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.