       NOTE: This disposition is nonprecedential.

  United States Court of Appeals
      for the Federal Circuit
              __________________________

          TEXTRON INNOVATIONS INC.,
               Plaintiff-Appellant,

                           v.
    AMERICAN EUROCOPTER CORPORATION
      (also known as American Eurocopter, LLC)
                AND EUROCOPTER,
                Defendants-Appellees.
              __________________________

                      2011-1309
              __________________________

   Appeal from the United States District Court for the
Northern District of Texas in Case No. 09-CV-0377, Judge
John H. McBryde.
             ___________________________

              Decided: September 7, 2012
             ___________________________

     SCOTT L. ROBERTSON, Goodwin Procter LLP, of Wash-
ington, DC, argued for plaintiff-appellant. With him on
the brief were CHARLES H. SANDERS, of Boston, Massachu-
setts; and MICHAEL S. DEVINCENZO, CALVIN E. WINGFIELD,
JR., and TIMOTHY J. ROUSSEAU, of New York, New York.
TEXTRON INNOVATIONS   v. AM EUROCOPTER                   2


   ROY W. HARDIN, Locke Lord, LLP, of Dallas, Texas,
argued for defendants-appellees. With him on the brief
were MICHAEL V. POWELL and MARK R. BACKOFEN.
              __________________________

   Before NEWMAN, CLEVENGER, and BRYSON, Circuit
                     Judges.
BRYSON, Circuit Judge.

    In this litigation, a helicopter manufacturer has ac-
cused a competitor of infringing its patent covering heli-
copter landing gear assemblies.       The district court
granted summary judgment in favor of the defendant,
concluding that in light of the court’s construction of
certain claim terms, there was no infringement. We
reverse and remand.

                            I

    Textron Innovations Inc. is the owner of U.S. Patent
No. 5,462,242 (“the ’242 patent”). The patent describes a
way of attaching a skid-type landing gear assembly to the
fuselage of a helicopter by using brackets and other
components. Claim 10, the independent claim asserted in
this action, reads as follows:

   10. An improved replacement helicopter landing
   gear assembly, of the type having a bracket ex-
   tending from the helicopter fuselage into engage-
   ment with a strap on top of a generally cylindrical
   crosstube that supports landing devices, the
   bracket engaging the strap and stabilizing the fu-
   selage with respect to the crosstube, the im-
   provement comprising:
3                   TEXTRON INNOVATIONS   v. AM EUROCOPTER


    the strap having an inner surface adapted to en-
         gage an outer surface of the crosstube;

    the strap having an outer surface including a stop
         surface for mating with the bracket to mini-
         mize lateral movement of the bracket on the
         strap;

    the strap extending over the top of the crosstube
         and generally one half around the crosstube,
         terminating in two lower edges that extend
         axially with respect to the tube;

    the strap having a plurality of strap fastener holes
         located proximate to the neutral bending axis
         of the crosstube to minimize stress at the
         strap fastener holes, the strap being other-
         wise imperforate to minimize stress concen-
         tration;

    the crosstube having crosstube fastener holes reg-
         istering with the strap fastener holes on the
         strap;

    the strap being fastened to the crosstube through
         the strap fastener holes and the crosstube
         fastener holes; and

    the crosstube being made of a material which, in a
         crosstube configuration, has a ratio of fatigue
         strength over yield strength of not less than
         0.35.

Figures 2 and 2A from the patent illustrate the way the
crosstube is attached to the fuselage of the helicopter:
TEXTRON INNOVATIONS   v. AM EUROCOPTER                     4




    The patented apparatus describes a bracket consist-
ing of two parts (22a and 22b) that clamp around the
landing gear crosstube (14). To minimize lateral move-
ment of the crosstube with respect to the helicopter body,
a strap (20) is affixed to the crosstube. The strap has a
ridge-like projection, referred to as a stop surface, and the
stop surface “mat[es] with the bracket to minimize lateral
movement.” ’242 patent, col. 7, ll. 20-21.

    In 2009, Textron filed this action against Eurocopter
and its American subsidiary, claiming that the landing
gear assemblies installed on Eurocopter’s EC120 helicop-
ter infringed the ’242 patent. Eurocopter moved for
summary judgment of noninfringement.          Among the
grounds raised by Eurocopter in support of its motion
were (1) that the claims of the ’242 patent were expressly
5                  TEXTRON INNOVATIONS   v. AM EUROCOPTER


limited to replacement landing gear assemblies, and the
assemblies on the EC120 were not replacement assem-
blies but original equipment; and (2) that there could be
no infringement, either literally or under the doctrine of
equivalents, because the accused design did not have a
strap that mated with a bracket that fit on top of the
strap.

    The accused device differs in its structure from the
patented invention. Rather than having a single “strap”
that mates with the bracket, the accused design has a
rubber gasket on which the bracket rests and stop pieces
that mount to either side of the bracket, as illustrated
below:




In the accused device, as in the patented invention, the
bracket consists of two parts: a bottom part (440) and a
corresponding top part (not shown in the illustration).
Together the two bracket parts clamp around the cross-
tube (also not shown). Unlike the patented invention,
however, the top part of the bracket in the accused struc-
ture sits on a rubber gasket (450) rather than on a rigid
strap attached to the crosstube. The rubber gasket does
not minimize the lateral movement of the crosstube by
TEXTRON INNOVATIONS   v. AM EUROCOPTER                   6


itself; instead, two stop pieces (both labeled 380) are
attached to the crosstube on either side of the bracket to
serve that function. The side ridges of the rubber gasket
are interposed between the bracket and the stop pieces, so
that the stop pieces do not directly contact the bracket.

     The district court granted summary judgment to
Eurocopter. Textron Innovations, Inc. v. Am. Eurocopter,
LLC, 773 F. Supp. 2d 650 (N.D. Tex. 2011). The court
construed the term “replacement” as denoting “the intent
that the invention, an improved helicopter landing gear
assembly, is to be used as a replacement for a landing
gear assembly already installed on a helicopter and that
its construction be suitable for that purpose.” Id. at 658-
59. The court based its construction mainly on the prose-
cution history, noting that the addition of the word “re-
placement” in an amendment to the claim after an initial
rejection was meant to give that word an entirely differ-
ent meaning than the word “improvement,” which was
used in the original claims. Id. at 659. The court rejected
Textron’s argument that “improved replacement” in the
asserted claims means an improvement over the prior art
in a device that can be used to replace prior art struc-
tures. The court was persuaded that “clear reliance on
the preamble during prosecution to distinguish the
claimed invention from the prior art transforms the
preamble into a claim limitation because such reliance
indicates use of the preamble to define, in part, the
claimed invention.” Id., quoting Catalina Mktg. Int’l, Inc.
v. Coolsavings.com, Inc., 289 F.3d 801, 808 (Fed. Cir.
2002). Based on that construction, the court concluded
that landing gear assemblies installed as original equip-
ment by Eurocopter could not infringe the ’242 patent. Id.
at 661.
7                   TEXTRON INNOVATIONS    v. AM EUROCOPTER


    The district court also found that there was no literal
infringement of the ’242 patent because the accused
device did not possess a “strap” of the sort recited in the
patent. The court construed the limitation requiring a
“strap having an outer surface including a stop surface for
mating with the bracket to minimize lateral movement of
the bracket on the strap,” to mean that the bracket “seats
on the strap” and that the “stop surface of the strap
contacts the bracket to minimize movement.” The court
found that limitation not to be satisfied in the accused
assemblies because they lacked a strap with the structure
recited in the claim language as the court construed it.
Textron, 773 F. Supp. 2d at 662-63. The court stated that
the rubber gasket in Eurocopter’s design could not be
considered a strap because it had no holes. Id. at 663.
The court further concluded that the stop pieces, which
have holes, could not satisfy the limitation defining the
structure of the strap because the “bracket does not clamp
around or seat on top of the stop pieces.” Id. Addition-
ally, the court noted, the stop surfaces on the stop pieces
contacted the sides of the rubber gasket, not the bracket
itself, as required by the court’s construction of the claim.
Id. The court also stated that there was insufficient
evidence to support Textron’s claim of infringement under
the doctrine of equivalents, but it did not elaborate on
that ruling. Id. at 663-64.

                             II

    On appeal, Textron attacks both grounds for sum-
mary judgment. First, it asserts that the trial court
impermissibly imported a use limitation into an appara-
tus claim when it construed the patent to require that the
landing gear assemblies recited in the claims be used to
replace original landing gear assemblies. Second, it
asserts that the court erred in concluding as a matter of
TEXTRON INNOVATIONS   v. AM EUROCOPTER                     8


law that there was no infringement, either literally or
under the doctrine of equivalents. Textron contends that
a reasonable fact finder could find that the gasket and the
stop pieces of the accused design satisfy the “strap” limi-
tations, either literally or by equivalents, including the
limitation requiring the outer surface of the strap to have
“a stop surface for mating with the bracket.”

                             A

    Textron first argues that the district court erred by
limiting the claim solely to replacement landing gear
assemblies because such an interpretation impermissibly
reads a use limitation into an apparatus claim. According
to Textron, the fact that the claim was written in Jepson
format confirms that the patented invention was meant to
replace the prior art, not that it was intended to cover
only replacement landing gear assemblies. Eurocopter
disagrees, arguing that the amendment to the claim
supports the court’s construction that the claimed landing
gear assemblies must be suitable for, and used as, re-
placement assemblies.

    When a patentee “uses the claim preamble to recite
structural limitations of his claimed invention, the PTO
and courts give effect to that usage.” Rowe v. Dror, 112
F.3d 473, 478 (Fed. Cir. 1997). However, when a patentee
“defines a structurally complete invention in the claim
body and uses the preamble only to state a purpose or
intended use for the invention, the preamble is not a
claim limitation.” Id.; see Pitney Bowes, Inc. v. Hewlett-
Packard Co., 182 F.3d 1298, 1305 (Fed. Cir. 1999) (ex-
plaining that if “the body of the claim fully and intrinsi-
cally sets forth the complete invention, including all of its
limitations, and the preamble offers no distinct definition
of any of the claimed invention’s limitations, but rather
9                    TEXTRON INNOVATIONS    v. AM EUROCOPTER


merely states, for example, the purpose or intended use of
the invention, then the preamble is of no significance to
claim construction because it cannot be said to constitute
or explain a claim limitation”); Corning Glass Works v.
Sumitomo Elec. U.S.A., Inc., 868 F.2d 1251, 1257 (Fed.
Cir. 1989); Kropa v. Robie, 187 F.2d 150, 152 (CCPA
1951). The question whether the court should “treat a
preamble as a limitation is a determination ‘resolved only
on review of the entire . . . patent to gain an understand-
ing of what the inventors actually invented and intended
to encompass by the claim.’” Catalina Mktg., 289 F.3d at
808, quoting Corning Glass, 868 F.2d at 1257.

     In certain circumstances functional language may be
used to add limitations to an apparatus claim. See K-2
Corp. v. Salomon S.A., 191 F.3d 1356, 1363 (Fed. Cir.
1999); Wright Med. Tech., Inc. v. Osteonics Corp., 122
F.3d 1440, 1443-44 (Fed. Cir. 1997). In cases in which
functional language adds a structural limitation to an
apparatus claim, however, it does so because the language
describes something about the structure of the apparatus
rather than merely listing its intended or preferred uses.
See, e.g., K-2, 191 F.3d at 1363 (“[T]he functional lan-
guage tells us something about the structural require-
ments of the attachment between the bootie and the base
[of an inline skate] . . . .”). By contrast, in this case there
is nothing about the term “replacement” that dictates any
structural feature for the claimed limitation. See IMS
Tech., Inc. v. Haas Automation, Inc., 206 F.3d 1422, 1434
(Fed. Cir. 2000) (“The phrase ‘control apparatus’ in the
preamble merely gives a descriptive name to the set of
limitations in the body of the claim that completely set
forth the invention. Its use does not limit the claims . . .
to a control apparatus that is separate from the machine
tool. The claim is infringed by any apparatus encompass-
ing all of the limitations in the body of the claim.”).
TEXTRON INNOVATIONS   v. AM EUROCOPTER                   10


    This case differs from Rowe, cited by Eurocopter, be-
cause the court in Rowe found that the term “angioplasty”
in the preamble phrase “balloon angioplasty catheter”
imposed structural limitations on the claimed catheter
rather than merely specifying its intended use. 112 F.3d
at 479. In Rowe, the court explained, the specification
indicated “a particular and distinct structural meaning
for ‘balloon angioplasty catheter’ that distinguishes it
from ‘balloon catheters’ generally. In particular, an
angioplasty catheter must be capable of ‘expand[ing] a
stenosis in a coronary artery.’” Id. at 479-80. The court
thus limited the claims to “catheters that can be inflated
radially outward to dilate a narrowed region in a blood
vessel.” Id. at 480. In Rowe, the specific use of the cathe-
ter for angioplasty dictated the structure that the cathe-
ter needed to have—it had to have the capacity to be
“inflated radially outward.” Here, in contrast, the term
“replacement” does not impose any structural limitations
on landing gear assemblies used as replacement parts
that differ from the structure of original equipment
landing gear assemblies that satisfy the limitations in the
body of the claim.

    Moreover, the entire preamble consists of a general
description of the context in which the “improvement”
recited in the body of the claim is situated. The other
portions of the preamble describe the landing gear assem-
bly as being “of the type having a bracket extending from
the helicopter fuselage into engagement with a strap on
top of a generally cylindrical crosstube that supports
landing devices,” in which “the bracket engag[es] the
strap and stabiliz[es] the fuselage with respect to the
crosstube.” Those portions of the preamble plainly con-
tain words of context, not limitation. They describe the
general type of landing gear assembly for which the claim
provides an improvement, and they describe the function
11                  TEXTRON INNOVATIONS   v. AM EUROCOPTER


of the bracket-strap combination in stabilizing the fuse-
lage with respect to the crosstube. They do not, however,
prescribe the particular limitations of the invention. In
that setting, the reference to “replacement helicopter
landing gear assembly” likewise should not be interpreted
as a limitation of the claim.

    In support of its argument that the term “replace-
ment” is limiting and confines the claimed invention to
devices used to replace original equipment, Eurocopter
points out that Textron added the term “replacement”
during the prosecution of the ’242 patent in order to
overcome the examiner’s initial rejection. Eurocopter
asserts that the amendment of the claim language neces-
sarily means that Textron intended to limit the claim to
replacement assemblies. But the prosecution history does
not support that inference. Claim 10 was initially re-
jected as obvious in view of U.S. Patent No. 3,716,208 to
Fagan. 1 The examiner rejected the claim because Fagan
disclosed a similar strap design. In response, Textron
amended the claims. The amended claims not only added
the term “replacement” to the preamble but, more impor-
tantly, added the limitation that the strap is “otherwise
imperforate to minimize stress concentration.” That
amendment was important because Textron’s strap had
fewer holes in it than the Fagan strap, and the holes were
in a different location. The amendment explained that
the “imperforate” limitation meant that Fagan did not
anticipate the invention: “Fagan teaches away from


     1  Although portions of the prosecution history were
directed to claim 1, that claim is almost identical to claim
10, and the examiner treated the claims similarly. Be-
cause the claims do not differ in any respect that is perti-
nent to this appeal, we do not distinguish between them
for purposes of analyzing the prosecution history.
TEXTRON INNOVATIONS   v. AM EUROCOPTER                     12


locating the fastener holes only near the neutral bending
axis of the crosstube.”

    Addressing the obviousness rejection, Textron focused
on two critical limitations of each claim: “the fastener
holes being only near the neutral bending axis of the
crosstube” and the particular material strength and
fatigue ratios specific to each claim. According to Tex-
tron, “Fagan teaches away from locating the fastener
holes only near the neutral bending axis” of the crosstube
and “teaches away from using the materials claimed in
claim 10 in that instead of teaching a particular material
to use, Fagan teaches the use of [a] liquid spring shock
unit.” Notably, the amended application was silent as to
why the term “replacement” was added. There was no
express statement in the amendment or elsewhere that
the term “replacement” was added to overcome the rejec-
tion by limiting the invention to replacement parts only.

     In the context of the entire patent, it is apparent that
the term “replacement” is intended to describe the princi-
pal intended use of the invention, but not to import a
structural limitation or exclude from the reach of the
claims any assembly that happens to be used as original
equipment. The specification mentions the use of the
crosstubes “as replacements for the old crosstubes,” ’242
patent, col. 4, ll. 23-25, and it also refers to using the
crosstubes to replace prior art crosstubes, see id. at col. 4,
ll. 25-27 (“The prior art crosstubes that this preferred
embodiment is designed to be a replacement for . . . .”); id.
at col. 1, ll. 54-57 (“It would be beneficial to have a re-
placement landing gear assembly that would have a
substantially longer service life than the prior art landing
gear assemblies.”). But nothing in the specification or the
prosecution history states, or even suggests, that Textron
intended to exclude landing assemblies that were struc-
13                  TEXTRON INNOVATIONS   v. AM EUROCOPTER


turally identical to its claimed assemblies but were in-
stalled as original equipment. See Grober v. Mako Prods.,
Inc., 686 F.3d 1335, 1342 (Fed. Cir. 2012) (explaining that
ambiguous statements made during prosecution “do not
disavow or even clearly describe the structure” and that
such “reexamination commentary cannot fairly limit the
characteristics of the claim term”). Therefore, we reverse
the district court’s grant of summary judgment in favor of
Eurocopter on this ground.

                            B

    Textron next argues that the district court erred in
concluding that the accused devices could not infringe the
’242 patent because they failed to satisfy the limitation
requiring the strap to have a stop surface for mating with
the bracket. Textron asserts that nothing in the patent
requires the strap to be a unitary structure and that the
combination of the rubber gasket and the two stop pieces
satisfies that limitation. Alternatively, Textron argues
that the combination in the accused devices satisfies that
limitation under the doctrine of equivalents.

     The district court based its summary judgment of no
literal infringement on its conclusion that the accused
assembly does not contain a “strap” as required by the
claims of the ’242 patent. Because the court rejected
Textron’s argument that the rubber gasket and the two
stop pieces in the accused assembly taken together consti-
tute the “strap” that is attached to the cross-piece and
mates with the bracket, the court held as a matter of law
that the accused assembly did not infringe. Textron
argues that if those three components can constitute the
strap, as that term is used in the ’242 patent, the con-
tested limitations of the claims would be satisfied: The
inner surface of the rubber gasket portion of the strap
TEXTRON INNOVATIONS   v. AM EUROCOPTER                   14


would engage the crosstube, and the combination of the
rubber gasket and the stop pieces would contact and mate
with the bracket to minimize the lateral movement of the
bracket over the rubber gasket portion of the strap.

     We disagree with the district court that, as a matter
of law, the three-piece structure in accused assembly—the
rubber gasket and the two stop pieces—cannot qualify as
the “strap” recited in the asserted claims. In general, “the
mere depiction of a structural claim feature as unitary in
an embodiment, without more, does not mandate that the
structural limitation be unitary.” Cross Med. Prods., Inc.
v. Medtronic Sofamor Danek, Inc., 424 F.3d 1293, 1309
(Fed. Cir. 2005), citing CCS Fitness, Inc. v. Brunswick
Corp., 288 F.3d 1359, 1367 (Fed. Cir. 2002). Unless the
claims, the specification, or the prosecution history re-
quire that the particular component be a single, one-piece
structure, a court normally will not read that limitation
into the claim. E.g., Utica Enters., Inc. v. Fed. Broach &
Mach. Co., 109 F. App’x 403, 407-08 (Fed. Cir. 2004).

    Nothing in the claims, the specification, or the prose-
cution history indicates that the recited strap must be a
unitary structure. There is therefore no legal bar to
treating the combination of the rubber gasket and the two
stop pieces in the accused landing gear assembly as the
claimed strap. And if those three components constitute
the strap, there is ample evidence to show that the
bracket engages the strap and that the strap has “an
outer surface including a stop surface for mating with the
bracket.”    Because this issue cannot be resolved as a
matter of law but presents a factual question, we hold
that the district court erred in granting summary judg-
ment of no infringement based on the court’s conclusion
that the rubber gasket and the two stop pieces in Euro-
copter’s assembly cannot constitute the claimed “strap.”
15                  TEXTRON INNOVATIONS   v. AM EUROCOPTER


    Eurocopter makes a separate argument that the limi-
tation in the asserted claims that the strap be “imperfo-
rate” (with the exception of the fastener holes) means that
it cannot consist of more than one piece. Textron re-
sponds that the term “imperforate” relates only to the
number of holes in the strap, not to whether the strap
consists of one piece or more. The district court did not
address that issue in its summary judgment order.
Because that issue of claim construction was not resolved
by the district court, we decline to address it on appeal
and leave it to the district court to address in the first
instance on remand. In re Katz Interactive Call Process-
ing Patent Litig., 639 F.3d 1303, 1321 (Fed. Cir. 2011);
Metro. Life Ins. Co. v. Bancorp Servs., L.L.C., 527 F.3d
1330, 1336 (Fed. Cir. 2008); Nazomi Commc’ns, Inc. v.
ARM Holdings, PLC, 403 F.3d 1364, 1371 (Fed. Cir.
2005).

    Apart from the issue of literal infringement, Textron
argues that the district court improperly granted sum-
mary judgment on its claim that Eurocopter’s accused
landing gear assembly infringes under the doctrine of
equivalents. We agree with Textron that it has raised a
genuine issue of material fact as to infringement under
the doctrine of equivalents, and we therefore reverse the
district court’s ruling on that issue.

    Under the doctrine of equivalents, “a product or proc-
ess that does not literally infringe upon the express terms
of a patent claim may nonetheless be found to infringe if
there is ‘equivalence’ between the elements of the accused
product or process and the claimed elements of the pat-
ented invention.” Warner-Jenkinson Co. v. Hilton Davis
Chem. Co., 520 U.S. 17, 21 (1997); see Voda v. Cordis
Corp., 536 F.3d 1311, 1324 (Fed. Cir. 2008). The doctrine
seeks to prevent “[u]nimportant and insubstantial substi-
TEXTRON INNOVATIONS   v. AM EUROCOPTER                  16


tutes for certain elements” from defeating the patent and
destroying the patent’s value “by simple acts of copying.”
Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535
U.S. 722, 731 (2002). To prove infringement under the
doctrine, the patentee must show that the accused device
“performs substantially the same function in substan-
tially the same way to obtain the same result.” Graver
Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605,
608 (1950); see Dawn Equip. Co. v. Ky. Farms, Inc., 140
F.3d 1009, 1015 (Fed. Cir. 1998).

    The evidence in the summary judgment record was
sufficient to preclude summary judgment on the issue of
whether the structure used in the accused assembly to
prevent lateral movement of the crosstube is equivalent to
the strap of the ’242 patent. The record in this case
demonstrates—and the parties do not appear to dispute—
that the accused structure performs substantially the
same function as the strap disclosed in the ’242 patent:
Both serve to limit the lateral movement of the crosstube
vis-à-vis the fuselage of the helicopter. It is also undis-
puted that the accused device produces the same result as
the patented invention: Again, both structures limit the
lateral movement of the crosstube. The question is
whether the accused device achieves that result in sub-
stantially the same way as the patented invention. We
believe that fact question is one on which a jury could
properly find for the plaintiff, and thus summary judg-
ment for the defendants was improper. See, e.g., Pressure
Prods. Med. Supplies, Inc. v. Greatbatch Ltd., 599 F.3d
1308, 1318 (Fed. Cir. 2010); U.S. Philips Corp. v. Iwasaki
Elec. Co., 505 F.3d 1371, 1380 (Fed. Cir. 2007).

    Eurocopter argues that Textron’s doctrine of equiva-
lents argument is barred as a matter of law for two rea-
sons.    First, it argues that the “all-elements rule”
17                  TEXTRON INNOVATIONS   v. AM EUROCOPTER


precludes the application of the doctrine of equivalents.
The all-elements rule bars a patentee from asserting “a
theory of equivalence [that] would entirely vitiate a
particular claim element.” DePuy Spine, Inc. v. Medtronic
Sofamor Danek, Inc., 567 F.3d 1314, 1323 (Fed. Cir.
2009), quoting Warner-Jenkinson, 520 U.S. at 39 n.8.
Second, Eurocopter argues that prosecution history
estoppel bars Textron from asserting a scope of equiva-
lency surrendered during prosecution. See DePuy Spine,
567 F.3d at 1323; see also Festo Corp., 535 U.S. at 732.

    We reject Eurocopter’s contention that Textron’s
equivalence argument ignores “the limitation that the
lateral movement of the bracket that must be minimized
is ‘on the strap,’” because we conclude that Textron’s
argument would not entirely vitiate the limitation recit-
ing the structure of the strap. If the rubber gasket/stop
piece combination is viewed as being equivalent to the
“strap” in the ’242 patent, there is nothing to suggest that
the lateral movement of the bracket sought to be mini-
mized would not occur “on the strap”; that is, on the
rubber gasket/stop piece combination.

    We also reject Eurocopter’s claim of prosecution his-
tory estoppel. Although the ’242 patent specification
describes the stop surfaces on the strap and how the strap
is attached to the crosstube, it says nothing more about
the structure of the strap. The prosecution history—
including the addition of the “imperforate” limitation—
appears to be aimed at avoiding the Fagan prior art
reference, which taught having rivet holes at the top of
the strap and crosstube. The amendment explains that,
unlike Fagan, “the strap fastener holes [are] located only
near the neutral bending axis for the crosstube” and that
the reason for positioning the holes in that location “is to
avoid the problems previously associated with fastener
TEXTRON INNOVATIONS   v. AM EUROCOPTER                  18


holes located away from the neutral bending axis [which]
resulted in premature crack initiation at those holes.”
Fagan, in contrast, “shows fastener holes located at the
very top of [the strap], this being the location of highest
stress.” Eurocopter has not pointed to anything other
than the term “imperforate” that would suggest that
having a strap made of three different pieces was some-
how disclaimed by the amendment to overcome the Fagan
rejection. Making the strap out of separate pieces (such
as a gasket and stop pieces) does not create a need for
more holes in the crosstube itself, which is what is dis-
closed in Fagan. 2 For the foregoing reasons, we reverse
the judgment of the district court and remand for further
proceedings.

            REVERSED and REMANDED



   2     Eurocopter argues that using a bracket that
clamps around the crosstube was already known in the
prior art, as shown in a patent issued to a Eurocopter
affiliate, U.S. Patent No. 5,211,359. Eurocopter asserts
that in light of that patent, it would have been obvious to
use the stop pieces and gasket attachment mechanism,
and that “it would be improper to expand the claims
under the doctrine of equivalents to cover this structure.”
Eurocopter is correct that as a general proposition, the
defense of “[e]nsnarement bars a patentee from asserting
a scope of equivalency that would encompass, or ‘ensnare’
the prior art” and that this is “a legal limitation on the
doctrine of equivalents to be decided by the court.” DePuy
Spine, 567 F.3d at 1322. The district court, however,
never assessed “the prior art introduced by the accused
infringer” to determine whether a hypothetical claim that
covers the accused device would have been unpatentable
under 35 U.S.C. §§ 102 or 103. See id. at 1325. As with
the claim construction issue, we decline to address that
issue for the first time on appeal and leave it to the dis-
trict court to address on remand.
