GB2518235A

GB2518235A - Cable raceway

Info

Publication number: GB2518235A
Application number: GB1316484.3A
Authority: GB
Inventors: Jack Blanchard; Andreas Yiasoumi; Alan R Bennett
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2013-09-17
Filing date: 2013-09-17
Publication date: 2015-03-18
Anticipated expiration: 2033-09-17
Also published as: GB2518235B; GB201316484D0

Abstract

A cable raceway for use in an aircraft comprises an elongate, electrically conductive body 11 and an electrically conductive cover 16. The cover is in electrical contact with the body when secured thereto and has a plurality of apertures such that fluid, such as air, may flow through it. The cover may be a mesh, and may be metallic with an insulating anti-chafe coating 20. The cover may be electrically connected to the body through fasteners (21, Fig 4), or may include integral fastening portions (24, 23, Fig 5). One cover may span, and electrically connect, two such bodies. The cover allows ventilation while providing protection from electromagnetic hazards.

Description

CABLE RACEWAY

Technical Field

This specification relates to a raceway for retaining cables and, in particular, a raceway for electrical and communication cables and wiring for use in an aircraft.

Background

Raceways are used in aircraft for retaining cables and generally comprise elongate aluminium components comprising one or more channels in which the cables are io retained. The raceway serves the purpose of guiding and securing the cables and protecting the cables from mechanical damage.

To enable the loading of the raceway with cables and for subsequent maintenance or repairs to the cables, the channels of the raceway are generally U-shaped and include i. one open face. In the event of an electrical short circuit between two or more cabks within a raceway, or between a cable and the body of the raceway, which may be accompanied by intense electrical arcing, large amounts of thermal and electrical energy can be released which can escape the raceway channels with the resulting risk of damage to the adjacent elements. Such an electrical short circuit may cause electromagnetic interference to be emitted which may be detrimental to electrical se]lsitive circuits or systems. In addition, external electromagnetic hazards (EMH) can enter the channels through the open face, which includes various electrical interferences and threats such as electromagnetic interference (EMI), electromagnetic coupling (EMC) and radio frequency interference (RFI).

Summary

In this specification there are described embodiments of a cable raceway for use in an aircraft comprising A cable raceway for use in an aircraft comprising an elongate, electrically conductive body having at least one channel with an open face along its length, and an electrically conductive cover securable to the body to cover the open elongate face of the channel, the cover being in electrical contact with the body when secured thereto and having a plurality of apertures such that fluid may flow through the cover from the at least one channel.

The cover may comprise a mesh. The cover may be coated with an anti-chafe material.

The cover maybe metaflic. The cover may comprise an expanded metaflic sheet. The cover may comprise expanded copper foil.

The cover may comprise material with a weight of between 10 g/m2 -1000 g/m2, and may be between 30 g/m2 -900 g/m2, and may be between 75 g/m -1000 g/m2.

The cover maybe secured to the body by a plurality of electrically conductive fasteners.

to The body may include a non-conductive coating.

The body may comprise a plurality of first coupling elements, and the cover may comprise a plurality of second coupling elements, wherein the first and second coupling elements may be releasably engageable to secure the cover to the body.

The first coupling elements may be in electrical contact with the electrically conductive material of the body, and the second coupling elements may be in electrical contact with the electrically conductive material of the cover, such that when the cover is secured to the body, the cover and body may be in dectrica] contact.

The body may comprise a first raceway body, and the cable raceway may further comprise a second body as defined above disposed adjacent the first body but spaced therefrom to define a gap therebetween, and an electrically conductive cover, having a plurality of apertures such that fluid may flow through the cover, in electrical contact with the first and second bodies and spanning the gap between the first and second bodies.

The cover securable to the first body may be one and the same cover that spans the gap between the first and second bodies and may be in contact with the second body.

The cover that spans the gap between the first and second bodies and is in contact with the first and second bodies maybe a separate cover to the cover which is securabk to the first body.

Brief description of the drawings

Embodiments of the present invention will now be described, by way of examp'e on'y, with reference to figures 2 to 5 of the accompanying drawings, in which: Figure 1 shows a perspective view of a convention& caNe raceway for use in an aircraft; Figure 2 shows a perspective view of a cable raceway of a first embodiment of the invention with a cover detached; Figure 3 shows the cable raceway of figure 2 with the cover attached and with a power line disposed proximate thereto; Figure 4 shows an enlarged perspective view of a portion of the cable raceway of figures 2and3;and Figure 5 shows a perspective view of a cab'e raceway of a second embodiment of the invention with a cover detached.

Detailed description

Figure 1 shows a perspective view of a known configuration of cable raceway 2 for use in an aircraft 1 comprising a plurality of U-shaped channàls 3 for containing a plurality of cables 4. The channe's 3 of the raceway 2 are open along one faces to enable the cab'es 4 to be fitted into the chann&s 3 and also for ease of access to the caNes and/or raceway mounting points within the chann&s 3 for subsequent maintenance or repairs.

However, the raceway 2 having open channels 3 presents an issue of EMH entering the channels as well as exiting the channels and damaging or interfering with the cables 4 therein. Furthermore, any short circuit between two or more cables within the raceway 2, or between a cable and the raceway itself, can result in arge amounts of thermal and e1ectrica energy which can escape from the raceway channe' and risk damaging adjacent electrical elements and/or emitting EMH which maybe detrimental to electrically sensitive systems.

Figures 2 to 4 show a raceway 10 according to a first embodiment of the present invcntion for use in an aircraft 1, comprising mi clongate alumiiium body ii having a o phiraBty of channels 12 formed therein to retain a phiraBty of cables 13. Each of the chann&s 12 has an open face 14 to aflow the cables to be loaded into the chann&s. The raceway body 11 is secured to the aircraft structure 5, for examp'e to a eading or trailing edge of a wing or the aircraft fusdage. The raceway body 11 is aTho preferably in dectrica conductive contact with the aircraft structure 5 to which it is secured. This may be by means of conductive fasteners such as metallic bolis 6, or by other electrically conductive connectors between the metallic raceway body 11 and the aircraft structure 5 or the aircraft current return network.

The raceway body ii includes a nylon coating 15. This non-conductive coating i acts to mitigate the risk of abrasion and arcing between the metallic raceway body 11 and cables 13 within the channels 12 which may become damaged such than the inner core within the protective cable sleeves are exposed. Therefore, the raceway body 11 may comprise a coating of another non-conductive other than nylon.

to The raceway 10 further comprises an elongate cover 16 which is generally U-shaped in cross-section and has an upper face 17 and side faces i8, 19 depending from the elongate edges of the upper face 17. The cover i6 is made of an electrically conductive material and may be formed of a metallic mesh or of an expanded metallic mesh, for example expanded copper foil (ECF). The cover 16 is configured to sit over the raceway body ii with the side faces i8, 19 lying along the outer edges of the raceway body ii and the upper face 17 lying across the open faces 14 of the raceway channels 12, thereby closing the raceway channels 12.

The cover 16 may have an anti-chafe coating 20, such as a rubber, nylon, PVC, polymer or other plastic coating. In normal circumstances, the cables 13 should be secured in place within the channels 12 and not free to move around. However, if one or more fasteners securing the cables 13 in place is damaged or comes loose, the anti-chafe coating 20 on the cover 16 is intended to mitigate the risk of cables 13 becoming damaged during movement of the aircraft if the cables 13 within the channels 12 impact against the cover 16. The coating is also preferably non-conductive to prevent a short circuit and arcing between damaged cables 13 within the channels 12 and the cover 16, or between any adjacent power lines 22 and the cover 16. The anti-chafe coating 20 is preferably lightweight, resilient, and resistant to impacts.

The cover 16 is secured to the raceway body ii by means of fastenings 21, for examp'e, nut and boft mechanical fastenings with washers, such that the cover 16 is fastened in electrically conductively contact wfth the raceway body ii. The mechanical fastenings 21 may be electrically conductive, for example, metallic, thereby providing an electrically conductive connection between the metallic raceway body ii underneath the non-conductive coating 15, and the body of the cover 16 underneath the anti-chafe coating 20 (which may also be dectricafly non-conductive).

In addition, or as an akemative to the mechanica' fasteners 21 being electricafly conductive, the anti-chafe coating 20 may be removed at certain points along the side faces 18, 19 of the cover 16, and the non-conductive coating 15 on the raceway body ii may also be removed at corresponding points, so that the underlying body of the cover i6 is in electrical contact with the underlying metallic raceway body 11 so that the raceway body ii and cover i6 are in eectrica1 contact, prior to application of any protective over-sealing paint or varnish that may subsequently me applied.

to The cover 16 serves to reduce the EMH entering the channels 12 of the raceway 10 from external sources by providing electrical shiekling completely surrounding the cables 13 within the channels 12 (i.e. the raceway ii and cover i6 together completely surround the cables 13) and connection to the aircraft current return structure or network. The conductive nature of the cover 16 renders it effective in achieving this function as it is i dectricafly bonded to the greater metallic dement that is the raceway body ii, which itself, is in electrical conductive contact with the aircraft structure or network 5.

Therefore, EMH incident upon the cover i6 is conducted away from the cables and is diverted through the cover 16, to the raceway body ii and to the aircraft structure 5 where it wUl have no appreciable effect on the cables 13 or any other nearby dectricafly sensitive systems and circuits, thereby protecting these elements.

Further advantages of the open mesh structure of the cover 16 are that it enables thermal energy which may result in a raceway in the event of an electrical short circuit and resulting arcing, to be dissipated from within the channels 12, thus mitigating damage to adjacent elements and systems. A mesh structure is advantageous in this respect because of the particularly open structure which offers little or no resistance to fluid flow through the apertures of the mesh, allowing free flow of fluid therethrough.

If a solid cover was used in place of the open structure cover 16, such thermal energy from an arcing event would be contaiicd within the channcs 12, the force and concentration of which could cause significant damage to the cables 13 and surrounding systems. Also, the raceways are often ocated in parts of the aircraft structure which may be exposed to harsh environmenta' conditions, such as the eading and trailing wing edges. The channeTh 12 within the raceway 11 may therefore be exposed to wind, rain, dirt and dust, and so the open structure of the cover 16 permits water to drain out of the channels 12 through the cover 16, and foreign objects such as dire and dust to be flushed out of the chann&s 12. Yet further, an open structure such as a mesh has a high strength to weight ratio due to the relatively little amount of mesh material per unit area of the stnicture. This is beneficial as minimising of weight in aircraft apphcations is particulariy important as it impacts many factors such as fuàl efficiency and the required structure strength that supports such components. Expanded mesh structures, such as ECF, are advantageous as the material is particularly uniform across its surface area due to efficiency and accuracy of the manufacturing technique, which essentially involves punching a sheet material at spaced locations and stretching the material to open it out into an open mesh structure. This technique is also material efficient as there is little or no wastage.

A further advantage of providing the electrically conductive shielding cover i6 over the open faces 14 of the channels 12 is that it enable the distance D (see figure 3) between the raceway 10 and an electrical power line 22 to be decreased to less than a distance that would otherwise be permissible if the raceway 10 did not have a cover 16. Space within aircraft structures, such as within wings and fusethges, for power and communication lines and other necessary components is very limited, and such elements need to be mounted in the most space-efficient manner possible. However, for safety reasons, minimum "safety segregation distances" exist between &ectric& power and generation routes and raceways -that is, the minimum distance power lines carrying currents over a threshold value must be spaced from raceways to minimise the risk of arcing or EMH. Furthermore, in modern aircraft electrical systems, higher voltages are being increasingly used for greater electrical efficiency, but higher voltages result in greater arcing and EMH risk, meaning increased safety segregation distances are required. However, by providing a conductive shielding cover 16, protection against arcing and the effects of EMH on the raceway 10 are reduced and so the safety segregation distances are reduced, enabling more space-efficient mounting of components within the aircraft structure A further advantage of the cover 16 is that, in an arcing event, it can manage the arcing energy that may be produced from the electrical power line 22 or in the raceway chann& 12 by burning or oxidising. That is, as the arcing energy travels through the cover 16, the cover 16 can act as a sacrificial material and oxidises or burns, using up the arcing energy and reducing the remaining arcing energy that is to be conducted through the raceway body 11 to the aircraft structure 5. This reduces effects such as s charring at the mechanical fasteners 21 holding the cover 16 to the raceway body ii which could weaken the fasteners 21. The configuration of the cover 16, such as the density of the mesh and/or its thickness, or the wire gauge of the mesh, can be optimised to achieve this sacrificial effect between the extremes of too much damage to the cover 16 being sustained, and too much ener being conducted to the raceway body ii with insufficient energy absorption by the cover 16. Exemplary cover materials which may be acceptable are for expanded copper foil mesh covers having a weight of between 10 g/m2 -1000 g/m2.

A raceway 30 of a second embodiment of the invention is shown in Figure 5, and is similar to the first embodiment of raceway 10 described above. Like features retain the to same reference numerals and a detailed description of these will not be repeated. A difference between the raceway 30 of the second embodiment and that of the first is that the cover i6 is not fastened to the raceway body by separate fasteners 21. Instead, the raceway body ii includes a plurality of female couplings 23 on the outside surface of its side walls, and the cover 16 includes a plurality of correspondingly positioned male couplings 24 protecting from the side faces 18, 19. The male couplings 24 are configured to releasably engage with the female couplings 23 to retain the cover i6 in position on the raceway body ii. Furthermore, the female couplings 23 do not include the non-conductive coating 15 that covers the rest of the raceway body ii.

Furthermore, the male couplings 24 do not include the anti-chafe coating that is disposed over the rest of the cover 16. Therefore, when the cover 16 is secured to the raceway body ii, the male and female couplings are in electrically conductive contact and serve to provide the electrical contact points between the raceway body ii and the cover 16.

It will be appreciated that in the second embodiment of raceway 30 described above, the respective location of the male and female couplings 23, 24 may be reversed within the scope of the invention.

Although thc embodiments of the invention described above comprise a cover having a mesh structure, the invention is not Bmited to such configuration and the cover may equay comprise planar panels for its respective faces, wherein at east one of the panels comprises a p'urality of apertures therethrough to allow fluid to flow through the cover between the channels 12 and ambient atmosphere, for the reasons explained above.

It should be appreciated that the cover i6 in the embodiments described above also act to divert high intensity radiated fields (HIRF) and any LMH from lightning strikes away from the cables within the raceway ii to the aircraft bonding network.

The cover 16 is described in the above embodiments as covering the channels 12 of a raceway body 11. However, within aircraft structure, cables 13 have to run in non-linear routes and so a plurality of sections of raceway 10 are often required, and there are therefore inevitably gaps between the raceway sections where the cable routes change direction. In such embodiments, the cover 16 could extend beyond the distal ends of to the raceway body ii and span over the gap to the adjacent raceway body 11 to make electrical contact therewith, and electrically connect the adjacent raceway bodies ii.

This can prevent arcing over a gap between adjacent raceways 10 if a short-circuit or arc event occurs in one raceway 10. Furthermore, rather than a single cover extending over one raceway body ii and onto an adjacent raceway body 11, a separate section of cover 16 can be used to span the gap between adjacent raceway bodies ii and be in electrical contact with both, as described above.

Claims

Claims 1. A cable raceway for use in an aircraft comprising an elongate, dectrically conductive body having at least one channel with an open face along its length, and an electrically conductive cover securable to the body to cover the open elongate face of the channel, the cover being in electrical contact with the body when secured thereto and having a plurality of apertures such that fluid may flow through the cover from the at least one channel.
2. A cable raceway according to claim 1 wherein the cover comprises a mesh.
3. A cable raceway according to claim 1 or claim 2 wherein the cover is coated with an anti-chafe material.
4. A cable raceway according to any of daims ito 3 wherein the cover is metallic.
5. A cable raceway according to any of claims i to 4 wherein the cover comprises an expanded metallic sheet.
6. A cable raceway according to claim 5 wherein the cover comprises expanded copper foil.
7. A cable raceway according to any preceding claim wherein the cover comprises material with a weight of between 10 g/m2 -1000 g/m2.
8. A cable raceway according to any preceding claim wherein the cover is secured to the body by a plurality of electrically conductive fasteners.
9. A cabk raceway according to any preceding claim wherein thc body indudes a non-conductive coating.to. A cable raceway according to anypreceding daim wherein the body comprises a plurality of first couphng elements, and the cover comprises a plurality of second coupling elements, wherein the first and second coupbng dements are rdeasably s engageable to secure the cover to the body. -10-ii. A cable raceway according to claim 10 wherein the first coupling elements are in electrical contact with the electrically conductive material of the body, and the second coupling elements are in electrical contact with the electrically conductive materia' of the cover, such that when the cover is secured to the body, the cover and body are in electrical contact.12. A cable raceway according to any preceding claim, the body comprising a first raceway body, the cable raceway further comprising a second body as defined in any preceding claim disposed adjacent the first body but spaced therefrom to define a gap therebetween, and an electrically conductive cover, having a plurality of apertures such that fluid may flow through the cover, in electrical contact with the first and second bodies and spanning the gap between the first and second bodies.13. A cable raceway according to claim 12 wherein the cover secLirable to the first body is one and the same cover that spans the gap between the first and second bodies and is in contact with the second body.14. A cable raceway according to claim 12 wherein the cover that spans the gap between the first and second bodies and is in contact with the first and second bodies is a separate cover to the cover which is securable to the first body.