Technical Field

The present invention relates to a system and a corresponding method for installing ducts/cables in micro trenches.

Background

When installing ducts for cables (e.g. communication cables) in the ground it is often a requirement that each duct should be able to be identified along its entire length. This in order to know which duct leads to a particular destination.

Today, mainly ducts with different colours or colour codings delivered directly from the factory are used. This causes problems in the production because each dimension must be manufactured in numerous colours. It will also cause logistical problems during installation since it has to be ensured that ducts with all used types of marking/co lours in each dimension is available on site and in sufficient quantities. From experience, it can be assumed that installation as planned often cannot be performed, but instead must wait for days or weeks because ducts/cables with specific markings are missing.

A system that requires that a unique marking is added to each duct during manufacturing, involves major manufacturing and logistical problems because a large number of ducts must be produced and supplied for each duct size (dimension).

Summary

An objective of embodiments of the present invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.

The above and further objectives are achieved by a system for installation of ducts/cables in micro trenches; said system being arranged for sawing micro trenches and placing ducts/cables in micro trenches in a continuous process; said system comprising a sawing machine including a saw blade and a stabilizing device, said stabilizing device being arranged directly behind said saw blade and being arranged to stabilise the sides of said micro trench, said stabilizing device comprising guiding means arranged for guiding said ducts/cables (29) into said micro trench; said system further comprising:

- at least one drum for holding ducts/cables;

- a duct guiding device arranged to guide said ducts/cables from said at least one drum to said stabilizing device;

- a marking device arranged to mark each of said ducts/cables so that each of said duct/cable is given a unique identity; and wherein the stabilizing device further is arranged to:

- install said marked ducts/cables in said micro trench by means of said guiding means based on said unique identity.

The above and further objectives are also achieved by a method for installation of ducts/cables in micro trenches by using a system comprising:

- a sawing machine including a saw blade and a stabilizing device, said stabilizing device being arranged directly behind said saw blade and being arranged to stabilise the sides of said micro trench, said stabilizing device comprising guiding means arranged for guiding said ducts/cables into said micro trench; and

- at least one drum for holding ducts/cables; the method comprising the steps of:

guiding said ducts/cables from said at least one drum to said stabilizing device;

marking each of said ducts/cables so that each of said duct/cable is given a unique identity;

installing said marked ducts/cables in said micro trench based on said unique identity.

The present invention does not require marking of the ducts from the factory. This means that only one type of duct for each dimension needs to be delivered to the installation sites. Therefore, the present method is cost saving. Costly installation stops, because ducts/cables with a certain marking or colour is missing, when needed at the installation site is totally avoided by the present solution.

Embodiments of the present system are given in the appended claims. Embodiments of the present method are the same, mutatis mutandis, as the corresponding embodiments of the system.

Further applications and advantages of the present invention will be apparent from the following detailed description. Brief description of figures

Fig. 1 : shows a sawing machine 8 with its saw blade 14 installing ducts/cables 29 by means of the stabilizing device 13 in a micro trench 1 below ground level 10.

Fig. 2: shows the underground part of the sawing machine, in operation, comprising a saw blade 14 and a stabilizing device 13 with its guiding means 17 (indicated by dotted lines) for guiding ducts/cables into the micro trench in a preserved order. The enlarged view of the output of the guiding means shows one possible configuration with 2 columns and 7 rows.

Fig. 3: shows a system 100 according to an embodiment of the present invention with the location case 1 wherein the marking device 23 is arranged between the drums 28 on the trailer 27 and the stabilizing device 13 of the sawing machine 8. Fig. 3 also shows a combined feeding device 24 and duct guiding device 30

Fig. 4: shows a system 100 according to an embodiment of the present invention with the location case 2 wherein the marking device 23 is arranged together with a re- spooling function used to fill the drums 28 for the trailer 27 from a much larger storage drum 20.

Fig. 5: shows a flowchart of an embodiment of the present invention.

Figs. 6-8 shows further aspects of the present invention.

Detailed description

According to embodiments of the present invention, the ducts 29 are marked using a marking device 23 before the ducts 29 are installed/placed in the ground. The marking device 23 is used to give each duct 29 a unique identity. The marking is done continuously along the entire length of the duct 29, or repetitive, e.g. every 50-100 cm depending on the application. The distance between the markings shall be sufficiently far for the desired marking to fit on the duct 29 but not as far apart that it will take time to find the marking when a duct 29 has to be identified if, for example, it is accidentally cut when digging in the ground. The proposed solution is primarily meant to be used when a number of ducts 29 are installed using a sawing machine 8 equipped with a stabilizing device 13 (plough), but it can also be used on other occasions where a variety of ducts 29 with different labels are needed. Thereby, logistical problems are minimized. The sawing machine 8 is used for sawing micro trenches 1 and may be arranged to pull a trailer 27 comprising at least one drum holder (or in short: drum) for holding a number of drums 28 for ducts/cables 29. The trailer 27 may also comprise a tank 26 with water for cooling of the saw blade 14. The water tank 26 is preferably positioned low and centrally on the trailer 27 to provide a low centre of gravity and stability. The water tank 26 may also be splash proof.

The drum holder, which in one embodiment is arranged on the trailer, holds the drums 28 with ducts 29 required for the installation (typically, up to 15 - 25 drums 28 are needed). As the trailer 27 fully loaded may weigh more than 2 tons it should preferably have two wheels on each side of the trailer 27. It is advantageous if the trailer 27 can be made so narrow that it fits on a pavement. Preferably, the drum holder can be arranged to be folded down to make the trailer 27 more compact during transportation. Other parts that may be mounted on the trailer, such as the re- spooling function and the marking function can be removed or folded down during transportation. Electrical power to the re-spooling function and other features that require electrical power on the trailer may be taken from the sawing machine 8, or from external power sources.

Marking device

Marking of the ducts 29 may be done with laser, thermal heat, ink/paint or any other suitable method. Therefore, the unique identity is created from unmarked ducts/cables by adding a marking in the form of a unique colour, code, text or in any other way.

The idea is that each duct 29 should have a unique marking along its entire length. The marking might be done by a laser melting a text string into the ducts 29, repeated e.g. every 50-100 cm. The text string is unique for each duct 29 in a group of ducts 29 installed together.

For location case 1 (see below) when many ducts 29 must be marked at the same time, this can be done with a single laser if the ducts 29 are fed tightly side by side through the marking device. By utilizing the ducts' 29 forward motion the deflection of the laser beam need only be made in a single direction perpendicular to the duct 29 motion direction. This is a cost effective solution. A5. Hence, according to this embodiment said marking device 23 comprises a laser providing a controlled laser beam, wherein the laser beam is deflected in a direction perpendicular to the motion of the ducts/cables 29.

An alternative method is to mark each duct 29 with the aid of a wheel that somewhere along its periphery has a heated stencil, which melts a unique marking on the duct 29 as it is fed forward. This calls for one such wheel for each duct 29 to be marked simultaneously. A third method could be to use a coloured plastic film from which some of this film is melted on to the ducts 29 in a unique pattern such as a text string.

The marking device 23 is arranged to handle all different dimensions of ducts 29 used. A minimum required marking is a unique marking in the group of cables/ducts in one and the same micro trench according to an embodiment of the present invention. However, if some sort of text is used, the marking could be made unique in the whole installation or in the whole region or in the whole country or in the whole world. A problem is that it may be a tedious job to read all characters needed to identify a particular marking made unique in a large area.

In most cases it is therefore sufficient to add a marking making the ducts/cables unique in the group they belong to, which in this case is in one and the same micro trench. The marking should also be resistant to wear and to aging year after year in the ground. A marking method that fulfils these requirements is a marking method based on heat. The heat may be generated from a laser or from electrical heating and it is allowed to melt in a pattern in the ducts/cables or melting a pattern from a plastic film onto the ducts/cables. Location of the marking device

Location Case 1 : with reference to Fig. 3, the marking device 23 is in this case arranged between the drums 28 on the trailer 27 and the stabilizing device 13 of the sawing machine 8. This means that the marking device 23 might be mounted either on the trailer 27 or on the sawing machine 8. The unmarked ducts 29 on the drums 28 on the trailer 27 will be marked before they reach the stabilizing device 13. In this case, the marking device 23 must in parallel and simultaneously be able to handle and mark all ducts 29 that are being installed.

Location Case 2: with reference to Fig. 3, the marking device 23 is in this case arranged together with a re-spooling function used to fill the drums 28 for the trailer 27 from a much larger storage drum 20, delivered from the factory. In this case, ducts 29 are marked when they are spooled on to the smaller drums 28 for the trailer. The re-spooling device and the marking device 23 might be placed on the trailer 27, pulled by the sawing machine 8, or located on a separate trailer. Re-spooling and marking is, in this case, done before the installation begins, and these devices need not be on the trailer 27 or sawing machine 8 during the actual installation. In this case, the marking device 23 only has to mark one duct 29 at a time.

Measuring device

The trailer 27 or the sawing machine 8 may also be equipped with a measuring device 21 that measures the installed distance for each duct 29. This measurement may also be added to the text string on the ducts 29 by the marking device 23, thus adding a length mark on the ducts 29. The measuring device 21 can also be used in conjunction with a cutting device 22 to automatically cut a specific duct 29 after a specified and predetermined length or distance. If a cutting device 2 is not used the measuring device gives the operator information to determine where a duct 29 shall be cut manually. Cutting device

The measuring device 21 may be complemented by a cutting device 22 that cuts a certain duct 29 at a predetermined location based on measurements performed by the measuring device 21. Feeding device

The sawing machine 8 and/or the trailer 27 may also be equipped with a feeding device 24 for ducts 29. The feeding device 24 is arranged to compensate for the friction of the ducts 29 and drums 28 and is located/arranged before the stabilizing device 13. The feeding device 24 may be arranged so that each duct 29 is led between a pair of wheels with high- friction arranged as a so-called capstan drive (see below). The wheels are counter-rotating and driven at a steady speed, corresponding to and/or adapted the speed of the sawing machine 8, or constant torque/force. Between the wheels of a wheel pair thus propulsion for the duct 29 is accomplished. The constant torque/tension is set just below the torque/tension needed to pull the duct/cable 29. If the torque/tension is set even higher the feeding device 24 would pull the duct/cable 29 at higher speed than the machine 8 is moving forward, thereby creating a big mess of ducts/cables 29. As an alternative to the unique set of wheels for each duct 29, two counter rotating rollers with high friction can be used. All ducts 29 of the same dimension are, in parallel, led between the two counter-rotating rollers and will thus have propulsion to compensate for friction.

The feeding device 24 is located between the drums 28 on the trailer 27 and the stabilizing device 13 on the sawing machine 8. For location case 1 above, where the marking is done in connection with the installation, the feeding device 24 may be combined and assembled together with the marking device 23 and placed either on the trailer 27 or on the sawing machine 8. A sensor that detects the speed of the trailer 27/sawing machine 8 and controls the feeding speed of the feeding device 24 and thereby stops feeding and marking and when the trailer 27/sawing machine 8 stops. Alternatively, if constant torque/force is used, no sensor is needed. Propulsion power is in this case adjusted to a value not greater than the frictional force and therefore the propulsion stops automatically when the trailer 27/sawing machine 8 stops.

Duct guiding device

Between the drums 28 on the trailer 27 and the stabilizing device 13 a duct guiding device 30 may be arranged which ensures that the ducts 29 are guided into the stabilizing device 13. This duct guiding 30 device may have various designs but must have the following main functions: it must change the direction of the ducts 29 so that the ducts reach the stabilizing device 13 in a near vertical direction. This must be controlled so that minimum allowed bend radius for the ducts 29 is not compromised. For location case 1 the duct guiding device 30 may be mounted after the marking device 23, or be split so that one part is arranged before the marking device 23 and another part arranged after.

Stabilizing device The stabilizing device 13 is mounted on the sawing machine 8 immediately behind the saw blade 14. It stabilizes the sides/walls of the micro trench 1 being sawn by the saw blade and ensures that each duct 29 is placed in the sawed trench 1 in a predefined and in advance known order. This means that the present method and system ensures that a certain duct 29 with a certain, by the method added marking, will be placed on a predetermined location in the trench 1. The stabilizing device 13 is also in an embodiment arranged to change the direction of the ducts 29 from a near vertical direction at ground level 10 to a near horizontal direction out from the stabilizing device 13. The stabilizing device 13 ensures that this change of direction is made with a bend radius not less than the minimum allowed bend radius for the ducts 29 used according to an embodiment of the invention.

Depending on the width of the micro trench 1 and the diameter of the ducts 29, the stabilizing device 13 may be designed to output one, two or more ducts 29 at each height level. The principle is to always ensure that the duct 29 that is in line to be routed to the next destination is always located at the top level. Gradually, as the sawing machine 8 progresses (moves forward in operation), the number of ducts 29 in the main trench 1 decreases when ducts 29 one by one is routed to their destinations. The decrease is thus from the top and down and at the end there is only the duct 29 that from the beginning was in the bottom of the micro trench 1 left.

In an embodiment of the invention, the shape of the stabilizing device 13 closest to the saw blade is complementary or near complementary to the shape of the saw blade. Hence, the risk of collapsing micro trench is even more reduced with this embodiment. Gaiter

Between the duct guiding device and the stabilizing device 13 there may be a seal in the form of a gaiter 25 made of rubber, leather or any other suitable material. This seal prevents gravel and stones to fall into the channels of the stabilizing device 13 and damaging the ducts 29 to be installed in the trench 1.

Direct installation of fibre optic cables and/or electrical cables without ducts

Electrical cables 29 and fibre optic cables 29 may be installed directly without ducts 29. This installation can be made with exactly the same installation method as described above. Therefore, what was said above regarding the installation of ducts 29 also applies for fibre optic cables 29 or power cables 29, installed using the same method.

Capstan drive is used on tape recorders to feed the tape at a steady rate. The tape is fed between a counter-rotating pair of wheels. Just as with counter-rotating rollers in a mangle, but where the rollers have been replaced by wheels.

Field Client for real time documentation

The sawing machine 8 can further be equipped with a computer and software that give and collects information about the installation of the ducts/cables in the micro trench.

Work Orders (WO), created by the planner and designer of micro trenching, ducts, and communication networks, can be loaded into the software Client, running on a rugged field computer installed on the trenching machine.

One or more GPS receivers on the trenching machine continuously track the position and heading in real time. As the machine makes progress, the map moves in the map view of the client so the machine is always centered in the view, allowing the operator to monitor and steer it in line with the designed and planned trenching path displayed in the map view.

The information system requires corrections from a reference network or a single reference station near the work site, to provide needed atmospheric correction to reach high accuracy positioning. The position (e.g. in x and y position; or in x, y and z position) of the machine is defined to 1-2 cm and the height to 3 cm in good conditions. In addition, a positioning unit sends out heading information which comprises information about the heading in relation to north.

The micro trench is continuously digitized and stored within the WO. Whenever needed, the operator can, directly from within the software Client, sync the WO and its digitized information back via the Internet to the information system, making it available for all other users.

At the start of a micro trench, the software Client can instruct the operator, e.g. via a display or audio instructions, in what order to load the ducts in the stabilizing device. As micro trenching progresses, the client can tell the operator when to take out a specific duct to a (previous trenched) branch.

The field computer can be detachable arranged from the machine 8 and mounted on a "hands- free" operator harness, or onto a rod with a GPS receiver to manually mark out infrastructure on the ground, or to digitize locations of wells, splicing points, etc. This data can then be synced back via the Internet to the information system. The one or more GPS receivers connect to the field computer e.g. via a Bluetooth connection. If mobile data is unavailable, the Inside Link Client and its GPS receivers can work "off-line", with corrections applied later.

Fig. 5 shows a flow chart of a method according to an embodiment of the present invention. The method comprises the steps of:

guiding 202 said ducts/cables 29 from said at least one drum 28 to said stabilizing device 13;

marking 204 each of said ducts/cables 29 so that each of said duct/cable is given a unique identity;

installing 206 said marked ducts/cables 29 in said micro trench 1 based on said unique identity.

In an embodiment of the method further comprises the step of:

routing said ducts/cables 29 to their final destinations based on said unique identity.

Fig. 6, 7 and 8 schematically shows a cross section of an area in which the ducts/cables 29 are placed in a micro trench 1. The area is a three dimensional region of a typical roadway or pavement area, wherein the area comprises a first layer LI being a surface layer such as asphalt or concrete, and a second layer L2 being a bearing layer for the first layer LI and usually consisting of gravel, stones, sand and earth. The second layer L2 is naturally located below the first layer LI as shown in the figures.

The above mentioned sawing is made using a machine 8 arranged for sawing micro trenches 1 and placing ducts/cables 29 in micro trenches 1. The machine 8 comprises a saw blade 14 arranged for sawing a micro trench 1 in areas comprising a first layer LI and a second layer L2. Layer LI is a hard surface layer, such as asphalt or concrete, and the second layer L2 is a bearing layer for and located below the first layer LI . The bearing layer L2 normally consists of gravel, stones, sand and earth.

The sawing step involves: sawing the micro trench 1 through the first layer LI into the second layer L2, which means that the micro trench 1 is sawed as shown in Fig. 6 and 7. The micro trench 1 is sawed so deep that all ducts/cables 29 (minimum one) is placed in the micro trench 1 below the first layer LI . Using the present method all ducts/cables 29 for fibre optic networks will be placed deep enough so that they are safe if the surface layer LI is removed and/or replaced, e.g. when repairing the road. Then, the at least one duct 29 and/or a communication cable 29 is placed in the micro trench 1. The duct 29 may be a duct arranged to hold "air-blown fibre" (so called EPFU) or fibre cables 29. The duct/s 29 and/or the communication cable/s 29 are placed in the micro trench 1 so that they are entirely positioned below the first layer LI . Thereafter, the micro trench 1 is filled with a suitable filling material such as sand or preferably a material that is liquid and can be pumped into the micro trench and which material afterwards hardens and becomes resistant to compression forces such as aerated concrete or any other material with suitable properties. The micro trench 1 is filled with the filling material to a suitable level, and if needed the filling material is thereafter packed with a compactor that fits the width w of the micro trench.

Finally, the micro trench 1 is sealed using a sealing material, such as bitumen, in order to get a water tight sealing. If a water tight sealing is not needed, patching may also be made with cold asphalt which is a simple and cheap method of restoration. A suitable amount of cold asphalt is simply poured and scraped into the micro trench, and thereafter compacted to a smooth and hard surface. Any excess asphalt can then be collected and removed.

The sealing step may according to a preferred embodiment involve the steps of:

- sealing the micro trench 1 flush to the bottom of the first layer LI with a first sealing SI; - washing the sides of the micro trench 1 using a high pressure washer to remove any residue of sand from the asphalt/concrete edges; and

- sealing the micro trench 1 flush to a surface of the first layer LI with a second sealing S2. Fig. 8 shows the above described embodiment. The surface and the bottom of the first layer LI are indicated in Fig. 8. In order to obtain a sealed repair with high adhesion it is recommended to pour hot bitumen or bitumen mix when sealing the micro trench. However, other material such as concrete or polymer modified asphalt will work.

The first sealing S 1 is put down to seal the micro trench 1 substantially flush with the bottom of the first layer LI so that the micro trench 1 can be cleaned with a high-pressure washer to remove any residue of sand from the asphalt/concrete edges. After washing, the micro trench 1 may be dried and pre-heated using a propane burner and finally, the micro trench is filled flush with the top surface of the first layer LI using a suitable sealant such as a hot crack sealant based on bitumen.

The present invention also relates to at least the following further embodiments. Al . A system comprising a machine (8) and devices for installation of ducts/cables (29) in micro trenches (1); said machine (8) being arranged for sawing micro trenches (1) and placing ducts/cables (29) in micro trenches (1) in a continuous process; said machine (8) comprising a saw blade (14) and a stabilizing device (13); said stabilizing device (13) being arranged on said machine (8) directly behind said saw blade (14); said stabilizing device (13) being arranged to stabilise the sides/walls of said micro trench (1); said stabilizing device (13) comprising guiding means (17) for guiding and changing direction of said ducts/cables (29) from a mainly vertical direction at ground level (10) to a mainly horizontal direction out from said stabilizing device (13), without compromising minimum allowed bending radius of said ducts/cables (29); said guiding means (17) being arranged to guide each of said ducts/cables (29) into a predetermined relative position in said micro trench (1); said machine (8) is arranged to pull a trailer (27) arranged with holders for drums (28) for said ducts/cables (29), said installation further comprising the steps:

• marking each of said ducts/cables (29) in a marking device (23) using colour, text or in any other way so that each duct/cable 29 is given a unique and identifiable identity in said micro trench ( 1 ) ;

• guiding said ducts/cables (29) from said drums (28) on said trailer (27) to said stabilizing device (13) via duct guiding devices;

• installation of said ducts/cables (29), each marked with a unique identity, in said micro trench (1) with the aid of said guiding means (17) in said stabilizing device (13), thereby guiding said ducts/cables (29) to enter said micro trench (1) in predetermined order;

• said installation finally comprising the step of routing said ducts/cables (29) to their predetermined final destinations based on said duct's/cable's (29) unique identity.

A2. Machine (8) and devices according to Al, wherein said unique identity is added to each of said ducts/cables (29) by said marking device (23) in connection with a re-spooling of unmarked ducts/cables (29) from storage drums (20) to marked ducts/cables (29) on drums (28) which later will be placed on said holders on said trailer (27).

A3. Machine (8) and devices according to Al or A2, wherein said unique identity is added to each of said ducts/cables (29) by said marking device (23) located between said drums (28) on said trailer (27) and said stabilizing device (13) on said machine (8). A4. Machine (8) and devices according to any of A1-A3, further comprising a gaiter (25) arranged to prevent gravel and/or stones entering said stabilizing device (13).

A5. Machine (8) and devices according to any of A1-A4, wherein said marking device (23) comprises a laser providing a controlled laser beam; wherein said laser beam is deflected in a direction perpendicular to the motion of said ducts/cables (29).

A6. Machine (8) and devices according to any of A1-A5, wherein said marking device (23) comprises a wheel/wheels that somewhere along the periphery has heated stencils that melts said unique marking onto each said duct/cable (29). The unique marking are placed on each duct/cable (29) at distances equal to the circumference of said wheel.

A7. Machine (8) and devices according to any of A1-A6, wherein said marking device (23) comprises a device that melts portions of coloured plastic films onto said ducts/cables (29) either with unique colours for each said duct/cable (29) and/or a unique pattern, for example a unique text string for each said duct/cable (29).

A8. Machine (8) and devices according to any of A1-A7, wherein said trailer (27) or said sawing machine (8) is arranged with a meter device (21) in order to measure the installed length of each said duct/cable (29). A9. Machine (8) and devices according to A8, wherein said meter device (21) controls a cutting device (22) that automatically cuts each said duct/cable (29) at a for each said duct/cable (29) predetermined length.

AlO. Machine (8) and devices according to any of A1-A9, wherein said machine (8) or said trailer (27) is arranged with a feeding device (24) for said ducts/cables (29); wherein said feeding device (24) is arranged to pull said ducts/cables (29), thereby at least partially compensating for the friction of said ducts/cables (29) and said drums (28); said feeding device (24) being arranged before said stabilizing device (13).

Al 1. Machine (8) and devices according to AlO, wherein said feeding device (24) comprises a number of pairs of counterrotating wheels between which each of said ducts/cables (29) are led; said pairs of wheels are driven at a steady speed, corresponding to the speed of said machine (8) or alternatively driven with a constant torque/tension.

A12 Machine (8) and devices according to Al 1, wherein said pairs of counterrotating wheels are replaced by pairs of counterrotating rollers, each pair arranged to pull one or more of said ducts/cables (29).

A13. Machine (8) and devices according to AlO, Al l or A12, wherein said feeding device (24) is arranged with a sensor sensing said trailer's (27) or said sawing machine's (8) motion and stops said pulling and said marking when said trailer (27) or said sawing machine (8) stops.

A14. Machine (8) and devices according to any of A1-A13, wherein said drum holders on said trailer (27) has a maximum capacity of holding up to 25 drums (28); and/or said drum holders may further be able to be folded down in order to ease transportation. A15. Machine (8) and devices according to any of A1-A14, wherein said feeding device (24) and said marking device (23) are arranged as a single device.