Patent Description:
Installation of electrically conductive materials in a fuel tank requires significant design detail and consideration to minimize a possibility of an electrical discharge within the fuel tank. Historically, non-metallic conductors such as carbon loaded plastics and foams have been widely used for shielding and anti-static applications. When exposed to transient electric fields these materials are resistant to the high current flows and sparks that would ignite fuels. Additionally, fuel tanks are confined spaces and excitation wires and return signal wires connected to fuel level sensing probes inside a fuel tank need to be configured to prevent electromagnetic interference.

<CIT> describes, in accordance with its abstract, a system for power and data communications within a fuel tank and across a wall of the fuel tank and includes a fuel height sensor and a sealed connector extending through a wall of a fuel tank. The system also includes an electric power connection between the fuel height sensor and the sealed connector. The system additionally includes an internal data communications connection between the fuel height sensor and the sealed connector, wherein the electric power connection comprises a resistive non-metallic wire.

The invention to which this European patent relates is defined in the appended claims.

In accordance with an example, a system includes a fuel level sensing probe inside a fuel tank. The system also includes an exciter wire bundle configured to electrically connect the fuel level sensing probe to an electric power source outside the fuel tank. The exciter wire bundle includes an excitation wire and a grounded guard wire. The excitation wire and the grounded guard wire each include a resistive non-metallic wire. The system also includes a return signal wire bundle configured to electrically connect the fuel level sensing probe to a device configured to measure a quantity of fuel within the fuel tank by using a return signal from the fuel level sensing probe. The return signal wire bundle includes a return signal wire and a grounded guard wire. The grounded guard wire of the return signal wire bundle and the grounded guard wire of the exciter wire bundle are configured to shield the return signal wire from electromagnetic interference. The return signal wire and the grounded guard wire each comprise a resistive non-metallic wire.

In accordance with another example, a vehicle includes a fuel tank and a system for measuring a quantity of fuel in the fuel tank. The system includes a fuel level sensing probe inside the fuel tank. The system also includes an exciter wire bundle configured to electrically connect the fuel level sensing probe to an electric power source outside the fuel tank. The exciter wire bundle includes an excitation wire and a grounded guard wire. The excitation wire and the grounded guard wire includes a resistive non-metallic wire. The system further includes a return signal wire bundle configured to electrically connect the fuel level sensing probe to a device configured to measure a quantity of fuel within the fuel tank by using a return signal from the fuel level sensing probe. The return signal wire bundle includes a return signal wire and a grounded guard wire. The grounded guard wire of the return signal wire bundle and the grounded guard wire of the exciter wire bundle are configured to shield the return signal wire from electromagnetic interference. The return signal wire and the grounded guard wire comprise a resistive non-metallic wire.

In accordance with another example, a method includes providing one or more fuel level sensing probes inside a fuel tank. The method also includes providing an exciter wire bundle configured to electrically connect the fuel level sensing probe to an electric power source outside the fuel tank. The exciter wire bundle includes an excitation wire and a grounded guard wire. The excitation wire and the grounded guard wire comprise a resistive non-metallic wire. The method also includes providing a return signal wire bundle configured to electrically connect the fuel level sensing probe to a device configured to measure a quantity of fuel within the fuel tank by using a return signal from the fuel level sensing probe. The return signal wire bundle includes a return signal wire and a grounded guard wire. The grounded guard wire of the return signal wire bundle and the grounded guard wire of the exciter wire bundle are configured to shield the return signal wire from electromagnetic interference. The return signal wire and the grounded guard wire comprise a resistive non-metallic wire.

In accordance with an example and any of the preceding examples, the system, vehicle or method further include a plurality of fuel level sensing probes disposed at predetermined different locations within the fuel tank to accurately measure the quantity of fuel within the fuel tank. The exciter wire bundle includes a plurality of excitation wires and one or more grounded guard wires. Each excitation wire is electrically connected to a respective one of the plurality of fuel level sensing probes. The return signal wire bundle includes a plurality of return signal wires and one or more grounded guard wires. Each return signal wire is electrically connected to a respective one of the plurality of fuel level sensing probes.

The following detailed description of examples refers to the accompanying drawings, which illustrate specific examples of the disclosure. Other examples having different structures and operations do not depart from the scope of the present disclosure. Like reference numerals may refer to the same element or component in the different drawings.

In accordance with examples of the present disclosure, a system for determining or measuring a quantity of fuel in a fuel tank includes one or more fuel level sensing probes inside the fuel tank. The system also includes an exciter wire bundle configured to electrically connect each fuel level sensing probe to an electric power source outside the fuel tank. The exciter wire bundle includes an excitation wire for each fuel level sensing probe and a grounded guard wire configured to couple to the excitation wire or each excitation wire for preventing electromagnetic interference from the excitation wire or wires. The excitation wire and the grounded guard wire each includes a resistive non-metallic wire. The system additionally includes a return signal wire bundle configured to electrically connect each fuel level sensing probe to a device configured to determine or measure a quantity of fuel within the fuel tank by using a return signal from each fuel level sensing probe. The return signal wire bundle includes a return signal wire for each fuel level sensing probe and a grounded guard wire. The grounded guard wire of the return signal bundle and the grounded guard wire of the exciter wire bundle are configured to shield the return signal wire or each return signal wire from electromagnetic interference. The return signal wire and the grounded guard wire each include a resistive non-metallic wire. The grounded guard wire causes an exciter field (produced by the signal carrying wires) to couple to the grounded guard wire rather than the signal/return or return signal wires which substantially cancels the electromagnetic interference created by the exciter field. Routing a grounded guard wire in the exciter wire bundle and/or the return signal wire bundle is a simpler and less expensive means to achieve similar results to a shield between the excitation wires and the return signal wires for less cost and complexity. The exciter wire bundle and the return signal wire bundle can also be routed together with a separation of about <NUM> inches (<NUM>) with the grounded guard wires compared to at least <NUM> inches (<NUM>) without the grounded guard wires. This significantly reduces the amount of work in the confined space of a fuel tank and reduces build time for installation. In accordance with an example, a vehicle, such as an aircraft includes a system for determining or measuring the quantity of fuel in a fuel tank of the vehicle.

<FIG> is an illustration of a fuel tank <NUM> in a vehicle <NUM> and a system <NUM> for measuring or determining a quantity of fuel in the fuel tank <NUM> in accordance with an example of the present disclosure. The vehicle <NUM> in <FIG> is an aircraft and the fuel tank <NUM> is inside a wing <NUM> of the aircraft. In other examples, the fuel tank <NUM> is any tank for containing a flammable material. In some examples, e.g., an aircraft, the system <NUM> is also referred to as a fuel management system. The system <NUM> includes one or more fuel level sensing probes <NUM> inside the fuel tank <NUM>. In the example in <FIG>, where the vehicle <NUM> is an aircraft, the system <NUM> includes a plurality of fuel level sensing probes <NUM> disposed at predetermined different locations within the fuel tank <NUM> to accurately measure the quantity of fuel within the fuel tank <NUM>. An example of a fuel level sensing probe is described in more detail in <CIT>, is assigned to the same assignee as the present application.

The system <NUM> also includes an exciter wire bundle <NUM> configured to electrically connect the fuel level sensing probe <NUM> or probes <NUM> through a first sealed connector <NUM> to an electric power source <NUM> outside the fuel tank <NUM>. The exciter wire bundle <NUM> includes an excitation wire <NUM> (<FIG>) and a grounded guard wire <NUM> (<FIG>) configured to couple to the excitation wire <NUM> when energized or carrying an electrical signal to prevent electromagnetic interference from the excitation wire <NUM>. In accordance with some examples, the exciter wire bundle <NUM> includes an excitation wire <NUM> connected to each fuel level sensing probe <NUM>. The excitation wire <NUM> and the grounded guard wire <NUM> each include a resistive non-metallic wire. In accordance with an example, the resistive non-metallic wire is a carbon loaded thermoplastic, e.g., a carbon loaded polyether ether ketone (PEEK) thermoplastic. The resistive non-metallic wire includes a resistance between about <NUM> ohms/meter and about <NUM> Mega-ohms/meter.

The system <NUM> also includes a return signal wire bundle <NUM> configured to electrically connect the fuel level sensing probe <NUM> or probes <NUM> to a device <NUM>, outside the fuel tank <NUM>, configured to determine or measure a quantity of fuel within the fuel tank <NUM> by using a return signal from the fuel level sensing probe <NUM> or return signals from each of the fuel level sensing probes <NUM>. The return signal wire bundle <NUM> electrically connects the fuel level sensing probe <NUM> or probes as shown in <FIG> through a second sealed connector <NUM>. The return signal wire bundle <NUM> includes a return signal wire <NUM> (<FIG>) and a grounded guard wire <NUM> (<FIG>). The grounded guard wire <NUM> of the return signal wire bundle <NUM> and/or the grounded guard wire <NUM> of the exciter wire bundle <NUM> are configured to shield the return signal wire <NUM> from electromagnetic interference. In accordance with an example the return signal wire bundle <NUM> includes a return signal wire <NUM> from each fuel level sensing probe <NUM>. In the example in <FIG>, the device <NUM> includes a return signal interface <NUM> or receiver configured to receive the return signal from the fuel level sensing probe <NUM> or probes <NUM> to measure or determine the quantity of fuel in the fuel tank <NUM>. The return signal wire <NUM> and the grounded guard wire <NUM> each include a resistive non-metallic wire. In the example illustrated in <FIG>, the electric power source <NUM> is a component of the device <NUM> configured to measure or determine the quantity of fuel in the fuel tank <NUM>. In other examples, the electric power source <NUM> is a separate component from the device <NUM>. Examples of the device <NUM> include but are not necessarily limited to a computer, a probe reader or a data concentrator. As previously described, the system <NUM> in the example in <FIG> includes a plurality of fuel level sensing probes <NUM> disposed at predetermined different locations within the fuel tank <NUM> to accurately measure the quantity of fuel within the fuel tank <NUM>. The exciter wire bundle <NUM> includes a plurality of excitation wires <NUM> and one or more grounded guard wires <NUM> (<FIG> and <FIG>). Each excitation wire <NUM> is electrically connected to a respective one of the plurality of fuel level sensing probes <NUM>. The return signal wire bundle <NUM> includes a plurality of return signal wires <NUM> and one or more grounded guard wires <NUM>. Each return signal wire <NUM> is electrically connected to a respective one of the plurality of fuel level sensing probes <NUM>.

Referring also to <FIG> is a cross-sectional view of an exciter wire bundle <NUM> and a return signal wire bundle <NUM> taken along lines <NUM>-<NUM> in <FIG> in accordance with an example of the present disclosure. The exciter wire bundle <NUM> includes a single grounded guard wire <NUM> and a plurality of excitation wires <NUM>. In some examples, the single grounded guard wire <NUM> and the plurality of excitation wires <NUM> are twisted together to form the exciter wire bundle <NUM>. The excitation wires <NUM> couple to the single grounded guard wire <NUM> when the excitation wires <NUM> are energized or carry an electrical signal to prevent electromagnetic interference from the excitation wires <NUM>. The exciter wire bundle <NUM> also includes a jacket <NUM> of insulation material to protect the excitation wires <NUM> and the grounded guard wire <NUM>.

In the example in <FIG>, the return signal wire bundle <NUM> also includes a single grounded guard wire <NUM> and a plurality of return signal wires <NUM>. In some examples, the single grounded guard wire <NUM> and the plurality of return signal wires <NUM> are twisted together to form the return signal wire bundle <NUM> and to shield the return signal wires <NUM> from the electromagnetic interference, e.g., electromagnetic interference from the excitation wires <NUM>. The return signal wire bundle <NUM> also includes a jacket <NUM> of insulation material to protect the return signal wires <NUM> and the grounded guard wire <NUM>. The exciter wire bundle <NUM> and the return signal wire bundle <NUM> are also spaced a predetermined distance "D" apart to prevent electromagnetic interference from the exciter wire bundle <NUM> to the return signal wire bundle <NUM>. For example, the predetermined distance "D" is about <NUM> inches (<NUM>).

Referring also to <FIG> is a cross-sectional view of an exciter wire bundle <NUM> and a return signal wire bundle <NUM> taken along lines <NUM>-<NUM> in <FIG> in accordance with another example of the present disclosure. <FIG> is an illustration of an example of either the exciter wire bundle <NUM> or the return signal wire bundle <NUM> in <FIG> showing a grounded guard wire <NUM> or <NUM> twisted with each exciter wire <NUM> or return signal wire <NUM> in accordance with an example of the present disclosure. In the example in <FIG>, the exciter wire bundle <NUM> includes a plurality of grounded guard wires <NUM> and a plurality of excitation wires <NUM>. Each grounded guard wire <NUM> forms a twisted pair <NUM> with one of the plurality of excitation wires <NUM>, as illustrated in <FIG>, to form the exciter wire bundle <NUM> and to electromagnetically couple the excitation wires <NUM> to the plurality of grounded guard wires <NUM> when the excitation wires <NUM> are energized or carry an electrical signal to prevent electromagnetic interference from the excitation wires <NUM>. The exciter wire bundle <NUM> also includes a jacket <NUM> of insulation material to protect the excitation wires <NUM> and the grounded guard wires <NUM>.

In the example in <FIG>, the return signal wire bundle <NUM> includes a plurality of grounded guard wires <NUM> and a plurality of return signal wires <NUM>. Each grounded guard wire <NUM> forms a twisted pair <NUM> with one of the plurality of return signal wires <NUM> to form the return signal wire bundle <NUM>. The grounded guard wires <NUM> of the return wire bundle <NUM> and/or the grounded guard wires <NUM> of the exciter wire bundle <NUM> are configured to shield the return signal wires <NUM> from the electromagnetic interference. The return signal wire bundle <NUM> also includes a jacket <NUM> of insulation material to protect the return signal wires <NUM> and the grounded guard wires <NUM>. The exciter wire bundle <NUM> and the return signal wire bundle <NUM> are also spaced a predetermined distance "D" apart to prevent electromagnetic interference between the exciter wire bundle <NUM> and the return signal wire bundle <NUM>. For example, the predetermined distance "D" is about <NUM> inches (<NUM>).

<FIG> is a block schematic diagram of the exemplary system <NUM> in <FIG>. As previously described, the system <NUM> includes a first sealed connector <NUM> extending through a wall <NUM> of the fuel tank <NUM>. The first sealed connector <NUM> is configured to electrically connect the plurality of excitation wires <NUM> to the electrical power source. The system <NUM> also includes a second sealed connector <NUM> extending through the wall <NUM> of the fuel tank <NUM>. The second sealed connector <NUM> is configured to electrically connect the plurality of return signal wires <NUM> to the device <NUM> configured to measure the quantity of fuel within the fuel tank <NUM>. The exciter wire bundle <NUM> extends between each fuel level sensing probe <NUM> and the first sealed connector <NUM>. One of the excitation wires <NUM> and a grounded guard wire <NUM> branches off from the exciter wire bundle <NUM> to connect to each fuel level sensing probe <NUM>. The return signal wire bundle <NUM> extends between each fuel level sensing probe <NUM> and the second sealed connector <NUM>. One of the return signal wires <NUM> and a grounded guard wire <NUM> branches off from the return signal wire bundle <NUM> to connect to each fuel sensing probe <NUM>. The exciter wire bundle <NUM> electrically connects each fuel level sensing probe <NUM> to the first sealed connector <NUM> and the return signal wire bundle electrically connects each fuel sensing probe to the second sealed connector <NUM>. In some examples, at the first sealed connector <NUM>, the exciter wire bundle <NUM> transitions to metallic wiring outside of the fuel tank <NUM>, and at the second sealed connector <NUM>, the return signal wire bundle <NUM> also transitions to metallic wiring outside the fuel tank <NUM>. The first sealed connector <NUM> is configured to connect the exciter wire bundle <NUM> to an external exciter wire bundle <NUM> outside the fuel tank <NUM> and the second sealed connector <NUM> is configured to connect the return signal wire bundle <NUM> to an external return signal wire bundle <NUM> outside the fuel tank <NUM>. The external exciter wire bundle <NUM> includes a plurality of external excitation wires <NUM> and one or more external grounded guard wires <NUM> depending on whether the exciter wire bundle <NUM> inside the fuel tank <NUM> includes a single grounded guard wire <NUM> as shown in the example in <FIG> or a plurality of grounded guard wires <NUM> as shown in the example in <FIG>. In some examples, the external excitation wires <NUM> and the external grounded guard wire or wires <NUM> are a metallic conductive material such as copper. In other examples, the external excitation wires <NUM> and the external grounded guard wire or wires <NUM> are a resistive non-metallic wire. The external return signal wire bundle <NUM> includes a plurality of external return signal wires <NUM> and an external grounded guard wire or wires <NUM>. In some examples, the external return signal wires <NUM> and the external grounded guard wire or wires <NUM> are a metallic electric conductive material such as copper. In other examples, the external return signal wires <NUM> and the external grounded guard wire or wires <NUM> are a resistive non-metallic wire.

<FIG> is a block schematic diagram of an example of a system <NUM> to determine a quantity of fuel in a fuel tank in accordance with another example of the present disclosure. The system <NUM> is similar to the exemplary system <NUM> in <FIG> and <FIG> except the system <NUM> includes a single sealed connector <NUM> extending through a wall <NUM> of the fuel tank <NUM>. The sealed connector <NUM> is configured to electrically connect the plurality of excitation wires <NUM> to the electric power source <NUM> and the plurality of return signal wires <NUM> to the device <NUM> configured to measure the quantity of fuel within the fuel tank. In some examples, the external wiring outside the fuel tank <NUM> is metallic electric conductive material, such as copper.

<FIG> is a block schematic diagram of an example of a system <NUM> to determine a quantity of fuel in a fuel tank in accordance with a further example of the present disclosure. The system <NUM> is similar to the exemplary system <NUM> in <FIG> and <FIG> except the system <NUM> includes a plurality of sealed connectors 602a-602n extending through the wall <NUM> of the fuel tank <NUM>. One sealed connector <NUM> is associated with each fuel level sensing probe <NUM>. Each sealed connector 602a-602n extends through a wall <NUM> of the fuel tank <NUM> and is configured to electrically connect the excitation wire <NUM> connected to an associated fuel level sensing probe <NUM> to the electrical power source <NUM> and to electrically connect the return signal wire <NUM> connected to the associated fuel level sensing probe <NUM> to the device <NUM> configured to measure the quantity of fuel within the fuel tank <NUM>. In some examples, the external wiring outside the fuel tank <NUM> is metallic electric conductive material, such as copper.

<FIG> is an illustration of an example of a clamp assembly <NUM> configured to fasten the exciter wire bundle <NUM> and the return signal wire bundle <NUM> to a grounded structure <NUM> of the fuel tank <NUM> within the fuel tank <NUM> in accordance with an example of the present disclosure. The clamp assembly <NUM> is also configured to space the bundles <NUM> and <NUM> the predetermined distance "D" apart to prevent electromagnetic interference between the exciter wire bundle <NUM> and the return signal wire bundle <NUM>. The clamp assembly <NUM> includes a pair of P-shaped clamps 704a and 704b. Each P-shaped clamp 704a and 704b includes a pair of adjacent linear leg portions <NUM> and <NUM> at one end and a loop portion <NUM> integrally formed and extending from the leg portions <NUM> and <NUM> at an opposite end. The loop portion <NUM> is configured to receive one of the wire bundles <NUM> or <NUM>. A hole (not shown in <FIG>) is formed through the adjacent linear leg portions <NUM> and <NUM> for receiving a fastener <NUM>. The P-shaped clamps 704a and 704b are attached to the grounded fuel tank structure <NUM> with the loop portions <NUM> of the P-shaped clamps 704a and 704b opposite one another to provide the predetermined distance "D" between the exciter wire bundle <NUM> and the return signal wire bundle <NUM>.

<FIG> is a flow chart of an example of a method <NUM> for monitoring a quantity of fuel in a fuel tank in accordance with an example of the present disclosure. In block <NUM>, the method includes providing one or more fuel level sensing probes inside the fuel tank. In accordance with an example, the fuel level sensing probes are similar to the fuel level sensing probes <NUM> in <FIG>.

In block <NUM>, the method <NUM> includes providing an exciter wire bundle configured to electrically connect the fuel level sensing probe or probes to an electric power source outside the fuel tank. In some examples, the exciter wire bundle is similar to the excited wire bundle <NUM> described with reference to <FIG>. The exciter wire bundle includes an excitation wire or wires and a grounded guard wire or wires configured to prevent electromagnetic interference from the excitation wire or wires. Each excitation wire and the grounded guard wire includes a resistive non-metallic wire.

In block <NUM>, the method <NUM> includes providing a return signal wire bundle configured to electrically connect the fuel level sensing probe or probes to a device configured to determine or measure a quantity of fuel within the fuel tank by using a return signal from each fuel level sensing probe. In some examples, the return signal wire bundle is the same or similar to the return signal wire bundle <NUM> described with reference to <FIG>. The return signal wire bundle includes a return signal wire or wires and a grounded guard wire or wires configured to shield the return signal wire or wires from electromagnetic interference. Each return signal wire and grounded guard wire includes a resistive non-metallic wire.

In block <NUM>, the method <NUM> includes transmitting fuel level data from each fuel level sensing probe to a device configured to measure or determine a quantity of fuel in the fuel tank.

In block <NUM>, the method <NUM> includes generating a fuel quantity indication by a fuel management system based on fuel height or fuel level in the tank.

In block <NUM>, the method <NUM> includes presenting the fuel quantity indication to an operator of the vehicle or system. In an example where the vehicle is an aircraft, the fuel quantity indication is presented on a display in a cockpit of the aircraft to a pilot.

The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various examples of the present disclosure.

The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting of examples of the disclosure. It will be further understood that the terms "include," "includes," "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present examples has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to examples in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope of examples.

Claim 1:
A system (<NUM>, <NUM>, <NUM>), comprising:
a fuel level sensing probe (<NUM>) inside a fuel tank (<NUM>);
an exciter wire bundle (<NUM>) configured to electrically connect the fuel level sensing probe (<NUM>) to an electric power source (<NUM>) outside the fuel tank (<NUM>), wherein the exciter wire bundle (<NUM>) comprises an excitation wire (<NUM>) and a grounded guard wire (<NUM>), and wherein the excitation wire (<NUM>) and the grounded guard wire (<NUM>) each comprise a resistive non-metallic wire; and
a return signal wire bundle (<NUM>) configured to electrically connect the fuel level sensing probe (<NUM>) to a device (<NUM>) configured to measure a quantity of fuel within the fuel tank (<NUM>) by using a return signal from the fuel level sensing probe (<NUM>), wherein the return signal wire bundle (<NUM>) comprises a return signal wire (<NUM>) and a grounded guard wire (<NUM>), and wherein the grounded guard wire (<NUM>) of the return signal wire bundle (<NUM>) and the grounded guard wire (<NUM>) of the exciter wire bundle (<NUM>) are configured to shield the return signal wire (<NUM>) from electromagnetic interference, and wherein the return signal wire (<NUM>) and the grounded guard wire (<NUM>) each comprise a resistive non-metallic wire.