High-strength metal grids for containment and protection and their manufacturing apparatus

Abstract

The high-strength protective grid consists of multiple metal wires arranged alternately with a metal rope. The metal wires intersect each other at intersections or are twisted around the rope at twisted sections. The intersections between wires and the twisting of wires and ropes define the mesh of the grid. Both the intersections and twisting are unidirectional. The ropes are larger than the wires and have an outer diameter greater than 8 mm, preferably 9-12 mm, and more preferably about 10 mm. This grid is manufactured using equipment for passing such enlarged diameter ropes compared to conventional protective grid ropes.

Description

Technical Field

[0001] The present invention relates to the field of high-strength civil structures for the purpose of containment and protection, such as the construction of protective walls against rockfalls and avalanches, the bark-like coating of rock walls to prevent rock detachment, the three-dimensional stabilization of soil, cliffs, levees, tunnels, and road structures. It is used for the three-dimensional stabilization of dams, embankments, tunnels, and road structures, the construction of water-blocking walls for embankments, the protection of levees in water areas, the construction of dams, other sediment protection fences along rivers and streams, and general water conservancy facilities, the composition of gabions and other metal grid products, and all other uses in the generally known fields of civil engineering and geotechnical engineering.

[0002] The present invention has been developed with particular attention to metal protection and containment grids (grids) reinforced with metal ropes.

Background Art

[0003] For metal grids (metal grids) for containment and protection, a number of types are known, for example, loose mesh grids, electric welded grids, single-twisted, double-twisted, triple-twisted hexagonal mesh grids, etc. Each type of grid usually has a specific use according to the formation and technical characteristics of its metal components. For example, an electric welded grid is usually composed of a plurality of straight bars with a large diameter such as 12 mm, and has high mechanical strength against tension. These bars are arranged vertically and horizontally and welded to each other at the intersections to form a woven structure with square and / or rectangular meshes. While these grids are very tough, they are not suitable for civil engineering works (such as wall coatings and geotechnical methods that need to adapt to the ground shape) that require a certain flexibility in the grid because of their large weight and high rigidity.

[0004] Another example of protective gratings frequently used in civil engineering works to prevent rockfalls is a grating composed of multiple intersecting steel wires or ropes arranged at angles to each other (preferably perpendicularly). An example of this type of grating is illustrated and described in European Patent Application WO 2008 / 132654 by the same applicant. The ropes used in this type of grating have a diameter of 10-12 mm and are fixed to each other at intersections by various types of connecting devices. The most common are clamp studs or plates, or a pair of coiled steel rods tightly wrapped around the intersections of the ropes. These gratings have excellent tensile resistance and, at the same time, are flexible enough to absorb the energy of impacting objects or supports, such as stones and rocks. One drawback of these gratings is the relatively long time required for their manufacture. Furthermore, because the dimensions of these gratings are generally modest, they are used in civil engineering works of limited scale, such as so-called snow-catching umbrella systems and rockfall prevention fences.

[0005] As mentioned above, each known type of grating is particularly well-suited for use under specific conditions. However, in some cases, using the appropriate type of grating can be inconvenient, not very advantageous, and very expensive anyway. For example, a rockfall protection grating with excellent tensile resistance may be perfectly suited to its design and intended purpose, but its weight, size, difficulty in compacting and folding can complicate transportation. Furthermore, it may be expensive due to its constituent materials and manufacturing process, and its high rigidity may make installation difficult.

[0006] Another drawback of the known high-strength grids described above is that, while they provide sufficient resistance to impacts and thrusts from, for example, rock fragments, they do not guarantee complete safety if their mesh size is insufficient to hold rock fragments and other fine materials. For this reason, it is necessary to use hexagonal double-strand metal grid panels with smaller mesh dimensions than the main grid in combination with any of the aforementioned types of grids. These are manufactured by electric welding or cross-rope construction and form a filter that holds finer fragments. However, this makes the installation of the containment structure more complex and costly, and involves both electric-welded or cross-rope grids and double-strand grids as components.

[0007] In general, metal grids are known for their extremely simple crossing of metal wires in different fields, such as garden and courtyard enclosures, animal enclosures, coverings for wall structures to be painted, and other similar applications where high impact resistance is not required. In addition to conventional enclosure grids (single wires bent spirally and intertwined), grids are also known in which adjacent wires are wrapped around each other from the center of each mesh, with each entanglement formed by a half-turn clockwise and another half-turn clockwise. Examples of such grids are described in U.S. Patents 1,401,557 and 2,053,221. In some embodiments, a third wire has been introduced into these crossing structures, and a configuration has been proposed in which the wire runs linearly through the center of each mesh of the grid. However, these grids are unsuitable for civil engineering applications in the field of geotechnical engineering, such as retaining soil and rock slopes and protecting against rockfalls, and cannot guarantee reasonable resistance and reliability after impact, even minor impacts. In fact, even applying a small tensile force to the intersection of the grid in a direction perpendicular to the main direction of the intersecting wires will cause the intersection to loosen and open. Indeed, the resistance of these grid intersections is determined by the resistance of the wires to bending, which is far less than the breaking load of the wires when it is necessary to tear the wires to open the grid mesh (as in the high-strength grids mentioned earlier or the grids described later).

[0008] Another high-strength metal grid for protection and containment is described in U.S. Patent No. 6,279,858. This grid is woven from corrosion-resistant wire and is installed on the ground surface or fixed upright on an incline. The wires of this metal grid are manufactured from steel with a nominal resistance of 1,000 to 2,200 MPa. The metal grid has a rhomboid mesh, which is formed by bending single wires spirally and intertwining them. The main drawback of this grid is its cost. Because it is composed solely of high-strength steel wire, it is itself very expensive. Furthermore, the simple entanglement structure of the grid wires creates a vulnerability where, even if only one wire is damaged, it can completely detach from adjacent wires, causing the grid itself to completely open up. This irreparably compromises functionality and safety.

[0009] Another type of high-strength containment and protective grating consists of a combination of metal wire and metal rope. One example is the structure commercially available as Steelgrid® HR, manufactured by the applicant, Officine Maccaferri SpA. Several variations of these gratings are described in the applicant's European patent applications EP1680552 and EP2475477. These feature a grating structure reinforced by forming a hexagonal mesh by interlacing double-twisted metal wires, with some of the metal wires replaced by longitudinal metal ropes in the weaving of this mesh. The metal ropes in the Steelgrid® HR grating have a maximum diameter of 8 mm and a maximum tensile strength of 1770 MPa, and are woven alternately with the metal wires at nominal distances of 300 mm, 500 mm, and 1000 mm. Meanwhile, the nominal transverse pitch of the mesh formed by the metal wires is 80 mm. These gratings can be produced using standard equipment used for the manufacture of conventional double-twisted metal gratings.

[0010] Combining the versatility of double-strand netting with the added resistance of metal ropes, these protective and containment nets are particularly effective and highly valued in the market. However, due to inherent limitations resulting from their construction, these nets cannot meet certain specific requirements.

[0011] A known problem in the manufacturing of grids by intersecting metal wires and metal ropes is that, in order to ensure the linearity of the ropes necessary to improve the grid's resistance, the ropes must be tensioned downstream of the beam (i.e., the cylinder from which the grid is drawn) after the intersection of the metal wires and metal ropes. However, this tension applied to the ropes downstream of the beam causes lateral constriction of the grid, resulting in two main negative effects. First, the grid width becomes smaller than the nominal dimension, reducing the lateral coverage of the grid relative to the design data and increasing the weight per unit area. This results in increased transportation costs and installation difficulties due to the need to use more grid reels to cover the same area. Furthermore, the grid constriction value cannot be reliably predicted and may vary from production lot to production lot. As a result, there is a risk that a particular grid supply may be rejected by the customer for not conforming to the design specifications.

[0012] Furthermore, another adverse effect caused by the narrowing of the grid downstream of the beam after the wire and rope have been woven is that it becomes impossible to properly insert the transverse ropes into the grid to increase lateral resistance. In the manufacturing process, the transverse ropes need to be inserted into the grid immediately after weaving and before the grid tension is adjusted by the beam. At this point, the grid has a nominal width corresponding to the design width, but the longitudinal ropes are untensioned and wavy. When transverse ropes are inserted into the grid in this state, a rope section equal to the nominal length is created. However, due to the narrowing of the grid width downstream of the beam, the length of the transverse ropes exceeds the grid width that is being narrowed. As a result, the transverse ropes form undulations to compensate for the reduction in grid width. These transverse undulations deform the grid, making winding difficult during transport and reducing the performance level, at least in the lateral direction, during operation. [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The object of the present invention is to overcome the above-mentioned drawbacks of conventional metal grids and to provide a metal grid that is reinforced with metal ropes and substantially maintains a predetermined flatness and nominal width after weaving. In this grid, the metal ropes are already substantially straight with minimal waviness during the manufacturing stage in which metal wires are intersected with each other and with metal ropes at predetermined intervals.

[0014] Another object of the present invention is to provide a metal grid reinforced with metal ropes, particularly of the double-twisted type. The metal ropes are laid out relatively straight in the longitudinal direction during the manufacturing process of the grid, while retaining the possibility of adding transverse ropes that are also relatively straight in the transverse direction of the grid when the grid is completed. As a result, the manufactured grid does not produce any significant undulations in the longitudinal or transverse direction, while retaining sufficient flexibility to adapt to various terrain formations in the fields of ground, embankment, slope, steep slope, and geotechnical engineering in general.

[0015] Another object of the present invention is to provide a metal grid, particularly one with a double-twist structure, that is reinforced with metal rope capable of withstanding high tensile forces, while simultaneously possessing flexibility, lightness, and ease of handling.

[0016] Furthermore, the present invention aims to provide a protective metal grid for use in the field of geotechnical engineering, particularly one with a double-twisted structure. This grid is economical and rapid to manufacture, and the manufacturing process can be mechanized and automated without using equipment that is particularly complex or extremely expensive compared to known protective grid manufacturing equipment. [Means for solving the problem]

[0017] To achieve the above objective, the present invention relates to a metal protective grid (metal protective grate) as described in claim 1. The present invention also relates to an apparatus particularly suitable for manufacturing such a grid.

[0018] In the first aspect, a protective grid for civil engineering works is described. This is made of multiple metal wires arranged alternately with a metal rope. The metal wires cross each other at wire intersections, or, for convenience of explanation, are twisted to the rope at intersections defined here as “rope intersections,” even if the twisting with the rope is done on the wire side. At this time, the rope is stretched as much as possible and maintains a substantially straight or slightly wavy direction of travel. The crossings between the wires and the twisting of the wires with the rope define the mesh of the grid, and the crossings and twistings are each unidirectional. The outer diameter of the rope is greater than that of the wires and exceeds 8 mm. Preferably, the outer diameter of the rope is 9 to 12 mm, excluding normal dimensional tolerances. More preferably, the outer diameter of the rope is about 10 mm, excluding normal dimensional tolerances. The metal rope may have a protective coating of plastic material that contributes to the formation of the overall outer diameter of the rope.

[0019] Experiments conducted by the applicant revealed, surprisingly, that ropes with a diameter exceeding 8 mm (preferably 9-12 mm, more preferably about 10 mm) remained substantially straight even before reaching the beam of the metal grid loom, after leaving the region where they intersected and woven with the metal wire. This supports the idea that the larger the diameter of the metal rope, the better its linearity is maintained, and therefore no narrowing due to rope straightening downstream of the beam occurs, thus preserving the nominal width of the grid. This is a desirable characteristic for ensuring the high-performance resistance of the grid. In fact, it has been confirmed that the more the rope is stretched, i.e., the more linear or substantially linear it is, the better the impact resistance and debris containment performance of the protective grid.

[0020] In certain embodiments, the protective grate may include a rope having a maximum tensile strength greater than about 1000 MPa, preferably greater than 1500 MPa, and more preferably greater than about 1700 MPa. The rope may be of various types, and in some embodiments it may be a helical rope.

[0021] In another embodiment, a manufacturing machine for producing the above-described type of protective grate is described. The device includes a series of pairs of first guide devices arranged coaxially and spaced apart from each other in a row parallel to the axis of the drum, and a series of pairs of second guide devices arranged coaxially and spaced apart from each other in a plane of symmetry that contacts the drum. Each pair of second guide devices is positioned in a mirror-symmetric position with respect to the plane of symmetry and corresponds to one of the pairs of first guide devices. The first and second pairs of devices are able to move alternately and simultaneously in half-steps in opposite directions parallel to the axis of the drum. In the device, the minimum distance between guide devices of the same type in the rope passage area is greater than 8 mm, preferably about 10 mm or more, more preferably about 12 mm or more, for example, 13 mm or more. [Brief explanation of the drawing]

[0022] Additional features and advantages will be understood from the detailed description of preferred embodiments with reference to the attached drawings. The drawings are provided only as non-limiting examples and are shown below: - Figure 1 is a perspective view including a partial cross-section of a part of the apparatus for manufacturing a protective grid incorporating the features of the present invention. A part of this grid can also be seen. - Figure 2 is a cross-sectional view of a portion of the apparatus shown in Figure 1, taken from a longitudinal perspective. - Figure 3 is a longitudinal cross-sectional view of a detailed part of the apparatus shown in Figure 1. [Modes for carrying out the invention]

[0023] In the following embodiments, features enabling the implementation of the present invention will be described. The described features can be combined with each other in various ways and are not necessarily limited to the exact embodiments referred to in the drawings and related descriptions. That is, for those skilled in the art who read the following description, paragraphs, terms or drawings that constitute restrictions on the possibility of separating one or more of the specific expressions, described and illustrated features in the description and combining them with one or more of the other described and illustrated features. More specifically, in this specification, any combination of any two explicitly described features should be understood to be explicitly described, even if those features are individually extracted from a specific context in which they coexist or are combined with other different features. Considering the skills and knowledge of those skilled in the art, and without the need to functionally apply other different features, for those who understand the possibility of functionally combining features, it should be understood as such. Unless otherwise specified, each element, member, means, system, component, object described and illustrated in this specification should be understood to be individually described, autonomously changeable, and separable / attachable from any other element, member, means, system, component, object described and illustrated. The described and illustrated materials, forms, functions are not intended to limit the present invention, but are described to enable those skilled in the art to understand and implement the invention according to preferred (but non-exclusive) embodiments.

[0024] Referring to FIG. 1, a part of an apparatus 10 for manufacturing a protective grid (protective grid) 12, particularly a metal protective grid in the field of civil engineering (rockfall / avalanche prevention fence, earth and sand prevention weir for waterways, bark-like coating material, rock slope / topography protection work, etc.), is shown as a perspective view including a partial cross-section.

[0025] More specifically, the protective grid 12 is composed of an assembly of metal wires 14 that intersect each other to form a series of meshes 16. In the illustrated embodiment, the meshes 16 are substantially hexagonal. The dimensions of the hexagonal meshes are standardized and generally known in the field of double-twisted metal grids and do not limit the present invention in any case. The present invention can be implemented using any type and form of hexagonal mesh, and the ratio of width to height is generally in the range of about 0.70 to about 0.85 in the art (e.g., - at least nominally - about 0.75 (60×80 mm mesh), about 0.80 (80×100 mm mesh), about 0.83 (100×120 mm mesh)).

[0026] The metal wires 14 are generally arranged along the longitudinal direction of the protective grid 12 in their longitudinal direction. The metal wires 14 intersect each other at the wire intersections 18. These wire intersections 18 are defined by portions where sections of each metal wire 14 are twisted together one or more times in a single direction of the twisting direction, i.e., clockwise or counterclockwise for each wire intersection 18. This knitting method defined as "double twist" is particularly excellent in resistance and stability and enables the manufacture of a protective grid having a safe and strong mesh.

[0027] Metal ropes 20, which have higher resistance than the metal wires 14, are inserted at predetermined intervals into the assembly of metal wires 14. The metal ropes 20 generally have less wavy propagation than the metal wires 14, and are arranged as linearly as possible, or in a slightly wavy direction. This mainly contributes to the resistance of the protective grid 12 when impacts such as rocks from landslides are applied to the protective grid 12 itself. As shown in Figure 1 (only a part of the protective grid 12 and the metal ropes 20 are shown for simplification), it is preferable that the metal ropes 20 be kept as linear as possible with respect to the preferred longitudinal direction of the protective grid 12. In the example in Figure 1, it can be clearly seen that the metal wires 14 adjacent to the metal ropes 20 are wrapped around the ropes 20 at the rope intersections 22. At each rope intersection 22, the section of metal wire 14 is defined by the portion that has been twisted multiple times in one direction (clockwise or counterclockwise) relative to the rope, i.e., re-twisted in a single direction. The metal wire 14 intertwines with the metal rope 20, which has a transverse undulation relative to the preferred longitudinal direction, but this undulation is much smaller than that of the metal wire 14, and is either substantially straight or undulating, as mentioned above. Therefore, the metal wire 14 can form a so-called "half-mesh" 24, which can take on a characteristic semi-hexagonal shape in a protective grid where the intertwined metal wires form a hexagonal mesh.

[0028] The protective grate 12 can be formed from metal wires 14 made of common steel, for example, with a diameter of 2-3 mm or more, for example, 4-5 mm. This protective grate is flexible and easily transportable. Of course, the wires 14 can be replaced entirely or partially with thin metal ropes, for example, with a diameter of about 2-5 mm (much smaller than the diameter of the maximum metal rope 20).

[0029] The metal wires 14 and the largest metal ropes 20 can be covered with protective coverings, such as those made of plastic material, which prevents or at least reduces corrosion of the wires and / or ropes.

[0030] A particularly advantageous feature is that the metal rope 20 having a larger diameter, including the potential protective covering, has a total diameter exceeding 8 mm, preferably 9-12 mm, and more preferably about 10 mm. Naturally, this excludes typical dimensional tolerances in the field of metal rope manufacturing. The resistance characteristics of such a grid are substantially greater than those of known types of grids with rope diameters of 8 mm or less, given the same tensile resistance per square millimeter of rope. A protective grid composed of metal rope 20 with a diameter exceeding 8 mm, preferably 9-12 mm, and more preferably about 10 mm, has sufficient flexibility for winding and transport to the installation site, while retaining sufficient rigidity to construct a protective structure with relative dimensional stability after deployment. This is particularly advantageous, for example, in a bark-like covering, where the protective grid is placed on a rock face to hold back rock material that would otherwise peel away.

[0031] Further experiments have shown that using metal ropes with a diameter of 8 mm or more, preferably 9-12 mm, and more preferably about 10 mm, makes it much easier to maintain the ropes 20 in a stretched state during lattice manufacturing, regardless of whether or not a protective covering is present, due to the inherent stiffness of metal ropes of this outer diameter. This is particularly advantageous in the construction of the protective lattice 12, because the more linear the ropes 20 incorporated into the lattice, the greater the overall resistance of the lattice to impact. This is because the ropes 20, which are already substantially under tension, receive tensile force almost instantly, long before any force is applied to the metal wires of the lattice. In other words, the impact force applied to the protective lattice 12 is absorbed to the maximum extent by the ropes 20 almost instantaneously, and the residual force of the impact, with reduced strength, is evenly distributed by the lattice surface formed by the intersecting metal wires.

[0032] Preferably, the maximum tensile strength of the metal rope 20 is greater than approximately 1000 MPa, more preferably greater than 1500 MPa, and even more preferably about 1700 MPa or more. A rope with a maximum tensile strength of about 1770 MPa has been found to be particularly effective, but ropes with a maximum tensile strength of 2200 MPa or more can also be successfully used. Naturally, by using a metal rope 20 with a diameter of more than 8 mm (larger than the diameter of the ropes typically used in similar conventional protective gratings), it becomes possible to use steel with a lower unit tensile strength than known strengths. In any case, it is possible to make the overall resistance of the metal rope used in conventional gratings at least equivalent to or greater than that of the metal rope used in conventional gratings.

[0033] A particularly effective rope for constructing the grid according to the present invention is a galvanized helical rope with a nominal diameter of 10 mm. This rope is composed of a strand of 19 steel wires with a maximum tensile strength of 1770 MPa, and the minimum tensile strength of the rope is 93.166 kN. This rope conforms to the standard EN12385-10. Naturally, different types of ropes, such as those with multiple strands or core wires, can also be used. In any case, the fundamental aspect identified by the applicant is that the higher the strength of the rope, the less likely it is to cause waviness during grid manufacturing. Therefore, flatness is improved by using a rope with a larger diameter than those used in known large-scale structures. In this context, for example, as mentioned above, by using a high-strength rope, i.e., a rope with a high maximum tensile strength or a helical rope, even a rope with a diameter slightly exceeding 8 mm can provide a significant advantage in flatness.

[0034] The protective grid 12 described above cannot be manufactured with existing equipment that cannot accept ropes with an outer diameter exceeding 8 mm. Therefore, one of the objectives of the present invention is to provide a special apparatus for manufacturing a protective grid 12 having the above characteristics. The apparatus for producing a grid with the above characteristics is partially similar to known apparatus for packaging conventional double-strand grids. The following description concerns the apparatus as a whole, but will focus on detailing the novel and original elements that enable the manufacture of a grid using reinforcing ropes with a diameter exceeding 8 mm.

[0035] As shown in Figure 1, the apparatus 10 comprises a drum or beam 32, which is mounted within the apparatus's fixed housing by means (not shown) and is rotatable at a constant speed in the direction of arrow 34 about its axis T, synchronized with the speed of the wire crossing means 14. Radial projections or pins 38 protrude outward from the curved surface 36 of the drum. These pins are arranged in rows extending parallel to the axis T and are spaced at equal angular intervals. In each row, the pins 38 are spaced at equal intervals, and two adjacent rows are staggered by half a pitch in the axial direction. These pins form a grid with a hexagonal mesh and are used to hold a portion of the already formed grid in the discharge direction of the apparatus.

[0036] The means for crossing and / or interconnecting the metal wires and ropes consists of a series of pairs of first guide devices, spaced apart and coaxially arranged, and positioned parallel to the axis of the drum 32 on one side of the plane of symmetry tangent to the cylindrical circumferential surface of the beam 32. The pairs of guide devices are arranged radially with respect to the beam, and their pitch is the same as the pitch of the pins 38. The means for crossing and / or interconnecting the metal wires and ropes further includes a series of pairs of second guide devices, spaced apart and coaxially arranged, and positioned on the other side of the plane of symmetry tangent to the drum 32. Each pair of second guide devices is positioned opposite one of the pairs of first guide devices, which is mirror-symmetric with respect to the plane of symmetry. The pairs of first and second guide devices are able to move alternately and simultaneously in half-steps in a direction parallel to the axis of the drum 32. When in use, the rotation of the guide devices around their axes causes the wires to cross, and the movement of the pairs of first and second guide devices parallel to and opposite to the axis T of the drum 32 forms a hexagonal mesh. The crossing means operates in conjunction with the movement of the beam to weave the entire grid.

[0037] More specifically, below the drum 32 are two sets of bars 40, 42 and 44, 46 parallel to the axis T, which function as supports for rotatable semi-cylindrical bodies 60, 62, 64, 66. The function of the semi-cylindrical bodies is to twist wires and ropes together in pairs to form a grid 12.

[0038] Bars 40, 42 and 44, 46 have a U-shaped profile with their cross-section rotated 90 degrees. The bars are arranged in pairs, with the open ends of the U-shapes facing each other, and are located on a vertical plane of symmetry that is in contact with the periphery of the drum 32. Bars 40 and 42 form the upper pair, and bars 44 and 46 form the lower pair. Naturally, the terms “upper” and “lower” refer to the arrangement of the bars in the illustrated embodiment. However, in practice, different arrangements can be employed using wires or ropes that slide mainly horizontally and vertically, as shown in Figure 2, for example. More generally, the “upper” bars are located downstream in the operating direction relative to the corresponding “lower” bars, regardless of the installation height.

[0039] The pairs of bars 40, 42 and 44, 46 are supported by elements 50, 52, 54, 56 which constitute part of the fixed housing of the device 10. Furthermore, they are movable in a direction parallel to the direction of axis T. The upper bars 40 and 42 are similar to the lower pair of bars 44 and 46. At the end of each bar 40, 42, 44, 46, a semi-cylindrical seat is formed with an axis perpendicular to axis T, and each seat houses a corresponding semi-cylindrical rotating body 60, 62, 64, 66. The distance between each seating surface and adjacent seating surfaces within the same bar is substantially equal to the distance between pins 38.

[0040] The semi-cylindrical rotating body 62 housed in the upper bar 42 is aligned with the semi-cylindrical rotating body 66 of the lower bar 46 and has through holes 72 and 76 having axes parallel to the axes of the corresponding semi-cylindrical rotating bodies. The through holes 72 and 76 are also aligned. Wires 14 supplied to the grid 12 are formed and passed through the holes 72 and 76, as will be described later.

[0041] Upper semi-cylindrical rotating bodies 160, 162 and lower semi-cylindrical rotating bodies 164, 166 are provided in the area where it is desirable to insert the rope 20 into the grid 12. These are of a different type from those used for the passage of the wire 14 and have been modified to allow the passage of a large-diameter rope, as described above. These are of a different type from those used for the passage of the wire 14 and have been modified to allow the passage of a large-diameter rope (greater than 8 mm, preferably not limited to up to 12 mm), as described above. This makes it possible to manufacture the grid structure described later.

[0042] Below each semi-cylindrical body 60 and 160, supported by the upper bar 40, a cylindrical container 90 is attached, in which a wire 14 of a predetermined length is wound spirally. The wire 14 exits from the top of the container 90, passes through a through hole 70, and is supplied to the grid forming device. During use, the cylindrical container 90 rotates around the adjacent wire 14 or rope 20.

[0043] Each pair of bars 40, 42 and 44, 46 is connected to a moving mechanism. This allows the two vertically positioned bars 42, 46 and the two vertically positioned bars 40, 44 to move in the same direction parallel to the axis T of the drum 32, but facing opposite directions. These moving mechanisms are configured so that each semi-cylindrical shape supported by the same bar can move in translation from a position facing a first semi-cylindrical shape of the opposing bar to a second position facing a second semi-cylindrical shape adjacent to the first semi-cylindrical shape.

[0044] Furthermore, the semi-cylindrical rotating bodies are connected to a rotating mechanism by means such as the racks 100 and 102 shown in Figure 1, and are rotated in pairs by these mechanisms. This causes two adjacent wires 14 to entangle with each other, or the wires 14 to twist together with the rope 20, thereby creating twisted sections and gradually forming the mesh of the protective grid 12.

[0045] As described above, the upper semi-cylindrical bodies 160, 162 and lower rotating semi-cylindrical bodies 164, 166 used to twist the wire 14 and rope 20 have a different structure from those used to entangle only the metal wire 14. As shown in Figure 2, the lower rotating semi-cylindrical body 166 through which the rope 20 passes is provided with a through hole 176 having an enlarged diameter exceeding 8 mm, preferably 10 mm or more, more preferably 12 mm or more, for example, 13 mm or more. This allows the passage of rope 20 with an outer diameter exceeding 8 mm, preferably up to a maximum of 12 mm. Naturally, it is also possible to provide an enlarged diameter hole in the semi-cylindrical body 66 through which smaller diameter wires 14 pass, and the enlarged diameter is preferably the same as the diameter of the hole 166. This makes it possible to manufacture a protective grid 12 with a desired rope 20 arrangement using the apparatus 10.

[0046] The upper semi-cylindrical body 160 has a cylindrical container 90 attached to its lower part, and there is a space of 8 mm or more, preferably 10 mm or more, more preferably 12 mm or more, for example 13 mm or more, between the cylindrical container 90 and the adjacent container through which the rope 20 can pass. This ensures that when twisting the wire 14 around the rope 20 to form the wire intersection 22, the rope 20 passes through between two adjacent cylindrical containers 90 without interference while the cylindrical container 90 rotates around the rope 20. The upper semi-cylindrical body 162 is provided with a widened opening 163, into which the rope 20 is inserted at a slight incline. This allows the rope 20 to be moved in the direction of the wire 14 while the rope 20 is twisted around the wire 14. The engagement of each semi-cylindrical body in the racks 100 and 102 is configured such that at least the semi-cylindrical body 162 has a diameter sufficient to form a through hole 172 with a diameter of 8 mm or more, preferably 10 mm or more, more preferably 12 mm or more. For example, this allows the passage of a rope 20 with an increased diameter, such as 13 mm or more, as described above.

[0047] As more clearly shown in Figure 3, the pair of upper semi-cylindrical bodies 60, 160 are spaced apart from each other by an interval A corresponding to the mesh width of the grid 12. This interval is predetermined and does not change in known types of double-strand grids (including single-strand and rope-reinforced grids). As previously mentioned, in order to enable the manufacture of double-strand grids with ropes 20 of increased diameter, the through-hole 172 of the upper semi-cylindrical body 162 is formed with a diameter B greater than 8 mm and 12 mm or slightly greater. The through-hole 170 of the upper semi-cylindrical body 160 may have a diameter C of less than 8 mm, so that only a single metal wire 14 always protrudes from this hole, and the metal wire is spirally housed in a cylindrical container 90 located below the lower semi-cylindrical body itself. As previously mentioned, the minimum distance D between two adjacent semi-cylindrical containers (not limited to cases where passage for ropes 20 is provided) is preferably 12 mm or more, and not less than 8 mm.

[0048] The above device 10 makes it possible to reinforce the protective grid 12 with ropes (with or without plastic protective coating) having an outer diameter of approximately 8 mm or more. This allows for the maintenance of hexagonal meshes with conventionally known and preferred dimensions of 5 × 7, 6 × 8, 8 × 10, 10 × 12, and 12 × 14 mm. The preferred spacing between two adjacent ropes 20 is 25 cm to 100 cm or more. The overall lateral dimension of the grid is preferably 2 m to 5 m.

[0049] A particularly advantageous feature of the present invention is that the apparatus 10 enables the manufacture of a protective grate 12 in which the rope 20 has a larger diameter than those usable in known protective grates and therefore has higher resistance, as well as being more linear on the upstream side of the beam. This not only improves the performance level of the protective grate after impact, but also avoids narrowing of the nominal lateral dimension of the grate, particularly on the downstream side of the beam. In fact, as described above, ropes with a diameter greater than 8 mm (preferably 9 mm to 12 mm, more preferably about 10 mm) of the grate described above already have no undulation or maintain only very small undulation on the upstream side of the beam. As a result, the narrowing seen in known types of grates that occurs when the rope is straightened on the downstream side of the beam does not occur in this grate. This feature makes it possible to introduce lateral ropes into the protective grate 12 without causing undulation due to narrowing of the grate. In particular, it is advantageous to insert potential lateral ropes directly downstream of the discharge of wires or ropes from the semi-cylindrical rotating bodies 60, 62, and 160. It is particularly advantageous to insert the lateral rope Z, indicated by the thin line in Figure 3, at the position shown by the contour of the lateral rope Z, directly below the wire or rope discharge section from 162. The diameter of this lateral rope Z is smaller than the distance E between the axes of the wire or rope discharge holes from the semi-cylindrical rotating bodies 60, 62, 160, and 162.

[0050] When using the lateral rope Z, there is an additional advantage in that the impact force applied to the protective grid 12 is absorbed to the maximum extent virtually instantaneously, while simultaneously exerting an immediate suppressive effect in both directions by both the longitudinal rope 20 and the lateral rope Z.

[0051] Naturally, the principle of the invention remains the same, and the details of the form and structure of the embodiments can be broadly modified from those described and illustrated without departing from the scope of the present invention.

Claims

1. A high-strength protective grid for civil engineering and geotechnical engineering applications, manufactured by arranging metal wires (14) and metal ropes (20) alternately, wherein the metal wires intersect each other at intersections (18) or are twisted around the ropes at twisted sections (22), the intersections between the wires and the twisting of the wires and ropes define the mesh of the grid, both the intersections and twisting are unidirectional, and the outer diameter of the ropes is larger than that of the wires and exceeds 8 mm.

2. A protective grate according to claim 1, wherein the outer diameter of the rope (20) is 9 to 12 mm.

3. A protective grate according to claim 2, wherein the outer diameter of the rope (20) is approximately 10 mm.

4. A protective grate according to any one of claims 1 to 3, wherein the rope (20) has a protective covering of a plastic material that contributes to forming the overall outer diameter of the rope.

5. A protective grate according to any one of claims 1 to 4, wherein the maximum tensile strength of the rope (20) is greater than about 1000 MPa, preferably greater than 1500 MPa, and more preferably about 1700 MPa or more.

6. A protective grate as described in any one of the preceding paragraphs, wherein the rope (20) is a spiral rope.

7. A protective grate as described in any one of the preceding paragraphs, wherein the grate is substantially planar.

8. A protective grid as described in any one of the preceding paragraphs, comprising a lateral rope (Z) that intersects the mesh of the grid.

9. A protective grate manufacturing apparatus as described in any one of the preceding paragraphs, comprising: a series of pairs of first guide devices arranged coaxially and spaced apart from each other in a row parallel to the axis of a drum; and a series of pairs of second guide devices arranged coaxially and spaced apart from each other in a plane of symmetry that contacts the drum, wherein each pair of second guide devices is arranged mirror-image symmetrically with respect to the plane of symmetry from one of the pairs of first guide devices, the first and second pairs of guide devices are simultaneously movable in opposite directions by half a step in a direction parallel to the axis of the drum, and the minimum distance (D) between guide devices in the rope passage area exceeds 8 mm.

10. The apparatus according to claim 9, wherein the minimum distance between guide devices is 10 mm or more, preferably 12 mm or more, and more preferably 13 mm or more.

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