CABLE INSTALLATION IN DUCTING

Abstract: In a method of installing a cable in ducting from a location (60) intermediate the length of the ducting, the cable is provided in a coil (62) at the location and some cable (64) is passed from one end of the coil into a first portion of the ducting extending from the location to one end of the ducting and the remaining cable (66) is passed from the other end of the coil into a second portion of the ducting extending from the location to the other end of the ducting.

Description: Cable Installation in Ducting This invention relates to installing a length of cable in ducting from a location intermediate the ends of the ducting. The invention is particularly, although not exclusively, applicable to installing optical fibre cables comprising at least one optical fibre unit disposed within an extruded sheath, the or each unit comprising a plurality of optical fibres. Heretofore, lengths of such optical fibre cables have been installed in ducting from locations intermediate the ducting ends by coiling the cable on a drum, transporting the drum to the location, mounting the drum for rotation about its axis for paying cable off the drum, rotating the drum and feeding the length of the cable into a first portion of the ducting extending from said location until the cable is installed in that portion, thereafter feeding the remainder of the cable onto the ground, locating the end of the cable and feeding the remainder of the cable into a second portion of the ducting extending from said location. This known installation method has two main disadvantages. Firstly, the rotating drum presents a safety hazard both to installation operatives and members of the public when the location is in a public place. In this connection a typical drum rotational speed when installing optical fibre cables is 50 r.p.m. Secondly the feeding of the cable onto the ground can result in damage to the cable and additionally represents a safety hazard. An object of the invention is to enable the above two disadvantages to be overcome. This is broadly achieved by a method of installing a cable in ducting from a location intermediate the ends of the ducting, comprising providing the cable in a coil at the location, passing cable from one end of the coil into a first portion of the ducting extending from the location to one end of the ducting and passing cable from the other end of the coil into a second portion ofthe ducting extending from the location to the other end of the ducting. As will be appreciated the coil of cable does not rotate in this method and the cable is fed from the coil directly into both ducting portions. The invention also includes apparatus for use in installing a length of cable in ducting from a location intermediate the ends of said ducting, said apparatus comprising: a generally cylindrical housing for housing the length of cable in a coiled condition, said housing comprising respective end walls removably mounted relative to opposite end portions of a generally cylindrical side wall; and a support means supporting said housing for pivotal movement about an axis transverse to the axis of the housing between a first position in which a first one of said opposite end portions is uppermost and a second position in which the second one of said opposite end portions is uppermost. The invention also includes a method of installing a cable in ducting from a location intermediate the ends of said ducting using an apparatus as defined in the last preceding paragraph and comprising: housing the length of cable to be installed in said housing in a coiled condition; positioning said apparatus adjacent said location with said housing in said first position; removing the uppermost end wall from the housing; locating the end of the cable adjacent the end portion of the housing from which the end wall has been removed; passing said end and part of the length of cable extending therefrom through said end portion of the housing from which the end wall has been removed and into a first portion ofthe ducting extending from said location; remounting the removed end wall to the housing; pivoting said housing about said axis transverse to the axis of the housing to said second position removing the now uppermost end wall from the housing; locating the remaining end of the cable and passing that end and the remaining length of the cable extending therefrom through the end portion of the housing from which the end wall has been removed and into a second portion ofthe ducting extending from said location. Advantageously, the length of cable may be fed into said housing at a site remote from said location said apparatus being transported to said location for positioning adjacent said location. The support means of the apparatus may include a base and opposed stub axles mounted relative to said base and connected to opposed portions of said housing side wall. The support means may also include means for supporting said housing in said first and second positions, which means may comprise length adjustable supports extending from said base to engage said housing at or adjacent the end portion which is lowermost when said housing is in said first or second position. The base of the apparatus may be provided with wheels or endless tracks. A cable guide may be positioned above said housing. Preferably the end walls are provided with respective hubs which fit one within the other when said end walls are mounted to said opposite end portions ofthe housing side wall. Advantageously, the housing side wall is provided with a closable aperture through which cable may pass. Preferably, the housing side wall and/or the housing end walls comprises bars and/or tubes. In order for the invention to be well understood, a preferred embodiment thereof which is given by way of example only, will now be described with reference to the accompanying drawings, in which: Figure 1 schematically illustrates apparatus for use in installing a length of cable in ducting from a location intermediate the ends ofthe ducting; Figures 2 and 2A are respective plan and side schematic views of part of the housing of the apparatus, the view in Figure 2A being taken in the direction of arrow 2A in Figure 2; Figures 3 and 3A are respective plan and side schematic views of one of the end walls of the housing; and Figures 4 to 8 schematically illustrate successive steps in the installation of a cable using the apparatus shown in Figure 1. Referring first to Figure 1, the apparatus illustrated therein and designated 10 comprises a generally cylindrical housing 12 for housing a length of cable (not shown) in a coiled condition. The housing 12 comprises respective end walls 14 and 16 which are removably mounted relative to opposite end portions 18 and 20 of a generally cylindrical side wall 22. The end walls 14 and 16 are provided with respective hubs 24 and 26 which fit one within the other when the end walls 14 and 16 are mounted to the opposite end portions 18 and 20 as illustrated in Figure 1. As will be understood from Figures 2, 2A, 3 and 3A the housing side wall 22, the end walls 14 and 16 and the hubs 24 and 26 are formed of bars and/or tubes which are connected to form grids such that the housing 12 takes the form of a cage. Figures 3 and 3 A show end wall 14 with its hub 24 and it is to be understood that end wall 16 and its hub 26 are similarly constructed but with the hub 26 having a larger diameter than the hub 24 so that the hub 24 may fit within the hub 26 as shown in Figure 1. The side wall 22 is provided with a slot 28 closable by a gate 30 through which cable within the housing may pass as will be explained in more detail hereinafter. Referring back to Figure 1, the apparatus 10 also comprises a support generally referenced 32 for supporting the housing 12 for pivotal movement about an axis 34 transverse to the axis 36 of the housing between a first position (as illustrated in Figure 1) in which end portion 18 of the housing side wall is uppermost and a second position as illustrated in Figure 7 in which end portion 20 ofthe housing side wall is uppermost. To this end, the support 32 includes a base 38 and opposed stub axles 40 and 42 mounted relative to the base 38 on mountings 44 and 46 respectively and connected to opposed portions 48 and 50 of the housing side wall. The support 32 also includes means for supporting the housing in the first and second positions mentioned above, preventing or at least limiting pivotal movement of the housing about axis 34. The means illustrated comprise length adjustable supports 52 extending from the base 38 to engage the housing at or adjacent the end portion 18 or 20 which is lowermost when the housing is in its first or second position. A cable guide 54 is mounted on the base 38 so as to be above the housing and disposed on or near the housing axis 36. The base 38 is provided with wheels 56 (one of a pair of which is shown) to enable the apparatus to be towed. Other similar means such as endless tracks may be used instead. Alternatively, the base 38 may be mounted on a truck or similar motor vehicle. In use a length of cable is fed into the housing at a site remote from the location intermediate the ends of the ducting, for example in a factory where the cable is produced. The cable may be fed into the housing with the housing already mounted to the base 38 as illustrated in Figure 1 or before such mounting. In each case the cable is fed through end portion 18 of the housing from which end wall 14 has been removed and is coiled about the hub 26. When the complete length of cable has been fed into the housing the previously removed end wall 14 is replaced, its hub 24 being received within hub 26. Installation of the cable in the housing in ducting will now be described with particular reference to Figures 4 to 8. Firstly, the apparatus 10 is towed to the location intermediate the ends of the ducting where access to the ducting intermediate its ends is provided. Typically this access will be provided by a pit from which a first portion of the ducting extends to one end of the ducting and a second portion of the ducting extends to the other end of the ducting. In schematic Figures 4 to 8 an entrance to the access pit is referenced 60 and the ducting portions, which are underground, are not illustrated. As shown in Figure 4 the apparatus 10 is positioned adjacent the entrance 60 of the pit with the housing in its first position and with uppermost end wall 14 removed to provide access through the end portion 18 of the housing to the cable coiled within the housing. In Figures 4 to 8 the coil of cable in the housing is referenced 62. The end of the cable adjacent the end portion 18 of the housing is located and that end and the cable 64 extending therefrom is passed through the end portion 18 and the cable guide 54 into the access pit and through the first portion of the ducting to the end of the ducting. The cable may be passed through the ducting portion by being pulled therethrough and/or by being blown therethrough in the known manner. As the cable is fed into the first portion of the ducting the size of the coil 62 in the housing is reduced and Figure 5 illustrates the situation when the cable 64 is fully installed in the first portion of the ducting. At this stage, as illustrated in Figure 6, cable 64 is released from the cable guide and passed through the slot 28 in the side wall 22 which slot is then closed by the gate 30 to retain the cable between the end portions of the side wall. Also, the end wall 14 is remounted as shown in Figure 6. Next, the length adjustable supports 52 supporting the housing in its first position are removed and the housing is pivoted about axis 34 to its second position and the supports refitted to support the housing in that second position. If necessary, the apparatus is repositioned relative to the entrance 60 to the access pit as shown in Figure 7 and as also illustrated in Figure 7, the now uppermost end wall 16 of the housing is removed to give access through the end portion 20 of the housing to the cable coiled within the housing. The remaining end of the cable is located and that end and the cable 66 extending therefrom is passed through the end portion 20 and the cable guide 54 into the access pit and through the second portion ofthe ducting to the other end of the ducting. The cable 66 may be passed through the second portion of the ducting by being pulled and/or blown therethrough. Figure 8 illustrates the situation when the cable 66 is fully, or almost fully, installed in the second portion of the ducting and no cable remains in a coiled condition in the housing. At this stage the cable 66 is released from the cable guide 54 and the cable 64 is passed through the slot 28 in the side wall 22 of the housing after the gate 30 has been opened. In this way, the cable is free of the housing and the remaining loop of cable can be stored in the pit or passed into the second portion of the ducting. This completes the installation of the cable in the ducting and the apparatus 10 can be towed away for a future installation. It is to be understood that the first and second portions of the ducting referred to herein are typically discrete ducts with adjacent ends located in the access pit. In a particular embodiment for use in installing optical fibre cable having an outer diameter of 15 mm and a weight of 150 kg/km, the illustrated housing has a cylindrical side wall 22 with a height of 650 mm and an outer diameter of about 1700 mm and a hub 26 with an outer diameter of about 700 mm. Such a housing is able to house about 4 km of such cable.

Claims: CLAIMS: 1. Apparatus for use in installing a length of cable in ducting from a location intermediate the ends of said ducting, said apparatus comprising: a generally cylindrical housing for housing the length of cable in a coiled condition, said housing comprising respective end walls removably mounted relative to opposite end portions of a generally cylindrical side wall; and a support means supporting said housing for pivotal movement about an axis transverse to the axis of the housing between a first position in which a first one of said opposite end portions is uppermost and a second position in which the second one of said opposite end portions is uppermost. 2. Apparatus as claimed in claim 1 wherein said support means includes a base and opposed stub axles mounted relative to said base and connected to opposed portions of said housing side wall. 3. Apparatus as claimed in claim 2, wherein said support means includes means for supporting said housing in said first and second positions. 4. Apparatus as claimed in claim 3, wherein said means for supporting said housing in said first and second positions comprises length adjustable supports extending from said base to engage said housing at or adjacent the end portion which is lowermost when said housing is in said first or second position. 5. Apparatus as claimed in claim 2, 3 or 4, wherein said base is provided with wheels or endless tracks. 6. Apparatus as claimed in any one of claims 1 to 5, wherein a cable guide is positioned above said housing. 7. Apparatus as claimed in any one of claims 1 to 6, wherein said end walls are provided with respective hubs which fit one within the other when said end walls are mounted to said opposite end portions of the housing side wall. 8. Apparatus as claimed in any one of claims 1 to 7, wherein said housing side wall is provided with a closable aperture through which cable may pass. 9. Apparatus as claimed in any one of claims 1 to 8 wherein the housing side wall and/or the housing end walls comprises bars and/or tubes. 10. A method of installing a cable in ducting from a location intermediate the ends of said ducting using an apparatus as claimed in any one of the preceding claims and comprising: housing the length of cable to be installed in said housing in a coiled condition; positioning said apparatus adjacent said location with said housing in said first position; removing the uppermost end wall from the housing; locating the end of the cable adjacent the end portion of the housing from which the end wall has been removed; passing said end and part of the length of cable extending therefrom through said end portion of the housing from which the end wall has been removed and into a first portion of the ducting extending from said location; remounting the removed end wall to the housing; pivoting said housing about said axis transverse to the axis of the housing to said second position removing the now uppermost end wall from the housing; locating the remaining end of the cable and passing that end and the remaining length of the cable extending therefrom through the end portion of the housing from which the end wall has been removed and into a second portion ofthe ducting extending from said location. 14 11. A method as claimed in claim 10, wherein said length of cable is fed into said housing at a site remote from said location and said apparatus is transported to said location for positioning adjacent said location. 12. A method of installing a cable in ducting from a location intermediate the length of the ducting, comprising providing the cable in a coil at the location, passing cable from one end of the coil into a first portion of the ducting extending from the location to one end of the ducting and passing cable from the other end of the coil into a second portion of the ducting extending from the location to the other end ofthe ducting.

Inventors: SUTEHALL RALPH, SUTEHALL, RALPH
Applicants: PIRELLI GENERAL PLC, SUTEHALL RALPH, SUTEHALL, RALPH
Application year: 2000
Main classification: H02G1
IPC codes: G02B6, H02G1