Court Opinion

ID: 9353615
Source: CourtListenerOpinion
Date Created: 2023-01-12 14:01:26.873502+00
Date Added: 2024-06-11T17:09:51.510434
License: Public Domain

Case: 21-2370    Document: 55     Page: 1   Filed: 01/12/2023

   United States Court of Appeals
       for the Federal Circuit
                  ______________________

      GRACE INSTRUMENT INDUSTRIES, LLC,
                Plaintiff-Appellant

                             v.

    CHANDLER INSTRUMENTS COMPANY, LLC,
               AMETEK, INC.,
              Defendants-Appellees
            ______________________

                        2021-2370
                  ______________________

    Appeal from the United States District Court for the
 Southern District of Texas in No. 4:20-cv-01749, Judge An-
 drew S. Hanen.
                  ______________________

                Decided: January 12, 2023
                 ______________________

     BRADFORD TURNER LANEY, Raley & Bowick, LLP, Hou-
 ston, TX, argued for plaintiff-appellant. Also represented
 by ROBERT MCGEE BOWICK, JR.

     JULIE S. GOLDEMBERG, Morgan, Lewis & Bockius LLP,
 Philadelphia, PA, argued for defendants-appellees. Also
 represented by EUGENE HWANGBO, JASON C. WHITE, Chi-
 cago, IL; ARCHIS VASANT OZARKAR, WILLIAM R. PETERSON,
 MELISSA MARIE STORY, Houston, TX.
                  ______________________
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 2                        GRACE INSTRUMENT INDUSTRIES, LLC v.
                         CHANDLER INSTRUMENTS COMPANY, LLC

     Before CHEN, CUNNINGHAM, and STARK, Circuit Judges.
 CHEN, Circuit Judge.
      Grace Instrument Industries, LLC (Grace) appeals a
 claim construction order issued by the United States Dis-
 trict Court for the Southern District of Texas finding the
 term “enlarged chamber” indefinite and construing the
 term “means for driving said rotor to rotate located in at
 least one bottom section.” As a result of the district court’s
 order, the parties stipulated that asserted claims 1, 2, 4, 5,
 7–9, 11, 14, 15, and 17 of U.S. Patent No. 7,412,877
 (’877 patent) are invalid and that claims 4, 5, 7–9, 11, 14,
 15, and 17 are not infringed, and the court entered final
 judgment in favor of Chandler Instruments Company, LLC
 (Chandler). Because the district court erred in its analysis
 of the term “enlarged chamber,” we vacate the district
 court’s determination that “enlarged chamber” is indefinite
 and remand for further proceedings consistent with this
 opinion. We affirm the district court’s construction of
 “means for driving said rotor to rotate located in at least
 one bottom section.”
                         BACKGROUND
                                I
      When drilling oil wells, drilling fluid is used to drive a
 drill bit and bring drill cuttings back to the surface of the
 well. ’877 patent col. 1 ll. 17–19. The drilling fluid’s vis-
 cosity is critical to the well’s operation—too high and the
 fluid is too hard to pump; too low and the fluid cannot carry
 the drill cuttings back to the surface. Id. at col. 1 ll. 19–24.
 Thus, before use, drilling fluid viscosity is first measured
 using a viscometer that simulates “down-hole” conditions—
 i.e., the temperature and pressure at the drill bit while
 drilling. Id. at col. 1 ll. 26–28.
     In a liquid pressurized viscometer, pressurization fluid
 is added to pressurize the sample drilling fluid within the
 viscometer to down-hole conditions while the sample fluid
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 is stirred by a rotor to measure its viscosity. The introduc-
 tion of the pressurization fluid compresses the sample drill-
 ing fluid, causing it to take up less volume within the
 viscometer. Ideally, the pressurization fluid does not mix
 with the sample fluid being measured to ensure that the
 viscometer reports the viscosity of only the sample fluid
 and not the viscosity of a mixture of the two fluids. Id. at
 col. 1 ll. 53–56, col 5 ll. 55–57, col. 5 ll. 59–62, col. 12
 ll. 21–23.
      Before the ’877 patent, liquid pressurized viscometers
 separated the sample fluid from the pressurization fluid in
 one of two ways. Some viscometers relied on the density
 difference between the fluids, but if some pressurization
 fluid entered the chamber where the sample fluid was be-
 ing tested, stirring by the rotor would cause the two fluids
 to mix, leading to measurement errors. Id. at col. 1
 ll. 53–56, col. 5 ll. 59–62. Other viscometers used a seal to
 separate the two fluids, but friction caused by the sample
 fluid rubbing against the seal as the sample fluid was
 stirred led to inaccurate results. Id. at col. 1 ll. 43–46, col. 5
 ll. 57–59.
      The ’877 patent’s viscometer purportedly eliminates
 measurement errors caused by seal friction or commingling
 of sample and pressurization fluids by offering a different
 solution. Id. at col. 2 ll. 1–3, col. 12 ll. 21–23. Instead of
 using a seal to separate the fluids, the ’877 patent’s viscom-
 eter includes an “enlarged” chamber located between a
 lower chamber, housing the sample fluid, and a pressuri-
 zation fluid inlet, located in the top section of the viscome-
 ter’s pressure vessel. This enlarged chamber is large
 enough such that the level of the sample fluid, which before
 pressurization initially fills both the lower chamber and
 the enlarged chamber, never falls below the transition
 point between the lower chamber and enlarged chamber
 when the application of the pressurization fluid compresses
 the sample fluid. By keeping the sample fluid level above
 the top of the lower chamber and within the enlarged
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                         CHANDLER INSTRUMENTS COMPANY, LLC

 chamber, even when the sample fluid is compressed, the
 claimed viscometer design ensures that any mixing be-
 tween the two fluids occurs within the enlarged chamber
 and no pressurization fluid enters the lower chamber
 where the sample fluid is being tested. Id. at col. 5 l. 55 –
 col. 6 l. 6; see also id. at col. 8 ll. 37–48, col. 10 ll. 49–60.
 Thus, the ’877 patent’s design is intended to “[t]otally elim-
 inate the measurement error because of sample mixing
 with pressurization fluid in a comparative viscometer.” Id.
 at col. 12 ll. 21–23.
    The ’877 patent discloses three embodiments of its vis-
 cometer. The first embodiment is shown below.

 Id. FIG. 1 (exploding out chambers 45 and 49); see also id.
 FIG. 2, FIG. 3. In each embodiment, chambers 45 and 49
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 act together to contain the pressurization fluid as the sam-
 ple fluid in a “lower measurement zone” is compressed:
     [W]hen pressurization fluid is applied, the sample
     fluid level is pushed down due to the compressibil-
     ity of tested sample. Thus initial sample fluid in-
     side of chamber 45 goes down to chamber 49
     through small gap 25, and some of the initial sam-
     ple fluid inside of chamber 49 goes down to the
     lower measurement zone through small gap 27.
     However, chamber 45 and chamber 49 are large
     enough so that at maximum rated pressure, cham-
     ber 49 is still at least half filled with sample fluid.
     This ensures the accuracy of the measurement be-
     cause measurement zone below anti mixer bottom
     fin 82 is always totally filled with sample fluid.
 Id. at col. 5 l. 63 – col. 6 l. 6; see also id. at col. 8 ll. 37–48,
 col. 10 ll. 49–60. Although the three embodiments use both
 chamber 45 and chamber 49, the ’877 patent also explains
 that “[i]t is not necessary to have both chamber 45 and
 chamber 49.” Id. at col. 10 ll. 64–65. “With just cham-
 ber 45 or chamber 49 and sufficient volume, pressuriza-
 tion fluid and test sample can still be separated well.” Id.
 at col. 10 ll. 65–67 (emphasis added).
      To measure the viscosity of the sample fluid in the
 lower measurement zone, the ’877 patent discloses a rotor
 that is driven by magnetic coupling but also “could be
 driven to rotate with any means such as directly driven at
 the bottom of the cell body with dynamic seal, etc.” Id. at
 col. 2 ll. 11–13, col. 4 ll. 54–59, col. 5 ll. 42–54, col. 7
 ll. 41–47, col. 8 ll. 24–36, col. 9 ll. 61–67, col. 10 ll. 36–48,
 col. 11 ll. 41–43.
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 6                      GRACE INSTRUMENT INDUSTRIES, LLC v.
                       CHANDLER INSTRUMENTS COMPANY, LLC

     Claims 1 and 4 are independent claims that claim a
 pressurized device and a viscometer, respectively:
     1. A pressurized device comprising:
        (a) a pressure vessel within which is verti-
        cally disposed at least one top section filled
        with a pressurization fluid of a first density
        and at least one lower section filled with a
        test sample of a second density,
        (b) an enlarged chamber with reduced
        openings positioned between the at least
        one top section and the at least one bottom
        section for communicating pressure with
        said top section and said lower section
        within said pressure vessel,
        (c) whereby said pressurization fluid would
        not mix with said test sample because of
        the nature of their density difference.
     4. Viscometer comprising:
        (a) a pressure vessel within which at least
        one top section filled with a pressurization
        fluid of a first density,
        (b) within said pressure vessel a rotor
        which is driven to rotate while contacting
        with a sample liquid of a second density to
        be measured,
        (c) means for driving said rotor to rotate lo-
        cated in at least one bottom section,
        (d) a bob within said rotor,
        (e) an enlarged chamber with reduced
        openings positioned between the at least
        one top section and the at least one bottom
        section for communicating pressure located
        above said bob,
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         (f) whereby said pressurization fluid would
         not mix with said sample liquid because of
         the nature of their density difference.
 Id. at col. 12 ll. 34–47, col. 12 ll. 52–67 (emphases added).
 The two italicized claim terms are the focus of this appeal.
                               II
     On May 19, 2020, Grace sued Chandler in the United
 States District Court for the Southern District of Texas, al-
 leging that Chandler’s Model 7600 viscometer infringed
 multiple claims of the ’877 patent. J.A. 52; J.A. 61–65. On
 July 1, 2021, the district court issued its claim construction
 order. Grace Instrument Indus., LLC v. Chandler Instru-
 ments Co., No. 4:20-cv-1749, 2021 WL 2711987 (S.D. Tex.
 July 1, 2021) (Claim Construction Order).
     Relevant here, the district court held that the term “en-
 larged chamber” in claims 1 and 4 is indefinite. Id. at *4–5.
 The district court explained that “enlarged” is a “term of
 degree” that “necessarily calls for some comparison against
 some baseline.” Id. at *5 (quoting Liberty Ammunition,
 Inc. v. United States, 835 F.3d 1388, 1395 (Fed. Cir. 2016)).
 Finding that the ’877 patent “does not provide the requisite
 objective boundaries” for a skilled artisan, the district court
 held that “enlarged chamber” is indefinite. Id. at *5. The
 district court rejected Grace’s argument that “enlarged
 chamber” could be defined by its purpose, finding that “ex-
 plaining that something is large enough to do a certain task
 does not answer the question: larger than what?” Id. The
 district court further disagreed with Grace that the base-
 line for “enlarged” is the prior art, explaining that “this is
 not evident from the ’877 Patent itself.” Id.
     The district court also construed “means for driving
 said rotor to rotate located in at least one bottom section.”
 Id. at *7–8. The parties agreed that the term was subject
 to 35 U.S.C. § 112, ¶ 6 (pre-AIA), and the table below illus-
 trates the parties’ positions on the construction:
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 8                       GRACE INSTRUMENT INDUSTRIES, LLC v.
                        CHANDLER INSTRUMENTS COMPANY, LLC

 Id. at *7; J.A. 34. The parties thus agreed that the function
 is “driving said rotor to rotate,” but they disputed the
 means and whether the phrase “located in at least one bot-
 tom section” modifies “rotor,” as Grace contended, or
 “means for driving,” as Chandler argued. Claim Construc-
 tion Order, 2021 WL 2711987, at *7.
     To resolve the dispute, the district court looked to
 claim 14, which depends from claim 4 and recites:
     14. The viscometer of claim 4 wherein said means
     for driving said rotor to rotate is a magnetic cou-
     pling across said pressure vessel wall.
 ’877 patent col. 13 ll. 22–24. The district court found that
 Grace’s proposed construction of the means (1) was “not
 broad enough to include magnetic coupling” as it must be-
 cause of dependent claim 14 and (2) would exclude other
 terms described in the patent as causing the rotor to rotate.
 Claim Construction Order, 2021 WL 2711987, at *7 (citing
 ’877 patent col. 5 ll. 45–47 (magnet mount), col. 4 ll. 55–59
 (gear box, motor, driving magnet, or coupling magnet),
 col. 12 ll. 41–43 (direct drive at bottom of the cell body)).
 Thus, the district court adopted Chandler’s proposed con-
 struction of the means.
     The district court also agreed with Chandler that “lo-
 cated in at least one bottom section” modifies “means for
 driving,” not “rotor.” Id. at *8. The district court explained
 that this interpretation “conform[s] with [the] usual rules
 of grammar and sentence structure” and is confirmed by
 limitation 4(b), which already describes the rotor’s location
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 as “within said pressure vessel,” not necessarily in the “bot-
 tom section.” Id.
     Thus, the district court adopted in its entirety Chan-
 dler’s proposed construction of “means for driving said ro-
 tor to rotate located in at least one bottom section.” Id.
 Accordingly, the function of the “means for driving” limita-
 tion is “driving said rotor to rotate, where the means for
 driving is located in at least one bottom section,” and the
 corresponding structure is “(i) magnetic coupling (magnetic
 mount, gear box or motor, driving magnet, coupling mag-
 net), or (ii) direct drive at bottom of cell body, and known
 equivalents.” Id. at *7–8.
     The parties then stipulated that claims 1, 2, 4, 5, 7–9,
 11, 14, 15, and 17 are invalid based on the district court’s
 determination that “enlarged chamber” is indefinite, and
 that claims 4, 5, 7–9, 11, 14, 15, and 17 are not infringed
 based on the district court’s construction of “means for driv-
 ing said rotor to rotate in at least one bottom section.”
 J.A. 1529–34. The district court entered a final judgment
 on September 23, 2021. J.A. 19–20.
    Grace timely appealed. We have jurisdiction under 28
 U.S.C. §§ 1291 and 1295(a)(1).
                         DISCUSSION
      Claim construction requires determining how a skilled
 artisan would understand a claim term “in the context of
 the entire patent, including the specification.” Phillips v.
 AWH Corp., 415 F.3d 1303, 1313 (Fed. Cir. 2005) (en banc).
 We begin by considering the language of the claims them-
 selves. Id. at 1314. However, “claims must be read in view
 of the specification, of which they are a part.” Id. at 1315
 (internal quotation marks omitted) (quoting Markman v.
 Westview Instruments, Inc., 52 F.3d 967, 978 (Fed. Cir.
 1995) (en banc)). We have explained that the specification
 is the “single best guide to the meaning of a disputed term,”
 Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582
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 (Fed. Cir. 1996), and “is, thus, the primary basis for con-
 struing the claims,” Phillips, 415 F.3d at 1315 (citation and
 internal quotation marks omitted). A court also should
 consider the patent’s prosecution history, and may rely on
 dictionary definitions, “so long as the dictionary definition
 does not contradict any definition found in or ascertained
 by a reading of the patent documents.” Id. at 1317,
 1322–23 (citation and internal quotation marks omitted).
      We review claim construction based on intrinsic evi-
 dence de novo and review any findings of fact regarding ex-
 trinsic evidence for clear error. SpeedTrack, Inc. v.
 Amazon.com, Inc., 998 F.3d 1373, 1378 (Fed. Cir. 2021) (cit-
 ing Teva Pharms. USA, Inc. v. Sandoz, Inc., 574 U.S. 318,
 331–32 (2015)). Intrinsic evidence includes the patent’s
 claims, specification, and prosecution history. Cont’l Cirs.
 LLC v. Intel Corp., 915 F.3d 788, 795 (Fed. Cir. 2019). Ex-
 trinsic evidence is “secondary to the intrinsic evidence” and
 “consists of all evidence external to the patent and prose-
 cution history, including expert and inventor testimony,
 dictionaries, and learned treatises.” Id. at 799 (quoting
 Phillips, 415 F.3d at 1317). “If the meaning of a claim term
 is clear from the intrinsic evidence, there is no reason to
 resort to extrinsic evidence.” Seabed Geosolutions (US) Inc.
 v. Magseis FF LLC, 8 F.4th 1285, 1287 (Fed. Cir. 2021).
      A “patent is invalid for indefiniteness if its claims, read
 in light of the specification delineating the patent, and the
 prosecution history, fail to inform, with reasonable cer-
 tainty, those skilled in the art about the scope of the inven-
 tion.” Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S.
 898, 901 (2014). “The ultimate conclusion that a claim is
 indefinite under 35 U.S.C. § 112, ¶ 2 is a legal conclusion,
 which we review de novo.” Cox Commc’ns, Inc. v. Sprint
 Commc’n Co., 838 F.3d 1224, 1228 (Fed. Cir. 2016) (citation
 omitted). “As in claim construction, we review a district
 court’s underlying factual determinations for clear error.”
 Id. (citations omitted). Moreover, “[a]ny fact critical to a
 holding on indefiniteness . . . must be proven by the
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 challenger by clear and convincing evidence.” Id. (altera-
 tion in original) (citation and internal quotation marks
 omitted).
                    I. Enlarged Chamber
     Grace argued before the district court that the term
 “enlarged chamber” should be construed as “the area be-
 tween reduced openings that is large enough to hold excess
 test sample (i.e., the type of fluid normally used in these
 machines) to prevent mixing of pressurization fluid and
 test sample below the bottom fin during elevated pressuri-
 zation.” Claim Construction Order, 2021 WL 2711987,
 at *5. The district court declined to adopt that construc-
 tion, concluding that the ’877 patent fails to disclose objec-
 tive boundaries for a skilled artisan to know what the
 claimed “enlarged chamber” must be larger than. Id. This
 was error. The intrinsic record informs a skilled artisan
 that the ’877 patent and its claims are directed to a viscom-
 eter with an “enlarged chamber” that is large enough to
 prevent pressurization fluid from entering the lower sec-
 tion of the pressure vessel—where the viscosity of the test
 sample is being measured—during elevated pressuriza-
 tion. In other words, the enlarged chamber has to be able
 to contain enough sample fluid at the pre-pressurization
 stage such that, during pressurization, the sample fluid
 level does not fall below the bottom of the enlarged cham-
 ber and into the viscometer’s lower, testing section. This
 design ensures that any mixing of the pressurization fluid
 and compressed sample fluid occurs within the enlarged
 chamber and not in the lower, testing section. Thus, in the
 context of this patent, “enlarged chamber” does not require
 that chamber to be larger than some baseline object; rather
 it must be large enough to accomplish a particular function.
    The ’877 patent’s specification guides us to the    term’s
 meaning. The specification explains that “[o]ne        of the
 drawbacks of most liquid pressurized viscometers       is the
 mixing between tested sample and pressurization        fluid,”
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 which leads to inaccurate test results. ’877 patent col. 5
 ll. 55–57, col. 5 ll. 59–62; see also id. at col. 1 ll. 53–56. Ac-
 cording to the patent, prior art viscometers attempted to
 remedy this inaccuracy by using a seal between the pres-
 surization fluid and sample fluid, but the seal “induce[s]
 friction error causing inaccurate measurement.” Id. at
 col. 5 ll. 57–59; see also id. at col. 1 ll. 43–46; discussion su-
 pra Background § I. The ’877 patent explains that the “cur-
 rent invention” solves this problem through use of
 chambers 45 and 49: “[C]hamber 45 and chamber 49 are
 large enough so that at maximum rated pressure, chamber
 49 is still at least half filled with sample fluid. This ensures
 the accuracy of the measurement because measurement zone
 below anti mixer bottom fin 82 is always totally filled with
 sample fluid.” ’877 patent col. 6 ll. 2–6 (emphases added).
 The patent discloses the same for two other embodiments,
 id. at col. 8 ll. 43–48, col. 10 ll. 55–60, and explains that a
 single chamber could be used instead of two chambers (i.e.,
 chamber 45 and chamber 49), provided the single chamber
 has “sufficient volume,” id. at col. 10 ll. 64–67. Finally, the
 specification explains that “[b]y providing an enlarged
 chamber such as chamber 45 or chamber 49 . . . this config-
 uration can be applied to other applications than viscome-
 ters to reduc[e] the mixing of test sample and
 pressurization fluid.” Id. at col. 11 ll. 28–32 (emphasis
 added). A skilled artisan would understand from these dis-
 closures that the “enlarged chamber” comprises cham-
 bers 45 and/or 49 and is large enough to prevent the
 pressurization fluid from mixing with the sample fluid in
 the lower measurement zone during elevated pressuriza-
 tion, thus avoiding measurement errors caused by commin-
 gling of the sample and pressurization fluids in prior-art
 viscometers.
     The prosecution history supports this understanding.
 In response to a rejection over U.S. Patent No. 4,633,708
 (Blommaert), which taught use of a seal, the applicant ex-
 plained “[b]y having ‘an enlarged chamber with reduced
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 openings for communicating pressure’, pressurization oil
 will not contaminate [the] test sample even without a seal
 as described in Blommaert.”            J.A. 1063; see also
 J.A. 1066–67, 1069–70. The applicant also explained that
 the “[c]urrent invention solved a long lasting problem” in
 high-pressure testing of drilling fluids, including “the large
 measurement error . . . induced due to the friction of the
 seal” in designs like Blommaert. J.A. 1062–63; see also
 J.A. 1064, 1066, 1068, 1070. The examiner subsequently
 allowed the claims. A skilled artisan would understand
 from the prosecution history that the purpose and role of
 the ’877 patent’s “enlarged chamber” is to prevent commin-
 gling of the sample and pressurization fluids in the lower
 measurement zone without using a seal, thereby avoiding
 the measurement errors seen in prior-art viscometers like
 Blommaert.
      Thus, although “enlarged chamber” is not a term of art,
 the intrinsic record sufficiently guides a skilled artisan to
 the meaning of that term as used in the ’877 patent. The
 district court erred in its reliance on extrinsic evidence—
 i.e., dictionary definitions—that contradict the scope and
 meaning of “enlarged chamber” that a skilled artisan
 would ascertain by reading the intrinsic record. See Phil-
 lips, 415 F.3d at 1322–23; see also id. at 1316 (“[O]ur cases
 recognize that the specification may reveal a special defini-
 tion given to a claim term by the patentee that differs from
 the meaning it would otherwise possess.”); Trs. of Colum-
 bia Univ. v. Symantec Corp., 811 F.3d 1359, 1363 (Fed. Cir.
 2016) (“The only meaning that matters in claim construc-
 tion is the meaning in the context of the patent.”). Where
 the specification instructs as to the meaning of a claim
 term, “the inventor’s lexicography governs.” Phillips, 415
 F.3d at 1316.
      Chandler, for its part, is correct that the ’877 patent’s
 specification refers to “enlarged chamber” only twice, but,
 for the reasons already stated, a skilled artisan would un-
 derstand that the specification’s descriptions of an
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 enlarged chamber and the corresponding embodiments ad-
 equately guide the skilled artisan to the meaning of “en-
 larged chamber.” Further, to the extent Chandler would
 require an explicit definition of the term “enlarged cham-
 ber,” that is incorrect. As our en banc opinion in Phillips
 explained, a “claim term may be clearly redefined without
 an explicit statement of redefinition,” and “[e]ven when
 guidance is not provided in explicit definitional format, the
 specification may define claim terms by implication such
 that the meaning may be found in or ascertained by a read-
 ing of the patent documents.” 415 F.3d at 1320–21 (first
 quoting Bell Atl. Network Servs., Inc. v. Covad Commc’ns
 Grp., Inc., 262 F.3d 1258, 1268 (Fed. Cir. 2001); and then
 quoting Irdeto Access, Inc. v. Echostar Satellite Corp., 383
 F.3d 1295, 1300 (Fed. Cir. 2004)); see also Aventis Pharma
 S.A. v. Hospira, Inc., 675 F.3d 1324, 1330 (Fed. Cir. 2012)
 (“This clear expression need not be in haec verba but may
 be inferred from clear limiting descriptions of the invention
 in the specification or prosecution history.”).
      The district court’s reliance on dictionary definitions of
 “enlarged” rather than the meaning a skilled artisan would
 reasonably understand from the intrinsic record led, in
 part, to its reliance on Liberty Ammunition. There, we
 found that “reduced area of contact” must be compared to
 the prior-art ammunition because there was no other ob-
 jective boundary for a skilled artisan. Liberty Ammunition,
 835 F.3d at 1396–97 (citing Interval Licensing LLC v. AOL,
 Inc., 766 F.3d 1364, 1370–71 (Fed. Cir. 2014)). Here, how-
 ever, the intrinsic record provides an objective boundary
 for a skilled artisan—i.e., the “enlarged chamber” must be
 large enough to prevent, during elevated pressurization,
 commingling of sample and pressurization fluids in the
 lower measurement zone. Unlike Liberty Ammunition,
 this objective boundary does not require a comparison to
 the size of prior-art chambers.
     Our decision in Biosig Instruments, Inc. v. Nautilus,
 Inc., 783 F.3d 1374 (Fed. Cir. 2015), is more applicable.
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 There, we reviewed claims directed to a heart rate monitor
 with a “spaced relationship” between a first live electrode
 and a first common electrode. Id. at 1376. We explained
 that, although the patent “does not specifically define
 ‘spaced relationship’ with actual parameters,” the intrinsic
 evidence demonstrated that a “skilled artisan would be
 able to determine this language requires the spaced rela-
 tionship to be neither infinitesimally small nor greater
 than the user’s hands”:
     For example, on the one hand, the distance be-
     tween the live electrode and the common electrode
     cannot be greater than the width of a user’s hands
     because claim 1 requires the live and common elec-
     trodes to independently detect electrical signals at
     two distinct points of a hand. On the other hand,
     it is not feasible that the distance between the live
     and common electrodes be infinitesimally small, ef-
     fectively merging the live and common electrodes
     into a single electrode with one detection point.
 Id. at 1382–83 (quoting Biosig Instruments, Inc. v. Nauti-
 lus, Inc., 715 F.3d 891, 899 (Fed. Cir. 2013), vacated sub
 nom. Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S.
 898 (2014)). Thus, we found that “a skilled artisan would
 understand the inherent parameters of the invention as
 provided in the intrinsic evidence.” Id. at 1384. The same
 is true here. A skilled artisan would understand the inher-
 ent parameters of the “enlarged chamber” through the in-
 trinsic evidence. Like the spaced relationship in Nautilus,
 the “enlarged chamber” must be a certain minimum size,
 or large enough, to maintain sample fluid within the en-
 larged chamber when the sample fluid is under elevated
 pressurization.
     Although we disagree with the district court’s conclu-
 sion that “enlarged chamber” must be larger than some-
 thing else rather than large enough to achieve a particular
 purpose, it appears that the indefiniteness question is not
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 yet fully resolved and may require further fact finding on
 remand. Chandler, for example, argues that the term “en-
 larged chamber” is still indefinite because the claims recite
 an additional limitation that relies on the “density differ-
 ence” between the fluids—not the enlarged chamber—to
 prevent mixing. Appellee’s Br. 20–22, 32–33. Chandler
 also argues that different sample fluids will compress in
 different amounts under the same pressure, and thus a
 skilled artisan cannot determine if a given viscometer’s
 chamber satisfies the “enlarged chamber” limitation due to
 the variance in how much different sample fluids compress.
 Appellee’s Br. 23–25, 32–33; see also Appellee’s Letter,
 Aug. 8, 2022, ECF No. 50. Grace disagrees with the merits
 of both arguments and asserts that both arguments are
 waived because they were not raised before the district
 court. Appellant’s Reply Br. 4–7, 15–19; Appellant’s Let-
 ter, Aug. 11, 2022, ECF No. 53. Grace also makes addi-
 tional arguments based on the extrinsic record.
 Appellant’s Br. 45–54. We will not address these argu-
 ments in the first instance. It is appropriate for the district
 court to consider these types of arguments on remand, in-
 cluding whether any have been waived. We also note that
 the district court made no finding as to the identity of the
 pertinent person of ordinary skill in the art, from whose
 perspective the “reasonable certainty” analysis must be un-
 dertaken. This oversight may well be due to the parties’
 relative inattention to this factual issue, although the res-
 olution of it may also be informative as to whether, on re-
 mand, the claims are again determined to be indefinite.
 See generally Nautilus, 572 U.S. at 901.
      In sum, we find the term “enlarged chamber” in the
 ’877 patent to mean “a chamber that is large enough to con-
 tain excess test sample prior to pressurization to prevent
 mixing of the test sample and pressurization fluid in the
 lower measurement zone when the test sample is pressur-
 ized to maximum rated pressure.” We thus vacate the dis-
 trict court’s determination that “enlarged chamber” is
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 indefinite, vacate the district court’s invalidity determina-
 tions based thereon, and remand for further proceedings
 consistent with this opinion.
    II. Means for Driving Said Rotor to Rotate Located in
                at Least One Bottom Section
      Grace also contests the district court’s construction of
 “means for driving said rotor to rotate located in at least
 one bottom section.” Grace argues that the court erred in
 finding that the term “bottom section” refers to the bottom
 section of the viscometer rather than the bottom section of
 the pressure vessel and in finding that “located in at least
 one bottom section” modifies “means for driving” rather
 than “rotor.” Appellant’s Br. 57–68, 70–71. According to
 Grace, the correct construction of “means for driving” in-
 cludes a “magnet holder” and a “direct drive” that attaches
 to the bottom section of the rotor rather than “at bottom of
 cell body.” Appellant’s Br. 67–69. We disagree and thus
 affirm the district court’s construction.
            A. The District Court’s Construction
     We first consider whether the phrase “located in at
 least one bottom section” in limitation 4(c) modifies “means
 for driving” or “rotor.” Starting with the claim language,
 we agree with the district court that the most natural read-
 ing of limitation 4(c) requires the phrase “located in at least
 one bottom section” to modify “means for driving” and not
 “rotor.” In this limitation, “means” is a noun modified by
 the prepositional phrase “for driving said rotor to rotate.”
 The noun “means” also is modified by the participle phrase
 “located in at least one bottom section.” Because the prep-
 ositional phrase is unnecessary, the sentence is best read
 as a “means” that is “located in at least one bottom section.”
 Had the patentee intended for “located in at least one bot-
 tom section” to modify “rotor,” the patentee would have
 placed the “located in at least one bottom section” phrase
 before “to rotate.”
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      That “means for driving said rotor to rotate” should be
 read as a unit, composed of a noun modified by a preposi-
 tional phrase, is confirmed by dependent claim 14.
 Claim 14 recites the viscometer of claim 4 “where said
 means for driving said rotor to rotate is . . . .” ’877 patent
 col. 13 ll. 23–24 (emphasis added). Thus, in claim 14, the
 same noun modified by the same prepositional phrase is
 used in the same manner as in claim 4, indicating that the
 patentee intended the noun and prepositional phrase to be
 read together. Thus, “located in at least one bottom sec-
 tion” modifies the entire “means” unit and not the “rotor.”
      Comparing limitations 4(b) and 4(c) supports this in-
 terpretation. Limitation 4(b) introduces the “rotor” and ex-
 plains that the rotor is located “within said pressure
 vessel.” Id. at col. 12 ll. 55–57. Limitation 4(c) introduces
 the “means for driving” and explains that the “means for
 driving” is “located in at least one bottom section.” Id. at
 col. 12 ll. 58–59. A skilled artisan reading claim 4 would
 understand that these limitations are directed to different
 components of the viscometer and also describe the corre-
 sponding locations for those components. Indeed, it would
 make little sense for limitation 4(b) to introduce the rotor,
 explain that it is located in the pressure vessel, and then,
 in a separate limitation directed to the “means for driving,”
 explain that the rotor is located in the bottom section.
      Next, we agree with the district court that the intrinsic
 record requires that the claimed “bottom section” refers to
 the bottom section of claim 4’s viscometer, not the pressure
 vessel component of the viscometer. Dependent claim 14
 explains that the “means for driving” is a “magnetic cou-
 pling across said pressure vessel wall.” Id. at col. 13
 ll. 23–25 (emphasis added). The “means for driving” thus
 cannot be in the bottom section of the pressure vessel be-
 cause claim 14 requires the “means for driving” to operate
 across the pressure vessel wall—i.e., magnetic coupling
 components must be located inside and outside the pres-
 sure vessel. Thus, the “means for driving” must be in the
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 “bottom section” of the overall viscometer rather than the
 pressure vessel because that understanding encompasses
 the “means for driving” components located outside the
 pressure vessel.
      The structure of claim 4 is consistent with this inter-
 pretation. Claim 4 is directed to a “Viscometer.” Id. at
 col. 12 l. 52. Limitations 4(a) and 4(b), however, are specif-
 ically tailored to aspects of the pressure vessel within the
 viscometer, whereas limitation 4(c) does not refer to the
 “pressure vessel.” Id. at col. 12 ll. 58–59. Reading these
 limitations together, a skilled artisan would interpret lim-
 itations 4(a) and 4(b) to refer to the pressure vessel and
 limitation 4(c) to refer to the “bottom section” the viscome-
 ter.
      This reading also is consistent with the specification,
 which explains that the primary “means for driving” the
 rotor is magnetic coupling: “A motor or gearbox drives
 magnet mount 40 to rotate carrying driving mag-
 net 38 . . . . Due to the magnetic coupling between driving
 magnet 38 and coupling magnet 34, rotor 51 rotates at the
 same revolving speed as magnet mount 40 does.” Id. at
 col. 5 ll. 42–47; see also id. at col. 8 ll. 24–30, col. 10
 ll. 36–42. The motor or gearbox, magnet mount 40, and
 driving magnet 38 are located outside the pressure vessel.
 See id. at FIGS. 1–3, col. 3 ll. 7–10. Because some of these
 components are outside the pressure vessel, they cannot be
 located in the bottom section of the pressure vessel. In-
 stead, these components must be located in the bottom sec-
 tion of the viscometer.
     Grace’s remaining arguments are unpersuasive. Grace
 argues that “top section” of the pressure vessel in limita-
 tion 4(a) means that “bottom section” in limitation 4(e) re-
 fers to the pressure vessel, and “top section” and “bottom
 section” in limitation 4(e) must both refer to the pressure
 vessel to facilitate communicating pressure between the
 two. Appellant’s Br. 58–59; Appellant’s Reply Br. 31. We
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 disagree. Limitation 4(e), consistent with our analysis
 above, can be understood as simply requiring that the en-
 larged chamber be positioned between the top section of the
 pressure vessel and bottom section of the viscometer.
      Grace also argues that the district court’s interpreta-
 tion of “means for driving” to include “magnetic coupling
 (magnet mount, gear box or motor, driving magnet, cou-
 pling magnet)” (1) excludes the patent’s preferred embodi-
 ments because certain components are outside of the
 pressure vessel and thus can cannot be located in the “bot-
 tom section,” Appellant’s Br. 63–65; (2) renders claim 14
 impossible by requiring the magnetic coupling to be inside
 the pressure vessel’s bottom section, Appellant’s Br. 65–66;
 and (3) requires the electric motor to be inside the pressur-
 ized bottom of the pressure vessel, even though a motor
 cannot work while submerged in drilling fluid, Appellant’s
 Br. 66–67. But for all of these arguments, Grace’s logic is
 circular. Each argument relies on Grace’s preferred inter-
 pretation that “bottom section” refers to the pressure ves-
 sel, not the viscometer. Under the correct interpretation
 that “bottom section” refers to the viscometer, the preferred
 embodiments are not excluded and there is no conflict with
 claim 14.
     Finally, Grace relies on claim 1 and a stipulation be-
 tween the parties to argue that the ’877 patent uses the
 terms “lower section” and “bottom section” interchangeably
 to refer to the bottom section of the pressure vessel. Appel-
 lant’s Br. 60 (citing J.A. 1297). We disagree. The stipula-
 tion Grace cites only modifies claim 1, not claim 4, and only
 changes “bottom section” in claim 1 to “lower section” to
 address the lack of antecedent basis. Appellee’s Br. 50–51.
 Additionally, when Chandler argued at the Markman hear-
 ing that “lower section” in claim 1 refers to the pressurized
 device and “bottom section” in claim 4 refers to the viscom-
 eter, J.A. 1479–80 (75:8–76:10), Grace’s counsel asked the
 agreement to be withdrawn because Grace did not intend
 for the stipulation to be used against it in relation to
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 claim 4, J.A. 1489 (85:13–23). The stipulation thus does
 not make clear that the terms “lower section” and “bottom
 section” are used interchangeably in the ’877 patent, and
 we are not persuaded that the patentee intended the terms
 to be interchangeable.
     For the foregoing reasons, we affirm the district court’s
 construction of “means for driving said rotor to rotate lo-
 cated in at least one bottom section.”
                B. Grace’s Proposed Construction
      We also reject Grace’s proposed alternate construction
 for the means for driving limitation. Grace’s proposed con-
 struction comprises two parts: (1) “means for driving” can
 be just the “magnet holder” alone because the magnet
 holder individually qualifies as a “means for driving,” Ap-
 pellant’s Br. 67–68, Appellant’s Reply Br. 22–28; and
 (2) the “direct drive” alternative to magnetic coupling as
 the “means for driving” should be construed such that it
 “attaches in the bottom section to the rotor to rotate it,”
 rather than “at the bottom of the cell body,” Appellant’s Br.
 69. We disagree.
                       1. Magnet Holder
      Grace asserts that every structure involved in relaying
 power to the rotor individually qualifies as a separate
 “means for driving.” See Appellant’s Reply Br. 26. But
 Grace misreads the specification. See, e.g., ’877 patent
 col. 5 ll. 42–47; see also id. at col. 8 ll. 24–30, col. 10
 ll. 36–42. The specification provides no details suggesting
 that the magnet holder, for example, could be solely re-
 sponsible, without additional structure, for rotating the ro-
 tor. The other magnetic coupling components also are
 required to rotate the rotor.
     Grace’s argument that its interpretation prevents ex-
 cluding the preferred embodiments is, again, circular. The
 district court’s interpretation of “means for driving” only
 excludes the preferred embodiments if the claimed “bottom
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 22                      GRACE INSTRUMENT INDUSTRIES, LLC v.
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 section” refers to the pressure vessel, not the viscometer.
 But because we have determined that “bottom section” re-
 fers to the bottom section of the viscometer, the other com-
 ponents involved in the magnetic coupling “means for
 driving” may be located inside or outside the pressure ves-
 sel. See discussion supra Discussion § II.A. We thus disa-
 gree with Grace’s attempt to define the “means for driving”
 as any individual component that relays power to the rotor.
                       2. Direct Drive
     Grace argues that the district court erred in reading a
 limitation from the written description into the means for
 driving limitation by requiring the “direct drive” to be “at
 bottom of cell body.” Appellant’s Br. 69. Grace argues that
 means-plus-function claims must be limited to disclosed
 structures and equivalents, not locations of disclosed struc-
 tures. Appellant’s Reply Br. 31–32. We disagree.
     The ’877 patent explains that magnetic coupling can be
 used to drive the rotor to rotate, or the rotor “could be
 driven to rotate with any means such as directly driven at
 the bottom of the cell body with dynamic seal, etc.” ’877
 patent col. 11 ll. 41–43 (emphasis added). The disclosed
 structure is, therefore, magnetic coupling or a direct drive
 at the bottom of the cell body, and known equivalents, con-
 sistent with the district court’s opinion. See Claim Con-
 struction Order, 2021 WL 2711987, at *7–8. We reject
 Grace’s attempt to disassociate the disclosed structure
 from the location of the disclosed structure. The specifica-
 tion indicates that the invention envisioned and claimed by
 the patentee was a direct drive attached to the bottom of
 the cell body. See, e.g., NOMOS Corp. v. BrainLAB USA,
 Inc., 357 F.3d 1364, 1367–68 (Fed. Cir. 2004) (affirming the
 district court’s construction of a “means for generating at
 least one ultrasound image” as requiring the ultrasound
 probe to be mounted to the treatment table by a fixation
 device).
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                         CONCLUSION
      We have considered Grace’s remaining arguments and
 do not find them persuasive. For the foregoing reasons, we
 vacate the district court’s determination that “enlarged
 chamber” is indefinite, vacate the district court’s invalidity
 determinations based thereon, and remand for further pro-
 ceedings consistent with this opinion. We affirm the dis-
 trict court’s construction of “means for driving said rotor to
 rotate located in at least one bottom section” and the dis-
 trict court’s judgment based thereon.
   AFFIRMED-IN-PART, VACATED-IN-PART, AND
                 REMANDED
                            COSTS

 No costs.