Oxygenator Water Tech Inc v. Tennant Co

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Oxygenator Water Technologies, Inc. (Minnesota)
  • Defendant: Tennant Company (Minnesota)
  • Plaintiff’s Counsel: Carlson, Caspers, Vandenburgh & Lindquist, P.A.
• Case Identification: 0:20-cv-00358, D. Minn., 05/08/2020
• Venue Allegations: Venue is alleged to be proper in the District of Minnesota as Defendant resides in the district, has committed alleged acts of infringement there, and maintains a regular and established place of business in the district.
• Core Dispute: Plaintiff alleges that Defendant’s commercial floor scrubbers, which incorporate its "ec-H2O" technology, infringe three reissue patents related to the electrolytic generation of micro- and nanobubbles in flowing water.
• Technical Context: The technology concerns using electrolysis in a flow-through device to create extremely small, stable oxygen bubbles in water, which is marketed as a chemical-free cleaning solution for industrial and commercial applications.
• Key Procedural History: The complaint alleges a history of pre-suit interactions, including Defendant’s 2007 patent application that allegedly referenced a parent patent to the patents-in-suit. It also describes licensing discussions between the parties in 2010, which did not result in an agreement. The patents-in-suit are all reissues of U.S. Patent No. 7,670,495, a fact that may introduce the potential for an intervening rights defense under 35 U.S.C. § 252.

Case Timeline

Date	Event
2002-02-22	Earliest Priority Date for '415, '092, and '665 Patents
2007-01-01	Tennant files patent application allegedly referencing OWT technology
2008-01-01	Tennant introduces ec-H2O™ electrolysis modules
2008-08-08	Rights to patents-in-suit assigned to OWT
2010-07-27	OWT and Tennant meet to discuss potential license
2010-09-02	Tennant declines to bid on OWT's technology
2015-03-17	U.S. Patent No. RE45,415 Issues
2018-10-23	U.S. Patent No. RE47,092 Issues
2019-09-20	OWT sends notice letter to Tennant regarding infringement
2019-10-29	U.S. Patent No. RE47,665 Issues
2020-05-08	First Amended Complaint Filed

II. Technology and Patent(s)-in-Suit Analysis

U.S. Reissue Patent No. RE45,415 - “Flow-Through Oxygenator”

• Issued: March 17, 2015.

The Invention Explained

• Problem Addressed: The patent addresses the difficulty of efficiently increasing and maintaining high levels of dissolved oxygen in water. Conventional methods like sparging are inefficient because large bubbles escape quickly, while prior electrolytic methods often require high power and create harsh chemical environments unsuitable for biological applications ('415 Patent, col. 1:30-44, col. 2:4-11).
• The Patented Solution: The invention is an electrolytic cell, or "oxygen emitter," that uses a specific, "critical distance" between the anode and cathode (0.005 to 0.140 inches) to generate extremely small oxygen microbubbles and nanobubbles. These bubbles are so small they remain suspended in the water, creating a stable, supersaturated solution at low voltage. The patent particularly describes a flow-through model for treating moving water ('415 Patent, Abstract; col. 3:9-42).
• Technical Importance: This approach provided a method for creating supersaturated water in a portable, low-voltage, and quiet manner, making it suitable for sensitive applications like aquaculture and for in-line water treatment ('415 Patent, col. 2:50-54).

Key Claims at a Glance

• The complaint asserts independent method claim 13 (Compl. ¶35).
• The essential elements of Claim 13 include:
  • Flowing water at a rate no greater than 12 gallons per minute through an electrolysis emitter contained in a tubular housing.
  • Causing electricity to flow between an anode and cathode.
  • Producing a suspension of oxygen microbubbles and nanobubbles with a diameter less than 50 microns.
  • The anode and cathode are separated by a "critical distance" of 0.005 to 0.140 inches.
  • The power source provides a voltage no greater than about 28.3 volts and amperage no greater than about 13 amps.
  • The water has conductivity sufficient to support plant or animal life.
• The complaint reserves the right to assert other claims but focuses its allegations on claim 13.

U.S. Reissue Patent No. RE47,092 - “Flow-Through Oxygenator”

• Issued: October 23, 2018.

The Invention Explained

• Problem Addressed: The patent addresses the same problems as the ’415 Patent regarding the inefficient oxygenation of water ('092 Patent, col. 2:1-25).
• The Patented Solution: This patent refines the flow-through oxygenator concept by claiming a specific geometric arrangement of electrodes within the tubular housing. The electrodes are positioned away from the center of the housing, closer to the interior walls. This configuration creates an unobstructed central passageway for water flow, which is critical for efficient in-line applications, while still maintaining the "critical distance" between electrodes required for microbubble generation ('092 Patent, Abstract; col. 17:11-47).
• Technical Importance: The invention optimizes the emitter's design for flow-through systems by minimizing flow obstruction, a key consideration for its integration into devices like industrial scrubbers or irrigation systems ('092 Patent, col. 3:3-8).

Key Claims at a Glance

• The complaint asserts independent method claim 13 (Compl. ¶86).
• The essential elements of Claim 13 include:
  • Providing a flow-through oxygenator with an emitter in a tubular housing.
  • The electrodes are separated by 0.005 to 0.140 inches.
  • A key geometric limitation: each electrode is positioned so that "substantially all points midway between all opposing electrodes are closer to a surface of the tubular housing than to a center point," allowing some water to flow without passing between the electrodes.
  • A power source delivers a voltage ≤ 28.3 volts and a current ≤ 12.8 amps.
  • Passing water through the housing while applying current to produce oxygen via electrolysis.
• The complaint’s allegations for the ’092 Patent are focused on claim 13.

U.S. Reissue Patent No. RE47,665 - “Flow-Through Oxygenator”

• Issued: October 29, 2019.
• Technology Synopsis: The ’665 Patent claims an apparatus (an "emitter") rather than a method. It protects the physical device embodying the same core technology as the ’092 Patent. The invention is an emitter for electrolytic generation of oxygen bubbles, defined by the specific geometric positioning of electrodes within a tubular housing such that they are closer to the housing surface than to the center, creating an unobstructed central flow path while maintaining the critical electrode separation distance (’665 Patent, Abstract; col. 17:21-65).
• Asserted Claims: The complaint asserts independent apparatus claim 13 (Compl. ¶110).
• Accused Features: The complaint alleges that Tennant’s "cylindrical electrode products," specifically the "cylindrical electrolysis modules" and the floor scrubbers containing them, are infringing emitters (Compl. ¶109-110).

III. The Accused Instrumentality

• Product Identification: The accused instrumentalities are Tennant’s commercial floor scrubbers incorporating its "ec-H2O™" and "ec-H2O NanoClean®" technologies (Compl. ¶13, 16, 63). The complaint identifies two specific infringing components within these systems: "cylindrical electrode products" and "plate electrode products" (Compl. ¶17, 21).
• Functionality and Market Context:
  • The accused modules are described as using electrolysis to "transform tap water into a safe, effective cleaning solution" by generating "millions of tiny microscopic bubbles" that enable cleaning without chemical detergents (Compl. ¶13, 16). The complaint provides detailed photographic evidence of two distinct physical designs: a cylindrical module with concentrically nested mesh electrodes and a plate-based module with parallel plate electrodes inside a rectangular housing (Compl. ¶18, 21, 43, 66). An annotated diagram shows the flow of water through the system, where an "electric charge" is applied in an "oxygenation chamber" to create the cleaning solution (Compl. ¶38, p. 15).
  • The complaint alleges that the ec-H2O technology is a key market differentiator for Tennant, allowing it to command a 10-20% price premium and to have achieved over $1 billion in sales of equipment containing the technology (Compl. ¶14, 15).

IV. Analysis of Infringement Allegations

RE45,415 Infringement Allegations

Claim Element (from Independent Claim 13)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
flowing water at a flow rate no greater than 12 gallons per minute through an electrolysis emitter...	The accused T3 floor scrubber operates at 0.12-0.25 gpm, and the T350 at 0.12-0.35 gpm, both below the claimed maximum.	¶39, ¶64	col. 16:21-23
...comprising an electrical power source electrically connected to an anode electrode and a cathode electrode contained in a tubular housing,	The accused modules contain an "ec-H2O CONTROL BOARD" (power source) electrically connected to anode and cathode electrodes, which are housed inside the module. A provided electrical diagram shows this connection.	¶40, ¶65	col. 5:26-39
producing the composition comprising a suspension comprising oxygen microbubbles and nanobubbles in the water, the microbubbles and nanobubbles having a bubble diameter of less than 50 microns...	Tennant's marketing materials state the technology creates "Oxygenated Micro Bubbles" and "nanobubbles."	¶42, ¶63, ¶68	col. 16:28-32
...the anode electrode is separated at a critical distance from the cathode such that the critical distance is from 0.005 inches to 0.140 inches;	Photographic evidence with a caliper purports to show the spacer separating the electrodes is ~0.095 inches thick for the cylindrical product and the frame is ~0.138 inches for the plate product, both within the claimed range.	¶43-45, ¶69-30	col. 16:33-36
...the power source produces a voltage no greater than about 28.3 volts and an amperage no greater than about 13 amps...	Electrical diagrams show a 24 VDC input and a 10-amp fuse, and the complaint alleges on information and belief that the output is within the claimed voltage and amperage limits.	¶46, ¶70	col. 16:37-39
...the water flowing into the inlet has a conductivity produced by the presence of dissolved solids such that the water supports plant or animal life.	The operator manual states that "normal water" passes through the module, which is alleged to have the requisite conductivity.	¶48, ¶72	col. 16:44-47

RE47,092 Infringement Allegations

Claim Element (from Independent Claim 13)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
providing a flow-through oxygenator comprising an emitter for electrolytic generation of bubbles of oxygen...	The accused cylindrical electrolysis modules are alleged to be flow-through oxygenators that use electrolysis to treat water.	¶88	col. 17:11-14
a tubular housing having a water inlet, a water outlet, and a longitudinal water flow axis...	An exploded parts diagram of the accused module shows a tubular housing for the electrode with a clear inlet, outlet, and longitudinal flow axis.	¶89, Ex. D at 68	col. 17:15-17
at least two electrodes... opposing and separated from the second electrode by a distance of between 0.005 inches to 0.140 inches...	A photograph with a caliper measures the spacer creating the separation distance at ~0.095 inches, which is within the claimed range.	¶90-93	col. 17:20-24
each electrode... is positioned so that substantially all points midway between all opposing electrodes are closer to a surface of the tubular housing than to a center point...	A photograph with annotated circles purports to demonstrate this specific geometric relationship in the accused cylindrical electrode. It also shows a water flow path that does not pass between the electrodes.	¶94-95, p.41	col. 17:25-36
a power source... configured to deliver a voltage... less than or equal to 28.3 volts... and a current... less than or equal to 12.8 amps;	An electrical diagram shows a 24 VDC input and a 10-amp fuse, which is alleged to result in power delivery within the claimed limits.	¶96	col. 17:37-43

Identified Points of Contention

• Scope Questions: A question for the court may be whether the term "tubular housing", as used across the patents, can be interpreted to read on the rectangular, box-like housing of the accused "plate electrode products" (Compl. ¶66, p.28). Further, for the ’415 Patent, a dispute may arise over whether tap water used for floor cleaning meets the limitation of being water that "supports plant or animal life," a phrase that, in the context of the patent's specification, relates to biological applications like hydroponics and aquaculture.
• Technical Questions: The infringement allegation for the geometric limitation in the ’092 and ’665 Patents relies heavily on an annotated photograph (Compl. ¶95, p.41). A technical question for the court will be whether this evidence is sufficient to prove that "substantially all points" midway between the electrodes satisfy the specific spatial relationship to the housing surface and center point as required by the claims.

V. Key Claim Terms for Construction

• The Term: "tubular housing" (asserted in all three patents)

• Context and Importance: This term's construction is critical because the complaint accuses both a "cylindrical electrode" in a cylindrical housing and a "plate electrode" in a distinctly rectangular housing (Compl. ¶66). Whether the rectangular housing of the plate electrode products falls within the scope of "tubular housing" will be a central issue for infringement of those products.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The specifications are not explicitly limited to circular tubes. The patents disclose alternative embodiments that are not strictly cylindrical, such as a "funnel or pyramid" shape and a "multilayer sandwich" design, which may suggest that "tubular" was intended to mean any conduit for fluid flow, regardless of cross-sectional shape ('415 Patent, FIG. 4, FIG. 5A).
  • Evidence for a Narrower Interpretation: The primary flow-through embodiment depicted in the patents has a circular cross-section ('415 Patent, FIG. 7A). A party might argue that the ordinary meaning of "tubular" implies a round or cylindrical shape and that the alternative embodiments are distinct exceptions that do not broaden the general term.

• The Term: "each electrode ... is positioned so that substantially all points midway between all opposing electrodes are closer to a surface of the tubular housing than to a center point" ('092 Patent, Claim 13)

• Context and Importance: This complex geometric limitation is a key distinguishing feature of the '092 and '665 patents. Its precise definition will determine whether the accused cylindrical modules, which feature nested concentric electrodes, infringe these later patents. Practitioners may focus on this term because it appears to have been added during prosecution to define the invention over prior art.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The patent claims require this condition for "substantially all points," which provides some flexibility and does not require mathematical perfection at every point along the electrodes. The claim language is supported by Figure 7A, which shows electrodes placed against the inner wall of a circular housing, clearly away from the center.
  • Evidence for a Narrower Interpretation: The term "center point" could be a focus of dispute. In a cylindrical housing, it is unambiguous, but its application to other shapes could be contested. A defendant may argue for a strict interpretation of "substantially all," requiring the condition to be met along the entire active length of the electrodes in a way the accused products do not.

VI. Other Allegations

• Indirect Infringement: The complaint alleges induced infringement based on Defendant’s product literature, marketing materials, and operator manuals, which allegedly instruct customers to use the ec-H2O system in a manner that directly infringes the asserted method claims (Compl. ¶55, 80, 104). A specific instruction cited is to "Press the ec-H2O system switch to the on (I) position" (Compl. ¶55). Contributory infringement is alleged on the basis that the electrolysis modules are not staple articles of commerce and are especially made for an infringing use (Compl. ¶54, 79).
• Willful Infringement: Willfulness is alleged based on Defendant's purported pre-suit knowledge of the patented technology. The complaint points to a 2007 Tennant patent application that allegedly cited a parent to the patents-in-suit, as well as licensing negotiations that occurred between the parties in 2010 (Compl. ¶23-31, 129). The complaint further alleges Tennant received a notice letter on September 20, 2019, putting it on notice of at least the '415 and '092 patents before the '665 patent had issued (Compl. ¶53).

VII. Analyst’s Conclusion: Key Questions for the Case

• A core issue will be one of definitional scope: can the term "tubular housing", described in the patent’s primary embodiments as cylindrical, be construed to cover the rectangular, box-like housing of the accused "plate electrode" products? This claim construction dispute will be determinative for a significant portion of the accused sales.
• A key legal question will be the applicability of an intervening rights defense: as all patents-in-suit are reissues, the case may turn on whether the asserted claims are substantively identical to the original patent's claims. If they are not, Defendant may be shielded from damages for infringing conduct that occurred before the patents were reissued.
• A central evidentiary question will be one of geometric proof: does the complaint's annotated photographic evidence (Compl. ¶95) suffice to prove, by a preponderance of the evidence, that the accused cylindrical electrodes meet the highly specific spatial and geometric limitations required by the asserted claims of the '092 and '665 patents?