Robert Bosch LLC v. Westport Fuel Systems Canada Inc.

NOTE: This disposition is nonprecedential.

United States Court of Appeals
for the Federal Circuit
______________________

ROBERT BOSCH LLC, MERCEDES-BENZ USA,
LLC,
Appellants

v.

WESTPORT FUEL SYSTEMS CANADA INC.,
Appellee
______________________

2025-1455, 2025-1456
______________________

Appeals from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in Nos. IPR2023-
00292, IPR2023-00293.
______________________

Decided: August 18, 2026
______________________

M
ELANIE L. BOSTWICK, Orrick, Herrington & Sutcliffe
LLP, Washington, DC, argued for all appellants. Appellant
Robert Bosch LLC also represented by KATHERINE M.
KOPP; BAS DE BLANK, Menlo Park, CA; JOSEPH RAYMOND
KOLKER, New York, NY.

MIRANDA Y. JONES, Winstead PC, Dallas, TX, argued for
appellee. Also represented by CODY MACJACKSON CARTER,
DAVID WILLIAM HIGER.
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ROBERT BOSCH LLC v. WESTPORT FUEL SYSTEMS CANADA INC. 2

CELINE JIMENEZ CROWSON, Hogan Lovells Cadwalader
US LLP, Washington, DC, for appellant Mercedes-Benz
USA, LLC. Also represented by J
OSEPH JAMES RAFFETTO,
NICHOLAS ROTZ.
______________________

Before C
HEN, CUNNINGHAM, and STARK, Circuit Judges.
STARK, Circuit Judge.
Westport Fuel Systems Canada Inc. (“Westport”) is the
owner of U.S. Patent Nos. 6,298,829 (the “’829 patent”) and
6,575,138 (the “’138 patent”), which relate to “an injection
valve . . . which includes a passive hydraulic link.” J.A. 94
(’829 pat. 1:12-17), J.A. 111 ( ’138 pat. 1:16-21). Robert
Bosch LLC and Mercedes-Benz USA, LLC (together
“Bosch”) filed petitions for inter partes review (“IPR”) of
various claims of the ’829 and ’138 patents. In two final
written decisions, the Patent Trial and Appeal Board
(“Board”) found that Bosch failed to prove that any of the
challenged claims would have been obvious. Bosch now ap-
peals, and we affirm.
I
The ’829 and ’138 patents share a title, “Directly Actu-
ated Injection Valve,” and a materially identical specifica-
tion.
1
Both relate generally to fuel injector valves for an
internal combustion engine. Figure 1, reproduced below, is
a cross-section view of a preferred embodiment. J.A. 97
(8:23-24).

1
Because there are no material differences between
the patents with respect to the issues presented in this ap-
peal, we cite only to the ’829 patent and the final written
decision relating to it, unless otherwise noted.
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ROBERT BOSCH LLC v. WESTPORT FUEL SYSTEMS CANADA INC. 3
J.A. 89. Fuel exits the valve through valve tip 106. J.A. 97
(8:45-49). Needle spring 116 exerts a closing force when
the system is at rest, preventing any fuel from exiting the
valve. J.A. 98 (9:16-34). During actuation, by contrast, an
opening force is generated by the magnetostrictive actuator
(the combination of elements 130, 132, and 134), which
“provides an opening force in opposition to the closing force
of the spring assembly.” J.A. 98 (9:45-10:8). That opening
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ROBERT BOSCH LLC v. WESTPORT FUEL SYSTEMS CANADA INC. 4
force overcomes the closing force, allowing fuel to exit the
valve. J.A. 98 (9:36-38).
The opening force is transmitted through the hydraulic
link assembly, which i ncludes hydraulic cylinder 160, con-
taining a “viscous hydraulic fluid.” J.A. 98-99 (10:62-11:6).
The hydraulic fluid preferably “acts as an incompressible
solid when activation of the actuator assembly” occurs,
thereby allowing “ a valve opening force to be quickly trans-
mitted through the hydraulic fluid.” J.A. 99 ( 11:21-26). In
this respect, then, “ hydraulic fluid 164b acts as a solid and
transfers the movement . . . to valve needle 114,” resulting
in the valve opening. J.A. 99 ( 12:57-64).
Claim 1 of the ’829 patent is representative for pur-
poses of this appeal. Only limitation 1(e) is in dispute. It
recites:
a hydraulic link assembly comprising a passive hy-
draulic link having a hydraulic fluid thickness
through which said opening and closing forces are
transmitted, whereby said hydraulic fluid acts
substantially as a solid with said thickness being
substantially constant while said actuator assem-
bly is activated and wherein said thickness of said
hydraulic link is adjustable while said actuator is
not activated in response to changes in the dimen-
sional relationship between components of said in-
jection valve to maintain a desired valve needle lift
upon activation of said actuator assembly.
J.A. 102 (17:32-43) (emphasis added).
Bosch contended in its petition that claim 1 would have
been obvious over a combination of prior art references
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ROBERT BOSCH LLC v. WESTPORT FUEL SYSTEMS CANADA INC. 5
Wirbeleit
2
and Klügl.
3
The Board understood that Bosch
relied on Klügl to teach a hydraulic link that “acts substan-
tially as a solid with said thickness being substantially con-
stant while said actuator assembly is activated.” J.A. 10-
11. Specifically, Bosch relies on the embodiment depicted
in Klügl’s Figure 1, reproduced below.
J.A. 11 (annotated by Bosch). The Board was persuaded by
Bosch that Klügl’s p ressure chamber 5 (pink) is filled with
a hydraulic fluid of “low compressibility,” which is “defined
and sealed by a membrane 6.” J.A. 11-12. It was undis-
puted, therefore, that Klügl discloses “a hydraulic fluid
thickness through which said opening and closing forces
are transmitted.” Bosch further argued that “the dimen-
sions of chamber 5 – including its thickness – remain con-
stant so that the movement of the actuator results in the
same amount of movement of the piston.” J.A. 12 (citing
J.A. 169). The Board rejected this contention, finding in-
stead that “ Klügl expressly teaches that membrane 6 is
‘flexible.’” J.A. 15-16 ( first quoting J.A. 1393 (7:45-47)

2
U.S. Patent No. 5,479,902.

3
Certified translation of German Patent No. 19708304.
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ROBERT BOSCH LLC v. WESTPORT FUEL SYSTEMS CANADA INC. 6
(“[F]lexible membranes 6, 8, 26 . . . have a progressive char-
acteristic curve of the spring force in relation to the spring
deflection.”); and then quoting J.A. 1393 (7:68-9:31) (refer-
ring to “first flexible element (6)” and “first flexible mem-
brane (6)”)). The Board reasoned that because membrane
6 is flexible, it will flex during actuation. Thus, in the
Board’s view, Bosch failed to prove that Klügl satisfies lim-
itation 1(e)’s requirement that
the hydraulic fluid “acts
substantially as a solid with said thickness being substan-
tially constant.” J.A. 16.
Bosch appeals the Board’s determination that it failed
to prove the challenged claims obvious. We have jurisdic-
tion under 28 U.S.C. § 1295(a)(4)(A) and 35 U.S.C. § 141(c).
II
We “review the Board’s legal determinations de novo
and its factual findings for substantial evidence.” Camp-
bell Soup Co. v. Gamon Plus, Inc., 10 F.4th 1268, 1275
(Fed. Cir. 2021). “Obviousness is a question of law based
on underlying facts.” Id. Factual findings underlying an
obviousness conclusion include “[w]hat a reference
teaches.” In re Cuozzo Speed Techs., LLC, 793 F.3d 1268,
1280 (Fed. Cir. 2015). “In an inter partes review . . . the
petitioner shall have the burden of proving a proposition of
unpatentability by a preponderance of the evidence.” 35
U.S.C. § 316(e).
III
The only issue on appeal is whether the Board had sub-
stantial evidence to support its finding that Klügl does not
disclose limitation 1(e).
4
The disputed limitation requires,

4
To the extent Bosch is attempting on appeal to rely
on Wirbeleit as teaching limitation 1(e), it fails to show any
abuse of discretion in the Board’s finding that, in its peti-
tion, Bosch relied solely on Klügl for this limitation. See
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ROBERT BOSCH LLC v. WESTPORT FUEL SYSTEMS CANADA INC. 7
among other things, that “the hydraulic fluid acts substan-
tially as a solid,” which the Board found Klügl does not dis-
close, since Klügl’s membrane 6 is “flexible,” meaning the
fluid will change shape as the membrane flexes, which is
inconsistent with the behavior of a solid. J.A. 16 (emphasis
added).
Substantial evidence, relied on by the Board, supports
the Board’s finding. See, e.g., J.A. 17 (“Westport provides
ample evidence in the form of credible expert testimony
that Klügl only ever specifies and describes membrane 6 as
a flexible membrane or element, and, thus, the membrane
will tend to deform longitudinally upward where it con-
tracts the drive piston and bulge outward where uncon-
strained in the annular area . . . between the edge of the
drive piston 3 and the wall of transmission module 2.”) (in-
ternal quotation marks omitted). Klügl explicitly describes
membrane 6 as a “flexible membrane.” J.A. 1393 (7:44-46).
Nowhere does Klügl limit this description only to certain
embodiments. To the contrary, Klügl specifically refers to
“Fig[ure] 1 or 3” when explaining the “advantages with
flexible membrane 6,” providing support for the Board’s
reading of Klügl as disclosing a flexible membrane in both
its F igure 1 and 3 embodiments. J.A. 1393 (7:34-47) (em-
phasis added).
Bosch attempts to make much of the fact that Klügl’s
Figure 1 depicts a device “without stroke translation,”
while its Figure 3 embodiment operates “with stroke trans-
lation.” J.A. 1390 (1:41-46). According to Bosch, “stroke
translation” refers to a change in the amount of movement
from the actuator to the opening of the valve, such that if
there is “no stroke translation” (as in Klügl’s Figure 1) the
hydraulic fluid is required to achieve a constant thickness.

Netflix, Inc. v. DivX, LLC, 84 F.4th 1371, 1377 (Fed.
Cir. 2023) (“The Board is entitled to discretion in how it in-
terprets petitions.”).
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ROBERT BOSCH LLC v. WESTPORT FUEL SYSTEMS CANADA INC. 8
Yet the only evidence Bosch produced in support of its def-
inition of stroke translation was the declaration of its ex-
pert, Dr. Quinlan, see J.A. 293, which the Board found was
“undermined by incomplete and contradictory opinions,”
J.A. 23; see also J.A. 68 (’138 patent final written decision)
(“Dr. Quinlan’s testimony in many instances . . . is sub-
stantively incomplete and fraught with contradictions that
undermine the weight of his testimony.”); J.A. 71 (finding
Dr. Quinlan to be “contradicted by Klügl’s express disclo-
sure”).
5
The Board did not abuse its discretion in making
this credibility assessment. See Sierra Wireless, ULC
v. Sisvel S.p.A., 130 F.4th 1019, 1024 (Fed. Cir. 2025) ( as-
serting that Board’s credibility determinations are re-
viewed for abuse of discretion).
Bosch argues in the alternative that even if membrane
6 of Klügl is flexible, the Board lacked substantial evidence
to find that membrane 6 flexes during activation (also re-
ferred to as “actuation”), as is required of limitation 1(e).
Bosch predicates this contention on Klügl’s discussion of
movement of membrane 6 “in the rest position without be-
ing actuated.” J.A. 1391 (3:63-4:10). A reasonable mind
could accept the Board’s logical determination that if
Klügl’s membrane 6 is flexible and actually flexes when not
actuated, then it remains flexible and will flex when actu-
ated as well. J.A. 15; J.A. 66-68; see also Consol. Edison
Co. v. Nat’l Lab. Rels. Bd., 305 U.S. 197, 229 (1938) (defin-
ing substantial evidence as “such relevant evidence as a
reasonable mind might accept as adequate to support a
conclusion”).

5
The Board found, for example, that despite using cer-
tain terms like “stroke amplification” in his declaration,
Dr. Quinlan could not explain their meaning, instead ad-
mitting he had not “taken the time to do a formal analysis
on what amplification means.” J.A. 25 (citing J.A. 2799
(34:3-12)).
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ROBERT BOSCH LLC v. WESTPORT FUEL SYSTEMS CANADA INC. 9
Bosch’s additional arguments are also unpersuasive.
Bosch insists that “nothing in Klügl shows that membrane
6 can (let alone must) flex to such a degree that it mean-
ingfully changes the thickness of the hydraulic fluid during
actuation.” Open Br. 50. We agree, instead, with the
Board, which characterized this contention as nothing
more than “conclusory attorney argument, lacking any ci-
tation to the record or meaningful explanation.” J.A. 17.
Bosch also argues that a skilled artisan would “readily be
able to design Klügl’s injector” to minimize or avoid flexing
altogether. However, as the Board pointed out, this con-
tradicts Klügl’s repeated teachings that its membrane is
flexible. J.A. 21-22. Finally, we see no merit to Bosch’s
multiple allegations of procedural error.
IV
We have considered Bosch’s remaining arguments and
find them unpersuasive. Accordingly, the judgment of the
Board is affirmed.
AFFIRMED
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