Oxygenator Water Technologies, Inc. v. Tennant Company

Background

Oxygenator Water Technologies, Inc. (OWT) owns a family of reissued electrolysis patents — U.S. Patent Nos. RE45,415 ('415), RE47,092 ('092), and RE47,665 ('665) — covering the production of micro- and nanobubbles in water. All three patents share the same specification, claim priority to applications filed in 2003, and trace back to a parent patent (U.S. Patent No. 6,689,262) that originally issued to Aqua Innovations in 2004 and was assigned to OWT in 2008. Tennant Company manufactures commercial and industrial floor-cleaning machines, many of which include an electrolysis module (the 'ec-H2O module') that allows cleaning without detergents.

OWT filed suit in 2020. Before trial, the court granted summary judgment that Tennant's newer 'ec-H2O NanoClean modules' did not infringe. The parties stipulated that certain ec-H2O modules infringed specific claims; remaining contested issues were tried to a jury in November 2024. The three issues tried were: (1) whether Tennant's ec-H2O modules with 36-volt batteries infringed claims 13, 18, 24, and 26 of the '415 patent; (2) whether Tennant's infringement (both stipulated and contested) was willful; and (3) the amount of damages.

The jury returned a unanimous verdict entirely in OWT's favor: it found infringement of the '415 patent both literally and under the doctrine of equivalents (a legal doctrine that holds a product infringes if it performs substantially the same function in substantially the same way with substantially the same result, even if not literally covered by the patent's language), found indirect infringement, found willfulness dating to 2015, and awarded $9,815,595 in damages (based on 18,558 infringing modules at $529 per module).

Tennant's Motion for Judgment as a Matter of Law (JMOL) and New Trial

Legal Standard

Judgment as a matter of law (JMOL) — a ruling that no reasonable jury could have reached the verdict it did — requires a 'complete absence of probative facts to support a verdict.' A new trial under Federal Rule of Civil Procedure 59 is warranted only to avoid a miscarriage of justice, such as where the verdict is against the clear weight of the evidence or the result of passion or prejudice. Courts must view the evidence in the light most favorable to the prevailing party and may not reweigh credibility.

JMOL of No Direct Infringement (Denied)

The '415 patent claims at issue require a 'power source [that] produces a voltage no greater than about 28.3 volts.' Tennant's accused modules use a 36-volt battery. OWT's expert, Dr. Seth Miller, testified that the module's power source combined the 36-volt battery with an electronic control board that used pulse width modulation (PWM) — rapidly toggling power on and off 2,000 times per second — to produce an average output voltage of about 2.5 volts, well below 28.3 volts. Tennant's expert countered that the voltage was either '36 or nothing' and could not satisfy the claim language.

The court denied JMOL on literal infringement, finding substantial evidence supported the jury's verdict. The dispute was a classic battle of experts; the jury chose to believe Dr. Miller, and it is not the court's role to reweigh that credibility determination. The court also rejected Tennant's argument that Dr. Miller invited improper claim construction (i.e., that the jury impermissibly expanded the meaning of the patent's language), finding instead that the jury permissibly applied plain and ordinary meaning to the phrase 'produces a voltage no greater than about 28.3 volts.'

On the doctrine of equivalents, the court found Dr. Miller provided sufficient 'particularized testimony and linking argument' — a requirement under Federal Circuit law — by extensively explaining PWM before his equivalents opinion and then expressly linking that earlier testimony to his conclusion that any difference between the patent's voltage limitation and the accused product was insubstantial. The court noted that Federal Circuit precedent expressly permits an expert to incorporate earlier testimony rather than repeat it when transitioning to a doctrine of equivalents analysis.

JMOL of No Willful Infringement Before 2019 (Denied)

Willfulness requires that an infringer acted deliberately or intentionally in the face of a known or obvious risk of infringement. Tennant argued there was no evidence it knew of the '415 patent before 2019.

The court found substantial circumstantial evidence supported the jury's willfulness finding from 2015. The evidence included: (1) a Tennant engineer purchased and reverse-engineered a patent-marked product called a 'Bait Keeper' (made by Aqua Innovations, OWT's predecessor) at a Cabela's store, and Tennant's internal documents showed it sought 'equivalence to the Cabela's breadboard' in designing its own sparger; (2) the engineer cited the Bait Keeper and the parent patent in his own patent application; (3) OWT approached Tennant in 2010 about licensing; (4) Tennant set up patent-tracking alerts for micro- and nanobubble patents from 2012 to 2019, and those alerts flagged the parent patent in 2012; (5) Tennant was researching nanobubble technology around the time the '415 patent reissued in 2015; (6) Tennant considered but rejected removing the sparger between 2015 and 2018 because it was too expensive; and (7) a Tennant employee shredded physical copies of patent search results. The court found the jury could reasonably infer from this totality that Tennant knew or should have known of the '415 patent when it reissued and that it was infringing.

New Trial Based on Jury Taint (Denied)

Tennant argued that allowing pre-2019 willfulness evidence to go to the jury inflamed the jury and tainted its verdicts on other issues. The court denied this request. Even had JMOL on willfulness been granted, the underlying evidence would still have been presented to the jury — Tennant had not sought summary judgment on pre-2019 willfulness, had not moved to exclude the evidence pretrial, and had not objected during trial. Moreover, the court found OWT's closing arguments on willfulness were explicitly linked to that issue and could not, standing alone, have caused the kind of passion or prejudice warranting a new trial. The court also noted Tennant had never requested bifurcation of the willfulness issue, waiving that argument.

JMOL of No Indirect Infringement (Denied)

Indirect infringement (both induced and contributory) requires knowledge of the infringed patent. Because the court found sufficient evidence of willfulness — and thus knowledge of the '415 patent since 2015 — the indirect infringement JMOL failed for the same reasons.

JMOL on Overseas Units (Denied)

Tennant sought to exclude damages for units sold overseas between 2015 and 2018, arguing the Patent Act requires infringement to occur within the United States. The jury heard evidence that Tennant manufactured and tested the ec-H2O modules in Michigan before assembling some scrubbers in the Netherlands. OWT argued at closing that testing the modules in the United States constituted practicing the method claims of the '415 patent. The court found this was not a JMOL issue — Tennant's argument was merely an attack on the weight of evidence, not a showing that no reasonable jury could have reached this conclusion.

JMOL on 2,851 Additional Units in the 2015 Royalty Base (Granted in Part, But No Impact on Verdict)

Tennant challenged inclusion of 2,851 commercial floor scrubbers from a 2015 transition period — units manufactured before the '415 patent issued but sold after. Because the patent claims at issue are method claims (covering the use of a process, not the sale of a product), OWT had to show Tennant itself used the infringing method in those units. The court agreed with Tennant that OWT's evidence — that the units 'could have been tested' or 'may have been turned on as a demonstration' — was too speculative to support direct infringement for those units.

However, the court found this ruling had no practical effect on the verdict. The jury also found indirect infringement (infringement by Tennant's customers using the machines), which would have occurred whenever customers operated the machines. Because the verdict form did not ask the jury to differentiate between direct and indirect infringement for each unit, the court declined to disturb the overall damages figure.

New Trial on Damages (Denied)

Tennant argued OWT's damages expert, Dr. Timothy Nantell, improperly applied the entire market value rule (EMVR) — a narrow exception that allows damages based on the full value of a product only when the patented feature drives consumer demand for the entire product. Tennant contended Dr. Nantell failed to properly apportion the value of the infringing sparger from the rest of the ec-H2O module.

The court disagreed, finding Dr. Nantell's opinion was apportioned. He set the royalty base against the value of the ec-H2O module itself — not the floor scrubber machine or Tennant's total revenue — and further calculated his recommended royalty of $529 per module as approximately half of the $1,058 in incremental profit Tennant derived from the module in industrial scrubbers, reflecting only the sparger's contribution. The court distinguished this from EMVR cases like Mirror Worlds, where a plaintiff had tried to use the entire revenue of Apple's product lines as the royalty base. The court also rejected Tennant's argument that OWT advanced a 'new damages theory' at trial, finding Dr. Nantell had previously offered the same alternative analysis in his expert report.

OWT's Motion for Enhanced Damages, Fees, Interest, and Costs

Enhanced Damages (Granted at 30%)

Under 35 U.S.C. § 284, a court may increase a patent damages award up to three times. The Supreme Court in Halo Electronics, Inc. v. Pulse Electronics, Inc. held that enhanced damages should generally be reserved for egregious cases of willful misconduct. Courts assess enhancement under nine non-binding factors from Read Corp. v. Portec, Inc. The court analyzed each:

Conclusion: Five factors favored enhancement (to varying degrees) and four did not. The court also considered that the jury adopted Dr. Nantell's royalty figure in full — a number the court described as sitting at the high end of credible proposals. The court enhanced the damages award by 30%, adding $2,944,679 to the $9,815,595 verdict for a total of $12,760,274.

Attorney Fees Under 35 U.S.C. § 285 (Denied)

The Patent Act allows attorney fees in 'exceptional cases' — those that stand out from others based on the substantive weakness of a party's litigation position or unreasonable litigation conduct. The court denied fees. While OWT won at trial, the case was hard-fought and Tennant had prevailed on significant positions at earlier stages (claim construction and summary judgment on the e-cell). Tennant's stipulation to certain infringement was a reasonable litigation choice, not evidence of bad faith. Tennant maintained credible defense theories at trial on willfulness and damages. The court further noted that a willfulness finding alone does not make a case exceptional for fee purposes, and that OWT could not claim fees for the cost of litigating the broader lawsuit that was partially narrowed against it.

Prejudgment Interest (Granted from March 17, 2015 at Minnesota Statutory Rate)

Prejudgment interest under § 284 ordinarily runs from the date of first infringement. Tennant argued interest should start only in 2019, when OWT first accused it of infringement, contending OWT's delay constituted 'undue delay' that should toll interest. The court rejected this, relying on the Federal Circuit's decision in Kaufman v. Microsoft Corp., which held that waiting to sue — even for five years — does not alone constitute undue delay, and that a defendant must show it was prejudiced. Tennant showed no prejudice; it made no effort to stop infringing even after the lawsuit was filed in 2020.

On the rate, the court adopted Minnesota's statutory rate of 10% per year (Minn. Stat. § 549.09(c)(2)) over Tennant's preferred prime rate, citing consistent district practice and the need to adequately compensate OWT.

Post-Judgment Interest (Granted)

Post-judgment interest is mandatory under 28 U.S.C. § 1961(a) and accrues from the date judgment is entered at the weekly average one-year Treasury yield. It applies to both the damages award and the prejudgment interest amount.

Costs

The court awarded costs to OWT under Federal Rule of Civil Procedure 54(d)(1), to be specified upon entry of judgment.

Disposition