GB2597073A

GB2597073A - Clearnet - sub-duct extraction

Info

Publication number: GB2597073A
Application number: GB2010788.4A
Authority: GB
Inventors: Snowden Robert
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-07-14
Filing date: 2020-07-14
Publication date: 2022-01-19
Also published as: GB202010788D0

Abstract

Provided is an apparatus suitable for removing a sheath that surrounds a cable, particularly in the context of underground telecoms cables. The apparatus comprises a drive assembly, such as a track with gripping teeth, that feeds a sheathed cable towards a cutting assembly 10. The cutting assembly 10 comprises two clamps 11, each with a rotary cutter 12, that clamp the sheath 3. When the sheath 3 passes through the clamps 11, the cutters 12 make longitudinal cuts in the sheath so that the sheath is cut in two and is thus separated from the cable. Each cutter 12 may be driven by a motor up to a speed of 30,000 rpm. Also provided is a method of separating a sheath from a cable using this apparatus and subsequently wrapping the separated sheath around a rotary drum.

Description

Apparatus and Method for Slitting a Sub-Duct to Free a Cable [1] klbe present invention relates to a method and equipment for removing a duct from around a cable/fibre without damaging the cable/fibre. More specifically the present thvention relates to apparatus and method for slitting a sub-duct encasing a cable/fibre, the sub-duct located within a primary duct. Even more specifically the present invention relates to removing the protective sub-duct surrounding a telecommunications cable housed within an underground primary conduit.

Background

[2] Across the world there are many millions of kilometres of sub-ducts installed in primary ducts beneath the ground between access chambers. Each of these sub-ducts carries one or multiple fibre optic cables transmitting vital data between communities and countries. Years ago, it was thought these sub-ducts gave valued added protection to the fibre optic cables however it is now noted they give only an extra 5% protection to the cables but increase 12% in the constructive build cost.

[3] As years go by and the telecoms networks increase in growth and new customers then these sub-ducts get filled with cables then eventually all the capacity 20 of both the primary duct and sub-ducts become too congested "to total capacity".

[4] Equipment for removing sub-ducts from around cables within a primary ducted network are already known. EP17176562.1 which discloses equipment which pulls the duct longitudinally onto fixed blades within a block head. The fixed blades 25 then cut the sub-ducts into two which can then be removed from the network.

[005] However due to the slow method of the technology and restricted space within the public highway these long lengths of extracted sub-ducts require a lot of highway management, street works noticing/permitting thus large areas of public roads and footpaths become restricted for lengthy periods. This method can be problematic for many reasons such as traffic management, the general public's safety etc. [6] A problem with such equipment is that the sub-duct, when slit, is required to be physically handled as it is removed in individual lengths which could be distances exceeding 100 metres at a time This requires street management and public protection during the procedure of removing the sub-ducts. Additionally, and following the removal of the slitted sub-duct further processing and cutting is required to reduce the slitted sub-duct into smaller more processable pieces. This further processing requires additional equipment and more manual operators within the site setup thus further obstructing the work site with a greater working space required. The use of such known equipment is consequently complicated and costly with such methods.

[7] The present innovation looks to overcome the problematic issues of the prior art.

Summary of the Invention

[8] According to a first aspect of the invention there is provided an apparatus for cutting a tubular sub-duct which surrounds a cable, the sub-duct being arranged in a primary duct. The apparatus comprising a drive assembly and a cutting assembly. The cutting assembly comprising a cutting head having two halves displaceable relative to one another such that they can clamp around the duct, each half having a rotary cutter such that in use when clamped around a sub-duct the rotary cutters engage opposing sides of the sub duct, and rotate about an axis substantially perpendicular to a longitudinal axis of the sub-duct, cutting the sub duct in two as it passes through the cutting apparatus.

10091 An embodiment according to the first aspect, further comprising a protective sleeve arranged in between the two halves of the cutting head and 5 respective cutters, such that in use it can encompass the cable and protect it from the rotary cutters. The protective sleeve may be in two halves before surrounding the cable.

[0101 An embodiment according to the first aspect, wherein the drive assembly 10 comprises at least one, preferably a plurality of tracks adapted to grip the duct. Preferably the tracks comprise gripping teeth.

[0111 An embodiment according to the first aspect wherein the cutting assembly further comprises two motors, one associated with each half of the cutting head 15 respectively and each driving their respective rotary cutters. Preferably the motors can drive the rotary cutters at up to 30,000rpm.

[0121 According to a second aspect of the invention there is provided a method of cutting a duct comprising the steps of: (a) providing an apparatus according to the first aspect of theinvention; (b) Grasping the sub duct within the drive assembly; (c) Engaging the drive assembly to pull the sub-duct along its longitudinal axis into engagement with the cutting assembly such that the cutting heads engage opposing sides of the sub-duct; (d) Spinning the dual router cutters about an axis substantially perpendicular to the longitudinal/horizontal axis of the sub duct so as to split the sub-duct into two halves as it is urged through the cutting assembly.

[13] An embodiment according to the second aspect, wherein step (a) further 5 comprises the step of: securing the cable held within the sub-duct in a protective sleeve.

[14] An embodiment according to the second aspect, wherein step (d) further comprises the steps of: providing a rotary drum/spool; and, collecting the two halves 10 of the sub-duct around a rotary drum for transport.

Brief Description of the Drawings

[15] The invention will be described in more detail, by way of example, with 15 reference to the following drawings: [16] Figure 1 depicts containing subducts and cables; [17] Figure 2 depicts a manhole for access to the ducts; [18] Figure 3 depicts a manhole for access to the ducts with the device installed; [19] Figure 4 depicts an embodiment of the cutting assembly.

S

Detailed Description

[20] A preferred embodiment of the invention is for the removal of protective sub-ducts (traditionally made from plastic) around telecommunication cables (fibre optic etc.) contained in underground primary ducts. Access to these primary ducts and therefore the sub-ducts and encased cables is conventionally through man holes. A simplified schematic of these man holes 6 is shown in figure 2. Underground tunnels 1 hold primary conduits 2. The primary conduits 2 each surround at least one, and normally a plurality of sub ducts 3 (only one shown for simplicity) each sub-duct 3 encasing a cable 4. As can be seen, the primary conduits 2 do not extend into the manhole 6 and instead top at the side walls of the manhole 6. Conduits 3 and cable 4 extend into the manhole so that they are accessible for maintenance etc. Inside the manhole 6 the cable 4 is divided at a connector 7, the connector 7 detachably connecting the two ends of cable 4.

[21] In order to remove the subduct 3 from around the cable 4. As shown in figure 3, the device 8 for cutting the sub-duct 3 and removing it from around the cable 4 is positioned in the manhole 6 and held over the entrance to tunnel 1 in the side wall of manhole 6. The device 8 is held in place by any suitable means known to the skilled person. The cable 4 is passed through device 8 and the sub-duct 3 is engaged with the device 8. Then the device 8 grips and pulls the sub-duct 3 into a cutting head within device 8, which splits and removes the sub-duct 3.

[22] Apparatus 8 comprises two parts. A drive assembly and a cutting assembly.

The drive assembly consists of a means to grip and pull the sub-duct 3 into the cutting assembly. The drive assembly can be of any suitable means known to the skilled person, and therefore for conciseness is not discussed in detail here. In a preferred embodiment comprises a high torque caterpillar haul off device having specifically designed gripping teeth for gripping the sub-duct 3.

[23] The cutting assembly 10 is shown in figure 4. It comprises two adjustable cutting blocks 11, adjustably mounted on slide 14 such that in use the blocks 11 can be separated to position around cable 4 and sub-duct 3, then closed together to the 5 appropriate distance to encase and cut sub duct 3 as the drive assembly urges. The actual cutting is done by two opposing rotary cutters 12 mounted within blocks 11. Both rotary cutters 12 rotate about an axis which is substantially perpendicular to the longitudinal axis of the sub-duct 3 as it passes through the cutting assembly. As the sub-duct 3 passes through the cutting assembly the rotary cutters 12 slit either 10 side of the sub duct 3 along its longitudinal/horizontal axis and therefore splitting the subduct 3 into two halves.

[24] Each rotary cutter 12 comprises a cutting head and a router shaft, and is powered via a 110v electric compact motor 13. The motors 13 are mounted onto the cutting assembly 10 and can move with their respective associated heads 11. Preferably the router shaft is adjustable in length so that there can be fine adjustment so that the cutter heads are optimally positioned apart to split the sub duct 3.

025] In a preferred embodiment the cutting assembly further comprises a split tube protector for protecting the cable 4 from the rotary cutters 12. The split tube protector preferably is formed of two halves which can be attached around the section of cable situated between the heads 11.

[026] The block heads 11 split into two parts as does the protector tube, the cable 4 is then encased within the split protector tube. The sub-duct is then presented to the face of the cutting heads, there is approximately 6mm of excess space between the annulus of the protector tube and the inner wall of the sub-duct. The bottom of the router head which has a concave shaped circumference fits comfortably between the annulus of the protector tube and the inner wall of the sub-duct. Slightly above the bottom of the router head "concave protector base" is the main body of the router cutter, this router body rotates at some 30,000rpm creating a dual slit along the horizontal axis of the sub-duct.

[027] The dual cutting heads rotate at 30,000rpm, the provides a much smoother cutting than fixed blades like in LP17176562.1, this in turn allows the drive assembly to extract sub-duct at a faster rate, allowing a release of up to 60 metres of freed up sub-duct per minute. This is fed directly onto a hydraulically rotating operated sub-duct drum trailer thus reducing the amount of workspace required and manual site workers within the work site. From a single site setup as much as 1kin can be extracted in a single operation. The extracted sub-duct is then taken straight to processing site to be recycled.

[028] In a preferred embodiment, use of the device to remove the sub-duct comprises the steps of: 1. Providing the device as described above around a sub-duct; a. Optionally securing the cable held within the sub-duct in a protective split tube; 2. Grasping the sub duct within the drive assembly; 3. Engaging the drive assembly to pull the sub-ducts along its horizontal/longitudinal axis into engagement with the cutting assembly such that the cutting heads engage opposing sides of the sub-duct; 4. Spinning the dual router cutters about an axis substantially perpendicular to the longitudinal/horizontal axis of the sub duct so as to split the sub-duct into to halves as it is urged through the cutting assembly.

b. Optionally collecting the two halves of the sub-duct around a rotary drum for transport.

[029] The invention has been described with reference to a preferred embodiment. 5 The description is intended to enable a skilled person to make the invention, not to litnit the scope of the invention. The scope of the invention is determined by the claims.

Claims

Claims 1. An apparatus for cutting a tubular sub-duct which surrounds a cable, the sub-duct being arranged in a primary duct; the apparatus comprising a drive assembly and a cutting assembly; the cutting assembly comprising a cutting head having two halves displaceable relative to one another such that they can clamp around the duct, each half having a rotary cutter such that in use when clamped around a sub-duct the rotary cutters engage opposing sides of the sub duct, and rotate about an axis substantially perpendicular to a longitudinal axis of the sub-duct, cutting the sub duct in two as it passes through the cutting apparatus.
2. An apparatus as claimed in claim 1, further comprising a protective sleeve arranged in between the two halves of the cutting head and respective cutters, such that in use it can encompass the cable and protect it from the rotary cutters.
3. An apparatus as claimed in claim 2, wherein the protective sleeve is in two halves before surrounding the cable.
4. An apparatus as claimed in any preceding claim, wherein the drive assembly comprises at least one, preferably a plurality of tracks adapted to grip the duct.
5. An apparatus according to claim 4 wherein the tracks comprise gripping teeth.
6. An apparatus according to any preceding claim wherein the cutting assembly further comprises two motors, one associated with each half of the cutting head respectively and each driving their respective rotary cutters.
7. An apparatus according to claim 6 wherein the motors can drive the rotary cutters at up to 30,00()rpm.
8. A method of cutting a duct comprising the steps of (a) providing an apparatus as claimed in any preceding claim; (b) Grasping the sub duct within the drive assembly; (r) Engaging the drive assembly to pull the sub-duct along its longitudinal axis into engagement with the cutting assembly such b 2, b b that the cutting heads engage opposing sides of the sub-duct; (d) Spinning the dual router cutters about an axis substantially perpendicular to the longitudinal/horizontal axis of the sub duct so as to split the sub-duct into two halves as it is urged through the cutting assembly.
9. A method according to claim 8 when dependent on any one of claims 2 or 3, wherein step (a) further comprises the step of: securing the cable held within the sub-duct in a protective sleeve.
10. A method according to any one of claims 8 or 9, wherein step (d) further comprises the steps of: providing a rotary drum/spool; and, collecting the two halves of the sub-duct around a rotary drum for transport.