Court Opinion

ID: 4573402
Source: CourtListenerOpinion
Date Created: 2020-10-06 16:00:37.532079+00
Date Added: 2024-06-11T13:31:52.865184
License: Public Domain

Case: 19-1878   Document: 51     Page: 1    Filed: 10/06/2020

        NOTE: This disposition is nonprecedential.

   United States Court of Appeals
       for the Federal Circuit
                 ______________________

    EXMARK MANUFACTURING COMPANY INC.,
              Plaintiff-Appellee

                            v.

            BRIGGS & STRATTON CORP.,
                Defendant-Appellant
               ______________________

                       2019-1878
                 ______________________

     Appeal from the United States District Court for the
 District of Nebraska in No. 8:10-cv-00187-JFB-CRZ, Senior
 Judge Joseph F. Bataillon.
                   ______________________

                 Decided: October 6, 2020
                 ______________________

      J. DEREK VANDENBURGH, Carlson, Caspers, Vanden-
 burgh & Lindquist PA, Minneapolis, MN, argued for plain-
 tiff-appellee. Also represented by ALEXANDER RINN,
 JOSEPH W. WINKELS.

     MATTHEW WOLF, Arnold & Porter Kaye Scholer LLP,
 Washington, DC, argued for defendant-appellant. Also
 represented by MARC A. COHN.
                 ______________________
Case: 19-1878     Document: 51      Page: 2    Filed: 10/06/2020

2                 EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.

       Before CHEN, LINN, and STOLL, Circuit Judges.
 CHEN, Circuit Judge.
      The parties and this litigation appear before us for the
 second time, having taken a long and winding road since
 Exmark filed its patent infringement suit against Briggs in
 2010 alleging infringement of certain claims of U.S. Patent
 No. 5,987,863. The procedural history leading up to the
 first appeal was thoroughly explained in our prior opinion,
 Exmark Mfg. Co. v. Briggs & Stratton Power Prods. Grp.,
 LLC, 879 F.3d 1332 (Fed. Cir. 2018), and only claim 1 re-
 mains at issue. Relevant to this second appeal, following
 grant of summary judgment of infringement and no inva-
 lidity, the case proceeded to a jury trial, where the jury
 found that Briggs willfully infringed claim 1 of the ’863 pa-
 tent. Id. at 1337. Our prior opinion vacated the district
 court’s summary judgment of no invalidity and the ulti-
 mate damages award, remanding for reconsideration of in-
 validity and, if necessary, a retrial on willfulness and
 damages. Id. at 1353–54.
     On remand, the district court again ruled that claim 1
 was not invalid as a matter of law. Following another jury
 verdict on damages, the district court awarded enhanced
 damages for willfulness. The district court also awarded
 prejudgment interest at an interest rate which was later
 adjusted in response to a motion filed by Exmark under
 Rule 59(e) of the Federal Rules of Civil Procedure. In this
 second appeal, Briggs challenges the district court’s rulings
 that claim 1 is infringed and not invalid, as well as the ad-
 justment of prejudgment interest. We affirm.
                         BACKGROUND
     The ’863 patent’s invention relates to lawn mowers,
 and specifically to the use of baffles to control and guide the
 flow of air and grass clippings through the mower. As the
 patent explains, there are various types of commercial
 lawn mowers that differ depending on “the manner in
Case: 19-1878      Document: 51      Page: 3     Filed: 10/06/2020

 EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.                    3

 which the cut grass cuttings or clippings are handled or di-
 rected.” ’863 patent at col. 1 ll. 29–36. In a “side discharge”
 mower, “the grass clippings are discharged out of one side
 of the deck and onto the ground.” Id. at col. 1 ll. 36–38. In
 a “mulching” mower, the grass clippings are not discharged
 from the side, but instead “are re-cut into finer particles
 and are then discharged directly down to the ground.” Id.
 at col. 1 ll. 38–41.
      Mowers were often converted from side discharge to
 mulching configurations through installing “mulching baf-
 fles” to maintain “an enclosed area around the [mower]
 blade” so that clippings are ultimately “directed down to
 the ground” instead of being discharged through a dis-
 charge opening in the mower deck’s sidewall. Id. at col. 1
 ll. 41–49. But the installation of such mulching baffles was
 “labor-intensive and time-consuming,” a problem which the
 ’863 patent addresses by providing a side discharge mower
 with “flow control baffles” that would combine with “remov-
 able mulching baffles which cooperate with [the] flow con-
 trol baffles to define individual mulching chambers
 surrounding each of the rotary cutting blades.” Id.
      The benefits of the invention’s convertible mower are
 two-fold. First, in the side discharge state, the flow control
 baffles’ claimed design “efficiently direct the grass clip-
 pings and air to the side discharge opening” of the mower.
Id. at col. 2 l. 66–col. 3, l. 4. Second, these same flow control
 baffles are reused in a mulching state—by “securing” the
 removable mulching baffles to the flow control baffles they
 “cooperate” “to define a substantially cylindrical mulching
 chamber around each of the cutting blades.” Id. at col. 3 ll.
 4–11. Reusing the flow control baffles as part of the mulch-
 ing chamber in the mulching state simplified the process of
 converting between side discharge and mulching states; in-
 stead of installing an entire mulching chamber, only the
 relatively small and easily installed removable mulching
 baffles need be secured to the existing flow control baffles.
Id. at col. 5 ll. 51–56 (“The mulching baffles . . . are quickly
Case: 19-1878    Document: 51      Page: 4   Filed: 10/06/2020

4                EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.

 and easily installed on the mower deck to convert the side
 discharge mower deck into a mulching deck with a mini-
 mum amount of material being required.”); see also id. at
 col. 1 ll. 41–49.
     Claim 1 is directed to the side discharge mower and re-
 cites:
    1. A multiblade lawn mower, comprising:
     a mower deck comprising a top wall, a front wall,
    a back wall, and first and second side walls defin-
    ing a downwardly directed opening;
    each of said front wall, said back wall, and said op-
    posite side walls having interior and exterior sur-
    faces;
    said first side wall having a discharge opening
    formed therein;
    said discharge opening having rearward and for-
    ward ends;
    means operatively connected to said mower deck
    for moving said mower deck along the ground;
    first and second cutting blades having blade tips
    rotatably disposed within said mower deck;
    power means operatively connected to said cutting
    blades for causing the rotation of each of said cut-
    ting blades whereby the blade tip path of each of
    said cutting blades defines a circle;
    a first flow control baffle positioned in said mower
    deck which extends downwardly from the interior
    surface of said top wall between said cutting blades
    and said front wall;
    said first flow control baffle extending substan-
    tially continuously from a first location adjacent
    the interior surface of said second side wall to a
Case: 19-1878      Document: 51    Page: 5      Filed: 10/06/2020

 EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.                 5

     second location adjacent the interior surface of said
     first side wall and adjacent the forward end of said
     discharge opening;
     said first flow control baffle comprising a first ar-
     cuate baffle portion, having first and second ends,
     which extends from the interior surface of said sec-
     ond side wall partially around said first cutting
     blade, a first elongated and substantially straight
     baffle portion, having first and second ends, ex-
     tending from said second end of said first arcuate
     baffle portion, a second arcuate baffle portion, hav-
     ing first and second ends, which extends from said
     second end of said first elongated and substantially
     straight baffle portion partially around said second
     cutting blade;
     a second flow control baffle positioned in said
     mower deck which extends downwardly from the
     interior surface of said top wall rearwardly of said
     cutting blades; and
     said second flow control baffle including a plurality
     of semi-circular baffle portions, each of said baffle
     portions being positioned adjacent the blade tip
     path of one of said cutting blades;
     said first and second flow control baffles defining a
     plurality of open throat portions which are posi-
     tioned between adjacent cutting blades.
 ’863 patent at claim 1 (emphases added).
      Claim 4, although not at issue, is relevant to the par-
 ties’ dispute over the construction of “discharge opening” in
 claim 1. In particular, claim 4, which depends from claim
 1 through claim 2, is directed to the conversion of the side
 discharge mower to a mulching mower:
     4. The lawn mower of claim 2 further comprising a
     plurality of selectively removable mulcher baffles
Case: 19-1878     Document: 51      Page: 6    Filed: 10/06/2020

6                 EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.

     which close said throat portions and said discharge
     opening to define a substantially cylindrical mulch-
     ing chamber around each of said cutting blades.
Id. at claim 4 (emphases added).
      On remand after the first appeal to our court in 2018,
 the district court was to “reach its own independent conclu-
 sion,” separate from the Board’s rulings during various
 reexaminations, “on whether a genuine issue of fact exists
 regarding invalidity” of claim 1. Exmark, 879 F.3d at 1344.
 In reconsidering the invalidity issue as to claim 1, the dis-
 trict court was also to “resolve any remaining claim con-
 struction disputes.” Id. After receiving additional briefing
 from the parties, the district court reaffirmed its prior
 grant of summary judgment of no invalidity of claim 1.
     Construing the claims, the district court determined
 that “the claim language . . . requires some ‘spatial separa-
 tion’” between the first flow control baffle and the front
 wall, and the claimed “discharge opening” was not met by
 a prior art “opening” that was obstructed. J.A. 43–44. The
 district court denied Briggs’s motion for summary judg-
 ment on indefiniteness of claim 1, which argued that the
 court’s construction had imposed an indefinite requirement
 that the baffle’s control of grass clippings must have
 “meaningful effect.” J.A. 84–85. Based on its claim con-
 structions, the district court reaffirmed its decision on sum-
 mary judgment that claim 1 was not invalid, rejecting
 Briggs’s arguments that claim 1 was anticipated by and ob-
 vious over a brochure disclosing a lawn mower mulching
 kit from Simplicity Manufacturing Co. (Simplicity). J.A.
 45.
      After the district court reaffirmed its ruling of no inva-
 lidity of claim 1, and on the basis of the undisturbed in-
 fringement ruling from 2015, the case proceeded to a retrial
 on damages. Following a jury verdict on damages, the dis-
 trict court then entered judgment awarding enhanced dam-
 ages for willful infringement and prejudgment interest at
Case: 19-1878      Document: 51    Page: 7      Filed: 10/06/2020

 EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.                 7

 the U.S. Treasury rate instead of the prime rate. J.A. 175–
 80. Exmark moved under Rule 59(e) to amend the judg-
 ment by altering the prejudgment interest rate. The court
 granted Exmark’s motion, maintaining the lower U.S.
 Treasury rate for the six-year period before the lawsuit was
 filed and applying the higher prime interest rate to the
 nine-year period post-suit filing. J.A. 189–91.
     Briggs appeals the district court’s orders (1) granting
 summary judgment of no invalidity; (2) denying summary
 judgment of indefiniteness; (3) granting summary judg-
 ment of infringement; and (4) adjusting prejudgment inter-
 est under Rule 59(e). We have jurisdiction under 28 U.S.C.
 § 1295(a)(1).
                          DISCUSSION
     We review the district court’s grant of summary judg-
 ment according to the law of the regional circuit. Phil–In-
 sul Corp. v. Airlite Plastics Co., 854 F.3d 1344, 1353 (Fed.
 Cir. 2017). The Eighth Circuit reviews a district court’s
 grant of summary judgment de novo. Id. (citing Wilson v.
 Spain, 209 F.3d 713, 716 (8th Cir. 2000)). “Summary judg-
 ment is appropriate if ‘the movant shows that there is no
 genuine dispute as to any material fact and the movant is
 entitled to judgment as a matter of law.’” Id. (quoting Fed.
 R. Civ. P. 56(a)).
                    I. CLAIM CONSTRUCTION
     “[T]he ultimate issue of the proper construction of a
 claim should be treated as a question of law.” Teva Pharm.
 USA, Inc. v. Sandoz, Inc., 574 U.S. 318, 328–29 (2015). We
 review any “subsidiary factual findings [on extrinsic evi-
 dence]     under    the     ‘clearly   erroneous’    stand-
 ard.” Id. “[W]hen the district court reviews only evidence
 intrinsic to the patent (the patent claims and specifica-
 tions, along with the patent’s prosecution history), the
 judge’s determination will amount solely to a
Case: 19-1878     Document: 51      Page: 8    Filed: 10/06/2020

8                 EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.

 determination of law, and the Court of Appeals will review
 that construction de novo.” Id. at 331.
      The parties’ dispute as to whether claim 1 is invalid
 over the Simplicity prior art centers on the construction of
 two claim terms: “discharge opening” and “flow control baf-
 fle.” We address each in turn.
                    a. “Discharge opening”
     Briggs argues that the discharge opening of claim 1 en-
 compasses a lawn mower having a mower deck opening
 that does not function to discharge grass clippings.
 Briggs’s argument relies on the relationship between claim
 1 and dependent claim 4, which recites “selectively remov-
 able mulcher baffles which close” the “discharge opening.”
 In Briggs’s view, because the removable mulcher baffles of
 claim 4 close off the discharge opening, the discharge open-
 ing of claim 1 need not discharge any grass. We disagree.
     While we begin our analysis with the language of the
 claim itself, see Phillips v. AWH Corp., 415 F.3d 1303, 1312
 (Fed. Cir. 2005), the claims “do not stand alone. Rather,
 they are part of ‘a fully integrated written instrument,’ . . .
 consisting principally of a specification that concludes with
 the claims.” Id. at 1315 (quoting Markman v. Westview In-
 struments, Inc., 52 F.3d 967, 978 (Fed. Cir. 1995)). “For
 that reason, claims ‘must be read in view of the specifica-
 tion, of which they are a part.’” Id. (quoting Markman, 52
 F.3d at 979).
     Claim 1 recites a “discharge opening” in a “first side
 wall.” ’863 patent at claim 1. To read claim 1 as encom-
 passing a lawn mower with a side discharge opening that
 is covered and thus cannot discharge grass would render
 the word “discharge” meaningless. Bicon, Inc. v. Strau-
 mann Co., 441 F.3d 945, 950 (Fed. Cir. 2006) (explaining
 that to read limitations out of a claim would “be contrary
 to the principle that claim language should not be treated
 as meaningless”).
Case: 19-1878      Document: 51     Page: 9     Filed: 10/06/2020

 EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.                   9

     Consistent with the specification, the side discharge
 mower of claim 1 is open to conversion into other states by
 the addition of other components. Briggs acknowledges
 that claim 1 “recites a ‘multiblade lawn mower’ that con-
 verts between side discharging and mulching.’” Appel-
 lant’s Reply Br. at 1. As recited in claim 4, one such
 conversion is through the addition of a “removable” struc-
 ture, i.e., “selectively removable mulcher baffles,” whereby
 the mower is converted from a side discharge state into a
 mulching state. Id. at claim 4; see also id. at col. 3 ll. 4–11.
 But the addition of the removable mulcher baffles in claim
 4 does not change the scope of claim 1, which continues to
 be directed to a mower with a side discharge state having
 particular claimed features, including a “first side wall
 having a discharge opening” and a “first control baffle ex-
 tending substantially continuously from a first location ad-
 jacent the interior surface of said second side wall to a
 second location adjacent the interior surface of said first
 side wall and adjacent the forward end of said discharge
 opening.” Id. at claim 1.
      As indicated by the “selectively removable” aspect of
 the recited mulcher baffles, claim 4’s added claim elements
 provide claim 1’s mower with an additional mulching state
 in which the removable mulcher baffles combine with the
 flow control baffles. While it is true that, in the mulching
 state with the mulcher baffles installed, the discharge
 opening cannot discharge grass, claim 4 also preserves the
 side discharge state of claim 1 with a functioning “dis-
 charge opening” and “control baffle” when the mulcher baf-
 fles are “selectively remov[ed].” Id. at claims 1, 4. Thus,
 we agree with the district court that, to meet all of the lim-
 itations of claim 1, the discharge opening “must be one
 through which grass will actually discharge when grass is
 cut.” J.A. 44.
Case: 19-1878     Document: 51      Page: 10     Filed: 10/06/2020

 10               EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.

                    b. “Flow control baffle”
      Briggs argues that the district court erred in importing
 a requirement of spatial separation between the claimed
 “first flow control baffle” and the front wall. We agree. Alt-
 hough the district court “adopted the parties’ agreed-to con-
 struction of ‘first flow control baffle’ as ‘a front structure
 within the walls of the mower deck that controls the flow
 of air and grass clippings,’” J.A. 33, the court further ob-
 served that “[i]n context, to a person of ordinary skill in the
 art, a baffle is separate from and spaced away from the
 front wall in order to constitute a ‘flow control baffle.’” J.A.
 42. The court explained that Simplicity’s mounting plates,
 which “run along, contact and conform to the front wall are
 not ‘flow control baffles’ due to a lack of spatial separation
 between the mounting plates and the front wall.” J.A. 41.
 Reasoning that “[t]he claims of the ’863 patent expressly
 require two distinct structures: a ‘front wall’ and a front
 ‘flow control baffle,’” and that the front flow control baffle
 must be “between” the blades and the front wall, the court
 concluded that this distinction “requires some ‘spatial sep-
 aration.’” J.A. 43.
     Although claim 1 recites both a “front wall” and a “first
 flow control baffle,” the separate recitation of these struc-
 tures does not preclude physical contact between them.
 Likewise, a mower having a “first flow control baffle” that
 contacts the “front wall” can still meet the claimed require-
 ment that the baffle is positioned between the front wall
 and the cutting blades. ’863 patent at claim 1 (requiring
 that the “first flow control baffle” “extends downwardly
 from the interior surface of said top wall between said cut-
 ting blades and said front wall”). Exmark itself argued
 during reexamination that the claim does not preclude con-
 tact between the flow control baffle and the front wall. J.A.
 28500–01 (“We don’t disagree that [the flow control baffle]
 can contact – you can bolt the thing to the front wall and it
 would still be a baffle.”).
Case: 19-1878    Document: 51      Page: 11     Filed: 10/06/2020

 EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.                  11

      The specification, which is entirely silent as to any spa-
 tial requirement between front wall and flow control baffle,
 does not support the district court’s construction. To the
 extent that the specification addresses any spacing be-
 tween flow control baffles and walls of the mower, it is to
 suggest that the two can be merged and form part of the
 same structure. Id. at col. 4, ll. 34–36 (explaining that
 “back wall 36 may be eliminated with the flow control baf-
 fle 68 forming the back wall of the mower deck”). Although
 the figures in the specification depict some distance be-
 tween the front wall and corresponding flow control baffle,
 id. at Figs. 3–4, these exemplary illustrations are not suf-
 ficient to impose a spatial separation requirement on claim
 language that is otherwise silent as to any required baffle-
 wall spacing. “We have repeatedly held that it is not
 enough that the only embodiments, or all of the embodi-
 ments, contain a particular limitation to limit claims be-
 yond their plain meaning.” Unwired Planet, LLC v. Apple
 Inc., 829 F.3d 1353, 1359 (Fed. Cir. 2016) (citations and
 quotations omitted).
     For the above reasons, we vacate the district court’s
 construction to the extent that it required spatial separa-
 tion between the “first flow control baffle” and the “front
 wall.” 1 We thus reinstate the parties’ agreed-upon con-
 struction for the “first flow control baffle”: “a front struc-
 ture within the walls of the mower deck that controls the
 flow of air and grass clippings.” J.A 33. Our rejection of
 this particular construction, however, does not require a
 reversal or remand of the district court’s validity or in-
 fringement rulings, which we turn to next.

     1   Because we hold that the district court erred in im-
 porting a requirement of spatial separation into claim 1, we
 do not reach Briggs’s argument that such a spatial separa-
 tion requirement would be indefinite under 35 U.S.C.
 § 112.
Case: 19-1878    Document: 51      Page: 12   Filed: 10/06/2020

 12              EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.

                        II. INVALIDITY
                       a. Anticipation
      Under 35 U.S.C. § 102(b), a prior art reference will an-
 ticipate if it “disclose[s] each and every element of the
 claimed invention . . . arranged or combined in the same
 way as in the claim.” In re Gleave, 560 F.3d 1331, 1334
 (Fed. Cir. 2009) (citations and internal quotation marks
 omitted). “While anticipation is a question of fact, it may
 be decided on summary judgment if the record reveals no
 genuine dispute of material fact.” Encyclopaedia Britan-
 nica, Inc. v. Alpine Elecs. of Am., Inc., 609 F.3d 1345, 1349
 (Fed. Cir. 2010).
     Because the district court correctly construed claim 1,
 reciting a “discharge opening,” to require a mower with a
 side discharge state, i.e., that grass is discharged through
 the opening, the district court likewise did not err in con-
 cluding that claim 1 is not anticipated by Simplicity’s
 mulching mower.
     Simplicity discloses a mulching kit that can be added
 to a side discharge mower. J.A. 23915. The parties do not
 dispute that, without the mulching kit installed, the Sim-
 plicity side discharge mower does not include the claimed
 “flow control baffle.” Rather, Briggs contends that, with
 the mulching kit installed, the Simplicity mower contains
 both the “flow control baffle” and the “discharge opening.”
 But Briggs’s arguments on appeal rely on its proposed con-
 struction of the “discharge opening” as encompassing an
 opening that does not discharge any grass. The parties do
 not appear to dispute that the Simplicity mulching kit,
 when installed, covers the side opening in a way that pre-
 vents discharge of grass, i.e., the opening is not a “dis-
 charge” opening as construed by the district court. That
 leaves Briggs with relying on a prior art mulching mower
 to anticipate a mower in a claimed side discharge state.
 Because we affirm the district court’s construction of “dis-
 charge opening,” we likewise affirm the district court’s
Case: 19-1878    Document: 51      Page: 13     Filed: 10/06/2020

 EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.                 13

 ruling that Simplicity does not disclose any mower config-
 uration meeting all of the limitations of claim 1: a “dis-
 charge opening” and a “flow control baffle.”
                        b. Obviousness
      In the alternative, Briggs argues that that it would
 have been obvious under 35 U.S.C. § 103(a) to only par-
 tially install Simplicity’s mulching kit, i.e., employing its
 mulching plates but discarding the plate covering the open-
 ing in the side wall. Briggs complains that the district
 court failed to address this partial installation argument.
 In support of this argument, Briggs points to testimony by
 its expert, Mr. Del Ponte, that customers might leave
 mulching baffles in place when converting a mower from
 mulching to side discharge modes. We agree with Exmark
 that Mr. Del Ponte’s speculative testimony fails to create a
 genuine question of material fact.
      As an initial matter, Briggs’s briefing on appeal does
 not attempt to explain why it would have been obvious to
 partially install Simplicity’s mulching kit for the purpose
 of side discharge. Instead, Briggs offers the conclusory as-
 sertion that it “argued, based on Mr. Del Ponte’s testimony,
 that it would have been obvious to a person of ordinary skill
 to mow with the cover removed from the discharge open-
 ing” and alleged as a general matter that “[s]everal pieces
 of prior art show baffles like the one in Simplicity in a side
 discharge configuration.” Appellant’s Opening Br. at 61–
 62. Before the district court, Briggs offered equally conclu-
 sory arguments on its partial installation theory, asserting
 only that “Mr. Del Ponte testified that it would have been
 obvious to a person of ordinary skill to try to mow with the
 cover removed from the discharge opening” and “[s]everal
 pieces of prior art show baffles like the one in Simplicity in
 a side discharge configuration, providing further motiva-
 tion to do so with Simplicity.” J.A. 27812–13. On appeal
 and before the district court, Briggs has focused its efforts
 on advancing its construction of “discharge opening” for
Case: 19-1878    Document: 51       Page: 14    Filed: 10/06/2020

 14               EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.

 anticipation, leaving its obviousness theories undeveloped
 and thus inadequate to prevent summary judgment of non-
 obviousness. Ecolochem, Inc. v. S. Cal. Edison Co., 227
F.3d 1361, 1372 (Fed. Cir. 2000) (“Broad conclusory state-
 ments regarding the teaching of multiple references, stand-
 ing alone, are not ‘evidence.’”).
      Even considering Mr. Del Ponte’s testimony, we do not
 see any concrete theory for why it would have been obvious
 to create a new side discharge mower by combining por-
 tions of Simplicity’s mulching and side discharge configu-
 rations. Based on second-hand information heard from
 “[p]eople who are in contact with mulching kits,” Mr. Del
 Ponte asserted that customers “may choose, and in most
 cases will choose, to keep mulch baffles . . . installed in the
 mower deck rather than go through the process of remov-
 ing them and reinstalling them as they move from cus-
 tomer to customer to customer.” J.A. 25609 at p. 218 l. 10–
 p. 220 l. 21. Lacking personal knowledge of how Simplic-
 ity’s mower might be configured by customers, Mr. Del
 Ponte instead suggested that it was “conceivable” that, for
 some unspecified “grass conditions,” keeping mulch baffles
 in place might not have a significant detrimental impact on
 the ability of the mower to cut grass in side discharge mode.
Id. at p. 219 ll. 5–12 (testifying that “it’s very conceivable
 that closing off the raised front skirt with a baffle could
 have a negligible effect on – on some grass conditions”).
 Mr. Del Ponte’s testimony was untethered to Simplicity’s
 mower and thus too skeletal and speculative to create a
 material factual dispute as to why it would have been ob-
 vious to combine parts of Simplicity’s side discharge and
 mulching configurations. “[C]onclusory expert assertions
 do not give rise to a genuine issue of material fact.” Streck,
 Inc. v. Rsch. & Diagnostic Sys., Inc., 665 F.3d 1269, 1290
 (Fed. Cir. 2012). Likewise, the existence of other prior art
 with baffles does not, without more, create a material fac-
 tual dispute over whether it would have obvious to combine
 Simplicity’s mulching and side discharge configurations.
Case: 19-1878    Document: 51      Page: 15     Filed: 10/06/2020

 EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.                  15

 In the absence of any material factual dispute, district
 court did not err in granting summary judgment of nonob-
 viousness.
                      III. INFRINGEMENT
     In its summary judgment order in 2015, the district
 court concluded that “[t]he evidence shows that every lim-
 itation recited in the claims is found in the accused de-
 vices,” and no reasonable jury could have found otherwise.
 J.A. 23966–67. We agree. Like the district court, we see
 no difference in the claimed “flow control baffle” and the
 structure of the accused Briggs mower. This outcome is
 immediately apparent from a comparison of the accused
 mower to the limitations of claim 1, and is illustrated by a
 comparison of Figure 4 of the ’863 patent to Briggs’s ac-
 cused mower provided by Exmark:

 Appellee’s Br. at 63; see also ’863 patent at Fig. 4; J.A.
 21520. Although we vacate the district court’s construction
 of “flow control baffle” to the extent it required spatial sep-
 aration between the baffle and the front wall, summary
 judgment of infringement is appropriate regardless of
 whether “flow control baffle” is construed to require spatial
 separation.
                 IV. PREJUDGMENT INTEREST
    In the Eighth Circuit, the grant or denial of a motion
 under Rule 59(e) is reviewed for an abuse of discretion.
 Mathenia v. Delo, 99 F.3d 1476, 1480 (8th Cir. 1996).
     In 2016, following the first jury trial, Exmark moved
 for prejudgment interest in the amount of $8,545,058,
Case: 19-1878     Document: 51      Page: 16     Filed: 10/06/2020

 16               EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.

 representing interest at the “prime” rate applied to dam-
 ages accrued prior to the date of judgment. The district
 court instead awarded prejudgment interest of $1,540,614
 at the lower U.S. Treasury rate to penalize Exmark for its
 delay in filing suit, which “contributed, to some extent, to
 a longer period of prejudgment interest.” 2 J.A. 21227–28.
 After the second jury trial, the district court again awarded
 prejudgment interest at the reduced U.S. Treasury rate,
 and Exmark moved under Rule 59(e) to adjust the prejudg-
 ment interest. The district court was persuaded by
 Exmark’s argument that, because the “the case ha[d] now
 been pending for almost nine years,” the “historically low,
 near-zero” U.S. Treasury rate during this time overpenal-
 ized Exmark and was thus “not sufficient to adequately
 compensate Exmark.” J.A. 189–91. Adopting Exmark’s
 proposed bifurcation of the prejudgment interest award
 into pre-suit and post-suit time periods, the district court
 assigned the reduced U.S. Treasury rate to the pre-suit
 time period while awarding the prime rate to the post-suit
 time period. Id.
      In bifurcating the prejudgment interest award, the dis-
 trict court also stated:
      Circumstances have changed since the first trial of
      this action. In particular, the Court has awarded
      $9.9 million less in enhanced damages.
 J.A. 190. Briggs argues that the district court erred in re-
 lying on a reduction in enhanced damages as a justification
 for increasing the prejudgment interest rate. In particular,
 Briggs argues that enhanced damages are a punitive

      2   The district court stated that its award following
 the first jury trial also “reflect[ed] the facts that Briggs pre-
 vailed on some claims (the redesigned models), and that
 Exmark was awarded enhanced damages.” Id.
Case: 19-1878    Document: 51      Page: 17     Filed: 10/06/2020

 EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.                  17

 remedy and thus not relevant to the choice of interest rate
 for the compensatory remedy of prejudgment interest.
      We decline to overturn the district court’s discretionary
 determination of prejudgment interest. The district court
 reasonably adjusted the prejudgment interest award to re-
 flect that the litigation had continued for longer than the
 district court had anticipated when it initially awarded the
 lower interest rate in 2016. Because the lower interest rate
 initially awarded was intended to penalize Exmark for its
 delay in filing suit, it became less representative as more
 time passed after the suit was filed. Under the circum-
 stances in this long, drawn-out litigation, we cannot con-
 clude that it was an abuse of discretion for the district court
 to correct the initially assigned interest rate by bifurcating
 the prejudgment interest award between pre-suit and post-
 suit time periods. 3 Assigning a reduced prejudgment in-
 terest rate to only the pre-suit time period more accurately
 represented Exmark’s contribution to a longer period of
 prejudgment interest.
      If, as Briggs urges, it was error to consider the jury’s
 award of enhanced damages, then that speaks to the dis-
 trict court’s first prejudgment interest determination,
 which likewise accounted for the enhanced damages
 award. But Briggs did not challenge that first prejudgment
 interest determination for improperly considering

     3   The parties also dispute whether, in the Eighth
 Circuit, Rule 59(e) motions are held to the same standard
 as Rule 60(b) motions and thus granted only in “exceptional
 circumstances.” Appellant’s Opening Br. at 69 (citing
 Jones v. Swanson, 512 F.3d 1045, 1048 (8th Cir. 2008)).
 But even when considering whether “exceptional circum-
 stances” have occurred, “[t]he district court has wide dis-
 cretion in ruling on a Rule 60(b) motion, and we will only
 reverse for a clear abuse of discretion.” Jones, 512 F.3d at
 1048.
Case: 19-1878    Document: 51      Page: 18   Filed: 10/06/2020

 18              EXMARK MFG. CO.   v. BRIGGS & STRATTON CORP.

 enhanced damages when the award of that reduced inter-
 est rate favored Briggs, and it was not an abuse of discre-
 tion for the district court to adjust that interest rate to
 correct for an over-penalization of Exmark’s delay in filing
 suit.
                        CONCLUSION
      We have considered Briggs’s remaining arguments and
 find them unpersuasive. For the reasons stated above, we
 affirm the district court’s judgments as to infringement
 and no invalidity, as well as the court’s adjustment to the
 prejudgment interest award under Rule 59(e).
                        AFFIRMED