by Robert M. Asher
Recent decisions by the Federal
Circuit Court of Appeals have breathed life into the doctrine of equivalents.
This doctrine is judge-made law that allows patent owners to establish
infringement when an accused product or method has skirted the literal wording
of the patent claims but is only insubstantially different from the claimed
The claims of a patent typically define the legal scope of the invention. The
broader the claims, the more expansive the patent protection and the more
difficult it is to get the claims allowed in the U.S. Patent and Trademark
Due to the vagaries of language and invention and the unforeseeability of all
variations on an inventive concept, any word or phrase in a patent claim offers
aggressive competitors an opportunity to design around the words, while still
benefiting from the inventive teachings. The doctrine of equivalents was
developed to protect the invention when the claim language turns out to be too
The patent litigated in Deere & Co. v. Bush Hog, LLC, 2012 U.S. App. LEXIS
8527 (Fed. Cir., Apr. 25, 2012) [an enhanced version of this opinion is available to lexis.com
subscribers] was directed to a
rotary cutter deck that houses one or more powered mower blades. The upper deck
slopes downwardly "into engagement with, and being secured to" the
lower deck. Rather than directly engaging the upper deck with the lower deck,
the accused products included an intermediate structure connecting the upper
deck to the lower deck.
The district court judge found no infringement because the upper deck of the
accused product did not directly contact the lower deck. The Federal Circuit
reversed, stating "into engagement with" did not require direct
contact. Indirect contact could suffice. Deere & Co. v. Bush Hog, LLC, 703
F.3d 1349 (Fed. Cir. 2012) [enhanced version].
More important, Chief Judge Rader took the opportunity to explain how a court
should apply the doctrine of equivalents. He noted that the lower court judge
believed that "into engagement with" was binary in nature, that is,
the walls of the deck were either in contact or they were not. The district
court feared that allowing a finding of infringement when there was no contact
would "vitiate," that is, give no effect to, that phrase of the
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M. Asher of Sunstein Kann Murphy & Timbers LLP specializes in
patent litigation and prosecution with a particular emphasis on inter partes
review, which operates at the intersection between litigation and prosecution.
He is an astute and accomplished advocate for inventors and businesses affected
by patents. Clients, such as ActiveVideo Networks, Superspeed Software and
Silent Systems, have been richly rewarded from Bob's prosecution work on their
patents. He co-chairs the firm's Patent Practice Group.