PTAB

IPR2018-01123

General Electric Company v. United Technologies Corporation

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1. Case Identification

2. Patent Overview

  • Title: Geared Turbofan Engine Fan Blade Design
  • Brief Description: The ’368 patent describes a geared turbofan gas turbine engine. The claims are directed to specific numerical ranges for the fan design, including the number of propulsor blades (N), the solidity value (R) of the blades, and the ratio of these two parameters (N/R), which purportedly enhance propulsive efficiency.

3. Grounds for Unpatentability

Ground 1: Claims 1-4 and 8-18 are obvious over Hall in view of the knowledge of a POSITA.

  • Prior Art Relied Upon: Hall (Cesare A. Hall et al., Engine Design Studies for a Silent Aircraft, Journal of Turbomachinery (2007)).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Hall’s “Design C” discloses a two-spool geared turbofan engine that meets the structural limitations of independent claim 1. Hall explicitly discloses an engine with 18 fan blades, which satisfies the claimed limitation of “no more than 20” blades (N). The only elements not explicitly disclosed in Hall are the specific claimed ranges for solidity (R) and the N/R ratio. For dependent claims, Hall discloses a fan pressure ratio (e.g., 1.40 at cruise) that, when accounting for typical low bypass duct losses, would result in a bypass flow passage pressure ratio (BFPPR) within the claimed ranges of claims 2 and 3.
    • Motivation to Combine (for §103 grounds): Petitioner contended that the claimed parameters R and N/R are well-known "result-effective variables" in turbofan engine design. A person of ordinary skill in the art (POSITA), starting with the engine architecture of Hall's Design C, would have been motivated to optimize these known design variables through routine experimentation to achieve desired performance characteristics. The petition argued that simply selecting an optimal or workable range for a known result-effective variable is obvious absent any evidence of unexpected results, which the ’368 patent allegedly fails to provide.
    • Expectation of Success (for §103 grounds): A POSITA would have had a reasonable expectation of success in determining workable ranges for R and N/R. This is because the relationships between blade count, chord dimension, fan diameter, and solidity were well understood, and modern computational fluid dynamics tools allowed for routine optimization of such parameters.

Ground 2: Claims 1-18 are obvious over Daly in view of the knowledge of a POSITA.

  • Prior Art Relied Upon: Daly (Mark Daly, Pratt & Whitney PW1000G, Jane's Aero-Engines (Mar. 2010)).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Daly, which describes the Pratt & Whitney PW1000G geared turbofan engine, discloses all structural elements of independent claim 1. Daly discloses a two-shaft geared turbofan with a 3:1 reduction gearbox and 18 titanium blades for its demonstrator engine, which satisfies the "N is no more than 20" limitation. Similar to the argument against Hall, Daly does not explicitly state values for solidity (R) or the N/R ratio. For dependent claims, Daly discloses a high bypass ratio (10:1 to 13:1), for which a POSITA would have known to target a fan pressure ratio (e.g., 1.3-1.4) that results in a BFPPR within the claimed ranges.
    • Motivation to Combine (for §103 grounds): The motivation argument mirrored that of Ground 1. Given the detailed PW1000G engine described in Daly, a POSITA would have been motivated to select appropriate values for the known result-effective variables of R and N/R to optimize performance. Petitioner argued this amounted to obvious design choice and routine optimization, not invention.
    • Expectation of Success (for §103 grounds): A POSITA would have expected to successfully implement fan blades with the claimed R and N/R characteristics on the Daly engine. The process involved routine engineering calculations and well-established design trade-offs to achieve desired efficiency and performance, all based on known principles.

4. Key Claim Construction Positions

  • "design pressure ratio ... of said bypass flow passage" (BFPPR): Petitioner argued this term, central to claims 2, 3, 6, 7, 13, and 14, should be construed based on its plain meaning and the patent's figures. Specifically, the inlet pressure for the calculation should be measured at the inlet of the fan (station 60 in Fig. 1), not at the inlet of the engine's nacelle as Patent Owner had argued in a related IPR. Petitioner contended the specification does not mention a nacelle, and that the difference in pressure between the fan inlet and nacelle inlet is negligible (0-3%) and would not alter the obviousness analysis.

5. Key Technical Contentions (Beyond Claim Construction)

  • Result-Effective Variables: The central technical pillar of the petition was the argument that the key claimed parameters—number of fan blades (N), tip solidity (R), and the ratio N/R—are all well-known "result-effective variables." Petitioner argued that R is a direct function of blade chord dimension (CD), N, and fan diameter (Dfan), and therefore the N/R ratio is essentially a proxy for the ratio of fan diameter to blade chord dimension. Because the prior art recognized that adjusting these variables affects engine performance (e.g., efficiency, stability), Petitioner contended that finding a workable or optimal range for them, as claimed in the ’368 patent, is merely the result of obvious, routine experimentation, especially since the prior art already disclosed overlapping ranges for these parameters.

6. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 1-18 of the ’368 patent as unpatentable.