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 conveyor belt (100), the metal carcass cords (11) being coated in a first elastomeric matrix (15); o a first reinforcing layer (20) arranged above the core, the first reinforcing layer comprising a textile fabric and / or metal cords extending in a transverse direction of the conveyor belt (100) and a second elastomeric matrix (25) coating the fabric and / or the metal cords; and o a second reinforcing layer (30) placed above the first reinforcing layer (20), the second reinforcing layer (30) comprising a plurality of metal reinforcing cords (31) which are wavy in the plane of the conveyor belt (100) and are arranged in parallel in a longitudinal direction of the conveyor belt (100), and a third elastomeric matrix (35) coating the reinforcing cords (31).

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 a rubber 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, particularly when impacted by very sharp objects such as dolerite or slate.

[0011] Other types of reinforcement include transverse wire cables held in place by longitudinal metal or textile binding threads, for example, made of polyamide or polyester. Wire cable-based protective reinforcements typically have higher breaking strength than textile reinforcements. However, wire cables are less flexible than textile reinforcement and therefore cannot gather at the bottom of a crack to create a thicker reinforcement in that position. Furthermore, such reinforcements significantly increase the flexural stiffness of the conveyor belt.

[0012] DESCRIPTION OF THE INVENTION

[0013] One aim of the invention is to design a conveyor belt exhibiting improved resistance to breakage, allowing deformation to create a thicker reinforcement at the bottom of any crack, while retaining sufficient flexibility for transverse bending of the belt on the rollers.

[0014] To this end, the invention proposes a conveyor belt comprising: o a core comprising carcass metal cables extending in a longitudinal direction of the conveyor belt, said carcass metal cables being coated in a first elastomeric matrix; o a first reinforcement layer arranged above the core, said first reinforcement layer comprising a textile fabric and / or metal cables extending in a transverse direction of the conveyor belt and a second elastomeric matrix coating said fabric and / or the metal cables; and o a second reinforcement layer disposed above the first reinforcement layer, said second reinforcement layer comprising a plurality of corrugated metal reinforcement cables in the plane of the conveyor belt, arranged parallel to each other in a longitudinal direction of the conveyor belt, and a third elastomeric matrix coating the reinforcement cables.

[0015] Depending on other advantageous but optional features, taken separately or in combination:

[0016] - the distance between the centers of two adjacent corrugated metal reinforcement cables is less than or equal to four times the diameter of each corrugated metal reinforcement cable, preferably twice the diameter of each reinforcement cable; - the amplitude of the corrugation of the reinforcement cables is between 3 and 8 mm, preferably 5.5 mm;

[0017] - the wavelength of the reinforcement cables is between 10 and 20 mm, preferably 14.5 mm;

[0018] - the ratio between the ripple amplitude and the ripple period is greater than or equal to 0.3;

[0019] - the reinforcement cables cover a central portion of the conveyor belt with a width greater than 30% of the width of the conveyor belt;

[0020] - the reinforcement layer (30) comprises a plurality of reinforcement layers juxtaposed in a single thickness on an upper face of the core in a transverse direction of the conveyor belt, each reinforcement layer comprising corrugated metal reinforcing cables in the plane of the conveyor belt embedded in an elastomeric matrix;

[0021] - the width of each reinforcement layer is between 100 and 350 mm;

[0022] - each reinforcing cable comprises between 1 and 26 metallic monofilaments;

[0023] - the diameter of the reinforcing cables (31) is between 0.18 mm and 2 mm;

[0024] - the conveyor belt further includes a third layer of reinforcement arranged below the core, said third layer of reinforcement comprising a textile fabric and / or metal cables extending in a transverse direction of the conveyor belt and an elastomeric matrix encasing said fabric and / or metal cables;

[0025] - the conveyor belt further includes a top coating and / or a bottom coating of an elastomeric material.

[0026] 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 conveyor belt, said carcass metal cables being coated in a first elastomeric matrix; o applying a first reinforcement layer above the core, said first reinforcement layer comprising a textile fabric and / or metal cables extending in a transverse direction of the conveyor belt and a second elastomeric matrix coating said fabric and / or the metal cables; o deforming a sheet comprising parallel metal cables so that the cables form corrugations, said cables being coated in a third elastomeric matrix; o realigning the corrugated metal cables so that the corrugations are arranged in a plane;o the covering of the upper face of the first reinforcement layer by the second reinforcement layer, so that the corrugated metal cables extend in a longitudinal direction of the conveyor belt.;

[0027] The said process may further include the application of a third layer of reinforcement on an underside of the core, said third layer of reinforcement comprising a textile fabric and / or metal cables extending in a transverse direction of the conveyor belt and an elastomeric matrix encasing said fabric and / or metal cables.

[0028] The covering of the upper face of the first reinforcement layer may include the laying of at least two reinforcement layers comprising identical corrugated metal cables parallel in a longitudinal direction of the conveyor belt.

[0029] BRIEF DESCRIPTION OF THE FIGURES

[0030] Other features and advantages will become apparent from the detailed description that follows, with reference to the attached drawings, on which:

[0031] - Figure 1 is a perspective view of a portion of a conveyor belt according to the invention;

[0032] - Figure 2A illustrates a first embodiment of the arrangement of monofilaments in a core cable;

[0033] - Figure 2B illustrates a second embodiment of the arrangement of monofilaments in a core cable;

[0034] - Figure 3 illustrates a first layer of reinforcement comprising a polyamide fabric;

[0035] - Figure 4 illustrates a first layer of reinforcement comprising transverse metal cables;

[0036] - Figure 5 is a perspective view of the core cables and reinforcement structures of a conveyor belt according to the invention;

[0037] - Figure 6A is a top view of the cables and wires present in a conveyor belt;

[0038] - Figure 6B is a cross-sectional view of the cables and wires in Figure 6A;

[0039] - Figure 60 is a longitudinal cross-sectional view of the cables and wires in Figure 6A.

[0040] - Figure 7 is a detailed view of the second reinforcement layer of Figure 6A;

[0041] - Figure 8 illustrates the geometry of the corrugated cables.

[0042] For the sake of clarity, the illustrated elements are not necessarily drawn to scale. DETAILED DESCRIPTION OF IMPROVEMENT METHODS

[0043] In this text, the terms "vertical", "horizontal", "upper", "lower" are understood to refer to the position of an object transported on the belt oriented in the direction of transport.

[0044] 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. The carcass wires 11 are the main wires of the conveyor belt and extend in a longitudinal direction I corresponding to the direction of belt circulation. By way of illustration and without limitation, the carcass wires 11 are typically multi-strand wire ropes, each strand comprising several monofilaments. Preferably, the monofilaments are arranged helix and the strands are arranged helix. "Metallic" is understood to mean a material consisting of at least 50% of its mass of a metallic material.

[0045] 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. Alternatively, with reference to Figure 2B, carcass cables 11B may, for example, comprise seven strands 12 of nineteen monofilaments 13 per strand 12. Such cables typically have a diameter between 4 and 14 mm.

[0046] The monofilaments of carcass cables are, for example, made of steel, preferably pearlitic steel or carbon ferritic-pearlitic steel, or stainless steel containing at least 10.5% chromium. These monofilaments may have a coating comprising copper, zinc, tin, cobalt, or an alloy of these metals, for example, brass or bronze. Each individual metallic monofilament typically has a mechanical strength of 1000 MPa to 5000 MPa.

[0047] The mechanical resistance measurement is carried out according to the ASTM D 2969 - 00 standard on a metal cable intended for tire reinforcement.

[0048] The initial cross-section of the wire rope (So) is determined upstream of a tensile measurement.

[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 mThe elongation of the wire rope and the force exerted during stretching are measured. Stretching is measured with a mechanical extensometer that remains in contact with the wire rope during the procedure. The rope is held by clamps that allow for stretching until the rope breaks outside the clamp's gripping zone. Clamps with a gradual curve are therefore preferred.

[0050] 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).

[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] Maximum mechanical resistance R m is determined from the maximum force

[0055] F m and the initial section of the test specimen So according to R m [MPa] =

[0056] S o [îîlîîl J

[0057] The carcass cables 11 are arranged parallel to each other and coated with a first elastomeric matrix 15. The distance between the centers of two carcass cables 11 D a is typically between 10 and 19 cm.

[0058] The conveyor belt includes at least a first reinforcement layer 20 arranged above the core 10. With reference to Figure 3, the first reinforcement layer 20 includes an internal structure such as a textile fabric and / or transverse metal cables, and a second elastomeric matrix 25 encasing said fabric and / or metal cables.

[0059] The internal fabric structures 23 comprise at least one longitudinal multifilament strand 22 of aromatic polyamide or aromatic copolyamide, aliphatic polyamide or polyester and have a density of up to 1.6 kg / m² 2 .

[0060] By aromatic polyamide multifilament strand or aromatic copolyamide, it is well known that it is a filament of linear macromolecules formed of aromatic groups linked together by amide bonds of which at least 85% are directly linked to two aromatic nuclei, and more particularly of poly (p-phenylene terephthalamide) (or PPTA) fibers, manufactured for a very long time from optically anisotropic spinning compositions. Among the aromatic polyamides or aromatic copolyamides, we can mention polyarylamides (or PAA, notably known under the trade name Ixef from the company Solvay), poly(metaxylylene adipamide), polyphthalamides (or PPA, notably known under the trade name Amodel from the company Solvay), or para-aramids (or poly(paraphenylene terephthalamide or PA PPD-T notably known under the trade name Kevlar from the company Du Pont de Nemours or Twaron from the company Teijin).

[0061] A multifilament strand of aliphatic polyamide is defined as a filament of linear macromolecules of polymers or copolymers containing amide groups without aromatic rings, and which can be synthesized by polycondensation between a carboxylic acid and an amine. Examples of aliphatic polyamides include nylons PA4.6, PA6, PA6.6, and PA6.10, notably Zytel from DuPont, Technyl from Solvay, and Rilsamid from Arkema.

[0062] A multifilament polyester strand is a filament of linear macromolecules formed from groups linked together by ester bonds. Polyesters are manufactured by polycondensation through esterification between a dicarboxylic acid or one of its derivatives and a diol. For example, polyethylene terephthalate can be manufactured by the polycondensation of terephthalic acid and ethylene glycol. Among the known polyesters are polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polybutylene naphthalate (PBN), polypropylene terephthalate (PPT), and polypropylene naphthalate (PPN).

[0063] Fabrics containing such strands are designed to absorb and dissipate impact energy. The yarns in such fabrics are adapted to stop cracking in the event of a puncture by a penetrating object, thus more effectively limiting damage to the conveyor belt. Textile reinforcements typically have an elongation at break of 15 to 25%. It should be noted that the impact protection is primarily due to the transverse yarns 21 of the fabric. In these fabrics, the pitch d2 of the transverse yarns 21 is between 2 and 4 mm. Pitch refers to the distance between the centers of two adjacent yarns or strands. The tensile strength of the transverse yarns 21 of a polyamide fabric is typically on the order of 0.5 to 1 kN. The tensile strength of the fabric 23 in the transverse direction is between 125 and 800 N / mm.

[0064] When the internal structure includes wire ropes, as shown in Figure 4, the wire ropes 26 extend in the transverse direction to maintain the belt's bend in the longitudinal direction. In this case, the first reinforcement layer also includes textile yarns 27 extending in the longitudinal direction. These textile yarns 27 are typically made of polyamide or polyester and help to hold the transverse wire ropes 26 in position. The transverse wire ropes 26 used usually have an elongation at break of approximately 4–8%. The distance between the centers of two adjacent transverse wire ropes 26 is preferably between 4 and 20 mm. As shown in Figures 1 and 5, the conveyor belt includes a second reinforcement layer 30 arranged above the first reinforcement layer 20.Preferably, with reference to Figure 6A, the second reinforcement layer 30 completely covers a central portion of the belt with a width LR greater than 30% of the conveyor belt width. Typically, the central portion of the belt covered by the second reinforcement layer 30 has a width corresponding to between 30% and 50% of the conveyor belt width LB. Thus, the second reinforcement layer 30 covers the area where impacts are most frequent during loading onto the conveyor belt.

[0065] The second reinforcing layer 30 comprises a plurality of metallic reinforcing cables 31. Metallic is defined as a material consisting of at least 50% of its mass of a metallic material. The reinforcing cables are embedded in an elastomeric matrix 35.

[0066] By way of illustration and not limitation, reinforcement cables are monofilament cables or single-strand cables.

[0067] Preferably, the reinforcing cables are identical. Each reinforcing cable typically comprises between 1 and 26 metallic monofilaments. The monofilaments can have a diameter between 0.18 and 0.45 mm in both monofilament and single-strand cables. For example, the reinforcing cables could be single-strand cables comprising four monofilaments with a diameter of 0.23 mm.

[0068] 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 rope and / or the conveyor belt 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.

[0069] Referring to Figure 7, the reinforcing cables 31 are corrugated in the plane of the strip. In other words, the reinforcing elements are arranged between two parallel planes separated by approximately the diameter of the reinforcing cables 31, these two planes being parallel to the plane of the strip.

[0070] By corrugation, we mean that the cables follow a regular sinusoidal or sawtooth pattern with or without clipped crests. The corrugation of the cables prevents an increase in the rigidity of the conveyor belt due to the presence of the reinforcement layer 30. The orientation of this corrugation in the plane of the protective layer limits the thickness of the reinforcement layer 30 and thus limits the thickness of the conveyor belt.

[0071] A layer of corrugated cables in the plane is described for example in FR2518462 and FR2518463.

[0072] The reinforcing cables 31 are arranged parallel to each other along the longitudinal direction of the conveyor belt, meaning that the corrugations of all the reinforcing cables 31 are in phase. This arrangement allows the corrugated cables to be placed at maximum density within the plane of the conveyor belt. The high density of corrugated metal cables provides very effective protection against even the most severe cutting impacts. This level of protection is particularly high compared to textile reinforcement layers.

[0073] The reinforcing cables 31 preferably have a diameter between 0.18 mm and 2 mm. The distance D r The distance between the centers of two adjacent reinforcing cables 31 is less than or equal to four times the diameter d of each reinforcing cable, preferably close to twice the diameter of each reinforcing cable. For example, in the case of a diameter d of the reinforcing cables of 0.54 mm, the distance D rthe distance between the centers of two adjacent 31 reinforcement cables can be approximately 1 mm.

[0074] The distance D r between the centers of two adjacent reinforcing cables 31 is typically such that d + 0.2 mm < D r < 2d.

[0075] Figure 8 schematically illustrates the geometry of parallel corrugated cables. The amplitude A is defined as the distance between a crest of maximum 38' and a crest of minimum 38' in a direction perpendicular to the principal axis X of the corrugated cable. The amplitude A of the corrugation of the reinforcing cables 31 is typically between 3 and 8 mm, for example, 5.5 mm.

[0076] The wavelength X corresponds to the distance between two maxima of ripple. Typically, the wavelength X is between 10 and 20 mm, for example 14.5 mm.

[0077] The elongation capacity of the entire corrugated cable assembly depends on the ratio between the amplitude A and the wavelength X. Preferably, the cables exhibit an elongation of at least 20% in the direction of the conveyor belt, which corresponds to the typical elongation at break of the longitudinal wires of the first reinforcement layer 20, which provide the belt's mechanical strength and are, for example, made of polyamide. The ratio between the corrugation amplitude A and the wavelength X is advantageously greater than or equal to A / X = 0.3 in order to achieve such an elongation of 20% in the second reinforcement layer. An elastomeric matrix 35 encases the reinforcement cables 31. The spaces between the reinforcement cables 31 are thus filled with elastomeric material. The space between two respective layers, in particular between the wires and / or cables of the first reinforcement layer 20 and the second reinforcement layer 30, is also filled with an elastomeric material.The elastomeric material arranged between the cables of two respective layers thus forms a decoupling layer separating the wires and / or cables of the first reinforcement layer 20 and the cables of the second reinforcement layer 30. This decoupling layer consists of the elastomeric material of the first reinforcement layer and the second reinforcement layer 30. The total thickness of the elastomeric material of the decoupling layer is between 0.2 mm and 3 mm, preferably between 0.5 mm and 1.5 mm.

[0078] In some embodiments (not shown), the second reinforcement layer consists of several reinforcement plies, each with a width less than the second reinforcement layer 30. In this case, each conveyor ply comprises parallel corrugated reinforcement cables. The waviness amplitude A and the wavelength X are identical for all reinforcement plies within the same reinforcement layer. The reinforcement plies are placed side-by-side along the longitudinal direction of the strip in a single, parallel thickness, with adjacent plies placed as close together as possible. The cable waviness in two adjacent reinforcement plies is therefore in phase.

[0079] With reference to Figure 6B and Figure 6C, the conveyor belt may further include a third reinforcing layer 40. The third reinforcing layer 40 is arranged below the core 10 of the conveyor belt. The third reinforcing layer 40 comprises an internal structure such as a textile fabric and / or metal cables extending in a transverse direction of the belt and an elastomeric matrix 45 encasing said fabric and / or metal cables.

[0080] The presence of the third reinforcement layer 40 increases the symmetry of the conveyor belt reinforcements and can thus improve the conveyor belt's flexural behavior during use. The same types of internal structures described above for the first reinforcement layer are generally used. The third reinforcement layer 40 may be identical to the first reinforcement layer 20 or have a different composition and / or arrangement.

[0081] As illustrated in Figure 1, the conveyor belt may have a coating 50, for example of an elastic material, on its upper face and / or on its lower face.

[0082] The first elastomeric matrix 15, the matrices 25, 35, 45 of the reinforcing layers, and an 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 co-vulcanization of several layers.

[0083] The compounds in the elastomeric matrices and the coating 50 can be of fossil origin or bio-based. In the latter case, they can be partially or entirely 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 entirely produced through 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.

[0084] The compositions of the elastomeric matrices according to the invention and of the coating are based on at least one elastomer, a reinforcing filler, a crosslinking system.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] The elastomer can be chosen from the group consisting of diene elastomers and mixtures thereof.

[0093] 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).

[0094] 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%.

[0095] 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:

[0096] (a) any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms;

[0097] (b) any copolymer obtained by copolymerization of one or more dienes conjugated together or with one or more aromatic vinyl compounds having 8 to 20 carbon atoms;

[0098] (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;

[0099] (d) a copolymer of isobutene and isoprene (butyl rubber), as well as halogenated versions, in particular chlorinated or brominated, of this type of copolymer.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] We will now describe a manufacturing process for a conveyor belt. Such a process typically begins with the provision of a core comprising steel carcass cables embedded in a first elastomeric matrix. The carcass cables extend in a longitudinal direction along the belt.

[0107] The first layer of reinforcement and, where applicable, the third layer of reinforcement, are applied in a manner commonly known to those skilled in the art.

[0108] To prepare the second reinforcement layer, straight metal reinforcing cables are placed between two layers of calendered and pressed rubber. Typically, a composite comprising metal reinforcing cables encased in an elastomeric material to form the second reinforcement layer is supplied as a reel and is subsequently processed to manufacture the reinforcement layer. The cables then undergo plastic deformation to achieve a corrugated shape. Advantageously, this deformation is achieved by passing the straight cables, surrounded by the rubber layers, between two serrated cylinders.

[0109] After deformation, the metal cables are reoriented to align the undulations with the plane of the layer so that the cable undulations are in phase. During this step, the elastomeric matrix 35 is not yet cross-linked and follows the reorientation of the cables. The composite consisting of the cables and the elastomeric matrix 35 is thus flattened, and the interstitial spaces between the cables are filled with the elastomeric material.

[0110] The width of the cable arrangement corresponds to the intended width of the reinforcement layer to be manufactured, for example, between 30% and 50% of the width of the conveyor belt to be manufactured. In some embodiments, the width corresponds to the width of a layer to be placed alongside other layers. In this case, the width of the cable arrangement is equal to a fraction of the width of the reinforcement layer to be manufactured. Typically, the width of such a fraction is between 100 and 350 mm, which facilitates the manufacturing and handling of the second reinforcement layer and allows for sufficiently complete belt coverage.

[0111] The corrugated metal cables are thus coated in the elastomeric matrix 35 and form a reinforcing layer.

[0112] Following this step, the reinforcement layer is placed on a central portion of the web containing the first reinforcement layer and, if applicable, the third reinforcement layer. In the case of multiple layers whose width is a fraction of the width of the second reinforcement layer, these layers are placed side-by-side in a single thickness on the central portion of the web, parallel to each other, minimizing the space between the respective adjacent layers.

[0113] The reinforcing plies are then bonded to the first reinforcing layer to form the conveyor belt. The elastomeric material is brought to its solid state by cross-linking, for example, by vulcanization. Typically, elastomeric matrices 15, 25, and 35 are cross-linked, for example, vulcanized, only after the reinforcing layers and the belt core have been assembled. After the core and reinforcing layers are superimposed, the layers are pressed together, resulting in initial bonding due to the natural adhesion of the elastomeric matrices. Cross-linking, particularly vulcanization, is carried out in several sections, for example, ten meters long. The elastomeric material of all layers is cross-linked together in a single step per section. Each section is mechanically pressed to fix the reinforcing plies. Heat treatment can also be applied to the section during mechanical pressing.This procedure is repeated until the reinforcement layer is glued along the entire length of the conveyor belt.

[0114] After the application of the second reinforcing layer, a coating, for example made of an elastomeric material such as rubber, 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.

[0115] REFERENCES

[0116] FR2518462

[0117] FR2518463

Claims

DEMANDS 1. Conveyor belt (100) comprising: o a core (10) comprising carcass metal cables (11) extending in a longitudinal direction of the conveyor belt (100), said carcass metal cables (11) being encased in a first elastomeric matrix (15); o a first reinforcement layer (20) arranged above the core, said first reinforcement layer comprising a textile fabric and / or metal cables extending in a transverse direction of the conveyor belt (100) and a second elastomeric matrix (25) encasing said fabric and / or metal cables;and a second reinforcement layer (30) disposed above the first reinforcement layer (20), said second reinforcement layer (30) comprising a plurality of corrugated metallic reinforcement cables (31) in the plane of the conveyor belt (100), arranged parallel to each other in a longitudinal direction of the conveyor belt (100), and a third elastomeric matrix (35) encasing the reinforcement cables (31).

2. Conveyor belt (100) according to claim 1, wherein the distance (D r ) between the centers of two adjacent corrugated metal reinforcing cables (31) is less than or equal to four times the diameter of each corrugated metal reinforcing cable (31), preferably twice the diameter of each reinforcing cable.

3. Conveyor belt (100) according to claim 1 or claim 2, wherein the amplitude of undulation (A) of the reinforcing cables (31) is between 3 and 8 mm, preferably 5.5 mm.

4. Conveyor belt (100) according to any one of the preceding claims, wherein the wavelength (X) of the reinforcing cables (31) is between 10 and 20 mm, preferably 14.5 mm.

5. Conveyor belt (100) according to any one of the preceding claims, wherein the ratio between the amplitude of the waviness (A) and the period of the waviness (X) is greater than or equal to 0.

3.

6. Conveyor belt (100) according to any one of the preceding claims, wherein the reinforcing cables (31) cover a central portion of the conveyor belt (100) having a width (LR) greater than 30% of the width of the conveyor belt (100).

7. Conveyor belt (100) according to any one of the preceding claims, wherein the reinforcement layer (30) comprises a plurality of reinforcement plies juxtaposed in a single thickness on an upper face of the core (10) in a transverse direction of the conveyor belt (100), each reinforcement ply comprising reinforcing cables (31) of corrugated metal in the plane of the conveyor belt (100) embedded in an elastomeric matrix (35).

8. Conveyor belt (100) according to claim 7, wherein the width of each reinforcement layer (33) is between 100 and 350 mm.

9. Conveyor belt (100) according to any one of the preceding claims, wherein each reinforcing cable (31) comprises between 1 and 26 metallic monofilaments.

10. Conveyor belt (100) according to any one of the preceding claims, wherein the diameter of the reinforcing cables (31) is between 0.18 mm and 2 mm.

11. Conveyor belt (100) according to any one of the preceding claims, further comprising a third reinforcement layer (40) arranged below the core (10), said third reinforcement layer (40) comprising a textile fabric and / or metal cables extending in a transverse direction of the conveyor belt (100) and an elastomeric matrix (45) encasing said fabric and / or metal cables.

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

13. Method for manufacturing a conveyor belt (100), comprising o providing a core (10) comprising carcass metal cables (11) extending in a longitudinal direction of the conveyor belt (100), said carcass metal cables (11) being coated in a first elastomeric matrix (15); o the application of a first reinforcement layer (20) above the core (10), said first reinforcement layer (20) comprising a textile fabric and / or metal cables extending in a transverse direction of the conveyor belt (100) and a second elastomeric matrix (25) coating said fabric and / or metal cables; o the deformation of a sheet comprising parallel metal cables (31) so that the cables form undulations, said cables being coated in a third elastomeric matrix (35); o the realignment of the corrugated metal cables (31) so that the undulations are arranged in a plane;o the covering of the upper face of the first reinforcement layer (20) by the second reinforcement layer (30), so that the corrugated metal cables (31) extend in a longitudinal direction of the conveyor belt (100).; 14. Method according to claim 13, further comprising the application of a third reinforcement layer (40) on an underside face of the core (10), said third reinforcement layer comprising a textile fabric and / or metal cables extending in a transverse direction of the conveyor belt (100) and an elastomeric matrix encasing said fabric and / or metal cables.

15. Method according to claim 13 or claim 14, wherein the covering of the upper face of the first reinforcement layer (20) comprises laying at least two reinforcement layers comprising identical corrugated metal cables (31) in parallel in a longitudinal direction of the conveyor belt (100).

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