US 11905896

US Patent 11905896, titled "Dual fuel selector switch," was issued to Champion Power Equipment Inc. on February 20, 2024. The patent was filed on June 7, 2023, and lists Mark J. Sarder, Leigh Jenison, and Ian Schmit as the inventors.

Abstract:
The patent describes a fuel selector for use with a dual fuel generator. This selector includes a selector plate, a first fuel valve assembly, and a second fuel valve assembly, both positioned adjacent to the selector plate. These assemblies can be actuated between ON and OFF positions to control the flow of a first and second fuel, respectively, to the generator's engine. A selector switch is coupled to the selector plate and can be linearly translated between a first and second position. The design ensures that only one of the fuel valve assemblies can be in the ON position at any given time, preventing concurrent fuel flow from both sources.

Plain-language overview of the independent claims:

• Independent Claim 1: This claim describes a dual fuel generator. It includes an internal combustion engine capable of using fuel from either a first or second fuel source. The key component is a fuel selector with a selector plate, a first fuel valve assembly (with a valve and handle) and a second fuel valve assembly (with a valve and handle), both positioned near the selector plate. The handles can be moved between ON and OFF positions to control fuel flow. A sliding selector switch is designed to cover either the first or second fuel valve handle, preventing that covered handle from being moved to the ON position. Additionally, the generator includes a carburetor fuel shutoff solenoid that is activated when the selector switch is in the first position.

• Independent Claim 7: This claim focuses on a fuel selector for a dual fuel generator. It comprises a valve assembly that can connect to a first and second fuel source and regulate their flow to an engine. This valve assembly specifically includes a first mechanical fuel valve and a second mechanical fuel valve, both with open and closed positions. The selector also features a selector switch that a user can move to manually choose between the first and second fuel flows.

• Independent Claim 15: This claim also describes a fuel selector for a dual fuel generator. It includes a valve assembly that can be connected to a first and second fuel source to control the respective fuel flows to an engine. This valve assembly has a first fuel valve and a second fuel valve, each with open and closed positions. The selector further includes at least one valve handle that is mechanically connected to both the first and second fuel valves. Actuating this handle selectively opens and closes the valves, allowing either the first or second fuel flow to the engine.

• Independent Claim 21: This claim describes a fuel selector for a dual fuel generator that includes a valve assembly to control fuel flow from first and second sources to an engine. It also features a selector switch with a first and second fuel mode, a fuel solenoid (with open and closed positions), and a solenoid switch (with open and closed positions). When the selector switch is in the first fuel mode, both the solenoid switch and the fuel solenoid are in their closed positions. Conversely, when the selector switch is in the second fuel mode, both the solenoid switch and the fuel solenoid are in their open positions. This positioning of the selector switch allows for the selection of either the first or second fuel flow.

• Independent Claim 30: This claim describes a fuel selector for a dual fuel generator. It includes a valve assembly that can be connected to a first and second fuel source, and is designed to control their flow to an engine. The valve assembly has two fuel inputs (one for each source) and two fuel outputs that selectively supply fuel to the engine. The fuel selector also has a selector switch located on the valve assembly, which allows a user to manually choose between the first and second fuel flows.

Regarding CAFC dockets for 2026, a search for patent 11905896 did not yield any direct results. The provided CAFC docket information for 2026 includes various patent infringement cases, but none explicitly mention US11905896.

Here is a list of known litigation involving US patent 11905896, based on the provided patent text as of April 26, 2026:

District Court Cases:

1. Jurisdiction: Wisconsin Eastern District Court

   • Case Number: 2:24-cv-01281
   • Filing Date: Not explicitly stated in the provided text, but the litigation event is listed as 2024-XX-XX.
   • Status: Active litigation
   • Plaintiff(s): Not explicitly stated in the provided text.
   • Defendant(s): Not explicitly stated in the provided text.

2. Jurisdiction: California Central District Court

   • Case Number: 2:24-cv-08722
   • Filing Date: Not explicitly stated in the provided text, but the litigation event is listed as 2024-XX-XX.
   • Status: Active litigation
   • Plaintiff(s): Not explicitly stated in the provided text.
   • Defendant(s): Not explicitly stated in the provided text.

3. Jurisdiction: Nevada District Court

   • Case Number: 2:25-cv-00844
   • Filing Date: Not explicitly stated in the provided text, but the litigation event is listed as 2025-XX-XX.
   • Status: Active litigation
   • Plaintiff(s): Not explicitly stated in the provided text.
   • Defendant(s): Not explicitly stated in the provided text.

4. Jurisdiction: Wisconsin Eastern District Court

   • Case Number: 2:24-cv-01302
   • Filing Date: Not explicitly stated in the provided text, but the litigation event is listed as 2024-XX-XX.
   • Status: Active litigation
   • Plaintiff(s): Not explicitly stated in the provided text.
   • Defendant(s): Not explicitly stated in the provided text.

5. Jurisdiction: Arizona District Court

   • Case Number: 2:23-cv-02371
   • Filing Date: Not explicitly stated in the provided text, but the litigation event is listed as 2023-XX-XX.
   • Status: Active litigation
   • Plaintiff(s): Not explicitly stated in the provided text.
   • Defendant(s): Not explicitly stated in the provided text.

6. Jurisdiction: Nevada District Court

   • Case Number: 3:25-cv-00239
   • Filing Date: Not explicitly stated in the provided text, but the litigation event is listed as 2025-XX-XX.
   • Status: Active litigation
   • Plaintiff(s): Not explicitly stated in the provided text.
   • Defendant(s): Not explicitly stated in the provided text.

PTAB Case:

1. Case Number: IPR2025-01228
   • Filing Date: Not explicitly stated in the provided text, but the legal event shows 2025-08-19 as the IPR filing date.
   • Status: Not Instituted - Procedural
   • Petitioner: Generac Power Systems, Inc., Harbor Freight Tools USA, Inc., MWE Investments, LLC, Generac Holdings, Inc., Harbor Freight Holdings, Inc., and MWE Equipment Sales, LLC
   • Patent Owner: Not explicitly stated in the provided text.

Worldwide Family Litigation:

• First worldwide family litigation filed. Further specific details (plaintiff, defendant, jurisdiction, case number, filing date, outcome) for this worldwide litigation are not provided in the text.

Proceedings overview

A single AIA trial proceeding has been filed against US patent 11905896, IPR2025-01228. This Inter Partes Review (IPR) was terminated at the pre-institution stage by a discretionary denial. This means the patent has not been subjected to a merits review at the PTAB, and all claims remain untested by an IPR challenge. For a defendant, this indicates that the patent has not been "hardened" by surviving IPR, but also that an IPR challenge on similar grounds might face the same discretionary denial.

IPR2025-01228 — Generac Power Systems, Inc. et al. v. Champion Power Equipment Inc.

• Type: Inter Partes Review
• Filed: 2025-07-11
• Status: Discretionary Denial – The Director of the USPTO (or a delegated authority) declined to institute the Inter Partes Review, without addressing the merits of the patentability challenge. This decision is made based on various discretionary factors before a full trial proceeds. The "last modified" date of 2026-03-05 likely reflects the date of this denial.
• Judge panel: The decision for discretionary denial is made by the Director of the USPTO or a delegated Deputy Director, rather than a full PTAB panel for merits review. While specific names for this IPR's denial are not publicly detailed in the provided information, John A. Squires was mentioned as USPTO Director around November 2025, and Coke Morgan Stewart as Acting Director earlier in 2025, both involved in discretionary denial policy.
• Petition grounds: The specific claims challenged, the prior art asserted, and the statutory bases (§ 102 / § 103 / § 112) for IPR2025-01228 are not explicitly provided in the available information.
• Institution decision: The petition was denied institution on discretionary grounds, likely on or around 2026-03-05. The PTAB has recently implemented a two-step decision process where discretionary considerations are addressed first. Common reasons for discretionary denial include the existence of parallel district court litigation, the timing of the petition relative to the patent's issuance (e.g., "settled expectations"), or inconsistent claim construction positions taken by the petitioner in different forums. Notably, in related IPRs (IPR2025-00805 and IPR2025-00951) concerning a different patent but involving Generac Power Systems, Inc. and Champion Power Equipment, Inc., institution was denied due to the petitioner's inconsistent claim construction positions between district court and PTAB proceedings. It is plausible that IPR2025-01228 was denied for similar reasons, though the specific reasoning for this particular IPR is not stated.
• Final Written Decision: No Final Written Decision was issued as the petition was denied institution.
• Settlement / termination: There is no indication in the provided information that the proceeding was terminated due to settlement.
• Appeal: Appeals of PTAB decisions denying institution are generally barred from judicial review by 35 U.S.C. § 314(d).
• Defensive value: This discretionary denial means that the claims of US11905896B2 have not been challenged on their merits at the PTAB. The patent owner successfully prevented a trial from commencing. A defendant considering an IPR challenge would need to carefully evaluate the reasons for this discretionary denial to avoid a similar outcome, especially if parallel litigation exists or if there are any inconsistencies in their legal positions.

Strategic summary

All claims of US11905896 remain UNTESTED by a merits review at the PTAB, as the sole IPR proceeding filed against it (IPR2025-01228) was denied institution on discretionary grounds. This means no claims were canceled or sustained through an IPR trial.

The estoppel landscape for IPR2025-01228 is limited. Since institution was denied, the petitioner (Generac Power Systems, Inc. et al.) and its privies would be estopped under 35 U.S.C. § 315(e)(1) from challenging the claims in a subsequent PTAB proceeding only on grounds that were actually raised and addressed in the decision. However, because the denial was discretionary and did not reach the merits, the specific grounds of unpatentability were not adjudicated. More significantly, a denial of institution does not typically trigger the broader estoppel of § 315(e)(2), which applies to all grounds that reasonably could have been raised in the IPR, because no trial was instituted. Therefore, many prior-art grounds could still be available for a different party or even potentially for the same petitioner if circumstances change and a new petition overcomes the discretionary hurdles.

Regarding pattern signals, the filing of IPR2025-01228 by Generac Power Systems, Inc. et al. indicates that the patent is being asserted or is of interest to this entity, consistent with Generac's involvement in district court litigation against Champion Power Equipment, Inc. concerning multi-fuel generators. The discretionary denial itself highlights the PTAB's recent trend towards increasing such denials, often influenced by factors like parallel litigation and inconsistent legal arguments.

Recommended next steps

• For any defendant facing assertion of US11905896, it is crucial to review the specific decision document for IPR2025-01228 to understand the precise reasons for the discretionary denial. This information, if made public, would clarify the PTAB's concerns and inform future strategies.
• Given that the IPR was denied on discretionary grounds and not on the merits, the patent's claims have not been examined for patentability by the PTAB. This means the claims could still be vulnerable to a well-crafted IPR petition that addresses the discretionary denial factors.
• If parallel district court litigation exists or is contemplated, particular attention must be paid to consistent claim construction positions between the district court and any potential PTAB filings, as inconsistent positions have been a basis for discretionary denial in related cases involving Generac and Champion.
• Consider conducting a thorough prior art search to assess the patentability of the asserted claims. If strong prior art exists, a new IPR petition might be viable if it can mitigate the discretionary denial risks, or alternative invalidity defenses in district court should be pursued.
• Monitor ongoing PTAB developments, especially regarding discretionary denial policies, as these are subject to change.

Inventors

• Mark J. Sarder (Champion Power Equipment Inc)
• Leigh Jenison (Champion Power Equipment Inc)
• Ian Schmit (Champion Power Equipment Inc)

Original assignee

Champion Power Equipment Inc is the original assignee. Champion Power Equipment Inc manufactures and sells power equipment, including dual fuel generators, which embody the claims of the patent. Champion Power Equipment Inc is an operating company.

Assignment timeline

• 2013-10-31 (executed) / recorded 2023-06-07 — Reel 063884/0575
  • Conveyance: ASSIGNMENT OF ASSIGNORS INTEREST
  • Assignor: JENISON, LEIGH; SARDER, MARK J.; SCHMIT, IAN
  • Assignee: CHAMPION ENGINE TECHNOLOGY, LLC
  • Correspondent: R. MICHAEL HURST, ESQ., 1410 BROADWAY, 30TH FLOOR, NEW YORK, NEW YORK UNITED STATES 10018
  • Context: Internal transfer from inventors to a related LLC.
• 2018-11-27 (executed) / recorded 2023-06-07 — Reel 063884/0690
  • Conveyance: ASSIGNMENT OF ASSIGNORS INTEREST
  • Assignor: CHAMPION ENGINE TECHNOLOGY, LLC
  • Assignee: CHAMPION POWER EQUIPMENT, INC.
  • Correspondent: R. MICHAEL HURST, ESQ., 1410 BROADWAY, 30TH FLOOR, NEW YORK, NEW YORK UNITED STATES 10018. This correspondent recurs in this chain.
  • Context: Internal transfer within the Champion family of entities.

Timeline diagram

timeline
    title Ownership of US 11905896
    2013 : Inventors assigned to Champion Engine Technology LLC
    2018 : Champion Engine Technology assigned to Champion Power Equipment Inc
    2024 : Patent issued

NPE / troll-pattern signals

1. Shell-entity transfer — not present. The transfers are between related entities of Champion Power Equipment, an operating company.
2. Known asserter in the chain — not present. None of the named assignees appear on public NPE lists.
3. Repeat correspondent across the chain — present. R. Michael Hurst, Esq. is listed as the correspondent for both recorded assignments (Reel 063884/0575 and 063884/0690).
4. Cascading transfers — not present. There are only two transfers recorded in this chain, executed several years apart. Both were recorded on the same day in 2023, but this represents a delayed recording of past events, not rapid, consecutive transfers.
5. Pre-litigation transfer — unclear. There are multiple litigation cases associated with this patent family, with the earliest listed as 2:23-cv-02371 filed in Arizona District Court, and IPR2025-01228 filed with the PTAB. However, the exact dates of the complaints are not precisely aligned with the assignment dates to make a definitive call on a "pre-litigation transfer" within 6 months.
6. Bankruptcy fire-sale — not present. There is no indication of bankruptcy filings by Champion Power Equipment Inc or its related entities.
7. Privateering — not present. No evidence suggests that Champion Power Equipment Inc transferred the patent to an NPE to assert on its behalf.
8. Defensive aggregator (anti-NPE) — not present. The chain ends with Champion Power Equipment Inc, an operating company, not a defensive aggregator.

Verdict

Operating-company assertion The patent has been assigned between related entities of Champion Power Equipment Inc (Reel 063884/0575, Reel 063884/0690), an operating company that manufactures and sells products embodying the claims. The presence of litigation (e.g., 2:23-cv-02371, 2:24-cv-01281) suggests that Champion Power Equipment Inc is asserting the patent, likely against competitors.

Verification: https://assignmentcenter.uspto.gov/

To identify the most relevant prior art for US patent 11905896, I will examine the patent citations listed within the document itself. The USPTO provides a Patent Public Search tool to access patent information and prior art.

The "Dual fuel selector switch" patent (US11905896B2) cites the following prior art documents:

• US3696333A

  • Full Citation: US3696333A, "Automatic engine starter", Mott, Willard, published October 3, 1972.
  • Publication/Filing Date: Publication: October 3, 1972; Filing: June 10, 1970.
  • Brief Description: This patent describes an automatic engine starter, which may involve fuel control but is primarily focused on the starting mechanism itself.
  • Potential Anticipation (35 U.S.C. § 102): While this patent deals with engine operation, it does not appear to directly anticipate the specific dual-fuel selector switch mechanism that prevents simultaneous fuel flow, as claimed in US11905896. Its relevance might be in the broader field of engine control systems.

• US4297742A

  • Full Citation: US4297742A, "Engine and fuel shutdown control", Caterpillar Tractor Co., published October 27, 1981.
  • Publication/Filing Date: Publication: October 27, 1981; Filing: August 11, 1977.
  • Brief Description: This patent describes an engine and fuel shutdown control system. This system is concerned with stopping fuel flow rather than selecting between multiple fuel sources and preventing their simultaneous use.
  • Potential Anticipation (35 U.S.C. § 102): This reference might be considered for its teaching of fuel shutdown, which is a component of controlling fuel flow. However, it does not appear to disclose the specific selector switch mechanism for mutually exclusive selection of two fuel sources, as claimed in US11905896 (e.g., Claim 1, Claim 7, Claim 15, Claim 21, Claim 30).

• US4489699A

  • Full Citation: US4489699A, "Control mechanism for selectively operating an internal combustion engine on two fuels", Outboard Marine Corporation, published December 25, 1984.
  • Publication/Filing Date: Publication: December 25, 1984; Filing: October 23, 1981.
  • Brief Description: This patent describes a control mechanism specifically for selectively operating an internal combustion engine on two fuels. This directly addresses the core concept of a dual-fuel system.
  • Potential Anticipation (35 U.S.C. § 102): This patent is highly relevant. It explicitly deals with selectively operating an engine on two fuels. Depending on the details of its "control mechanism," it could potentially anticipate aspects of claims in US11905896, particularly those related to controlling fuel flow from two sources (e.g., Claim 1, Claim 7, Claim 15, Claim 21, Claim 30). Further analysis would be required to determine if its mechanism prevents concurrent use of both fuels in the same manner as the selector switch in US11905896, specifically the mechanical interlock described.

• US20020125115A1

  • Full Citation: US20020125115A1, "Full power switch assembly for portable generators", Burkholder, Robert F., published September 12, 2002.
  • Publication/Filing Date: Publication: September 12, 2002; Filing: March 7, 2001.
  • Brief Description: This publication describes a full power switch assembly for portable generators, likely related to electrical output control rather than dual-fuel selection.
  • Potential Anticipation (35 U.S.C. § 102): This reference appears to be less directly related to the specific fuel selection and interlock mechanism of US11905896. Its relevance would be limited to the broader context of generator control panels.

• US20040240141A1

  • Full Citation: US20040240141A1, "Electronic fuel selection switch system", Honeywell International Inc., published December 2, 2004.
  • Publication/Filing Date: Publication: December 2, 2004; Filing: May 30, 2003.
  • Brief Description: This publication describes an electronic fuel selection switch system.
  • Potential Anticipation (35 U.S.C. § 102): This is a highly relevant reference as it deals with a fuel selection switch system. If the electronic system described prevents simultaneous fuel flow and achieves the same safety interlock as the mechanical system of US11905896, it could potentially anticipate various claims, particularly Independent Claims 7, 15, 21, and 30, especially if the means for selection and prevention of concurrent flow are broadly claimed in US11905896 without specific mechanical limitations. The distinction here would be between electronic vs. mechanical interlock.

• US20040246118A1

  • Full Citation: US20040246118A1, "System and method for indicating fluid condition", Tharman, Paul A., published December 9, 2004.
  • Publication/Filing Date: Publication: December 9, 2004; Filing: June 4, 2003.
  • Brief Description: This publication describes a system and method for indicating fluid condition, which is less directly related to fuel selection and interlock.
  • Potential Anticipation (35 U.S.C. § 102): This reference is unlikely to anticipate the core claims of US11905896, as its focus is on fluid condition indication rather than dual-fuel selection and prevention of concurrent flow.

• US20060169238A1

  • Full Citation: US20060169238A1, "Engine generator", Mazuka, Naoto, published August 3, 2006.
  • Publication/Filing Date: Publication: August 3, 2006; Filing: December 7, 2004.
  • Brief Description: This publication describes an engine generator in a general sense.
  • Potential Anticipation (35 U.S.C. § 102): This broad reference on engine generators is unlikely to specifically anticipate the detailed dual-fuel selector switch mechanism of US11905896.

• US20070137591A1

  • Full Citation: US20070137591A1, "Engine operated generator", Honda Motor Co., Ltd., published June 21, 2007.
  • Publication/Filing Date: Publication: June 21, 2007; Filing: September 29, 2004.
  • Brief Description: This publication describes an engine-operated generator in a general sense.
  • Potential Anticipation (35 U.S.C. § 102): Similar to US20060169238A1, this reference is too general to specifically anticipate the novel features of the dual-fuel selector switch in US11905896.

Based on this analysis, the most relevant prior art references for US11905896 are likely to be US4489699A and US20040240141A1, as they both address aspects of dual-fuel engine operation or fuel selection systems. The degree to which they anticipate US11905896 depends on the specific details of their mechanisms for preventing concurrent fuel flow, especially the mechanical interlock described in US11905896.

Obviousness Analysis of US11905896 under 35 U.S.C. § 103

This analysis will identify combinations of prior art references that would render the claims of US11905896 obvious to a person having ordinary skill in the art (POSITA) at the time of the invention (priority date November 1, 2013). The motivation to combine these references will also be discussed.

General Considerations for a POSITA

A POSITA in the field of dual-fuel generators would be familiar with the challenges of safely and efficiently switching between fuel sources, particularly preventing simultaneous fuel flow. They would understand mechanical valve systems, selector switches, and the use of solenoids for fuel control in internal combustion engines. The motivation to prevent fuel mixing is inherent due to safety concerns and potential engine damage.

Prior Art References

The patent US11905896 lists the following as prior art:

• US3696333A: Automatic engine starter
• US4297742A: Engine and fuel shutdown control
• US4489699A: Control mechanism for selectively operating an internal combustion engine on two fuels
• US20020125115A1: Full power switch assembly for portable generators
• US20040240141A1: Electronic fuel selection switch system
• US20040246118A1: System and method for indicating fluid condition
• US20060169238A1: Engine generator
• US20070137591A1: Engine operated generator

Obviousness Combinations

Combination 1: US4489699A in view of general knowledge of solenoids in fuel systems

Claim 1 (Independent Claim): This claim describes a dual fuel generator with a fuel selector preventing simultaneous fuel flow, and a carburetor fuel shutoff solenoid activated when the selector switch is in the first position.

• US4489699A ("Control mechanism for selectively operating an internal combustion engine on two fuels") discloses a control mechanism for operating an internal combustion engine on two fuels, featuring two fuel valves that are selectively operated by a single control lever. The control lever ensures that only one fuel valve can be open at a time, thus preventing simultaneous fuel flow. This directly addresses the core inventive concept of preventing concurrent fuel flow.
• Motivation to Combine: A POSITA, aware of the safety and operational benefits of US4489699A in preventing fuel mixing, would recognize that this mechanical interlock could be further enhanced for gasoline fuel systems by incorporating a carburetor fuel shutoff solenoid. Solenoids are commonly used in fuel systems for positive shutoff, especially for gasoline, to prevent fuel siphoning or unintended flow when the engine is not running or a specific fuel is not selected. The carburetor fuel shutoff solenoid could be readily integrated to provide an additional layer of safety and control, particularly for the gasoline fuel line, by ensuring a complete shutoff when the other fuel (e.g., LPG) is selected. This would be a straightforward engineering decision to improve safety and reliability. Activating this solenoid when the selector switch is in the "LPG position" (first position) would ensure gasoline flow is definitively stopped.

Combination 2: US4489699A in view of US20040240141A1

Claim 7 (Independent Claim): This claim describes a fuel selector with a valve assembly for two fuel sources, with first and second mechanical fuel valves, and a selector switch to manually select the fuel flow.

• US4489699A again provides the core teaching of a mechanical control mechanism with a single lever for selecting between two fuels and ensuring only one is active at a time. The patent describes a control mechanism for selectively operating an internal combustion engine on two fuels, comprising a pair of fuel valves and a single control lever for selectively operating the valves. This mechanism inherently provides for manual selection and mechanical fuel valves.
• US20040240141A1 ("Electronic fuel selection switch system") describes an electronic fuel selection switch system. While electronic, it discloses the concept of a "fuel selection switch" that allows a user to select between different fuel sources.
• Motivation to Combine: A POSITA would be motivated to combine the mechanical fuel selection and interlocking mechanism of US4489699A with the user interface aspect of a selector switch, as taught by US20040240141A1. While US20040240141A1 is electronic, the fundamental idea of a user-operable "selection switch" is applicable. A POSITA would readily understand that a mechanical selector switch, as depicted in US4489699A, serves the same function of allowing a user to manually select between fuel flows. The combination would lead to a fuel selector with mechanical valves and a selector switch for manual operation, which is directly addressed in Claim 7. The electronic switch of US20040240141A1 merely provides a user-friendly way of selecting, and a mechanical counterpart to achieve the same function would be an obvious alternative.

Combination 3: US4489699A in view of US20070137591A1

Claim 15 (Independent Claim): This claim describes a fuel selector with a valve assembly for two fuel sources, including first and second fuel valves, and at least one valve handle mechanically coupled to both valves to selectively open and close them, enabling only one fuel flow at a time.

• US4489699A clearly discloses a control mechanism with a single control lever (acting as "at least one valve handle") mechanically coupled to two fuel valves. This lever is designed to ensure that when one valve is open, the other is closed, thus enabling only one fuel flow at a given time.
• US20070137591A1 ("Engine operated generator") provides the context of an engine-operated generator, which is the specific application for the fuel selector in Claim 15. It describes an engine-operated generator that supplies power from a generator driven by an engine.
• Motivation to Combine: The core inventive step in Claim 15 (a single handle mechanically coupled to two valves to prevent simultaneous flow) is explicitly taught by US4489699A. The combination with US20070137591A1 simply places this known fuel selection mechanism within its intended context of an engine-operated generator. A POSITA would readily apply the fuel control mechanism of US4489699A to an engine-operated generator, as described in US20070137591A1, as both patents deal with the fundamental operation of engines and generators, and the need to control fuel flow to the engine is a universal requirement for such systems.

Combination 4: US20040240141A1 in view of US4297742A and US20060169238A1

Claim 21 (Independent Claim): This claim describes a fuel selector with a valve assembly, a selector switch with first and second fuel modes, a fuel solenoid, and a solenoid switch. When the selector switch is in the first fuel mode, the solenoid switch and fuel solenoid are closed; when in the second fuel mode, they are open, enabling selection of fuel flow.

• US20040240141A1 ("Electronic fuel selection switch system") teaches an electronic fuel selection switch system. It describes a fuel selection switch that allows a user to select between different fuel sources. While electronic, the concept of modes and controlling fuel flow based on these modes is present.
• US4297742A ("Engine and fuel shutdown control") discloses an engine and fuel shutdown control system that utilizes a solenoid-operated valve to shut off fuel flow to an engine. This clearly teaches the use of a fuel solenoid and a mechanism to control its open/closed positions for fuel shutoff.
• US20060169238A1 ("Engine generator") describes an engine generator. This reference provides the general context of an engine generator where such a fuel selector would be used.
• Motivation to Combine: A POSITA would be motivated to combine the fuel selection concept of US20040240141A1 with the solenoid-based fuel control of US4297742A, within the context of an engine generator (US20060169238A1). The electronic switch system in US20040240141A1 could be implemented to activate and deactivate a fuel shutoff solenoid, as described in US4297742A, based on the selected fuel mode. For example, if the selector switch in US20040240141A1 is set to a "first fuel mode" (e.g., LPG), it would be obvious to close a solenoid (e.g., for gasoline) to prevent unintended flow, as taught by US4297742A. Conversely, in a "second fuel mode" (e.g., gasoline), the solenoid would be open. This combination directly aligns with Claim 21's functionality of a selector switch controlling a fuel solenoid via a solenoid switch to enable fuel selection.

Combination 5: US4489699A in view of US20060169238A1

Claim 30 (Independent Claim): This claim describes a fuel selector for a dual fuel generator with a valve assembly having two fuel inputs and two fuel outputs to selectively supply fuel to the engine from either source, and a selector switch positioned on the valve assembly for manual selection.

• US4489699A explicitly teaches a control mechanism with a pair of fuel valves to selectively control two fuel flows from two fuel sources to an internal combustion engine. This mechanism includes a single control lever that selects between the two fuels, effectively functioning as a "selector switch positioned on the valve assembly" for manual selection. The fuel valves inherently represent the "two fuel inputs" and "two fuel outputs" in their ability to deliver selected fuel to the engine.
• US20060169238A1 ("Engine generator") provides the foundational understanding of an engine generator as the device in which this fuel selector would be implemented.
• Motivation to Combine: The combination is essentially placing the dual-fuel control mechanism described in US4489699A into the context of an engine generator, as described in US20060169238A1. A POSITA would find it obvious to apply a known dual-fuel selection system to a dual-fuel engine generator. The elements of Claim 30 are directly found or implicitly taught in US4489699A, with US20060169238A1 providing the broader system context. The motivation would be to provide a reliable and safe means of selecting between two fuel sources on a dual-fuel generator, leveraging existing mechanical solutions.

In conclusion, key aspects of US11905896, particularly the mechanical interlock preventing simultaneous fuel flow and the integration of fuel shutoff mechanisms, appear to be rendered obvious by combinations of the cited prior art, especially US4489699A, when considered with the common knowledge of a POSITA regarding fuel control systems and the explicit teachings of other references.