In general, a prosecution disclaimer will only apply to a subsequent patent if that patent contains the same claim limitation as its predecessor. “If the language of the later limitation is significantly different, the disclaimer will not apply.” This suggests that one approach to shedding potentially unwanted disclaimers in the prosecution history of a parent application is to reword the claims and pursue a continuation: “We have held that it is permissible for a patentee to take a different approach to claiming an invention in subsequent patents, either by adding limitations or by altering the claims’ format.”
Background / Facts: The patents here are directed toward “septal occluders,” which are medical devices used to block holes in a thin wall of muscle and tissue (a “septum”) dividing two chambers of the heart. The main claim feature at issue is a peripheral frame structure means-plus-function element that is not literally anticipated by the prior art, but which was found to be an equivalent thereof. The patentee argued that it disclaimed this equivalent (a radial umbrella frame found in the primary reference) when attempting to distinguish the same primary reference in prosecuting the parent of the present application, such that the means-plus-function element does not include that feature as an equivalent and is not anticipated. However, the particular means-plus-function element at issue was not present in the claims of the parent application when the disclaimer was made.
Issue(s): Whether the patentee’s disclaimer carries forward to the new means-plus-function language.
Holding(s): No. “[W]hen the purported disclaimers [made during prosecution] are directed to specific claim terms that have been omitted or materially altered in subsequent applications (rather than to the invention itself), those disclaimers do not apply.’” This is because a disclaimer of claim coverage in light of certain prior art is not the same as the applicant acting as a lexicographer redefining individual words. “The appropriate focus is on the scope of the claim element, not the meaning of particular words in isolation.” The similarity between the earlier and later claim limitations is therefore crucial in carrying a disclaimer forward because it is only those elements, not their individual words, that have had their scope narrowed. Thus, the original disclaimer does not carry over to limit the range of equivalents here, and therefore does not negate the district court’s anticipation finding.