IP Law Daily Post-trial infringement and validity rulings upheld in long-running lawn mower patent suit
Tuesday, October 6, 2020

Post-trial infringement and validity rulings upheld in long-running lawn mower patent suit

By Jody Coultas, J.D.

In its second ruling in the case brought by Exmark against Briggs & Stratton, the Federal Circuit affirmed a lower court’s ruling on validity and prejudgment interest.

The U.S. Court of Appeals for the Federal Circuit affirmed a district court’s judgments as to infringement and no invalidity, as well as the court’s adjustment to the prejudgment interest award, in a suit between competing manufacturers of high-end commercial lawn mowers. Exmark Manufacturing Company Inc. filed a patent infringement suit against competitor Briggs & Stratton Corp., alleging infringement a patent covering high-tech lawn mower technology. An Omaha, Nebraska, district court ruled that asserted claim 1 was valid and infringed, and awarded an adjustment of prejudgment interest. The Federal Circuit agreed with the district court despite vacating construction of one of the key patent claim terms (Exmark Manufacturing Co. Inc. v. Briggs & Stratton Corp., October 6, 2020, Chen, R.).

In September 2015, a jury awarded Exmark over $24 million for Briggs’s infringement of high-tech lawn mower technology. The patent at issue—U.S. Patent No. 5,987,863 (the ’863 patent)—was directed to a multi-blade lawn mower with improved flow control baffles. A baffle is a metal structure under the mower deck that directs air flow and grass clippings during operation. Claim 1 of the patent recited a "first arcuate baffle portion," a "first elongated and substantially straight baffle portion," and a "second arcuate baffle portion" with the elongated and substantially straight baffle portion "angularly disposed … in a chord-like fashion" with respect to the second cutting blade. The parties referred to that disclosed shape as a "curved-straight-curved" baffle.

In May 2016, the district court ruled that the award was supported by ample evidence and denied Briggs’s motion for a new trial on damages. In a separate opinion, the court determined that Exmark was entitled to enhanced damages—doubling the jury’s assessment, bringing the total damages award to over $48.5 million—but not an award of attorney fees. In Exmark Mfg. Co. Inc. v. Briggs & Stratton Power Prod. Grp., LLC, 879 F.3d 1332, 1338 (Fed. Cir. 2018), the Federal Circuit vacated the jury’s finding of willful infringement, vacated the district court’s award of enhanced damages, and remanded the matter for the district court to determine whether a new trial on willfulness was necessary.

On remand, the district court again ruled that Briggs failed to prove its invalidity defense as a matter of law. Also, the court awarded enhanced damages for willfulness and prejudgment interest. Briggs appealed the district court’s rulings that claim 1 was infringed and not invalid, as well as the adjustment of prejudgment interest.

Claim construction. The Federal Circuit agreed with the district court that, to meet all of the limitations of claim 1, the discharge opening "must be one through which grass will actually discharge when grass is cut." Claim 1 recites a "discharge opening" in a "first side wall." Briggs argued that the discharge opening of claim 1 encompasses a lawn mower having a mower deck opening that does not function to discharge grass clippings. However, reading claim 1 as encompassing a lawn mower with a side discharge opening that is covered and does not discharge grass would render the word "discharge" meaningless.

The court, however, vacated the district court’s construction of the term "first flow control baffle" to the extent that it required spatial separation between the "first flow control baffle" and the "front wall." Therefore, the court reinstated the parties’ agreed-upon construction for the "first flow control baffle": "a front structure within the walls of the mower deck that controls the flow of air and grass clippings."

Anticipation. Because the court affirmed the district court’s construction of "discharge opening," it also affirmed the ruling that a prior art reference did not disclose any mower configuration meeting all of the limitations of claim 1: a "discharge opening" and a "flow control baffle." The prior art reference (Simplicity) disclosed a mulching kit that can be added to a side discharge mower. Without the mulching kit installed, the Simplicity side discharge mower did not include the claimed "flow control baffle."

Obviousness. The district court did not err in granting summary judgment of nonobviousness because there was no facts in dispute. Briggs argued that that it would have been obvious to only partially install Simplicity’s mulching kit, i.e., employing its mulching plates but discarding the plate covering the opening in the side wall and that the district court failed to address this argument. However, Briggs did not explain why it would have been obvious to partially install Simplicity’s mulching kit for the purpose of side discharge. There was no evidence as to why it would have been obvious to create a new side discharge mower by combining portions of Simplicity’s mulching and side discharge configurations. In dismissing the obviousness argument, the court noted that Briggs left its obviousness theories "undeveloped and thus inadequate to prevent summary judgment of nonobviousness."

Infringement. Although the court vacated the district court’s construction of "flow control baffle" to the extent it required spatial separation between the baffle and the front wall, it affirmed summary judgment as to infringement.

Prejudgment interest. In 2016, the district court 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." After the second jury trial, the district court again awarded prejudgment interest at the reduced U.S. Treasury rate. The court also agreed with Exmark in assigning the reduced U.S. Treasury rate to the pre-suit time period while awarding the prime rate to the post-suit time period.

In affirming the prejudgment interest ruling, the appellate court held that the district court reasonably adjusted the prejudgment interest award to reflect that the litigation had continued for longer than anticipated when the court initially awarded the lower interest rate in 2016. Because the lower interest rate was punitive in nature, it became less representative as more time passed after the suit was filed. The court could not conclude 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. Briggs argued that it was error to consider the jury’s award of enhanced damages, but did not challenge that first prejudgment interest determination for improperly considering enhanced damages when the award of that reduced interest rate favored Briggs, and it was not an abuse of discretion for the district court to adjust that interest rate to correct for an over-penalization of Exmark’s delay in filing suit.

This case is No. 19-1878.

Attorneys: J. Derek Vandenburgh (Carlson Caspers Vandenburgh & Lindquist, PA) for Exmark Manufacturing Co. Inc. Matthew Wolf (Arnold & Porter Kaye Scholer LLP) for Briggs & Stratton Corp.

Companies: Exmark Manufacturing Co. Inc.; Briggs & Stratton Corp.

MainStory: TopStory Patent GCNNews FedCirNews

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