Conveyor belt

Abstract

The present invention relates to a conveyor belt (100) comprising: o a core (10) comprising metal carcass cords (11) extending in a longitudinal direction of the belt (100), the metal carcass cords (11) being coated in a first elastomeric matrix (15), and o a reinforcing ply (30) at least partially covering the upper face of the core (10), the reinforcing ply comprising - a plurality of metal reinforcing cords (21) arranged in parallel in a transverse direction of the belt, each reinforcing cord (21) comprising a plurality of metal monofilaments (23) helically wound around an empty center, each reinforcing cord having a total elongation at break greater than 8%, the total elongation at break being measured in accordance with the ASTM D 2969-00 standard, and - a second elastomeric matrix (25) coating the monofilaments (23).

Description

[0001] CONVEYOR BELT

[0002] FIELD OF INVENTION

[0003] The invention relates to a conveyor belt for transporting bulk materials in mines, docks, metallurgy, machinery, and warehouses. The invention also relates to methods for manufacturing such a conveyor belt.

[0004] STATE OF THE ART

[0005] Conveyor belts are commonly used for transporting bulk materials in mines, docks, metallurgy, machinery, and warehouses. Conveyor belts are primarily composed of a core made of main steel cables extending in the direction of belt travel and an elastomeric matrix.

[0006] Such conveyor belts are subjected to harsh conditions and must withstand significant impacts. For example, the belts may be exposed to impacts from sharp objects, objects weighing several tens of kilograms, and loads falling onto the belt from a height of several meters, such as sharp stones or rocks. As a result, conveyor belts are frequently damaged by hard objects that pierce the belt and often cause longitudinal tears.

[0007] To prevent and minimize damage to the conveyor belt during impacts, protective reinforcements can be integrated into the belt structure above the belt web, and in some applications also below the web.

[0008] However, these reinforcements lead to an increase in the flexural rigidity, particularly in transverse bending, of the belt, which can become problematic to ensure good lateral guidance of the belt and good contact on the support rollers.

[0009] There are two main families of protective reinforcements: reinforcements based on textile fabrics, mainly polyamide, and reinforcements based on metal cables arranged in the transverse direction of the band.

[0010] Textile reinforcements can be made of strong yarns that can stop cracks if punctured by a penetrating object, thus effectively limiting the severity of the damage. This effect is due to the ability of polyamide yarns to stretch and gather at the base of the crack into a bundle that can become strong enough to stop the crack. However, polyamide textiles have limited tear resistance, especially when impacted by very sharp objects such as dolerite or slate. Furthermore, despite their stretchability, such reinforcements significantly increase the rigidity of the conveyor belt.

[0011] Other types of reinforcement include transverse wire cables held in position by longitudinal metal or textile binding threads, for example, made of polyamide or polyester. Protective reinforcements based on wire cables typically have higher breaking strength than textile reinforcements. The transverse wire cables used have an elongation at break of approximately 4–8%. Despite this high value for a metal cable, such reinforcements increase the stiffness of the conveyor belt more significantly than textile reinforcements. Thus, conveyor belts with such reinforcement are rigid in bending, which can disrupt the belt's behavior, particularly its stability on the transport rollers. Furthermore, wire cables are less flexible than textile reinforcements and therefore cannot organize themselves at the bottom of a crack to create a thicker reinforcement in that position.

[0012] DESCRIPTION OF THE INVENTION

[0013] One aim of the invention is to design a conveyor belt exhibiting improved resistance to breakage, while retaining sufficient flexibility for transverse bending of the belt on the rollers.

[0014] To this end, the invention proposes a conveyor belt comprising: a core comprising steel carcass cables extending in a longitudinal direction of the belt, said steel carcass cables being embedded in a first elastomeric matrix, and a reinforcing layer covering at least partially the upper face of the core, said reinforcing layer comprising

[0015] • a plurality of metal reinforcing cables, arranged parallel to each other in a transverse direction of the strip, each reinforcing cable comprising a plurality of metal monofilaments wound helically around an arch, each reinforcing cable having a total elongation at break greater than 8%, the total elongation at break being measured according to ASTM D 2969-00 and

[0016] • a second elastomeric matrix coating the monofilaments. Depending on advantageous but optional characteristics, taken alone or in combination:

[0017] - each carcass cable has a total elongation at break of less than 4%, the total elongation at break being measured according to ASTM D 2969 - 00.

[0018] - each carcass cable has a total elongation at break of between 1% and 3%, preferably between 2% and 3%, the total elongation at break being measured according to ASTM D 2969-00.

[0019] - each carcass cable is a multi-strand cable, each strand comprising several metallic monofilaments.

[0020] - Each metallic monofilament has a mechanical resistance between 1000 MPa and 5000 MPa.

[0021] - the reinforcement layer comprises a plurality of reinforcement layers juxtaposed in a single thickness on an upper face of the core in a longitudinal direction of the strip;

[0022] - the distance between two adjacent reinforcement cables is less than or equal to 4 mm, preferably 2.2 mm;

[0023] - Each reinforcing cable has a monofilament diameter Df and a helix radius Rf such that: 9 < Rf / Df < 30, and the arch is defined by a cylinder radially internal and tangent to each monofilament, said cylinder having an arch diameter D v such that 1.30 < D v / Df < 4.5;

[0024] - each reinforcing cable comprises between 3 and 10 monofilaments, preferably 5 monofilaments;

[0025] - each monofilament has a diameter Df between 0.1 and 0.5, preferably 0.35 mm;

[0026] - each reinforcing cable has an external diameter between 0.9 and 2.1, preferably 1.9 mm, and / or an internal arch diameter between 0.4 and 1.3, preferably 1.2 mm;

[0027] - the reinforcing cables extend over a width less than or equal to the width of the conveyor belt, preferably between 95% and 100% of the width of the conveyor belt;

[0028] - the conveyor belt further includes an upper coating and / or a lower coating made of an elastomeric matrix;

[0029] - the conveyor belt further includes at least one reinforcing layer arranged on an underside of the web.

[0030] Another object of the invention relates to a method for manufacturing a conveyor belt, comprising: o providing a core comprising carcass metal cables extending in a longitudinal direction of the belt, said metal cables being embedded in a first elastomeric matrix; o providing a plurality of reinforcement cables, each reinforcement cable comprising a plurality of metal monofilaments wound helically around an arch, each reinforcement cable having a total elongation at break greater than 8%, the total elongation at break being measured according to ASTM D 2969-00; o arranging the reinforcement cables parallel to each other in a plane; o embedding all the reinforcement cables in an elastomeric matrix such that each monofilament is embedded in the elastomeric matrix;o the covering of the upper face of the core by a plurality of reinforcing layers in the longitudinal direction of the strip, the reinforcing cables extending in a transverse direction of the strip.;

[0031] The said process may include covering the underside of the core with a plurality of reinforcing layers as described above.

[0032] BRIEF DESCRIPTION OF THE FIGURES

[0033] Other features and advantages will become apparent from the detailed description that follows, with reference to the attached drawings, on which:

[0034] - Figure 1 is a perspective view of a portion of a conveyor belt according to the invention;

[0035] - Figure 2A illustrates a first embodiment of the arrangement of monofilaments in a core cable;

[0036] - Figure 2B illustrates a second embodiment of the arrangement of monofilaments in a core cable;

[0037] - Figure 3 is a perspective view of a reinforcement layer for a conveyor belt according to the invention;

[0038] - Figure 4 is a perspective view of the core cables and reinforcement cables of a conveyor belt according to the invention;

[0039] - Figure 5A is a top view of the metal cables present in a conveyor belt;

[0040] - Figure 5B is a cross-sectional view of the cables in Figure 5A;

[0041] - Figure 5C is a longitudinal cross-sectional view of the cables in Figure 5A;

[0042] - Figure 6 is a perspective view of a plurality of open reinforcing cables

[0043] - Figure 7 illustrates the arrangement of monofilaments in a hyperelastic yarn. For the sake of clarity, the elements shown are not necessarily drawn to scale.

[0044] DETAILED DESCRIPTION OF IMPLEMENTATION METHODS

[0045] In this text, the terms "front" and "rear," "anterior" and "posterior" refer to the direction of movement of the conveyor belt during its use. The terms "vertical," "horizontal," "upper," and "lower" refer to the position of an object transported on the belt, oriented in the direction of transport.

[0046] Figure 1 is a perspective view of a portion of a conveyor belt 100 according to the invention. The conveyor belt comprises a core 10 made of carcass wire ropes 11 embedded in an elastomeric matrix, preferably rubber. The carcass wires 11 are the main wires of the conveyor belt and extend in a longitudinal direction x corresponding to the direction of belt circulation. The carcass wires 11 are rigid wire ropes. By rigid, it is understood that the total elongation at break is less than 4%, preferably between 1% and 3%, or even between 2% and 3%. By way of illustration and without limitation, the carcass wires are typically multi-strand wire ropes, each strand comprising several monofilaments. Preferably, the monofilaments are arranged helix and the strands are arranged helix.Metallic means a material consisting of at least 50% of its mass of a metallic material.

[0047] The measurement of the total elongation at break is carried out according to the ASTM D 2969 - 00 standard on a metal cable intended for tire reinforcement.

[0048] The measurement is performed using one or more cable samples extracted from a conveyor belt. Each cable sample shows traces of vulcanized elastomeric material.

[0049] The measurement is performed on a tensile testing machine that stretches the cable until it breaks in order to determine the breaking force F m of the wire rope as well as the force exerted during elongation. Elongation is measured with an extensometer, preferably a mechanical extensometer which is in contact with the wire rope.

[0050] The cable is held by clamps that allow for extension of the wire rope until it breaks outside the clamp's gripping zone. Clamps with a gradual curve are therefore preferred. The test begins by applying a load to the sample (called preload) corresponding to 1% of the estimated breaking force, which initiates the elongation measurement. This corresponds to a zeroing of the deformation.

[0051] This preload is estimated beforehand based on 3 force-at-break measurements taken with the same device.

[0052] The measurement consists of recording the force curve as a function of the cable elongation until the break occurs.

[0053] The measurement is considered valid when the point of rupture is located in the area between the clamps, outside the gripping area of ​​the metal reinforcement.

[0054] The elongation measured at the point of rupture is called the total elongation A t and is calculated as follows:

[0055] HAS t (%)= (L t - Lo) / L o 100 with:

[0056] L t = The distance between the arms of the extensometer at the time of rupture in mm, Lo = The initial distance between the arms of the extensometer in mm.

[0057] The result of the test is the value measured on a single test specimen.

[0058] The rigid longitudinal cables maintain the conveyor belt's dimensions in its longitudinal direction when it is tensioned for operation. In this configuration, the open transverse cables provide flexibility in the event of vertical compression shocks, thus offering resilience and absorbing these shocks to prevent damage to the longitudinal cables.

[0059] By way of illustration and without limitation, carcass cables 11A may be seven-strand cables 12 of seven monofilaments 13 per strand, as shown in Figure 2A. Such cables typically have a diameter between 2 and 6 mm. In another example, with reference to Figure 2B, carcass cables 11B may, for instance, comprise seven strands 12 of nineteen monofilaments 13 per strand. Such cables typically have a diameter between 4 and 14 mm.

[0060] The monofilaments of carcass cables are, for example, made of steel, preferably pearlitic steel, carbon ferritic-pearlitic steel, or stainless steel containing at least 10.5% chromium. The monofilaments may have a coating of copper, zinc, tin, cobalt, or an alloy of these metals, such as brass or bronze. Each metallic monofilament typically has a tensile strength of 1000 MPa to 5000 MPa. The tensile strength is measured according to ASTM D 2969-00 on a steel cable intended for tire reinforcement.

[0061] The initial cross-section of the wire rope (So) is determined upstream of a tensile measurement.

[0062] The measurement is performed on a tensile testing machine that stretches the cable until it breaks in order to determine the breaking force F mof the wire rope as well as the force exerted during elongation. Elongation is measured with a mechanical extensometer that is in contact with the wire rope during the procedure.

[0063] The cable is held by clamps that allow for the extension of the metal cables until they break outside the clamp's gripping area. Clamps with a gradual curve are therefore preferentially used.

[0064] The tensile test begins by loading the sample (called preload) corresponding to 1% of the estimated breaking force and allows the elongation measurement to be initiated (zeroing the deformation).

[0065] This preload is estimated beforehand based on 3 force-at-break measurements taken with the same device.

[0066] The measurement consists of recording the force curve as a function of the cable elongation until the break occurs.

[0067] The measurement is considered valid when the point of rupture is located in the area between the clamps, outside the gripping area of ​​the metal reinforcement.

[0068] Maximum mechanical resistance R m is determined from the maximum force F m and the initial section of the test specimen So according to R m [MPa] =

[0069] The carcass cables 11 are arranged parallel to each other and coated with an elastomeric matrix 15. The distance between the centers of two carcass cables D a is typically between 10 and 19 mm.

[0070] The conveyor belt also includes at least one reinforcing layer 30, 40. A first reinforcing layer 30 is typically arranged on the upper face of the web. A second reinforcing layer 40 can be arranged on the lower face of the web. The use of two reinforcing layers arranged on opposite faces of the web protects the belt against stress on both sides. The symmetry of the reinforcing layers can also improve the flexural behavior of the conveyor belt during use.

[0071] Typically, each reinforcement layer 30, 40 covers between 95% and 100% of the web width 10 to maximize the coverage of the conveyor belt and provide good protection over the entire width of the belt, without extending beyond the edges of the conveyor belt.

[0072] Each reinforcement layer comprises a plurality of reinforcing cables 21 arranged parallel to each other in a transverse direction t of the strip. The reinforcing cables 21 are therefore perpendicular to the carcass cables 11. Advantageously, in order to provide optimal protection against impacts and cracking, the distance D r between two adjacent reinforcing cables 21 is between zero and the external diameter of each reinforcing cable, preferably between half the external diameter and the external diameter of each reinforcing cable, more preferably less than or equal to 4 mm, for example 2.2 mm as illustrated in Figure 3.

[0073] The reinforcing cables 21 are embedded in an elastomeric matrix 25.

[0074] Preferably, each reinforcement layer 30, 40 comprises a plurality of reinforcement plies 20 placed side by side in the longitudinal direction x of the belt in a single thickness. Typically, a reinforcement ply 20 has a rectangular shape with a width less than or equal to the width of the reinforcement layer 30, 40. The length of each reinforcement ply is typically identical for all reinforcement plies 20 of the conveyor belt and is, for example, between 0.5 and 5 times the ply width. In this case, each reinforcement ply 20 comprises a plurality of reinforcement cables 21 embedded in an elastomeric matrix. Figure 3 schematically illustrates such a reinforcement ply. The plies are placed side by side along the entire length of the conveyor belt so that the reinforcement cables are arranged in the transverse direction of the belt.

[0075] Figure 4 illustrates the arrangement of the carcass cables 11 and the reinforcement layers 30, 40 in the conveyor belt. The reinforcement cables 21 have a smaller diameter than the carcass cables 11 and are oriented perpendicular to the carcass cables. With reference to Figure 5A, the distance D r The distance between the reinforcing cables 21 is less than the distance D a between the carcass cables 11, thus preventing the penetration of objects between the carcass cables.

[0076] With reference to Figure 5B and Figure 5C, the carcass cables 11 and the reinforcing cables 21 are arranged in separate layers, with a vertical spacing between the respective layers.

[0077] Preferably, the distance D zThe vertical z-direction gap between the carcass cables 11 and the reinforcing cables 21 is between 1 and 3 mm, preferably 1.5 mm. This gap is filled by a portion of the elastomeric matrix of the core 10 and a portion of the elastomeric matrix of the reinforcing layer 30 and 40. The gap between the carcass cables 11 and the reinforcing cables 21 is completely filled by one or more elastomeric materials.

[0078] The conveyor belt may have a coating 50, for example in an elastomeric matrix, on its upper face and / or on its lower face.

[0079] Open reinforcement cables are metal cables, preferably hyperelastic metal cables. Hyperelastic means that the total elongation at break is greater than 8%, for example, around 10%.

[0080] The measurement of the total elongation at break is carried out according to the ASTM D 2969 - 00 standard on a metal cable intended for tire reinforcement.

[0081] The measurement is performed using one or more cable samples extracted from a conveyor belt. Each cable sample has an arch filled with vulcanized elastomeric material.

[0082] The measurement is performed on a tensile testing machine that stretches the cable until it breaks in order to determine the breaking force F m of the wire rope as well as the force exerted during elongation. Elongation is measured with an extensometer, preferably a mechanical extensometer which is in contact with the wire rope.

[0083] The cable is held by clamps that allow for the extension of the metal cables until they break outside the clamp's gripping area. Clamps with a gradual curve are therefore preferentially used.

[0084] The test begins by loading the sample (called preload) corresponding to 1% of the estimated breaking force and allows the elongation measurement to be initiated (zeroing the deformation).

[0085] This preload is estimated beforehand based on 3 force-at-break measurements taken with the same device.

[0086] The measurement consists of recording the force curve as a function of the cable elongation until the break occurs.

[0087] The measurement is considered valid when the point of rupture is located in the area between the clamps, outside the gripping area of ​​the metal reinforcement.

[0088] The elongation measured at the point of rupture is called the total elongation A t and is calculated as follows:

[0089] HAS t (%) = ^^ - 100 with:

[0090] L t = The distance between the arms of the extensometer at the moment of rupture in mm, Lo = The initial distance between the arms of the extensometer in mm. The result of the test is the value measured on a single specimen.

[0091] The monofilaments of the reinforcing cables may be made of a metal, preferably steel. The metal or steel used, whether carbon steel or stainless steel, may itself be coated with a metallic layer that improves, for example, the handling properties of the wire rope and / or its constituent elements, or the performance properties of the conveyor belt cable itself, such as adhesion, corrosion resistance, or resistance to aging. In a preferred embodiment, the steel used is coated with a layer of brass (Zn-Cu alloy) or zinc.

[0092] Figure 6 and Figure 7 illustrate an assembly of open reinforcing cables 21 in a reinforcement layer. Each open reinforcing cable 21 comprises a single layer made up of N metallic monofilaments 23, N being an integer, typically between three and ten. Preferably, the layer consists of five monofilaments 23. Each metallic monofilament has a diameter Df.

[0093] A monofilament is defined as an element extending longitudinally along a principal axis and having a cross-section perpendicular to the principal axis, where the largest dimension G is relatively small compared to the dimension L along the principal axis. Relatively small means that L / G is greater than or equal to 100, preferably greater than or equal to 1000. This definition covers both monofilaments with a circular cross-section and wire elements with a non-circular cross-section, for example, polygonal or oblong cross-sections. Preferably, each metallic monofilament has a circular cross-section.

[0094] The monofilaments 23 are wound helically with a helix radius of curvature Rf. The helix radius of curvature is equal to Rf = P / (TT sin(2a)), where P is the pitch of each metal monofilament and a is the helix angle of each metal monofilament. Thus, each metal monofilament describes a helical path around a principal axis substantially parallel to the principal axis of the cable. Referring to Figure 7, the external diameter D of the set of N monofilaments 23 corresponds to the external diameter of each helix. The monofilaments 23 define an internal arch 27 of the cable. The reinforcing cable 21 therefore lacks a central metal core. The internal arch 27 of the open reinforcing cable 21 is delimited by the monofilaments 23.

[0095] The preforming and the internal arch provide the cable, once assembled, with relatively significant ventilation, in other words, a relatively large space between each pair of adjacent monofilaments compared to the diameter of the monofilaments.

[0096] Preferably, the internal arch 27 has the shape of a right circular cylinder (also called a right circular cylinder). In this case, the internal arch 27 corresponds to a radially internal cylinder tangent to each monofilament. The diameter of this cylinder is equal to the arch diameter D v .

[0097] The helix diameter Dh is calculated according to the relation Dh=P x Tan(a) / TT in which P is the pitch at which each metallic monofilament is wound, a is the helix angle of each monofilament and Tan is the tangent function.

[0098] In a cross-section perpendicular to the main axis of the open reinforcing cable 21, the distance Dh / 2 between the center C of each metallic monofilament and the main axis of the cable is substantially constant and equal for all the metallic monofilaments in the layer. This distance Dh / 2 is equal to half the helix diameter Dh.

[0099] The open reinforcing cable is single helix. By definition, a single helix cable is a cable in which the axis of each metallic monofilament in the layer describes a single helix, as opposed to a double helix cable in which the axis of each monofilament describes a first helix around the cable axis and a second helix around a helix described by the cable axis.

[0100] Most advantageously, each reinforcing cable has a monofilament diameter Df and a helix bend radius Rf such that: 9 < Rf / Df < 30. Preferably, the internal arch diameter D v is such that 1.30 < D v / Df < 4.5.

[0101] Preferably, each monofilament has a diameter Df between 0.1 and 0.5, preferably 0.35 mm.

[0102] Each reinforcing cable can have an external diameter between 0.9 and 2.1, preferably 1.9 mm.

[0103] The internal arch diameter is advantageously between 0.4 and 1.3, preferably 1.2 mm.

[0104] The relative radial play J r can be defined by J r=N / (TT (D - Df)) ■ (Dh ■ Sin(TT / N) - (Df / Cos(a ■ TT / 180))), where N is the number of metallic filament elements in the layer. This parameter represents the distance separating each pair of adjacent metallic monofilaments relative to the available length for positioning the metallic monofilaments on the layer. Thus, the greater the relative radial gap J r The higher the J, the greater the space separating two adjacent metallic monofilaments relative to the maximum number of metallic monofilaments the layer could accommodate. Conversely, the higher J r is small, the smaller the space separating two adjacent metallic monofilaments is compared to the maximum number of metallic monofilaments that the layer could accommodate.

[0105] Advantageously, the relative radial clearance is such that 0.10 mm < J rThe 0.25 mm thickness maximizes the number of metallic monofilaments in a layer, thus increasing the cable's reinforcement capacity without compromising its ability to accommodate longitudinal compression deformations. Generally, the elastomeric matrix 25 of the reinforcement layer 20 encases all the monofilaments 23 within the open reinforcement cables 21. The internal arch 27 of each reinforcement cable 21 is therefore also filled with the elastomeric material of the matrix 25.

[0106] An open reinforcing cable comprising a single layer of helically wound metallic monofilaments and a method for manufacturing such a cable are described in FR3099191A1. Such cables are also known as "open cords".

[0107] Alternatively, an open reinforcing cable in the reinforcement layer can be a multi-strand of open reinforcing cables as described above.

[0108] The table below shows a comparison of different types of conveyor belt reinforcement. The measurements were taken on an isolated reinforcement strip, not assembled to a conveyor belt. The right-hand column presents the values ​​for an example of a reinforcement layer according to the invention, made with open reinforcement cables with the following parameters:

[0109] Diameter of a monofilament Df=0.35mm

[0110] External diameter of the open reinforcement cable D=1.9mm

[0111] Internal vault diameter D v =1.2mm

[0112] Number of monofilaments N=5.

[0113] The breaking strength of a reinforcement layer with open reinforcing cables is therefore greater than or equal to the breaking strength of a reinforcement layer comprising a polyamide fabric reinforcement. The range of breaking strength values ​​for a conveyor belt according to the invention overlaps with the values ​​corresponding to a reinforcement layer with transverse wire cables. The reinforcement layer according to the invention can therefore withstand the same impacts as known belts.

[0114] The transverse strength of a reinforcement layer comprising open reinforcing cables is comparable to the transverse strength that can be obtained for reinforcement layers comprising polyamide fabric or transverse metal cables.

[0115] The use of open transverse reinforcing cables avoids disruption of the transverse flexibility of the conveyor belt while allowing sufficient deformation of the reinforcing cables in any crack areas, thanks to the optimized modulus of elasticity of the open reinforcing cables.

[0116] A reinforcement layer using such open reinforcement cables presents a reduced thickness of protective reinforcement compared to polyamide textile fabrics.

[0117] Compared with a known reinforcement layer using transverse wire ropes held in position by tie wires, the density of open reinforcement wires can be higher than the density of wire ropes in a known reinforcement layer.

[0118] Open reinforcing cables exhibit very high mobility within the elastomeric matrix, resulting in high resistance to strip rupture, particularly against longitudinal cracks.

[0119] The cables also exhibit very high compressibility when subjected to transverse force during impact, for example, from a falling sharp object. This prevents excessive localized overloads that could lead to cable breakage.

[0120] The transverse arrangement of the open reinforcing cables allows the longitudinal flexibility of the conveyor belt to be maintained. The first elastomeric matrix of the core 15, the matrix 25 of the reinforcing layer, and any optional coating 50 can be made of the same or different elastomeric materials. Advantageously, the respective matrices of a conveyor belt and, where applicable, the coating, are made of materials that facilitate the adhesion of the layers prior to vulcanization, and the assembly of the belt by covulcanization of several layers.

[0121] The compounds of the elastomeric matrices 15, 25 and the coating 50 can be of fossil origin or bio-based. In the latter case, they can be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the aforementioned compounds can also come from the recycling of previously used materials; that is, they can be partially or totally derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. This includes, in particular, the matrix, reinforcing yarns, polymers, plasticizers, fillers, etc.

[0122] The compositions of the elastomeric matrices according to the invention and of the coating are based on at least one elastomer, a reinforcing filler, and a crosslinking system.

[0123] Any type of reinforcing filler known for its ability to strengthen a rubber composition can be used, for example an organic filler such as carbon black, an inorganic reinforcing filler such as silica, alumina, or a blend of these two types of filler.

[0124] Preferably, the reinforcing filler content is in the range of 5 to 200 parts per cent, preferably from 20 to 160 parts per cent. The term "part per cent" means, for the purposes of this patent application, parts by weight per hundred parts of elastomers, as determined by the composition preparation prior to baking.

[0125] For the purposes of the invention, the reinforcing filler is preferably chosen from the group consisting of silicas, carbon blacks, and mixtures thereof. More preferably, the reinforcing filler is predominantly carbon black, preferably in a proportion ranging from 30 to 90 parts per cent. Also preferably, the reinforcing filler is predominantly silica, preferably in a proportion ranging from 30 to 90 parts per cent.

[0126] Any type of crosslinking system known to those skilled in the art for its ability to strengthen a rubber composition for the manufacture of conveyor belts can be used.

[0127] Preferably, the crosslinking system is a vulcanization system, i.e., based on sulfur (or a sulfur-donating agent) and a primary vulcanization accelerator. Various known secondary accelerators or vulcanization activators, such as zinc oxide, stearic acid or equivalent compounds, and guanidine derivatives (in particular diphenylguanidine), may be added to this basic vulcanization system, incorporated during the first non-productive phase and / or during the productive phase as described later.

[0128] Sulfur is used at a preferential rate of between 0.5 and 10 pc, more preferentially between 0.5 and 5 pc, in particular between 0.5 and 3 pc.

[0129] The vulcanization system for the composition according to the invention may also include one or more additional accelerators, for example, compounds from the thiuram family, zinc dithiocarbamate derivatives, sulfenamides, guanidines, or thiophosphates. In particular, any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur may be used, including thiazole-type accelerators and their derivatives, thiuram-type accelerators, and zinc dithiocarbamates.These accelerators are most preferably chosen from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide (abbreviated "CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide (abbreviated "DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide (abbreviated "TBBS"), N-tert-butyl-2-benzothiazyl sulfenamide (abbreviated "TBSI"), zinc dibenzyldithiocarbamate (abbreviated "ZBEC"), and mixtures of these compounds. Preferably, a sulfenamide-type primary accelerator is used.

[0130] The elastomer can be chosen from the group consisting of diene elastomers and mixtures thereof.

[0131] By elastomer (or "rubber", the two terms being considered synonymous) of the "diene" type, it is recalled here that it must be understood in a known way to mean at least one (we mean one or more) elastomer derived at least in part (i.e., a homopolymer or a copolymer) from diene monomers (monomers bearing two carbon-carbon double bonds, conjugated or not).

[0132] Diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". Generally, "essentially unsaturated" refers to a diene elastomer derived at least in part from conjugated diene monomers, with a proportion of diene motifs or units (conjugated dienes) greater than 15% (mole percent); thus, diene elastomers such as butyl rubbers or EPDM-type diene-alpha-olefin copolymers do not fall under the previous definition and can be described as "essentially saturated" diene elastomers (low or very low proportion of diene motifs, always less than 15%). In the category of "essentially unsaturated" diene elastomers, a "highly unsaturated" diene elastomer is defined in particular as a diene elastomer having a rate of diene origin motifs (conjugated dienes) which is greater than 50%.

[0133] Having given these definitions, the term diene elastomer, which can be used in the compositions according to the invention, is understood more specifically to mean:

[0134] (a) any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms;

[0135] (b) any copolymer obtained by copolymerization of one or more dienes conjugated together or with one or more aromatic vinyl compounds having from 8 to 20 carbon atoms;

[0136] (c) a ternary copolymer obtained by copolymerization of ethylene, of an α-olefin having 3 to 6 carbon atoms with an unconjugated diene monomer having 6 to 12 carbon atoms, such as, for example, elastomers obtained from ethylene, propylene with an unconjugated diene monomer of the aforementioned type such as, in particular, hexadiene-1,4, ethylidene norbornene, dicyclopentadiene;

[0137] (d) a copolymer of isobutene and isoprene (butyl rubber), as well as halogenated versions, in particular chlorinated or brominated, of this type of copolymer.

[0138] Although it applies to any type of diene elastomer, those skilled in conveyor belt design will understand that the present invention is preferably implemented with essentially unsaturated diene elastomers, particularly of type (a) or (b) above.

[0139] Suitable conjugated dienes include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C1-C5 alkyl)-1,3-butadiene such as 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene, and chloroprene. Examples of suitable vinylaromatic compounds include styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene.

[0140] Copolymers can contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinylaromatic units. Elastomers can have any microstructure that depends on the polymerization conditions used, particularly the presence or absence of a modifying and / or randomizing agent and the quantities of modifying and / or randomizing agent used. Elastomers can be, for example, block, statistical, sequenced, or microsequenced, and can be prepared in dispersion or solution; they can be coupled and / or star-shaped or functionalized with a coupling and / or star-shaped or functionalizing agent. Here, "functionality" preferably refers to a chemical group that interacts with the reinforcing charge of the composition.

[0141] Preferably, the elastomer in the composition comprises predominantly an essentially unsaturated diene elastomer. The elastomer in the composition is preferably selected from the group consisting of polybutadienes (abbreviated "BR"), synthetic (IR) or natural (NR) polyisoprenes, butadiene copolymers, isoprene copolymers, chloroprene copolymers (e.g., neoprene), and mixtures of these elastomers. Such butadiene and isoprene copolymers are more preferably butadiene-styrene copolymers (SBR) and isoprene-styrene copolymers (SIR), nitrile-butadiene copolymers (NBR), and neoprene, respectively.

[0142] Preferably, the major elastomer is chosen from the group consisting of polybutadienes (BR), butadiene-styrene copolymers (SBR), natural (NR) or synthetic (IR) polyisoprenes, nitrile-butadiene copolymers (NBR), chloroprene copolymers (e.g. neoprene) and mixtures of these elastomers.

[0143] The term "composition based on" refers to a composition comprising a mixture and / or the in situ reaction product of the various basic constituents used, some of which may react and / or are intended to react with each other, at least partially, during the various stages of manufacturing the composition, or during subsequent cooking, thereby modifying the composition as initially prepared. Thus, the compositions implemented for the invention may differ in their uncrosslinked and crosslinked states.

[0144] Conveyor belt manufacturing

[0145] We will now describe a manufacturing process for a conveyor belt. Such a process typically begins with the provision of a core comprising the carcass steel cables encased in a first elastomeric layer. The carcass cables extend in a longitudinal direction along the belt.

[0146] A second step is the preparation of the reinforcement layer. For this purpose, open reinforcing cables are arranged parallel to each other in a plane. Each open reinforcing cable comprises a plurality of helically wound metallic monofilaments, thus defining an internal arch within the cable. The cables are then embedded in an elastomeric matrix so that each monofilament of each cable is embedded within the matrix. To achieve this embedding, the cables are typically pressed between two layers of pre-calendered elastomeric material. The elastomeric material layers are unvulcanized and deform plastically during pressing. In this way, the elastomeric material completely fills the space between and within the cables.

[0147] During this step, the internal vault of each respective cable is also filled with the elastomeric material of the matrix.

[0148] The open reinforcement cables and the matrix are subsequently cut into a plurality of plies. Each ply has, in a longitudinal direction of the reinforcement cables, a length L corresponding to 95% to 100% of the conveyor belt width. The plies are then placed side by side to form a reel with a width corresponding to 95% to 100% of the conveyor belt width, with the cables arranged transversely.

[0149] Preferably, the tablecloths are rectangular in shape.

[0150] Following this step, part of the upper surface of the web is covered with reinforcement layers, so that the open reinforcing cables within the layers are positioned transversely to the conveyor belt. If necessary, the underside of the same section of the belt can also be covered with reinforcement layers.

[0151] Typically, the matrices are cross-linked, for example vulcanized, only after the reinforcement plies and the core of the strip have been assembled. After the core and reinforcement layers are laid on top of each other, all the layers are pressed together, resulting in initial bonding due to the natural adhesion of the elastomeric matrices. The plies stacked on the core are typically vulcanized under appropriate pressure and curing temperature. Cross-linking is carried out on the stack in several sections, for example, ten meters long.

[0152] The coating, curing, and pressing steps are repeated on subsequent sections until cross-linking is achieved, preferably vulcanizing the core and reinforcing layer along the entire length of the strip. The elastic material within the core of each reinforcing cable is cross-linked with the elastomeric matrices of the respective core and reinforcing layer.

[0153] When the core is fully covered with reinforcing plies, a coating, for example of an elastic material, can be applied to the top and / or bottom surface of the conveyor belt. Typically, such coatings are applied before the belt is cross-linked and cross-linked together with the core and reinforcing plies. REFERENCES

[0154] FR3099191A1

Claims

DEMANDS 1. Conveyor belt (100) comprising: o a core (10) comprising carcass steel cables (11) extending in a longitudinal direction of the belt (100), said carcass steel cables (11) being embedded in a first elastomeric matrix (15) and o a reinforcing layer (20) covering at least partially the upper face of the core (10), said reinforcing layer comprising • a plurality of reinforcing metal cables (21) arranged parallel to each other in a transverse direction of the strip, each reinforcing cable (21) comprising a plurality of metallic monofilaments (23) wound helically around an arch, each reinforcing cable having a total elongation at break greater than 8%, the total elongation at break being measured in accordance with ASTM D 2969-00, and • a second elastomeric matrix (25) coating the monofilaments (23).

2. Conveyor belt (100) according to claim 1, wherein each carcass cable (11) has a total elongation at break of less than 4%, the total elongation at break being measured according to ASTM D 2969-00.

3. Conveyor belt (100) according to claim 1 or claim 2, wherein each carcass cable (11) has a total elongation at break of between 1% and 3%, preferably between 2% and 3%, the total elongation at break being measured according to ASTM D 2969-00.

4. Conveyor belt (100) according to any one of claims 1 to 3, wherein each carcass cable (11) is a multi-strand cable, each strand comprising several metallic monofilaments.

5. Conveyor belt (100) according to claim 4, in which each metallic monofilament has a mechanical resistance between 1000 MPa and 5000 MPa.

6. Conveyor belt (100) according to any one of the preceding claims, comprising a plurality of reinforcing plies (20) juxtaposed in a single thickness on an upper face of the web (10) in a longitudinal direction of the belt (100).

7. Conveyor belt (100) according to any one of the preceding claims, wherein the distance (D r ) between two adjacent reinforcing cables (21) is less than or equal to 4 mm, preferably 2.2 mm.

8. Conveyor belt (100) according to any one of the preceding claims, wherein each reinforcing cable (21) has a monofilament diameter Df and a helix radius Rf such that: 9 < Rf / Df < 30, and the arch is defined by a cylinder radially internal and tangent to each monofilament, said cylinder having an arch diameter D v such that 1.30 < D v / Df < 4.

5.

9. Conveyor belt (100) according to any one of the preceding claims, wherein each reinforcing cable (21) comprises between 3 and 10 monofilaments (23), preferably 5 monofilaments.

10. Conveyor belt (100) according to any one of the preceding claims, wherein each monofilament (23) has a diameter Df between 0.1 and 0.5, preferably 0.35 mm.

11. Conveyor belt (100) according to any one of the preceding claims, wherein each reinforcing cable (21) has an external diameter of between 0.9 and 2.1, preferably 1.9 mm, and / or an internal arch diameter of between 0.4 and 1.3, preferably 1.2 mm.

12. Conveyor belt (100) according to any one of the preceding claims, wherein the reinforcing cables (21) extend over a width less than or equal to the width of the conveyor belt (100), preferably between 95% and 100% of the width of the conveyor belt.

13. Conveyor belt (100) according to any one of the preceding claims, further comprising an upper coating and / or a lower coating of elastomeric matrix.

14. Conveyor belt (100) according to any one of the preceding claims further comprising at least one reinforcing layer (20) arranged on an underside face of the web.

15. Method for manufacturing a conveyor belt (100), comprising o providing a core comprising carcass metal cables (11) extending in a longitudinal direction of the belt (100), said metal cables (11) being coated in a first elastomeric matrix (15); o providing a plurality of reinforcement cables (21), each reinforcement cable (21) comprising a plurality of metallic monofilaments (23) wound helically around an arch, each reinforcement cable having a total elongation at break greater than 8%, the total elongation at break being measured according to ASTM D 2969-00; o arranging the reinforcement cables (21) in a parallel manner in a plane; o the coating of all the reinforcing cables (21) in an elastomeric matrix (25) so that each monofilament (23) is coated in the elastomeric matrix (25);o the covering of the upper face of the core by a plurality of reinforcing layers (20) in the longitudinal direction of the strip (100), the reinforcing cables (21) extending in a transverse direction of the strip (100).; 16. Method according to claim 15, further comprising covering the underside of the core with a plurality of reinforcing layers (30).

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