PTAB

IPR2018-00801

ArcelorMittal v. Array Technologies, Inc.

Title: Single Axis Solar Tracking System
Brief Description: The ’249 patent discloses a solar tracking system that uses a single driving apparatus to rotate a plurality of linked solar tracker assemblies. The system's key feature is the use of worm-gear box assemblies at each tracker to resist external forces, such as wind, thereby preventing those forces from being transmitted back to the drive shaft and allowing the drive shaft to be "minimally constructed."

Prior Art Relied Upon: Mackamul (Application # 2006/0044511) and Johnson ’521 (Patent 4,297,521), with optional further support from Johnson ’355 (Patent 4,968,355), Sampayo (Patent 5,542,409), and Shingleton (Patent 6,058,930).
Core Argument for this Ground:
- Prior Art Mapping: Petitioner argued that Mackamul, which was not cited during the ’249 patent's prosecution, taught a linked, single-axis solar tracker system with a single drive mechanism. Critically, Mackamul taught reducing forces on its drive mechanism by directly mounting its driving sections to support foundations. However, Mackamul used a linear actuator. Petitioner asserted that Johnson ’521 taught the key missing element: a single motor rotating a drive shaft that uses worm gears to pivot multiple rows of solar collectors.
- Motivation to Combine: A POSITA would combine these references because Mackamul explicitly stated that "other drive mechanisms or actuators may be employed." Petitioner contended that replacing Mackamul's linear actuator with the well-known rotary worm gear drive from Johnson ’521 was a simple substitution of one known element for another to achieve the predictable result of rotating solar collectors.
- Expectation of Success: The combination involved substituting known components to perform their established functions, leading to a high and predictable expectation of success.

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 built upon the combination in Ground 1 to address dependent claims 5, 6, and 13, which add limitations related to a harmonic dampener. Petitioner asserted that Dorian taught the use of dampeners (shock absorbers) connected between a solar panel's support frame and its support legs to dampen wind-induced movement. Mackamul’s structure, with its torsion tube (torque element) and support columns (foundations), allegedly provided the necessary components for attaching such a dampener.
- Motivation to Combine: A POSITA would have been motivated to add Dorian’s dampeners to the base Mackamul/Johnson system to solve the well-known problem of wind-induced oscillations, a particular concern for the type of large solar arrays disclosed in Mackamul. Dorian expressly taught using dampeners for this very purpose.
- Expectation of Success: Applying a known solution (dampeners) to a known problem (wind oscillation) in a known system configuration would yield the predictable result of a more stable solar array.

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 also built on the base combination from Ground 1 to address claims 7 and 14, which add limitations concerning a brake for resisting motor coast and back forces. Petitioner argued that Appelqvist taught a brake for a motor drive shaft specifically intended to remain engaged when the motor is not energized, thereby preventing unintended rotation from back-driving forces.
- Motivation to Combine: A POSITA would combine Appelqvist's brake with the Mackamul/Johnson system to solve the known problem of positional errors in tracking systems caused by motor coasting and back forces. The existence and benefits of motor brakes for providing better control were well-known in the art.
- Expectation of Success: The combination would predictably result in better control of the drive shaft's position and improved overall tracking accuracy.

"worm-gear box assembly": Petitioner proposed this term should be construed broadly to mean an interacting worm and worm-gear, not necessarily requiring a physical housing or casing. This construction was central to mapping prior art that disclosed worm gear mechanisms without always explicitly showing a sealed box.
"minimally constructed": Petitioner argued this term, applied to the drive shaft, means the shaft is constructed to withstand only the driving forces from the motor, not the significant external forces (e.g., wind) that are instead resisted by the worm-gear assembly. This supported the argument that Mackamul's system, which reduces forces on its drive mechanism, met the limitation.
"directly mounted": Petitioner proposed a broad interpretation meaning "attached to and supported by," which would allow for indirect mounting via cross-beams as shown in the ’249 patent's own figures. This was critical for arguing Mackamul’s support structure met the limitation.
"to avoid transmitting...external forces" / "resisting a transmission...": Petitioner construed these phrases to mean that the worm-gear's inherent inefficiency at being back-driven "virtually eliminates" the transmission of external forces, not that it prevents transmission completely. This interpretation aligns with the specification and prosecution history.

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 under 35 U.S.C. §103.