        NOTE: This disposition is nonprecedential.


  United States Court of Appeals
      for the Federal Circuit
                     ______________________

                       GATOR TAIL, LLC,
                        Plaintiff-Appellant

                                    v.

        MUD BUDDY LLC, DBA MUD BUDDY
              MANUFACTURING,
               Defendant-Appellee

   ----------------------------------------------------------------------

                       GATOR TAIL, LLC,
                        Plaintiff-Appellant

                                    v.

   GO-DEVIL MANUFACTURING COMPANY OF
        LOUISIANA INCORPORATED,
     DBA GO-DEVIL MANUFACTURERS OF
               LOUISIANA, INC.,
               Defendant-Appellee
             ______________________

                      2014-1747, 2014-1748
                     ______________________

   Appeals from the United States District Court for the
Middle District of Louisiana in Nos. 3:08-cv-00125-BAJ-
RLB, 3:08-cv-00124-BAJ-RLB, Judge Brian A. Jackson.
                 ______________________
2                          GATOR TAIL, LLC   v. MUD BUDDY LLC




                 Decided: June 22, 2015
                 ______________________

     MATTHEW WOLF, Arnold & Porter LLP, Washington,
DC, argued for plaintiff-appellant. Also represented by
JOEL WILEY MOHRMAN, ANDERSON LAM CAO, McGlinchey
Stafford, Houston, TX.

    SAMUEL C. STRAIGHT, Ray Quinney & Nebeker P.C.,
Salt Lake City, UT, argued for defendant-appellee Mud
Buddy LLC. Also represented by JED H. HANSEN, Thorpe,
North & Western LLP, Sandy, UT.

    JOHN PARHAM MURRILL, Taylor, Porter, Brooks &
Phillips, Baton Rouge, LA, argued for defendant-appellee
Go-Devil Manufacturing Company of Louisiana Incorpo-
rated. Also represented by FREDRICK R. TULLEY.
                 ______________________

      Before MOORE, CLEVENGER, and WALLACH, Circuit
                       Judges.
CLEVENGER, Circuit Judge.
    Gator Tail, LLC appeals the decision of the district
court that the asserted patents are invalid as obvious, for
lack of written description, and as indefinite. Broussard v.
Go-Devil Mfg. Co., 29 F. Supp. 3d 753, 757 (M.D. La.
2014). This court has jurisdiction under 28 U.S.C.
§ 1295(a)(1) (2012). Because the district court’s conclusion
that the asserted claims are obvious was supported by
factual findings that are not clearly erroneous, we affirm.
                             I
    This case concerns United States Patent Nos.
7,052,340 (“the ’340 patent”) and 7,297,035 (“the ’035
patent”), collectively referred to as Gator Tail’s patents.
Both patents name Kyle Broussard as the sole inventor,
GATOR TAIL, LLC   v. MUD BUDDY LLC                       3



and essentially claim the same invention: a short-tail mud
motor with a horizontally mounted engine.
                              A
    “Mud motors” are boat motors designed for shallow
waters, and are primarily used in fishing and hunting. A
mud motor’s propeller is positioned near the water’s
surface so that the boat can maneuver in shallow water
and in water congested with mud and vegetation.
    The traditional mud motor, which dominated the
market from the 1970s until the early 2000s, is the long
tail motor. United States Patent No. 2,996,035 (“the
Torrey Patent”) describes one version of a long tail mud
motor. The Torrey Patent discloses a propulsion unit that
is mounted to the transom of a boat. It includes a motor
(M), with a horizontally oriented engine that directly
attaches to a propeller shaft (14). A belt (18) and pulleys
(16 and 17) drive motion of the propeller shaft. U.S.
Patent No. 2,996,035 (filed Dec. 3, 1958).




U.S. Patent No. 2,996,035 fig. 1.
    While the long tail mud motor provided for boat oper-
ation in shallow and muddy waters, it posed several
disadvantages. In particular, the long propeller shaft
4                           GATOR TAIL, LLC   v. MUD BUDDY LLC



means that these motors have a wide turning radius and
are difficult to maneuver. Relatedly, steering the long
propeller requires substantial space inside the boat.
    To avoid this problem with the long tail motors, com-
panies started looking to short tail mud motor designs.
United States Patent No. 5,741,165 (“the Saito Patent”)
discloses one such motor. Saito’s short tail motor was
designed to increase range of movement, decrease boat
space occupied by the motor, and incorporate a mounting
bracket that would also permit use of conventional out-
board motors on the same boat. See U.S. Patent No.
2,996,035 col. 1 ll. 45–51 (filed Jan. 27, 1996). To that end,
Saito discloses a propulsion system that can be attached
to the rear of a boat. It includes a vertically oriented
engine (104) which connects to a drive shaft (117). The
drive shaft, in turn, attaches to and drives motion in the
propeller shaft (123).




U.S. Patent No. 2,996,035 fig. 7.
   With this design, the propeller is shorter and that
means better steering, maneuverability, and control.
Broussard v. Go-Devil Mfg. Co., 29 F. Supp. 3d at 771.
GATOR TAIL, LLC   v. MUD BUDDY LLC                        5



However, because the Saito short tail design uses a verti-
cal engine and vertical drive shaft, it has to hang off the
back of a boat. And that creates balance problems. Id. at
775.
                              B
    Gator Tail’s ’035 patent is a continuation in part of
the ’340 patent. For the purposes of this appeal, the
patents essentially claim the same invention: a belt-
driven short tail mud motor with a horizontal engine
capable of being mounted to the transom of a small boat
in a manner common to outboard engines.




U.S. Patent No. 7,297,035 fig. 16 (filed May 22, 2006).
     The overall design of the Gator Tail motor is similar
to the Saito Patent, with two key differences. First, Gator
Tail’s patents require a horizontally oriented engine. See,
e.g., Broussard, 29 F. Supp. 3d at 797 (describing Gator
Tail’s patents as containing horizontal output engines).
Second, the engine connects directly to a timing belt drive
gear (104) that attaches to and drives motion in the
parallel propeller. Saito, on the other hand, does not
disclose a timing belt and it requires a vertical, not hori-
zontal, engine.
6                         GATOR TAIL, LLC   v. MUD BUDDY LLC



    As an example, claim 1 of the ’035 patent discloses:
    A marine craft comprising
    a hull comprising a transom; and
    a portable drive assembly temporarily attached to
    the transom, the portable drive assembly compris-
    ing
    an elongated drive housing enclosing an upper
    drive assembly and a lower driven assembly and a
    timing belt connecting the upper drive assembly
    to the lower driven assembly; and
    an engine mounting plate attached externally to
    the drive housing adjacent the upper drive assem-
    bly perpendicular to the drive housing;
    wherein the lower driven assembly comprises a
    propeller shaft at least a portion of which is en-
    closed within a shaft housing attached to the drive
    housing adjacent the driven assembly, the shaft
    housing extending in excess of 18 inches beyond
    the drive housing, and a propeller attached to the
    propeller shaft.
The other asserted claims depend from, or are essentially
identical to, this claim.
                            II
    Gator Tail alleged that defendants, Mud Buddy, LLC
(“Mud Buddy”) and Go-Devil Manufacturing Company of
Louisiana (“Go-Devil”) manufacture products that in-
fringe claims 1, 3–9, and 11–13 of the ’340 patent and
claims 1, 3–7, and 9–13 of the ’035 patent.
                            A
   After Gator Tail filed its complaints, Mud Buddy re-
quested an ex parte reexamination of both patents by the
United States Patent and Trademark Office (“PTO”).
GATOR TAIL, LLC   v. MUD BUDDY LLC                         7



During those reexamination proceedings, the examiner
initially rejected all the claims as obvious in light of the
Saito Patent and other references. After a series of ex-
changes between Mr. Broussard and the PTO, including
the introduction of expert declarations and additional
claims, the PTO confirmed all claims of the patents. In
relevant part, the PTO concluded that Mr. Broussard’s
expert successfully established “modification of the Saito
Patent proposed in the rejection would lead to significant
changes . . . which would not be obvious to one of ordinary
skill in the art.” Broussard, 29 F. Supp. 3d at 790.
                              B
     The district court held a three day bench trial on the
issue of patent validity. In its amended final judgment,
the district court held that all the claims of the ’340 and
’035 patents were invalid as either obvious, indefinite, or
failing the written description requirement.
    On appeal, Gator Tail raises three specific challenges
to the amended final judgment: (1) the holding of obvi-
ousness of the asserted claims of the ’340 and ’035 pa-
tents, (2) the holding that claim 1 of the ’340 patent is
invalid for lack of written description, and (3) the holding
that claims 1, 8, and 14 of the ’340 patent and claim 1 of
the ’035 patent are invalid as indefinite under 35 U.S.C.
§ 112. Claims 1 and 8 of the ’340 patent and claim 1 of the
’035 patent were all asserted claims. Because those claims
were held invalid as obvious, and we affirm that holding,
we do not address the alternative holding that those
claims are invalid on other grounds. Method claim 14 of
the ’340 patent was not listed as an asserted claim, but
the district court’s holding of invalidity includes claim 14,
and the obviousness analysis of the district court applies
as well to claim 14 of the ’340 patent, making the indefi-
niteness holding an alternative ground that we need not
reach.
8                          GATOR TAIL, LLC   v. MUD BUDDY LLC



    The district court’s obviousness analysis focused pri-
marily on claim 1 of the ’035 and claim 1 of the ’340
patent. The court determined the content of the two
claims was indistinguishable, and applied the same
reasoning to invalidate both. All the other asserted claims
depend from these claims. Building on its analysis of
claim 1 of the ’340 patent, the court made separate find-
ings that each asserted claim was obvious.
    As it relates to this appeal, the district court focused
on the Torrey and Saito Patents when assessing obvious-
ness. And the court found that there were only limited
ways to improve upon Torrey or Saito. What is more,
those improvements were merely predictable uses of prior
art elements. The court also found that one of ordinary
skill in the art is a person with an undergraduate educa-
tion in mechanical engineering and experience with
marine propulsions systems. Because, through the lens of
a person of ordinary skill, the asserted claims were mere-
ly a predictable combination of Saito and Torrey, the
district court held that the claims were invalid.
    First, the court considered whether it would be obvi-
ous to replace Saito’s vertical engine with a horizontal
one. Because Saito used a vertical drive shaft motor, the
whole propulsion unit had to hang off the back of a boat.
This, in turn, created balance problems. The court found
that one of ordinary skill would be motivated to solve this
balance problem by moving Saito’s engine further into the
boat—above the transom. And “the expert witnesses
tended to agree that in order to relocate the engine above
the transom, one of ordinary skill in the art would neces-
sarily substitute Saito’s vertical drive-shaft engine for a
horizontal drive-shaft engine.” Broussard, 29 F. Supp. 3d
at 775. In addition, the court was persuaded by expert
testimony that one of ordinary skill would use a timing
belt to connect a horizontal drive engine to the horizontal
propeller. Overall, the court concluded this was a case
where there were a limited number of design options
GATOR TAIL, LLC   v. MUD BUDDY LLC                        9



available. And one of ordinary skill would have seen the
benefit of upgrading Saito in the way Gator Tail’s patents
did.
    The district court then conducted a separate obvious-
ness inquiry, based primarily on the Torrey Patent. The
only significant limitation present in Gator Tail’s patents,
but missing from the Torrey Patent, is the elongated drive
housing. This drive housing refers to the overall housing
that contains the engine, the timing belt, and the connec-
tion to the propeller in the lower portion. And the district
court found that, like Mr. Broussard and the Saito inven-
tors, a person of ordinary skill would be motivated to
improve on the long tail motor with a short tail design.
Furthermore, implementing the short tail requires an
elongated drive housing. Therefore, the court concluded
that claim 1 of both patents was an obvious combination
of prior art elements.
    Concluding that the defendants established a prima
facie case of obviousness, the district court then consid-
ered Gator Tail’s evidence of secondary considerations—
as potentially objective evidence of non-obviousness. The
court determined that Gator Tail’s evidence of commercial
success was not enough to support a finding of non-
obviousness. Similarly, the court was not persuaded by
Gator Tail’s arguments of unexpected results, long unmet
need, failure of others, or copying.
                              II
    On appeal, Gator Tail makes three main arguments
challenging the district court’s obviousness analysis: that
the court failed to give proper deference to the PTO, that
the Saito reference teaches away from the claimed inven-
tion, and that the court failed to correctly consider evi-
dence of Gator Tail’s commercial success.
    Obviousness is a question of law, which this Court re-
views de novo, and underlying factual questions are
10                        GATOR TAIL, LLC   v. MUD BUDDY LLC



reviewed for clear error. Scanner Techs. Corp. v. ICOS
Vision Sys. Corp. N.V., 528 F.3d 1365, 1379 (Fed. Cir.
2008).
                            A
    Gator Tail complains that the district court misunder-
stood the nature of PTO reexamination proceedings,
which led the court to misapply the presumption of validi-
ty. Brief for Plaintiff-Appellant at 35–36, Gator Tail v.
Mud Buddy, Nos. 14-1747, 14-1748 (Fed. Cir. Nov. 3
2014); see also 35 U.S.C. § 282. According to Gator Tail,
the court overemphasized the PTO’s interim rejections,
and therefore found that the “ultimate acceptance of those
patents was half-hearted and due little deference.” Brief
for Plaintiff-Appellant at 35.
    District courts are directed to consider a PTO reexam-
ination decision as evidence when determining invalidity.
Fromson v. Advance Offset Plate, Inc., 755 F.2d 1549,
1555 (Fed. Cir. 1985). While the court must consider the
reexamination as evidence, it is not bound by the PTO’s
decision. Id. at 1555. Here, the district court discussed
the PTO proceedings at length, and explained why it did
not afford substantial weight to the PTO’s decision.
    In particular, the court credited expert testimony in-
troduced during trial—testimony which was contrary to
declarations submitted during reexamination and which
undermined the PTO’s reasoning. Gator Tail’s expert
declaration to the PTO stated that one of ordinary skill
would be discouraged from reorienting the engine in Saito
to match the claimed horizontal engine. And the PTO
examiner relied heavily on that declaration when allow-
ing the patents. Broussard, 29 F. Supp. 3d at 782. Howev-
er, at trial, all parties’ experts admitted that one of
ordinary skill would be motivated to substitute the verti-
cal engine with a horizontal one to overcome balance
problems. See, e.g., Broussard, 29 F. Supp. 3d at 775–76,
782–83. The court considered the trial testimony to be a
GATOR TAIL, LLC   v. MUD BUDDY LLC                       11



more complete picture of the evidence, and concluded that
the PTO decision on reexamination deserved less weight.
The district court’s consideration of the PTO reexamina-
tion was not clearly erroneous.
                              B
    Next, Gator Tail argues that the Saito reference une-
quivocally teaches away from using a horizontal engine in
a short tail motor. And, where a reference teaches away
from the claimed invention, the patents are more likely to
be non-obvious. See KSR Int’l Co. v. Teleflex, 550 U.S. 398,
416 (2007). According to Gator Tail, the district court
disregarded Saito’s teaching away. However, we agree
with the district court that Saito does not teach away
from Gator Tail’s patents.
    A reference teaches away from a claimed invention
“when a person of ordinary skill, upon reading the refer-
ence, would be discouraged from following the path set
out in the reference, or would be led in a direction diver-
gent from the path that was taken by the applicant.” In re
Gurley, 27 F.3d 551, 553 (Fed. Cir. 1994). References may
also teach away if, when taking the two references in
combination, it would produce a “seemingly inoperative
device.” McGinley v. Franklin Sports, Inc., 262 F.3d 1339,
1354 (Fed. Cir. 2001).
    On the other hand, if a reference describes a modifica-
tion as “somewhat inferior,” then the reference does not
teach away. Gurley, 27 F.3d at 553. “A reference does not
teach away . . . if it merely expresses a general preference
for an alternative invention but does not ‘criticize, dis-
credit, or otherwise discourage’ investigation into the
invention claimed.” DePuy Spine, Inc. v. Medtronic So-
famor Danek, Inc., 567 F.3d 1314, 1327 (Fed. Cir. 2009).
     The Saito Patent does not teach away from the use of
horizontal motors. Instead, it describes the shortcomings
of long tail motors that use horizontal engines. For exam-
12                         GATOR TAIL, LLC   v. MUD BUDDY LLC



ple, the Saito Patent explains how the horizontal engine
motors that were on the market at the time took up too
much space in the boat. The Saito Patent also describes
the limited range of movement enabled by the long tail
motor. In fact, the Saito Patent states that it was “di-
rected towards several embodiments of outboard marine
propulsion systems that overcome the disadvantages of
the prior art . . .” U.S. Patent No. 5,741,165 col. 1 ll. 45–
55.
    Nowhere does Saito suggest that using a horizontal
engine would render the motor inoperable. It merely
describes the benefits of its vertical engine when com-
pared to the dominant prior art—the long tail motor.
These are not statements that would deter one of ordinary
skill from combining features of the long-tail motor with
the Saito Patent. See United States v. Adams, 383 U.S. 39,
52 (1966) (finding that one of ordinary skill in the art
would have to ignore long-accepted factors in the field of
wet batters to arrive at the claimed invention). In fact, the
district court heard several experts testify regarding why
one of ordinary skill in the art would be motivated to
replace Saito’s vertical motor with a horizontal one.
    The Saito Patent explains why it is an improvement
over the prior art—prior art that had a horizontal engine.
Therefore, Saito inevitably suggests that horizontal
engines are inferior to its vertical engine. However, these
statements do not teach away from Gator Tail’s invention.
                             C
    Finally, Gator Tail argues that the district court ap-
plied the wrong legal test when considering evidence of
commercial success. Any error by the district court was,
however, harmless error because Gator Tail has failed to
produce evidence of success suggesting the patents are
not obviousness.
GATOR TAIL, LLC   v. MUD BUDDY LLC                       13



    Evidence of commercial success is only relevant to the
obviousness inquiry if “there is a nexus between the
claimed invention and the commercial success.” Ormco
Corp. v. Align Tech., Inc., 463 F.3d 1299, 1312 (Fed. Cir.
2006). Where the marketed product is coextensive with
the claimed features, then the court should presume that
commercial success of the product is due to the patented
invention. Brown & Williamson Tobacco Corp. v. Philip
Morris Inc., 229 F.3d 1120, 1130 (Fed. Cir. 2000).
    According to Gator Tail, the district court failed to
presume that the company’s commercial success was due
to the patented invention. Instead, the court incorrectly
evaluated whether individual patented features were
present in the prior art. And where an individual feature
was present in the prior art, the court concluded it was
not relevant to commercial success.
    In this case, the parties do not dispute that the Gator
Tail product embodies the patents in question. Therefore,
the court should have presumed that any commercial
success of Gator Tail’s motors was a function of the
claimed patent. And that commercial success should have
weighed in favor of non-obviousness, unless the defend-
ants proved the alleged success was due to something
else. See Brown & Williamson, 229 F.3d at 1130 (once the
patentee shows that the patent and product are coexten-
sive, the “burden shifts to the party asserting obviousness
to present evidence to rebut the presumed nexus”).
    However, if there was any error in the district court’s
nexus analysis, it was harmless. In this case, Gator Tail’s
only evidence of commercial success is the fact that it sold
zero motors in 2004 and by 2014 it was selling one thou-
sand motors per year. Gator Tail has failed to establish
the overall size of the mud motor market, the size of the
short tail motor market, or any other facts that would
indicate whether selling one thousands units per year is a
commercial success in this industry.
14                         GATOR TAIL, LLC   v. MUD BUDDY LLC



    “This court has noted in the past that evidence related
solely to the number of units sold provides a very weak
showing of commercial success, if any.” In re Huang, 100
F.3d 135, 140 (Fed. Cir. 1996) (citing Cable Elec. Prods.,
Inc. v. Genmark, Inc., 770 F.2d 1015, 1026–27 (Fed. Cir.
1985)). Because Gator Tail failed to introduce any evi-
dence that establishes commercial success, the court’s
arguably flawed nexus analysis is harmless error.
                        CONCLUSION
    All of the claims at issue of the two patents in suit are
invalid under 35 U.S.C. § 103. The amended judgment of
the district court is affirmed.
                       AFFIRMED
     No costs.
