Abstract:
A device and method for securing a plurality of electrical conductors in a bundle. The device ( 10 ) comprises first and second portions ( 12   a,    12   b ) connected so as to be moveable between a closed configuration in which the first and second portions define at least one enclosed space which extends through the device and an open configuration in which a conductor may be moved laterally into the at least one space from the periphery of the device. The device further includes a plurality of recesses ( 20 ) for receiving conductors disposed around its peripheral edge.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention concerns a device for securing cables. More particularly, but not exclusively, this invention concerns a device for securing a plurality of electrical conductors in a bundle, and a method of securing together conductors in an aircraft. The invention also concerns a clamp for attaching a bundle of conductors held together by a cable retaining device to a surface. 
       BACKGROUND OF THE INVENTION 
       [0002]    In an aircraft, cables made up of bundles of electrical conductors are used to distribute power from an electrical generator to various items of equipment which require electrical power to operate. Such cables usually carry three phases, with each phase being associated with two individual conductors connected in parallel. Thus, the cable is a bundle of six individual electrical conductors. An exciter cable which supplies field energy and control signals to the electrical generator is also often routed together with the power cable. The power cable plus exciter cable bundle is typically secured along its route inside the supporting structure of the cabin floor, the tail section of the aircraft, and also the wings. 
         [0003]    The electrical conductors in the power cable are sensitive to electromagnetic radiation, and also themselves emit such electromagnetic radiation. The exciter cable also emits electromagnetic radiation. To prevent interference effects resulting from this electromagnetic radiation, the arrangement of the conductors and the exciter cable in the bundle must be controlled so as to maintain appropriate spacing between the various elements in the bundle, depending on the sensitivity of the individual conductors to the interfering radiation. 
         [0004]    U.S. Pat. No. 5,243,138 discloses a device for securing a plurality of electrical conductors in an aircraft. A known device, broadly corresponding to that shown in U.S. Pat. No. 5,243,138, is illustrated by  FIGS. 1   a  and  1   b,  and comprises two plastic sections  1   a  and  1   b  which snap together. Each section has at the centre (of the assembled device) a curved arm, the two curved arms  2   a,    2   b  defining a space  3  in which a conductor can be gripped when the device is assembled. The sections  1   a,    1   b  also each have three further curved arms  4  on their peripheral edges, which cooperate with recesses  5  in the outer periphery of the device to define six further conductor retaining spaces. All of the peripheral conductor spaces are open-sided so that a conductor can be pushed laterally into the space. The peripheral arms each include a pair of tabs  6  extending radially outwards so as to define a circumferential channel around the device. In use, once the conductors have been inserted into the spaces, a band  7  (such as a jubilee clip, or, as in  FIG. 1 , a P-clip) is secured around the device in the channel to hold the device and conductors together. This band can then be fastened to a suitable part of the aircraft structure. 
         [0005]    The device of U.S. &#39;138 has several disadvantages and/or could be improved in various respects. It only has seven conductor spaces, so it is not well-suited for use with cables which have a neutral conductor in addition to the six phase conductors and the exciter cable. It is known to solve this problem by using the central space to hold the neutral conductor and to provide a separate auxiliary retainer  8  (see  FIGS. 1   a  and  1   b ) which has a recess for the exciter cable and which is shaped so that it can rest on the circumferential edge of the device and be held in place by the band. Installing a cable using such an auxiliary retainer is particularly difficult, however, since the fitter must maintain the main device and auxiliary retainer in the correct position relative to each other whilst fitting a band around both. It has been found that using this system often results in damage to the device and/or the auxiliary retainer during installation. 
         [0006]    Installation of the U.S. &#39;138 device can also be challenging for the fitter because the device has two separate parts. This means that the fitter must hold one half of the device in the correct position, push the conductors into place on that half of the device, and maintain them there whilst the other half of the device is connected and the rest of the conductors are pushed into place. It is easy during this process for the fitter to drop the second half of the device, or to be too forceful in pushing the conductors into place, either of which can damage the device. This risk is exacerbated by the fact that the conductors are usually very stiff, whereas certain parts of the device, such as the peripheral arms, are relatively thin and fragile. 
         [0007]    It is often desirable to hang the cable from the aircraft structure using P-clips, rather than jubilee clips. The band of a P-clip defines a teardrop shape rather than a circle, meaning that if a P-clip is used to secure the device shown in  FIGS. 1   a  and  1   b  there will be gaps  9  between the device and the clip at the point of the teardrop as shown in  FIG. 1   a.  It has been found that conductors can escape from the peripheral spaces into these gaps, leading to electromagnetic interference between the phases. Furthermore, the gaps  9  mean that the P-clip band does not fully engage with the circumferential channel on the device so in use the P-clip can become laterally dislodged from the device. 
         [0008]    In other locations in an aircraft it may not be possible to use P-clips to attach a cable bundle to the aircraft structure because of space constraints. In some situations it is possible to use a saddle clamp in conjunction with a jubilee clip as is shown in  FIG. 1   b . Known saddle clamps comprise a curved portion  3   a  arranged to engage with the curved edge of a prior art cable retaining device, from which extends radially a flat portion  3   b.  The flat portion has holes  11  through it to enable it to be screwed or bolted to the aircraft structure. The cable retaining device is held to the saddle clamp by a jubilee clip  13 , which may be the same clip as is used to hold the cable retaining device together. As is clear from  FIG. 1   b , prior art saddle clamps are configured for attachment to surfaces which are perpendicular to the longitudinal axis of the cable bundle, and this limits the situations in which they can readily be used. It also means that they are quite bulky, and that the cable bundle cannot be held closely against a surface which it runs parallel to by such saddle clamps. 
         [0009]    The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved cable retainer for securing bundles of conductors. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention provides, according to a first aspect, a device for securing a plurality of electrical conductors in a bundle. The device comprises first and second portions. The first and second portions are configurable between a closed configuration and an open configuration. The first and second portions are preferably arranged to be connected (or are already so connected/arranged) so as to be moveable between the closed configuration and the open configuration. The closed configuration is preferably one in which the first and second portions define at least one enclosed space (for example a central bore) which extends through the device. The open configuration is preferably one in which a conductor may be moved laterally into the at least one space (for example the central bore) from the periphery of the device. The device also has a plurality of recesses, for example outer recesses, for receiving conductors disposed around its peripheral edge. The first and second portions may be arranged so as to prevent movement of a conductor accommodated in the at least one space (for example, a central bore and/or an outer recess) defined when the device is in the closed configuration, laterally out therefrom. 
         [0011]    Advantageously, the connection between the first and second portions enables devices according to the invention to be opened to allow access to the conductor space or spaces whilst remaining as a single object. This in turn enables a fitter to hold the device easily with one hand, leaving his/her other hand free to guide the conductors into the spaces and/or recesses. Preferably the device is arranged such that an operator can move it between the open and closed configurations using one hand. The device may be a device for securing a plurality of aircraft electrical conductors in a bundle. 
         [0012]    A first part of the surface defining the central bore may be formed by the first portion of the device and a second part of the surface defining the central bore may be formed by the second portion of the device. The device may of course comprise a third and/or other portions. The device may alternatively be essentially in the form of a two part device (excluding any clamps, bands, fixings or the like for example). 
         [0013]    The device may be substantially planar in its general form. For example, the device may be so shaped that, when in the closed configuration, it has a cross-sectional footprint having a minimum dimension in the plane of the device that is significantly greater than the thickness of the device (the dimension of the device transverse to the plane of the device). There may be one or more notional planes of the device. 
         [0014]    The device may be arranged such that conductors secured by the device run transversely to the plane of the device. The at least one enclosed space may extend transversely through the plane (or the thickness) of the device. The device may have a transverse thickness which is less than half of its maximum dimension in the plane of the closed device. Preferably the device has a transverse thickness which is less than a quarter of its maximum dimension in the plane of the closed device. The maximum transverse dimension of the device may be between 5 mm and 40 mm. Preferably the maximum transverse dimension of the device is between 10 mm and 25 mm. The maximum dimension in the plane of the closed device may be between 40 mm and 100 mm. Preferably the maximum dimension in the plane of the closed device is between 50 mm and 80 mm. The weight of the device may be less than 25 g. Preferably the weight of the device is less than 15 g. 
         [0015]    One or more of the plurality of recesses may comprise an arcuate surface. One or more of the plurality of recesses may be part-circular. Each of the plurality of recesses may comprise an arcuate surface and/or be part circular. Each of the arcuate surfaces may be substantially the same shape and size. Each of the plurality of recesses may be substantially the same distance from the centre of the enclosed space when the device is closed. The separations between a plurality of adjacent pairs of recesses may be substantially the same when the device is closed. The recesses may be spaced at equal angles around the peripheral edge of the device. Each of the plurality of recesses may be arranged to accommodate a conductor having a diameter of between 3 mm and 15 mm. Each of the plurality of recesses may be arranged to accommodate a conductor having a diameter of between 5 mm and 12 mm. 
         [0016]    The at least one space may be arranged to accommodate a conductor having a diameter of between 3 mm and 15 mm when the device is closed. The at least one space may be arranged to accommodate a conductor having a diameter of between 5 mm and 13 mm when the device is closed. The area of the at least one space may be larger than the cross-sectional area of the largest conductor (with circular cross-section) which it is arranged to accommodate. For example, one or more retaining arms arranged to retain a conductor of a given cross-sectional area smaller than the area of the at least one space may extend into the at least one space. The at least one space (for example, all spaces for receiving conductors including a central bore and all peripheral recesses) may comprise a significant fraction of the overall footprint of the device. Advantageously, devices according to the invention in which the space comprises a significant fraction of the device are relatively lighter than devices in which the space is smaller, which is an important consideration for devices which are intended for use in aircraft. 
         [0017]    The plurality of peripheral (outer) recesses may comprise six recesses arranged to accommodate six conductors circumferentially spaced, for example in hexagonal formation, about a central bore, when the device is in the closed configuration. 
         [0018]    One or more of the plurality of peripheral recesses may be associated with a retaining arm extending across at least part of the recess so as to retain a conductor in the recess. Each of the plurality of peripheral recesses may be associated with such a retaining arm. The one or more retaining arms may be formed integrally with one of the first and/or second portions. The one or more retaining arms may be resilient. The one or more retaining arms may be arranged so as to be able to flex. The one or more retaining arms may form part of a peripheral edge of the device. The peripheral edge so formed may be curved. The one or more retaining arms may comprise one or more projections extending outwardly from the peripheral edge of the device. The one or more retaining arms may comprise a pair of such projections. The one or more retaining arms may comprise a plurality of such projections that together with an outer surface of the one or more arms define a channel. The channel may be arranged to receive the band of a clip, for example a P-clip or a jubilee clip. The projections may be arranged to minimise or prevent lateral movement of a clip being used on the device. 
         [0019]    At least one of the first and second portions may be formed as a single piece. Preferably each of the first and second portions is formed as a single piece. The first and second portions may be pivotally connected. If the first and second portions are pivotally connected, they may be arranged to pivot about an axis transverse to the plane of the device. The first and second portions may be connected by a hinge. The hinge feature may enable devices according to the invention to be opened and closed in a clam shell manner, i.e. with the first and/or second portions pivoting about an axis transverse to the plane of the device. Alternatively, the first and second portions may be arranged to pivot about an axis in the plane of the device. The first and second portions may be connected such that they can be moved between a closed configuration in which the first and second portions form an “O” shape and an open orientation in which they form an “S” shape, for example by means of the aforementioned pivoting movement. The first and second portions may be slidably connected. The first and second portions may be arranged to slide relative to each other in a direction in the plane of the device. The first and second portions may be pivotally connected by means of a snap-fit connection. Thus, the first and second portions may be configured to be pivotally connected together, subsequently to be detached completely from each other, but then reattached. All of the spaces of the device for receiving conductors (for example including a central bore and all outer recesses) may be exclusively defined by the first portion, by the second portion or by parts of first and second portions. 
         [0020]    The device may comprise a fastener for maintaining the device in the closed configuration. Devices having this feature advantageously are able to remain in the closed configuration without the operator needing to hold the device in that configuration. This allows the operator to use both hands to perform other tasks, such as adjusting the positioning of the conductors in the device, or fitting a clip around the outside of the device. The fastener may comprise a first formation on the first portion arranged to engage, for example by means of an interference fit, with a second corresponding formation on the second portion. One of the first and second formations may comprise a recess. The other of the first and second formations may comprise a projection, for example corresponding to such a recess. 
         [0021]    The device may be arranged such that the first and second portions, when in the closed configuration, define at least one further enclosed space extending through the device for receiving a conductor, the at least one further space being disposed such that a conductor may be moved laterally into the at least one further space from the periphery of the device when the device is in the open configuration. In devices according to the invention, the spaces extending through the device are fully enclosed when such devices are in the closed configuration. Therefore, providing further such spaces advantageously means that a greater number of conductors can be located in the device such that there is no risk of them becoming dislodged and creating interference. The device may have two such further spaces. One or more of such further enclosed spaces may be disposed at or near the periphery of the device. 
         [0022]    The at least one space may be disposed approximately centrally in the device. The at least one further space may be disposed toward the periphery of the device. The at least one space may be disposed relative to the recesses and/or the at least one further space so as to reduce the risk of interference between conductors received in the spaces and/or recesses when the device is in use. The at least one space may be larger than the at least one further space. 
         [0023]    The peripheral edge of the device may include an angular region having two (preferably flat) surfaces which define a corner therebetween. In the case where the device has a first portion and a second portion, one of the two (preferably flat) surfaces may be defined by the first portion of the device and the other of the two surfaces may be defined by the second portion of the device. The two surfaces may meet at an angle in the range 70° to 110°. Preferably the two surfaces meet at an angle in the range 80° to 100°. The peripheral edge of the device may include one or more surfaces which are arranged such that the peripheral edge of the device includes a curved region. The curved region may be formed partly by the first portion of the device and partly by the second portion. The curved region may be part-circular. The curved region may be approximately semi-circular. Advantageously, devices according to the invention which have such an angular region and such a curved region can be fitted into the loop of a P-clip with a good fit between the corresponding surfaces (for example, with no or only very small gaps between the peripheral edge of the device and the clip). This in turn significantly reduces the risk of conductors escaping from the recesses and becoming damaged or causing interference. The device may be roughly teardrop-shaped so as to facilitate use of a P-clip around its peripheral edge. 
         [0024]    The device may include a slot arranged to bypass the angular region so as to define, in conjunction with the peripheral edge of the device excluding the angular region, a roughly circular path around the device. Advantageously, devices having this feature can be used with circular clips as well as with P-clips. The slot may be suitable for receiving the band of a jubilee clip. 
         [0025]    The device may include at least one arm which extends into the at least one space to inhibit lateral movement of a conductor received within the space. The at least one arm may be curved, to facilitate engagement with a conductor. The device may include two such arms arranged such that in use of the device a conductor received within the space is held between the two arms. The at least one arm may be arranged so as to be able to flex. Advantageously, this feature allows devices according to the invention to receive conductors of a range of cross-sectional shapes and sizes within the at least one space. The at least one arm may be resilient. The device may include a formation arranged to limit the amount which the arm is able to flex. Advantageously, this feature of devices according to the invention prevents the arms flexing too much and becoming damaged or broken. The formation may be in the form of a stop. The at least one arm may be formed integrally with one of the first and/or second sections. 
         [0026]    The present invention also provides, according to a second aspect, a method of securing together a bundle of conductors in an aircraft. Such a method may comprise the use of a device as described in relation to the first aspect. In such a case, the method may also comprise the steps of 
         [0027]    providing a plurality of conductors extending between a first part of an aircraft and a second part of that aircraft, 
         [0028]    arranging the device in the open configuration by moving the first portion relative to the second portion whilst the first and second portions remain connected together, 
         [0029]    positioning a first one of the plurality of conductors between the first and second portions such that the conductor will be enclosed by the at least one space (for example the central bore) when the device is closed, and 
         [0030]    moving the device into the closed configuration. 
         [0031]    The step of arranging the device in the open position may be carried out by pivoting the first and second portions relative to each other. The step of moving the device into the closed configuration may be carried out by pivoting the first and second portions relative to each other. The method may further comprise the step of pushing a further one of the plurality of conductors into one of the plurality of recesses. This step may be repeated until all of the plurality of conductors are received within either the at least one space or the plurality of recesses, with one conductor per space/recess. The method may additionally comprise the steps of providing a band and fastening the band around the peripheral edge of the device. This step may be carried out once all of the conductors are received within either the at least one space or the plurality of recesses. The band may comprise a P-clip. Alternatively, the band may comprise a jubilee clip. 
         [0032]    The method may include the step of providing one or more further devices as described above. The one or more further devices may be used to secure together the bundle of conductors at a different point or points along the length of the conductors to where the first device is used. The method may include the step of attaching the device to a surface in an aircraft, for example via a band as mentioned above. 
         [0033]    The present invention also provides, according to a third aspect, a device for securing a plurality of electrical conductors in a bundle, wherein the device has first and second portions and at least two spaces for conductors each being formed by both the first and second portions. Such a device may comprise first and second portions which are movable relative to each other into a closed configuration in which the first and second portions define a central bore which is preferably wholly enclosed in the plane of the device by the device and which extends through a central region of the device for receiving a conductor. The first and second portions may also be movable relative to each other into a closed configuration in which the first and second portions define a peripheral bore which is preferably wholly enclosed in the plane of the device by the device and which extends through a peripheral region of the device for receiving a conductor. The first and second portions may be arranged such that a first part of the surface defining the central bore is formed by the first portion and a second part of the surface defining the central bore is formed by the second portion. The first and second portions may be arranged such that a first part of the surface defining the peripheral bore is formed by the first portion and a second part of the surface defining the peripheral bore is formed by the second portion. The device may further have a plurality of recesses for receiving conductors disposed around its peripheral edge. 
         [0034]    Advantageously, conductors are substantially prevented from escaping from the enclosed bores of devices according to the fourth aspect of the invention when such devices are in the closed configuration, even if significant forces (of the magnitude that might be sustained during use) are exerted on the conductors and/or the devices. 
         [0035]    The first and second portions may be arranged to move to an open configuration, in which a conductor may be moved laterally into either of the central and peripheral bores. This feature of devices according the fourth aspect of the invention allows conductors to easily be inserted into the bores since it is not necessary to poke them through the bores lengthways. 
         [0036]    The device may be arranged such that the first and second portions, when in the closed configuration, define at least one further peripheral bore which is wholly enclosed by the device and which extends through a peripheral region of the device for receiving a conductor, wherein a first part of the surface defining the further peripheral bore is formed by the first portion and a second part of the surface defining the further peripheral bore is formed by the second portion. The further peripheral bore may be smaller than the first peripheral bore. The further peripheral bore may be arranged to receive an exciter cable. The first peripheral bore may be arranged to receive a phase conductor. The peripheral bore and/or the further peripheral bore may be arranged to accommodate a conductor with a non-circular cross section. The central bore may be larger than the peripheral bore or bores. 
         [0037]    One of the first and second parts of the surface defining the peripheral bore may be flat. The other of the first and second parts of the surface defining the peripheral bore may be in the form of a recess. The recess may be curved. One of the first and second parts of the surface defining the further peripheral bore may be flat. The other of the first and second parts of the surface defining the further peripheral bore may be in the form of a recess. 
         [0038]    The invention also provides, according to a fourth aspect, a method of securing together a bundle of conductors in an aircraft comprising the steps of 
         [0039]    providing a plurality of conductors which extend between a first part of an aircraft and a second part of that aircraft, 
         [0040]    providing a device as described above in relation to the third aspect of the invention, 
         [0041]    inserting a first one of the plurality of conductors into the central bore such that the first conductor is circumferentially enclosed by the device, and 
         [0042]    inserting a second one of the plurality of conductors into the peripheral bore such that the second conductor is circumferentially enclosed by the device. 
         [0043]    The step of inserting a first one of the plurality of conductors may comprise the steps of 
         [0044]    arranging the device in an open configuration in which the first and second portions are relatively spaced apart from each other as compared with the closed configuration, 
         [0045]    and moving the first one of the plurality of conductors laterally into the central bore. 
         [0046]    The first conductor may be a neutral conductor. Alternatively, the first conductor may be a phase conductor. The first conductor may be an exciter cable. The second conductor may be a phase conductor. The second conductor may be an exciter cable. 
         [0047]    The step of inserting a second one of the plurality of conductors may comprise the steps of 
         [0048]    arranging the device in an open configuration in which the first and second portions are relatively spaced apart from each other as compared with the closed configuration, 
         [0049]    and moving the second one of the plurality of conductors laterally into the peripheral bore. 
         [0050]    The method may include the step of moving the device into the closed configuration. The method may include the step of inserting a third one of the plurality of conductors into a further peripheral bore such that the third conductor is circumferentially enclosed by the device. The method may further comprise the step of pushing a further one of the plurality of conductors into one of the plurality of recesses. This step may be repeated until each of the plurality of conductors are received within either the central bore, the peripheral bore, the further peripheral bore (if present) or a recess. 
         [0051]    The invention also provides, according to a fifth aspect, a device for securing a plurality of electrical conductors in a bundle, the device comprising a body portion having a plurality of spaces for receiving elongate conductors, wherein the peripheral edge of the body portion includes two surfaces which define a corner therebetween such that the device is shaped to engage with a P-clip. The two surfaces may define an extended region of the body portion which is radially further from the centre of the body portion than all other regions of the body portion. The extended region may comprise at least one bore in which a conductor may be received. 
         [0052]    The invention also provides, according to a sixth aspect, a device as described above in relation to the fifth aspect in use with a P-clip, wherein the device and the conductors secured by the device fill substantially all of the space within the loop of the P-clip, such that any peripheral spaces between the P-clip loop and the peripheral edge of the device are smaller than the peripheral recesses. In some embodiments the device itself may define free space, but in such contexts it will be understood that the device still fills substantially all of the space within the P-clip loop. The P-clip loop may be in contact with substantially all of the two surfaces. The P-clip may be fastened to a surface in an aircraft. 
         [0053]    The invention also provides, according to a seventh aspect, a device for securing a plurality of electrical conductors in a bundle, the device comprising a body portion having at least one space through the body portion for receiving an elongate conductor, and at least one arm which extends into the space to inhibit radial movement of a conductor received within the space, the at least one arm being arranged so as to be able to flex relative to the body portion, and wherein the device includes a formation arranged to limit the amount of this flexion. 
         [0054]    The formation may comprise a projection extending inwardly from the inner surface of the at least one space. Alternatively, the formation may comprise a projection extending outwardly from the outer surface of the at least one arm. The formation may comprise a ridge. The formation may comprise a stop. The formation may comprise a boss. The formation may be formed integrally with the at least one arm. The formation may be formed integrally with the body portion. 
         [0055]    The present invention also provides, according to an eighth aspect, an aircraft comprising a bundle of electrical conductors secured by at least one device as described in relation to any of the first, third, fifth, sixth and seventh aspects. 
         [0056]    The invention also provides, according to a ninth aspect, a clamp for attaching a bundle of conductors held together by a cable retaining device to a surface. The clamp may be provided as part of a kit of parts. Such a kit may also include a device of the present invention, as described or claimed herein, for securing a plurality of electrical conductors in a bundle. The clamp preferably comprises a first portion adapted to engage with (preferably removably engage with) a cable retaining device. The first portion may have a generally arcuate surface adapted to engage with such a device. The first portion is connected to (including being integrally formed therewith) a second portion which is adapted to be attached to a (preferably flat) surface, for example of an aircraft structure. The second portion may have a generally planar surface for this purpose. The clamp is advantageously arranged such that in use the longitudinal axis of a bundle of conductors held by the cable retaining device is parallel to the surface to which the clamp is attached. The surface may be a surface in an aircraft. Advantageously, the feature of the clamps according to the invention of being arranged to attach to a surface parallel to the longitudinal axis of the bundle of conductors being clamped allows for the clamps to be significantly smaller than prior art clamps. Also the bundle can advantageously be held very close to the surface to which it is being attached, allowing bundles to be routed through smaller spaces than would otherwise be possible. 
         [0057]    The clamp may be a saddle clamp. The first portion may be arranged to engage with a substantially planar cable retaining device. The first portion may be arranged to engage with a cable retaining device having a peripheral edge which comprises a curved surface. The first portion may be arranged to engage with a cable retaining device as described herein in relation to any of the first, third, fifth, sixth and seventh aspects of the invention. The first portion may comprise at least one curved surface. The first portion may comprise an inner curved surface and an outer curved surface radially spaced from the inner curved surface. The first portion may be substantially arcuate. The clamp may be arranged such that in use a curved surface on the first portion abuts a curved surface on the cable retaining device. The clamp may be so arranged that, in use, the central longitudinal axis is centrally spaced apart from the extreme lateral edges defined by the arcuate surface of the first portion, preferably such that the angle subtended, within the plane of the device, by the extreme lateral edges defined by the arcuate surface and having a vertex at the central longitudinal axis is at least 30 degrees, and preferably more than 45 degrees and possibly more than 60 degrees. Thus, the extent of the clamp along the surface may be relatively great thus providing a reliable and strong means for clamping the bundle of conductors relative to the surface. 
         [0058]    The first portion may comprise at least one recess arranged to receive a projection disposed on the peripheral edge of a cable retaining device. This engagement between the recess and the projection helps to ensure that movement between a clamp according to the invention and a device it is clamped thereto is minimised. The at least one recess may extend radially from the at least one curved surface. The first portion may comprise two recesses arranged to receive a projection disposed on the peripheral edge of a cable retaining device. Preferably the first portion includes four such recesses. The at least one recess may be larger than the projection it is arranged to receive. This feature of clamps according to the invention makes it easy to fit a retaining device to a clamp. 
         [0059]    The second portion may comprise a flat surface. The clamp may be arranged such that in use the flat surface on the second portion abuts the surface to which the clamp is attached. The flat surface on the second portion may form an opposite face of the clamp to the curved surface on the first portion. The second portion may be substantially planar. The second portion may extend tangentially to the at least one curved surface on the first portion. 
         [0060]    There may be one or more holes extending through the second portion. The one or more holes may be arranged to receive the shaft of a bolt. There may be one or more holes extending through the first portion. The holes extending through the first portion may be larger than the holes extending through the second portion. The holes extending through the first portion may be aligned with the holes extending through the second portion. The holes extending through the first portion may be arranged to allow access to the holes extending through the second portion, for example to permit a screwdriver to be applied to the head of a screw received by one of the holes passing through the second portion. 
         [0061]    The clamp may include a passage between the first and second portions for receiving the band of a jubilee clip. The passage may be at least partly defined by a curved surface of the first portion. This feature of clamps according to the invention allows the clamp to be held to a cable retaining device by a jubilee or other similar clip, which may be the same clip which holds the retaining device together. 
         [0062]    The invention also provides, according to a tenth aspect, a surface in an aircraft having a bundle of conductors attached to it using a clamp as described in relation to the ninth aspect. 
         [0063]    The invention also provides, according to an eleventh aspect, a method of attaching a bundle of conductors held together by a cable retaining device to a surface in an aircraft comprising the steps of 
         [0064]    providing a bundle of conductors extending between a first part of an aircraft and a second part of that aircraft which is held together by a cable retaining device, 
         [0065]    providing a clamp arranged to engage with the cable retaining device, 
         [0066]    securing the clamp to a surface in the aircraft, and 
         [0067]    securing the clamp to the device such that the longitudinal axis of the bundle of conductors is parallel to the surface. 
         [0068]    It will of course be appreciated that the various aspects of the invention as described herein are closely related and that therefore essential or preferred features of one aspect of the invention may be incorporated into other aspects of the invention as described herein. For example, a clamp according to the ninth aspect of the invention may be used to attach a device according to any of the first, third, fifth, sixth and seventh aspects to an aircraft according to the eighth aspect. A device according to any aspect of the invention may be so configured as to be suitable for used in a method according to the same, or any other, aspect of the invention. Also, any aspect of a method of the invention may use, or be performed on, a device according to the same, or any other, aspect of the invention. Features of the device of the invention may be incorporated into the method of the invention and vice versa. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0069]    Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: 
           [0070]      FIG. 1   a  shows a side view of a prior art cable retaining device in use; 
           [0071]      FIG. 1   b  shows a side view of a prior art cable retaining device and a prior art saddle clamp in use; 
           [0072]      FIG. 2  shows a perspective view of a cable retaining device according to an example embodiment of the invention; 
           [0073]      FIG. 3  shows a side view of the device of  FIG. 2 ; 
           [0074]      FIG. 4  shows a side view of the device of  FIG. 2  in use with a P-clip; 
           [0075]      FIG. 5   a  shows a perspective view of a saddle clamp according to an example embodiment of the invention; 
           [0076]      FIG. 5   b  shows a side view of the clamp of  FIG. 5   a;    
           [0077]      FIG. 5   c  shows an end view of the clamp of  FIG. 5   a ; and 
           [0078]      FIG. 6  shows a side view of the device of  FIG. 2  and the clamp of  FIG. 5   a.    
       
    
    
     DETAILED DESCRIPTION 
       [0079]      FIGS. 2 and 3  show a cable retaining device  10  according to an example embodiment of the invention. The device  10  comprises two sections  12   a  and  12   b  moulded from a plastics material such as polyetherimide. If resistance to very high temperatures is required then the plastics material can be reinforced with glass fibres. The overall thickness of the device is 20 mm. When in the closed configuration shown in  FIGS. 2 and 3  the device has a maximum dimension in the plane of 60 mm. 
         [0080]    Sections  12   a  and  12   b  are connected by a hinge  14 . Hinge  14  consists of two pins formed integrally with section  12   a , which locate with either end of a cylindrical bore in section  12   b,  such that the sections may pivot relative to each other about the pins between an open configuration (not shown) and the closed configuration shown in  FIGS. 2 and 3 . Section  12   b  includes a projection  16  at the opposite end of the device to hinge  14 , which snap-fits into a corresponding recess  18  on section  12   a  to hold the device in the closed configuration. 
         [0081]    Section  12   a  has three recesses  20  arranged around the peripheral edge that forms the outer surface of the device  10 . Each recess is arranged to hold a circular cross-section conductor having a diameter of up to 9.9 mm (the diameter of a typical phase conductor). Each recess  20  has an associated retaining arm  22  extending across the open side of the recess. A recess  20  and its retaining arm  22  together form a substantially enclosed space with only a small gap being present between the inner surface of the retaining arm  22  and the lip of the recess  20 . Section  12   b  has two such recesses  20  and associated arms  22 . 
         [0082]    The retaining arms  22  are formed integrally with the sections  12   a,    12   b  and are slender enough at the points where they meet the recesses  20  to be able to flex by a significant amount. This flexibility allows the arms  22  to be deflected away from the device  10  such that conductors can be inserted radially into the recesses  20 . The arms  22  are resilient and spring back to their original position once the conductors have been inserted, and so act to retain the conductors in the recesses  20 . Each arm  22  has two tabs  23  projecting radially from its outer surface. The tabs  23  are formed integrally with the arms  22  and serve to prevent lateral movement of a band wrapped around the peripheral edge of the device  10  (for example the band of a P-clip or a jubilee clip). 
         [0083]    Each section  12   a,    12   b  has an extended portion  24   a,    24   b  at an end opposite the ends which are connected by hinge  14 . Each of the extended portions  24   a,    24   b  has a flat outer surface  26 . These flat surfaces meet at right angles when the device  10  is closed. A rectangular cross-section slot  28  passes through each of the extended portions  24   a,    24   b  close to where they join the rest of sections  12   a,    12   b.  The slot  28  allows a circular band (such as that belonging to a jubilee clip) to be wrapped around the device  10  when it is closed. The band passes through the slot  28  and so does not go around the extended portions  24   a,    24   b.    
         [0084]    Extended portion  24   a  includes a U-shaped space  30  extending from one face of the device  10  to the other. This space  30  is open-sided when the device is open, allowing a conductor to be inserted into it. When the device  10  is closed the space  30  is closed off by the edge of section  12   b,  retaining the conductor within it. Space  30  is large enough to hold a circular cross-section conductor of the same diameter as the conductors received by the recesses  20 . Space  30  is located toward the inner end of extended portion  24   a,  so that slot  28  passes to the outside of it. 
         [0085]    Extended portion  24   b  includes an approximately U-shaped space  32  extending from one face to the other. This space  32  is open-sided when the device is open and is closed off by the edge of section  12   a  when the device is closed. Space  32  is smaller than space  30 , and is arranged to hold an exciter cable. Space  32  is located towards the outer end of extended portion  24   b,  so that it is outside of slot  28 . 
         [0086]    Towards the centre of each section  12   a,    12   b  there is a semi-circular cut-away portion  34   a,    34   b.  A curved arm  36   a ,  36   b  extends into each of the cut-away portions. When the device  10  is closed the two curved arms  36   a,    36   b  define between them a cylindrical space 11.5 m in diameter, which is equal to the diameter of a typical neutral conductor. Smaller diameter cables may also be held by this central space, although clearly they will not be gripped as firmly by the arms  36   a,    36   b.  When the device  10  is opened the arms  36   a,    36   b  move apart so that a conductor can be inserted radially between the arms. 
         [0087]    The arms  36   a,    36   b  are formed integrally with the sections  12   a,    12   b.  The arms are slender enough to be able to flex slightly in the plane of the device, however excessive deflection of either arm toward the wall of its associated cut-away section could break that arm. To prevent such excessive deflection, a thin ridge  38  extends from the inner surface of each cut-away portion  34   a,    34   b.  Each ridge stops a short distance away from the outer surface of the associated arm  36   a,    36   b  so as to limit the degree of deflection possible by that arm whilst not adding significantly to the weight of the device  10 . 
         [0088]    In use, the device  10  holds up to seven conductors plus an exciter cable together in a bundle. To apply the device to a group of conductors consisting of six phase conductors and a neutral conductor, a fitter holds the device in the open configuration with one hand and pushes the neutral conductor between the two sections  12   a,    12   b  and into the central space between the arms  36   a,    36   b.  The device may then be closed enough that the neutral cable is held in place whilst still allowing access to spaces  30  and  32 . A phase conductor is pushed into space  30 , and the exciter cable is pushed into space  32 . The device  10  is then closed by squeezing the sections  12   a  and  12   b  together so that the projection  16  snaps into recess  18  to hold the device in the closed configuration. 
         [0089]    The device  10  will now support itself on the conductors which are already held within it, so the fitter may use both hands to ease the remaining phase conductors into the five recesses  20 . Once the recesses  20  have been filled, the arms  22  hold the phase conductors in place well enough to allow the fitter to use both hands to position the band of a retaining clip around the peripheral edge of the device, between the tabs  23  and then tighten it to hold all of the outer phase conductors securely in place. 
         [0090]      FIG. 4  shows a device  10  holding a neutral conductor  40 , six phase conductors  42   a - f,  and an exciter cable  44 . A P-clip  46  has been applied around the peripheral edge of the device. It can be seen that the extended portions  24   a,    24   b  fill the pointed region of the P-clip loop, and the flat surfaces  26  ensure that there are no gaps between the P-clip band and the peripheral edge of the device into which the phase conductor  42   f  could escape. 
         [0091]    Once a P-clip has been secured around the device  10 , the P-clip is used to hang the bundle from a part of the aircraft structure by passing a bolt through the ends of the P-clip band. Further devices  10  can then be applied at other points along the bundle as appropriate. 
         [0092]    In some locations within an aircraft it is not possible to hang the bundle from the structure using P-clips, for example because of space constraints. In these locations a jubilee clip is used to hold the device and conductors securely together, and a saddle clamp is used to attach the device to the aircraft structure. 
         [0093]      FIGS. 5   a - c  show a saddle clamp  50  according to the first example embodiment of the invention. The clamp  50  is moulded from a plastics material such as polyetheretherketone (PEEK) reinforced with glass fibres. It has a flat base portion  52  with a circular hole  54  at either end (only one hole is visible in  FIG. 5   a ) through which a bolt or screw can be inserted to fix the clamp to a surface. Above the base portion  52  and formed integrally with it there is an arcuate saddle portion  56 . The flat base portion  52  extends tangentially from the arcuate saddle portion  56 . 
         [0094]    The lower surface of the saddle portion  56  has downwardly extending ridges which define a passage  58  between the lower surface of the saddle portion  56  and the upper surface of the base portion  52 , as can be seen from  FIG. 5   c . The passage  58  allows a band, such as that of a jubilee clip, to pass through the clamp  50  so that it can be secured to a cable retaining device  10 . The saddle portion  56  also has two holes  60  passing through it. The holes  60  allow a screwdriver or similar tool to manipulate the screws or bolts in holes  54  before the clamp is attached to a device  10 . 
         [0095]    The upper surface of the saddle portion  56  has two recessed portions  62  on each of its long edges. These recessed portions receive the tabs  23  of a device  10 . Thus, the width of the saddle portion  56  between the recessed portions  62  is approximately equal to the distance between a pair of tabs  23  on device  10 . 
         [0096]    A saddle clamp  50  is used to secure a cable retaining device  10  to the structure of an aircraft where space is limited and the cable bundle must be held close to the structure. As can be seen from  FIG. 6 , the low profile of the saddle clamp  50  means that the cable bundle is held just a few millimetres away from the surface to which the clamp is attached. 
         [0097]    To attach a cable bundle to a surface of an aircraft structure using a saddle clamp  50 , firstly the clamp  50  is fixed to the surface using bolts through holes  54 . A device  10  is then applied to the cable bundle as described above, in a position such that two pairs of the tabs  23  can engage with the cut-away portions  62  when the device  10  and the clamp  50  are held together with the peripheral surface of the device against the upper surface of the saddle portion  56 . Once the device  10  has been so applied, it is held in position against the saddle clamp  50  and a jubilee clip  64  is fitted around the device/clamp combination as shown in  FIG. 6 . The band of the clip  64  passes through the passage  58  in the saddle clamp  50 , and through the slot  28  in the device  10 . The jubilee clip  64  thus holds the cables in position with respect to the device, and the whole bundle in place on the clamp  50 . 
         [0098]    It will be seen that the clamp  50  is arranged such that in use the central longitudinal axis of the cable bundle is parallel to the flat surface to which it is fixed. The axis of the cable bundle is centrally disposed between and above the extreme lateral edges defined by the upper surface of the arcuate saddle portion  56 . The angle, having as its vertex the central axis of the cable bundle, subtended by those extreme latter edges is greater than 45 degrees in  FIG. 6 . 
         [0099]    Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described. 
         [0100]    A dedicated hinge may be provided for allowing the movement of the first section relative to the second section. For example, in the embodiment shown in  FIGS. 2 and 3 , hinge  14  could be replaced with a snap-fit projection that operates in much the same way as projection  16 , and a separate hinge mechanism could instead be provided between part  14  and the extreme periphery of the device. 
         [0101]    The number of peripheral recesses  20  provided on the device  10  need not be five. For example, there could be six peripheral recesses. In this case space  30  need not be present. The size of the recesses and/or conductor spaces could be different from that set out above. The size of the device may be adjusted according to how many conductor spaces and/or recesses it has, and/or the diameter of the conductors it is intended to retain. The flat surfaces  26  need not be exactly flat, but could instead be slightly convex or concave. The location of the projection  16  and corresponding recess  18  could be different to that shown in the figures. A closure mechanism other than projection  16  and recess  18  could be used, for example an elastic band could be attached to one of the sections  12   a,    12   b,  for engagement with a formation such as a hook on the other of the sections  12   a,    12   b.    
         [0102]    The base of the saddle clamp may have more or fewer than two holes  54 . The number of recessed portions  62  may be more or fewer than four. 
         [0103]    Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.