SENSOR-FITTED METAL NET

Abstract

A metal net having entwined metal wires defining the meshes of the metal net comprises at least one elongate sensor element fixed integrally to the metal net, inserted into the net during the production thereof. The elongate sensor element may comprise a wire of a material having a low coefficient of variation of the resistivity and a high gauge factor, preferably formed from constantan, or else may be of the optical fibre or composite fibre type.

Claims

1.-15. (canceled)

16. A metal net having entwined metal wires defining the meshes of the metal net, comprising at least one elongate sensor element integrally fixed to the metal net, wherein the at least one elongate sensor element is added to the wires with which the metal net is produced, so as to form together therewith three-wire nodes, or else may be substituted for a wire of the metal net to produce two-wire nodes at the entwinements with the adjacent metal wires, wherein the at least one elongate sensor element is inserted selectively at nodes of the meshes of the metal net in the longitudinal direction of the net.

17. The metal net according to claim 16, wherein at least one transverse elongate sensor element is incorporated to form meshes in the metal net, inserted selectively at nodes of the meshes of the metal net in the transverse direction of the net.

18. The metal net according to claim 16, wherein the at least one elongate sensor element is incorporated into the meshes of the metal net, taking on a substantially rectilinear path or else a wavier path with loops.

19. The metal net according to claim 16, wherein the at least one elongate sensor element comprises a substantially rectilinear wire of a material having a low coefficient of variation of resistivity and a high gauge factor, preferably formed of constantan, or of a material having similar features, for example a copper-manganese-nickel alloy, a copper-zinc-nickel alloy and/or an alloy of nickel and chromium.

20. The metal net according to claim 16, wherein the at least one elongate sensor is covered with a layer or sheath of insulating material.

21. The metal net according to claim 16, wherein the at least one elongate sensor is an optical fibre sensor or a composite fibre sensor.

22. The metal net according to claim 21, wherein the elongate sensor is an optical fibre sensor based on scattering phenomena.

23. The metal net according to claim 21, wherein the elongate sensor is an optical fibre sensor based on Brillouin scattering.

24. A monitored bank for containing a waterway or basin, comprising an embankment with two flanks, a metal net according to claim 16 being embedded in at least one of the two flanks.

25. The monitored bank according to claim 24, wherein the at least one elongate sensor element is arranged parallel to a primary direction of the bank itself.

26. A road or railway embankment comprising a foundation and a road or railway pavement, comprising at least one net according to claim 16.

27. The road or railway embankment according to claim 26, wherein the at least one net comprising elongate sensor elements is positioned in at least one of the following positions: at the base of the road embankment, at the base of the foundation, in the interior of the foundation, in the interior of the pavement.

28. A process for manufacturing a metal net according to claim 16, wherein the at least one elongate sensor element fixed integrally to the metal net is inserted into the net during the production thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Further features and advantages will be apparent from the following detailed description of preferred embodiments, referring to the accompanying drawings, given by way of non-limiting example, in which:

[0028] FIG. 1 is a view of an example of a portion of hexagonal-mesh net incorporating aspects of the present invention,

[0029] FIG. 2 is a view of a second example of a portion of hexagonal-mesh net incorporating aspects of the present invention,

[0030] FIG. 3 is a view of a third of a portion of hexagonal-mesh net incorporating aspects of the present invention,

[0031] FIG. 4 is a view of a fourth of a portion of hexagonal-mesh net incorporating aspects of the present invention,

[0032] FIG. 5 is a view of a bank of a river reinforced with a hexagonal-mesh net incorporating aspects of the present invention, and

[0033] FIG. 6 is a view of a reinforced road embankment comprising a hexagonal-mesh net incorporating aspects of the present invention.

DETAILED DESCRIPTION

[0034] Referring now to FIG. 1, an example is shown of a portion of preferably hexagonal-mesh net incorporating aspects of the present invention. The net 1 may be a double-twist hexagonal-mesh net, which may comprise a plurality of wires 2, 3, 2, 3, in particular metal wires, preferably made of steel, entwined around one another in twisted portions 7, 7 to form hexagonal meshes 4. The twisting follows a single twisting direction in each twisted portion 7, 7: clockwise or anticlockwise but constant in each twisted portion. In FIG. 3, the twisted portions 7, 7 have the wires 2, 3 entwined in an alternating direction between one row and the next: if the wires 2 and 3 are entwined with one another clockwise in one row, the wires 2 and 3 are entwined anticlockwise in the row below and the row above. However, a variant in which all the twisted portions 7, 7 have a single entwinement direction is not to be excluded.

[0035] The net 1 may comprise at least one elongate sensor 5 inserted longitudinally through selected twisted portions 7. The elongate sensor 5 may form two trapezoid meshes 6 flanked by two successive twisted portions 7 in a longitudinal direction defined by the direction along which the elongate sensor 5 extends. The elongate sensor is preferably a wire of an alloy for extensometers, for example constantanan alloy of copper and nickelor any other known metal alloy having good sensitivity to deformation (gauge factor) and a relatively low sensitivity to the amplitude of the deformation and to temperature. For this purpose, other known alloys having similar features may be used, for example the copper-manganese-nickel alloy known by the trade name manganin, the copper-zinc-nickel alloy known as nickel brass, and the alloy of nickel and chromium known as nichrome. The elongate sensor 5 may be covered with a layer or sheath of insulating material. In some applications, it is also possible to use an optical fibre or composite fibre elongate sensor.

[0036] At the heads of the elongate sensor 5, with variable spacing, a known data acquisition system is provided comprising an electronic device which detects, in the case of the use for example of a constantan wire, the electrical potential at the heads of the elongate sensor 5, and is capable of reporting and/or storing a variation in said electrical potential.

[0037] In the case of the use of optical fibres or composite fibres, an equivalent data acquisition system in the use of these fibres is provided in the installation step on a building site, in a spacing which is variable as a function of the subdivisions in individual homogeneous stretches to be monitored. The system normally provides at least one light source and a photodetector.

[0038] Referring now to FIG. 2, another example is shown of a portion of hexagonal-mesh net incorporating aspects of the present invention. In the variant of FIG. 2, the net 10 further comprises at least one transverse elongate sensor 11. The transverse elongate sensor 11 is arranged perpendicular to the elongate sensors 5, which are intersected by the transverse elongate sensor 11 at intersections 12. The at least one transverse elongate sensor 11 is inserted into the interior of twisted portions 7 formed by only two longitudinal wires 2, 3, 2, 3. The at least one transverse elongate sensor 11 is also preferably a wire of an alloy for extensometers, for example constantanan alloy of copper and nickelor any other known metal alloy having good sensitivity to deformation (gauge factor) and a relatively low sensitivity to the amplitude of the deformation and to temperature. For this purpose, other known alloys having similar features may be used, for example the copper-manganese-nickel alloy known by the trade name manganin, the copper-zinc-nickel alloy known as nickel brass, and the alloy of nickel and chromium known as nichrome. The transverse elongate sensor 11 may be covered with a layer or sheath of insulating material. In some applications, it is also possible to use an optical fibre or composite fibre elongate sensor. The transverse elongate sensor 11 may be of the same type as or a different type from the elongate sensor 5. At the heads of the transverse elongate sensor 11, a known electronic circuit is provided, which detects, in the case of the use of constantan or the like, the electrical potential at the heads of the transverse elongate sensor 11, and is capable of reporting and/or storing a variation in this electrical potential. The electronic circuit may be combined with the electronic circuit which detects the potential difference in the elongate sensor 5, or else may be a different electronic circuit.

[0039] It should be noted that the net portions depicted in FIGS. 1 and 2 exhibit a single longitudinal elongate sensor 5 and a single transverse elongate sensor 11 because the portion of the net 1 depicted in the drawings is small so as to make it possible to appreciate the details thereof. However, a plurality of longitudinal and transverse elongate sensors may normally be provided. A net having these features is capable of reporting, by way of a the electronic circuit or circuits arranged at the heads of each longitudinal 5 and/or transverse 11 elongate sensor, deformation events caused for example by a load or impact on the net, or else of being used as a structure forming a monitoring system linked to an element having its own mechanical resistance features, such as a metal net.

[0040] A net 1 as described above with reference to FIG. 1 or 2 may be produced by way of a machine of the type forming the subject matter of patent PCT/IB2017/050700, by the same applicant. It should be noted that the machine described in said patent application does not place any limits on the length of the sensor 5. Indeed, the machine feeds the element directly from a bobbin, which does not have size limitations imposed by the machine or by the manufacturing process. This aspect is particularly beneficial in the case where the sensor is an optical fibre, since it is preferable to reduce the number of junctions as much as possible.

[0041] Referring to FIG. 3, another example is shown of a portion of hexagonal-mesh net 16 incorporating aspects of the present invention. In this case, the net 16 is formed by wires 18 entwined together at the nodes 24 so as to form hexagonal meshes. At selected intervals, an elongate sensor 20, which extends longitudinally to form trapezoidal meshes with the adjacent wires 18 to which it is entwined at the nodes 24, is placed in place of one of the wires 18. As described above in relation to the examples of FIGS. 1 and 2, the at least one elongate longitudinal sensor 20 is preferably a wire of an alloy for extensometers, for example constantanan alloy of copper and nickelor any other known metal alloy having good sensitivity to deformation (gauge factor) and a relatively low sensitivity to the amplitude of the deformation and to temperature. For this purpose, other known alloys having similar features may be used, for example the copper-manganese-nickel alloy known by the trade name manganin, the copper-zinc-nickel alloy known as nickel brass, and the alloy of nickel and chromium known as nichrome. The elongate longitudinal sensor 20 may be covered with a layer or sheath of insulating material. In some applications, it is also possible to use an optical fibre or composite fibre elongate sensor. At the heads of the longitudinal elongate sensor 20, a known electronic circuit is provided, which detects the electrical potential at the heads of the longitudinal elongate sensor 20, and is capable of reporting and/or storing a variation in this electrical potential. In the case where the elongate sensor 20 is of the optical fibre or composite fibre type, another data acquisition system is provided at the heads thereof, generally comprising at least one light source and at least one photodetector.

[0042] In FIG. 4, another example is shown of a portion of hexagonal-mesh net 16 incorporating aspects of the present invention. In this case, the net is formed by the wires 18 entwined together at the nodes 24 so as to form hexagonal meshes. At selected intervals, an elongate sensor 20, which extends longitudinally to form trapezoidal meshes with the adjacent wires 18 to which it is entwined at the nodes 24, is placed in place of one of the wires 18. By comparison with FIG. 3, where the elongate sensor 20 is substantially rectilinear, in the example of FIG. 4, the elongate sensor 20 is arranged so as to form curved loops. In a single net, it is possible also to use elongate sensors 20 arranged substantially rectilinearly as well as sensors 20 arranged in a loop, as is shown by way of non-limiting example at the edges of the net in FIG. 4.

[0043] A net as described above with reference to FIGS. 3 and 4 may be produced by way of a machine described in document WO 2011/030316 by the same applicant.

[0044] Referring now to FIG. 5, a net having incorporated elongate sensors may be used for producing a bank 30 of a river, a canal, a lake or the like. In particular, a net 1 as described above with reference to FIG. 1 may be used, optionally also folded so as to form a mattress structure. Naturally, it is also possible to use a net 10, 16, 16 like those of FIG. 2, 3 or 4, or having features combined from among those of the four described types of net.

[0045] In a known manner, the bank 30 comprises an embankment having two flanks 32 and 34: an inner flank 32, facing towards the water, and an outer flank 34, facing the opposite side. The net 1 may be used to reinforce only one of the flanks 32, 34 or both. For this purpose, it is placed on the previously compacted ground. Subsequently, it may also be covered, for example with soil, as in the example case of FIG. 5.

[0046] The net 1 is placed on the ground with the elongate sensor elements 5 preferably arranged parallel to the direction of the river or parallel to the shore, in the case of a water basin, or in other words parallel to a primary direction of the bank itself. In this way, a single sensor element monitors long stretches of the bank 30. The bank further comprises a communication backbone 36, preferably positioned on the summit 38 of the bank.

[0047] The bank 30 may further comprise a rain sensor 40, which is particularly beneficial in the case where at least one of the two elongate sensors 5 detects humidity or temperature. Indeed, it is clear that in the case of rain an increase in humidity and probably also a variation in temperature, which however are not attributable to a loss of the bank, will be detected. The possibility of monitoring the presence of rainwater thus makes it possible to interpret correctly the values detected by the sensors 5.

[0048] The bank 30 may also comprise a hydrometer 44, to monitor the height of the water. It may also comprise a surveillance video camera 42. The communication backbone 36 transmits the information received from all of the equipment, as well as the signals detected by detection control units 46, positioned a predetermined distance apart. The detection control units 46 may comprise a data acquisition system for acquiring the signal from the elongate sensor elements 5.

[0049] In use, the elongate sensors 5 monitor at least one parameter, for example deformation, temperature, humidity and vibration. It should be noted in particular that the fact that the sensors 5 are fixed at the nodes 7 of the net 1 causes the net itself to be the means by which the surrounding environment comes into contact with the sensors 5. The metal net 1, which in the illustrated example is completely embedded in the bank, undergoes all the deformations and vibrations to which the structure in which it is embedded is subjected, and therefore transmits them highly efficiently to the sensors.

[0050] The bank 30 is thus an intrinsically monitored bank. Naturally, the type of monitoring may be modified depending on the requirements of the particular stretch and on multiple variables, such as the atmospheric conditions, the detected height of the water etc. For example, it is possible to vary the sampling frequency, but also to set different alarm thresholds for each monitored parameter.

[0051] It should be emphasised that the net 1 maintains the functions of a conventional metal net for erosion control and for reducing the risks associated with the presence of burrowing animals. Further, the net 1, being provided with elongate sensors 5, also performs a further function of hydraulic and geotechnical monitoring.

[0052] For producing the bank 30 of FIG. 5, the use of optical fibres sensors 5 is particularly recommended, and in particular optical fibres based on scattering phenomena are preferable. The preferred choice is the use of optical fibres which use the Brillouin effect, because they are well suited to monitoring very long stretches effectively and precisely, as is indeed the case for banks of rivers, canals or lakes, which typically extend for many kilometres.

[0053] Referring now to FIG. 6, a net having incorporated elongate sensors may be used for producing a road or railway embankment. In the drawings, the example of a road embankment 50 on poles and a road embankment 54 free of poles is shown. Independently of the presence or otherwise of poles 52, the road embankment 50, 54 comprises at least one net having elongate sensors.

[0054] A first net 60 comprising elongate sensor elements is positioned at the base 56 of the road embankment 50, 54. A second net 62 comprising elongate sensor elements is positioned at the base of the foundation 58. A third net 63 comprising elongate sensor elements is positioned in the interior of the foundation 58, which may be bound or unbound. A fourth net 64 comprising elongate sensor elements is positioned in the interior of the road pavement 59, which may optionally comprise bituminous macadam. In the examples illustrated, both of the road embankments 50 and 54 comprise four nets 60, 62, 63, 64, comprising elongate sensors, even though it is naturally possible to use one net comprising elongate sensors in only one of the described positions, using nets free of elongate sensors in the other positions or alternative reinforcement structures.

[0055] Naturally, without prejudice to the principle of the invention, the embodiments and the implementation details may vary considerably from what is described and illustrated, without departing from the scope of the present invention as a result.