GB2432710A

GB2432710A - Electrical-Cable Shielding

Info

Publication number: GB2432710A
Application number: GB0623869A
Authority: GB
Inventors: Gregory Neil Burland; Nicholas Jones
Original assignee: Icore International Ltd
Current assignee: Safran Electrical Components UK Ltd
Priority date: 2005-11-29
Filing date: 2006-11-29
Publication date: 2007-05-30
Anticipated expiration: 2026-11-29
Also published as: GB0623869D0; US20080296037A1; EP1964224A1; GB2432710B; WO2007063304A1; US7550666B2

Abstract

An electrical-cable transition where two or more bundles 23,24 of shielded cables 21 divide from a shielded, main bundle 22, is shielded from electromagnetic interference by a flexible shielding-element 25 of bare or covered metal mesh 2 wrapped round the transition to overlap (S), or be overlapped by, shielding of the branch bundles and interconnect electrically with it under straps 26. The flexible element may be an end-part of wrapped shielding 75 of the main bundle 70 that envelops the shielded branch bundles 71,72 and is closed onto them. Alternatively, it may be a separate shielding element 37;67 that is clamped by a clip or strap 36;68 onto the shielding 33;63 of the main bundle 30;60 to sandwich folded-tags 34t,35t;65t,66t drawn out from the ends of the branch-bundle shieldings 34,35;65,66, onto a metal ring or collar 39;64 through which the main-bundle cables pass before division into the branch bundles 31,32;61,62. The separate element 37;67 is closed tightly onto the individual branch bundles 31,32;61,62 by draw-strings, ties or other fastenings.

Description

24327 Electrical-cable Shielding This invention relates to

electrical-cable shielding, and is concerned particularly with bundles of electrical cables shielded against electromagnetic interference, and methods of such shielding of electrical-cable bundles.

In order to provide effective shielding of a bundle of electrical cables against electromagnetic interference it is necessary to ensure that the shield has electrical continuity and that connection to ground is of low resistance. Where there is to be a transition in the cabling run for dividing or branching the bundle into two or more smaller bundles, it is normal to interrupt the shield and insert a solid, usually metal, branching fitting to which the individual shields of the main and branch bundles are each attached to maintain continuity of shielding. A ground-bonding connection is usually made directly to the branching fitting.

The use of solid fittings as referred to above for cable-branching transitions has disadvantages in that they add weight and bulk to the cabling and increase costs. it is an object of the present invention to provide electrical-cable branching-transitions, and methods for providing such transitions, for which shielding against electromagnetic interference is maintained and the above disadvantages are, at least to a significant extent, overcome.

According to one aspect of the invention there is provided a method of providing an electrical-cable transition at which a shielded bundle of cables of a cabling run is divided into two or more shielded branch-bundles, wherein continuity of shielding of the cabling run against electromagnetic interference is maintained through the transition by wrapping a flexible shielding element round the branch bundles and the main bundle (that is to say, the bundle from which the branch bundles are divided) to envelop them all together at the transition as one and overlap, or be overlapped by, shielding of each of the branch bundles, and establishing electrical interconnection of the flexible shielding element with the shielding of the individual branch bundles.

According to another aspect of the invention there is provided an electrical-cable transition at which a shielded bundle of cables of a cabling run is divided into two or more individually-shielded branch-bundles, comprising a flexible shielding element wrapped round the branch bundles and the main bundle (that is to say, the bundle from which the branch bundles are divided) to envelop them all together as one at the transition and overlap, or be overlapped by, shielding of each of the branch bundles, and wherein the flexible shielding element is electrically interconnected with the shielding of the branch bundles for maintaining continuity through the transition of shielding of the cabling run against electromagnetic interference.

The method and cable-transition of the present invention avoid the need for a solid fitting in maintaining electrical continuity in shielding. This may be achieved where the flexible shielding element provides shielding of the main bundle before the division as well as enveloping the main and branch bundles at the transition, or where the main bundle is provided with its own individual shielding separate from that provided by the flexible shielding element, in which case the flexible shielding element may overlap or be overlapped by the shielding of the main bundle. In the latter case the flexible shielding element may be clamped individually to each of the main and branch bundles, or the shieldings of the main and individual branch bundles may all be clamped together with the flexible shielding element at the transition. The clamping may be achieved by one or more straps or clips encircling and compressing the cable-bundle, and may involve a degree of resilience. For example in the latter respect, the straps may have elasticity and/or a spring device or other contributor of resilience may be introduced into the cable-bundle itself.

The division of the main bundle of cables into the branch bundles is to be understood as being possibly of only one of the cables of the main bundle into one branch bundle and the remainder into one or more other branch bundles.

Therefore, a branch bundle' in the sense in which this terra is used herein, may be of a single cable or a plurality.

The flexible shielding element may be of woven, knitted or braided metal wires, or woven, knitted or braided metal-coated filaments, and may have an attached layer or layers of plastics or other electrically-insulating material.

Electrical-cable transitions, and methods for providing such transitions, in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

I

Figure 1 is a representative cross-section of tape used in the shielding of the electrical-cable branching transitions in each of the examples to be described; Figure 2 is illustrative of a plan view of the tape of Figure 1; Figure 3 is illustrative schematically of the weave of a wire-mesh that forms part of the tape of Figures 1 and 2; Figure 4 is a cross-sectional view of a bundle of electrical cables wrapped in the tape of Figures 1 to 3 for electromagnetic shielding of the cable-bundle; Figures 5 and 6 are illustrative of a first electrical-cable transition according to the invention; Figures 7 to 9 are illustrative of a second form of electrical-cable transition according to the invention; Figures 10 to 12 are illustrative of features and detail of a third electrical-cable transition according to the invention; Figures 13 and 14 are illustrative of another electrical-cable transition according to the invention; and Figure 15 is illustrative of a further electrical-cable transition according to the invention.

For simplicity of representation only a small number of electrical cables are represented as involved in the transitions shown in the drawings. In practice there are likely to be many more than represented.

The electrical-cable bundles involved in the shielded transitions to be described with reference to Figures 5 to 11 are all shielded from electromagnetic interference using shielding tape of the form illustrated in Figures 1 to 3 and now to be described.

Referring firstly to Figures 1 and 2, the shielding tape 1 used is of a three-layered, light-weight construction including a woven mesh 2 of bare metal-wire strands (for example, in a twill weave). The mesh 2 is sandwiched between inner and outer electrically-insulating layers 3 and 4 respectively. The layers 3 and 4 are formed by strips of plastics sheet (the thicknesses of the layers 3 and 4 and the mesh 2 are exaggerated in the drawings).

More particularly, the inner layer 3 is, for example, of polytetrafluoroethylene (PTFE) or polyvinyl chloride (PVC), and the outer layer 4 is of a hard-wearing plastics material, for example, a ketone-based resin such as polyetheretherketone (PEEK), for providing physical strength with resistance to abrasion.

As indicated schematically in Figure 3, the warp of the woven mesh 2 is formed by fine wire-strands 5 that run lengthwise of the tape 1, whereas the weft is formed by a fine wire-strand 6 running back and forth without break, in a narrow-fabric weave with the warp strands 5. The strands 5 and 6 are, for example, single wire-filaments or twisted pairs, of nickel-coated copper wire, and the strands 5 are fine enough that a group (in the case illustrated, of four) of them are drawn together through the dent-space of the loom in the weaving process; the gap G between the adjacent groups, resulting from the dents (and shown exaggerated in Figure 3), is small enough that it does not materially affect the shielding provided.

The inner layer 3 is of a width to cover the inside face 7 of the woven mesh 2 apart from throughout a longitudinal marginal strip 8 of the face 7 at one longitudinal edge 9 of the bare mesh 2. The outer layer 4 correspondingly covers the outside face 10 of the mesh 2 apart from throughout a longitudinal marginal strip 11 of the face 10 at the other longitudinal edge 12 of the mesh 2. An edge 13 of the layer 4 lies beyond the edge 9 of the mesh 2 to carry a strip 14 of upstanding fibres that abuts the edge 9.

The strip 14 forms in conjunction with a second strip 15 of upstanding fibres, a pair of interengaging elements of a selectively-disengageable fabric-fastening of the kind, such as that sold under the Registered Trade Mark VELCRO, in which hook-ended fibres of one element engage with upstanding loop-ended fibres of a second element; in this case, for example, the element 14 has the loop-ended fibres and the strip 15 has the hook-ended fibres. The strip 15, which is supported along the opposite edge 16 of the layer 4, has a central, red-coloured line 17 running throughout its length.

The mesh 2 together with the layers 3 and 4 and the strips 14 and 15 are retained in assembly with one another by stitching.

The tape 1 is used for electromagnetic shielding of a bundle of cables as will now be described with reference to Figure 4.

Referring principally to Figure 4, the tape 1 is deployed running lengthwise of the bundle of electrical cables 20 with the inner layer 3 abutting the cables 20 of the bundle. The tape 1 is now wrapped widthwise round the bundle by folding its longitudinal margins round the bundle as indicated generally by arrows A in Figure 1.

Wrapping of the tape 1 round the bundle is carried through to bring the margin 8 into overlap with the margin 11 and engagement of the element 14 onto the element 15 throughout the full length of the tape 1. Sufficiency of the area of engagement between the element 14 and the element 15 at each position throughout the length of the tape 1, so as to ensure that the tape 1 is correctly wrapped and secured, is confirmed if the red line 17 cannot be observed anywhere along that length.

When the tape 1 is correctly wrapped, the margins 8 and 11 of the woven mesh 2 are in hard abutment with one another so as to ensure that there is good electrical contact.

between them and that optimum shielding is provided. With such contact, there is complete closed-circuit encirclement of the bundle, and low-resistance connection of that circuit with the weft strand 6 and each warp strand 5. The strands 5 and 6 are clamped into couplings (not shown) at either end of the bundle to ensure good ground connection. Moreover, the shortest possible path for discharge from and lengthwise of the bundle is provided by the warp strands 5 running longitudinally of

B

the shielding tape 1; this is of especial importance for lightning protection.

The shielding tape 1 is used as described above for electromagnetic shielding of individual bundles of cables throughout their lengths, but may also be used as will be described, to establish screening according to the present invention throughout cable-transitions where a bundle is divided into two or more branch bundles. A first example of a screened transition according to the invention will now be described with reference to Figures 5 and 6.

Referring to Figure 5, the cables 21 of a shielded cable- bundle 22 in this example divide into two oppositely-directed branches or sub-bundles 23 and 24 (only a few of the cables in each bundle are shown schematically in Figure 5, and correspondingly in Figure 6, for simplicity of illustration) . The bundles 22 to 24 are individually shielded against electromagnetic interference using wrapped tape of the form of the tape 1 described above with reference to Figures 1 to 4. The electrically-conductive mesh 2 (not shown) of the shielding tape 1 of each bundle 22 to 24 is interconnected electrically with the corresponding mesh 2 of the shielding tape 1 of each other bundle 22 to 24 via a flexible shielding element 25. The element 25, as shown in Figure 6, is wrapped round the cables 21 where they divide from the bundle 22 into the bundles 23 and 24.

The shielding and protective tape 1 of each bundle 22 to 24 overlaps the element 25 throughout a limited end-region S indicated in Figure 5. More particularly, the inner insulating layer 3 of the tape 1 is removed throughout this region S so that the mesh 2 of the tape 1 is in face-to-face contact with the element 25. In this respect, the flexible element 25 may simply be, as suggested by the illustration of Figure 6, an element of bare electrically-conductive mesh or braid (for example a short length of mesh corresponding to the mesh 2 described above with reference to Figures 1 to 3), with which the mesh 2 of the overlapping tape 1 makes direct electrical contact.

Alternatively, and more in accord with the representation of Figure 5, it may be a short length of tape constructed in the same manner as the tape 1, having its outer protective layer corresponding to the layer 4 cut back within the overlapping regions S (or omitted altogether) so that good electrical contact is made there.

A strap 26, which may have a degree of elasticity, is tightened onto each individual, shielded bundle 22 to 24 within the region S, so as to urge and retain tight face-to-face electrical contact of the mesh 2 of the shielding tape 1 of that respective bundle, with the element 25.

This establishes the desirable low-resistance electrical interconnection of the electromagnetic shielding throughout the cable harness formed by the bundles 22 to 24.

A split-ring may be introduced under the mesh 2 and the element 25 within each overlapping region S so as to add resilience for enhancing the compressive force exerted, and therefore the clamping pressure urging tight face-to-face electrical contact, in that region.

A second form of transition is illustrated by Figures 7 to 9, and will now be described.

Referring initially to Figure 7, a main cable bundle 30 is divided into two branch bundles 31 and 32. The wrapped shielding tape 33 of the bundle 30 is terminated at the point where the division takes place to allow the bundles 31 and 32 to be branched off and provided with their own individual wrapped shielding tapes 34 and 35 respectively.

The shielding tapes 33 to 35 are interconnected electrically with one another to form a common bonding point by means of a single metal clamping-clip 36 that embraces the bundles 30 to 32 over their shielding tapes 33 to 35 at the point of division.

Shielding of the transition overall, involves an element 37 of the shielding tape which as shown more clearly in Figure 8 is inserted under the clip 36 and then folded back over it before being wrapped (as indicated by the arrows in figure 7)round the point of division and the bundles 31 and 32 to envelop them, as shown in Figure 9.

The longitudinal margins 38 of the wrapped element 37 overlap one another in hard abutment so as to ensure that there is good electrical contact between them for optimum shielding throughout the transition and its adjoining regions. The tape-element 37 is retained in place by drawing it tight round the bundles 30 to 32 and fastening it by using its fabric-fastening elements 14 and 15, a clip clamping round the clip 36, press-studs and/or draw-strings.

Low-resistance interconnection of the mesh 2 of the shielding element 37 with the mesh 2 of each shielding tape 33 to 35 is established by face-to-face contact with one another under the clamping-clip 36, or by means of one or more bonding straps between them. Although sufficient clamping pressure and consequent electrical contact may be achieved by tightening the clip 36 against the bundle of cables, the pressure and contact may be enhance by 1].

tightening it onto an underlying rigid or resilient member inserted in the transition.

More particularly, and as illustrated in Figure 8, the shielding tapes 34 and 35 are opened up at the ends of the bundles 31 and 32 and with the inner insulating layer 3 of each cut back, are folded in on themselves to form tags 34t and 35t. These tags 34t and 35t with the mesh 2 of each bare on the outside, are located over a metal ring or collar 39 (shown partly broken away) through which the cables of the bundle 30 pass for division into the two bundles 31 and 32 (to avoid the need for threading the collar 39 onto the cables, it may be slotted to allow the cables to be fed laterally into it, or split for fitting round them) . The end of the tape 33 of the bundle 30 is opened up and its insulating layer 3 is cut back, for folding over and making electrical contact with the tags 34t and 35t on the collar 39, so that the collar 39 provides a solid (or resilient) base against which the tags 34t and 35t are sandwiched with the element 37, under the clip 36.

The branch bundles 31 and 32 can be arranged beyond the transition to follow whatever path relative to the main bundle 30, is required for the harness installation. This has the advantage of allowing a greater degree of flexibility in manufacture and installation of the cable harness than in those circumstances where conventional transitions are used, and readily allows for adaptation of, in particular, the installed harness, to changing requirements for branch-bundle disposition and run.

Figure 10 is illustrative schematically of a similar shielded transition to that of Figures 7 to 9 where a main cable bundle 40 is divided into two branch bundles 41 and 42 and the shielding tapes 43 to 45 of the three bundles to 42 are individually clamped at their ends by clips 46 to 48. Shielding throughout the transition involves wrapping an element 49 of the shielding tape round the bundles 40 to 42 and securing it to envelop them where they divide and the region on either side. The electrical interconnection of the tapes 43 to 45 with the element 49, required in this case may be achieved using the methods illustrated in Figures 11 and 12, which will now be described.

Referring to Figure 11, low electrical-resistance interconnection is established in this example by flying leads 50 to 52 between the shielding tapes 43 to 45 and a common point 53 on the element 49, so that all shielding is brought to the same potential. In the case illustrated in Figure 12, on the other hand, the flying lead 50 is attached to a point 54 at one end of the element 49 whereas the flying leads 51 and 52 are attached to a point at the opposite end; this, which establishes the element 49 in series or in parallel with the shielding overall, precludes the possibility of the element 49 acting as an aerial/antenna.

A further example of a transition in which interconnection of the shielding is achieved without the use of flying leads, will now be described with reference to Figures 13 and 14.

Referring to Figures 13 and 14, a main cable bundle 60 is divided into two branch bundles 61 and 62 within the transition, and in emerging from within the wrapped shielding tape 63 of the bundle 60, passes through a metal ring or collar 64 (shown partly broken away) that projects out from within the tape 63. Initial portions of the shielding tapes 65 and 66 wrapped round the branch bundles 61 and 62, are folded in on themselves to form tags 65t and 66t for extending onto the collar 64 and making bare-metal contact with it. The shielding tape 63 of the main cable bundle 60 extends over the tags 65t and 66t where they make contact with the collar 64, and an element 67 of the shielding tape is wrapped tightly round this and the adjoining regions of the transition to envelop it. A strap 68 is used to pull the element 67 down tightly over the collar 64, the tape 63 and the tags 65t and 66t, clamping all of them onto the collar 64 and into good electrical surface contact with one another. A clip or tie may be used as an alternative to the strap 68, and draw-strings, ties, clips, press-studs, fabric-fastening may be used to hold the element 67 closed tightly down onto the individual branch bundles 61 and 62.

The situation in which there is only one cable in a branched bundle is illustrated in the case of the bundle 61 of Figures 13 and 14.

In certain circumstances it may be possible to effect the required shielding of the transition without the need for a separate shielding element enveloping the transition. An example of this is illustrated schematically in Figure 15, in which a main cable bundle 70 is divided into branched cable bundles 71 and 72, and where the shielding tapes 73 and 74 of the bundles 71 and 72 extend into the shielding tape 75 of the main bundle 70. The tape 75 is wrapped round the bundle 70 to extend over the division into the separate and separately-wrapped branch bundles 71 and 72, and so avoids the necessity for an additional shielding element to shield the cables where the branched transition is made. Clips or other means (not shown) of pulling the tape 75 tightly onto the shielded bundles 71 and 72 in establishing electrical interconnection between the tapes 73 to 75 (at individual positions or at a common point)and closing off the tape 75 round the bundles 71 and 72 would be provided.

Although the branching transitions of the examples described above involve just two branches, they may be readily adapted to provide for more branches than this.

Furthermore, there is an inherent flexibility that in general allows for a wide range of variation by choice of the relative orientations of the branches with respect to one another and the main bundle.

The shielded transitions described above have the advantage that the enveloping shield can be readily opened and removed from the harness simply by unwrapping it from main and branch cable bundles. This facilitates easy modification, inspection and repair of the bundles, and is achieved without use or introduction of the conventional metal or other specially-designed and -manufactured transition-component. Additionally, there is the advantage that the shielding and protection is achieved by wrapping an extra layer round the cable bundle, or (in the case of the example of Figure 15) of not requiring even this, so as to not increase the profile of the bundle materially.

Furthermore, there is the advantage that only a small range of different sizes of shielding tape is required to meet the requirements of a large range of different sizes and configurations of transition. With known transition products using metal or other hard components, a different product is generally required for each combination of main bundle size, number of branch bundles and their sizes and relative orientations. A range of different bundle diameters may be accommodated by providing for the possibility of adjustment of the degree of wrapped overlap of the shield.

With the methods and transitions of the invention electrical shielding protection and surge-current protection are provided through the junction zone. In this respect, the shields of the transition of the cable bundles can be brought to a single bonding point, so that a single high-current clamping device can be used. Also, any tendency for the transition-shield to act as an aerial/antenna can be suppressed by providing an electrical termination at each end of that shield. Any possibility of electrical discharge from high-curvature cut-ends of the wire of the shielding tape, and the risk of mechanical damage presented by them, can be reduced by hemming, or by encasing the ends.

Additional insulation and resistance to abrasion and other mechanical effects may be provided simply by adding additional layers to the shielding tape. Mechanical protection may be modified by the choice or mixture of fibres, and/or their diameters, within a textile layer.

More especially, fibres or other non-conductive fibres may be included between some or all of the wire strands 5 in the mesh 2 of the shielding tape 1 to improve the stability of the mesh 2.

As a further possible modification of the shielding tape 1, the layer 3 may be extended round the edge 12 of the mesh 2 to cover the strip 11. When the modified tape 1 is wrapped round the cable-bundle, the extended portion 21 of the layer 3 enhances the integrity of the electrical insulation of the mesh 2 from the cable-bundle, but separates the strip 11 of the mesh 2 from its direct electrical contact with the strip 8. It has been found that this separation does not materially detract from the operation of the shielding tape, especially in relation to high-frequency interference. The closed-circuit encirclement of the bundle by the mesh 2 is now of low impedance with a small capacitative component instead of being solely resistive.

In some circumstances it may not be necessary or desired to provide insulation between the bare mesh 2 and the cables 20, so then a saving in cost and weight can be achieved simply by omitting the inner insulating layer 3 from the tape 1.

Claims

Claims: 1. A method of providing an electrical-cable transition at

which a shielded bundle of cables of a cabling run is divided into two or more shielded branch-bundles, wherein continuity of shielding of the cabling run against electromagnetic interference is maintained through the transition by wrapping a flexible shielding element round the branch bundles and the main bundle (that is to say, the bundle from which the branch bundles are divided) to envelop them all together at the transition as one and overlap, or be overlapped by, shielding of each of the branch bundles, and establishing electrical interconnection of the flexible shielding element with the shielding of the individual branch bundles.

2. A method according to Claim 1 wherein the flexible shielding element provides shielding of the main bundle before the division as well as enveloping the main and branch bundles at the transition.

3. A method according to Claim 1 wherein the main bundle is provided with its own individual shielding separate from that provided by the flexible shielding element, and electrical interconnection is established between the shielding of the main bundle and the shieldings of the individual branch bundles and flexible shielding element.

4. A method according to Claim 3 wherein the flexible shielding element overlaps or is overlapped by the shielding of the main bundle.

5. A method according to Claim 3 or Claim 4 wherein the flexible shielding element is clamped individually to each of the main and branch bundles.

6, A method according to Claim 3 or Claim 4 wherein the shieldings of the main arid individual branch bundles are all clamped together with the flexible shielding element at the transition.

7. A method according to Claim 6 wherein the clamping of the shieldings of the main and individual branch bundles all together with the flexible shielding element is effected by clamping means for encircling and tightening onto them.

8. A method according to Claim 7 wherein the flexible shielding element is folded back over the clamping means to extend away from the main bundle.

9. A method according to any one of Claim 6 to 8 wherein the clamping at the transition is of the main and individual branch bundles and the flexible shielding element against an underlying rigid or resilient member.

10. A method according to Claim 9 wherein the rigid or resilient member is a ring or collar through which the one or more cables of the main bundle pass to the branch bundles.

11. A method according any one of Claims 6 to 10 wherein the shieldings of the branch bundles are extended as tags, and the clamping sandwiches them, the shielding of the main bundle and the flexible shielding element together in electrical contact with one another.

12. A method according to any one of Claims 3 to 11 wherein electrical interconnection between the shieldings of the main and branch bundles and the flexible shielding element is established by flying leads.

13. A method according to any one of Claims 3 to 12 wherein the flexible shielding element is an element of electrically-conductive mesh or braid.

14. A method according to any one of Claims 1 to 12 wherein the flexible shielding element is an element of tape that comprises a woven mesh of electrically-conductive strands.

15. A method according to any one of Claims 1 to 14 wherein each of one or more of the main and branch bundles is shielded by wrapping an elongate flexible tape widthwise round the bundle with the longitudinal margins of the tape overlapping one another, the tape comprising a mesh of electrically-conductive strands with some of those strands running longitudinally of the tape, and retaining the tape wrapped round the bundle as aforesaid with the mesh providing a closed electrical-circuit encirclement of the bundle via the overlap.

16. An electrical-cable transition at which a shielded bundle of cables of a cabling run is divided into two or more individually-shielded branch-bundles, comprising a flexible shielding element wrapped round the branch bundles and the main bundle (that is to say, the bundle from which the branch bundles are divided) to envelop them all together as one at the transition and overlap, or be overlapped by, shielding of each of the branch bundles, and wherein the flexible shielding element is electrically interconnected with the shielding of the branch bundles for maintaining continuity through the transition of shielding of the cabling run against electromagnetic interference.

17. An electrical-cable transition according to Claim 16 wherein the flexible shielding element provides shielding of the main bundle before the division as well as enveloping the main and branch bundles at the transition.

18. An electrical-cable transition according to Claim 16 wherein the main bundle is provided with its own individual shielding separate from that provided by the flexible shielding element, and there is electrical interconnection between the shielding of the main bundle and the shieldings of the individual branch bundles and flexible shielding element.

19. An electrical-cable transition according to Claim 18 wherein the flexible shielding element overlaps or is overlapped by the shielding of the main bundle.

20. An electrical-cable transition according to Claim 18 or Claim 19 wherein the flexible shielding element is clamped individually to each of the main and branch bundles.

21. An electrical-cable transition according to Claim 18 or Claim 19 wherein the shieldings of the main and individual branch bundles are all clamped together with the flexible shielding element at the transition.

22. An electrical-cable transition according to Claim 21 wherein the clamping of the shieldings of the main and individual branch bundles all together with the flexible shielding element is effected by clamping means which encircles them tightly.

23. An electrical-cable transition according to Claim 22 wherein the flexible shielding element is folded back over the clamping means to extend away from the main bundle.

24. An electrical-cable transition according to any one of Claim 21 to 23 wherein the clamping at the transition is of the main and individual branch bundles and the flexible shielding element against an underlying rigid or resilient member.

25. An electrical-cable transition according to Claim 24 wherein the rigid or resilient member is a ring or collar through which the one or more cables of the main bundle pass to the branch bundles.

26. An electrical-cable transition according to any one of Claims 21 to 25 wherein the shieldings of the branch bundles are extended as tags, and the clamping sandwiches them, the shielding of the main bundle and the flexible shielding element together in electrical contact with one another.

27. An electrical-cable transition according to any one of Claims 18 to 26 wherein electrical interconnection between the shieldings of the main and branch bundles and the flexible shielding element is established via flying leads.

28. An electrical-cable transition according to any one of Claims 18 to 27 wherein the flexible shielding element is an element of electrically-conductive mesh or braid.

29. An electrical-cable transition according to any one of Claims 16 to 27 wherein the flexible shielding element is an element of tape that comprises a woven mesh of electrically-conductive strands.

30. An electrical-cable transition according to any one of Claims 16 to 29 wherein each of one or more of the main and branch bundles is shielded by an elongate flexible tape that is wrapped widthwise round the bundle with the longitudinal margins of the tape overlapping one another, the tape comprising a mesh of electrically-conductive strands with some of those strands running longitudinally of the tape, and the tape is retained wrapped round the bundle as aforesaid with the mesh providing a closed electrical-circuit encirclement of the bundle via the overlap.

31. A method of providing an electrical-cable transition at which a shielded bundle of cables of a cabling run is divided into two or more shielded branch-bundles, substantially as hereinbefore described with reference to the accompanying drawings.

32. An electrical-cable transition at which a shielded bundle of cables of a cabling run is divided into two or more individually-shielded branch-bundles substantially as hereinbefore described with reference to the accompanying drawings.