PTAB

IPR2019-00625

Curt Mfg LLC v. Horizon Global Americas Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Microprocessor-based control for trailer brakes
  • Brief Description: The ’352 patent discloses an electronic brake controller for a towed vehicle’s electrically actuated brake system. The controller uses a microcontroller to generate and vary the duty cycle of a pulse-width modulated (PWM) signal, which in turn controls a power switching circuit to deliver a corresponding level of braking current to the trailer's brakes.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 64-67 and 70 by McGrath

  • Prior Art Relied Upon: McGrath (Patent 5,620,236).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that McGrath discloses every limitation of independent claim 64 and its dependent claims 65-67 and 70. Petitioner asserted that McGrath’s microprocessor 45 is the claimed "microcontroller," which is coupled to an input circuit (brake control signal generator 52) and a power switching circuit (brake switching circuit 62). This microprocessor generates a PWM signal (a square wave pulse train) and varies its duty cycle in response to a brake level signal from the input circuit. This action causes the power switching circuit to deliver braking current corresponding to the duty cycle. For the dependent claims, Petitioner argued McGrath discloses the required display circuit (light display 90) coupled to the microprocessor (claim 65), that the display represents the duty cycle (claim 66), that the display includes a plurality of LEDs (claim 67), and that the input circuit includes a decelerometer with an inertia sensor (claim 70).

Ground 2: Obviousness of Claim 1 over McGrath in view of Eccleston

  • Prior Art Relied Upon: McGrath (Patent 5,620,236) and Eccleston (Patent 5,149,176).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that while McGrath discloses most elements of claim 1—including the brake controller, microcontroller, input circuit, display circuit, and power switching circuit—it does not explicitly teach a "current sensing circuit" or using the display to indicate whether the brakes are "properly connected." Petitioner asserted that Eccleston remedies these differences. Eccleston teaches a brake controller with a novel current-sensing technique (sensing voltage drop across a power MOSFET) and an indicator light (LD11) that functions as a "circuit-connection indicator" to show if the trailer brakes are properly connected.
    • Motivation to Combine: Petitioner argued a person of ordinary skill in the art (POSITA) would combine Eccleston’s current sensing and connection indication features into McGrath’s microprocessor-based controller to yield predictable results. The motivation would be to improve the controller by providing real-time feedback on braking current and a visual confirmation of proper connectivity, both known objectives in the art. Critically, Eccleston itself suggested that its analog circuit components, including the lamp driver for the indicator light, "could readily be implemented by microprocessor control," providing an explicit motivation to integrate its features into a system like McGrath's.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success in making the combination. Petitioner argued the integration was a matter of routine engineering, such as connecting a current sensing circuit across the MOSFETs in McGrath’s power switching circuit and feeding the resulting signal to McGrath’s A/D converter. A POSITA would have understood that a commercially available A/D converter with additional inputs could be substituted with a nearly identical footprint, requiring only minor software modifications to the microprocessor to process the new signal and control the indicator lights accordingly.

4. Key Claim Construction Positions

  • Petitioner argued that the term "coupled," used in all challenged claims (1, 64-67, and 70), should be construed to mean "connected directly or indirectly."
  • This construction was asserted to be consistent with the term's plain and ordinary meaning in the art of electronic circuits. Petitioner supported this by noting that a dependent claim in the ’352 patent recites "direct coupling," which would be superfluous if "coupled" did not already encompass indirect connections. This construction is central to the invalidity arguments, as many components in the prior art references are connected indirectly, such as through A/D converters or driver circuits, rather than directly to the microprocessor.

5. Arguments Regarding Discretionary Denial

  • Petitioner acknowledged that a previous inter partes review (IPR) on the ’352 patent, filed by a different party (the "Hopkins Petition"), was denied institution.
  • However, Petitioner argued that its petition should not be denied on similar grounds because it is substantively different and avoids the deficiencies of the prior one. Petitioner contended the Hopkins Petition was denied for procedural failings, namely that it was "little more than a claim chart" that failed to meaningfully tie prior art teachings to the claim limitations. In contrast, this petition provides a detailed element-by-element analysis. Furthermore, Petitioner asserted different and stronger invalidity grounds, such as arguing anticipation of claim 64 by McGrath alone, whereas the Hopkins Petition had argued only obviousness combinations.

6. Relief Requested

  • Petitioner requested the institution of an IPR and the cancellation of claims 1, 64-67, and 70 of Patent 6,068,352 as unpatentable.