Patent Description:
In some aircraft, the aircraft fuel tanks have an irregular shape. The fuel tanks therefore typically comprise a plurality of segments defined by segment walls, or panels. The panels may extend substantially vertically between the top of the wing and the bottom of the wing. For example, in some aircraft the fuel tanks are located in the aircraft wings and are positioned around other equipment located in the wing.

Some other equipment, for example located in the wing, may be connected to the fuselage of the aircraft via pipes that pass through the aircraft fuel tank. In some instances, the pipes pass through the panels of the fuel tank. For example, the pipes may carry hydraulic fluid from a hydraulic supply to a hydraulic actuator. In some instances, the pipes must pass through the segment walls. <CIT> and <CIT> each disclose devices for isolating a tube from a wall through which the tube passes.

A first aspect of the present invention provides an isolation system for an aircraft fuel tank, as claimed in claim <NUM>.

Optionally, the first attachment points comprise a counterbore extending from the second side of the isolator to the first side of the isolator, wherein the wider end of the counterbore extends from the second side of the isolator.

Optionally, the first attachment points are positioned around the aperture to align with corresponding panel apertures in the panel.

Optionally, the second attachment points comprise a counterbore extending from the first side of the isolator to the second side of the isolator, wherein the wider end of the counterbore extends from the first side of the isolator.

Optionally, the second attachment points are positioned around the aperture to align with corresponding fitting apertures in a pipe fitting fixed to the pipe.

Optionally, the isolator comprises a groove on the first side and/or the second side of the isolator, the groove extending around the outer wall of the aperture and configured to receive a seal.

Optionally, the isolator is formed from a chemically inert material.

A second aspect of the present invention provides a method according to claim <NUM>.

Optionally, the method comprises: rigidly attaching the isolator to the pipe fitting with an electrically-conductive first fastener, electrically insulating the first fastener from the panel, rigidly attaching the isolator to the panel with an electrically-conductive second fastener, and electrically insulating the second fastener from the pipe.

Optionally, the method comprises providing a seal between the isolator and the panel. Optionally, the seal is a liquid gasket.

A third aspect of the present invention provides an aircraft comprising: an isolation system according to the first aspect of the present invention.

There can be a build-up of static electricity in an aircraft fuel tank, and/or the aircraft may be struck by lightning. In some aircraft, the panels and the pipes comprise or are formed from an electrically conductive material and may therefore carry an electrical current. Accordingly, it can be beneficial to isolate a panel from a pipe to prevent an electrical current from passing between the panel and pipe.

<FIG> shows an isometric view of an isolator <NUM> according to embodiments of the present invention. The isolator <NUM> is for an aircraft fuel tank and is configured to separate an electrically conductive internal panel of the fuel tank from an electrically conductive pipe that passes through the panel.

The isolator <NUM> comprises a plurality of first attachment points <NUM> for attaching the isolator <NUM> to the panel, a plurality of second attachment points <NUM> for attaching the isolator <NUM> to the pipe, and an aperture <NUM> defined by an outer wall <NUM> and extending from a first side <NUM> of the isolator <NUM> to a second side <NUM> of the isolator <NUM>. The aperture <NUM> is configured to receive the pipe in use.

The outer wall <NUM> of the aperture <NUM> extends outwardly from the first side <NUM> of the isolator <NUM> to form a tube. The tube is configured to pass through the panel in use. In some embodiments, the outer wall <NUM> extends from the first side <NUM> of the isolator <NUM> by a distance that is greater than a thickness of the panel. The length of the tube is greater than a thickness of the isolator <NUM>. That is, the length of the tube is greater than the distance between the first side <NUM> of the isolator <NUM> and the second side <NUM> of the isolator <NUM>.

The plurality of first attachment points <NUM> and the plurality of second attachment points <NUM> are positioned on a flange <NUM> extending from the outer wall <NUM> of the aperture <NUM>. The flange <NUM> may define the first side <NUM> and the second side <NUM> of the isolator <NUM>. The flange <NUM> of the isolator <NUM> shown in <FIG> is chamfered around the first and second attachment points <NUM>, <NUM>. This can help to reduce the size and therefore weight of the isolator <NUM>.

In some embodiments, the first attachment points <NUM> are configured to receive a fastener (not shown) for fastening the isolator to the panel and/or the second attachment points <NUM> may be configured to receive a fastener (not shown) for fastening the isolator to the pipe.

In some embodiments, the first attachment points <NUM> are positioned around the aperture <NUM> to align with corresponding panel apertures in the panel (not shown). In some embodiments, the second attachment points <NUM> are positioned around the aperture <NUM> to align with corresponding fitting apertures in a pipe fitting fixed to the pipe (not shown). The isolator <NUM> shown in <FIG> has three first attachment points <NUM> each at a first radial distance from the aperture <NUM> and three second attachment points <NUM> each at a second radial distance from the aperture <NUM>. In some embodiments, the first and the second radial distance are the same.

The isolator comprises two or more first attachment points <NUM>. The isolator comprises two or more second attachment points <NUM>. The isolator <NUM> shown in <FIG> has first attachment points <NUM> alternately spaced between the second attachment points <NUM> so that the attachment points <NUM>, <NUM> are equally spaced around the aperture <NUM>. This configuration can help to evenly distribute the load through the isolator <NUM> in use, thus helping to reduce the stresses on the isolator <NUM> in use.

In some embodiments, the first attachment points <NUM> are oriented in an opposite direction to the second attachment points <NUM>. Each of the first attachment points <NUM> of the isolator <NUM> shown in <FIG> comprises a first counterbore extending from a wider end of the first counterbore at the second side <NUM> of the isolator <NUM> to a thinner end of the first counterbore at the first side <NUM> of the isolator <NUM>. Each of the second attachment points <NUM> of the isolator <NUM> shown in <FIG> comprise a second counterbore extending from a wider end of the second counterbore at the first side <NUM> of the isolator <NUM> to a thinner end of the second counterbore at the second side <NUM> of the isolator <NUM>. The wider end <NUM> of the counterbore extends from the first side <NUM> of the isolator <NUM>. In some embodiments, the thinner end of the first and/or second counterbores is threaded and configured to receive a corresponding threaded bolt.

In other embodiments, the first attachment points <NUM> and/or the second attachment points <NUM> may be any other shape suitable for attaching the isolator <NUM> to the panel and the pipe, respectively.

The isolator <NUM> shown in <FIG> comprises a first groove <NUM> on the first side <NUM> of the isolator <NUM>. The first groove <NUM> extends around the outer wall <NUM> of the aperture <NUM> and is configured to receive a first seal (not shown). In other embodiments, the first groove <NUM> may be omitted. In some embodiments, the isolator <NUM> comprises a second groove <NUM> (as shown in <FIG>) on the second side <NUM> of the isolator <NUM>. The second groove <NUM> extends around the aperture <NUM> and is configured to receive a second seal. In other embodiments, the second groove <NUM> may be omitted. In use, the first and second seals may help to prevent fuel from passing from one side of the panel to another and may help to further isolate the panel from the pipe.

The isolator <NUM> comprises a non-electrically conductive material. In some embodiments, the non-electrically conductive material does not react to aircraft fuel or hydraulic fluid. Such a material helps to prevent premature degradation of the isolator <NUM> in use, and may help to prevent contamination of the fuel due to degradation of the isolator <NUM>. In some embodiments, the isolator <NUM> comprises another material that is coated by the non-electrically conductive material. In other embodiments, the isolator <NUM> is formed from only the non-electrically conductive material, for example the isolator <NUM> is machined from a block of the non-electrically conductive material or the isolator <NUM> is moulded from the non-electrically conductive material. In some embodiments, the isolator <NUM> comprises a single part. In other embodiments, the isolator <NUM> is formed from two or more parts rigidly fixed together, for example by a mechanical fastening or by chemical means such as an adhesive. In some embodiments, the isolator <NUM> is formed from a chemically inert material, for example nylon.

<FIG> shows a schematic cross-sectional view of an isolation system <NUM> according to embodiments of the present invention. The isolation system <NUM> comprises an isolator <NUM> according to embodiments of the present invention, for example the isolator <NUM> shown in <FIG>. The isolation system <NUM> further comprises a plurality of first bolts <NUM> and a plurality of second bolts <NUM>. Each bolt of the plurality of first bolts <NUM> is positioned in the counterbore of a respective one of the plurality of first attachments <NUM> of the isolator <NUM>. Each bolt of the plurality of second bolts <NUM> is positioned in the counterbore of a respective one of the plurality of second attachments <NUM> of the isolator <NUM>. Each of the plurality of plurality of first bolts <NUM> is held in position by a respective first nut <NUM>. Each of the plurality of second bolts <NUM> is held in position by a respective second nut <NUM>.

<FIG> shows the isolation system <NUM> in use. That is, the isolator <NUM> is positioned in an aircraft fuel tank. The isolator <NUM> is fastened to a pipe fitting <NUM>, through which a pipe <NUM> passes, by the plurality of second bolts <NUM>. In this embodiment, the pipe fitting <NUM> and the pipe <NUM> are electrically conductive. The outer wall <NUM> of the isolator <NUM> extends through an isolator aperture <NUM> of a panel <NUM>. The panel <NUM> extends through the aircraft fuel tank. The isolator <NUM> is fastened to the panel <NUM> by the plurality of first bolts <NUM>. In some embodiments, the panel <NUM> is an internal wall of the fuel tank and a different isolator is used at an intersection between the pipe <NUM> and an external wall of the fuel tank.

As can be seen in <FIG>, the outer wall <NUM> of the isolator <NUM> is positioned between the panel <NUM> and the pipe fitting <NUM> in use. In some embodiments, such as embodiments in which the pipe fitting <NUM> is electrically conductive, the outer wall <NUM> is configured to extend from the first side <NUM> of the isolator <NUM> by a distance that exceeds the width of the panel <NUM> and by an additional distance that prevents an electrical arc (see dashed line <NUM> in <FIG>, for example) forming between the panel <NUM> and the pipe fitting <NUM> or the pipe <NUM>. In some embodiments, the flange <NUM> of the isolator <NUM> has a thickness that is sufficient to help prevent an electrical arc (see dashed line <NUM> in <FIG>, for example) forming between the pipe panel <NUM> and the pipe fitting <NUM>.

The first attachment points <NUM> are positioned on the flange <NUM> of the isolator <NUM> to align with corresponding panel apertures <NUM> in the panel <NUM>. The second attachment points <NUM> are positioned on the flange <NUM> of the isolator <NUM> to align with corresponding fitting apertures <NUM> in the pipe fitting <NUM>. In some embodiments, the isolator <NUM> is configured such that the first attachments points <NUM> are at a radial distance from the outer wall <NUM> that is sufficient to help prevent an electrical arc forming between the plurality of first bolts <NUM> and the pipe fitting <NUM> or the pipe <NUM> (see dashed line <NUM> in <FIG>, for example).

When the plurality of first and second bolts <NUM>, <NUM> are positioned in their respective counterbores, respective voids <NUM>, <NUM> are formed around the head of each bolt. In some embodiments, at least one of the plurality of first and second bolts <NUM>, <NUM> are electrically-conductive. In such embodiments, the system <NUM> comprises a non-electrically conductive sealant (not shown) covering the head of the at least one of the plurality of first and second bolts <NUM>, <NUM> to seal the head of each bolt in its respective counterbore. In some embodiments, the sealant fills the void <NUM>, <NUM>. In some embodiments, the sealant is formed from a chemically inert material. In use, the sealant helps to prevent an electrical arc (see dashed line <NUM> in <FIG>, for example) forming between the first bolts <NUM> and the pipe <NUM> and/or the pipe fitting <NUM> and between the second bolts <NUM> and the panel <NUM>.

The isolation system <NUM> shown in <FIG> comprises an isolator <NUM> comprising a first groove <NUM> on the first side <NUM> of the isolator <NUM> and around the outer wall <NUM>. The isolation system <NUM> comprises a first seal <NUM> located in the first groove <NUM> of the isolator <NUM>. The first seal <NUM> surrounds the outer wall <NUM> of the isolator <NUM>. By way of example only, the first seal <NUM> is an O-ring. In use, as shown in <FIG>, the first seal <NUM> is positioned between the isolator <NUM> and the panel <NUM>. The first seal <NUM> further helps to isolate the panel <NUM> from the pipe <NUM>. The first seal <NUM> may also help to prevent leakage of fuel through the panel aperture <NUM>.

In some embodiments, the isolation system <NUM> comprises an isolator <NUM> that does not comprise the first groove <NUM>. In such embodiments, a liquid sealant or liquid gasket (not shown) may be provided between the panel <NUM> and the first side <NUM> of the isolator <NUM>. The liquid sealant further helps to isolate the panel <NUM> from the pipe <NUM>.

The isolation system <NUM> shown in <FIG> comprises an isolator <NUM> comprising a second groove <NUM> on the second side <NUM> of the isolator <NUM> and around the aperture <NUM>. The isolation system <NUM> comprises a second seal <NUM> located in the second groove <NUM> of the isolator <NUM>. The second seal <NUM> surrounds the aperture <NUM> on the second side <NUM> of the isolator <NUM>. By way of example only, the second seal <NUM> is an O-ring. In use, as shown in <FIG>, the second seal <NUM> is positioned between the isolator <NUM> and pipe fitting <NUM>. The second seal <NUM> further helps to isolate the panel <NUM> from the pipe <NUM>. The second seal <NUM> may also help to prevent leakage of fuel through the panel aperture <NUM>.

In some embodiments, the isolation system <NUM> comprises an isolator <NUM> that does not comprise the second groove <NUM>. In such embodiments, a liquid sealant or liquid gasket (not shown) may be provided between the pipe fitting <NUM> and the second side <NUM> of the isolator <NUM>. The liquid sealant further helps to isolate the panel <NUM> from the pipe <NUM>.

<FIG> shows a flow diagram of a method <NUM> of isolating an electrically conductive internal panel or an aircraft fuel tank from an electrically conductive pipe that passes through the panel, according to embodiments of the present invention. The method <NUM> comprises: passing <NUM> the pipe through a tube of a non-electrically conductive material isolator, passing <NUM> the tube through an aperture in the panel, rigidly attaching <NUM> the isolator to a pipe fitting fixed to the pipe, and rigidly attaching <NUM> the isolator to the panel.

In some embodiments, the isolator is an isolator <NUM> according to embodiments of the present invention.

In some embodiments, the rigidly attaching <NUM> comprises removably rigidly attaching the isolator to the pipe fitting fixed to the pipe. In some embodiments, the rigidly attaching <NUM> comprises removably rigidly attaching the isolator to the panel. For example, the isolator may be attached to the pipe fitting and the panel by fasteners.

In some embodiments, the rigidly attaching <NUM> comprises rigidly attaching the isolator to the pipe fitting with an electrically-conductive first fastener and the method comprises electrically insulating <NUM> the first fastener from the panel. In some embodiments, the rigidly attaching <NUM> comprises rigidly attaching the isolator to the panel with an electrically-conductive second fastener and the method comprises electrically insulating <NUM> the second fastener from the pipe. In some embodiments, the electrical insulating <NUM>, <NUM> may be achieved by providing a non-electrically conductive sealant over the first and second fasteners.

In some embodiments, the method comprises providing <NUM> a seal between the isolator and the panel. In some embodiments, the seal may be provided in a groove of the isolator, for example the first and/or second grooves <NUM>, <NUM> of the isolator <NUM> shown in <FIG>. In other embodiments, the seal may be a liquid gasket between a surface of the panel and an adjacent surface of the isolator and/or between a surface of the pipe fitting and the isolator.

<FIG> shows a schematic top view of an aircraft <NUM> according to embodiments of the present invention. The aircraft <NUM> comprises a fuselage <NUM> and wings <NUM>. In some embodiments, the wings <NUM> are formed from a non-electrically conductive material, for example carbon composite. In some embodiments, the wings <NUM> are formed from a non-electrically conductive material, for example carbon composite. In other aircraft, wings are formed from an electrically-conductive material and may not require an isolator according to the present invention because the wings themselves may dissipate an electrical current.

In some embodiments, an aircraft fuel tank is located in the wings <NUM>. In some embodiments, the aircraft <NUM> comprises one or more isolators <NUM> according to the present invention. In some embodiments, the one or more isolators <NUM> are located in the aircraft fuel tank, the one or more isolators <NUM> being fixed one or more respective internal panels <NUM> of the aircraft fuel tank. In some embodiments, the aircraft <NUM> comprises one or more isolation systems <NUM> according to embodiments of the present invention. The one or more isolation systems <NUM> being fixed to one or more respective internal panels <NUM> of the aircraft fuel tank.

It is to noted that the term "or" as used herein is to be interpreted to mean "and/or", unless expressly stated otherwise.

Claim 1:
An isolation system for an aircraft fuel tank, the isolation system configured to separate an electrically conductive internal panel (<NUM>) of the fuel tank from an electrically conductive pipe (<NUM>) that passes through the panel, the isolation system comprising:
a pipe fitting (<NUM>) configured, in use, to receive the pipe; and
an isolator (<NUM>) configured, in use, to pass through the panel, the isolator comprising:
an aperture (<NUM>) defined by an outer wall (<NUM>) and extending from a first side (<NUM>) of the isolator to a second side (<NUM>) of the isolator, the aperture configured to receive the pipe fitting in use, and
a flange (<NUM>) extending from the outer wall of the aperture and on which are positioned a plurality of first attachment points (<NUM>) for attaching the isolator to the panel,
wherein the isolator comprises a non-electrically conductive material, and
characterised in that a plurality of second attachment points (<NUM>) for attaching the isolator to the pipe fitting are positioned on the flange.