Neuralpulse Ltd v. Water Pik Inc

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Neuralpulse Ltd. (New York) and LuminaThrive LLC (Texas)
  • Defendant: Water Pik, Inc (Colorado)
  • Plaintiff’s Counsel: Glacier Law LLP
• Case Identification: 1:25-cv-01479, D. Colo., 05/10/2025
• Venue Allegations: Venue is asserted in the District of Colorado on the basis that Defendant Water Pik, Inc. is a resident of the judicial district.
• Core Dispute: Plaintiffs seek a declaratory judgment that their water dental flosser products do not infringe Defendant’s patent for an oral irrigator with a massage mode, and that the patent is invalid.
• Technical Context: The technology involves electronic control systems for oral irrigators that enable distinct operational modes, such as a standard cleaning mode and a gum massage mode, by altering the electrical signal sent to the device's motor.
• Key Procedural History: The action was precipitated by infringement reports Defendant allegedly submitted to Amazon.com against Plaintiffs' products. Plaintiffs also assert that the patentee narrowed the scope of the patent's claims during prosecution to add the term "constant voltage" to overcome prior art, potentially creating a prosecution history estoppel that would limit the scope of equivalents.

Case Timeline

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

U.S. Patent No. 9,642,677 - "ORAL IRRIGATOR WITH MASSAGE MODE"

• Patent Identification: U.S. Patent No. 9,642,677, issued May 9, 2017.

The Invention Explained

• Problem Addressed: The patent's background section notes that the pressure level in typical oral irrigators is determined by fixed mechanical characteristics and is not easily varied based on user preferences, which may be complicated to manufacture (’677 Patent, col. 1:11-20).
• The Patented Solution: The invention is an irrigating device with at least two distinct operational modes: a "normal mode" and a "massage mode." A processing element provides different control signals to the motor for each mode. In the normal mode, a "constant voltage" signal is supplied, while in the massage mode, a signal with a "voltage varying in at least one of magnitude or frequency" is supplied, resulting in different fluid pulse rates and pressures at the tip (’677 Patent, Abstract; col. 10:25-45).
• Technical Importance: The invention describes a method for providing users with distinct, electronically-controlled operational modes in a single device, moving beyond fixed mechanical outputs to offer a customized experience such as gum massage (’677 Patent, col. 3:21-28).

Key Claims at a Glance

• The complaint focuses on independent claim 1 and notes that independent claims 6, 16, and 20 are substantially similar (Compl. ¶27, ¶38).
• Independent Claim 1:
  • An oral irrigator comprising: a reservoir, a handle with a tip, a pump, and a motor.
  • A processing element in communication with the motor.
  • Wherein upon receiving a user input, the processing element provides either a first control signal or a second control signal to the motor.
  • The first control signal supplies a constant voltage to the motor.
  • The second control signal supplies a voltage varying in at least one of magnitude or frequency.
• The complaint does not explicitly reserve the right to assert dependent claims but seeks a declaration of non-infringement for all claims of the ’677 Patent (Compl. ¶26).

III. The Accused Instrumentality

Product Identification

• The "Water Dental Flosser" sold by Plaintiffs Neuralpulse and LuminaThrive on Amazon.com (Compl. ¶14). The product listing is shown in a screenshot provided in the complaint. (Compl. ¶14, p. 4).

Functionality and Market Context

• The accused product is a portable oral irrigator with four selectable operating modes: Low, Medium, High, and Pulse (Compl. ¶28).
• The complaint alleges that all four of these modes are driven by fixed-frequency Pulse Width Modulated (PWM) signals, where the output effect is varied by changing the signal's duty cycle (the percentage of time the signal is "on") (Compl. ¶28).
• Plaintiffs allege their product has a strong market presence, holding a "#1 Best Seller" rank in its category on Amazon (Compl. ¶14).

IV. Analysis of Infringement Allegations

’677 Patent Infringement Allegations

• Identified Points of Contention:
  • Scope Questions: The primary dispute revolves around the interpretation of "constant voltage." Does the term, as used in the patent, require a true, continuous direct current (DC) signal, or could it be construed to encompass a high-frequency PWM signal that delivers a constant average power? The complaint argues for the former, narrow interpretation (Compl. ¶27).
  • Technical Questions: Does the accused product's use of PWM signals with varying duty cycles for its "Low," "Medium," and "High" modes produce an output that is technically and functionally different from the "constant-voltage" normal mode described in the patent? The complaint provides oscilloscope traces showing the PWM signals for the accused device's various modes to support its argument of a fundamental operational difference (Compl. p. 7).
  • Prosecution History Estoppel: The complaint raises the question of whether the patentee, by adding the "constant voltage" limitation during prosecution to distinguish prior art, surrendered the right to claim that a PWM signal is an equivalent under the doctrine of equivalents (Compl. ¶32).

V. Key Claim Terms for Construction

• The Term: "constant voltage"
• Context and Importance: The determination of infringement or non-infringement hinges almost entirely on the construction of this term. Plaintiffs' core argument is that their device, which uses PWM signals in all modes, never supplies a "constant voltage" as required by the claim (Compl. ¶29, ¶30). Practitioners may focus on this term because its definition dictates whether the accused device's fundamental control method falls within the scope of the patent's "normal mode."
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The patent describes the normal mode signal as "substantially constant" (col. 10:31-32), which a defendant might argue allows for minor fluctuations inherent in certain signal types that achieve a constant effect.
  • Evidence for a Narrower Interpretation: The patent repeatedly contrasts the "constant voltage" of the normal mode with a "varying" voltage for the massage mode (Claim 1; col. 18:57-61). The complaint argues the patent explicitly links the "constant voltage" signal to the pressure graph in Figure 9A, which depicts a uniform, uninterrupted, high-frequency pressure stream, a result Plaintiffs claim their PWM-driven device does not and cannot produce (Compl. ¶29, ¶35). The complaint also points to the patentee's alleged amendment during prosecution to add this term, suggesting it was a deliberate choice to narrow the claim scope (Compl. ¶32).

VI. Other Allegations

• Indirect Infringement: The complaint addresses the doctrine of equivalents, arguing that the accused device does not infringe under this doctrine. It asserts that prosecution history estoppel bars the patentee from claiming that the accused device's PWM signal is equivalent to the claimed "constant voltage," alleging the patentee surrendered this scope to gain allowance of the patent (Compl. ¶32).

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

This declaratory judgment action appears to center on a focused, technical dispute over claim scope. The resolution of the case will likely depend on the court's answers to two primary questions:

1. A core issue will be one of definitional scope: Will the term "constant voltage" be construed narrowly to mean a continuous, non-pulsed DC signal, as Plaintiffs argue, or can it be interpreted more broadly to cover a Pulse Width Modulated (PWM) signal that delivers a constant average power output?
2. A key legal question will be one of prosecution history: Did the patentee, by adding the "constant voltage" limitation to the claims during prosecution, surrender any claim to PWM-based systems as equivalents for the "normal" operating mode, thereby barring an infringement argument under the doctrine of equivalents?