Durr Systems, Inc. v. Efc Systems, Inc.

N OTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
DURR SYSTEMS, INC.,
Plaintiff-Appellant
v.
EFC SYSTEMS, INC.,
Defendant-Appellee
______________________
2024-2158
______________________
Appeal from the United States District Court for the
District of Maryland in No. 1:18-cv-02597-SAG, Judge
Stephanie A. Gallagher.
______________________
Decided: March 20, 2026
______________________
J EFFREY A. L AMKEN, MoloLamken LLP, Washington,
DC, argued for plaintiff-appellant. Also represented by
L IDIYA M ISHCHENKO ; L AUREN F. D AYTON, ERIC J.
ROLSTON, New York, NY; T HOMAS E. BEJIN, WILLIAM K.
BROMAN, Taft Stettinius & Hollister LLP, Southfield, MI.
T RAVIS WILLIAM BLISS , Panitch Schwarze Belisario &
Nadel LLP, Wilmington, DE, argued for defendant-
appellee. Also represented by P HILIP L. HIRSCHHORN,
K EITH AARON J ONES , Philadelphia, PA.
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 2
______________________
Before D YK, BRYSON, and STOLL , Circuit Judges.
D YK, Circuit Judge.
Durr Systems, Inc. (“Durr”) sued EFC Systems, Inc.
(“EFC”) alleging infringement of claims of U.S. Patent
Nos. 6,189,804 (“’804 patent”), 6,360,962 (“’962 patent”),
7,017,835 (“’835 patent”), 8,141,797 (“’797 patent”), and
8,590,813 (“’813 patent”). The district court granted
EFC’s motion to exclude the testimony of Durr’s expert,
Vincent Dattilo, and its motion for summary judgment of
noninfringement. Durr appeals.
We conclude that the district court erred in construing
“generally conical/substantially conical” to exclude any
curves or undulations and erred in construing “rear cover
attached to the bell cup” to require that the rear cover and
bell cup be formed from separate pieces. However, we
determine that the district court did not abuse its discre-
tion in excluding the testimony of Durr’s expert. Accord-
ingly, we affirm the district court’s ruling excluding
Mr. Dattilo’s testimony, reverse its order granting sum-
mary judgment of noninfringement, and remand for
further proceedings.
BACKGROUND
Durr’s patents, which share the same specification,
are directed toward rotary atomizers for particulate
paints. According to the specification, many rotary atom-
izers “are unable to obtain good color matching” for par-
ticulate paint because “[w]hen [] paint is applied . . .
particles are oriented generally perpendicular to the
application surface” and “the paint has a different tint or
color than intended, i.e. with the . . . particles lying flat.”
’804 patent, col. 1 ll. 32–39. Durr’s rotary atomizer in-
cludes a bell cup with features that encourage laminar
(nonturbulent) flow and thus produce uniform paint
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 3
droplets that lie flat on the surface. One such feature of
the patented atomizer is the bell cup’s “generally conical
overflow surface.” Id. col. 1 ll. 57–62. The bell cup is also
“made hollow in order to reduce [its] weight” through a
“rear cover [] secured to the rear of the bell cup body,
enclosing an annular cavity.” Id. col. 2 ll. 6–8. Durr’s
invention improves color matching for particulate paints
by achieving “a more uniformed paint droplet size, which
in turn facilities control of the particulates in order to
assure proper orientation.” Id. col. 1 ll. 51–56.
Claim 1 of the ’804 patent, which is representative of
the asserted claims covering a rotary atomizer bell cup,
recites:
A rotary atomizer bell cup for atomizing particu-
late material including paint having a generally
conical overflow surface between a radially inward
central axial opening and a radially outward at-
omizing edge, the generally conical overflow sur-
face having a generally constant flow angle
relative to the atomizing edge and a deflector hav-
ing a deflection surface of generally rotational
symmetry disposed in front of said central open-
ing having a generally constant angle relative to
the axis from at least one inlet to a radial outer
edge.
’804 patent, claim 1 (emphasis added). Some of the as-
serted claims substitute the phrase “substantially conical”
for “generally conical.” See, e.g., ’797 patent, claim 8.
Several claims also require a hollow rear cover, and
other claims require a hollow rear cover without requiring
a generally or substantially conical surface. Claim 8 of
the ’797 patent, which is representative of the rear cover
claims, recites:
A rotary atomizer used to atomize a metallic
based particulate paint comprising:
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 4
a bell cup, including:
a central flat portion leading to a
substantially conical overflow sur-
face providing a color matching
flow at a spray edge, the spray
edge having a diameter; the par-
ticulate paint delivered to the bell
cup through a central axial open-
ing, wherein the substantially con-
ical overflow surface extends from
the central flat portion substan-
tially to the spray edge; and
a deflector having a diameter ap-
proximately one third the diame-
ter of the spray edge; the deflector
including a rear surface parallel to
the central flat portion and a gen-
erally conical surface substantially
parallel to the overflow surface of
the bell cup; and
a rear cover attached to the bell cup such
that the atomizer is hollow, the rear cover
cooperating with the bell cup to form an
annular cavity, the annular cavity extend-
ing about a perimeter of the bell cup;
wherein the rear cover extends from the
bell cup to a hub such that the rear cover
is substantially frustoconical from the bell
cup to the hub.
’797 patent, claim 8 (emphasis added).1
1 Other asserted claims use the language “bell cup
further having attached [thereto] a rear cover.” J.A. 77.
We refer throughout this opinion to the language in
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 5
EFC manufactures and sells a bell cup that is useable
in Durr’s rotary atomizers. EFC’s bell cup’s overflow
surface is slightly curved and its rear cover is not made
from a separate piece than the bell cup itself. On Au-
gust 22, 2018, Durr sued EFC for infringement of claims
of the ’804, ’962, ’835, ’797, and ’813 patents. EFC
brought counterclaims seeking declaratory judgments of
noninfringement and invalidity.
At a claim construction hearing, the parties disputed
the meaning of the claim terms “conical,” “general-
ly/substantially conical,” and “rear cover attached to the
bell cup.” J.A. 2288–89.2 As to a “conical” surface, Durr
proposed that the term be given its “[p]lain and ordinary
meaning—to the extent ordinary meaning needs to be
explained, ‘resembling a cone in shape.’” J.A. 64. EFC
argued a “conical” surface is “[a] surface that consists of a
cone shape, i.e., a surface which tapers, with a constant
slope, from a circle towards a point.” Id. The district
court agreed with Durr and construed “conical” to have its
plain and ordering meaning, noting that “it is readily
apparent, even to a layperson, that the plain and ordinary
meaning of conical is ‘resembling a cone in shape.’”
J.A. 64–65.
As to a “generally/substantially conical” surface, Durr
proposed the terms be given their “[p]lain and ordinary
meaning,” or to the extent their ordinary meaning needed
to be explained, “mostly conical.” J.A. 66. EFC proposed
construing a “generally/substantially conical” surface to
mean “[a] surface that consists of one or more conical
claim 8 of the ’797 patent (“rear cover attached to the bell
cup”) because that claim is representative of the attached
rear cover claims.
2 Citations to the J.A. refer to the Joint Appendix
submitted by the parties at Dkt. No. 29.
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 6
portions but without undulations or curved portions (e.g.,
a surface consisting of portions of two cones).” Id.
The district court adopted EFC’s construction. The
district court agreed that a “generally/substantially
conical” surface precludes undulations or curved portions.
The district court found support for its construction in a
preferred embodiment in the specification and the prose-
cution history that distinguished the ’797 patent over U.S.
Patent No. 4,838,487 (“Schneider”).
As to a “rear cover attached to the bell cup,” Durr
proposed that the term be given its plain and ordinary
meaning and EFC proposed that the term be construed as
“[b]ell cup and rear cover being separate pieces that have
been brought together and secured to one another.”
J.A. 77. The district court adopted EFC’s construction.
With respect to claim 8 of the ’797 patent, the district
court determined that this claim’s structure and language
indicated that the bell cup and rear cover were two sepa-
rate pieces because the claim uses the word “including” to
describe pieces integral to the bell cup in one limitation
and then, in a separate limitation, uses the word “at-
tached” to describe the rear cover. The district court also
found support for its construction in dependent claims
from the ’813 patent which add limitations specifying how
the rear cover is attached to the bell cup and suggesting
that the rear cover and bell cup are formed by two sepa-
rate pieces, such as dependent claim 7 which recites “the
rear cover is welded to the bell cup.” J.A. 78. Finally, the
district court determined that the specification supported
its conclusion because “the rear cover is consistently
described as a separate piece that is secured to the bell
cup.” J.A. 79.
Durr moved to clarify that the district court’s con-
struction of “generally/substantially conical” does not
exclude surfaces with inconsequential variations or
curves. The district court declined to “read ‘inconsequen-
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 7
tial’ curvature or variation into this claim construction”
and noted that, in any case, “it is unclear what would
constitute ‘inconsequential’ curvature or variation.”
J.A. 88.
Following claim construction, EFC moved to exclude
the testimony of Durr’s expert, Mr. Dattilo. In analyzing
EFC’s motion, the district court first defined a person of
ordinary skill in the art (“POSA”) as “someone with a
strong technical education that need not include a mas-
ter’s degree and with extensive experience in atomization
and the fluid dynamics of rotary atomizers, including
specific experience in the design of such atomizers.”
J.A. 13–14. It also clarified that “[i]f the person has a
master’s degree in engineering, fewer years of experience
shall be required.” J.A. 14. Based on this definition, the
district court granted EFC’s motion to exclude
Mr. Dattilo’s testimony as to infringement because “a
qualified expert must have technical experience and
knowledge about the design of [an atomizer’s] features”
and he “lack[ed] such technical experience and
knowledge.” J.A. 15. The district court determined
Mr. Dattilo could not provide testimony on doctrine-of-
equivalents infringement for the same reasons. In the
alternative, the district court noted that Mr. Dattilo’s
opinions as to doctrine-of-equivalents infringement must
be excluded because “he [did] not conduct his analysis ‘on
a limitation-by-limitation basis’ as required by the Feder-
al Circuit.” J.A. 17.
The parties also filed cross motions for summary
judgment. The district court granted EFC’s motion for
summary judgment of noninfringement because it found
no genuine dispute of material fact that EFC’s bell cup is
not “generally/substantially conical” because its overflow
surface is slightly curved and that EFC’s rear cover is not
“attached” to the bell cup because it is not formed from
separate pieces.
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 8
Durr timely appeals. We have jurisdiction under
28 U.S.C. § 1295(a)(1).
D ISCUSSION
I
Durr first argues the district court erred in construing
“generally/substantial conical” and “rear cover attached to
the bell cup.” We review a district court’s claim construc-
tion based on intrinsic evidence de novo and any underly-
ing factual findings based on extrinsic evidence for clear
error. Apple Inc. v. Wi-LAN Inc., 25 F.4th 960, 967
(Fed. Cir. 2022).
A
Durr argues that the district court’s construction of a
“generally/substantially conical” surface as a “surface that
consists of one or more conical portions but without undu-
lations or curved portions (e.g., a surface consisting of
portions of two cones, etc.)” is contrary to the plain mean-
ing of the claims. We agree.
“[W]ords of approximation, such as ‘generally’ and
‘substantially,’ are descriptive terms commonly used in
patent claims to avoid a strict numerical boundary to the
specified parameter.” Anchor Wall Sys., Inc. v. Rockwood
Retaining Walls, Inc., 340 F.3d 1298, 1310–11 (Fed. Cir.
2003) (internal quotation marks and citations omitted);
see also Aventis Pharms. Inc. v. Amino Chems. Ltd.,
715 F.3d 1363, 1377 (Fed. Cir. 2013) (“[T]his court has
interpreted ‘substantially’ as a non-specific term of ap-
proximation that avoids a numerical boundary.”); Liquid
Dynamics Corp. v. Vaughan Co., 355 F.3d 1361, 1368
(Fed. Cir. 2004) (“The term ‘substantial’ is a meaningful
modifier implying ‘approximate,’ rather than ‘perfect.’”);
Playtex Prods., Inc. v. Procter & Gamble Co., 400 F.3d
901, 907 (Fed. Cir. 2005). In the context of the claims
here, we conclude that the plain meaning of a “general-
ly/substantially conical” surface allows some deviation
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 9
from “conical,” and could include undulations or curved
portions.
The specification is not inconsistent with this con-
struction. The district court cited one preferred embodi-
ment in the specification in support of its construction
describing “a generally conical rear surface 144 which
extends to a generally rounded central rear surface 142[.]”
J.A. 68. It additionally pointed to Figure 5, reproduced
below, depicting this embodiment, where “it is clear that
the ‘rounded central rear surface[,]’ #142, is curved, while
the ‘generally conical rear surface’ is not.” J.A. 69.
J.A. 110. Putting aside the fact that the preferred embod-
iment cited by the district court refers to the deflector
[110], not the overflow surface [126], this embodiment
does not suggest that the term “generally conical” pre-
cludes all curves, only that a “generally rounded” surface
is not “generally conical.” See ’804 patent, col. 4, ll. 4–11.
Similarly, the prosecution history (in which the patent
applicant distinguished Schneider) only shows that
Schneider’s dramatic undulating overflow surface is not
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 10
“substantially conical.” Schneider, pictured below, dis-
closes a bell cup with an overflow surface [24.1 and 24.2]
that curves, forming what Durr calls a “sharp lip” [24.2],
towards the spray edge [60]. Pet’r’s Br. 43.
J.A. 3235. During prosecution of the ’797 patent, the
patent applicant distinguished the invention over Schnei-
der by contrasting the claimed “substantially conical
overflow surface extending from the central flat portion to
the spray edge” to Schneider’s overflow surface, where the
substantially conical portion “does not ‘extend . . . to the
spray edge.’” J.A. 2588. The patent applicant added that
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 11
“the insertion of ‘substantially’ prior to ‘conical’ does not
so broaden ‘conical’ to read upon [Schneider’s] undulating
surface.” J.A. 2589. While this prosecution history clear-
ly shows that “generally/substantially conical” cannot
capture the curve disclosed in Schneider, it does not
preclude the claim language from capturing some surface
deviations. A jury trial is required under the correct
construction to determine if EFC’s bell cup infringes the
asserted claims.
B
Durr also argues that the district court erred by not
giving “attached” its plain and ordinary meaning, which
does not require that the rear cover and bell cup be
formed from separate pieces. We agree. This is not a
product-by-process claim. As such, the meaning of “at-
tached” is agnostic to the method or procedure of attach-
ment. The plain meaning of “attached” is broad enough to
encompass both two pieces that are secured together or
two pieces that are proximate to each other although
formed from a single piece at the outset. See Webster’s
Third New Int’l Dictionary 140 (2002) (defining “at-
tach[ed]” as “join[ed,]” “fix[ed] or fasten[ed,]” or “con-
nect[ed]”); Attached, Merriam-Webster.com Dictionary,
https://www.merriam-webster.com/dictionary/attached
(last visited Mar. 6, 2026) (defining “attached” as “con-
nected or joined to something”); 1 Oxford English Diction-
ary 759 (2d. ed. 1989) (defining “attached” as both
“[t]acked on, fastened by a material union” and “[j]oined
functionally”).
Nothing in the dependent claims or specification lim-
its “attached” to only securing two separate pieces togeth-
er. That the dependent claims require a rear cover and
bell cup that start as two separate pieces and are secured
together does not impose any such requirement on the
independent claims. See Phillips v. AWH Corp., 415 F.3d
1303, 1314–15 (Fed. Cir. 2005) (en banc). Similarly, the
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 12
fact that the only example in the specification involves
joining two pieces does not limit the claims. See SciMed
Life Sys., Inc. v. Advanced Cardiovascular Sys., Inc.,
242 F.3d 1337, 1340 (Fed. Cir. 2001). This is particularly
true here where nothing in the nature of the invention
suggests joining two pieces together is necessary to
achieve the desired result.
II
Durr argues the district court abused its discretion by
excluding Mr. Dattilo’s testimony based on an improper
definition of a POSA. We review the district court’s
decision to exclude an expert witness for abuse of discre-
tion. See Trudell Med. Int’l Inc. v. D R Burton Healthcare,
LLC, 127 F.4th 1340, 1347 (Fed. Cir. 2025) (applying
Fourth Circuit law). The level of ordinary skill in the art
is a question of fact reviewed for clear error. ALZA Corp.
v. Andrx Pharms., LLC, 603 F.3d 935, 940 (Fed. Cir.
2010).
“To offer expert testimony from the perspective of a
skilled artisan in a patent case—like for claim construc-
tion, validity, or infringement—a witness must at least
have ordinary skill in the art. Without that skill, the
witness’ opinions are neither relevant nor reliable.”
Kyocera Senco Indus. Tools Inc. v. Int’l Trade Comm’n,
22 F.4th 1369, 1376–77 (Fed. Cir. 2022). “This is true
regardless of whether the witness is being offered to
testify on literal infringement, doctrine-of-equivalents
infringement, or both. . . . The absence of relevant
knowledge and the risk for abuse apply equally to both
situations.” Id. at 1377.
Before the district court, the parties disputed the rel-
evant art and, as a result, the definition of a POSA. Durr
argued that the relevant art is paint and color matching,
and that a POSA is a technical or business professional
with 10–15 years of experience in “‘automotive or indus-
trial painting systems’ and knowledge of ‘industrial
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 13
robots, fluid dynamics, paint chemistry, automated . . .
painting and manufacturing processes and management,’
and ‘painted surface . . . quality and control.’” J.A. 9
(alterations in original). EFC argued that the relevant
art is rotary atomizer design and that a POSA is “some-
one with at least a master’s degree in mechanical engi-
neering and five years of experience in ‘atomization and
fluid dynamics of rotary atomizers,’ including specific
experience in designing rotary atomizers.” J.A. 9.
In considering the definition of a POSA, the district
court identified six relevant factors from Best Med. Int’l,
Inc. v. Elekta Inc., 46 F.4th 1346 (Fed. Cir. 2022): “(1) the
educational level of the inventor; (2) type of problems
encountered in the art; (3) prior art solutions to those
problems; (4) rapidity with which innovations are made;
(5) sophistication of the technology; and (6) educational
level of active workers in the field.” J.A. 9 (quoting Best
Med., 46 F.4th at 1353). The first three factors are prin-
cipally applicable in defining a POSA in this case. In a
broad sense, the problem concerned the difficulty of
causing paint droplets to lie flat on a surface. But the
immediate problem—and the concern of the patents—was
with the functioning of the atomizer, and the solution lay
not in altering the nature of the paint but in altering the
design of the atomizer.
The specification states that in “known atomizer bell
cups, the paint follows a tortuous, turbulent path from the
nozzle to the atomizing edge” and, as a result, “paint from
the atomizer is atomized to a wide variety of paint droplet
sizes.” ’804 patent, col. 1 ll. 26–34. The invention solves
these problems through a rotary atomizer with “several
inventive features” including “a generically conical over-
flow surface having a generally constant flow angle be-
tween a deflector and the atomizing edge,” an increased
exposed surface area, and an increased diameter of the
atomizing edge. Id. col. 1 l. 57–col. 2 l. 2. The rotary
atomizer’s design solves these problems, as “[t]he bell cup
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 14
is designed to reduce flow deviations of the paint as it
travels from the axial opening to the spray edge in order
to provide laminar flow of the paint across the overflow
surface and the atomizing edge.” Id., col. 2 ll. 2–5. More-
over, some asserted claims are not limited to the applica-
tion of paint as they explicitly recite the application of any
“particulate material.” See ’804 patent, claim 1.
The district court did not err in concluding that the
relevant art “involves atomization and fluid dynamics
rather than paint and color match,” J.A. 11. Given that
Mr. Dattilo admittedly has no experience designing rotary
atomizers, the district court did not err in excluding his
testimony.
Durr argues that one of the inventors, Robert Heldt,
would not meet the district court’s definition of a POSA
because he has no expertise in fluid dynamics, but
Mr. Heldt’s qualifications “[are] not determinative.”
Custom Accessories, Inc. v. Jeffrey-Allan Indus., Inc.,
807 F.2d 955, 962 (Fed. Cir. 1986). The asserted patents
list multiple named inventors, as to three of which the
record contains no evidence about their level of skill.
Durr has not shown that these inventors lacked design
qualifications, and given the nature of the invention, it
seems almost certain that they were skilled in design.
Mr. Heldt’s limited qualifications do not compel us to
conclude that the district court erred in determining the
relevant art was rotary atomizer design.
Durr does not dispute that Mr. Dattilo does not meet
the district court’s definition of a POSA. Because we
conclude the district court did not err in its definition of a
POSA, we conclude that the district court did not abuse
its discretion by excluding Mr. Dattilo’s testimony. We
accordingly need not reach Durr’s arguments as to wheth-
er Mr. Dattilo’s doctrine-of-equivalents infringement
analysis should also be excluded because it was not con-
ducted on a limitation-by-limitation basis.
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DURR SYSTEMS, INC. v. EFC SYSTEMS, INC. 15
CONCLUSION
We conclude that the district court erred in construing
a “generally/substantially conical” surface to mean a
“surface that consists of one or more conical portions but
without undulations or curved portions (e.g., a surface
consisting of portions of two cones, etc.).” We also con-
clude that the district court erred in construing a “rear
cover attached to the bell cup” to require that the rear
cover and bell cup are two different pieces secured togeth-
er. With respect to the expert testimony, we do not think
the district court clearly erred in defining a POSA or
abused its discretion in excluding Mr. Dattilo’s testimony.
We accordingly affirm-in-part, reverse-in-part, and re-
mand for further proceedings consistent with this opinion.
AFFIRMED-IN-PART, REVERSED-IN-PART, AND
REMANDED
COSTS
No costs.
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