Obviousness

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.