In this specification,"connector fitting"may mean a link formed between one cable length and another cable length or lengths. By connector fitting it is also meant the forming of an electrical connection in a first electrical cable, such as a plug, socket or terminal end, which may subsequently be used to connect the first cable to a compatible electrical connection in another cable or electrical fitting (either permanently or temporarily).

It is desirable to form electrical connectors and connector fittings in cables for many applications. It may be desirable to provide power supplies in fairly inaccessible places such as tunnels and shafts, building conduits etc.

When laying such cables it may be difficult to form junctions or break out cables in situ. In order to overcome these difficulties the cables may be supplied in pre-cut lengths, so that the cables and junctions may be assembled and linked.

One way of assembling/linking these fittings is by means of pre-fitted or pre-moulded plug and socket type connector fittings.

As well as cables for running another power supply through tunnels, building shafts etc., it may be desirable to provide a power supply within the tunnel or shaft, for example for use in an emergency or during repairs. The cable may be run through the tunnel, and, in order to tap the supply, sockets may be provided at intervals along the length of the cable. The sockets may be moulded as plug and/or socket type connector fittings. In order to tap the power supply, the lights, tools etc. have their own associated cable with a compatible connector fitting which cooperates with the connector fitting provided on the cable.

Power cables for use in buildings and tunnels need to conform to stringent safety and fire performance standards, such as BS 6387. Obviously, to maintain safety and integrity, any connector fittings will have to conform to the same standards. In addition, the connector fittings in the cable must also be secure, firm and resistant to the ambient conditions where the cable is located; for example, the link may have to be resistant to attack by water, dust or other contaminants.

Previously, in order to provide a secure connection, it has not been possible to choose compatible materials for both the cable coating and the connector (socket) fitting without having to use materials that are extremely expensive, or materials with inferior quality (for example with inferior wear or fire resistance). One method of solving this problem is provided by GB 2 249 223, which describes a method of connecting cables using a cured rubber fitting. The cured rubber fitting and the material used for the cable coating are not compatible because the temperature at which the rubber fitting is cured is high enough to melt the cable coating; the method uses a preformed sleeve placed between the cable and fitting prior to curing the rubber fitting.

The preformed sleeve provides a firm connector. However, the pre-forming and fitting of this sleeve prior to curing the rubber fitting is a time consuming process which lengthens and complicates the manufacturing process.

According to the present invention there is provided a method of forming a connector fitting on an electric cable, the electric cable comprising an outer sheath of plastics material and an insulated conductor, the method comprising the steps of : [a] removing a section of outer sheathing to expose a portion of the insulated conductor;

[b] electrically connecting the conductor of the insulated conductor to connector terminals; [c] enclosing at least a portion of the conductor terminals, the exposed portion of the insulated conductor and a portion of the adjacent outer sheath in a mould for a connector housing; and [d] injecting a plastics material into the mould to form the housing; the plastics material being compatible with the plastics material of the outer sheath, whereby the housing is directly bonded onto a portion of the outer sheath.

The plastics material that forms the housing and the plastics material of the outer sheath may be of identical specification or formulation. The layer of plastics material that forms the housing and the plastics material that forms the outer sheath may be of different specification or formulation.

Preferably the layer of plastics material that forms the housing and the layer of fire resistant plastics sheathing material are of flame-retardant and/or fire resistant material.

By the"fire-resistant"plastics material and"fire- resistant connector fitting"it is meant materials resistant to temperatures associated with a fire. For example, the electric cable on which the connector fitting is injection moulded may sufficiently fire resistant to conform to British Standard BS 6387 CAT C, W and Z. In this case, the injection moulded fire resistant plastics material which forms the housing should have similar fire resistant properties.

Preferably the layer of plastics material that forms the housing and the layer of fire resistant plastics sheathing material have limited reaction in terms of production of corrosive or acid gases and of smoke, when compared to other materials such as PVC.

The plastics material that forms the housing and the plastics material of the outer sheath may be a zero halogen low smoke type material. The zero halogen low smoke type material may be, for example, a filled, flame retardant mixture of thermoplastic polymers blended to give desired physical characteristics and reaction to fire. The zero halogen low smoke type material may be a thermoplastic filled EVA flame-retardant compound, for example, an EVA (ethylene vinyl acetate) based material including a high proportion of a flame retardant material such as, for example, aluminium trihydrate (ATH), or magnesium hydroxide. A suitable plastics

material is that known as DP3 and sold under the Registered Trade Mark OHLS.

Preferably the plastics material that forms the housing is a flame-retardant halogen-free low smoke and fume thermoplatic compound such as the plastics material sold under the Registered Trade Mark ECCOH-5500 by Enviro Care Compounds, of Niels Leuchs vei 99 N1343 Eiksmarka, Norway.

ECCOH-5500 is a plastics material for which there is a range of plastics materials suitable for the outer sheath.

These include ECCOH-5500 itself, DP3 and other plastics materials commonly used as cable sheathing. The connector housing is directly bonded onto the plastics sheath.

The ECCOH-5500 formulation has a Mooney Viscosity at 140°C of 25 (other plastics materials such as DP3 have a value of the order of 45). This much lower Mooney value of ECCOH- 5500 allows processing at faster extrusion speeds and in some cases with a PVC screw thereby remarkably improving the speed and efficiency of the injection moulding process compared to other plastics materials.

It is expected that the ECCOH-5500 formulation will show improved fire-resistant capabilities compared to other plastics materials. It is expected that the polymers and

filler systems will form a stable ash when the connector burns on exposure to fire.

The plastics material that forms the housing and/or the plastics material of the outer sheath may be of the ECCOH-5500 material.

Preferably the step of electrically connecting the conductor of the insulated conductor to connector terminals makes a connection between the conductor and at least one connector terminal.

Preferably the step of electrically connecting the conductor of the insulated conductor to connector terminals makes a connection between the conductor and a connector terminal in a connector fitting mould insert section. The mould insert section and electrical connection may then be enclosed within the housing formed by injection moulding the plastics material.

The connector terminal (which may be housed in the connector fitting mould insert section) may comprise one part of a two-part reversible electrical connection. Thus, if the connector terminal is housed in a connector fitting mould insert section the connector fitting mould insert section may act as a template that ensures that the shape of the connector

fitting (or the configuration of electrical terminal or terminals within the fitting) will be compatible with a similar connector fitting that includes or is provided with the other part of the two-part reversible electrical connection. For example, the insert section may be provided with at least one pin section of a socket-and pin-type electrical connection. A connector fitting subsequently formed will be compatible with a connector fitting including the corresponding socket section.

Preferably the connector fitting mould insert section is made of ceramics material. The ceramics material may lead to improved electrical properties.

The connector fitting insert section may provided with a fuse.

According to the present invention in a further aspect there is provided a method of forming a fire resistant connector fitting in a cable, the cable comprising a layer of fire resistant plastics sheathing material surrounding at least one insulated conducting core, the method comprising the steps of : [a] making an electrical connection to the conducting core;

[b] enclosing the connection in a housing; in which the housing is formed by injection moulding a fire resistant plastics material compatible with the layer of fire resistant plastics sheathing material.

In a further aspect, the present invention provides a connector fitting made by any of the above methods.

Preferably, the connector fitting is fire resistant.

Preferably, the connector fitting is made of ECCOH-5500 material.

In a still further aspect, the present invention provides a cable including a plurality of spaced connector fittings formed on the cable by any of the above methods.

Preferably, the cable and connector fittings are fire resistant. Preferably the cable and/or connector fittings are made of ECCOH-5500 material.

Embodiments of the present invention will now be described with reference to the attached drawings, in which: FIGURE 1 is an exploded view of two embodiments of a cable linkage formed using connector fittings according to the invention;

FIGURE 2 is a sectional view of the first embodiment of Fig. 1 along the line Z-Z of Fig. 1; FIGURE 3 is a sectional view along the line X-X of Fig. 2; FIGURE 4 is a sectional view along the line Y-Y of Fig. 3; FIGURE 5 is an exploded view of a cable end showing the different layers of insulation; FIGURE 6 is a sectional view of the cable connector fitting linkages of Fig. 1, cutaway in part; FIGURE 7 is a sectional view of the second embodiment of Fig. 1 which is known as a"breakout". The section is taken along line X-X of Fig. 7A; FIGURE 7A is a plan view of the second embodiment of Fig. l; FIGURE 8 is a sectional view of the breakout of Fig. 7 taken at 90° to the section of Fig. 7 (along lines Y-Y of Fig. 7A);

FIGURE 9 is a partial schematic diagram of a manufacturing process for forming connector fittings in a cable by a method which is one embodiment of the present invention; FIGURE 10 is a sectional view of a further embodiment for a connector fitting suitable for use with a coupling nut; FIGURE 11 shows a cross section of the embodiment of figure 10 with a breakout (also according to the invention) held in place by a coupling nut; FIGURE 12 is a sectional view of a still further embodiment for a connector fitting suitable for use with a coupling nut; and FIGURE 13 shows a cross section of the embodiment of figure 12 with a breakout (also according to the invention) held in place by a coupling nut.

Figures 1 and 2 show cable connector fittings or linkages. The primary cable (1) is a length of standard cable designed to provide mains power in, for example, a tunnel.

At periodic intervals along the length of cable (1),

connectors (2) are provided so that connections can be made to, and/or power can be tapped from, cable (1). One method of tapping the power supply is via second cable (4) which terminates with breakout plug (3). Breakout plug (3) mates with connector (2), to provide a secure electrical connection which is resistant to contamination by dust and moisture. It should be noted that both the connection between cable (1) and connector (2) and that between second cable (4) and breakout (3), are embodiments of the present invention.

Figures 3,4,5 and 6 show further views of connector (2). Cable (1) includes a plurality of insulated conducting cores (10). These cores are surrounded with further layers (11,12) of, for example, one or more of a further insulation layer of silicone rubber of XLPE etc., a mica tape layer, and/or a low smoke sheath bedding layer. These further layers (11,12) are then surrounded by a metal layer of galvanised steel wire armour (13). The metal layer is surrounded by outer sheath (5). The outer sheath is made of a zero halogen, low smoke emitting material, for example the EVA based material including a high proportion of aluminium trihydrate sold under the Registered Trade Mark OHLS.

Connector (2) is provided by the following method. The outer plastics sheath of OHLS insulation (5) is removed. The amount of the sheath that is removed depends on the length of the connector fitting. The galvanised steel armour layer (13) is scored and then removed to expose the interior further layers (11,12). These are then cut away to expose insulated conducting cores (10). The two extreme ends (not shown) of cable (1) are then pushed together, forcing the conducting cores (10) to become separated from each other. The core insulation removed from one of these conducting cores (17) to expose the copper conductor in two parts (18,19). A connector fitting mould insert section, which is a preformed ceramic socket insert (20) provides the socket connector (2) to which breakout (3) may be reversibly mated. The ceramic socket insert (20) includes connector terminals, which are conducting brass socket inserts (21,22). One exposed part (18) of conductor core (17) is connected to brass socket insert (21). The second part (19) is connected to brass socket insert (22). The connections may be wrapped with a layer or layers of mica tape (not shown). An earth strap (14) is attached to the cut ends of the steel armour layer (13) at each end of the connection; each end of earth strap (14) is held in place by steel clamping band (15). A metal plate may be used instead of the earth strap (14). The metal plate can

act as a support frame and heat deflector and provides improved fire integrity performance.

In another embodiment (not shown), the ceramic socket insert (a connector fitting mould insert section) is provided with insulated conducting wire tails. These tails may be attached to insulated conducting cores via C'crimps, which function as the connector terminals. The C'crimps are crimped onto insulated conducting core (10), thus providing an electrical connection between the conducting tail (and thus the ceramic socket insert) and the conducting cores.

Figure 5 shows an exploded view of the cut made in one end of cable (1). This drawing demonstrates how the outer layers (11,12,13,5) are cut away in a stepwise fashion to leave sufficient area of galvanised steel armoured layer (13) to allow earth strap (14) to be firmly attached to the armour layer (by clamping bands (15)) without slippage.

Once the electrical connections have been made (as described above) the whole cable connector section [which may include the area between the cutaway ends of cable (1), the exposed insulating conducting cores (10), the ceramic socket insert (20), the cutaway conducting core (17), the mica tape,

the conducting tails and the C'crimps (if present)] is enclosed within a moulding tool (not shown). Plastics material is injection moulded into the moulding tool to provide the housing of connector fitting (2). High compatibility between the plastics sheath layer (5) and the injection moulded plastics material that forms the housing results in a firm and secure connector (the adjacent portions of the moulded connector fitting (2) and sheath layer (5) are firmly connected). The plastics material may be of exactly the same specification as that of plastics sheath layer (5).

A suitable material is the DP3 plastic formulation sold under the registered mark OHLS.

Injection moulding processes are well known but it will be appreciated that some minor modifications to tools may be necessary to suite the flow characteristics of the plastics material that is used. Such modifications are within the ability of those skilled in the art. If aluminium trihydrate (ATH) is present as. flame retardant in the plastics material the temperature must be kept low enough to prevent activation (i. e. water release) of the ATH.

In a further embodiment the plastics material is that under the Registered Trade Mark ECCOH-5500 by Enviro Care

Compounds. This is sufficiently compatible with the DP3 OHLS formulation so that fitting (injection moulding) by the method according to the invention results in a firmly secured connector as with the DP3 embodiment discussed above.

In a still further embodiment both the plastics sheath layer (5) and the injection moulding plastics material that forms the housing of the fitting are of ECCOH-5500 material.

After moulding, the connector fitting is then removed from the moulding tool and inspected, the finish of the connector fitting housing may be deflashed if necessary.

It will be seen that in the described embodiment, connector fitting (2) is a female socket. Breakout plug (3), which is, in this embodiment, a male fitting, is formed on the end of cable (4) by a similar method see Fig. 7,7A and 8.

In this embodiment it is necessary to remove the insulating layers from only one end of the cable.

The insulating layers are removed in the same way as for the previously described embodiment. Three insulated conducting cores (10) are taken from cable and the insulation

layer removed. A core (10) is attached to each of pin fittings (31,32,33) so as to form three electrical connections (in this embodiment, pin fittings (31,32,33) function connector terminals). The three pin fittings (31, 32,33) may be held in place by a ceramic insert section (not shown). The connections may also be wrapped in mica tape prior to injection moulding, in the same way as the previous embodiment. Once the connections, insert and tape have been applied the components are tested and subsequently placed within a moulding tool. The housing of breakout plug (3) is formed by injection moulded plastics material in the same way as for the previous embodiment.

Figure 9 shows a partial schematic diagram of a production line for producing connector fittings of the present invention (by a method which is a still further embodiment of the present invention). The primary cable (1) is run from reel (42) into a first preparation station (43).

[In the following description, parts similar to those of previous embodiments will be noted by the same reference numeral]. At first preparation station (43) the outer sheath (5) is removed, followed by scoring and removal of the steel wire armour layer (13). The inner layers of insulation (11, 12) are removed to reveal insulated cable cores (10). The

cable is then moved to second preparation station (44). At this point the two extremities of the cable are pulled together to enable the insulated cable cores (10) to be opened up and separated. The insulating layer of the insulated cable cores that are to be connected (together with any layers of mica tape) are removed at the points where electrical connections are to be made. A ceramic insert (20) including brass socket inserts (21,22) is attached to the cores at the brass socket inserts. A layer of mica tape is then applied over the non-connected insulated core (10) and connected insulated cores. Earth strap (14) is connected to metal layers (13) and fixed firmly in place by steel clamping bands (15). The connector is then tested (continuity and insulating tests) in the conventional manner.

The cable is then moved onto moulding station (48) where the components of the connector fitting are enclosed within a-mould tool. The plastics material is injection moulded to form the connector fitting (2). The plastics material may be of identical or similar specification to that of the cable sheath. After moulding and setting, the connector fitting is removed from mould tool and inspected.

The connector fitting is then moved onto test station (49) for standard continuity, phase and performance testing.

The results are recorded. A dust cap is fitted over the terminals and the connector fitting packed for transportation.

In a further embodiment (not shown), ceramic insert is provided with insulated conducting tail connected to a C' crimp. For each connection, a C'crimp is connected to a conducting core. The layer of mica tape is then applied over the non-connected insulated core, connected insulated cores, C'crimps, and tails. The subsequent procedure (application of earth strap, testing, injection moulding the housing etc may then be as previously described).

A still further embodiment is shown in Figs. 10 and 11, with like parts to the first embodiment (those of Figs 1-8) shown by the same reference numeral as for the first embodiment. This embodiment includes coupling means which is a coupling nut (300). The coupling nut (300) is annular, with a series of lugs (303) located on the outer surface of the annulus, towards the bottom edge.

The housing of the female connector fitting (2) is made of injection moulded plastics material, as in the first

embodiment. The female connector fitting (2) housing includes a socket for a breakout plug (3). The socket for the breakout plug is surrounded by an annular groove (302) which is formed during the injection moulding step which formed the housing of connector fitting (2). The annular groove (302) has a further groove (301) located in the sidewall of annular groove (302) with greatest circumference.

Prior to connection of breakout (3) to connector (2), the coupling nut is located around cable (4) (i. e. cable 4 is passed through the annulus of coupling nut (303)-this may take place before breakout connector fitting (3) is formed on cable (4)). Breakout (3) is then connected to the socket of female connector fitting (2). The coupling nut (300) is pushed from a first position around cable (4) to a second position over the breakout (3) so that the bottom edge of coupling nut (300) becomes located within annular groove (302). As the nut (300) enters the groove (302), the lugs (303) become located in groove (301), thereby holding the bottom edge of coupling nut (300) in place in groove (302) on connector fitting (2). The inner annular surface of coupling nut (300) is dimensioned to tightly fit around breakout (3); the coupling nut (300) thus firmly holds the connection between breakout (3) and connector fitting (2) in place.

Thus, coupling nut 300 reduces the effect of vibration and thus the risk of disconnection of connector fitting (2) and breakout (3). The coupling nut (300) may be made of the same plastics material as the housing of the connector fitting, such as flame retardant plastics.

It will be appreciated that other systems for retaining the connection between connector fittings according to the invention may be used, for example the coupling nut may be held in place on the housing of connector (2) by a"bayonet- type"fitting, or the lugs could be replaced by a resiliently deformable ring which engages with groove (301). A still further embodiment of a connector compatible with coupling means or a coupling nut is shown in Figs 12 and 13, with like parts to those of embodiments of Figs 1-8 and Figs 10 and 11 shown with like numerals.

The embodiments of Figures 12 and 13 include a fuse (309) in breakout (3).