Abstract:
A cable-raceway providing electromagnetic shielding has rectangular channels defined by longitudinal-folds of a tape which comprises mesh having a warp of bare wires running lengthwise and a weft of a single, bare-wire. Metal brackets support it with the base of each bracket extending transversely under the raceway. The channels nest between arms upstanding from the base, and a plastic insert fits over the tape to enhance electrical contact between the mesh and bracket for electrical ground-bonding of the raceway. The insert provides teeth down the walls of each channel for engagement by cable-retainers to push them down into the channels for retaining underlying cables. Further support in the channels is provided by plastic straps that extend under the raceway and to which the channels are secured using inserts and cable-retainers corresponding to the inserts and retainers. One face of the mesh is covered by an electrically-insulating sheet.

Description:
[0001]    This application is a National Stage completion of PCT/EP2010/063134 filed Sep. 7, 2010, which claims priority from British patent application serial no. 0915552.4 filed Sep. 7, 2009. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to cable-raceways of the kind for support and routing of electrical, fibre-optic and other cables. 
       BACKGROUND OF THE INVENTION 
       [0003]    Cable-raceways are conventionally provided in the form of metal channels within which the cables are retained for support and routing, for example within aircraft and other vehicle installations. The use of metal for the channels has the advantage of affording good physical support for the cables along their lengths and a degree of screening of them from external electromagnetic interference. The interference may be for example from lightning but may also be by induction from adjacent runs of electrical cable. Accordingly, although a raceway may be provided as a single channel it is conventional to route electrical cables between which there may be undesirable interference via different, parallel raceway-channels of a unitary, metal extrusion. Raceways constructed in this way provide good physical support but have the disadvantage that changes in direction and elevation of the cable-run can be accommodated only by fabricating specially-contoured channeling-sections adapted to the particular change required, and coupling them into the raceway between standard straight-sections. A further disadvantage arises in particular in aircraft installations where weight is a significant factor. 
       SUMMARY OF THE INVENTION 
       [0004]    It is an object of the present invention to provide a form of cable-raceway by which these disadvantages can be to a large extent overcome. 
         [0005]    According to the present invention there is provided a cable-raceway wherein a channel of the raceway is defined by an elongate tape that comprises an electrically-conductive mesh, the tape having longitudinal folds to define upstanding mutually-spaced side-walls of the channel. 
         [0006]    The mesh may be a woven mesh that comprises electrically-conductive strands, and may have the warp of the woven mesh extends longitudinally of the channel. The weave may be a narrow-fabric weave, and the weft of the weave may involve a single unbroken electrically-conductive strand. 
         [0007]    Also, the electrically-conductive strands may be individual wire-strands or a plurality of wire-strands twisted together, and the wire-strands which may be of nickel-coated copper, may be bare so that good electrical contact between all of them in common in the mesh. 
         [0008]    The mesh may be covered fully or partially on one face, or if desired on both faces, with electrically-insulating material. In particular, the electrically-insulating material may be in the form of a plastics sheet that is secured (for example, by stitching or bonding) to the mesh within the channel to provide an electrically-insulating barrier between the mesh and the cables within the channel. The plastics material may be, for example, of polytetrafluoroethylene. 
         [0009]    The cable-raceway according to the invention may comprise a plurality of parallel channels extending side by side with one another, the longitudinal folds of the tape defining in respect of each channel a bottom of the channel and mutually-spaced side-walls upstanding from the channel-bottom. Brackets, which may be of metal and located at intervals along the raceway, may provide for electrical ground-bonding of the raceway. Each bracket may have a base that extends transversely of the channels with the channel bottom of each individual channel secured to the base of that bracket and with arms upstanding from the base providing support for retention of the tape in its plural-channel configuration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0010]    Cable-raceways according to the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0011]      FIG. 1  is a side elevation of a part of the length of a four-channel cable-raceway according to the invention used for routing electrical and/or fibre-optic cables in an aircraft or other installation; 
           [0012]      FIG. 2  is a section of the cable-raceway taken on the line  2 - 2  of  FIG. 1 ; 
           [0013]      FIG. 3  is a representative cross-section of electromagnetically-shielding tape utilized in the fabrication of the raceway of  FIG. 1 ; 
           [0014]      FIG. 4  is illustrative of a plan view of the tape of  FIG. 3 ; 
           [0015]      FIG. 5  is illustrative schematically of the weave of a wire-mesh that forms part of the tape of  FIGS. 3 and 4 ; 
           [0016]      FIG. 6  is a representative cross-section of the raceway taken on the line  6 - 6  of  FIG. 1  to show part of a typical electrical ground-bonding support-assembly of the raceway; 
           [0017]      FIG. 7  is a perspective view from above of the four-channel cable-raceway of  FIG. 1  when sectioned on the line VI-VI of  FIG. 1  and showing the electrical ground-bonding support-assembly of  FIG. 6 ; 
           [0018]      FIG. 8  is an enlarged perspective view of a typical cable-retainer used in the electrical ground-bonding support-assembly of  FIGS. 6 and 7 ; 
           [0019]      FIG. 9  is a perspective view from above of the four-channel cable-raceway of  FIG. 1  when sectioned on the line  9 - 9  of  FIG. 1  to show a typical intermediate support-assembly of the raceway; 
           [0020]      FIG. 10  is an exploded view illustrating intercoupling of woven tapes together into a raceway according to the invention; and 
           [0021]      FIGS. 11 and 12  are illustrative of respective warp patterns that may be adopted for tape weaving in the construction of raceways according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Referring to  FIGS. 1 and 2 , the cable-raceway  1  of the example of the invention has four open-top channels  2  of rectangular section that are defined by a longitudinally-folded tape  3 . The tape  3  (the woven nature of which is illustrated only partially in  FIGS. 1 and 7  of the drawings) extends lengthwise of the raceway  1  and is folded longitudinally to form the bottom  4  and the two upstanding side-walls  5  of each channel  2  together with turned-over outer-rims  6  of the raceway  1 . The structure of the woven tape  3  is as illustrated in  FIGS. 3 and 4 . 
         [0023]    Referring to  FIGS. 3 and 4 , the tape  3  is of a lightweight construction that includes a woven mesh  7  of bare metal-wire strands (for example, in a twill weave). The mesh  7  is covered on one face throughout its length apart from within a marginal area  8  at each end, by an electrically-insulating sheet  9  of polytetrafluoroethylene that is bonded (it may alternatively be stitched) to the mesh  7 . 
         [0024]    As illustrated schematically in  FIG. 5 , the warp of the woven mesh  7  is formed by fine wire-strands  10  that run lengthwise of the tape  3 , whereas the weft is formed by a fine wire-strand  11  (emphasized in the drawing) that runs back and forth without break, in a narrow-fabric weave with the warp strands  10 . The strands  10  and  11  are, for example, single-wire-filaments or twisted pairs, of nickel-coated copper wire, and the strands  10  are fine enough that a group (in the case illustrated, of four) of them are drawn together through the dent space of the weaving loom; the gap G between the adjacent groups resulting from the dents (and shown exaggerated in  FIG. 5 ), is small enough that it does not materially affect the shielding against electromagnetic interference provided. Depending on the weave pattern used, the weft strand  11  may, for example, pass successively over one group of warp strands  10  and under the next in the weave. 
         [0025]    The tape  3  is folded on longitudinal fold-lines indicated by chain-dotted lines  12  in  FIG. 4 , to define the four interlinked channels  2  of rectangular cross-section illustrated by  FIG. 2  with the electrically-insulating sheet  9  on the inside of each channel  2 . The folded mesh  7  of woven wire retains the four-channel configuration into which it has been folded with a measure of both lateral and longitudinal rigidity. In this regard, however, support for retention of the tape  3  in its folded four-channel configuration laterally and for enhancing its load-carrying capacity longitudinally, as well as providing for ground-bonding of it electrically, is provided by metal brackets  13  (only one shown in  FIG. 1 ) located at intervals along the length of the raceway  1 . 
         [0026]    As illustrated by  FIGS. 6 and 7 , the bracket  13  at each support-location has an elongate rectangular base  14  that extends transversely across the underside of the raceway  1  in abutment with the bottom  4  of each channel  2  and with the channels  2  nesting tightly between limbs or arms  15  upstanding from the base  14 . This nesting holds the bare wire-mesh  7  of the tape  3  in both physical and electrical contact with the base  14  and the arms  15  of the bracket  13 , and this contact is enhanced by a plastics insert  16  that fits resiliently over the tape  3  within the bracket  13  to bear on the tape  3  throughout its transverse contour within the bracket  13 . A rivet  17  within each channel  2  clamps the insert  16  tightly to the base  14  of the bracket  13  with the bottom  4  of that channel  2  sandwiched between them. This and the resilient nature of the insert  16 , ensures that there is good physical and electrical contact between the mesh  7  and the bracket  13  throughout the full width of the tape  3 . Flanges  18  extending from opposite ends of the base  14  of each bracket  13  are used to mount the brackets  13  securely to individual electrical grounding points (not shown) of the installation. 
         [0027]    As illustrated most clearly in  FIG. 6 , the insert  16  is formed with series of ratchet teeth  19  which extend down both side-walls  5  within each channel  2  and are for engagement by respective cable-retainers  20  of the channels  2  (only two such retainers  20  are shown in  FIG. 6 ). The cable-retainers  20  are for use as illustrated in the case of only one channel  2  in  FIG. 7 , for firm retention of cables  21  in that channel. 
         [0028]    Each retainer  20 , which is of molded plastics, is of the substantially-rectangular form shown in  FIG. 8 , for fitting longitudinally within its respective channel  2  with its two ends  22  extending transversely of that channel and its two sides  23  engaged on opposite sides of the channel  2  respectively with the ratchet teeth  19  there. The sides  23  each have two spaced sets of ratchet teeth  24  and are attached to both ends  22  by flexure joints  25  to enable the retainer  20  to be pushed down into its channel  2  with its teeth  24  engaging the teeth  19 . Downward pressure on the retainer  20  causes the sides  23  to flex inwardly and allow the retainer  20  to be stepped downwardly by ratchet action onto the cables beneath. Release of the retainer  20  and withdrawal of it from the channel  2  is achieved using pliers to squeeze its two sides  23  towards one another and thereby release the teeth  24  from the teeth  19 . 
         [0029]    As well as using the brackets  13  at spaced intervals along the raceway  1  for retention of the tape  3  in its folded four-channel configuration and enhancing its load-carrying capacity longitudinally, retention in that configuration may be achieved to the same effect intermediate the ground-bonding brackets  13  as illustrated in  FIG. 9 . 
         [0030]    Referring to  FIG. 9 , the tape  3  in this case is sandwiched at the intermediate location between an external transversely-extending plastics strap  27 , and an insert  28  of the same form as the insert  16  used with the bracket  13 . The insert  28  is riveted to the strap  27  through the bottom  4  of each channel  2 , and retainers  29  of the same form as the retainers  20  of  FIG. 7 , are used for cable-retention. 
         [0031]    The use of the flexible woven-tape  3  to define the channels  2  of the raceway  1  has the advantage that changes in direction of the raceway can be achieved simply by bending and without the need to break the run to insert a specially-configured section. The bending of the raceway  1  to effect a change of elevation may be achieved by bending it to incline upwardly or downwardly in the plane of  FIG. 1  (for example to enable the raceway to cross-over another raceway or obstacle), and similarly, a change of direction in azimuth may be achieved by bending it into or out of the plane of  FIG. 1 . The woven mesh  7  of the tape  3  readily accommodates all such bending within the weave without any relevant distortion, and the use of support-assemblies of the form illustrated in  FIG. 7  can be used to maintain the bend and channel-configuration. Intermediate support-assemblies of the form illustrated in  FIG. 9  may also be used to maintain and restore desired channel-configuration elsewhere. 
         [0032]    Furthermore, as well as accommodating bends for changes of elevation and azimuth, the raceway of the invention may readily accommodate twisting along its length for changes of plane of the channels  2 . 
         [0033]    Accordingly, the flexibility of the woven structure allows a single tape  3  to be used for the full length of the cable-run required, without having to couple tapes together end to end. Where however, there is a need to couple tapes together end-to-end, this may be readily carried out as illustrated in exploded form by  FIG. 10 . 
         [0034]    Referring to  FIG. 10 , two woven tapes  30 , each folded correspondingly into four channels  31 , are coupled together end-to-end using a ground-bonding support-assembly  32  of the form illustrated in  FIG. 7 . In this, the bare end  33  of one tape  30  is inserted into the bare end  33  of the other tape  33  and the two sandwiched together one upon the other between an insert  34  corresponding to the insert  16  of  FIG. 7 , and a metal bracket  35  corresponding to the bracket  13  of  FIG. 7 . Rivets  36  secure the tapes  30  fast together and to the mounting bracket  35  giving good structural and electrical connection and ground-bonding between them. 
         [0035]    The cable-raceway  1  described above is effective to afford electromagnetic shielding for the cables contained in the individual channels  2 . Where the height of the channel is three times its width, a significant degree of shielding from external sources of interference has been found to be good for up to a 60% cable-filling of the channel. Furthermore, provided cables filling the channel do not protrude from its open top, interference between adjacent channels can be avoided. 
         [0036]    Although the tape  3  of the cable-raceway  1  described above is covered on one face by the electrically-insulating sheet  9 , this covering and the insulation it provides within the channels  2 , may be dispensed with. The mesh  7  may be bare or may be coated for example with nylon; a coating of this form can be used to add stiffness to the raceway and fill inter-strand gaps in the weave and reduce adhesion of debris. 
         [0037]    Furthermore, it will be understood that the invention is not limited to the provision of a specific number of channels in that the number may be more than four and may be fewer, and indeed may be merely one. 
         [0038]    Where strengthening of the woven tape used for the raceway is required, this may be achieved by the introduction of additional strands of metal, plastics or fibre into the weave (weft or warp). Moreover, the introduction of additional strands may be distributed across the width of the tape, but may also be in groupings at individual locations as illustrated in  FIGS. 11 and 12 . 
         [0039]    In  FIG. 11  additional warp strands  36  are shown bunched together within one area across the width of the weave, whereas in  FIG. 12 , additional warp strands  37  are shown bunched one upon the other at one location across the width. 
         [0040]    Where break out of cabling from the raceway is required, this may achieved simply by feeding the cabling out from between two closely-located support-assemblies that are of either of the forms illustrated in  FIGS. 7 and 9 . Similarly, where cabling is to be added into the raceway this may be achieved by feeding it into the raceway between two closely-located support-assemblies of either of those forms.