PTAB

IPR2018-00801

ArcelorMittal v. Array Technologies Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Single Axis Solar Tracking System
  • Brief Description: The ’249 patent discloses a linked solar tracker system where a single motor drives multiple rows of solar panels. The system utilizes worm-gear box assemblies at each tracker row, which inherently resist back-driving from external forces like wind, allowing the linked drive shafts to be "minimally constructed."

3. Grounds for Unpatentability

Ground 1: Obviousness over Mackamul and Johnson ’521 - Claims 1, 2, 8-10, and 14 are obvious over Mackamul in view of Johnson ’521.

  • Prior Art Relied Upon: Mackamul (Application # 2006/0044511) and Johnson ’521 (Patent 4,297,521). Petitioner also presents optional combinations with Johnson ’355 (Patent 4,968,355), Sampayo (Patent 5,542,409), and admitted prior art.
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Mackamul taught a single-axis solar tracker with a single drive mechanism for multiple rows, linked drive members, and support structures that transfer external forces to the foundations, thereby reducing forces on the drive mechanism. However, Mackamul disclosed a linear actuator. Johnson ’521 disclosed using a single motor with a worm gear drive to rotate multiple rows of solar collectors via linked shafts. Johnson ’521 also taught using universal joints to connect shafts, accommodating non-linearity. Petitioner contended that combining these references would result in a system meeting the limitations of independent claims 1 and 9, including the worm-gear box, single driving apparatus, and articulating joints. The inherent properties of Johnson ’521’s worm gear would resist back forces, meeting the "minimally constructed" shaft and force-avoidance limitations.
    • Motivation to Combine: A POSITA would combine these references because Mackamul expressly stated that "other drive mechanisms or actuators may be employed." Replacing Mackamul's linear actuator with Johnson ’521’s well-known rotary worm drive would be a simple substitution of one known element for another to achieve the predictable result of rotating solar panels. Petitioner further noted that Johnson ’355 provided additional motivation by teaching that worm drives exhibit superior tracking resolution.
    • Expectation of Success: A POSITA would have a high expectation of success as the combination involved substituting known, compatible components to achieve their expected functions.

Ground 2: Obviousness over Mackamul, Johnson ’521, and Dorian - Claims 5, 6, and 13 are obvious over Mackamul and Johnson ’521 in view of Dorian.

  • Prior Art Relied Upon: Mackamul (Application # 2006/0044511), Johnson ’521 (Patent 4,297,521), and Dorian (Patent 4,223,214).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addressed dependent claims 5, 6, and 13, which required a "harmonic dampener." Petitioner asserted that the base combination of Mackamul and Johnson ’521 provided the underlying solar tracker system. Dorian was introduced because it disclosed using shock absorbers (dampeners) connected between support legs and a solar panel frame to dampen movement caused by wind. Petitioner argued that Mackamul’s structure, with its torque tube and support columns, provided the necessary attachment points for such dampeners.
    • Motivation to Combine: A POSITA would be motivated to add Dorian's dampeners to the base combination to address the well-known problem of wind-induced oscillations in large solar arrays. Applying Dorian's solution for dampening to the Mackamul system was presented as a predictable solution to a known problem to increase system stability.
    • Expectation of Success: A POSITA would have reasonably expected success in adding dampeners, a standard mechanical solution for vibration, to the solar tracker structure.

Ground 3: Obviousness over Mackamul, Johnson ’521, and Appelqvist - Claims 7 and 14 are obvious over Mackamul and Johnson ’521 in view of Appelqvist.

  • Prior Art Relied Upon: Mackamul (Application # 2006/0044511), Johnson ’521 (Patent 4,297,521), and Appelqvist (Patent 7,140,475).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground addressed dependent claims 7 and 14, which added a "brake for resisting motor coast and back forces." The base combination of Mackamul and Johnson ’521 supplied the drive system. Appelqvist was added to teach a brake for a motor drive shaft that automatically engages when the motor is de-energized, explicitly for preventing unintended rotation like back-driving.
    • Motivation to Combine: A POSITA would combine Appelqvist's brake with the base system to solve known problems of positional inaccuracy caused by motor coasting and backlash in the drive train. This would yield the predictable result of better, more precise control of the tracker's position. This motivation, Petitioner argued, was consistent with the prosecution history and general knowledge in the art.
    • Expectation of Success: Integrating a standard motor brake into a motor-driven system was a routine design choice for a POSITA seeking to improve positional accuracy, leading to a high expectation of success.

4. Key Claim Construction Positions

  • "worm-gear box assembly" / "worm-drive gear boxes": Petitioner argued these terms were used interchangeably and, under the broadest reasonable interpretation, meant simply "a worm and worm gear interacting with each other." It was contended that the terms did not necessarily require a physical casing or housing, based on the specification and prosecution history.
  • "minimally constructed": Petitioner proposed this term meant that the drive shaft was designed to withstand only the forces from the driving apparatus, not the external forces (e.g., wind) exerted on the solar panels. This construction was based on specification language stating that the worm-drive's inherent properties eliminate the need for the drive shaft to resist such external forces.
  • "directly mounted to one or more support columns": Petitioner argued this phrase should be interpreted to mean "attached to and supported by the one or more support columns," including indirect support via cross-bars. This position was supported by figures in the ’249 patent that depicted the gearbox mounted on cross-beams between the support columns.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1, 2, 5-10, 13, and 14 of Patent 8,459,249 as unpatentable.