This invention relates to connection devices for use with flat cables for power distribution, typically of the type designed for uudercarpet use.

A connection system which can be quickly and simply installed on site, but which can be adapted for use iu many circumstances is clearly useful. British Patent Application 2,165,101 describes such a connection device for use with flat cables of the type described iu British Patent Application 2,165,086. This device has several disadvantages. Firstly, the use of insulation displacement contacts (IDC) to electrically connect to the conductors iu the cable necessitates the use of an iusulative separation plate between the earthing screen of the cable and the current carrying conductors. This has to be iuserted at the connection device to prevent the IDC's from penetrating too far. Secondly, the means for clamping the cable in position is the same as that used for making the IDC's and no separate strain relieving device is provided. Thirdly, it is possible with coutacts of the IDC type to connect live to ueutral between two cables at a connection device. And fourthly, the protective steel cover strip laid over the cable can become displaced.

The present invention in its various aspects is defined iu the appended claims to which reference should now be made.

A preferred embodiment of the invention comprises a pedestal unit on which a dual outlet 13 amp 240 Volt socket can be mounted. The pedestal is formed by a base assembly with screw terminals for receiving electrical connections to cables , a clamping assembly secured to the base assembly, and a cover assembly secured solely to the clamping assembly. Contact is made with the conductors in the cable prior to its insertion iu the pedestal unit by the use of ring staples through the cable. The staples through the live aud ueutral conductors are offset slightly to one side. This matches an equivalent offset of the screw terminals iu the base assembly and is used to ensure that connection can only be made with the correct electrical polarity. The protective steel cover for the cable is

held iu positiou by the screw terminal for the earth conductor. The clamping assembly holds the cable and protective steel cover iu position at the edge of the base assembly aud provides for access to be made to the screw terminals iu the base assembly. The cover assembly is designed to receive a dual outlet 13 amp socket. The pedestal unit can alternatively be used solely as a junction box between two cables or as a transition box between a flat cable aud a conventional round cable.

The invention will now be described iu more detail by way of example with reference to the drawings, iu which:-

Figure 1 shows a section through a twin and earth flat power cable designed for uudercarpet use;

Figure 2 is an exploded section of the flat power cable, showing the individual components of the cable;

Figure 3 is a plan view of the cable, prepared for the insertion of ring staples

Figure 4 is an exploded perspective view of the template used to mark out the cable before trimming it and to locate a punch for holes to be made for the ring staples;

Figure 5 is a plan and side view of a ring staple prior to insertion in the cable;

Figure 6 is a plan view of the assembled pedestal unit;

Figure 7 is a side sectional view through the assembled pedestal unit;

Figure 8 is an end sectional view through the assembled pedestal unit;

Figure 9 is an exploded perspective view of the entire pedestal unit with incoming cables;

Figure 10 is a cross-section through one leg of a ring staple iuserted into a flat cable; aud

Figure 11 is an exploded perspective view of the template used to make large holes in the insulation between live aud ueutral conductors aud to make the central hole iu the stainless steel cover strip.

The flat uudercarpet cable shown iu Figure 1 comprises three conductors, a live conductor 12, a neutral conductor 14 and an earthing couductor 26. The live aud neutral conductors 12 aud 14

are typically 0.25 mm thick, about 20 mm wide and made from copper for use with 240 volts at a 32 amp current rating. The live aud neutral conductors are sandwiched between two laminated strips 16 and 18 which form an inner iusulation sheath 15 aud are typically 60-65 mm wide. The laminated strips are typically constructed from a polyester layer on the side furthest from the conductors, a fire resistant vinyl layer aud a heat-sealable adhesive layer on the side nearest to the conductors. The conductors are separated by a gap of 10-15 mm where the two strips are bonded to each other 20. The strips are also bonded to each other at the outside edges of the conductors 22. The live aud ueutral conductors are thus contained in a sealed insulated package. The earthing conductor 26 is approximately the same width as the complete package containing live aud neutral conductors and cau be about half the thickness of the live and ueutral conductors. The earthing conductor cau be lightly bonded to the conductor package, but it should be separable by hand.

An outer sheath is formed around the assembly of inner sheath and earthing conductor 26. This is made of two further strips of laminate 30 aud 32, similar to that used to form the inner sheath, but about 20 mm wider. The edges of the strips 34 are bouded together to produce a sealed package. The upper strip 32 is preferably bouded to the earthing conductor 26 and the lower strip 30 can be lightly bouded to the inner sheath.

Indications of the electrical polarity of the conductors are preferably printed on the outer sheath. This is necessary when electrical connections are made to the cable.

To prepare the cable for insertion iu a connection device the template illustrated in Figure 4 is used. This enables the ends of a cable to be trimmed and holes made through the conductors as shown in Figure 3. The template consists of top and base members 60 and 61 fixed rigidly together with screws through the holes 63. A ridge 62 runs along one side of the template base member. This is used to locate the cable correctly in the base member. Six holes are provided where holes are to be made in the cable, namely earth conductor holes 64, live conductor holes 65 aud neutral conductor holes 66.

The top member of the template has holes corresponding to the

conductor punching holes 64, 65, 66 in the base member. A punch of the same diameter as the holes is provided. At either eud of the top member, on its underside, is a lug 60A with a curved profile on the side furthest from the centre of the template.

There are several scoring grooves on the top member. Four of these 67 run parallel to the cable direction. A three part groove 68 runs across the centre of the member. Two further two part grooves 69 run across the member between the earth conductor punching hole and the live aud ueutral conductor punching holes.

* To prepare a cable, the template is placed ou the floor where a pedestal unit is to be located. The cable slides sideways into the template past the lugs 60A with both live aud ueutral conductors coinciding with their punching holes in the template, the ueutral conductor side of the cable abutting against the ridge 62 aud the live conductor side abutting against the lugs 60A. Using the hole punch, the six contact holes 64, 65, 66 iu the conductors are made. The holes 36 aud 37 iu the live and ueutral conductors are not equidistant from the sides of the cable, hole 36 being nearer to the side than hole 37. This will ensure that when, the cable is brought into a connection device it will only be possible to fix it in one position, thus ensuring that the electrical polarity of the whole system is preserved.

A scriber is inserted into each of the scoring grooves 67, 68 aud 69 in turn and the cable marked along the length of the grooves.

The cable is now removed from the template and cut in half along the central scored line made via grooves 68. The side insulation is trimmed back 35 along the marks made via the grooves 67, aud finished off with a 45° angled cut to the side of the cable package. The light bonding on the lower insulation strip is broken and the strip cut back approximately as far as the trimmed section. The earth conductor is trimmed back to positiou 39, corresponding with the marks made via grooves 69. It is then folded back. This allows a further larger hole 40 to be made in the insulated gap 15 between the live and ueutral conductors with a second template, illustrated in Figure 11. This second template comprises a base member 73 aud a top member 73A typically made from plastics material with stainless steel inserts aud held together

with screws through the holes 80.

The base member is generally flat with two ridges 74 and 75 running transversely across it aud an "L" shaped recess 83 at one end. Two large holes 76 are located between these two ridges along with three locating lugs 77, 78 and 79. A punch is provided to fit these holes 76. A single hole 84 is located iu the "L" shaped recess.

The top member has two large holes 80 corresponding to the large holes 80 in the base member and a smaller hole 86 corresponding to hole 84 in the base member. The lugs 77, 78 aud 79 are not covered by the top member.

In use, cable ends are introduced into the template iu the direction of arrow 81. The hole 37 already made in the neutral conductor fits over the central lug 78, aud the hole 36 in the live conductor fits over either the lug 77 or the lug 79 dependent on which of the two cable ends is being prepared. The side of the cable adjacent to the live conductor abuts against either ridge 74 or ridge 75. A large hole 40 is then made through the iusulated gap 15 between live aud neutral conductors with the punch provided, the punch being iuserted iu one of the holes 76 depeudaut upon the position of the cable in the template. The centre of the hole 40 is offset from the centre of the hole 38 away from the end of the cable 41. This offset is necessary because in the connection device the earth connection is vertically displaced from the plaue of the live and neutral connections and the hole 40 has to fit over the post 42 providing this vertical displacement, whilst the hole 38 has to fit concentrically on top of the post 42. The stainless steel cover strip is trimmed to the length required to cover the cable aud iuserted into the "L" shaped recess at 90° to the insertion direction of the cable. The hole puuch used with the first template is used to make a central hole iu this cover strip.

The type of ring staple required for electrical connection to be made to the cable is shown iu Figure 5. In this example, the staple is a ring 42 of about 12 mm diameter. The thickness of the ring for this particular version of the flat cable should be at least 0.8 mm. The central hole has a diameter of about 5.5 mm, i.e. approximately the same diameter as holes 36, 37 aud 38, in the

cable. The staple is made from copper or some other good conductor. There are five legs 31 attached to one side of the ring. These legs have a constant cross section in the direction of the axis of the ring aud heuce have flat ends.

The staples are positioned with a staple insertion tool over holes 36, 37 aud 38. When pressure is applied to the staple, forcing the legs against the cable, the flat ends of the legs 31 are forced through the conductors, displacing material from the, conductor aud folding it round iu the same direction as the staple leg is folded by the insertion tool. A cross-section through a staple aud one of its legs 31 iuserted through the live conductor 12 of a flat cable is shown iu Figure 10. As cau be seen generally at 70, the flat end of the staple leg has broken through the conductor material 12. The leg has been folded through approximately 90°, and in doing so has folded the adjacent conductor material through 180°. Thus the conductor material is trapped between the staple leg 31 aud the ring section 42 of the staple, aud a greater surface area for electrical contact is made than is the case with contacts of the IDC type.

The prepared cable thus comprises an end section of cable with side insulation trimmed away 35, three holes 36, 37 and 38 to take ring staples through the three conductors, the earthing conductor cut back from the eud of the cable to permit access to the holes in the live and neutral conductors, a larger hole 40, iu the inner sheath between the live and ueutral conductors, coinciding with but offset from hole 38, aud ring staples inserted through each of the three holes 36, 37 and 38.

The pedestal unit which forms the connection device is shown in Figure 6.

The base assembly 49 of the connection device comprises two recesses 43 slightly wider than the trimmed width of a prepared cable end, three screw terminals or bosses 44, 45 and 46 iu each recess with solid inlaid electrical connections made between the opposed screw terminals iu the two recesses. The screw terminals 44 aud 45 for live and neutral connections are uot equidistant from the sides of the recesses; this is to accommodate the transverse offset of the ring staples iuserted iu the live aud ueutral

conductors of the cable. The offset of the terminals in one recess is the mirror image of the offset in the other recess, hence once a cable end has been prepared it will only fit into the connection device in one direction. The two earth terminals 46 are positioned centrally with respect to the sides of the recesses aud are vertically displaced from the plane of the live and ueutral terminals by a plastics post which is the height of the recess.

Four small locating lugs are provided for positioning the stainless steel strip which lies across the top of the earthing strip aud plastics part aud is hence above the- recess. These lugs also serve to positiou the clamping assembly 50, as does a large recess 71 at one end which takes a locating lug from the clamping assembly. Four holes 47 are provided iu the base assembly 49 to take screws or bolts for fixing the assembly to a flat surface. A further four holes 48 are provided with tapped metal inserts to take screws holding down the clamping assembly 50.

Next to the recesses 43 for receiving the cable, the sides of the base assembly are cut away at an angle 51 to give the clamping assembly 50 a surface to clamp the incoming cable against.

The clamping assembly 50 comprises a solid plate with a number of holes in it. Six holes are located iu positiou directly above the screw terminals in the base assembly, the holes for live aud neutral conductors being slightly offset from one end of the assembly. Four holes 48 are provided to take bolts through to equivalent holes in the base assembly.

Two holes with tapped metal inserts are provided to fix the cover assembly 52 onto the clamping assembly. One locating lug 72 protrudes downwards from the base of the assembly at one end to fit into the recess at oue eud of the base assembly. Thus there is only oue orientation in which the clamping assembly cau be fixed to the base assembly. Four small recesses are provided on the underside of the clamping assembly to fit the four locating lugs on the base assembly which are used to position the stainless steel strip.

At the sides of the assembly, where the cables enter the pedestal unit, a rectangular strip of plastic 53 protrudes downwards. This locates over the cut-away section 51 of the base

assembly and when in position will clamp the cable securely in positiou. The corner of this adjacent to the cut-away section 51 is radiused to prevent undue damage to the cable when iu positiou.

The cover assembly 52 is designed to fit completely over the base aud clamping assemblies. The assembly 52 has a large rectangular hole 54 through it to allow access to the screw terminals iu the base assembly aud to take a staudard dual outlet 13 amp socket unit. Two holes 55 are provided for fixing the socket unit to the oover assembly aud two further holes are provided to take bolts through to the clamping assembly.

In use, the base assembly 49 is screwed to a flat surface using screws through the holes 47. Prepared cable ends are introduced into the recesses 43 in the base assembly. Note that the offset of the live and neutral terminals iu the two recesses means that two different templates portions are required to prepare the two cables entering the unit as described above. Colour coding on these templates corresponding with colour coding on the cable ensures that cables are prepared aud instailed with the correct polarity.

The ring staples through the live and neutral conductors are positioned above screw terminals 44 and 45 respectively. The large hole 40 through the inner sheath of the cable fits over the plastic post 42. The ring staple through the earth conductor fits over the screw terminal 46 on top of the plastic post 42. Therefore, no separation plate between the earth conductor aud the live aud neutral conductors is required. This is because the earth conductor has been cut back away from the ring staples iu the live and neutral conductors, aud it is vertically displaced from the live aud neutral conductors in the connection device by the plastic post 42. The steel cover 56 for the cable has a small hole in its end aud this also is positioned above the post 42. Screws are then used to fix the live, ueutral aud the earth aud steel cover plate to their respective terminals. When two cables are used they will be electrically connected by the solid inlaid connections between the screw terminals in the base assembly.

The clamping assembly 50 is then positioned over the base assembly using the large locating lug 72 provided. The plastic strips 53 on the clamping assembly press down on the steel cover

strip 56 aud cable, forcing them against the cut-away sectiou 51 on the base assembly. The cable and steel cover strip are thus lifted from the surface to which the base assembly is attached, to the plane of the upper surface of the base assembly. The area of the cable aud steel cover strip between the plastic strips 53 and the cut-away sections 51 thus forms a ramp between the two planes. Two mechanisms are, therefore, in operation in clamping the cable iu position, the pressure caused by the plastic strips 63 pressing agaiust the cut-away sections 51, and the resistance to plauar deformation of the cable and steel cover strip. When the fixing screws are put in holes 48, the cable aud steel cover strip will be clamped in position by the plastic strips 53 aud auy strain put on the cable will be taken by the clamped sectiou, not just by the screw terminals iuside the pedestal unit.

When the clamping assembly is in place electrical jumper leads 57, 58 aud 59 are secured to the screw terminals iu the base assembly.

The cover assembly is then secured to the clamping assembly with the two bolt holes provided. It covers the entire base and clamping assemblies aud thus gives additional strength to the pedestal unit whilst forming a second insulative layer around the base and clamping assemblies. The 13 amp dual outlet socket unit is then connected to the electrial jumpers 57, 58 aud 59 and fixed onto the cover assembly with screws through holes 55.

The pedestal unit described above provides a versatile aud robust device for connecting flat uudercarpet cables. The cables as shown iu Figures 1 aud 2 are constructed with a double layer of insulation and the upper surface is covered by the earthing couductor. Their use is recommended with a steel cover strip 56 which should be held iu positiou at any connection device the cable enters. Electrical connection to the cables is made with staples which have flat ended legs 44 illustrated in Figure 5. These will ensure that a large amount of couductor material is displaced by the staple aud folded round in the same direction as the staple legs thus making good electrical contact. The assymetric positioning of these staples iu the cable is used to maintain the electrical polarity of the system by corresponding to the equivalent assymetric

positioning of terminals 44,45 and 46 inside the connection device. A clamping device comprising protruding strips 53 on the clamping assembly 50 and cut away sections Sir on the base assembly provides a means of relieving strain on the cable between the terminals inside the connection device and the Incoming cable. A cover assembly 52 is provided to add strength to the pedestal unit and to form a second iusulative layer around the base and clamping assemblies. This cover cau only be fixed to the pedestal when the clamping device is in position. The pedestal forms a versatile unit for use with the cable, being able to join lengths of cable, attach electrical sockets or perform the transition from flat to conventional cable.