PTAB

IPR2018-01442

General Electric Co v. Raytheon Technologies Corp

Key Events

Petition

petition

Title: Geared Turbofan Engine with Specific Power Density
Brief Description: The ’751 patent relates to a geared turbofan gas turbine engine architecture. The invention is defined by specific operational parameters, primarily a "power density" within a claimed numerical range, calculated as the engine's sea level takeoff thrust divided by the volume of its turbine section.

Prior Art Relied Upon: Knip (a 1987 NASA technical report titled Analysis of an Advanced Technology Subsonic Turbofan Incorporating Revolutionary Materials).
Core Argument for this Ground:
- Prior Art Mapping: Petitioner argued that Knip, a study on an advanced geared turbofan engine, disclosed all structural limitations of independent claim 1. This included a fan, compressor, combustor, a fan drive turbine (Low-Pressure Turbine or LPT) with five rotors, a second turbine (High-Pressure Turbine or HPT), and a gearbox. Knip disclosed 23 fan blades, resulting in a fan-blade-to-LPT-rotor ratio of 4.6, which is within the claimed range of 2.5 to 8.5.
- Motivation to Combine: This is a single-reference ground. Petitioner argued a POSITA would have been motivated to calculate the inherent power density of Knip's disclosed engine as part of a standard engineering analysis.
- Expectation of Success: Petitioner asserted that a POSITA could readily calculate the power density from Knip's scaled diagrams and performance data using publicly available software (e.g., GasTurb 9, DataThief, SolidWorks). The calculated power density (between 4.13 and 4.95 lbf/in³) fell within the claimed range of 1.5 to 5.5 lbf/in³. Petitioner further argued the claimed power density is a result-effective variable, making its optimization through routine experimentation obvious.

Prior Art Relied Upon: Knip (a 1987 NASA technical report) and Somanath (Patent 7,632,064).
Core Argument for this Ground:
- Prior Art Mapping: This ground addressed dependent claims requiring a "frame structure" with vanes between the fan drive (LPT) and second (HPT) turbines. Petitioner argued that Knip disclosed a "duct" in this location. Somanath taught that modern turbine engines conventionally include a "mid-turbine bearing frame" with inlet guide vanes at this exact position to provide structural support for bearings and efficiently direct airflow.
- Motivation to Combine: A POSITA would combine these references to improve the efficiency and structural integrity of the advanced engine in Knip. Somanath explicitly described the benefits of such a frame structure with vanes—improving airflow and reducing LPT size—which are well-understood goals in engine design.
- Expectation of Success: The combination involved implementing a conventional, well-known component (the mid-turbine frame with vanes from Somanath) into its known location within a standard engine architecture (disclosed in Knip) to achieve its expected function, presenting a high expectation of success.

Prior Art Relied Upon: Gliebe (a 2003 NASA study titled Ultra-High Bypass Engine Aeroacoustic Study).
Core Argument for this Ground:
- Prior Art Mapping: Petitioner contended that Gliebe, which studied two geared turbofan engine designs, disclosed every element of the claims. Gliebe disclosed engine designs with a sea level takeoff thrust of 61,500 lbf and provided scaled cross-sectional diagrams. Using the same methodology as applied to Knip, Petitioner calculated turbine volumes that yielded power densities of 4.62 and 3.67 lbf/in³, both squarely within the claimed range. Gliebe also disclosed 22 fan blades and LPTs with 5 and 6 rotors, yielding ratios (4.4 and 3.67) within the claimed range. Dependent claim 2 (3-6 LPT stages) and independent claim 15 (gear reduction) were also explicitly taught.
Additional Grounds: Petitioner asserted additional obviousness challenges, including claims 3, 9, and 16 over Knip in view of Decker (Application # 2006/0228206) for teaching a reduced fan blade count, and claim 23 over Gliebe in view of Somanath for adding a mid-turbine frame. An alternative obviousness ground over Gliebe was also presented.

"frame structure": Petitioner argued this term, which does not appear in the specification, should be construed as the "mid turbine frame" disclosed in the patent. This construction aligns the claim with conventional engine components, like that shown in Somanath, located between the high and low-pressure turbines.
"volume of the turbine section...measured...to an exit of a last rotating airfoil stage": Petitioner contended this language requires the volume measurement to terminate at the last rotating blade, explicitly excluding any subsequent stationary vanes. This construction was critical to Petitioner's power density calculations for both the Knip and Gliebe references.

Calculability from Prior Art Diagrams: A central contention was that a POSITA would find it obvious to derive the claimed power density ratio from prior art references like Knip and Gliebe, even if the ratio was not explicitly stated. Petitioner argued that the provided scaled diagrams and performance data were sufficient for a POSITA to calculate the turbine volume and thrust using standard, publicly available engineering software (DataThief, SolidWorks, GasTurb 9), and that such calculations are routine in the field.
Result-Effective Variables: Petitioner argued that the claimed parameters—specifically power density and the ratio of fan blades to turbine rotors—are "result-effective variables." It was well-known that decreasing turbine volume or reducing fan blade count affects engine performance (e.g., weight, efficiency). Therefore, optimizing these known variables to arrive at the claimed ranges would have been routine experimentation for a POSITA, not an inventive step.

Petitioner requested the institution of an inter partes review and the cancellation of claims 1-4, 9-10, 15-16, and 23 of Patent 9,695,751 as unpatentable.