It is commonly held that the doctrine of equivalents is lost
when claim amendments are made during patent prosecution.
That is, any claim amendment that is made during patent
prosecution surrenders or gives up elements which are equivalent to
those elements claimed in the amendment. Surrender of the
doctrine of equivalents places the burden on the patent Applicant,
and the patent practitioner representing the Applicant, to
carefully consider any amendments to the claims prior to issuance
of the patent (when such occurs). This principle is neatly
summed up in the rulings on the following two cases.
In re Zletz, 893 F.2d 319, 322, 13 USPQ2d 1320, 1322 (Fed. Cir.
1989) (manner of claim interpretation that is used by courts in
litigation is not the manner of claim interpretation that is
applicable during prosecution of a pending application before the
PTO). Sage Prods., Inc. v. Devon Indus., Inc., 126 F.3d 1420,
1425, 44 USPQ2d 1103, 1107 (Fed. Cir. 1997) (patentee who had a
clear opportunity to negotiate broader claims during prosecution
but did not do so, may not seek to expand the claims through the
doctrine of equivalents, for it is the patentee, not the public,
who must bear the cost of failure to seek protection for this
foreseeable alteration of its claimed structure).
What does this mean for the patent practitioner? The claims
as originally filed in a non-provisional patent application have
full use of the doctrine of equivalents. In an infringement
proceeding, any claim that is granted as originally filed covers
not only the literal elements in the claims but the equivalents of
those elements. But, an amended claim loses the equivalents.
So, the patent practitioner should exercise caution and
prudence when amending claims. Usually, a claim is amended
during patent prosecution to clarify the meaning of a claim
element, or to narrow or broaden the extent of a claim element in
light of art that is cited by the Examiner. As the Sage
ruling above warns us, we have the opportunity to negotiate broader
claims during prosecution. If we don't take advantage of
this opportunity to establish a desired breadth of any claim
element amended, we give up that broader breadth.
Some examples may illuminate. In an electronics patent
application, suppose the claim as originally filed recites MOS
transistors. But, the specification teaches that bipolar
transistors could also be used in a circuit, as could relays, etc.
If the claim as originally filed is granted, it may be
possible to argue that the claim covers other types of transistors
and also relays and so on, as these are equivalent to the MOS
transistors recited in the claim. If, during prosecution, the
claims are amended to recite NMOS transistors (e.g., because some
of the art cites a PMOS transistor embodiment and there is good
reason to argue that an NMOS embodiment is not shown in the art),
then the claims only cover NMOS transistors. It will not be
possible to argue that the claim covers other types of transistors
and also relays, because these equivalents have been surrendered in
the amendment.
In a mechanical patent application, suppose the claim as originally
filed recites threaded fasteners. But, the specification
teaches that nails, welding, rivets, etc. could also be used to
hold something together. If the claim is amended to recite
nuts and bolts, instead of threaded fasteners, then screws, which
are not nuts and bolts, and nails and rivets, etc. are surrendered
through loss of the equivalents.
Now, supposing in each of these cases, there are other arguments to
be made that differentiate the claims from the art, and these other
arguments don't depend on the narrowing as described above.
If the patent practitioner carelessly leaves the above
amendments in place, the equivalents are surrendered needlessly,
and the issued patent is narrower than was necessary in light of
the cited art. This situation is to be avoided. What
should a practitioner do?
When other arguments are found successful against cited art, one
strategy is to revisit previous amendments and carefully consider
whether a broadening amendment could then be made so that the
literal equivalents are captured in the claims. In the
electronics example, suppose an amendment is made elsewhere in the
claim, and the limitations regarding NMOS transistors are amended
to recite transistors, or better still, switches (provided the
specification explains that various types of transistors, relays,
etc. can be used as switches). Now, the amended claim element
recites switches, and has literal coverage for the types of
equivalents the Applicant intends. In the mechanical example,
suppose an amendment is made elsewhere in the claim, and the
limitations regarding nuts and bolts are amended to recite
fasteners, or attachment, or some other broader term, or a list of
devices that fasten or attach two materials together. Now,
the amended claim recites the literal coverage for the types of
equivalents the Applicant intends. This is taking advantage
of the opportunity that the above cases suggest is before us.
Failing to take advantage of this opportunity may have dire
costs for the Applicant, in terms of lost claims coverage. Of
course, art cited by the Examiner should be considered, as the
above tactic of broadening may reintroduce art earlier eliminated
by the initial narrowing amendment and arguments. The
broadening tactic is successful only if the claims, as amended as a
whole, do not read on any of the art under 35 USC §102 and 35
USC §103.
There are also more subtle aspects to this. Comparison
language such as less than or equal to, greater than or equal to,
thresholds and limits may also be subject to the loss of
equivalents in amendment. Words and phrases such as
"or", "and", "one of" versus "at
least one of" or "one or more of" may be subject to
strict scrutiny during Markman hearings, and the doctrine of
equivalents may have bearing on the scope of the claims.
Watch these carefully, and amend these prudently. The
doctrine of equivalents, and loss thereof through amendments, is a
recommended awareness to have in the art of patenting.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
