PTAB

IPR2025-01438

Harbor Freight Tools USA Inc v. Champion Power Equipment Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Fuel Selector for Dual Fuel Generator
  • Brief Description: The ’390 patent discloses a fuel selector for a dual fuel generator designed to prevent the simultaneous flow of two different fuels to the engine. The system uses a sliding "selector switch" that physically interlocks with valve assemblies, ensuring only one fuel valve can be opened at a time.

3. Grounds for Unpatentability

Ground 1: Obviousness of Claims 1-21 over DuroMax, DeVries, Nakafushi, and Olmr

  • Prior Art Relied Upon: DuroMax (Duro Max XP4400EH Operator’s Manual), DeVries (Patent 7,481,087), Nakafushi (JPS61283734A), and Olmr (Patent 5,301,644).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the combination of these references taught every element of the challenged claims. DuroMax disclosed a basic dual fuel generator with separate, non-interlocked valves for gasoline and LPG. DeVries taught a safety key-interlock system for valve assemblies to prevent the dangerous situation of having two valves open simultaneously. Nakafushi addressed the problem of residual gasoline in a carburetor when switching to LPG by using a control valve, and Olmr specified that such a control valve could be a solenoid valve.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSA) would combine DuroMax and DeVries to improve the safety of a standard dual fuel generator by preventing the simultaneous flow of fuels, a known hazard. A POSA would further incorporate the teachings of Nakafushi and Olmr to solve the well-known problem of unsteady performance and over-rich fuel mixtures caused by leftover gasoline in the carburetor after switching to LPG. This would be achieved by adding a carburetor shutoff solenoid (Olmr) controlled by the fuel selection mechanism (Nakafushi).
    • Expectation of Success: A POSA would have a reasonable expectation of success, as combining a mechanical interlock with a dual fuel system and adding a standard carburetor solenoid were all well-understood technologies used for their predictable functions.

Ground 2: Anticipation of Claims 11-16 and 21 by Fujisawa

  • Prior Art Relied Upon: Fujisawa (JP2005330867).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that Fujisawa, a prior art dual fuel generator, disclosed every limitation of claims 11-16 and 21. Fujisawa taught a valve assembly with two fuel valves operated by cam followers. Petitioner argued these cam followers met the claim limitation for first and second "selector switches" that manually actuate the valves. The rotary knob and cam body in Fujisawa, which controlled the cam followers and prevented simultaneous valve operation, met the limitation for an "interlock." Fujisawa’s system included two fuel inputs, two outputs, and non-solenoid mechanical valves, thus anticipating the dependent claims as well.

Ground 3: Obviousness of Claims 1-21 over Fujisawa, DuroMax, Nakafushi, and Olmr (Alternative Ground)

  • Prior Art Relied Upon: Fujisawa (JP2005330867), DuroMax (Duro Max XP4400EH Operator’s Manual), Nakafushi (JPS61283734A), and Olmr (Patent 5,301,644).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground was argued in the alternative, adopting the Patent Owner’s apparent claim construction from related litigation where the "selector switch" of claims 1-10 is a rotary knob that directly actuates the valve assembly. Petitioner asserted that Fujisawa’s rotary knob met this construction. The combination then added the teachings of DuroMax, Nakafushi, and Olmr.
    • Motivation to Combine: A POSA would combine these references to improve upon Fujisawa’s design. First, a POSA would be motivated to modify Fujisawa’s generator to run on LPG and gasoline (as taught by DuroMax) instead of two types of LPG, because gasoline is a more common and energy-dense fuel. This modification would include adding a carburetor (DuroMax). Second, to address the resulting problem of residual gasoline in the new carburetor, a POSA would integrate a carburetor shutoff solenoid (Olmr) controlled by the fuel selector knob, as taught by Nakafushi, to improve engine performance and safety.
    • Expectation of Success: A POSA would reasonably expect success because Fujisawa already taught coupling mechanical rotation of its selector to other functions via cams and pulleys, which could be readily adapted to actuate a solenoid switch.

  • Additional Grounds: Petitioner asserted that claims 11-16 and 20-21 are obvious over DuroMax in view of DeVries. Petitioner also asserted that claims 11-16 and 20-21 are obvious over Fujisawa in view of DuroMax.

4. Key Claim Construction Positions

  • "selector switch" (for Claims 1-10): Petitioner argued this term should be construed as "a movable component whose positioning enables subsequent user selection of only one fuel source." This construction was based on the specification and prosecution history of the parent ’101 patent, where the applicant distinguished the invention from prior art by arguing the claimed selector switch was a separate mechanical interlock (a sliding panel) that did not directly actuate the valves, but merely enabled access to one valve handle at a time.
  • "selector switch" and "interlock" (for Claims 11-21): Petitioner argued that in this claim set, the term "selector switch" should be construed as a "valve handle." Consequently, the claimed "interlock" corresponds to the sliding panel described in the specification, which functions as the "selector switch" in claims 1-10.
  • "valve assembly": Petitioner argued this term requires a structure that is separate and distinct from the "selector switch" or "interlock" and must comprise at least one fuel valve and a corresponding valve handle. This was based on arguments made during prosecution of the parent patent to overcome prior art.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1-21 of the ’390 patent as unpatentable.