The present invention relates to an apparatus and method for preparing a cable, In particular, it relates to an apparatus and method to enable part of an existing data transmission cable, such as the outer sheath and part of the insulating dielectric, to be re-used once the conductor has been extracted, by inserting optical fibres therethrough.

Data, digital or coaxial transmission cables for transmitting data and digital signals into homes have been used for many years and are usually buried underground, often beneath pavements and the front gardens of the homes to which data is being supplied. There are various different cables commonly in use, but a typical cable generally comprises a conductor formed from a single wire or a bundle of strands made of copper or other electrically conductive material. The conductor is surrounded by a dielectric, which may be a relatively hard plastic or similar polymer material that insulates, protects and provides support for the conductor. A sheath made of PVC or similar material may extend over the dielectric and a copper or other metallic shield may line the sheath. This cable configuration provides good overall mechanical, weather, chemical and electrical protection.

Developments in technology, together with demand for better and faster data transfer, have recently necessitated the use of optical fibres for data transmission purposes, as optical fibre is capable of transmitting much larger quantities of data at high speed relative to traditional copper and other traditional metal conductors. Where optical fibre is required, the standard approach is to disconnect the existing cable and to lay an entirely new cable containing the optical fibre, with the old disconnected cable either being removed altogether or left in the ground. It will be appreciated that this approach necessitates the digging of a trench in order to lay the new cable, which is disruptive, time consuming and expensive.

In EP3055910B1, the present applicant has described an apparatus and method for removing a cable conductor from a cable sheath of a particular cable type in which the conductor is surrounded by an insulator formed by a relatively soft polymer filler material. With this type of cable, the applicant found that by supplying a voltage along the conductor, sufficient heat can be generated to reduce the viscosity of the soft polymer material to a point at which the friction between the conductor and the sheath is low enough to enable the conductor to be extracted from its sheath by pulling it from one end, thereby avoiding the need to pump fluid along the cable.

The above-described technique has proven to be effective in the removal of the conductor from certain cable types having a soft polymer dielectric insulator, displacing it from the sheath using the hydraulic action of the fluid. However, it has the disadvantage that it cannot be used in all cases when the cable has an insulating dielectric material formed from a harder polymer that is physically bonded into the shield or sheath, as the friction cannot be overcome by the increasing the pressure as the sheath bursts first, destroying the integrity of the cable. In this case an alternative method must be used.

As illustrated in Figure l, there is a particular cable type l in which the dielectric 4 is formed from a relatively hard tubular polymer. The conductor 6 extends along a tubular passage 7 within the dielectric 4 and is centralised within the passage 7 by a series of evenly spaced dividing walls or partitions 5 along its length (also see Figure 2). Each partition 5 has a central opening 8 through which the conductor 6 extends. As shown in Figure 1, the outer surface of the dielectric 4 may have ridges in the vicinity of each partition 5 which assists in binding the dielectric 4 to an outer sheath 2. A metallic, i.e. copper, shield 3 is disposed between the outer sheath 2 and the dielectric 4

To date, it has not been possible to extract the dielectric 4, with partitions 5, and the conductor 6 from cables 1 of the above-described type to enable the remaining part of the cable to be reused. More specifically, whilst it has been possible to extract the conductor 6 by applying a pulling force, the insertion of new optical fibres is impossible as the space is too limited and insertion is prevented by the partitions 5.

Therefore, the present invention seeks to provide a method and apparatus which substantially overcomes or alleviates problems identified above and so that a cable, of the type illustrated in Figure 1, can be reused with optical fibres.

According to the invention, there is provided apparatus for preparing a data- transmission cable that comprises a metallic conductor to enable the conductor to be replaced with optical fibre, the conductor being centralised within a tubular passage of a polymer dielectric by a series of spaced integrally formed partitions, wherein the apparatus comprises a cutter insertable into the tubular passage, the cutter including a cutting element to cut away the spaced partitions of the dielectric as the cutter travels along the tubular passage. The cutter may comprise a primary cutting element to cut through the partitions of the dielectric. The primary cutting element may be a drill bit or have a similar form to a drill bit. For example, the primary cutting element may comprise one or more helically formed cutting blades. The primary cutting element may be straight or tapered. For example, the primary cutting element may be conical.

In some embodiments, the primary cutting element may comprise leas puncturing elements.

The cutter may comprise a secondary cutting element to remove residual portions of the cut partitions as the cutter travels along the tubular passage.

The secondary cutting element can be located directly behind the primary cutting element such that the secondary cutting element cuts residual portions of the cut partitions after the dielectric has been cut by the primary cutting element.

The secondary cutting element may comprise at least one circular blade having an axis coaxial with an axis of the cable.

The secondary cutting element may alternatively comprise a plurality of parallel circular blades spaced from each other in a direction extending away from the primary cutting element. The diameter of each circular blade may increase with distance away from the primary cutting element.

In some embodiments, the secondary cutting element may comprise one or more helically formed cutting blades. The cutter can be a unitary component, i.e. the primary and secondary cutting elements can be integrally formed. Alternatively, the primary and secondary cutting elements are separate components which can be permanently or releasably attached to each other. If the primary and secondary cutting elements are releasably attached to each other, different primary and secondary cutting elements can be selectively used together.

The cutter may comprise a through bore to enable the cutter to be slideably received on the cable conductor. Alternatively, the cutter may comprise a clamp to enable the cutter to be attached to the conductor.

The apparatus may further comprise a drive transmission member coupled to the cutter and extending external to the cable.

The drive transmission member may be configured to rotate the cutter.

The drive transmission member may be configured for connection to a motor located external to the cable for rotating the drive transmission member.

The drive transmission member can be configured to push the cutter along the dielectric.

The cutter may comprise a guide member to guide the cutter through the dielectric if the conductor is removed beforehand. The guide member may comprise a rod with a tapering tip.

The drive transmission member may comprise a flexible rod. The drive transmission member may comprise a coiled element.

The apparatus can comprise a set of cutters. In this case, each cutter maybe of a different diameter. According to another aspect of the invention, there is provided a method of preparing a data-transmission cable comprising a metallic conductor to enable the conductor to be replaced with optical fibre, the conductor being centralised within a tubular passage of a polymer dielectric by a series of spaced partitions integrally formed with said dielectric, the method comprising selecting a cutter to fit within a tubular passage of the dielectric, inserting said cutter within the passage of the dielectric, and translating the cutter along the tubular passage so that cutting elements on the cutter cut through the spaced partitions of the dielectric.

The method may include clamping the cutter onto the conductor and pulling on the conductor to draw the cutter through the dielectric.

Alternatively, the method may comprise the cutter surrounding the conductor with it passing through the cutter and then driven along the conductor within the tubular passage of the dielectric. The method can include rotating the cutter as it is driven along the conductor.

In another embodiment the method comprises pulling the conductor to remove it from the dielectric prior to inserting the cutter into the tubular passage and driving the cutter along the tubular passage.

Embodiments of the invention will now be described, by way of example only, with reference to Figures 2 to 4 of the accompanying drawings, in which:

FIGURE 1 is a diagrammatic perspective view of a portion of a known cable having a dielectric with spaced partitions supporting the conductor along its length; FIGURE 2 is a cross-sectional side elevation of a section of cable according to Figure 1 which is to be re-used, and in which a cutter is shown attached to the cable conductor, according to a first embodiment;

FIGURE 3 is a cross-sectional side elevation of a section of cable according to Figure 1 which is to be re-used, and in which the cutter is rotatably mounted on the cable conductor according to a second embodiment; and

FIGURE 4 is a cross-sectional side elevation of a section of cable according to Figure 1 which is to be re-used, and in which the conductor has been extracted prior to insertion of a cutter into an end of the cable according to a third embodiment. With reference to Figure 2, a section of cable 1 according to Figure 1 is shown. A cutter 9 is so shaped as to self-centre on the conductor 6 and allow the cutter 5 to slide along the conductor 6 within the dielectric 4 cutting the partition 5s as it goes. The cutter 9 is clamped in position on the conductor 6 using mechanical fasteners 10 such as grub screws so that the cutter 9 and conductor 6 cannot move relative to each other as shown in Figure 2.

The cutter 9 has a leading or primary cutting element 11, and a trailing or secondary cutting element 12 on a support hub 13. The secondary cutting element 12 is located directly behind the primary cutting element 11. The cutter 5 may be integrally formed as a unitary component. Alternatively, the primary and secondary cutting elements 11, 12 may be made separately and then attached to each other.

The primary cutting element 11 can take the form of a drill bit and can be either cylindrical or conical, as shown in Figure 2. The primary cutting element 11 can have blades 14 that follow a helical path, but other blade configurations are also possible such as removeable specialist blade types like tungsten or cobalt that are best suited to the specific cable construction. This means the blades 14 could be mounted straight or angled for the optimum cut/speed.

The secondary cutting element 12 comprises a series of spaced parallel blades 15 mounted on the hub 13. Each blade 15 may be of the same diameter, although it is also envisaged that the blades 15 may also have different diameters. In particular, the blade 15 closest to the primary cutting element 11 may have a smaller diameter than the diameter of one or more blades 15 further away from the primary cutting element 11. The diameter of the blades 15 may increase gradually in size. The overall or maximum diameter of the cutter 9 is such that it is a sliding fit within the tubular passage 7 of the dielectric 4.

In the embodiment of Figure 1, the cutter 9 is drawn through the dielectric 4 by applying a force to the conductor 6 in the direction indicated by arrow marked ‘A’ in Figure 2. As the conductor 6 is extracted and the cutter 9 pulled through the dielectric 4, the primary cutting element 11 cuts through the dielectric partitions 5. In Figure 2, the cutter 9 is shown with the primary cutting element 11 in a position in which it has partially cut through a partition 5. The primary cutting element 11 may not cut the partitions 5 cleanly. Therefore, the secondary cutting element 12 removes any residual portions of the partitions 5 which have just been cut by the primary cutting element 11. As the secondary cutting element 12 has multiple blades 15, the inner surface of the dielectric should be relatively clean and smooth once both the primary and secondary cutting elements 11, 12 have fully passed a partition 5. The secondary cutting element 11 effectively acts as a reamer to clean the inside surface of the dielectric 4, especially in the vicinity of the cut partitions

5. In some embodiments, the cutter 9 may have only a single cutting element, i.e. the primary cutting element 11. In such embodiments, the secondary cutting element 12 is unnecessary and may be omitted. Figure 3 illustrates a similar embodiment, except that the cutter 9 is not clamped or otherwise attached to the conductor 6. Instead, the cutter 6 has a bore 7 which has a slightly larger diameter that the diameter of the conductor 6 so that the cutter 9 is free to slide along the conductor 6 and be guided by the conductor 6 along the dielectric 4. In this case, the conductor 6 remains in situ and the cutter 9 is driven along the conductor 6, in the direction of the arrow marked ‘A’, by an externally located motor (not shown) and a transmission element 17 that extends from, and is driven by, the motor. The cutter 9 may be rotationally driven by the motor to facilitate cutting of the partitions 5, but also so that the cutter 9 is propelled or translated along the dielectric 4 so that it cuts through the partitions 5 as it goes. The transmission element 17 maybe a sectional solid, flexible steel rods up to 2m, or longer, in length with bolted connecting units that can be linked together for the desired length. Alternatively, the transmission element 17 can be a flexible, hollow, and possibly coiled, drive lines up to 30m in length that can be linked by adding additional sections to the required length. In the embodiment of Figure 3, only a primary cutting element 18 ia illustrated. Whilst, the primary cutting element 18 could be of a similar form to that described with reference to Figure 2, it can also take the form of a cylindrical shaft 19 with helical or angled cutting blades 20. A helical channel is formed between the blades 20 by the shaft 19, along which the cut material travels so that it is fed out behind the cutter 9. . An additional secondary cutting element could be added, similar to that shown in

Figure 2, depending on the smoothness of finish left by cutter 9. The primary cutting element 18 may have forward facing puncturing blades 21 to initially cut through the partions 5. The primary cutting element 18 maybe a broaching or similar type of drill. With reference to the embodiment of Figure 4, the conductor 6 is removed from the dielectric 4 prior to insertion of the cutter 9. This can be achieved by applying a pulling force to the conductor 6 via a winch. Once the conductor 6 has been removed, the cutter 9 is inserted into the, now vacant space within the dielectric 4, and using a guiding rod 22 at the front of the cutter 9 the cutter 9 self-centres within the dielectric 4. The cutter 9 is then driven along the dielectric 4, in the same way as described with reference to Figure 3. The guiding rod can have a pointed tip 23 that passes into the openings 8 in the partitons 5, to further improve the centering of the cutter 9 within the dielectric 4. er 9 can otherwise have a similar construction to the embodiment of Figure 2 or 3.

It will be appreciated that the cutter 9 needs to fit snugly within the dielectric 4 of the cable 1, so that it will remove and clear away the partitions 5. At the same time, the cutter 9 must be able slide within the tubular passage 7 of the dielectric 4. As cables 1 of different diameters exist, it is envisaged that the cutter 9 maybe provided as part of a set of cutters 9, each of which has a different diameter, so that an appropriate cutter 9 may be selected according to the diameter of the cable 1 which is being worked on.

The cutter 9 can be connected to the drive mechanism by a hexagonal shaft 24, 9 and connector 25 that slides over the shaft 24. The hexagonal shaft 24 is fixed in manufacture to the support hub 13 which in-turn is fixed to the remainder of the cutter 9 via a threaded shaft or welding.

Many modification and variations of the invention falling within the terms of the following claims will be apparent to those skilled in the art and the foregoing description should be regarded as a description of the preferred embodiments of the invention only.