FR2766634A1 - Wrapping of protective strip round bundle of cables buried in trench - Google Patents

Abstract

The cable is laid from a mobile machine that carries a reserve (4) of the cable (2) to be laid, a reserve (5) of the protective strip(3), and delivery mechanisms for cable and strip. The protective strip is wrapped (6) over the cable as it is advanced, with the longitudinal edges of the strip joined by a machine (7) after the cable has been wrapped.

Description

The present invention relates to a device for coating an elongated object, intended to be buried in the ground, with at least one external protective coating in the form of a strip.

The terms "elongated object" may especially designate a cable, a pipe, a pipe, a set of each of them, or the like. In the particular application which will be described below, the elongated object relates to a set of flexible electric cables, used for high and medium voltage lines, but it goes without saying that they could be optical cables, of pipes for transporting a fluid, etc., without departing from the scope of the invention.

We know that, to bury an electric cable (or a set of electric cables) in the ground, we use for example a motorized machine, provided with a slicer wheel whose peripheral cutting tools, following the rotation of the wheel and the advance of the machine, gradually realize in the ground a trench having dimensions (depth, width) appropriate. Also, before depositing the cable in the bottom of the trench and to avoid damaging the outer insulating and protective sheath of said cables by rocks or protruding stones and the consequences that this would entail (crack initiations, ...), the bottom of the trench is filled with a powdery, protective material, such as sand, to a desired thickness. Then, the cable is laid in the trench, so that the latter rests on sand to be gradually coated with a layer or a protective sand bed, preventing protruding edges thus coming directly into contact with its outer sheath , when the trench is filled.

Although this production process gives satisfactory results, it nevertheless has drawbacks mainly as regards the logistics to be implemented.

Indeed, it is necessary to provide a large amount of sand, always available (for example, about 130 kilograms of sand per linear meter of cable laid), otherwise the progress of the work will be interrupted.

This implies the presence of a plurality of trucks to feed the hopper delivering the sand into the trench, these trucks being required to make many more trips back and forth between the sand storage site and the site of the work in progress.

It therefore appears that this laying process requires a heavy and costly infrastructure to coordinate all the different operations and ensure the smooth running of the site, which is not always possible to achieve.

The object of the present invention is to remedy these drawbacks.

To this end, it relates to a device for coating an elongated object, such as a cable, pipe, set of cables or the like, intended to be buried in the ground, by at least one external protective coating in the form of a strip, and the device is remarkable in that it comprises - a reserve of said elongated object to be coated - a reserve of said protective coating, said object
elongated and said protective covering being able to
be subjected to a forward movement - equipment for gradually folding said covering
of protection around said elongated object as and
measure of the advance of these, so that the edges
longitudinal of said covering are at least contiguous
and - equipment for fixing said covering folded around
said elongated object to obtain, at the exit of said team
ment, an end product consisting of said object and said
coating and ready to be buried in the ground.

Thus, thanks to the invention, the elongated object (cable or set of cables) is first coated with the protective coating and then the final product, consisting of the object and the coating, is then deposited in the trench, on its bottom, to be then covered with the excavated material produced during the digging of the trench. Consequently, the device overcomes the logistical problems inherent in supplying and depositing sand in the trench, which makes it possible to increase the length of cable laid per day and to reduce the cost of laying.

Advantageously, said equipment for folding the coating can be in the form of a gutter with evolving cross sections, the inlet of said gutter being flat to receive said coating from the reserve, while the outlet of said gutter is substantially circular. so that the coating surrounds said elongated object previously disposed thereon. Thus, the covering strip, initially flat, is gradually folded longitudinally to completely envelop the cables leaving the equipment.

For example, said gutter comprises a set of rods connected transversely to each other by cradles and shaped to evolve, at the entrance to the gutter, from a flat section towards a circular section at the outlet of the gutter.

In addition, between said coating reserve and said folding equipment, there is provided at least one housing with transverse, parallel rollers, which receives said coating strip to direct it towards said equipment, and a guide is attached to said housing to direct and depositing said elongated object on said covering, substantially in the middle thereof. Thus, the covering strip and the cable assembly are perfectly guided one over the other, in the direction of the equipment.

Preferably, said equipment for fixing said folded covering around said elongated object is defined by a tape machine comprising - a rotary disc provided with a central opening
through which said final product can pass - a plurality of spindles mounted equally
angularly distributed on said disc, around said
opening ; and - coils mounted respectively on said spindles and
of which the wires, as a result of the rotation of the disc and the
product advance movement, surround and fix heli
coidally the external coating on said elongated object.

As will be specified below, it is advantageous that the tension of said wires is between 10 and 50 N.

Furthermore, a sensor wheel is advantageously provided on said folding equipment, said wheel being in contact with the protective coating and connected to the drive motor of said disc of the banding machine. Thus, the speed of rotation of the banding machine and the movement of advance of the coating are brought into relation by the sensor wheel, so that the latter can, for example, detect an unexpected stop of the rotation of the banding machine.

In addition, between the two devices, there is a removable cage with a circular cross section, inside which said folded covering is kept in place around the elongated object until the action of said fixing device, that is to say, the tightening wires of the banding machine.

For example, said reserves are constituted by drums around which are respectively wound said elongated object and said protective strip coating. At the outlet of the fixing equipment, a reserve can be provided around which said final product obtained is wound.

The invention also relates to a motorized vehicle for digging trenches intended for laying elongated objects, of the type comprising a cutting wheel or the like. Advantageously, it further comprises at least one reserve of final product consisting of said elongated object and of said external protective coating, and obtained by the device defined above. The product is then deposited directly into the trench after it has been made by the slicer wheel.

The invention also relates to a mechanized assembly for digging trenches and laying elongated objects in the trench, of the type comprising a motorized machine provided with a cutting wheel or the like. The assembly is remarkable in that it comprises a device as defined above and shaped as a mobile unit for laying, in the bottom of said trench, the final product obtained consisting of said elongated object and said external protective coating.

The figures of the appended drawing will make it clear how the invention can be implemented. In these figures, identical references designate similar elements.

FIG. 1 represents a plan view of an exemplary embodiment of the device according to the invention.

Figure 2 shows the guide arrangement of the protective covering and cables towards the folding equipment.

FIG. 3 is a cross section of said arrangement along line III-III of FIG. 2.

FIG. 4 illustrates an exemplary embodiment of said equipment for folding the covering around the cables.

Figures 5, 6 and 7 are cross sections of said equipment, along lines V-V, VI-VI and VII-VII of Figure 4.

FIG. 8 shows the arrangement for holding the covering wound around the cables, located between the folding and fixing equipment.

FIG. 9 is a cross section of said arrangement along line IX-IX of FIG. 8.

FIG. 10 is a partial perspective view of said equipment for fixing the covering to the cables.

Figure 11 is a schematic cross section of said fixing equipment.

FIG. 12 shows a motorized machine for digging and laying elongated objects in a trench, equipped with a reserve of final product obtained by said device.

FIG. 13 shows a mechanized assembly comprising a motorized vehicle with a cutting wheel and the device of the invention in the form of a mobile unit.

Figure 14 is a cross section of a trench at the bottom of which is placed said final product from the device.

The device 1, shown in FIG. 1, is intended to coat an elongated object with an external protective coating, to then deposit the final product obtained, consisting of the elongated object and the coating, in the bottom of a trench, as we will see later.

The elongated object is for example a set of three interlaced electrical cables 2 for the electrical distribution of a current at high and medium voltage (approximately 20,000 volts), while the protective coating 3 is in the form of a strip flexible consisting for example of a double-walled textile envelope of synthetic material between which are disposed a needled pad of fibers such as polypropylene, and a particulate material, such as sand. A binder can also be added to the sand. Thus, such a coating contributes to ensuring, on the one hand, excellent mechanical resistance and, on the other hand, good thermal evacuation as a result of the electric current flowing in the cables. To completely surround this set of cables 2, the protective covering strip has a width of approximately 40 cm for a thickness of the order of 10 to 15 mm.

According to the invention, the device 1 comprises two respective reserves 4, 5 for the cable assembly 2 and the covering 3, an equipment 6 for gradually folding the covering around the cables 2 and an equipment 7 for fixing the covering 3 on the cable assembly 2.

More particularly, the reserves 4, 5 are defined by drums on which the cable assembly 2 and the protective covering strip 3 are wound respectively. The drums 4, 5 are mounted free in rotation around their respective axes 4A, 5A which are carried by supports 4B, 5B via bearings not shown. Preferably, the two drums are substantially arranged in the same longitudinal plane. Relative to the direction of production or advance (arrows F) of the final product P, the drum 4 carrying the cables 2 is located in front of the drum 5 carrying the coating 3, so that the cable assembly 2 is brought to the equipment coating 6.

To properly direct and guide the covering strip 3 towards the equipment 6, the device further comprises a series of two housings 8, 9 with cylindrical rollers 10, parallel, transverse in the direction of unwinding of the strip towards the equipment indicated by an arrow F. As shown in particular in Figure 2, the housing 8 is fixed, integral with a support 11, and is located in the direction of the equipment 6, while the other housing 9 with rollers is pivotally mounted on the housing 8 in front of the latter, around a hinge axis 12. The housing 9 is advantageously equipped with a sliding plate 13 which is applied to the winding of the covering strip 3 to hold the windings in place and guarantee a substantially tangential entry of the strip in the direction of the roller housings 8, 9, as a result of the progressive unwinding thereof. A guide 14 is also attached to the fixed casing 8 and, as shown in FIG. 3, it has an inverted U shape between the arms 14A from which the cable assembly 2 passes to be deposited on the covering strip 3, substantially in the middle of it. This guide 14 thus guarantees the correct positioning of the cables on the covering.

The equipment 6 for folding the protective covering 3 around the cable assembly 2 is in the form of a gutter 15 with evolving cross sections, as shown in FIGS. 4 to 7. In fact, it can be seen on the Figure 5, that the inlet 15A of the gutter defines a flat, horizontal cross section extending the roller housing 8 to ensure optimal transfer between them.

The cross section of the gutter gradually evolves to take a semi-circular shape substantially in the middle 15B of the length of the gutter, so that the protective covering strip 3 has a shape similar to this level of the gutter, as shown in the Figure 6. The gutter 15 ends, at its outlet 15C, by an approximately circular cross section whereby the longitudinal edges 3A of the protective covering strip meet to preferably overlap, one covering the other. , so that, at the exit of the gutter, the cable assembly 2 is completely surrounded by the protective coating 3, as shown in FIG. 7.

In a particular embodiment, the gutter 15 is obtained from rods 16 which are connected transversely to each other by cradles 17 and which are shaped so as to evolve from a flat section, at the entrance to the gutter 15, towards a substantially circular section at the outlet of the gutter. The cradles are also fixed to a support 18.

To keep in place the covering strip 3 folded around the cables 2, between the two pieces of equipment 6 and 7, the device 1 comprises a cage 19 situated in the extension of the outlet 15C of the gutter 15 and inside which progresses the cable cover assembly. For example, as shown in FIGS. 8 and 9, the cage 19 is carried by the support 18 of the equipment 6 and it has a cylindrical shape, of circular cross section.

It consists of three curved, articulated parts 19A which, in the closed position under the action of a spring 19B or the like combining two parts, enclose the covering 3 to keep it folded around the set of cables 2.

The cage 19 is for example made from parallel rods 19C, assembled together to form a circular cross section when closed.

The fastening equipment 7 for the folded covering 3 on the cable assembly 2, is partially shown in FIGS. 10 and 11, and it is a tape cutter 20 of a type known per se.

In particular, the banding machine 20 comprises a disc or plate 21 capable of being rotated by a hydraulic motor, not shown, of the device, and having a central opening 21A through which can pass, substantially perpendicular to the plane of the disc, the final product P obtained after fixing the covering 3 on the cables 2. The disc 21 is provided with a plurality of spindles 22 (six in number in this example) arranged on the disc in an equi-angularly distributed manner with respect to the others, around the central opening 21A. These spindles 22 are mutually parallel and, therefore, in the direction of advance F of the product, and they carry spools 23 of respective wire, mounted to rotate freely on these. The wires 23A from these coils pass through tension and guide mechanisms 24 associated with the coils, to be directed around and fixed to the external covering surrounding the cables, leaving the cage 19.

At the outlet of the tape-making machine, an equipment 25 is provided to guide the elongated product obtained P, according to an appropriate curvature, and which in particular comprises rollers 25A between and over which said product passes.

Furthermore, in FIGS. 1, 4 and 5, it can be seen that a wheel 26 equipped with a sensor 26A is mounted, by means of an arm 27, on the support 18 of the equipment for folding 6, so that its periphery 26B is in contact with the protective covering strip 3, in the vicinity of one of its longitudinal edges 3A. The axis of rotation of the wheel 26 is orthogonal to the direction of advance F of the cable covering assembly. The sensor wheel is connected to a solenoid valve of the rotary drive motor (not shown) of the banding machine 20, and in particular makes it possible to detect an unexpected stop of the rotating disc 21 of the banding machine.

The operation of the device according to the invention takes place as follows.

Before starting the device 1, the six wires 23A of the coils 23 are first knotted around the protective covering 3 enveloping the cables 2.

The end of the product P thus formed of the covering and of the cables is subjected, at the outlet of the banding machine 20, to a feed movement F having an appropriate speed, which causes the rotation of the drums mounted free in rotation and, therefore, the unwinding of the covering strip 3 and the cables 2, then the folding of the covering 3 around the cables by the equipment 6, to completely envelop them.

Simultaneously with the advancing movement above, a rotational movement is imparted to the disc 21 of the banding machine 20.

As a result of the combination of the movement in advance of the covering and of the cables and the movement of rotation of the disc and, therefore, of the spindles 22 around the assembly, the wires 23A are wound helically around the protective covering 3 to carry out a suitable tying or tying of the covering on the cables, as shown in FIGS. 10 and 11. At the exit from the banding machine, the final product P is obtained ready to be deposited and buried in a trench. The pitch between two consecutive wires can for example be between 10 to 50 mm, and the material used for the wires is advantageously a synthetic material such as a polyester, in particular for its resistance to creep.

Thus, the wires 23A exert on the covering 3 a clamping action which depends on the tension of said wires, imposed by the tensioning and guiding mechanisms 24. Preferably, the tension of the wires 23A is adjusted between 10 and 50 N.

Indeed, experience has shown that the tightening of the coating 3 then had a favorable double effect a) by the increase in the compressive stress
imposed on sand, the latter's resistance to
static and dynamic penetration is increased. This
effect results from rubbing sand; because of
internal friction, the shearing of the sand necessary to
penetration is proportional to the constraint of
sand containment; this confinement constraint
is directly increased by the tension of the threads
rolled helically around the protection b) tightening increases the compactness of the sand contained in the
protective coating and this density increase
results in increased conductivity
thermal of sand. According to Kersten's laws, the
conductivity increases exponentially as a function
density, a 15% increase in density
producing an increase in order conductivity
50%. Now, the tightening of the sand resulting from a tension
wires between 10 and 50 N has the effect of
density increase, depending on the nature of the sand,
in the range of 10 to 20%.

It therefore results from the two effects of tightening due to the tension of the wires 23A an improvement in the performance of the protective coating in the two areas where the performances are sought: mechanical protection and thermal conduction.

The final product obtained P can preferably be recovered on a receiving drum provided for this purpose. In this case, the laying of the product in the bottom of a trench can be carried out using a motorized machine intended for digging the trenches.

The motorized vehicle 28 shown in FIG. 12 is provided, at the rear, with a cutting wheel 29 carried by a movable, orientable assembly 30, linked to the chassis 31 of the vehicle. At the front of the latter, there is then provided the drum (reserve) 32 around which is wound the final product P ready to install. Thus, simultaneously with the digging of the trench T in the ground by the cutting tools 29A located at the periphery of the wheel 29, the product P is directly brought via guides 33 integral with the machine, towards the rear of this, then deposited on the bottom FD of the trench, downstream of the wheel. The weight of the product deposited on the bottom of the trench is sufficient to ensure the rotation of the reel and to unwind it, as a result of the advance of the machine 28.

The elongated, deposited product is then covered by the cuttings from the digging, without risk for the cables to be altered by protruding rocks or the like, thanks to the presence of the coating 3 forming a mattress or a protective envelope, and guaranteeing a adequate mechanical resistance and thermal evacuation.

In the embodiment illustrated in FIG. 1, the device 1 is in the form of a mobile unit, a chassis 1A carrying, via the respective supports 4B, 5B, 11, 18, the various drums and equipment. Rolling means 1B, such as tracks, are then associated with the chassis. In this case, as shown in FIG. 13, the mobile unit 1 is located for example in front of the motorized vehicle 28 whose trencher wheel 29 executes the trench T in the ground. Simultaneously with the digging, the device 1 produces, from the set of electric cables and the protective covering strip, the final product P which is brought to the rear of the trench to be deposited on its bottom FD.

The cross section of the trench, shown in Figure 14, shows the final product P deposited on its bottom, all of the electrical cables 2 being surrounded by the protective coating 3 and thus protected from the surrounding soil. A marking strip 34 is also unwound in the trench
T above said buried product.

For information, the protective coating 3 contains approximately 6 kilograms of sand per linear meter laid of product, while with the usual process of covering cables, 130 kilograms of sand are necessary per linear meter laid.

Claims (11)

1. Device for coating an elongated object, such as a cable, pipe, set of cables or the like, intended to be buried in the ground, by at least one external protective coating in the form of a strip, characterized in that it comprises - a reserve (4) of said elongated object (2) to be coated - a reserve (5) of said protective coating (3), said  elongated object and said protective covering being  adapted to be subjected to a forward movement - equipment (6) for gradually folding said cover  protection around said object elongates as and  measure of the advance of these, so that the edges  longitudinal of said covering are at least contiguous  and - equipment (7) for fixing said folded covering around  said elongated object to obtain, at the exit of said team  ment, an end product consisting of said object (2) and said  covering (3) and ready to be buried in the ground. 2. Device according to claim 1, characterized in that said equipment (6) for folding the coating is in the form of a gutter (15) with evolving cross sections, the inlet (15A) of said gutter being planar for receive said coating (3) from the reserve, while the outlet (15C) of said gutter is substantially circular so that the coating surrounds said elongated object previously disposed thereon. 3. Device according to claim 2, characterized in that said gutter (15) comprises a set of rods (16) connected transversely to each other by cradles (17) and conform to evolve, at the entrance of the gutter, a planar section towards a circular section at the outlet of the gutter. 4. Device according to one of claims 1 to 3, characterized in that, between said coating reserve and said folding equipment, there is provided at least one transverse roller housing (8, 9), parallel, which receives said covering strip (3) to direct it towards said equipment (6), and in that a guide (14) is attached to said housing to direct and deposit said elongated object on said covering (3), substantially in the middle of it . 5. Device according to any one of the preceding claims 1 to 4, characterized in that said equipment (6) for fixing said folded covering around said elongated object is defined by a tape (20) comprising - a rotary disc (21) provided from a central opening to  through which said final product can pass - a plurality of spindles (22) mounted in an equi  angularly distributed on said disc, around said  opening ; and - coils (23) mounted respectively on said  bobbins and whose wires (23A), due to rotation  of the disc and of the advance movement of the product, surround  and helically fix the external covering (3) on  said elongated object (2). 6. Device according to claim 5, characterized in that the tension of said wires (23A) is between 10 and 50 N. 7. Device according to one of claims 5 or 6, characterized in that a sensor wheel (26) is provided on said folding equipment (6), said wheel being in contact with the protective coating and connected to the motor d drive of said tape recorder. 8. Device according to one of claims 1 to 7, characterized in that, between the two devices (6, 7), there is arranged a removable cage (19) of circular cross section, inside which is held in place said folded covering around the elongated object until the action of said fixing equipment (7). 9. Device according to any one of the preceding claims 1 to 8, characterized in that said reserves consist of drums (4, 5) around which are respectively wound said elongated object and said protective strip coating. 10. Device according to any one of the preceding claims 1 to 9, characterized in that, at the outlet from the fixing equipment (7), there is provided a reserve (32) around which said final product is wound (P ).  ll. Motorized machine for digging trenches intended for laying elongated objects, of the type comprising a cutting wheel (29) or the like, characterized in that it further comprises at least one reserve (32) of final product ( P) consisting of said elongated object and of said external protective coating, and obtained by the device (1) defined according to any one of the preceding claims 1 to 10. 12. Mechanized assembly for digging trenches and laying elongated objects in the trench, of the type comprising a motorized device provided with a cutting wheel (29) or the like, characterized in that it comprises a device (1) as defined in any one of claims 1 to 9, and configured as a mobile unit for laying, in the bottom of said trench, the final product obtained, consisting of said elongated object and said external protective coating.