entry, we looked at the presumption that amending a patent application, to narrow a patent claim, surrenders equivalents to any claim element so amended and narrowed.  Festo Corp. v Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002), placed the burden of rebutting this presumption on the patentee.  Justice Kennedy, in the majority opinion, offered one way to rebut.  Are there others?

Conceptually, when we amend a claim during patent prosecution to narrow and exclude known art, that is precisely what we intend.  We intend to surrender known art.  The known art may have equivalents to one or more of the various elements in the known art.  The combined literal elements of the patentee’s amended claim may have equivalents.  There may be a gap between the known art and the combined literal elements of the amended claim.  There may be a gap between the amended claim plus equivalents to elements in the amended claim, and the known art plus equivalents to the elements in the known art.  It is these gaps that can be explored in a rebuttal to the presumption of surrender.  Arguably, in an hypothetical case where a claim is narrowed, a court could consider that the patentee surrendered not only the known art but also the known art extended by equivalents to the elements in the known art.  But, does what the patentee surrendered extend from this point all the way across the gap to the combined literal elements of the amended claim?  Does what the patentee surrendered even extend from such a point all the way across the gap to the combined literal elements of the amended claim as extended by equivalents to these elements?  Or, is there still a gap between what the patentee intended to surrender, i.e., the known art, and what the patentee claimed, extended by equivalents?  If either gap exists, arguably the patentee has not surrendered those equivalents.  There is also room to argue about whether what one side says are equivalents are indeed so.  Remember, equivalents are claim-specific.

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Friday, April 12, 2013, 8:58 AM

Surrender of Equivalents

We discussed the Doctrine of Equivalents in a previous blog entry.  When might a patentee not have claim coverage extending to equivalents of elements in a patent claim?  In Festo Corp. v Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002), also known colloquially as Festo II, the Supreme Court vacated a previous ruling made by the Federal Circuit, and established important holdings regarding equivalents.  It was previously held that amending a patent application, to narrow a patent claim, gave rise to the presumption that equivalents to a particular claim element being amended were surrendered.  That is, amending a claim element to narrow the claim was presumed to constitute a surrender or giving up of equivalents to that claim element.  Equivalents to that claim element were no longer covered by the amended claim.  The newer ruling established that such amendments were no longer considered to create an absolute bar to equivalents.  Reasons for making the amendment could now be taken into account.  The presumption of surrender of equivalents still existed, but this presumption can be rebutted.  A showing that equivalents were not surrendered could now be considered.  Justice Kennedy delivered the majority opinion (separate excerpts below):

… when the court is unable to determine the purpose underlying a narrowing amendment--and hence a rationale for limiting the estoppel to the surrender of particular equivalents--the court should presume that the patentee surrendered all subject matter between the broader and the narrower language.

[In order to rebut this presumption] The patentee must show that at the time of the amendment one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent.


It behooves patentees and patent practitioners alike to carefully consider equivalents when drafting and prosecuting claims.  More thoughts about the presumption of surrender of equivalents will follow in a subsequent blog entry.

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Friday, April 5, 2013, 12:13 PM

Musings regarding the Doctrine of Equivalents

Claims in an issued patent protect a patented invention against infringement.  In a case involving alleged infringement, the essential objective inquiry is: “Does the accused product or process contain elements identical or equivalent to each claimed element of the patented invention?”  Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 117 S. Ct. 1040, 41USPQ2d 1865, 1875 (1977). As to whether an element is an equivalent, “analysis of the role played by each element in the context of the specific patent claim will thus inform the inquiry as to whether a substitute element matches the function, way, and result of the claimed element, or whether the substitute plays a role substantially different from the claimed element.”  41 USPQ2d at 1875.  One interpretation of this case law is that an allegedly infringing substitute element could be found an equivalent to a claimed element in one case.  Yet, the exact same substitute element might not be an equivalent to the same claimed element in another claim in another (unrelated) patent.  On the surface, this might appear paradoxical.  Equivalents are claim-specific and case-specific.  It is the context of the claim that determines whether an allegedly infringing element is an equivalent to a claimed element.

Let’s play around with some hypothetical examples.  Suppose a claim recited some components and a wheel that is driven by these components.  Suppose the specification disclosed an automobile wheel as an example of a type of wheel that could be driven as part of the claimed invention.  Perhaps, one could find that a bicycle wheel or a locomotive wheel is an equivalent to the automobile wheel, as any of these could be driven by the claimed components.  Now, suppose a different patent discloses and claims an automobile wheel with specific features and a new type of tire that fits those specific features.  In this case, a locomotive wheel would likely not be found an equivalent, as locomotive wheels don’t have tires.  The locomotive wheel plays a substantially different role from the automobile wheel, in terms of a relationship with a tire.  It is worth keeping in mind the doctrine of equivalents when crafting claims.  Having an awareness of client and competitor product lines, in the context of research and industry trends, helps us frame relevant questions: Can a claim term be broadened to include an equivalent?  Should it?  Does it do so already?  What might an infringer do?  How much detail should be in the specification to support equivalents?  The doctrine of equivalents helps us answer these questions.

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