Foreseeable Surrender of Equivalents Objectively Determined from Original Claim Scope at Time of Amendment
In the U.S., the doctrine of "prosecution history estoppel limits the range of equivalents available to a patentee by preventing recapture of subject matter surrendered during prosecution of the patent." Southwall Techs., Inc. v. Cardinal IG Co., 54 F.3d 1570, 1579 (Fed. Cir. 1995). The burden is on the patentee to establish that the reason for the amendment was unrelated to patentability. Warner-Jenkinson, 520 U.S at 33. If the patentee fails to meet this burden, the court must presume that the patentee "had a substantial reason related to patentability for including the limiting element added by amendment." Id. If there is a substantial reason related to patentability "prosecution history estoppel would bar the application of the doctrine of equivalents as to that element." Id. However, in Festo VIII, 535 U.S. at 740, the Supreme Court held that the patentee may prove that the amendment did not surrender the particular equivalent by demonstrating that one of three exceptions is met, namelythat
- the equivalent was "unforeseeable at the time of the application,"
- "the rationale underlying the amendment [bears] no more than a tangential relation to the equivalent in question," or
- that "some other reason suggest[s] that the patentee could not reasonably be expected to have described the insubstantial substitute in question." Festo VIII, 535 U.S. at 740-41.
On remand from the Supreme Court, the Federal Circuit concluded that "unforeseeable at the time of the amendment" meant "whether the alleged equivalent would have been unforeseeable to one of ordinary skill in the art at the time of the amendment." Festo X, 344 F.3d at 1369. They noted that later-developed technology or technology that was not known in the pertinent prior art was "usually" not foreseeable. Id. However, they explained that "old technology, while not always foreseeable, would more likely have been foreseeable. Indeed, if the alleged equivalent were known in the prior art in the field of the invention, it certainly should have been foreseeable at the time of the amendment." Id.
During prosecution, amendements and a new independent claim were added for a “cylindrical sleeve made of a magnetizable material” and the term “sealing means” was replaced with “first sealing rings located axially outside said guide rings.” The accused device included a sleeve member made of a non-magnetizable material (aluminum alloy), with only one sealing ring.
The question then became whether the use of a non-magnetizable sleeve or a single sealing ring was known as an alternative in the prior art at the time of amendment. Because the Federal Circuit concluded that use of non-magnetizable sleeves (including aluminum sleeves) was foreseeable under the original broader claim, they did not determine whether use of a single sealing ring was foreseeable.
According to the Federal Circuit,
We disagree that the foreseeability test requires application of the function/way/result or insubstantial differences test. Rather, we find that
an alternative is foreseeable if it is disclosed in the pertinent prior art
in the field of the invention. In other words, an alternative is foreseeable
if it is known in the field of the invention as reflected in the claim scope
before amendment. We have no occasion here to determine in what other
circumstances an equivalent might be foreseeable. . . .
Even if we were to assume that Festo’s argument was consistent with the purpose of the doctrine of equivalents, we conclude that, contrary to Festo’s argument, the foreseeability requirement does not require the knowledge that the equivalent would satisfy the function/way/result test or the insubstantial differences test.
. . . Festo also offers no persuasive theory as to why the function/way/result test applied to the claims as amended should be used to determine foreseeability. To adopt Festo’s argument, in fact, makes no sense. First, the function/way/result or insubstantial differences test is designed to determine whether the alternative is sufficiently close to the claimed feature that the patentee should be able to capture the equivalent and bar its use by a competitor. The test is not designed to determine whether prosecution history estoppel applies as a result of a limiting amendment. Festo offers no rationale for importing a test designed for one purpose into an entirely different context.
. . .Finally, and most important, Festo’s test focuses on the wrong claim. The
question is not whether after the narrowing amendment the alternative was a
known equivalent, but rather whether it was a known equivalent before the
narrowing amendment. The purpose of an amendment typically is to avoid the prior
art. If at the time of the amendment, the equivalent was known in the pertinent
prior art, the applicant should not be able to recapture it simply by
establishing that a property of the equivalent—irrelevant to the broader claim
before amendment—was relevant but unknown with respect to the objectives of the
narrower amended claim. In other words, an equivalent that is foreseeable as an
alternative to the broader claimed feature does not become unforeseeable simply
because the claimed feature is narrowed. For example, if a claim before
amendment broadly claimed a metal filament for a light bulb but was later
amended to avoid prior art and to specify metal A because of its longevity, the
equivalent metal B, known in the prior art to function as a bulb filament, is
not unforeseeable even though its longevity was unknown at the time of
Adopting this standard for foreseeability is not unfair when a reasonable
applicant at the time of the amendment would have been aware of the equivalent
as an alternative under the broader claim before the amendment. Under such
circumstances the applicant can properly be charged with surrender by narrowing
the claim to exclude the alternative. The Supreme Court noted that a surrender
is appropriate where "the inventor turned his attention to the subject matter in
question, knew the words for both the broader and narrower claim, and
affirmatively chose the latter." Festo VIII, 535 U.S. at 734-35.
We thus conclude that the function/way/result test or insubstantial
differences test is inapplicable to the question of foreseeability. An
equivalent is foreseeable if one skilled in the art would have known that the
alternative existed in the field of art as defined by the original claim scope,
even if the suitability of the alternative for the particular purposes defined
by the amended claim scope were unknown.
. . . The question then becomes whether the use of a non-magnetizable sleeve or a single sealing ring was known as an alternative in the prior art at the time of amendment. Because we conclude that use of non-magnetizable sleeves (including
aluminum sleeves) was foreseeable under the original broader claim, we need not determine whether use of a single sealing ring was foreseeable.
Dr. Stoll’s original claim 1 did not include a requirement for a magnetizable sleeve and the claimed sleeve (which could have been composed of any material) was not designed to shield the magnetic field but rather to enclose the magnets. . . .
In response to the examiner’s rejection and in light of the prior art, Dr. Stoll withdrew original claims 1 and 8 and filed a new amended claim that included a requirement for a magnetizable sleeve. A non-magnetizable sleeve was clearly known as available to perform the magnet-enclosing objectives of the claims before the amendment.
. . . We conclude that use of an aluminum alloy sleeve was foreseeable at the time of amendment because the pertinent prior art disclosed a non-magnetizable sleeve. Festo could have claimed use of a non-magnetizable sleeve but did not do so. Accordingly, we find that the equivalent was surrendered by amendment.