United States Court of Appeals
for the Federal Circuit
______________________
MTD PRODUCTS INC.,
Appellant
v.
ANDREI IANCU, UNDER SECRETARY OF
COMMERCE FOR INTELLECTUAL PROPERTY
AND DIRECTOR OF THE UNITED STATES
PATENT AND TRADEMARK OFFICE,
Intervenor
______________________
2017-2292
______________________
Appeal from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in No. IPR2016-
00194.
______________________
Decided: August 12, 2019
______________________
JOHN SALVATORE CIPOLLA, Calfee, Halter & Griswold
LLP, Cleveland, OH, argued for appellant. Also repre-
sented by ANDREW ALEXANDER, TRACY SCOTT JOHNSON,
MARK MCDOUGALL.
PETER JOHN SAWERT, Office of the Solicitor, United
States Patent and Trademark Office, Alexandria, VA, ar-
gued for intervenor. Also represented by THOMAS W.
KRAUSE, PHILIP J. WARRICK.
2 MTD PRODS. INC. v. IANCU
______________________
Before REYNA, TARANTO, and STOLL, Circuit Judges.
STOLL, Circuit Judge.
The Toro Company sought inter partes review of
claims 1–16 of U.S. Patent No. 8,011,458 before the U.S.
Patent and Trademark Office’s Patent Trial and Appeal
Board. The Board instituted review and, in its final writ-
ten decision, held the challenged claims obvious under
35 U.S.C. § 103. Critical to its decision, the Board deter-
mined that the claim term “mechanical control assem-
bly . . . configured to” perform certain functions is not a
means-plus-function term subject to 35 U.S.C. § 112, ¶ 6.
MTD Products Inc., owner of the ’458 patent, appeals the
Board’s decision.
We conclude that the Board erred by conflating corre-
sponding structure in the specification with a structural
definition for the term, and by misinterpreting certain
statements in the prosecution history. Under the appropri-
ate legal framework, we conclude that the term “mechani-
cal control assembly” is a means-plus-function term
governed by § 112, ¶ 6. We therefore vacate the Board’s
obviousness conclusion, which was predicated on its incor-
rect claim construction, and remand for further proceed-
ings consistent with this opinion. Because we are
persuaded by MTD’s primary argument, we do not reach
its alternative arguments.
BACKGROUND
I
The ’458 patent discloses a steering and driving system
for zero turn radius (“ZTR”) vehicles, with specific refer-
ence to ZTR lawn mowers. ’458 patent col. 1 ll. 17–21. The
patented system is designed to provide a more intuitive
steering mechanism to operators of ZTR vehicles. Id. at
col. 1 ll. 20–38. In contrast to prior art systems that
MTD PRODS. INC. v. IANCU 3
reverse in the opposite direction of a forward motion turn,
the claimed invention permits ZTR vehicles to turn in the
same direction both forward and backwards. Id. at col. 1
ll. 20–47. The claimed steering mechanism thus mimics
the forward and backward movements of an automobile.
The term “mechanical control assembly” appears in
both claims 1 and 9, the only independent claims of the
’458 patent. Claim 1 recites:
1. A vehicle capable of making a small radius turn,
comprising:
a frame;
a left drive wheel and a right drive wheel,
both coupled to the frame;
two independent left and right drive units,
the left drive unit coupled to the left drive
wheel via an axle and the right drive unit
coupled to the right drive wheel via another
axle;
a steering device coupled to the frame;
a speed control member coupled to the
frame; and
a mechanical control assembly coupled to
the left and right drive units that is config-
ured to actuate the left and right drive
units based on a steering input received
from the steering device and a speed input
received from the speed control member;
the mechanical control assembly being con-
figured such that if the speed control mem-
ber is shifted from (a) a forward position in
which the left drive wheel is rotating in a
forward direction at a first forward speed
and the right drive wheel is rotating in a
4 MTD PRODS. INC. v. IANCU
forward direction at a second forward
speed that is less than the first forward
speed as a result of the steering device be-
ing in a first right turn position to (b) a re-
verse position while the first right turn
position of the steering device is main-
tained, then the left drive wheel will rotate
in a reverse direction at a first reverse
speed and the right drive wheel will rotate
in a reverse direction at a second reverse
speed that is less than the first reverse
speed.
Id. at col. 7 l. 63–col. 8 l. 24 (emphasis added to highlight
portion of disputed claim term). Claim 9 is identical to
claim 1 in substantial part, adding only the further limita-
tion of:
the mechanical control assembly also being config-
ured to cause the vehicle to execute a zero-radius
turn when the speed control member is in a maxi-
mum forward position and the steering device is in
a maximum turn position.
Id. at col. 9 ll. 13–16 (emphasis added).
While the patent specification does not expressly refer
to a “mechanical control assembly,” it discloses a preferred
embodiment that includes a “ZTR control assembly.” Id. at
col. 3 ll. 41–42. The specification describes components of
the ZTR control assembly and its inputs, outputs, and link-
ages. Id. at col. 3 l. 41–col. 4 l. 57.
II
Toro petitioned for inter partes review of the ’458 pa-
tent in November 2015, arguing that the challenged claims
were invalid as anticipated or obvious. MTD responded
that the term “mechanical control assembly” is a means-
plus-function term, and that the asserted prior art did not
disclose the claim term’s corresponding structure. In
MTD PRODS. INC. v. IANCU 5
support of its argument, MTD introduced expert testimony
indicating that “mechanical control assembly” has no rea-
sonably well-understood meaning in the art. Specifically,
MTD’s expert testified that “mechanical control assembly”
is a nonce term that is not used in common parlance and
does not bring to mind any specific structure to a person of
ordinary skill in the art. J.A. 1366. He explained that the
term is used as a black box recitation for structure and, at
most, amounts to a collection of various parts. J.A. 1248,
1366. He further demonstrated that the term is used in
various prior patents and publications to describe a wide
variety of structures with varying functions. J.A. 1367–69
(noting that “mechanical control assembly” is used generi-
cally to describe mechanisms for infusion pumps, digital
firing systems, flush tanks, endoscopes, transmissions, and
engine outputs).
Toro did not expressly contradict MTD’s evidence that
“mechanical control assembly” did not have a well-under-
stood structural meaning. Instead, Toro responded that a
person of ordinary skill in the art would understand the
term to denote a specific structure in the context of the
’458 patent specification. Specifically, Toro argued that the
“ZTR control assembly” disclosed in the specification pro-
vides an express structural definition for the claimed “me-
chanical control assembly.” J.A. 2201–03. Toro also
argued that MTD admitted that the term “mechanical con-
trol assembly” conveys particular structure when it distin-
guished the patent claims from a prior art reference during
prosecution. J.A. 2203.
The Board initially agreed with MTD, stating that
when viewed “in isolation, the genericness of this term
bears similarities to other words or phrases that have been
held to be subject to § 112, ¶ 6 . . . such as ‘mechanism,’ ‘el-
ement,’ ‘device,’ ‘link member,’ and ‘control mechanism.’”
Toro Co. v. MTD Prods. Inc., No. IPR2016-00194,
2017 WL 1969747, at *9 (P.T.A.B. May 10, 2017) (first cit-
ing Williamson v. Citrix Online, LLC, 792 F.3d 1339, 1350
6 MTD PRODS. INC. v. IANCU
(Fed. Cir. 2015) (en banc); then citing Mas-Hamilton Grp.
v. LaGard, Inc., 156 F.3d 1206, 1215 (Fed. Cir. 1998); and
then citing Toro Co. v. Deere & Co., 355 F.3d 1313, 1325
(Fed. Cir. 2004)). The Board also determined that the “lan-
guage reciting what the mechanical control assembly is
‘configured to’ do . . . fits the mold of functional language
because it describes the mechanical control assembly by
what it does.” Id. The Board thus concluded that “the
claim language of the disputed phrase is primarily, but not
entirely, functional, which tends to favor [MTD]’s position
that § 112, ¶ 6 applies.” Id.
The Board agreed with Toro, however, that the ’458 pa-
tent specification weighed against application of § 112, ¶ 6.
Id. at *10. Citing the parties’ briefs, the Board stated that
“[t]he parties agree that the claimed ‘mechanical control
assembly’ is referred to in the specification as a ‘ZTR con-
trol assembly.’” Id. According to the Board, a person of
ordinary skill in the art would understand “mechanical
control assembly” to denote structure because “the specifi-
cation illustrates and describes the specific structure that
makes up the ZTR control assembly, and how it connects to
and operates with other components.” Id.
The most persuasive piece of evidence to the Board,
however, was the prosecution history. Id. at *9 (“The factor
that weighs most heavily in [the] determination is the pros-
ecution history.”). According to the Board, MTD admitted
that the term “mechanical control assembly” connotes spe-
cific structure by asserting that the claims recite “a me-
chanical control assembly that is structurally different
from what [the asserted prior art] discloses.” Id. The
Board emphasized MTD’s statements that “the claim lan-
guage at issue concerns the configuration of the claimed
mechanical control assembly” and “the claimed configura-
tion is indeed structural.” Id. (emphases in original). The
Board concluded that these statements “present[] strong
evidence that the disputed phrase should be understood as
a structural limitation rather than a means-plus-function
MTD PRODS. INC. v. IANCU 7
limitation under § 112 ¶ 6.” Id. at *11. Relying on the spec-
ification and prosecution history, the Board ultimately de-
termined that “mechanical control assembly” is not
governed by § 112, ¶ 6. Id.
DISCUSSION
I
This appeal requires us to address whether a particu-
lar claim limitation is drafted in means-plus-function for-
mat. Whether claim language invokes 35 U.S.C. § 112, ¶ 6 1
is a legal question of claim construction that we review de
novo. Williamson, 792 F.3d at 1346. We review the
Board’s factual findings underlying this inquiry for sub-
stantial evidence. EnOcean, GmbH v. Face Int’l Corp.,
742 F.3d 955, 959 (Fed. Cir. 2014).
Under this court’s guidance in Williamson, we begin by
asking whether the claim limitation employs the word
“means.” Williamson, 792 F.3d at 1348. If it does not, we
apply a rebuttable presumption that the term conveys suf-
ficiently definite structure and is not subject to § 112, ¶ 6.
Id. A challenger can rebut the presumption by demonstrat-
ing “that the claim term fails to ‘recite sufficiently definite
structure’ or else recites ‘function without reciting suffi-
cient structure for performing that function.’” Id. (quoting
Watts v. XL Sys., Inc., 232 F.3d 877, 880 (Fed. Cir. 2000)).
The “essential inquiry is not merely the presence or ab-
sence of the word ‘means’ but whether the words of the
1 Because the issue date of the ’458 patent is Septem-
ber 6, 2011, and neither the ’458 patent nor the application
from which it issued ever contained a claim with an effec-
tive filing date on or after September 16, 2012, the version
of 35 U.S.C. § 112 that applies here is the one preceding
the changes made by the America Invents Act. See Leahy-
Smith America Invents Act, Pub. L. No. 112-29, 125 Stat.
284, 296, § 4(c) (2011).
8 MTD PRODS. INC. v. IANCU
claim are understood by persons of ordinary skill in the art
to have a sufficiently definite meaning as the name for
structure.” Id.
One way to demonstrate that a claim limitation fails to
recite sufficiently definite structure is to show that, alt-
hough not employing the word “means,” the claim limita-
tion uses a similar “nonce word that can operate as a
substitute for ‘means’ in the context of § 112, para. 6.” Id.
at 1350. Generic terms like “module,” “mechanism,” “ele-
ment,” and “device” are commonly used as verbal con-
structs that operate, like “means,” to claim a particular
function rather than describe a “sufficiently definite struc-
ture.” Id. Our case law is replete with guidance on
whether or not a particular claim term is a “nonce” term.
See, e.g., Zeroclick, LLC v. Apple Inc., 891 F.3d 1003, 1008
(Fed. Cir. 2018) (holding that “program” and “user inter-
face code” are not nonce words because they are “used not
as generic terms or black box recitations of structure or ab-
stractions, but rather as specific references to conventional
graphical user interface programs or code”); Williamson,
792 F.3d at 1350 (noting that “module” is a nonce term be-
cause it “sets forth the same black box recitation of struc-
ture for providing the same specified function as if the term
‘means’ had been used”). In each case, a critical question
is whether “the claim term is used in common parlance or
by persons of skill in the pertinent art to designate struc-
ture,” including either a particular structure or a class of
structures. Skky, Inc. v. MindGeek, s.a.r.l., 859 F.3d 1014,
1019 (Fed. Cir. 2017) (citing TecSec, Inc. v. Int’l Bus.
Machs. Corp., 731 F.3d 1336, 1347 (Fed. Cir. 2013)) (hold-
ing that the claim term “wireless device means” does not
invoke § 112, ¶ 6 because it denotes a class of structures).
In addition, even if the claims recite a nonce term fol-
lowed by functional language, other language in the claim
“might inform the structural character of the limitation-in-
question or otherwise impart structure” to the claim term.
Williamson, 792 F.3d at 1351. In assessing whether the
MTD PRODS. INC. v. IANCU 9
claim limitation is in means-plus-function format, we do
not merely consider the introductory phrase (e.g., “mechan-
ical control assembly”) in isolation, but look to the entire
passage including functions performed by the introductory
phrase. See Apex Inc. v. Raritan Computer, Inc., 325 F.3d
1364 (Fed. Cir. 2003). The ultimate question is whether
“the claim language, read in light of the specification, re-
cites sufficiently definite structure to avoid § 112, ¶ 6.” Me-
dia Rights Techs. Inc. v. Capital One Fin. Corp., 800 F.3d
1366, 1372 (Fed. Cir. 2015) (citing Robert Bosch, LLC v.
Snap-On Inc., 769 F.3d 1094, 1099 (Fed. Cir. 2014)).
In Apex, for example, the court concluded that the term
“circuit” recited sufficient structure in the context of the
claims at issue. 325 F.3d at 1372–73 (considering the use
of the term “circuit” in the claim limitation “a first interface
circuit for receiving keyboard and cursor control device sig-
nals from the workstation”). Based on a dictionary defini-
tion of the word “circuit,” the court reasoned that “the term
‘circuit’ by itself connotes some structure,” and that “the
term ‘circuit with an appropriate identifier such as ‘inter-
face,’ ‘programming,’ and ‘logic,’ certainly identifies some
structural meaning to one of ordinary skill in the art.” Id.
at 1373. The court noted that the extrinsic evidence did
not show that the term “circuit” was not understood to have
structure, but rather “only that the term ‘circuit’ is under-
stood . . . as a very broad term.” Id. at 1374. As neither the
specification nor the prosecution history used the term “in
a manner clearly inconsistent with the ordinary meaning,”
the court held that the defendant failed to rebut the pre-
sumption that § 112, ¶ 6 did not apply. Id. at 1373–74.
In contrast, in Diebold Nixdorf, Inc. v. International
Trade Commission, the court held that the term “cheque
standby unit” for performing certain specified functions
was governed by § 112, ¶ 6. 899 F.3d 1291, 1300 (Fed. Cir.
2018). The court noted that “there is no evidence—in the
form of dictionary definitions or otherwise—that ‘cheque
standby unit’ was reasonably well understood by persons
10 MTD PRODS. INC. v. IANCU
of ordinary skill in the art to refer to a structure or class of
structures.” Id. at 1302. Instead, the extrinsic evidence
demonstrated only that “a skilled artisan would under-
stand the functional term ‘cheque standby unit’ to be any
structure capable of performing the claimed function.” Id.
at 1301. Further, neither the words of the claim nor the
specification suggested a “structural limitation that might
serve to cabin the scope of the functional term,” thus sup-
porting the conclusion that the claim limitation was writ-
ten in means-plus-function format. Id.
Finally, we note that “[c]laims are interpreted in light
of the written description supporting them, and that is true
whether or not the claim construction involves interpreting
a ‘means’ clause.” Inventio AG v. ThyssenKrupp Elevator
Ams. Corp., 649 F.3d 1350, 1356 (Fed. Cir. 2011), overruled
on other grounds by Williamson, 792 F.3d at 1339. For ex-
ample, a patentee may avoid application of § 112, ¶ 6 by
acting as a lexicographer and providing its own structural
definition of a nonce term in the specification by “‘clearly
set[ting] forth a definition of the disputed claim term’ other
than its plain and ordinary meaning.” Thorner v. Sony
Comput. Entm’t Am. LLC, 669 F.3d 1362, 1365 (Fed. Cir.
2012) (citing CCS Fitness, Inc. v. Brunswick Corp.,
288 F.3d 1359, 1366 (Fed. Cir. 2002)). Just as it is im-
proper to “import[] limitations from the specification into
the claims,” Phillips v. AWH Corp., 415 F.3d 1303, 1323
(Fed. Cir. 2005), however, a preferred embodiment dis-
closed in the specification cannot impart structure to a
term that otherwise has none. As with all lexicography,
“[i]t is not enough for a patentee to simply disclose a single
embodiment.” Thorner, 669 F.3d at 1365. Rather, “the pa-
tentee must ‘clearly express an intent’ to redefine the
term.” Id. (quoting Helmsderfer v. Bobrick Washroom
Equip., Inc., 527 F.3d 1379, 1381 (Fed. Cir. 2008)).
With these background principles in mind, we turn to
the claim language at issue in this case.
MTD PRODS. INC. v. IANCU 11
II
The disputed claim limitation is lengthy and recites:
a mechanical control assembly coupled to the left
and right drive units that is configured to actuate
the left and right drive units based on a steering
input received from the steering device and a speed
input received from the speed control member;
the mechanical control assembly being configured
such that if the speed control member is shifted
from (a) a forward position in which the left drive
wheel is rotating in a forward direction at a first
forward speed and the right drive wheel is rotating
in a forward direction at a second forward speed
that is less than the first forward speed as a result
of the steering device being in a first right turn po-
sition to (b) a reverse position while the first right
turn position of the steering device is maintained,
then the left drive wheel will rotate in a reverse di-
rection at a first reverse speed and the right drive
wheel will rotate in a reverse direction at a second
reverse speed that is less than the first reverse
speed.
’458 patent col. 8 ll. 7–24.
At the outset, we agree with the Board that the term
“mechanical control assembly” is similar to other generic,
black-box words that this court has held to be nonce terms
similar to “means” and subject to § 112, ¶ 6 because the
term does not connote sufficiently definite structure to one
of ordinary skill in the art. Toro, 2017 WL 1969747, at *9.
We also agree with the Board that the rest of the “claim
language of the disputed phrase is primarily, but not en-
tirely, functional.” Id. While the claim language reciting
that the mechanical control assembly is “coupled to the left
and right drive units” connotes structure, the claim lan-
guage reciting what the mechanical control assembly is
12 MTD PRODS. INC. v. IANCU
“configured to” do is functional. In this respect, as the
Board correctly recognized, the claim format tends to favor
MTD’s position that § 112, ¶ 6 applies. 2
We also discern no error in the Board’s acceptance of
MTD’s extrinsic evidence as showing that the term “me-
chanical control assembly” does not have an established
meaning in the art and instead merely operates as a ge-
neric label for a collection of parts. Toro did not dispute
MTD’s expert testimony that, in common parlance, “me-
chanical control assembly” does not bring to mind any spe-
cific structure to a person of ordinary skill in the art. J.A.
1366. Toro likewise did not dispute MTD’s reliance on var-
ious prior patents and publications that used “mechanical
control assembly” to describe a wide variety of structures
with varying functions. J.A. 1367–69 (noting that
2 The Board also stated that construing the disputed
phrase as a means-plus-function limitation “would seem to
render the second part [of the claim’s recitation of a ‘me-
chanical control assembly’] . . . superfluous” as it “would no
longer serve to define functionally the structural features
of the mechanical control assembly, as those features
would be part and parcel of what [MTD] alleges is the cor-
responding structure.” Toro, 2017 WL 1969747, at *9. We
disagree. Both the first and second limitations following
the two occurrences of the term “mechanical control assem-
bly” recite functions associated with the “mechanical con-
trol assembly”; i.e., (1) actuate the left and right drive units
and (2) rotate the wheel in a particular direction based on
the position of the speed control member. As we have held,
“[w]here there are multiple claimed functions, as we have
here, the patentee must disclose adequate corresponding
structure to perform all of the claim functions.” William-
son, 792 F.3d at 1351–52. Thus, the corresponding struc-
ture for “mechanical control assembly” in the specification
must perform both of these functions.
MTD PRODS. INC. v. IANCU 13
“mechanical control assembly” is used generically to de-
scribe mechanisms for infusion pumps, digital firing sys-
tems, flush tanks, endoscopes, transmissions, and engine
outputs).
We conclude that the Board erred, however, when it re-
lied on the specification’s description of a “ZTR control as-
sembly” to conclude that the claim term “mechanical
control assembly” has an established structural meaning.
While the parties agreed that the ZTR control assembly in
the specification is the structure “corresponding to” the
claimed mechanical control assembly, MTD did not agree
that the specification expressly defines the claim term “me-
chanical control assembly.” That the specification discloses
a structure corresponding to an asserted means-plus-func-
tion claim term does not necessarily mean that the claim
term is understood by persons of ordinary skill in the art to
connote a specific structure or a class of structures.
Interpretation of an asserted means-plus-function lim-
itation involves two steps. First, we determine if the claim
limitation is drafted in means-plus-function format. As
part of this step, we consider whether the claim limitation
connotes “sufficiently definite structure” to a person of or-
dinary skill in the art. If we conclude that the limitation is
in means-plus-function format, the second step requires us
to review the specification to identify the structure that
performs the claimed function(s) and thus “corresponds to”
the claimed means. While related, these two inquiries are
distinct. In this case, however, the Board conflated these
distinct inquiries, holding that the specification’s disclo-
sure of corresponding structure demonstrates that the al-
leged means-plus-function term is sufficiently definite so
as to not invoke § 112, ¶ 6. The Board’s analysis implies
that so long as a claim term has corresponding structure in
the specification, it is not a means-plus-function limitation.
This is not consistent with our prior decisions. Indeed, this
view would seem to leave § 112, ¶ 6 without any applica-
tion: any means-plus-function limitation that met the
14 MTD PRODS. INC. v. IANCU
statutory requirements, i.e., which includes having corre-
sponding structure in the specification, would end up not
being a means-plus-function limitation at all.
While we agree with the Board that the specification
plays a role in assessing whether particular claim language
invokes § 112, ¶ 6, we do not agree that the patent specifi-
cation at issue here renders the nonce term “mechanical
control assembly” sufficiently structural to a person of or-
dinary skill in the art. The specification does not demon-
strate that the patentee intended to act as its own
lexicographer and define the nonce term “mechanical con-
trol assembly” as the “ZTR control assembly” of the pre-
ferred embodiment. Indeed, the specification does not even
refer to a “mechanical control assembly.” Furthermore, the
functional language in the claim limitation suggests a
broader meaning of the generic term “mechanical control
assembly,” as it specifically adds to the “mechanical control
assembly” limitation the ability to execute a zero radius
turn. ’458 patent col. 9 ll. 13–16. Interpreting the “me-
chanical control assembly” as the “ZTR”—or zero-turn-ra-
dius—control assembly would render this functional
language superfluous.
We are also not persuaded by the Board’s interpreta-
tion of the prosecution history. While it would have
avoided uncertainty and argument had MTD shared its
current view that the claim limitation is written in means-
plus-function format during the original prosecution,
MTD’s statements did not clearly disclaim such an inter-
pretation. Rather, MTD’s statements indicated that the
phrase “mechanical control assembly configured to” per-
form certain functions must be given weight because it con-
notes structure and thus is not merely an intended use.
These statements were not made within the context of
§ 112, ¶ 6. Moreover, stating that the limitation connotes
structure and has weight is not inconsistent with claiming
in means-plus-function format since means-plus-function
limitations connote structure (i.e., corresponding structure
MTD PRODS. INC. v. IANCU 15
and their equivalents) and have weight. Furthermore, as
MTD explained, its interpretation of the claims as being in
means-plus-function format during inter partes review was
based on this court’s intervening law in Williamson.
J.A. 1204. Given the lack of any clear and undisputed
statement foreclosing application of § 112, ¶ 6, we conclude
that the Board erred in giving dispositive weight to the
equivocal statements it cited in the prosecution history.
CONCLUSION
We conclude that the Board erred by using the exist-
ence of corresponding structure in the specification to con-
clude that “mechanical control assembly” has a sufficiently
definite structure to evade § 112, ¶ 6. The Board also erred
by giving improper weight to out-of-context statements in
the prosecution history. We hold that the remaining evi-
dence and the Board’s factual findings demonstrate that
the term “mechanical control assembly . . . configured to”
perform certain functions in independent claims 1 and 9 of
the ’458 patent is governed by § 112, ¶ 6. We therefore va-
cate the Board’s decision and remand for further proceed-
ings consistent with this opinion.
VACATED AND REMANDED
COSTS
Costs to Appellant.