Asia
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ARTICLE
SUMMARY
The Doctrine of
Equivalents After Warner-Jenkinson
by
Professor Harold
C. Wegner
Partner, Foley & Lardner and
former Director, Intellectual Property Law Program
The George Washington University Law School
Washington, D.C., U. S. A.
Warner-Jenkinson
should strengthen a patent where competitors' embodiments are very close
to the claim language, but only where neither estoppel nor "all
elements" implications are present: Here, the doctrine of equivalents
is alive and well. The 1990's move by some to completely eliminate the
doctrine of equivalents is dead.
A third party who is within the objective scope of
equivalents is an infringer, even if he has independently created his own
commercial embodiment. (The "equity trigger" is dead.)
A patent previously thought to have a necessary scope
of equivalents is greatly weakened if there has been any narrowing
amendment other than one that has a contemporaneous explanation of a
non-prior art basis for such narrowing: Estoppel is implied through
silence.
Any patent that includes even a trivial element
unnecessary to practice the invention is very greatly weakened; even the
Corning Glass exception to Pennwalt is questionable.
Every amendment (including Preliminary Amendments and
Examiner's Amendments) should be carefully thought out in terms of either
(i) explaining a limited scope of estoppel; or (ii) a non-prior art basis
to avoid an estoppel altogether.
Claims to a combination of elements should be carefully
scrutinized to make sure that "element 'X'" is absolutely
necessary for the success of the invention and is absolutely necessary to
establish patentability. (A subclaim including "element 'X'" may
be added.)
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