US 10697398

The search results from the CAFC website do not directly list specific dockets for US patent 10697398 in 2026. They provide general information on how to find case information, including case filings and records, and mention PACER as a resource. The provided patent text already indicated general litigation and a PTAB case (IPR2025-01271), which is an inter partes review before the Patent Trial and Appeal Board, not a CAFC case directly. District court cases were also mentioned. To confirm CAFC dockets for 2026, a more direct search within PACER or contacting the Clerk's Office would be necessary, but this is outside the scope of the current tool's capabilities. Based on the current search, there is no direct confirmation of CAFC dockets specifically for 2026 for this patent.

Therefore, I will proceed with summarizing the patent information and noting the lack of specific CAFC 2026 dockets.

US Patent 10697398: Concise Summary

• Title: Batteryless dual fuel engine with liquid fuel cut-off
• Assignee: Champion Power Equipment Inc.
• Inventors: Kendall J. Collie, Mark J. Sarder, Aleko D. Sotiriades, James J. Dehn, Leigh Jenison, Hiroaki Sato
• Filing Date: October 28, 2015
• Issue Date: June 30, 2020
• Abstract: A dual fuel engine includes an engine operable on a gaseous fuel and a liquid fuel and a switch to change operation of the engine between gaseous fuel and liquid fuel. The dual fuel engine also includes a carburetor attached to an intake of the engine to mix air and fuel and connect to a gaseous fuel source and a liquid fuel source. A liquid fuel cut-off attaches to the carburetor to interrupt liquid fuel upon actuation of the switch from liquid fuel to gaseous fuel.

Plain-Language Overview of Independent Claims (based on "Brief Description of the Invention"):

Please note: The full, legal text of the claims was not provided in the authoritative patent text. The following overview is based on the "Brief Description of the Invention" section, which summarizes key aspects of the invention.

1. Dual Fuel Engine with Liquid Fuel Cut-off: This claim describes a dual fuel engine that can run on either a gaseous fuel or a liquid fuel. It has a carburetor connected to both fuel sources. A key feature is a switch to select the fuel type, and a liquid fuel cut-off mechanism that stops the flow of liquid fuel to the carburetor when the engine is switched from liquid fuel to gaseous fuel.
2. Batteryless Dual Fuel Generator with Fuel Shutoff: This claim focuses on a batteryless dual fuel generator. It includes a pull-start engine connected to an alternator, capable of running on gaseous or liquid fuel. The carburetor has a float bowl and a fuel passage for liquid fuel. The generator also features a switch for fuel selection and a fuel shutoff that closes the liquid fuel passage in the carburetor when gaseous fuel operation is selected.
3. Carburetor with Non-Linear Fuel Shutoff: This claim details a carburetor equipped with a fuel shutoff. The carburetor has a float bowl, a throat, and a fuel passage for liquid fuel. The fuel shutoff has an internal part that closes the fuel passage and an external part for actuation. A distinctive aspect is that the internal fuel shutoff operates (opens and closes the fuel passage) without linear motion.
4. Method of Assembling a Dual Fuel Engine: This claim outlines a method for putting together a dual fuel engine. It involves providing an engine that can use both gaseous and liquid fuels. A carburetor is attached to the engine's intake to deliver these fuels, having a throat, float bowl, and liquid fuel passage. The method includes connecting a gaseous fuel source to the throat and a liquid fuel source to the float bowl. Finally, a fuel selection switch is coupled to the engine, and a liquid fuel cut-off is attached to the carburetor to halt liquid fuel flow when the switch is set for gaseous fuel.

CAFC 2026 Dockets:

As of April 26, 2026, a search for US patent 10697398 in the CAFC 2026 dockets did not yield specific case filings directly referencing this patent. While the patent is noted to have ongoing litigation (including a PTAB case IPR2025-01271 and several district court cases in Wisconsin, Nevada, California, and Arizona), direct evidence of a 2026 CAFC docket related to this patent was not found in the accessible search results.

I have identified several known litigation cases involving US patent 10697398 based on the provided patent information.

Here is a list of known litigation involving US patent 10697398:

1. PTAB Case

• Case Number: IPR2025-01271
• Jurisdiction: Patent Trial and Appeal Board (PTAB)
• Current Status: Pending - Instituted
• Plaintiff(s): Not specified in the provided text.
• Defendant(s): Not specified in the provided text.
• Filing Date: Not specified in the provided text, other than "IPR2025-01271 filed".

2. US District Court Cases

• Jurisdiction: Wisconsin Eastern District Court
  • Case Number: 2:24-cv-01302
  • Filing Date: Not specified in the provided text.
  • Current Status: Not specified in the provided text.
  • Plaintiff(s): Not specified in the provided text.
  • Defendant(s): Not specified in the provided text.
• Jurisdiction: Wisconsin Eastern District Court
  • Case Number: 2:24-cv-01281
  • Filing Date: Not specified in the provided text.
  • Current Status: Not specified in the provided text.
  • Plaintiff(s): Not specified in the provided text.
  • Defendant(s): Not specified in the provided text.
• Jurisdiction: Nevada District Court
  • Case Number: 3:25-cv-00239
  • Filing Date: Not specified in the provided text.
  • Current Status: Not specified in the provided text.
  • Plaintiff(s): Not specified in the provided text.
  • Defendant(s): Not specified in the provided text.
• Jurisdiction: Nevada District Court
  • Case Number: 2:25-cv-00844
  • Filing Date: Not specified in the provided text.
  • Current Status: Not specified in the provided text.
  • Plaintiff(s): Not specified in the provided text.
  • Defendant(s): Not specified in the provided text.
• Jurisdiction: California Central District Court
  • Case Number: 2:24-cv-08722
  • Filing Date: Not specified in the provided text.
  • Current Status: Not specified in the provided text.
  • Plaintiff(s): Not specified in the provided text.
  • Defendant(s): Not specified in the provided text.
• Jurisdiction: Arizona District Court
  • Case Number: 2:23-cv-02371
  • Filing Date: Not specified in the provided text.
  • Current Status: Not specified in the provided text.
  • Plaintiff(s): Not specified in the provided text.
  • Defendant(s): Not specified in the provided text.

The provided patent text indicates that "Family has litigation" and links to a "Global patent litigation dataset” by Darts-ip and "Unified Patents PTAB Data" and "Unified Patents Litigation Data", but these links are not directly searchable in this environment for further details such as specific plaintiffs, defendants, or filing dates for all the listed district court cases. The current status for the PTAB case IPR2025-01271 is "Pending - Instituted". Without further access to these external databases, I cannot provide the missing details like plaintiffs, defendants, and specific filing dates for the district court cases, or an outcome for any of the cases.

Therefore, while litigation is known to exist, comprehensive details for each case are not fully available from the provided patent document.
.Here is a list of known litigation involving US patent 10697398, including details found through additional searching:

1. PTAB Case

• Case Number: IPR2025-01271
• Jurisdiction: Patent Trial and Appeal Board (PTAB)
• Current Status: Instituted (Pending - Instituted, as per the patent text)

2. US District Court Cases

• Jurisdiction: Wisconsin Eastern District Court

  • Case Number: 2:24-cv-01302
  • Plaintiff(s): Champion Power Equipment Inc.
  • Defendant(s): Harbor Freight Tools USA Inc.
  • Filing Date: October 14, 2024
  • Outcome/Current Status: Dismissed. The Eastern District of Wisconsin dismissed Champion's infringement lawsuit, citing the first-to-file rule, as Harbor Freight had filed a declaratory judgment action five days prior in the Central District of California. The substantive patent dispute will proceed in the Central District of California.

• Jurisdiction: Wisconsin Eastern District Court

  • Case Number: 2:24-cv-01281
  • Plaintiff(s): Champion Power Equipment Inc.
  • Defendant(s): Generac Power Systems Inc.
  • Filing Date: October 9, 2024
  • Outcome/Current Status: Ongoing. This case was mentioned in a judicial profile analysis, indicating it was active as of 2024. A separate patent infringement action brought by Champion against Generac was filed on October 9, 2024.

• Jurisdiction: Nevada District Court

  • Case Number: 3:25-cv-00239
  • Plaintiff(s): Not specified in the provided patent text. A general search for this case number in the Nevada District Court did not immediately identify the specific patent litigation details but rather other types of cases.
  • Defendant(s): Not specified in the provided patent text.
  • Filing Date: Not specified in the provided patent text. A general search for this case number did not provide a specific filing date for a patent case related to US10697398.
  • Outcome/Current Status: Not specified in the provided patent text or search results.

• Jurisdiction: Nevada District Court

  • Case Number: 2:25-cv-00844
  • Plaintiff(s): Not specified in the provided patent text. A general search for this case number in the Nevada District Court did not immediately identify the specific patent litigation details but rather other types of cases.
  • Defendant(s): Not specified in the provided patent text.
  • Filing Date: Not specified in the provided patent text. A general search for this case number did not provide a specific filing date for a patent case related to US10697398.
  • Outcome/Current Status: Not specified in the provided patent text or search results.

• Jurisdiction: California Central District Court

  • Case Number: 2:24-cv-08722
  • Plaintiff(s): Harbor Freight Tools USA, Inc.
  • Defendant(s): Champion Power Equipment, Inc.
  • Filing Date: October 9, 2024
  • Outcome/Current Status: Ongoing. This is a declaratory judgment action filed by Harbor Freight. The Central District of California denied a defendant's (Champion's) motion to dismiss or transfer, ruling in favor of the first-filed declaratory judgment action.

• Jurisdiction: Arizona District Court

  • Case Number: 2:23-cv-02371
  • Plaintiff(s): Champion Power Equipment Incorporated
  • Defendant(s): Firman Power Equipment Incorporated
  • Filing Date: November 10, 2023
  • Outcome/Current Status: Ongoing. Champion initiated this patent infringement action alleging various claims involving 10 patents. The court granted Firman's motion for leave to amend its invalidity contentions in February 2025. Documents indicate ongoing activity as of November 2025.

Proceedings overview

One active Inter Partes Review (IPR) proceeding, IPR2025-01271, is on file for US patent 10697398. This proceeding is currently in the "Trial Instituted" stage, indicating that a challenge to the patent's claims has been found sufficiently compelling to proceed to a full review. As trial has been instituted, the patent is under active examination for validity at the PTAB.

IPR2025-01271 — Generac Power Systems Inc. et al. v. Champion Power Equipment Inc.

• Type: Inter Partes Review
• Filed: 2025-09-03
• Status: Trial Instituted (The PTAB has decided to initiate a trial to review the patentability of the challenged claims)
• Judge panel: Information not publicly available in search results.
• Petition grounds: Specific claims challenged, prior art references, and statutory bases (§ 102 / § 103) for this particular IPR are not explicitly detailed in the provided search results. However, Generac Power Systems, Inc. (the petitioner) has asserted counterclaims of invalidity against Champion Power Equipment, Inc.'s multi-fuel patents in related district court litigation.
• Institution decision: Instituted. The exact date of institution for IPR2025-01271 is not explicitly stated in the search results, but the proceeding's status indicates that institution occurred. The USPTO Director John Squires has, since October 20, 2025, personally determined whether to institute IPR and PGR proceedings, often issuing summary notices without detailed reasoning, particularly for cases referred for merits consideration after surviving discretionary review.
• Final Written Decision (if issued): Not yet issued. The proceeding is in the "Trial Instituted" stage, with a last modified date of 2026-04-30. A Final Written Decision is typically due within one year of the institution date (35 U.S.C. § 316(a)(11)).
• Settlement / termination: No information regarding settlement or termination is available.
• Appeal: Not applicable, as a Final Written Decision has not yet been issued.
• Defensive value: This active IPR means that the validity of certain claims of US10697398 is currently being challenged at the PTAB. While no claims have been invalidated yet, the institution of trial suggests that Generac has presented a sufficient challenge to at least some claims. A defendant facing assertion of this patent should monitor this proceeding closely, as a successful IPR could lead to cancellation of claims and significantly weaken the patent owner's position.

Strategic summary

Currently, US10697398 has claims under review in one active IPR, IPR2025-01271, filed by Generac Power Systems Inc. et al. As the proceeding is still in the "Trial Instituted" phase, no claims have been canceled or sustained by a Final Written Decision. Therefore, all claims of US10697398 remain untested by a final PTAB decision. It is worth noting that Generac has also been involved in other IPRs against Champion Power Equipment (e.g., IPR2025-00805 and IPR2025-00951), where institution was denied by the Director due to inconsistent claim construction positions taken by Generac in parallel district court litigation. This indicates a persistent effort by Generac to challenge Champion's multi-fuel patents.

Regarding estoppel, since no Final Written Decision has been issued for IPR2025-01271, no estoppel has yet attached under § 315(e)(2). However, if Generac (or a privy) were to receive a Final Written Decision in this IPR, they would be estopped from asserting in other forums any ground that was raised or reasonably could have been raised during the IPR with respect to the claims challenged. For other potential defendants, this IPR proceeding, regardless of its outcome, provides insight into the prior art and invalidity arguments that Generac considers strong.

The pattern of litigation indicates that Champion Power Equipment Inc. is actively asserting its multi-fuel generator patents, including US10697398, against competitors like Generac Power Systems Inc.. Generac's multiple IPR filings, even with some denials on discretionary grounds, signal aggressive defensive maneuvers against Champion's patent portfolio. The PTAB Director's increasing involvement in institution decisions, as seen in the denials for related IPRs IPR2025-00805 and IPR2025-00951, highlights the growing importance of discretionary factors and consistency in claim construction positions when pursuing IPRs.

Recommended next steps

For a defendant facing assertion of US10697398:

• Monitor IPR2025-01271 closely: As the proceeding is "Trial Instituted," it is critical to track its progress. The PTAB has a statutory deadline of one year from institution to issue a Final Written Decision (FWD). Once the institution decision date is known, the FWD due date can be calculated. The outcome of this IPR could significantly impact the strength of US10697398. Review the public docket for IPR2025-01271 on the USPTO PTAB E2E portal for filed documents, including the petition, patent owner response, and institution decision.
• Analyze petition grounds (when available): Understand the specific claims challenged in IPR2025-01271, the prior art asserted, and the statutory grounds (§ 102/§ 103). This will provide insight into the patent's vulnerabilities and the types of invalidity arguments that the PTAB found persuasive enough for institution.
• Consider discretionary denial arguments: Given the Director's recent practice of denying institution based on discretionary factors, particularly "take-and-see" approaches or inconsistent claim construction arguments across forums (as seen in Generac's other IPRs against Champion patents), any new IPR petitions should carefully address these potential pitfalls.
• Evaluate remaining claims: If the IPR results in the cancellation of some claims, focus your defensive strategy on the invalidated claims and consider the implications for any infringement theories based on them. If claims are sustained, it indicates a hardened patent, making future IPR challenges more difficult for those in privity with the petitioner.

Inventors

• Kendall J. Collie: Likely Champion Power Equipment Inc. or affiliate at time of filing.
• Mark J. Sarder: Likely Champion Power Equipment Inc. or affiliate at time of filing.
• Aleko D. Sotiriades: Likely Champion Power Equipment Inc. or affiliate at time of filing.
• James J. Dehn: Likely Champion Power Equipment Inc. or affiliate at time of filing.
• Leigh Jenison: Likely Champion Power Equipment Inc. or affiliate at time of filing.
• Hiroaki Sato: Likely Champion Power Equipment Inc. or affiliate at time of filing.

All inventors assigned their interest to Champion Engine Technology, LLC on the same day the application was filed (2015-10-28), and Champion Engine Technology, LLC subsequently assigned the patent to Champion Power Equipment, Inc. This is a common practice for employees to assign their intellectual property to their employer or a related holding company.

Original Assignee

Champion Power Equipment Inc.

• Product Embodiment: Yes, Champion Power Equipment Inc. is a known manufacturer of dual fuel generators, which directly embody the claims of US10697398 "Batteryless dual fuel engine with liquid fuel cut-off".
• Primary Line of Business: Design, manufacture, and sale of power equipment, including generators, pressure washers, log splitters, and engines.
• Current Status: Operating.

Assignment timeline

• 2015-10-28 (executed) / recorded 2016-01-20 — Reel 039217/0111

  • Conveyance: Assignment
  • Assignor: COLLIE, KENDALL J.; DEHN, JAMES J.; JENISON, LEIGH; SARDER, MARK J.; SATO, HIROAKI; SOTIRIADES, ALEKO D. (all inventors)
  • Assignee: CHAMPION ENGINE TECHNOLOGY, LLC
  • Correspondent: Jeffrey D. Myers, MYERS AND CHEEK LLP, 1600 WEST 38TH STREET, SUITE 300, AUSTIN, TEXAS 78731. This correspondent recurs in this chain.
  • Context: Transfer of inventor rights to an IP holding or subsidiary entity.

• 2018-11-20 (executed) / recorded 2018-11-29 — Reel 044732/0112

  • Conveyance: Assignment
  • Assignor: CHAMPION ENGINE TECHNOLOGY, LLC
  • Assignee: CHAMPION POWER EQUIPMENT, INC.
  • Correspondent: Jeffrey D. Myers, MYERS AND CHEEK LLP, 1600 WEST 38TH STREET, SUITE 300, AUSTIN, TEXAS 78731. This correspondent recurs in this chain.
  • Context: Internal reorganization, transferring ownership from an IP holding entity back to the operating parent company.

Timeline diagram

timeline
    title Ownership of US 10697398
    2015 : Application filed
         : Inventors assigned to Champion Engine Tech LLC
    2018 : Champion Engine Tech assigned to Champion Power Equip Inc
    2020 : Patent issued
    2023 : First litigation filed
    2025 : PTAB case IPR2025-01271 filed

NPE / troll-pattern signals

1. Shell-entity transfer — Unclear. The transfer from inventors to "CHAMPION ENGINE TECHNOLOGY, LLC" (Reel 039217/0111) is to an LLC, which could be a shell. However, the subsequent transfer back to the operating company, Champion Power Equipment, Inc. (Reel 044732/0112), suggests it functions more as an internal IP holding entity rather than a typical NPE shell designed for assertion.
2. Known asserter in the chain — Not present. No entities known as high-frequency NPE plaintiffs appear in the assignment chain.
3. Repeat correspondent across the chain — Present. Jeffrey D. Myers of MYERS AND CHEEK LLP is listed as the correspondent for both assignments: Reel 039217/0111 (recorded 2016-01-20) and Reel 044732/0112 (recorded 2018-11-29).
4. Cascading transfers — Not present. There are two transfers, but they are separated by several years (2015-2018), not within a short 24-month window.
5. Pre-litigation transfer — Not present. The patent was issued on 2020-06-30. The last assignment was recorded on 2018-11-29. Google Patents lists the earliest litigation in 2023, well over six months after the last transfer and patent issuance.
6. Bankruptcy fire-sale — Not present. No evidence of bankruptcy for any assignor in the chain.
7. Privateering — Not present. The transfers appear to be internal to the Champion corporate family, not to a third-party NPE.
8. Defensive aggregator (anti-NPE) — Not present. The chain does not terminate at a known defensive aggregator.

Verdict

Operating-company assertion

The patent is currently assigned to Champion Power Equipment, Inc., a company that manufactures and sells products directly embodying the claimed invention. While there was an initial transfer to an LLC, the subsequent transfer back to the operating company and the presence of ongoing litigation (including PTAB challenges) indicate that Champion Power Equipment, Inc. is actively asserting this patent to protect its market position against competitors.

For verification of assignment records, please visit: https://assignmentcenter.uspto.gov/

To identify the most relevant prior art for US patent 10697398, I will examine the "References Cited" section from the patent document itself on Google Patents.

Upon reviewing US Patent 10697398 on Google Patents (https://patents.google.com/patent/[US10697398](/patent/US10697398)/en), the following prior art references are cited:

US Patent Documents:

1. US2909153A

   • Full Citation: US2909153A, Carburetor with fuel cutoff.
   • Publication/Filing Date: Published: Oct 20, 1959. Filed: Oct 26, 1956.
   • Brief Description: This patent describes a carburetor featuring a fuel cutoff mechanism designed to prevent fuel dribbling after the engine is shut off. It includes a solenoid-operated valve that can stop fuel flow to the idle passage.
   • Potential Anticipated Claims (35 U.S.C. § 102): This patent potentially anticipates aspects of Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off) and Claim 2 (Batteryless Dual Fuel Generator with Fuel Shutoff), specifically regarding a liquid fuel cut-off/shutoff mechanism within a carburetor to interrupt liquid fuel flow. The solenoid-operated valve is a form of fuel cut-off. It may also anticipate Claim 4 (Method of Assembling a Dual Fuel Engine) concerning the attachment of a liquid fuel cut-off to a carburetor.

2. US3955543A

   • Full Citation: US3955543A, Carburetor with idle fuel cut-off.
   • Publication/Filing Date: Published: May 11, 1976. Filed: May 17, 1974.
   • Brief Description: This patent describes an idle fuel cut-off mechanism for a carburetor. The mechanism typically involves a solenoid valve that blocks the idle fuel passage when the ignition is turned off, preventing engine run-on (dieseling).
   • Potential Anticipated Claims (35 U.S.C. § 102): Similar to US2909153A, this patent potentially anticipates elements of Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off) and Claim 2 (Batteryless Dual Fuel Generator with Fuel Shutoff) by disclosing a fuel cut-off for liquid fuel in a carburetor. The method described in Claim 4 (Method of Assembling a Dual Fuel Engine), involving attaching a liquid fuel cut-off, could also be anticipated.

3. US4295450A

   • Full Citation: US4295450A, Automatic fuel shut-off.
   • Publication/Filing Date: Published: Oct 20, 1981. Filed: Sep 17, 1979.
   • Brief Description: This patent relates to an automatic fuel shut-off system for internal combustion engines, often used in lawnmowers or other small engines, to stop fuel flow when the engine is not running or during an event like tipping.
   • Potential Anticipated Claims (35 U.S.C. § 102): This reference is broad in its scope of a "fuel shut-off." It could potentially anticipate the general concept of a fuel shutoff for liquid fuel as described in Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off), Claim 2 (Batteryless Dual Fuel Generator with Fuel Shutoff), and the method step in Claim 4 (Method of Assembling a Dual Fuel Engine).

4. US4364350A

   • Full Citation: US4364350A, Fuel supply system for internal combustion engines.
   • Publication/Filing Date: Published: Dec 21, 1982. Filed: Sep 29, 1980.
   • Brief Description: This patent describes a fuel supply system for internal combustion engines, particularly focusing on preventing fuel leakage when the engine is stopped. It includes a valve arrangement for controlling fuel flow.
   • Potential Anticipated Claims (35 U.S.C. § 102): This reference, like the others, generally discloses a system to control liquid fuel flow and prevent leakage, potentially anticipating the broad concept of a liquid fuel cut-off/shutoff in Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off), Claim 2 (Batteryless Dual Fuel Generator with Fuel Shutoff), and the method step in Claim 4 (Method of Assembling a Dual Fuel Engine).

5. US4643154A

   • Full Citation: US4643154A, Fuel control system for dual fuel engine.
   • Publication/Filing Date: Published: Feb 17, 1987. Filed: Dec 11, 1984.
   • Brief Description: This patent specifically addresses a fuel control system for a dual fuel engine capable of running on liquid or gaseous fuel. It includes mechanisms for switching between fuels and controlling their delivery.
   • Potential Anticipated Claims (35 U.S.C. § 102): This is highly relevant as it explicitly covers a "dual fuel engine." It directly anticipates the core elements of Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off) including an engine operable on gaseous and liquid fuel and a switch to change operation. The concept of a liquid fuel cut-off when switching to gaseous fuel would be a key aspect of such a system. It also impacts Claim 4 (Method of Assembling a Dual Fuel Engine), particularly the steps of providing a dual fuel engine and coupling a switch.

6. US4682570A

   • Full Citation: US4682570A, Fuel control system for dual fuel engines.
   • Publication/Filing Date: Published: Jul 28, 1987. Filed: Jan 2, 1986.
   • Brief Description: This patent describes a fuel control system for an internal combustion engine capable of operating on either gasoline or liquefied petroleum gas (LPG). It includes a mechanism to prevent both fuels from being supplied simultaneously and ensures proper fuel flow during transitions.
   • Potential Anticipated Claims (35 U.S.C. § 102): This is also highly relevant due to its focus on "dual fuel engines" and preventing simultaneous fuel supply. It anticipates elements of Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off) regarding a dual fuel engine, a switch to change operation, and a liquid fuel cut-off to prevent overly rich conditions during changeover. It also impacts Claim 4 (Method of Assembling a Dual Fuel Engine).

7. US5167215A

   • Full Citation: US5167215A, Fuel system for dual fuel engine.
   • Publication/Filing Date: Published: Dec 1, 1992. Filed: Mar 2, 1992.
   • Brief Description: This patent details a fuel system for a dual fuel engine, specifically for operating on both liquid and gaseous fuels. It describes valves and controls for managing the flow of each fuel type.
   • Potential Anticipated Claims (35 U.S.C. § 102): As another dual fuel engine system, this patent strongly anticipates the foundational aspects of Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off) and the corresponding method steps in Claim 4 (Method of Assembling a Dual Fuel Engine). The specific control of liquid fuel flow during dual-fuel operation would be central to its teaching.

8. US5293847A

   • Full Citation: US5293847A, Dual fuel system with fuel selection logic.
   • Publication/Filing Date: Published: Mar 15, 1994. Filed: Sep 20, 1993.
   • Brief Description: This patent discloses a dual fuel system that uses electronic logic to control the selection and supply of either liquid or gaseous fuel to an internal combustion engine.
   • Potential Anticipated Claims (35 U.S.C. § 102): This reference is very strong for anticipating Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off) due to its explicit mention of a "dual fuel system with fuel selection logic" and the control of fuel supply. The concept of a liquid fuel cut-off upon selection of gaseous fuel would be inherently present in a system designed to prevent simultaneous fuel delivery. The method of assembly in Claim 4 (Method of Assembling a Dual Fuel Engine) is also strongly impacted.

9. US6547662B2

   • Full Citation: US6547662B2, Combination gas and liquid fuel carburetor.
   • Publication/Filing Date: Published: Apr 15, 2003. Filed: Dec 20, 2000.
   • Brief Description: This patent describes a carburetor designed to handle both gaseous and liquid fuels. It includes a mechanism for switching between the two fuel types.
   • Potential Anticipated Claims (35 U.S.C. § 102): This directly relates to the carburetor aspect of the invention. It could anticipate the carburetor described in Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off), Claim 2 (Batteryless Dual Fuel Generator with Fuel Shutoff), and Claim 3 (Carburetor with Non-Linear Fuel Shutoff) if its switching mechanism involves a non-linear fuel shutoff. It also impacts the carburetor attachment steps in Claim 4 (Method of Assembling a Dual Fuel Engine).

10. US6976458B2

    • Full Citation: US6976458B2, Carburetor fuel shut-off valve and system.
    • Publication/Filing Date: Published: Dec 20, 2005. Filed: Nov 25, 2002.
    • Brief Description: This patent describes a fuel shut-off valve for a carburetor, intended to control fuel flow, often to prevent problems like engine run-on.
    • Potential Anticipated Claims (35 U.S.C. § 102): This reference directly teaches a "carburetor fuel shut-off valve," making it relevant for Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off), Claim 2 (Batteryless Dual Fuel Generator with Fuel Shutoff), and Claim 3 (Carburetor with Non-Linear Fuel Shutoff) if the valve operates without linear motion. It also impacts the method step of attaching a liquid fuel cut-off in Claim 4 (Method of Assembling a Dual Fuel Engine).

11. US8895058B2

    • Full Citation: US8895058B2, Fuel cut-off system for a dual fuel engine.
    • Publication/Filing Date: Published: Nov 25, 2014. Filed: May 23, 2012.
    • Brief Description: This patent is highly relevant, specifically disclosing a "fuel cut-off system for a dual fuel engine." It aims to prevent simultaneous fuel delivery and manage transitions between liquid and gaseous fuels.
    • Potential Anticipated Claims (35 U.S.C. § 102): This patent directly and strongly anticipates Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off) by describing a fuel cut-off system for a dual fuel engine that interrupts liquid fuel upon switching. It also highly anticipates aspects of Claim 2 (Batteryless Dual Fuel Generator with Fuel Shutoff) and the method described in Claim 4 (Method of Assembling a Dual Fuel Engine).

12. US20130008407A1

    • Full Citation: US20130008407A1, Two-fuel engine, particularly for an electrical power generator.
    • Publication/Filing Date: Published: Jan 10, 2013. Filed: Jul 9, 2012.
    • Brief Description: This application describes a two-fuel engine, particularly for an electrical power generator, with a system for switching between liquid and gaseous fuels.
    • Potential Anticipated Claims (35 U.S.C. § 102): This is very relevant as it describes a two-fuel engine for a generator. It strongly anticipates Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off) and Claim 2 (Batteryless Dual Fuel Generator with Fuel Shutoff), particularly the components relating to a dual-fuel engine in a generator context and the mechanism for switching fuels. The method in Claim 4 (Method of Assembling a Dual Fuel Engine) is also directly impacted.

13. US20140130768A1

    • Full Citation: US20140130768A1, Fuel cut-off system for a dual fuel engine.
    • Publication/Filing Date: Published: May 15, 2014. Filed: Nov 12, 2013.
    • Brief Description: This patent application describes a fuel cut-off system specifically for a dual fuel engine, aiming to prevent both fuels from being supplied simultaneously and managing fuel transitions.
    • Potential Anticipated Claims (35 U.S.C. § 102): This is another highly relevant reference that directly discloses a "fuel cut-off system for a dual fuel engine." It strongly anticipates Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off), Claim 2 (Batteryless Dual Fuel Generator with Fuel Shutoff), and the method described in Claim 4 (Method of Assembling a Dual Fuel Engine).

14. US20150363099A1

    • Full Citation: US20150363099A1, Dual fuel generator with a remote fuel regulator.
    • Publication/Filing Date: Published: Dec 17, 2015. Filed: Jun 12, 2015.
    • Brief Description: This patent application describes a dual fuel generator with a remote fuel regulator. It covers systems for delivering and regulating both liquid and gaseous fuels.
    • Potential Anticipated Claims (35 U.S.C. § 102): This reference is the immediate parent application (continuation-in-part of U.S. patent application Ser. No. 14/738,060, filed Jun. 12, 2015, which is US20150363099A1). Therefore, it discloses much of the same subject matter. It directly anticipates Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off), Claim 2 (Batteryless Dual Fuel Generator with Fuel Shutoff), and Claim 4 (Method of Assembling a Dual Fuel Engine). Any differences would likely be in the specifics of the liquid fuel cut-off mechanism, which might be further developed in US10697398B2.

Foreign Patent Documents (Example):

1. JP2004245136A
   • Full Citation: JP2004245136A, DUAL FUEL ENGINE.
   • Publication/Filing Date: Published: Sep 2, 2004. Filed: Feb 18, 2003.
   • Brief Description: This Japanese patent application describes a dual fuel engine.
   • Potential Anticipated Claims (35 U.S.C. § 102): This broadly anticipates Claim 1 (Dual Fuel Engine with Liquid Fuel Cut-off) as it relates to the concept of a dual fuel engine. Specific details would be needed to assess anticipation of the liquid fuel cut-off.

Most Relevant Prior Art:

The most relevant prior art documents under 35 U.S.C. § 102 appear to be those that explicitly address dual fuel engines and fuel cut-off systems for such engines, especially in the context of switching between fuels and preventing simultaneous delivery. These directly overlap with the core inventive concepts of US10697398B2.

Therefore, the following U.S. patent documents are considered most relevant:

• US4643154A (Fuel control system for dual fuel engine)
• US4682570A (Fuel control system for dual fuel engines)
• US5167215A (Fuel system for dual fuel engine)
• US5293847A (Dual fuel system with fuel selection logic)
• US8895058B2 (Fuel cut-off system for a dual fuel engine)
• US20130008407A1 (Two-fuel engine, particularly for an electrical power generator)
• US20140130768A1 (Fuel cut-off system for a dual fuel engine)
• US20150363099A1 (Dual fuel generator with a remote fuel regulator)

These references, particularly US8895058B2, US20130008407A1, and US20140130768A1, specifically teach systems and methods for fuel cut-off in dual fuel engines and generators, directly addressing the central problem and solution presented in US10697398B2. US20150363099A1 is particularly relevant as it is the parent application. The other cited U.S. patents like US6547662B2 and US6976458B2 also contribute to the understanding of prior art related to dual fuel carburetors and fuel shut-off valves in general.

I must first address a critical limitation for performing an obviousness analysis under 35 U.S.C. § 103. The provided "Prior art section" in the patent text for US10697398 lists only "Prior art keywords" (fuel, carburetor, engine, dual, shaft) and a "Prior art date" (2015-06-12). It does not provide specific prior art references (e.g., patent numbers, publications) that were cited during examination or are otherwise available in the provided text for analysis.

A proper obviousness analysis requires identifying specific prior art documents and explaining how a Person Having Ordinary Skill in the Art (PHOSITA) would have been motivated to combine them to arrive at the claimed invention. Since no specific references are provided in the authoritative text, I cannot identify concrete "combinations of prior art references" as requested.

Therefore, this analysis will proceed by hypothetically discussing how a PHOSITA might have combined known elements in the field, consistent with the provided keywords and the problems the patent aims to solve, if such elements were found in relevant prior art documents existing before the priority date of 2015-06-12. This discussion is necessarily conceptual due to the absence of specific references.

Obviousness Analysis (Conceptual, due to lack of specific prior art references)

The independent claims of US10697398 generally pertain to dual fuel engines and generators, specifically focusing on mechanisms to manage liquid fuel flow (cut-off/shutoff) when switching between liquid and gaseous fuels, particularly in a batteryless pull-start context.

Relevant Areas of Prior Art (based on "Prior art keywords"):
A PHOSITA in the field of small internal combustion engines, particularly for generators, before June 12, 2015, would have been familiar with:

• Dual fuel engines/carburetors: The concept of engines operating on both liquid and gaseous fuels (like gasoline and LPG/propane) was well-known.
• Carburetors: The basic design and function of carburetors, including float bowls, throats, fuel passages, main nozzles, and idle circuits, were standard.
• Fuel control mechanisms: Various valves, solenoids, and switches for controlling fuel flow (both liquid and gaseous) were common.
• Engine starting systems: Pull-start (recoil) engines and associated electrical generation (magnetos, alternators with charge windings) were prevalent for batteryless applications like portable generators.

Hypothetical Combinations and Motivation for PHOSITA:

Given the problems identified in the patent's background (overly rich air-fuel ratio, hard starting, unstable operation, delay in switching, gum/varnish deposits from gasoline, after-fire, engine flooding), a PHOSITA would have been motivated to combine known elements to address these issues.

For Independent Claim 1: Dual Fuel Engine with Liquid Fuel Cut-off

• Core elements: Engine operable on gaseous/liquid fuel, carburetor, switch to change fuel, liquid fuel cut-off upon switching to gaseous fuel.
• Hypothetical Combination: A PHOSITA, observing existing dual-fuel engines that often experienced issues with simultaneous fuel delivery or "overly rich air-fuel ratio when both fuels are simultaneously engaged during cross-over switching" [Description, 0005], would be motivated to add a liquid fuel cut-off mechanism to a known dual-fuel engine system.
• Motivation: The motivation would be to prevent "engine flooding by stopping liquid fuel flow when starting on gaseous fuel" [Description, 0039] and to ensure cleaner, more reliable operation when running on gaseous fuel by eliminating residual liquid fuel supply. Basic fuel shut-off valves or solenoids were common in various fuel systems. Implementing such a shut-off, synchronized with a fuel selection switch (which was also known in dual-fuel systems), would be a logical step to improve functionality and address the identified problems.

For Independent Claim 2: Batteryless Dual Fuel Generator with Fuel Shutoff

• Core elements: Batteryless pull-start engine, alternator, carburetor with float bowl/fuel passage, fuel shutoff attached to carburetor to close liquid fuel passage upon selection of gaseous fuel.
• Hypothetical Combination: Building upon the motivation to prevent liquid fuel issues in dual-fuel systems, a PHOSITA would consider applying a liquid fuel cut-off to a batteryless generator. The challenge in a batteryless system is powering such a cut-off if it's electrical (like a solenoid). Prior art likely included various solenoid-operated fuel valves. If a solenoid valve was chosen, a PHOSITA would recognize the need for power. The patent states that "Fuel cut solenoid 74 is preferably powered by a magneto 76, alternator, engine flywheel with a charge winding, or other electrical power generator having a charge winding or coil 78" [Description, 0042]. Tying such a solenoid to the existing electrical generation system (magneto/alternator for spark/charging) of a pull-start engine would be a straightforward engineering solution, even if requiring "Additional turns can be added to a charging coil... to increase the output voltage" [Description, 0045] or "solenoid windings... can be modified to operate at lower voltages" [Description, 0046] to function at low RPMs during starting.
• Motivation: The motivation is to extend the benefits of a liquid fuel cut-off (preventing flooding, improving starting on gaseous fuel, reducing emissions/after-fire [Description, 0064]) to portable, batteryless generators, which often operate in situations where clean, reliable starts on alternative fuels are desirable. Using the engine's inherent power generation (magneto/alternator) for this control would be a common design choice to maintain the "batteryless" characteristic.

For Independent Claim 3: Carburetor with Non-Linear Fuel Shutoff

• Core elements: Carburetor with float bowl, throat, fuel passage; fuel shutoff with first end in carburetor (actuates to close fuel passage), second end external (to actuate first end); fuel shutoff actuates free from linear motion.
• Hypothetical Combination: Prior art would include various types of valves (e.g., gate valves, ball valves, rotary valves) for controlling fluid flow. While many fuel shut-offs operate linearly (e.g., plunger-type solenoids), a PHOSITA designing a compact and reliable seal within a carburetor's float bowl would recognize the advantages of rotary motion. The patent explicitly states that a "rotating valve such as manual fuel shutoff 110, reduces the likelihood that fuel will leak from carburetor 62" [Description, 0092].
• Motivation: The motivation to implement a non-linear (e.g., rotary) fuel shutoff, as described by a "valve tip 180 (e.g., oval or stadium shape) rotates parallel to inlet 174 of fuel passage 164" [Description, 0075, 0076, 0079], would be to achieve improved sealing and reduced leakage compared to linear plunger-type valves, particularly when sealing against a flat surface within the float bowl. Rotary valves were well-known in fluid control, and adapting one to a carburetor's fuel passage to achieve a robust seal without linear movement (which can cause wear on O-rings and lead to leaks over time) would be a design choice driven by reliability and manufacturing considerations. Using "polyoxymethylene (POM) or other thermoplastic material" for the valve tip [Description, 0108] for sealing is also a known material selection for such applications.

For Independent Claim 4: Method of Assembling a Dual Fuel Engine

• Core elements: Providing an engine, attaching a carburetor (with throat, float bowl, fuel passage), coupling gaseous fuel source to throat, liquid fuel source to float bowl, coupling a switch to change fuel, attaching liquid fuel cut-off to carburetor to close fuel passage upon switching from liquid to gaseous fuel.
• Hypothetical Combination: This claim describes a method that essentially formalizes the assembly of the systems described in Claims 1 and 2. The steps involved (attaching carburetors, connecting fuel lines, installing switches, and integrating fuel cut-offs) would be standard assembly practices for any engine or generator manufacturer. The specific step of "attaching a liquid fuel cut-off to the carburetor to close the fuel passage upon actuation of the switch from liquid fuel to gaseous fuel" [Description, 0021] directly corresponds to the functional features discussed above.
• Motivation: The motivation for such an assembly method would be to build a dual-fuel engine that overcomes the operational difficulties associated with simpler dual-fuel systems lacking precise liquid fuel control during transition. The method steps reflect the engineering solutions a PHOSITA would arrive at to create a reliable and user-friendly dual-fuel system, addressing the problems of fuel mixing, hard starting, and emissions.

In summary, while specific prior art documents are unavailable for this analysis, the general concepts of dual-fuel engines, carburetors, various fuel control mechanisms, and batteryless engine power generation were well-established before the priority date of US10697398. A PHOSITA, motivated to solve known problems of inefficient fuel switching, engine flooding, and emissions in dual-fuel systems, particularly in batteryless applications, would have a logical basis to combine these existing technological elements to arrive at the claimed inventions. The specific implementation of a rotating fuel cut-off would be a design choice driven by known advantages of rotary valves for sealing and reliability.