DCT
1:25-cv-01561
Reabe Design LLC v. Reabe Aircraft Improvement Inc
Key Events
Complaint
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Reabe Design LLC (Wyoming), Reabe Aircraft Products, LLC (Wyoming), and Troy Reabe (Wisconsin)
- Defendant: Reabe Aircraft Improvement Inc. (Wisconsin) and Jeff Reabe (Wisconsin)
- Plaintiff’s Counsel: Amundsen Davis LLC
- Case Identification: 1:25-cv-01561, E.D. Wis., 10/13/2025
- Venue Allegations: Venue is alleged to be proper as Defendants are residents of De Pere, Wisconsin, within the Eastern District of Wisconsin, and because a substantial part of the events giving rise to the claims allegedly occurred in the district.
- Core Dispute: Plaintiffs allege that Defendants’ aircraft hopper gauge systems infringe a patent related to liquid quantity measurement technology following the termination of a long-standing business relationship and oral license between the parties.
- Technical Context: The technology concerns systems for accurately measuring the quantity of liquid agricultural products in irregularly shaped aircraft tanks, a critical function for the safe and effective operation of crop-dusting aircraft.
- Key Procedural History: The complaint alleges a prior, long-term oral business relationship (c. 2009-2024) where Plaintiffs designed and manufactured a "Hopper Gauge Product" and Defendants acted as the sales entity. Plaintiffs allege this relationship included an oral license to their intellectual property, which was explicitly terminated via a letter on September 25, 2024. The infringement allegations are limited to conduct occurring after this termination date.
Case Timeline
| Date | Event |
|---|---|
| 2009-11-19 | Priority Date for U.S. Patent No. 8,450,998 |
| 2013-05-28 | U.S. Patent No. 8,450,998 Issued |
| 2024-09-25 | Plaintiffs' letter terminating the alleged oral license and business relationship |
| 2025-10-13 | Complaint Filed |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 8,450,998 - "Digital Quantity Gauge for an Agricultural Aircraft Payload Hopper Using a Magnetostrictive Linear Displacement Transducer (MLDT)"
- Patent Identification: U.S. Patent No. 8,450,998, “Digital Quantity Gauge for an Agricultural Aircraft Payload Hopper Using a Magnetostrictive Linear Displacement Transducer (MLDT),” issued May 28, 2013.
The Invention Explained
- Problem Addressed: The patent’s background section describes the difficulty in obtaining a reliable indication of the quantity of liquid agricultural product in an aircraft’s hopper tank (’998 Patent, col. 3:20-30). Such tanks often have irregular shapes, and the liquid is subject to sloshing and dynamic forces during flight maneuvers, making simple level-sensing inaccurate and unreliable (’998 Patent, col. 3:37-45).
- The Patented Solution: The invention uses an elongated magnetostrictive linear displacement transducer (MLDT) tube placed vertically within the tank. A float containing a permanent magnet moves up and down the tube with the liquid level. The MLDT senses the precise position of the magnet and generates a signal corresponding to the liquid’s height. This height signal is then processed by “converter means,” which filters out oscillations from sloshing and converts the linear height measurement into a volume or quantity measurement for display to the pilot (’998 Patent, Abstract; col. 4:4-7).
- Technical Importance: This approach provided a more precise and reliable quantity measurement compared to prior mechanical systems, which were prone to wear and resolution loss, or less accurate electronic systems (’998 Patent, col. 5:6-14).
Key Claims at a Glance
- The complaint asserts independent claim 1 and reserves the right to assert other claims (Compl. ¶83).
- Independent Claim 1:
- A system for determining the quantity of a liquid agricultural product... from a tank in an airplane comprising:
- a payload storage tank for holding the agricultural product;
- an elongated magnetostrictive linear displacement transducer tube located vertically in the aircraft payload storage tank;
- a probe float slidably coupled to move up or down on the elongated magnetostrictive linear displacement transducer tube;
- a permanent magnet coupled to the probe float wherein the position of the magnet is sensed by the... transducer tube which generates a signal that marks the level of the liquid...; and
- converter means coupled to convert the generated signal that marks the level of the liquid... to a quantity of liquid in the aircraft payload storage tank.
III. The Accused Instrumentality
Product Identification
- The "Accused Products" are identified as the "Hopper Gauge Product" and "Knock-Off Hopper Gauge Products" that Defendants have allegedly continued to sell after September 25, 2024 (Compl. ¶67, ¶72).
Functionality and Market Context
- The complaint alleges the Accused Products are systems for determining the quantity of liquid in an aircraft tank (Compl. ¶48). They are sold as kits that include components such as a quantity probe, a probe float with a magnet, and a main display (Compl. ¶54). The complaint alleges these products are sold using the same part numbers as the products Plaintiffs previously manufactured and represent that they are compliant with Federal Aviation Administration ("FAA") supplemental type certificates ("STC") (Compl. ¶74).
- The complaint alleges that some of the accused "Knock-Off Hopper Gauge Products" are not STC compliant and do not function correctly when combined with Plaintiffs' components (Compl. ¶75-¶76).
IV. Analysis of Infringement Allegations
No probative visual evidence provided in complaint.
- Claim Chart Summary: The complaint alleges that each Accused Product sold since September 25, 2024, includes components that meet the limitations of at least claim 1 of the ’998 Patent (Compl. ¶84).
U.S. Patent No. 8,450,998 Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a payload storage tank for holding the agricultural product | The complaint alleges infringement in the context of a system that includes an aircraft payload storage tank where the other components are installed. | ¶84 | col. 4:31-34 |
| an elongated magnetostrictive linear displacement transducer tube located vertically in the aircraft payload storage tank | The Accused Products allegedly include this component as part of the system for measuring liquid levels. | ¶84 | col. 3:58-62 |
| a probe float slidably coupled to move up or down on the elongated magnetostrictive linear displacement transducer tube | The Accused Products allegedly include a probe float designed to slide along the transducer tube. | ¶84 | col. 3:62-64 |
| a permanent magnet coupled to the probe float wherein the position of the magnet is sensed by the... transducer tube which generates a signal that marks the level of the liquid... | The Accused Products allegedly use a magnet in the float, whose position is sensed by the transducer to generate a signal indicating the liquid level. | ¶84 | col. 3:65-col. 4:2 |
| converter means coupled to convert the generated signal that marks the level of the liquid... to a quantity of liquid in the aircraft payload storage tank | The Accused Products allegedly include converter means that convert the level signal into a final quantity measurement. | ¶84 | col. 4:4-7 |
- Identified Points of Contention:
- Factual Question: A primary question will be evidentiary: do the "Accused Products," particularly the alleged "Knock-Off" versions, in fact contain components that meet each limitation of claim 1? The complaint’s infringement allegations are largely conclusory and track the claim language, suggesting that discovery will be needed to establish the precise structure and operation of the accused systems.
- Scope Questions: The dispute may raise questions about the scope of the claims relative to the accused technology. For instance, what is the required structure for the "converter means," and does the accused system’s processing unit fall within that scope?
V. Key Claim Terms for Construction
- The Term: "converter means"
- Context and Importance: This term appears in the final limitation of independent claim 1 and recites the function of converting the raw level signal into a usable quantity of liquid. As a means-plus-function term under 35 U.S.C. § 112(f), its scope is limited to the corresponding structure described in the patent's specification and equivalents thereof. The construction of this term will be critical to determining whether the accused products’ processing electronics constitute an infringing structure.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: A party might argue that the term should encompass any electronic circuit capable of performing the recited function of converting a height signal to a quantity. The claim language itself is broad, and the specification describes the function generally as receiving a signal and converting it to a "tank quantity" (’998 Patent, col. 4:24-28).
- Evidence for a Narrower Interpretation: A party could argue the term is limited to the specific structures disclosed, such as the combination of "Filtering electronics 18" and "Converter electronics 20" working in concert (’998 Patent, col. 4:18-28; Fig. 2). The specification further describes specific filter types (e.g., resistor-capacitor circuit) and the use of a "map function which scales the analog input signal to a quantity of fluid" (’998 Patent, col. 4:51-54; col. 5:1-3), which could be argued as necessary structural components.
VI. Other Allegations
- Indirect Infringement: The complaint alleges both inducement and contributory infringement of claim 1 (Compl. ¶89-90).
- Inducement: The allegation is based on Defendants providing customers with instructions (a copy of the STC or directions to download instructions) on how to install the Hopper Gauge Product, thereby allegedly instructing them to assemble the infringing system (Compl. ¶88, ¶90).
- Contributory Infringement: This is based on the allegation that the components listed are "especially made or especially adapted for use" in the patented system and are not a "staple article or commodity of commerce suitable for substantial non-infringing use" (Compl. ¶85-86).
- Willful Infringement: The willfulness allegation is based on Defendants’ alleged knowledge of the ’998 Patent, which stems from the parties' prior business relationship and the explicit termination of the license on September 25, 2024. The complaint alleges that continued sales after this date constitute willful infringement (Compl. ¶91).
VII. Analyst’s Conclusion: Key Questions for the Case
- A central issue will be the enforceability of the patent against the Defendants: does the alleged history of an oral license and its subsequent termination on September 25, 2024, create a clear line after which Defendants' sales became unauthorized acts of infringement? The resolution of this question may depend on state contract law principles regarding the existence and termination of the alleged license.
- A key evidentiary question will be one of technical identity: do the "Accused Products" sold by Defendants after the termination date, particularly any "Knock-Off" versions sourced from third parties, actually incorporate the specific technology required by each element of claim 1 of the ’998 patent?
- The case may also turn on a question of claim construction: is the scope of the term "converter means" limited to the specific electronic filtering and mapping circuits described in the specification, or can it be construed more broadly to cover other processing units that perform a similar function?