GB2627007A - Cable laying apparatus - Google Patents

Abstract

Apparatus 2 for laying a cable 22 in a microtrench in a surface having a surface course, a base course and an underlying sub-base. The apparatus comprises a rotary cutting wheel 10 adapted to cut a micro trench in surface and to fragment the cut material from the surface and base courses to aggregate. A cable system feeds cable 22 from a cable reel 20 into the micro trench and to lay it along the bottom of the micro trench. A vacuum system 18 is arranged to remove the materials cut and fragmented in cutting the micro trench and to convey these to a sorter (32, Fig 2c) adapted to separate and aggregate from other material removed from the micro trench. A conveyor is adapted to convey this aggregate to a pugmill (34, Fig 2c) which is arranged to mix the aggregate with a flowable, setting material and to convey this mixture of aggregate and flowable, setting material to a dispenser (38, Fig 2c) adapted to dispense this mixture over the cable laid on the bottom of the micro trench. The apparatus is mounted in a self-propelled vehicle less than 1.2m in width and less than 2m in length.

Description

Cable Laying Apparatus

FIELD OF THE INVENTION

The present invention relates to apparatus for laying cables in trenches cut into the ground, particularly but not exclusively microtrenches cut into an asphalt or cement surface.

BACKGROUND ART

The installation of sub-surface utilities is a tightly regulated procedure, particularly in towns and cities where many different utilities are located underground in the only readily available area, which is roadways. The installation of utilities in roadways is usually a large-scale proceeding, requiring the roadway to be at least temporarily closed, leading to disruption of traffic and inconvenience to road users. Moreover, the machinery used in such works is usually large in size and heavy in weight, so much so that it is quite unsuited for operating on pavements (or sidewalks), which are, often too narrow to accommodate the machinery, and are seldom designed to take the weight of this machinery. Accordingly, many utilities are installed under the road surface, but relatively few under the pavement. In addition, the increasing demand for faster broadband coupled with an increasing desire to work online from home has led to a need to connect more homes to fast, fibre optic broadband in an expeditious manner, whilst minimising traffic disruption or other inconvenience. Accordingly the use of "microtrenching" is being considered as a way around this: for the purposes of this document a microtrench is a trench of no more than 60mrn in width, and a depth of at least 150mm (both of these dimensions are considerably smaller than the trenches cut for installing conventional utilities) but no more than about 250mm and is suitable for installing smaller utilities such as fibre optic cables. To date, microtrenches have been cut and cables installed using several, separate machines, using the same techniques as have been used for many years in installing, utilities in roadways: first a microtrench is cut, and the material cut out to form the microtrench removed and disposed of. Then a sublayer of granular or aggregate material is laid, the cable (or cables) is laid in the bottom of the trench and a layer of infill material such as asphalt is laid on top of the cable to fill the microtrench up to a point just below the surface of the surrounding pavement and to bind with the material forming the edges of the trench; this infill material is usually coloured (or the topmost part of it), so as to help prevent any later work to the pavement surface damaging the cable beneath (fibre optic cables being less robust than many other forms of cable). Finally, a surface infill material such as asphalt is added in such a manner as to blend in the top of the filled microtrench with the surrounding pavement surface. Even with the reduction in size of a microtrench compared to a conventional utilities trench, conventional microtrenching is a lengthy process and, although it can be carried out without interfering too much with traffic on the road by being located along the kerbline at the edge of the road, or an the pavement, it means closing off stretches of pavement, which inconveniences pedestrians. Moreover, the conventional techniques of installing utilities is labour intensive, with different machines being operated by different people, and requires costly raw materials such as infill materials to be provided. Consequently there is a need for new ways of laying cables in microtrenches.

SUMMARY OF THE INVENTION

The present invention therefore provides apparatus for laying a cable in a microtrench in a surface having a surface course, a base course and an underlying sub-base (usually soil, or subsoil), the apparatus comprising a rotary cutting wheel adapted to cut a microtrench in the surface and to fragment the cut material from the surface and base courses into aggregate, a cable system for feeding at least one cable from at least one cable reel into the microtrench and to lay it along the bottom of the microtrench, a vacuum system arranged to remove the materials cut and fragmented in cutting the microtrench and to convey these to a sorter adapted to separate the aggregate from other material removed from the microtrench, a conveyor adapted to convey this aggregate to a pugmill which is arranged to mix the aggregate with a flowable, setting material and to convey this mixture of aggregate and flowable, setting material to a dispenser adapted to dispense this mixture over the cable laid on the bottom of the microtrench, in which the apparatus is mounted in a self-propelled vehicle less than 1.2m in width and less than 2m in length.

With such an arrangement, the vehicle is small enough to be driven along a pavement and carry out the trench cutting, cable laying and infilling processes significantly faster than conventional techniques allow, meaning less inconvenience to pedestrians and road traffic.

Because the apparatus is contained in a single, relatively small vehicle it can be operated by a single operator and it is small and lightweight enough to be used on typical pavements. Because it recycles materials cut to form the trench as part of the infill material it requires less new material to be provided than for conventional techniques, which is commercially and environmentally beneficial. The flowable, setting material may be a cement, or a resin material, and may contain a filler such as sand and/or a colourant (in which case there would be a source of colourant, and means to introduce the colourant into the mixture of aggregate arid flowable, setting material). There may be at least two compartments for containing constituents of the flowable, setting material, such as cement and water.

In this document, the directions forward and sideways and the like are used in relation to the normal, forwards direction of the vehicle in use; likewise the terms longitudinal and transverse and the like are employed relative to the vehicle and its forward direction of movement, and all these and similar terms used herein should be interpreted in this manner.

The vehicle has a lengthwise axis along which it is driven in use, and the conveyor and pugrnill preferably both operate along opposed longitudinal axes, both of which are preferably aligned with the lengthwise axis of the vehicle. Such an arrangement allows the length and, more importantly, the width of the vehicle to be kept as small as possible, which is a requirement for the vehicle to be usable on most pavements. It also allows the vehicle to be used on the roadway, to lay a cable in a microtrench adjacent the edge of the roadway (i.e. at the kerb), without blocking an entire carriageway or a significant part of the width of the roadway. A short, narrow vehicle is also inherently easier to manoeuvre, so as to lay cables around corners, for example.

The rotary cutting wheel may be mounted so as to be movable transversely with respect to the vehicle; this allows the vehicle to move parallel to a kerb or wall, whilst, keeping the microtrench close up against the kerb/wall. The rotary cutting wheel can be mounted so as to be movable about a vertical axis; this allows the course of the microtrench to be varied easily without necessarily requiring the vehicle to be diverted; this could be helpful if there is some obstacle which the microtrench has to go around, such as a drain. The rotary cutting wheel may be mounted so as to be movable vertically, so as to adjust the depth to which the microtrench is dug.

The dispenser may be arranged with two dispensing rapertures disposed longitudinally with respect to the vehicle and either side of the cable as it is fed into the microtrench. Such an arrangement allows a proportion of the aggregate to be laid in the base of the microtrench before the cable is laid on top of it, so as to provide a "bed" for the cable; this aggregate may be mixed with the flowable, setting material so that the bed solidifies, or the aggregate may be allowed to remain as a granular material, so as to allow for small movements in the subsoil.

Preferably there is a control system adapted to control the rotary cutting wheel, the vacuum system, the cable system, the conveyor, the pug mill, the dispenser and the speed of movement of the vehicle. This may be in the form of a suitably programmed cpu or processor, and there may be a control panel, keyboard or other interface system mounted to the vehicle to allow the control system to actuate and to give alternative operating instructions to the apparatus. The control system may be adapted to be controlled by a person remotely from the vehicle; this remote control could be effected by an umbilical to a handheld control panel, or there may be a wireless communication system. Sensors such as cameras could be provided to enhance control of the apparatus (such as a camera looking into the microtrench, and/or cameras looking in the direction of movement of the vehicle and around the vehicle).

The vehicle is preferably tracked; this allows the vehicle to be stable in use, and for its weight to be *distributed evenly and over a large surface, thus minimising damage to surrounding roadway/path areas. The sorter may take the form of a grading grate, which can be arranged to vibrate; this allows the crushed material removed from the surface and base courses to be separated largely by gravity from the sub-base. The sub-base material may be stored in a part of the vehicle, or it could be deposited at the side of the vehicle, to be swept up or cleared away separately. ;Suitably, the apparatus, or the apparatus and the vehicle, is powered electrically. This reduces engine noise and thus the disturbance operation of the apparatus might give rise to. ;The power may be provided by a battery pack, an array of photovoltaic cells, and/or an umbilical from the mains or a separate generator (such an umbilical might also conduct a supply of water to the apparatus, removing the need for it to carry its own supply), Drive motors for the vehicle can be small enough to be wheelhub mounted, and variably controlled to help in manoeuvring the vehicle. ;BRIEF DESCRIPTION OF THE DRAWINGS ;The invention will now be described by way of example and with reference to the accompanying figures, in which; Figure 1 is a schematic perspective view of an embodiment of an apparatus in accordance with the invention, and Figures 2(a) to 2(d) are schematic illustrations of the apparatus of Figure 1, being a side elevation, a plan view, a side view in cross-section and a front view respectively. ;DETAILED DESCRIPTION OF THE EMBODIMENTS ;Figure 1 and Figure 2a show a combined microtrench digging and cable-laying apparatus 2 in the form of a tracked vehicle having two roller tracks 4. The vehicle has a chassis 6, a body compartment 8 and a rotary cutting wheel 10 mounted to an arm 12. The cutting wheel 10 is a commercially available type of toothed cutter, such as that sold by Rock.Zone GmbH of Germany under the trade mark Rockwheel. The upper part of cutting wheel 10 is covered by a shroud 14 which is connected by a hose 16 to a vacuum unit 18. A cable reel 20 is mounted to the front of the main body compartment and feeds out a cable 22. ;Moving to the plan view of Figure 2b, the body compartment 8 is divided internally into separate compartments for water 24, sand 25, cement 26 and removed aggregate 28. There is also a utility compartment 30 which contains batteries, the cable reel drive motor, the control system for operating the vehicle tracks 4 via wheelhub-mounted electric motors, the cutting wheel 10, the arm 12, the vacuum unit 18 and the sorting, conveying, mixing and dispensing processes described below; this control system is a suitably programmed processor. ;As can be seen in Figure 2c, which is a cross-sectional side view along the longitudinal centre line, of the vehicle 2, beneath the vacuum unit 18 is a sorting grate 32 which is arranged so as to separate out the larger granular pieces of material cut by the cutting wheel from the smaller pieces, ideally so as to remove all the soil and clay from the broken/crushed asphalt or other material; the latter material then falls into or is vibrated towards and into the aggregate compartment 28, whilst the former is diverted either into another compartment or is ejected from the side of the apparatus to be cleared away later. Running underneath the aggregate, cement and water compartments are two conveyer belts (not shown) onto one of which a measured amount of aggregate falls. Cement and sand are allowed to fall under gravity into hoppers towards the front of the apparatus and closely in front of the second conveyor belt from where they are scooped up by uplifters on the second conveyor belt to fall onto the second conveyor belt. Aggregate, cement and sand are conveyed rearwardly, to the end of the conveyor belt where they fall off and into a pugmill mixing chamber 34; this has a rotating mixing augur 36 which mixes the aggregate, cement, sand and water to form a paste, whilst conveying this mixture forwards towards two dispensers 38 (only one is shown, to the rear of the cable 22, the other is forward of the cable 22). Towards the rearward end of each conveyor belt is an infrared sensor meter device (not shown) which measures the water content of the aggregate material on the first conveyor belt and the water content of the sand and cement on the second conveyor belt. These devices communicate the measured water contents to the control system, which determines the overall water content, calculates the amount of water to be added to the final mixture, and actuates valves (not shown) to introduce the appropriate amount of water into the mixture in the pugmill mixing chamber 34. ;Figure 2d shows how much lateral distance there is between the cutting wheel 10 and the two tracks 4; it will be understood that the arm 12 (not visible in this drawing) is mounted at its distal end, away from the wheel 10, so as to pivot about both the lateral horizontal axis and a vertical axis. This allows the wheel 10 to be raised or lowered, to cut a trench of a lesser or greater depth, and to pivot left and right, to 'steer' the microtrench being cut. The end of the arm 12 at the pivot point is also arranged to move transversely, so as to move the wheel 10 towards one or other of the tracks 4. ;The operation of the apparatus will now be described. The cutting wheel 10 is started to rotate by an electric motor (not shown) with the arm 12 in a raised position; the arm 12 is slowly lowered and cuts a hole into the underlying surface to the desired depth. The cutting wheel 10 rotates in the direction shown by the arrow in Figure 2c, so that the lowermost edge of the wheel 10 is moving in the same direction as the apparatus is driven, so as to raise cut material into the hose 16 at the front of the vehicle. Once this depth of cut has been reached, the vehicle can begin to move forwards, as it does so the vacuum unit 18 starts and sucks up the debris created by the cutting wheel 10 into the shroud 14, along the hose 16 and eventually deposits this on the sorting grate 32. As the vehicle moves forward, the cable reel 20 feeds cable 22 into the microtrench, laying it either onto the underlying surface, or onto a layer of aggregate left behind because it is too big and heavy to be drawn upwards by the vacuum unit 18, or dispensed by the apparatus after mixing. Meanwhile, metered amounts of aggregate, cement and sand are allowed to drop onto the conveyors and conveyed to the rear of the vehicle, where they drop into the pugmill 34, are thoroughly mixed, and carried forwardly relative to the vehicle 2 to be dispensed downwardly into the microtrench; the appropriate amount of water is added to the materials in the pugmill 34 some distance away from its rearward end, so that the solid materials have been at least partially mixed together before the water is added (the "appropriate amount" of water is enough to ensure that the final mixture as it is dispensed into the microtrench is flowable enough to fill the microtrench around the cable with no voids, but is not too "runny", or liquid, so as to fail to fill the microtrench to the intended depth). In the microtrench the cement sets, bonding the mixture to the sides of the microtrench. The control unit can be, programmed to direct the dispensing of mixed aggregate and sand/cement relative to the forward speed of the vehicle so that the depth of aggregate and sand/cement fills the microtrench to just below the surrounding surface, ready for this to be "smoothed over" with a layer of asphalt or the like. The control unit also directs the cable laying motor to lay cable at the same speed as the vehicle speed. The controlling factor for the operation of the apparatus is the forward speed of the vehicle, which is determined by the nature of the material the microtrench is being cut through and the, depth of the microtrench. This is, preferably monitored by an operator, who can adjust the vehicle speed as well as other apparatus characteristics (e.g. wheel position, vacuum strength, amounts of cement and water to add to the aggregate) as appropriate, or these may be automatic, and are pre-programmed into the control system. It is preferable that the control system controls the amount of water to be'added so that it is "appropriate", although there should be an override in case the operator considers that the dispensed material is either too "runny", or liquid, or if it is not sufficiently flowable to properly fill the microtrench. The speeds of the conveyor and the pugmill are controlled by the control system according to the depth of cut and vehicle speed, and can be linked so as to transfer material at the same rate in operation, thus retaining a measure of even weight distribution. Because the apparatus reuses materials cut to create the microtrench this reduces the amount of new material which needs to be provided, which is environmentally beneficial, it also means that the apparatus 2 can run for longer, and cut a longer trench/lay a greater length of cable, before the water, sand and/or cement compartments need to be replenished or more cable added to the reel. ;It will of course be understood that many variations may be made to the above-described embodiment without departing from the scope of the present invention. For example, solar panels could be mounted to the exterior of the chassis, there may be more than one cable reel, so that several cables and/or cables of different types can be laid at the same time There may be a control panel mounted to the outside of the vehicle for an operator* to interacts with the control system, and there may be a wireless transmitter/receiver fitted to allow remote control of the apparatus. Depending on the nature of the materials forming the surface course, base course and underlying sub-base there may be no need for sand to be added to the mixture dispensed to fill the microtrench, in which case the sand compartment might be used to contain more cement.

Where different variations or alternative arrangements are described above, it should be understood that embodiments of the invention may incorporate such variations and/or alternatives in any suitable combination.

Claims (14)

1. CLAIMS1. Apparatus for laying a cable, in a microtrench in a surface having a surface course, a base course and an underlying sub-base, the apparatus comprising a rotary cutting wheel adapted to cut a microtrench in the surface and to fragment the cut material from the surface and base courses into aggregate, a cable system for feeding at least one cable from at least one cable reel into the microtrench and to lay it along the bottom of the microtrench, a vacuum system arranged to remove the materials cut and fragmented in cutting the microtrench and to convey these to a sorter adapted to separate the aggregate from other material removed from the microtrench, at least one conveyor adapted to convey this aggregate to a pugmill which is arranged to mix the aggregate with a flowable, setting material and to convey this mixture of aggregate and flowable, setting material to a dispenser adapted to dispense this mixture over the cable laid on the bottom of the rnicrotrench, in which the apparatus is mounted in a self-propelled vehicle less than 1.2m in width and less than 2m in length.
2. 2. Apparatus according to Claim 1, in which the vehicle has a lengthwise axis along which it is driven in use, and in which the conveyor and pugmill both operate along longitudinal axes which are aligned with the lengthwise axis of the vehicle and in opposite directions.
3. 3. Apparatus according to Claim 1 or Claim 2, in which the rotary cutting wheel is mounted so as to be movable transversely with respect to the vehicle.
4. 4. Apparatus according to any of Claims 1 to 3, in which the rotary cutting wheel is mounted so as to be movable about a vertical axis.
5. 5. Apparatus according to any preceding claim, in which the dispenser is arranged with two dispensing apertures disposed longitudinally with respect to the vehicle and either side of the cable, as it is fed into the microtrench.
6. 6. Apparatus according to any preceding claim, further comprising at least two compartments for containing constituents of the flowable, setting material.
7. 7. Apparatus according to any preceding claim, comprising a control system adapted to control the rotary cutting wheel, the vacuum system, the cable system, the conveyor, the pug mill, the dispenser and the speed of movement of the vehicle.
8. 8. Apparatus according to Claim 7, in which the control system is adapted to be controlled by a person remotely from the vehicle.
9. 9. Apparatus according to any preceding claim, in which the vehicle is tracked.
10. 10. Apparatus according to any preceding claim, further comprising a source of colourant, and means to introduce the colourant into the mixture of aggregate and flovvable, setting material.
11. 11. Apparatus according to any preceding claim, in which the sorter is in the form of a grading grate.
12. 12. Apparatus according to any preceding claim, in which the apparatus, or the apparatus and the vehicle, is powered electrically.
13. 13. Apparatus according to Claim 12, further comprising at least one of a battery pack and an array of photovoltaic cells.
14. 14. Apparatus according to any preceding claim, further comprising an infrared sensor to measure the water content of the aggregate and of the flowable setting material.