Abstract:
Described is a device ( 410 ) for use in removing a conveyance member from a material. The device ( 410 ) includes a displacement element ( 412 ) for being placed at least partly around a conveyance member and for displacing material as the device is advanced along a conveyance member. The device ( 410 ) also includes a driven component for receiving a driving force for driving the device through material. The device can include a coupling element ( 418 ) for coupling the device to a shaft and a material loosener ( 414 ) including a drilling element. The material loosener can be operable to loosen material ahead of the displacement element as the device is advanced along a conveyance member. The drilling element can be coupled to a first wheel ( 436 ) and the coupling element can include a second wheel ( 434 ) cooperating with the first wheel to transfer rotational movement of a shaft to the drilling element.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to methods for removing conveyance members and devices for use in removing conveyance members. 
       BACKGROUND 
       [0002]    In the United Kingdom and around the world, significant lengths of electrical cable are underground, especially in built-up areas where it is difficult or undesirable to suspend cables from pylons. 
         [0003]    In many cases, since these cables were laid, further building has been done above the cables. 
         [0004]    At present, in order to remove such cables, it is generally necessary to dig them out. However, this is often extremely difficult, for example where extensive building has been carried out above them and/or where the owner of the land does not wish his land to be disturbed. For example, if the cables pass under farmland, it is often necessary initially to remove and store the topsoil. Then it is necessary to dig out the cable. Once the cable has been dug out, it is necessary to import earth to fill the void left by the removed cable, before replacing the topsoil. Throughout this procedure, the farmer is unable to use his land. 
         [0005]    As a result of these difficulties, it is often easier to leave redundant cables where they are. 
         [0006]    However, many underground electricity cables include oil under pressure to prevent the high-voltage conductive core becoming inadvertently grounded. This can be an environmental risk since the oil can be environmentally damaging if it leaks. Furthermore, the risk of such leaks is higher with redundant cables since they are generally older and potentially degraded in comparison with newer cables. 
         [0007]    One way in which this risk is addressed is by soldering caps onto the ends of sections of redundant cables to prevent leakage of oil. However, this is a costly process and needs to be carried out by an expert jointer. 
         [0008]    GB 2466897, GB2431424 and GB2426534 disclose overdrilling devices. DE19802691 and DE19504484 disclose equipment for removing buried cables. Energy Networks Association NIA Project Registration and PEA Document of February 2014 provides details of a project for cable extraction. 
       SUMMARY OF THE INVENTION 
       [0009]    Aspects of the present invention seek to provide an improved conveyance member removal method and device. 
         [0010]    According to an aspect of the invention, there is provided a device for use in removing a conveyance member from a material, including:
       a coupling element for coupling the device to a shaft;   a displacement element for being placed at least partly around a conveyance member and for displacing material as the device is advanced along a conveyance member;   a driven component for receiving a driving force for driving the device through material; and   a material loosener operable to loosen material ahead of the displacement element as the device is advanced along a conveyance member;   wherein the material loosener includes a drilling element coupled to a first wheel and the coupling element includes a second wheel cooperating with the first wheel to transfer rotational movement of a shaft to the drilling element.       
 
         [0016]    A difficulty faced by many prior art drilling devices is how to provide a rotational drilling movement to a drilling element. This difficulty can be exacerbated by the fact that the axis of the drilling element is generally parallel to but laterally displaced from the axis of a shaft coupling the device to a driving unit. 
         [0017]    Preferred embodiments of the invention are able to laterally transfer rotational movement from a shaft to a drilling element using a dual wheel system, thereby effectively enabling a driving unit to remotely control and drive rotation of the drilling element. 
         [0018]    According to an aspect of the invention, there is provided a device for use in removing a conveyance member from a material, including:
       a displacement element for being placed at least partly around a conveyance member and for displacing material as the device is advanced along a conveyance member; and   a material loosener operable to loosen material ahead of the displacement element as the device is advanced along a conveyance member.       
 
         [0021]    According to an aspect of the invention, there is provided a device for use in removing a conveyance member from a material, including:
       a displacement element for being placed at least partly around a conveyance member and for displacing material as the device is advanced along a conveyance member; and   a driven component for receiving a driving force for driving the device through material.       
 
         [0024]    Preferably the device includes a material loosener operable to loosen material ahead of the displacement element as the device is advanced along a conveyance member. 
         [0025]    The term ‘ahead’ is intended to mean ahead in a direction along which the device is designed to be advanced and the terms ‘forwards’, ‘front’ and ‘back’ are similarly intended to be with respect to the direction in which the device is designed to be advanced. 
         [0026]    The term ‘conveyance member’ is intended to refer to for example elongate and/or tubular members or lines for conveying substances or signals, such as water, gas, electricity, or fibre optic signals, in particular underground. These can be for example wires, ducts or pipes, for example metal and/or plastic pipes. Preferably, the conveyance member is a cable, preferably an electricity cable. Nevertheless, although the term ‘cable’ is used throughout this description, embodiments can be used with other conveyance members or conveyance lines. 
         [0027]    Preferred embodiments of the invention are able to loosen a cable in material, such as in the ground, sufficiently that it can be pulled or pushed in a longitudinal direction to slide out and be removed from the material. The device can be said to form a void around the cable or debond the cable from the material. This can mean that it is only necessary to excavate a small section of the cable, either an end or a section in which the cable can be cut to create an end, and the cable can be slid out from under the ground. This means that it is not necessary to dig a trench as long as the section of cable it is desired to remove, thereby saving significant time and expense. 
         [0028]    Some previous attempts to remove cables in a longitudinal manner have resulted in the cable snapping, meaning that in order to recover the entire cable, it has been necessary to dig a long trench in the conventional manner. Furthermore, a snapping cable can lead to environmental risks if there is still oil in the cable. However, by providing a device which can travel along the cable and loosen material around the cable, the risk of the friction being greater than a breaking strength of the cable is minimised. In addition, the displacement element can displace the loose material away from the cable, compacting it outside the circumference of the displacement element. This can create a void between the material and the cable, further decreasing the resistance to the removal of the cable. 
         [0029]    Preferably, the displacement element is configured for substantially surrounding a conveyance member. Preferably, the displacement element or at least an inner edge thereof is substantially annular, and is configured to substantially surround a cable. Preferably, the displacement element is substantially circular in cross section. In other words, the displacement element can include a passageway therethrough for receiving a cable, the passageway preferably being substantially circular in cross-section. 
         [0030]    The device can be considered to have a longitudinal axis which coincides with a longitudinal axis of a cable when the device is placed on a cable. Preferably, the material loosener is arranged substantially evenly around the longitudinal axis to provide substantially even loosening of material around a cable. The material loosener can be provided in, on, or as part of the displacement element. 
         [0031]    In some embodiments, the material loosener is operable to create a suspension, hydrate and/or break up the material. For example, the material loosener can include a spray for spraying fluid ahead of the displacement element. This can make the material create a suspension and thereby loosen the material, allowing it to be displaced by the displacement element. The fluid can be a liquid, advantageously a lubricating liquid. The most preferred example of liquid to be used is bentonite solution. Bentonite solution is known in the drilling industry. It is a natural clay mixed with water which can cause earth and rock to float. This is advantageous since it can stabilise the void created by the displacement element, cool the device, and lubricate the displacement element. It is possible to use other fluids. For example, emulsion slurry can be used. However, this is not preferred since it is not biodegradable. 
         [0032]    The material loosener can include a fluid distribution network including:
       an inlet for receiving fluid from a fluid source; and   a plurality of forward-facing outlets for emitting fluid into material ahead of the displacement element, the plurality of outlets being coupled to the inlet by one or more conduits.       
 
         [0035]    The inlet can be coupled to a fluid source via a feed conduit. 
         [0036]    In some embodiments, the fluid distribution network includes a first distribution conduit for transporting fluid in a first angular direction around the longitudinal axis and a second fluid distribution conduit for transporting fluid in a second angular direction around the longitudinal axis opposite to the first angular direction. Each of the first and second distribution conduits can include a plurality of evenly spaced outlets. The first and second distribution conduits can be on or in the displacement element. The fluid distribution network can be housed within a housing for protection with openings for the outlets and inlet to emit and receive fluid, respectively. Part or all of the housing can be provided by the displacement element. The outlets can be configured to emit fluid through openings in the displacement element. 
         [0037]    The material loosener can include a drilling element. 
         [0038]    The drilling element can include any features to assist drilling, such as teeth. The drilling element is preferably operable to perform complete and continuous rotation, in other words it can preferably rotate continuously in the same angular direction through at least 360°. 
         [0039]    In some embodiments, the drilling element is provided at or on the front of the displacement element. However, in other embodiments, the drilling element can be an annular element distinct from the displacement element. If the drilling element is a distinct annular element, it preferably has a greater diameter than the displacement element since the displacement element is designed to push out loosened material. 
         [0040]    Preferably, the device, preferably the driven element, includes a coupling element for coupling the device to a shaft. A shaft coupled to the coupling element can apply a force to the driven element to drive the device through the material. The coupling element can include a longitudinal force transfer element to transfer a longitudinal force in the shaft into a longitudinal advancing force on the displacement element to advance the displacement element through material. 
         [0041]    The coupling element can be configured to couple a shaft to the device to transfer longitudinal forces in the shaft to the displacement element, and rotational forces in the shaft to the material loosener. This can allow operation of the shaft to advance the device in a rotating manner, causing a drilling or boring action. 
         [0042]    In some embodiments, the material loosener can be fixedly coupled to or integral with the displacement element so that the material loosener and the displacement element rotate together or as a single unit and the device advances as a single unit. In such embodiments, the device can include a stator with respect to which the material loosener and displacement element can rotate. 
         [0043]    The material loosener can include a drilling element coupled to a first wheel, and the coupling element can include a second wheel cooperating with the first wheel to transfer rotational movement of a shaft to the drilling element. If the displacement element and material loosener are configured to rotate together, the first wheel can be provided in the displacement element. 
         [0044]    A difficulty faced by many prior art drilling devices is how to provide a rotational drilling movement to a drilling element. This difficulty can be exacerbated by the fact that the axis of the drilling element is generally parallel to but laterally displaced from the axis of a shaft coupling the device to a driving unit. 
         [0045]    Preferred embodiments of the invention are able to laterally transfer rotational movement from a shaft to a drilling element using a dual wheel system, thereby effectively enabling a driving unit to remotely control and drive rotation of the drilling element. 
         [0046]    The coupling element may include one or more thrust bearing housings through which a shaft can rotatably pass and which can transfer longitudinal forces on the shaft into longitudinal forces on the device. The thrust bearing housings can be configured to transfer longitudinal forces to the stator, the stator being configured to transfer longitudinal forces to both of the material loosener and the displacement element. 
         [0047]    Preferably, the first wheel is a sprocket and the second wheel includes a perforated track, preferably a chain of roller bearings. This advantageously allows loose material such as mud to be pushed out of the region of engagement of the first and second wheels by the sprockets of the first wheel pushing it through the perforations of the second wheel. This prevents the first and second wheels from becoming clogged which would otherwise be a risk since they are designed to operate surrounded by often solid material, for example underground. 
         [0048]    Preferably, the axes of the first and second wheels are both substantially parallel, for example are both substantially longitudinal, so that the planes of rotation of the shaft, and the first and second wheels are all substantially parallel, providing an intuitive transfer of force from a shaft to the device. 
         [0049]    Preferably, the axis of the first wheel is outside a circumference of the second wheel. 
         [0050]    The material loosener can include a drilling element coupled to a plurality of first wheels, and the coupling element can include a plurality of second wheels, each second wheel cooperating with a respective first wheel to transfer rotational movement of a shaft to the drilling element. If the displacement element and material loosener are configured to rotate together, the plurality of first wheels can be provided in the displacement element. Each of the first and second wheels can be as described above. Having a plurality of first and second wheels means that the components are less likely to snap and more power can be transferred to the drilling element. 
         [0051]    In some embodiments, the material loosener can be fixedly coupled to or integral with the displacement element so that the entire device rotates and advances as a single unit. Where a drilling function is provided in these embodiments, it can be provided by oscillation of the entire device. 
         [0052]    According to an aspect of the invention, there is provided a system for removing a cable from a material, including:
       a device as described above; and   a driver for applying a forward force to the device.       
 
         [0055]    Preferably, the driver includes a shaft coupled to the driven element of the device. 
         [0056]    Preferably the driver includes a driving or drilling unit operable to apply a longitudinal force to the shaft. 
         [0057]    Preferably the driver is operable to provide a rotating force to the device, preferably to the shaft, preferably to the material loosener. 
         [0058]    In some embodiments, the driver is operable to supply a fluid, preferably under pressure, to the spray of the device. The fluid can be supplied for example using the shaft as a feed conduit. 
         [0059]    According to an aspect of the invention, there is provided a device for securing a cable mover to a cable, including:
       an annular clamp for being received around a cable, an internal diameter of a first end of the annular clamp being greater than an external diameter of a cable to be moved;   a coupling element for coupling the annular clamp to a cable mover; and   at least one block for being pressed between the clamp and a cable;   wherein the at least one block and/or the annular clamp includes a taper whereby a force on the clamp causes the clamp to press the block against the cable.       
 
         [0064]    Preferably, the annular clamp has a taper and an internal diameter of a second end of the clamp is less than the internal diameter of the first end of the clamp. 
         [0065]    Preferably, the block is a wedge. 
         [0066]    Preferably, a surface, preferably a tapered surface, of the wedge includes a gripping finish, for example a roughened finish, to increase friction with the annular clamp. 
         [0067]    According to an aspect of the invention, there is provided a method of moving a cable including:
       placing an annular clamp over a cable, wherein an internal diameter of a first end of the annular clamp is greater than an external diameter of a cable to be moved;   placing at least one block between the clamp and the cable; and   applying a force to the clamp in a direction in which the first end of the clamp is facing, to move the cable;   wherein the at least one block and/or the annular clamp includes a taper whereby the force on the clamp causes the clamp to press the block against the cable.       
 
         [0072]    Preferably, the force on the cable is longitudinal. 
         [0073]    Preferably, the or each block is a wedge and the or each block is placed between the clamp and the cable with a thicker end of a taper of the wedge facing the direction in which the force is applied. 
         [0074]    According to an aspect of the invention, there is provided a method of removing a cable from a material, the method including:
       placing a device as described above on the cable at or near a first end thereof;   advancing the device towards a second end of the cable to loosen material adjacent to the cable between the first and second ends; and   applying a substantially longitudinal force to the cable to draw the cable out of the material.       
 
         [0078]    According to an aspect of the invention, there is provided a method of removing a cable from a material, the method including:
       loosening or displacing material adjacent to the cable; and   applying a substantially longitudinal force to the cable to draw the cable out of the material.       
 
         [0081]    Advancing the device preferably includes rotating or oscillating a material loosener of the device, for example to enable any material adjacent to the cable to be loosened. 
         [0082]    Advancing the device can include applying fluid under pressure to the spray of the device, for example to the fluid distribution network, to cause the device to spray and thereby loosen material ahead of it. 
         [0083]    Preferably, advancing the device includes advancing a shaft coupled to a driven element of the device. 
         [0084]    Applying fluid to the device can include applying fluid via the shaft. 
         [0085]    The method can include excavating material around the first end to allow the device to be placed onto the cable and to allow a cable mover to be attached to the cable to apply the longitudinal force. 
         [0086]    The method can include excavating material around the second end. 
         [0087]    The method can include excavating material around a first and/or a second section of cable and cutting the cable in that or those section(s) to form the first and/or second end. 
         [0088]    Preferably, if a cable is cut to form an end, the method also includes capping the cable, preferably using the method for capping a cable described below. 
         [0089]    Preferably, after the cable is removed, the method includes pumping a filling material into a void left by the cable. 
         [0090]    In other embodiments, the method can include inserting a duct into a void left by the cable to keep the void open for possible reuse. This can be done by attaching a duct to the second end of the cable before the cable is withdrawn so that the cable draws the duct into the void as it is being withdrawn. 
         [0091]    According to an aspect of the invention, there is provided a method of capping a cable, including:
       placing a cap over an end of a cable; and   coupling the cap to the cable by a mechanical coupling only.       
 
         [0094]    The cap is preferably secured to the cable by an interference fit. 
         [0095]    The preferred method of securing a cap to a cable avoids the need to have the cap soldered to the cable. This avoids the time and expense of having an expert jointer soldering the cable. 
         [0096]    Although the preferred method of capping a cable may allow some moisture into the cable, this is not a problem where the cable is not intended to be reused since the reason for excluding moisture is that it may provide a path to ground for electricity in a live wire. The inventors have discovered that a cap coupled by purely mechanical means is sufficient to prevent egress of oil, which is all that is necessary in redundant oil filled cables. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0097]    Preferred embodiments of the invention are described below, by way of example only, with reference to the accompanying drawings, in which: 
           [0098]      FIG. 1  is a schematic diagram of a device according to an embodiment of the invention; 
           [0099]      FIG. 1A  is a front view of the device of  FIG. 1 ; 
           [0100]      FIG. 2  is a perspective view of a device according to an embodiment of the invention; 
           [0101]      FIG. 2A  is a perspective view of a wedge for use in the device of  FIG. 2 ; 
           [0102]      FIG. 2B  is a schematic cross section of the device of  FIG. 2 ; 
           [0103]      FIG. 3A  is a schematic cross section of an area of ground in which a cable is located; 
           [0104]      FIGS. 3B to 3H  are schematic cross sections of the area or a part of the area of ground of  FIG. 3A  during operation of a method according to an embodiment of the invention; 
           [0105]      FIG. 4  is a schematic perspective view of a device according to an embodiment of the invention; 
           [0106]      FIG. 5  is a schematic side cut-away view of a device according to an embodiment of the invention; 
           [0107]      FIG. 5A  is a schematic front view of a rotational force transfer element for the device of  FIG. 5 ; 
           [0108]      FIG. 5B  is a front view of a longitudinal force transferring element; 
           [0109]      FIG. 6  is a schematic side cut-away view of a device according to an embodiment of the invention; 
           [0110]      FIG. 7  is a schematic side view of a device according to another embodiment of the invention; and 
           [0111]      FIG. 8  shows a cross section of a cap for an end of a cable in an embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0112]    As described above, electrical cables are often buried in the ground. There is a variety of materials which can be around the cable underground, such as earth, soil, sand, cement, cement bound sand (CBS). Embodiments described below are generally described for a cable surrounded by soil. However, the description is equally applicable to a cable surrounded by other materials. 
         [0113]    Particularly preferred embodiments include a drilling element and are able to address prior difficulties in how to provide a rotational drilling movement to a drilling element. However, for ease of description, these embodiments are described later. 
         [0114]    As can be seen from  FIG. 1 , a device  10  according to an embodiment of the invention includes a displacement element  12  and a material loosener  14 . 
         [0115]    The displacement element is an annular element arranged so that as it is advanced along a cable  16  it displaces soil that was adjacent to the cable  16 , compacting the soil outside the outer perimeter of the displacement element  12 . 
         [0116]    The displacement element  12  and therefore the device  10  can be considered to have a longitudinal axis which when the device is placed on a cable corresponds to a longitudinal axis of the cable. 
         [0117]    As can be seen from  FIG. 1 , a cross section of the displacement element  12  when viewed along the longitudinal axis is substantially circular in order to correspond with the cable  16 . In particular, a cross-section of an inner passageway is substantially circular to receive the cable and a cross-section of the outer perimeter is substantially circular for tunnelling efficiency. 
         [0118]    A diameter of the displacement element is slightly greater than the diameter of the cable  16  on which the device is designed to be used. In the embodiment of  FIG. 1 , the outer diameter of the displacement element is about 160 mm. However, different cables have different diameters, and it is accordingly possible to provide a plurality of devices as described herein, each with a displacement element with a diameter or at least an inner diameter of a different size, designed to fit different cables. 
         [0119]    The device  10  includes a coupling element  18  for coupling the device to a shaft  20 . The coupling element  18  can be a tube for securely receiving a shaft, for example by an interference fit. The shaft is thereby able to provide longitudinal and rotational force to the device  10 . As described below, the shaft is also able to provide fluid for the material loosener  14 . 
         [0120]    The material loosener  14  in this embodiment includes a fluid distribution network providing a spray. The fluid distribution network includes an inlet  22  in the coupling element for coupling to and receiving fluid from the shaft  22 , the shaft acting as a feed conduit. 
         [0121]    The inlet  22  includes a conduit inside the coupling element  18  which leads fluid from the shaft to a fluid junction  24 . The fluid junction  24  is arranged to divide fluid and includes first, second and third output conduits. The first conduit  26  passes inside and around the displacement element  12  in a clockwise direction adjacent to a front edge of the displacement element  12 . The first conduit leads fluid around the displacement element  12  in a clockwise direction. Evenly spaced along the first conduit are provided apertures  30  in the conduit and displacement element  12  through which fluid in the first conduit is emitted forwards. 
         [0122]    The second conduit corresponds to the first conduit except that it passes around the displacement element  12  in an anti-clockwise direction. 
         [0123]    The first and second conduits terminate adjacent to each other at a point substantially diametrically opposite the junction  24 . However, they are not in fluid communication at this point. 
         [0124]    The third conduit  28  leads longitudinally forwards from the junction  24  and terminates in a further aperture  30  in line with the shaft  20 . 
         [0125]    However, in other embodiments, different configurations of the fluid distribution network are possible. For example, it is not always necessary to have the third conduit  28 . Furthermore, it is possible to have a single conduit which passes all the way around the displacement element  12  from the junction  24  rather than having two conduits passing in opposing directions. It is also possible for each aperture to have its own dedicated conduit leading from the junction  24 . Additionally, it is not necessary to have the apertures  30  evenly spaced. However, having two opposing conduits has been found to be an efficient way to provide a symmetrical pressure of fluid emission from a single feed conduit. 
         [0126]      FIG. 2  shows a device  100  for securing a cable puller to a cable  16 . The device  100  includes an annular clamp  102  which can be received on a cable  16 . 
         [0127]    As can be seen more clearly in  FIG. 2B , the annular clamp includes a first internal diameter  104  at a first end  106  and a second internal diameter  108  at a second end  110 . The internal diameter is the diameter of the cross section viewed along a longitudinal direction inside the clamp, in other words the space through which a cable can pass. 
         [0128]    The first internal diameter  104  is greater than the second internal diameter  108  and the internal surface of the annular clamp tapers from the first end to the second end. 
         [0129]    The device includes a plurality of removable wedges  112 . The wedges are blocks with a tapering surface  114 . The taper of the tapering surface  114  corresponds to the taper of the annular clamp so that the wedges  112  can fit between the internal surface of the annular clamp and the cable while being in substantially full contact with both. 
         [0130]    The tapered surface  114  of the wedges  112  is provided with a roughened gripping finish to increase friction with the clamp. 
         [0131]    As can be seen from  FIG. 2 , in this embodiment there are four wedges  112  for being placed between the clamp and a cable. However, there can be more or fewer than four in other embodiments. 
         [0132]    The device  100  includes a plurality of coupling elements  116  attached to the clamp for coupling to a cable puller. As shown, these can be in the form of loops. They are preferably located symmetrically about the annular clamp in order to provide a substantially longitudinal force to the device  100 . In the embodiment of  FIG. 2 , the coupling elements  116  are located in a line with the clamp, with one either side of the clamp. 
         [0133]    The devices  10  and  100  described above can be used in a method of removing a cable as follows. 
         [0134]    As shown in  FIG. 3A , an area of ground is located in which a cable  16  passes under the ground. 
         [0135]    As shown in  FIG. 3B , a first excavation is made to excavate a launch site  200  exposing a first section of the cable  16 , and a second excavation is made to excavate a receive site  220  exposing a second section of the cable  16 . 
         [0136]    As shown in  FIG. 3C , the first and second sections of cable are cut to create a section of cable to be removed with a first end  222  and a second end  224 . 
         [0137]    As shown in  FIG. 3D , each of the exposed ends of cable have a cap secured to them by purely mechanical means. The caps  226  are generally available for sale as caps for gas or water pipes. Previously, it has been considered necessary to solder copper caps to the ends of electric cables, especially oil filled electric cables, to keep out moisture. However, this is expensive. While soldering copper caps can still be done if the cable is to be reused, for redundant cables, it is advantageous to secure a cap by purely mechanical means. A cross section of the cap  226  on the end of the cable is shown in more detail in  FIG. 8 . As can be seen from  FIG. 8 , a cap end  225  is an open-ended cylinder configured to fit over the end of the cable. The cap end  225  includes a rubber annular wedge  227  which tapers from a first larger inner diameter nearer the open end of the cap end to a second smaller inner diameter nearer the closed end of the cap end. As a cable is pushed into the wedge, an interference fit is formed between the wedge and the cable to hold the cable. 
         [0138]    The next stage is to loosen material adjacent to the cable  16  for the section that is to be removed. 
         [0139]    A first end of a shaft  20  is coupled to a device  10  as described above. A second end of the shaft  20  is coupled to a horizontal directional drilling unit  230 . Horizontal directional drilling units  230  are well known in the drilling sector. 
         [0140]    The device  10  is placed over the first end  222  of the cable  16  so that the cable passes through the annulus of the displacement element  12 . 
         [0141]    The drilling unit  230  is operated to supply liquid, in this example in the form of bentonite solution, through the shaft  20  under pressure. 
         [0142]    The liquid enters the inlet  18  of the device  10  and is distributed by the junction  24  to the first, second and third conduits. Owing to the pressure of the liquid, the liquid sprays out of the apertures  30  in a forward direction with respect to the device  10 . 
         [0143]    The horizontal directional drilling unit  230  is operated to apply a longitudinal force to the shaft  20  and thereby advances the device. The drilling unit  230  can also apply a rotational force to the shaft to cause the device  10  to oscillate as it is advanced. While this can advantageously make the loosening of the material more efficient and symmetric, it is not always necessary. 
         [0144]    As the device  10  is advanced into the soil, the liquid is being sprayed in front of the device, causing the soil to become a loose suspension. As the displacement element is advanced into this loose suspension of soil, it easily pushes it away from the cable  16  and compacts it outside the perimeter of the displacement element  12 . This creates a void immediately around the cable  16 . 
         [0145]    Often, the shaft will be made up of a plurality of shaft sections. In this case, the drilling unit  230  is operable to couple the shaft sections together to lengthen the shaft as it is being advanced, in a manner known in the art. 
         [0146]    Once the device  10  has emerged in the receive pit  220 , the device  10  is decoupled from the shaft  20  and removed. However, the shaft is left in position. 
         [0147]    The shaft  20  is then decoupled from the drilling unit  230  and a device  100  as described above is attached to the cable  16  near the first end  222  as shown in  FIG. 3F . 
         [0148]    The device  100  is placed over the first end of the cable and advanced over the cable so that the first end  106  of the device  100  faces the direction in which the cable is to be withdrawn. 
         [0149]    The wedges are then placed between the internal surface of the clamp  102  and the cable  16 , and the coupling elements  116  are coupled to the drilling unit  230 , which now serves as a cable remover, for example by cables  240 . 
         [0150]    The cable remover  230  is then operated to apply a longitudinal force to the device  100  in the direction from the second end  110  of the device  100  towards the first end  106 . 
         [0151]    The grip of the device  100  on the cable  16  causes this longitudinal force to be transferred to the cable and to draw the cable out of the soil towards the cable remover  230 . 
         [0152]    As the clamp  102  is pulled by the cable remover, the cooperation of the tapers of the wedges and the internal surface of the clamp causes the clamp to press the wedges tighter against the cable, thereby increasing the grip of the device on the cable. This minimises the ability of the clamp to slide along the cable. 
         [0153]    Owing to the looseness of the soil where the device  10  has traveled along the cable and/or to the void created by the device, the cable  16  slides out of the soil in response to being pulled by the device  100 . 
         [0154]    In some embodiments, it is possible to attach a duct to the second end of the cable  16  so that as the cable is removed, it draws the duct in to replace the cable, thereby keeping the void open for possible future reuse. 
         [0155]    However, in the depicted embodiment, once the cable has been removed, the shaft  20  is recoupled to the drilling unit  230  and the drilling unit is operated to retract the shaft  20  while spraying a grout  250  into the void left by the cable as shown in  FIG. 3G . 
         [0156]    After about 6 hours, the grout will have set, thereby securely filling the void as shown in  FIG. 3H . 
         [0157]    The method described herein can provide an inexpensive and rapid way to remove underground cables, with minimal disruption to the surface. Preferred methods can remove a 150 m section of cable, which would normally take about 2 weeks to remove, in about 90 minutes. 
         [0158]    In addition to the above, various modifications can be made and different embodiments are possible. 
         [0159]    Although the displacement element  12  is generally described as being annular, it is not necessary in all embodiments for the displacement element  12  to be continuous around the cable. However, it is preferred that the displacement element  12  is configured to displace material from the entire periphery of the cable. It is also not necessary that the displacement element  12  is circular in cross section when viewed along the longitudinal axis. However, it is preferred that the cross section when viewed along the longitudinal axis substantially corresponds to the cross section of the cable  16  when viewed along the longitudinal axis as this tends to maximise the material displacement efficiency of the displacement element. 
         [0160]      FIG. 4  shows another embodiment of a device for use in removing a cable corresponding in many respects to the device  10  of  FIG. 1 . However, in the device of  FIG. 4 , the aperture  30  at the end of the third conduit is provided in a nozzle  310 . 
         [0161]      FIG. 5  is a schematic side view of another embodiment of a device  410  for use in removing a cable. 
         [0162]    The device  410  includes a displacement element  412  and a material loosener  414 . 
         [0163]    As for the embodiment of  FIG. 1 , the displacement element  412  is an annular element arranged so that as it is advanced along a cable  16  it displaces soil that was adjacent to the cable  16 , compacting the soil outside the outer perimeter of the displacement element  412 . 
         [0164]    As for the embodiment of  FIG. 1 , a cross section of the displacement element  412  when viewed along the longitudinal axis is substantially circular in order to correspond with the cable  16  and a diameter of the displacement element is slightly greater than the diameter of the cable  16  on which the device is designed to be used. 
         [0165]    As for the embodiment of  FIG. 1 , the device  410  includes a coupling element  418  for coupling the device to a shaft  20 . The shaft is thereby able to provide longitudinal and rotational force to the device  10 . 
         [0166]    The material loosener  414  in this embodiment includes a drilling element  415 . The drilling element  415  in this embodiment is a plurality of teeth projecting from a front of the displacement element  412 . The teeth can be integral with or fixedly coupled to the displacement element. 
         [0167]    In this embodiment, the displacement element  412  is rotatable through 360° about the longitudinal axis. Rotation of the displacement element  412  causes a corresponding rotation of the drilling element  415 . 
         [0168]    In this embodiment, there is provided a stator  417  with respect to which the displacement element  412  and drilling element  415  rotate. The stator  417  is annular, preferably cylindrical, and is configured for a cable to pass through it. 
         [0169]    The stator  417  has a smaller diameter than the displacement element  412  and is partly inside the displacement element. However, in other embodiments, the stator  417  can have a larger diameter than the displacement element. 
         [0170]    The displacement element  412  is rotatably coupled to the stator  417 , but in a manner which allows longitudinal force to be transferred from the stator to the displacement element  412 . In the depicted embodiment, this is by providing an internal circumference of the displacement element with first and second circumferential channels  424 , and providing the stator with corresponding projections  426  on its outer surface, in this embodiment in the form of brass wear rings, which allow the channels to rotate but not to move longitudinally with respect to the projections. A cross sectional view of the stator showing the projections, and a cable within the stator can be seen in  FIG. 5B . 
         [0171]    However, there are various other means known to one skilled in the art for coupling a rotator to a stator so that rotational relative movement is permitted but longitudinal relative movement is inhibited. For example the channels and projections can be the other way around, with the channels on the rotating displacement element and the projections on the stator, and there can be more or fewer than two channels. 
         [0172]    In this embodiment, the coupling element  418  is rotatable with respect to the stator  417 . The coupling element  418  passes through a thrust box  428  which is fixedly coupled to the stator  417  and which allows the coupling element  418  to rotate with respect to it, but restricts longitudinal movement, thereby transferring longitudinal forces from the coupling element to the stator  417 . As can be seen from  FIG. 5 , in this embodiment this is achieved by providing ridges on the coupling element  418  which abut thrust bearings  432  when they try to move longitudinally. The thrust bearings are coupled to the thrust box to transfer longitudinal forces thereto. 
         [0173]    However, there are various other means known to one skilled in the art for coupling a rotating shaft to a stator so that rotation of the rotating shaft is permitted but longitudinal relative movement is inhibited. 
         [0174]    A sprocket  434  is coupled to the coupling element  418 . The sprocket is arranged to rotate in a plane perpendicular to the longitudinal axis. The sprocket is arranged to cooperate with a perforated track  436  on or in the displacement element  412 . The perforated track is circumferential on or in the displacement element and the axis of the sprocket is outside the circumference of the displacement element. The cooperation of the sprocket and track is shown more clearly in  FIG. 5A . 
         [0175]    As shown in  FIG. 5A , the teeth of the sprocket are configured to press into perforations  438  in the track, thereby forcing soil or other material out to prevent the system becoming clogged as it is drilling. The perforated track in this embodiment is provided by a chain of roller bearing needles. However, other forms of chain or perforated track can be used in other embodiments. Alternatively, gears can be used, although these are not preferred since they are at risk of becoming clogged. 
         [0176]    Where the perforated track is provided on the displacement element, the displacement element is preferably provided with holes corresponding to and aligning with the perforations in the track to allow soil or other material to be pushed through the displacement element by the teeth of the sprocket. Where the perforated track is provided in the displacement element, the perforations preferably pass all the way through the displacement element to allow soil or other material to be pushed through the displacement element. 
         [0177]    As can be seen in  FIG. 5A , the sprocket  434  is configured to leave a gap  435  between the track and the troughs  439  of the sprocket as those troughs pass over the track, the troughs being between two adjacent teeth of the sprocket. In this embodiment, the needle rollers  437  and the troughs have different radii of curvature to prevent a needle roller completely filling a trough. In this embodiment, the trough has a radius of curvature less than a radius of curvature of the needle rollers. The gap  435  enables grit or dirt to be held in the gap until it can escape without jamming the device or forcing the device to crush the dirt or grit which may be difficult where the dirt or grit is hard. 
         [0178]    The coupling of the shaft to the drilling element enables the drilling element to be rotated through a full rotation. It also enables an efficient transfer of rotational force from the shaft to the drilling element. 
         [0179]    The embodiment of  FIG. 5  can also optionally be provided with a fluid distribution network as described in connection with  FIG. 1 . 
         [0180]    The device of  FIG. 5  is operated in a similar way to the device of  FIG. 1  during removal of a cable. However, the device of  FIG. 5  is particularly useful for hard materials such as cement bound sand where significant drilling is required. 
         [0181]    As the drilling unit  230  described above advances the shaft  20  which is coupled into the coupling element  418 , it also rotates the shaft  20  preferably continuously in the same angular direction. This causes rotation of the coupling element  418 , which in turn causes rotation of the sprocket  434 . 
         [0182]    The cooperation of the sprocket  434  and track  436  means that the sprocket  434  causes rotation of the displacement element  412  with respect to the stator  417 . 
         [0183]    The rotation of the displacement element  412  with respect to the stator  417  causes rotation of the drilling element  415  with respect to the stator  417 , preferably continuously in the same angular direction, causing the drilling element to provide a drilling action on material in front of it, thereby loosening the material. 
         [0184]    Longitudinal forces applied to the shaft are transferred to all components of the device thereby advancing the device through the material and causing the displacement element to displace the material as described above. 
         [0185]    As explained above, a difficulty in drilling devices has been in transferring rotational motion of a shaft to a drilling element the axis of which is laterally offset. The embodiment of  FIG. 5  is able to transfer rotational motion of a shaft to rotational motion of the drilling element. Furthermore, it is able to do this without the mechanism for transferring the rotational movement becoming clogged with the loosened material. 
         [0186]      FIG. 6  is a schematic cut-away view of a device according to another embodiment of the invention. The device corresponds in many respects to the device of  FIGS. 5 and 5A , except that the stator has a tapering back. 
         [0187]      FIG. 7  is a schematic side view of a device according to another embodiment of the invention. The device of  FIG. 7  is similar in many ways to the device of  FIG. 5  except that in the embodiment of  FIG. 7  there are provided a plurality of adjacent perforated tracks  536  instead of the single perforated track  436  shown in  FIG. 5 . In this embodiment, there are provided first, second and third perforated tracks  536 , although other numbers of perforated tracks can be provided in other embodiments. Furthermore, instead of a single sprocket  434  as in  FIG. 5 , there is provided a plurality of sprockets  534 , each sprocket being coupled to a respective perforated track in the manner described in respect of  FIG. 5 . An advantage of having a plurality of tracks and sprockets in this manner is that greater rotational power can be provided to the displacement element, and the likelihood of the sprocket and track becoming decoupled or a component snapping is reduced. 
         [0188]    With regard to the method of removing a cable, it is not necessary to cut the cables if ends of cables can be located. Cables are generally provided in  300   m  sections. It is preferable to remove sections of  150   m , thereby cutting each cable section substantially in two. However, different lengths of cable can be removed if appropriate and/or desired. 
         [0189]    Furthermore, although the cable is described as being pulled from the launch site, it is equally possible to pull it from the receive pit. 
         [0190]    Additionally, if the cable does not need cutting to form the second end, it is not always necessary to excavate a receive pit. 
         [0191]    Further details of embodiments of the invention are included in the attached annexes 1 to 4. 
         [0192]    All optional and preferred features and modifications of the described embodiments are usable in all aspects of the invention taught herein. Furthermore, all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with one another. 
         [0193]    The disclosures in British patent application numbers 1408164.0 and 1422808.4, from which this application claims priority, and in the abstract accompanying this application are incorporated herein by reference.