Transmission belt comprising two superimposed layers of reinforcers embedded in a matrix, and method for assembling said belt

Abstract

Disclosed is a transmission belt (10) comprising a body (11) extending in a longitudinal direction (X), comprising a main portion (12c) and two end portions (12a, 12b) each extending from one end of the main portion (12c), produced in a matrix delimited by two end portions (12a, 12b), said transmission belt (10) being configured to transition from an initial state, in which the end portions (12a, 12b) are free, to an assembled state in which the end portions (12a, 12b) are secured to each other. Each of the end portions (12a, 12b) comprises at least one layer of reinforcing elements embedded in said body, and having a contact surface (17, 18) each. At least the contact surfaces (17, 18) are made of thermoplastic elastomer. The reinforcing elements (14a, 14b) extend in the form of two reinforcing layers superimposed in a transverse direction (Y) in the thickness of the matrix (12) when the belt is in the assembled state.

Description

[0001] DESCRIPTION

[0002] TITLE: Transmission belt comprising two superimposed layers of reinforcements embedded in a matrix and method of assembling said belt

[0003] The present invention relates to the field of transmission of drive forces, more particularly transmission belts, in particular synchronous belts.

[0004] The present invention may also relate to rubber tracks for agricultural, military, public works and leisure vehicles (snowmobiles, motorcycles, etc.)

[0005] A belt is presented, in a manner known per se, in the form of a closed band capable of transmitting the forces from a driving pulley to a driven pulley, preferably synchronously.

[0006] Installing a new belt is quite complex and usually requires dismantling various parts of the machine, which results in the consumption of resources and time.

[0007] To overcome this disadvantage, it is known to produce an open belt that can be easily installed and closed at the installation site, for example by gluing.

[0008] However, bonding requires the supply of material to the installation site.

[0009] Such belts are commonly referred to as "welding belts".

[0010] Furthermore, when gluing or welding is performed with the end portions of the belt overlapping, the bending stiffness of the belt is increased locally, and the neutral fiber is displaced. This creates a non-uniformity that can disrupt the operation of the belt.

[0011] There are belts with inlet and outlet zones cut into the belt and then glued to the vertical walls of the cutouts. The neutral fiber remains stable. However, such a solution is particularly complex.

[0012] The aim of the invention is to provide an improved belt, or an improved track, which is easy to manufacture and install on the installation site and which still allows a neutral fiber to be maintained.

[0013] The subject of the invention is a transmission belt or a track comprising a body extending in a longitudinal direction, comprising a main portion and two end portions each extending from one end of the main portion, and produced in a matrix and delimited by two end portions.

[0014] Said transmission belt is configured to pass from an initial, unassembled state, in which the end portions are free, to an assembled state in which the end portions are secured to one another via a contact surface.

[0015] Each of the end portions comprises at least one layer of reinforcing elements embedded in said body and a contact surface.

[0016] At least the contact surfaces are made of thermoplastic elastomer.

[0017] The reinforcing elements extend in at least two superimposed reinforcing layers in a transverse direction in the thickness of the matrix in the assembled state of the belt.

[0018] Generally, each end portion has the same number of reinforcement layers.

[0019] In other words, the transmission belt is a so-called "open" belt, that is, it is stored in an initial unassembled state and is configured to be installed in a complex mechanical environment requiring its assembly directly at the installation site.

[0020] Each reinforcement layer is embedded in the matrix, that is to say surrounded by the matrix.

[0021] According to the invention, the superposition of the two end portions makes it possible to maintain a neutral sheet (also commonly called a sheet of "neutral fibers") at the same transverse position at the junction zone as in the rest of the body of the transmission belt.

[0022] For example, each layer of reinforcing element comprises a plurality of reinforcing elements parallel to each other in a vertical direction.

[0023] Advantageously, each reinforcement layer has a transverse dimension, i.e. a thickness, of between 0.1 mm and 7 mm.

[0024] According to one embodiment, the contact surfaces are located transversely between the two reinforcement layers.

[0025] Advantageously, the end portions have a thickness less than the total thickness of the matrix.

[0026] According to one embodiment, one of the end portions comprises a first section having a thickness less than the total thickness of the body of the belt and a single external reinforcing layer and the other of the end portions comprises a second section having a thickness less than the total thickness of the body of the belt and a single internal reinforcing layer. In the assembled state of the belt, the internal surface of the first section is superimposed transversely on the external surface of the second section so that the sheet of neutral fibers of the belt is at the same transverse position at the main portion and at the end portions when the belt is in the assembled state of the belt.

[0027] In other words, the internal reinforcing layer of one of the end portions is opposite in the longitudinal direction the internal reinforcing layer of the other of the end portions and the external reinforcing layer of one of the end portions is opposite in the longitudinal direction the external reinforcing layer of the other of the end portions.

[0028] In fact, one of the end portions is composed of a first section of the belt and the other of the end portions is composed of a second section of the belt. The joining of the end portions makes it possible to superimpose the first and second sections of the belt and to reconstitute the belt in the assembled state. In other words, the internal surface of one of the end portions is offset transversely outwardly relative to the internal surface of the die and the external surface of the other of the end portions is offset transversely inwardly relative to the external surface of the die.

[0029] In the assembled state of the belt, the inner surface of the first section forms an inner contact surface and the outer surface of the second section forms an outer contact surface. Said contact surfaces are intended to come into contact along the transverse axis perpendicular to the belt when the belt is in the assembled state. Said contact surfaces are parallel or slightly inclined relative to the extension axis of the belt.

[0030] According to one embodiment, the matrix is ​​made of a first thermoplastic elastomer material and the internal surface of one of the end portions forms a first contact surface and the external surface of the other of the end portions forms the second contact surface, said contact surfaces being configured to be integral or assembled with each other, for example during a heat welding step, in the assembled state of the transmission belt.

[0031] Advantageously, the end portions of the transmission belt in the free state are configured to be assembled at a junction zone, by bringing the first section and the second section into contact together in a direction perpendicular to the direction of extension of the belt, then by connecting the end portions by applying a pressure of between 0.1 bar and 20 bar and heat, in particular a temperature of between 80°C and 200°C, preferably between 120°C and 200°C.

[0032] According to another embodiment, the matrix is ​​made of a second non-thermoplastic elastomer material and the internal surface of one of the end portions is coated at least in part with an internal bonding layer crosslinked only locally at the interface with the elastomer matrix and the external surface of the other of the end portions is coated at least in part with an external bonding layer crosslinked only locally at the interface with the elastomer matrix, said bonding layers being made of a third thermoplastic elastomer material and configured to be secured or assembled to one another, in particular during a heat-welding step, in the assembled state of the transmission belt.

[0033] Advantageously, the end portions of the transmission belt in the free state are configured to be assembled at a junction zone, by bringing the connecting layers into contact together in a direction perpendicular to the direction of extension of the belt, then by bonding between said connecting layers by applying a pressure of between 0.1 bar and 20 bar and heat, in particular a temperature of between 80°C and 200°C, preferably between 120°C and 200°C.

[0034] The terms "outer" and "inner" are defined in terms of the center of the drive belt, with the outer surfaces being further apart than the inner surfaces.

[0035] The bonding layers are located exclusively on each of the end portions of the transmission belt, respectively at the first and second sections.

[0036] Thanks to the connecting layers, the transmission belt according to the invention is dimensional. In other words, it is designed so that once in the closed or assembled state, the belt has a length adapted to the desired dimension.

[0037] Alternatively, the drive belt can be prepared upstream at a production site, which can be separate from the installation site to avoid any additional material being brought to the installation site.

[0038] In fact, the bonding system can be directly included in the transmission belt, without the need to provide external glue or adhesive. Such a bonding of the free end portions of the transmission belt makes it possible to obtain good mechanical strength at a junction zone in the assembled state of the belt.

[0039] Advantageously, each bonding layer has a transverse dimension, i.e. a thickness, of between 20 pm and 100 pm, preferably between 30 pm and 60 pm.

[0040] "Thickness" means the dimension of the belt in the transverse direction, perpendicular to the direction of longitudinal extension of the belt in the free state.

[0041] For example, the bonding layers have the same length in the direction of belt extension.

[0042] According to one embodiment, the end surface of each of the end portions extends along a plane comprising the vertical axis and the transverse axis.

[0043] According to another embodiment, the end surface of each of the end portions extends along an inclined plane comprising the transverse axis and an axis inclined at an angle of between 0° and 60° relative to the vertical axis, such that the contact surface between the ends of the end portions extends along a vertically inclined plane.

[0044] In other words, the contact surfaces of the end portions are beveled.

[0045] For example, the belt comprises a mechanical drive surface comprising a plurality of ribs or teeth each extending in the direction perpendicular to the direction of extension of the transmission belt.

[0046] The teeth are intended to be engaged in grooves or grooves of complementary shape, for example provided on pulleys on which the belt is intended to be mounted. When the transmission belt is in the initial state, before assembly, it extends along the longitudinal axis and its teeth extend along the transverse axis.

[0047] Each tooth has, in a non-limiting manner, a trapezoidal section along a plane perpendicular to the transverse axis. The general directions of the teeth are substantially parallel to each other.

[0048] Advantageously, the internal surface of one of the free end portions is devoid of teeth.

[0049] Alternatively, the mechanical drive surface is smooth, so as to form a contact surface by adhesion. This type of belt is known as a "flat" belt.

[0050] For example, each bonding layer is coated with a removable protective film intended to be removed before assembly of the free end portions of the belt.

[0051] For example, each protective film is made of polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), polyamide or nylon (PA), polyethylene terephthalate (PET), polyester.

[0052] The protective films serve to protect the associated bonding layer during storage and handling of the drive belt.

[0053] Protective films allow the transmission belt to be easily stored in its initial, unassembled state, without the risk of accidental welding of the free end portions. In addition, the films help preserve the properties, particularly the welding capabilities, of the bonding layers.

[0054] For example, the second non-thermoplastic elastomer material of the matrix comprises at least one elastomer selected from the group consisting of a natural rubber (NR), a synthetic polyisoprene (IR), a butadiene-styrene copolymer (SBR).

[0055] In one embodiment, the matrix comprises a so-called “reinforcing” filler.

[0056] When a reinforcing filler is used, any type of reinforcing filler known for its ability to reinforce an elastomeric matrix may be used, for example an organic filler, such as carbon (CB), a reinforcing inorganic or mineral filler such as silica, or a mixture of these two types of fillers. The rubber compositions may also include all or part of the additives, which are usually used in elastomeric materials, such as plasticizing resins or extender oils, whether the latter are aromatic or non-aromatic in nature, protective agents such as anti-ozone waxes, antioxidants, etc.

[0057] Preferably, the matrix comprises a crosslinking system.

[0058] The crosslinking system advantageously comprises a co-crosslinking agent, preferably sulfur or triallylcyanurate.

[0059] Advantageously, the rate of the co-crosslinking agent is between 0.5pce and 5pce.

[0060] In one embodiment, each reinforcing element is metallic.

[0061] Alternatively, each reinforcing element could be made of a non-metallic material, for example polyethylene terephthalate (PET), polyamide or nylon (PA6), carbon, glass, rayon, etc.

[0062] For example, each reinforcing element is a wire reinforcing element. The reinforcing elements may be woven to form the reinforcing layers. Alternatively, the reinforcing elements may be fibers blended with the non-thermoplastic elastomer material.

[0063] By "wire reinforcement element" is meant elongated elements of great length relative to their cross-section, whatever the shape of the latter, for example circular, oblong, rectangular, square or flat.

[0064] A wire reinforcement element can be straight or non-straight, for example twisted or corrugated.

[0065] A reinforcing element may comprise a plurality of elementary monofilaments assembled together.

[0066] The wire reinforcement elements may be arranged in the length direction of the transmission belt, possibly at an angle of between 0° and 45° relative to the length direction of the belt.

[0067] For example, the first material and / or the third material are respectively composed of a thermoplastic elastomer comprising a block copolymer comprising at least one elastomer block and at least one thermoplastic block, and the total content of thermoplastic elastomer being within a range varying from 65 to 100 pce (parts by weight per hundred parts of elastomer).

[0068] For example, the second material and / or the third material composed of a thermoplastic elastomer is chosen from the following copolymers: a copolymer whose elastomer blocks are unsaturated, and which comprises styrene blocks and diene blocks, a copolymer whose elastomer blocks are unsaturated, and which comprises styrene blocks and diene blocks, and a linear or star copolymer whose elastomer blocks comprise a saturated part and an unsaturated part.

[0069] According to another aspect, the invention relates to a method of manufacturing a transmission belt comprising a body extending in a longitudinal direction comprising a main portion and two end portions each extending from one end of the main portion and each comprising at least one layer of reinforcing elements embedded in said body and a contact surface.

[0070] Said transmission belt is configured to pass from an initial, unassembled state, in which the end portions are free, to an assembled state in which the end portions are secured to each other via their contact surface. At least the contact surfaces are made of thermoplastic elastomer.

[0071] The reinforcing elements extend in at least two superimposed reinforcing layers in a transverse direction in the thickness of the body in the assembled state of the belt.

[0072] According to the process:

[0073] - the contact surfaces are shaped from a matrix made of a thermoplastic elastomer material; and the end portions of the transmission belt are assembled in the free state at a junction zone, by bringing the contact surfaces into contact with each other in a direction perpendicular to a direction of extension of the belt, then by bonding between said bonding layers by applying a pressure of between 0.1 bars and 20 bars and heat, in particular a temperature of between 80°C and 300°C, preferably between 120°C and 200°C.

[0074] Thus, the belt is prepared upstream in a production site, which can be separate from the installation site to avoid any additional material being brought to the installation site.

[0075] According to one embodiment, the body is shaped from an elastomeric matrix made from a first thermoplastic elastomer material, the contact surfaces being directly formed on the body.

[0076] According to another embodiment:

[0077] - the body is shaped from an elastomeric matrix made from a second non-thermoplastic elastomeric material (at this stage, the non-thermoplastic material is not yet crosslinked);

[0078] - an internal bonding layer and an external bonding layer are formed from a third thermoplastic elastomer material;

[0079] - the internal bonding layer is deposited on at least part of an internal surface of one of the end portions;

[0080] - the external bonding layer is deposited on at least part of an external surface of the other of the end portions.

[0081] The method further comprises, before the step of assembling the end portions of the transmission belt, a step of curing the belt comprising the non-thermoplastic elastomeric body comprising the reinforcing elements, and comprising the bonding layers.

[0082] For example, the belt can be cooked in a mold, in an oven, for example at a temperature between 100°C and 200°C, preferably between 100°C and 150°C at a pressure between 0.1 bars and 20 bars, preferably at a temperature of 140°C to 2 bars.

[0083] During the curing step, although the bonding layers do not have a crosslinking system, the crosslinking system of the elastomeric matrix is ​​sufficient to bond the thermoplastic elastomer bonding layers with said non-thermoplastic elastomeric matrix by crosslinking. In fact, the crosslinking system of the elastomeric matrix migrates during the assembly of the belt, under the effect of pressure and thanks to the input of heat, from the matrix to the bonding layers.

[0084] In other words, the bonding layers are crosslinked only locally at the interface with the non-thermoplastic elastomeric matrix during the assembly step.

[0085] This crosslinking bond between the elastomeric matrix and the bonding layers is robust over time.

[0086] Advantageously, after the cooking step, the end portions of the transmission belt are assembled, during a heat-sealing step, in the free state at a junction zone, by bringing the bonding layers into contact together in a direction perpendicular to a direction of extension of the belt, then by bonding between said bonding layers by applying a pressure of between 0.1 bar and 20 bar and heat, in particular a temperature of between 80°C and 300°C, preferably between 120°C and 200°C.

[0087] The neutral layer (also commonly referred to as the "neutral fiber" layer) refers to the longitudinal portion of the belt that does not undergo any variation in length during bending. In other words, in the case of a belt subjected to bending, the neutral fiber layer is the surface located inside the belt and formed by the fibers that undergo neither shortening nor elongation but only bending.

[0088] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0089] [Fig. 1] very schematically represents a general view of a transmission belt according to the invention; [Fig. 1B] illustrates in detail a flat portion of the transmission belt of figure 1;

[0090] [Fig.2] and [Fig.3] are detailed views of a transmission belt according to one embodiment of the invention before assembly of the end portions of said belt;

[0091] [Fig.4] is a detailed view of the belt of Figure 3 after assembly of the end portions of said belt;

[0092] [Fig.5] is a detailed view of a transmission belt according to a second embodiment of the invention after assembly of the end portions of said belt;

[0093] [Fig.6] is a detailed view of a transmission belt according to a third embodiment of the invention before assembly of the end portions of said belt;

[0094] [Fig.7] illustrates the steps of a manufacturing process for the belt of Figure 1; and

[0095] [Fig.8] represents a step of assembling the end portions of the belt of figure 2.

[0096] Figures 1 to 8 are described as relating to a transmission belt, and are to be understood as also relating to a track.

[0097] In the following description, the terms "longitudinal", "transverse", "vertical", "front", "rear", "left" and "right" are defined according to the usual orthogonal reference of transmission belts, shown in the drawings, and which includes:

[0098] - a longitudinal axis X, horizontal and oriented from left to right in figure 1B in the direction of movement of the transmission belt; - a transverse axis Y, horizontal, perpendicular to the longitudinal axis X and oriented from bottom to top in figure 1B;

[0099] - a vertical axis Z, orthogonal to the longitudinal and transverse axes X and Y and directed from front to back in figure 1B.

[0100] Figure 1 illustrates an example of a transmission belt, referenced 10 as a whole, configured to transmit a rotational movement and / or mechanical power between two or more mechanical members, for example pulleys (not shown).

[0101] By "thickness" is meant the dimension of the belt 10 in the transverse direction Y, visible in figures 1B and 2 to 6.

[0102] By "length" is meant the dimension of the belt 10 in the longitudinal direction X, visible in figures 1B and 2 to 6.

[0103] By "width" is meant the dimension of the belt 10 in the vertical direction Z, visible in Figures 1B and 2 to 6.

[0104] The transmission belt 10 is here in the closed or assembled state, ready to be used for the mechanical drive of the mechanical components.

[0105] The transmission belt 10 is a so-called "open" belt, that is to say that it is stored in an initial unassembled state and is configured to be installed in a complex mechanical environment requiring its assembly directly on the installation site.

[0106] The transmission belt 10 comprises a body 11 made in a matrix 12 and in which reinforcing elements 14a, 14b are embedded, here in the form of two layers of reinforcements superimposed along the transverse axis Y.

[0107] The body 11 is delimited transversely by an external surface 13 and an internal surface 15.

[0108] The terms "external" and "internal" are defined in relation to the center C of the transmission belt when closed, the external surfaces being further apart than the internal surfaces. The internal surface 15 of the body 11 forms a mechanical drive surface configured to drive a mechanical member (not shown).

[0109] In the example illustrated in the figures, the mechanical drive surface 15 comprises a plurality of ribs or teeth 16 each extending in the direction perpendicular to the direction of extension of the belt 10.

[0110] Alternatively, the mechanical drive surface 15 could be smooth, so as to form an adhesion contact surface. This type of belt is known as a "flat" belt.

[0111] When the transmission belt 10 is in the initial state, before assembly, it extends along the longitudinal axis X and its teeth extend along the transverse axis Y.

[0112] Each tooth 16 has here, in a non-limiting manner, a trapezoidal section along a plane perpendicular to the transverse axis. The general directions of the teeth 16 are substantially parallel to each other.

[0113] The teeth 16 extend over the entire length of the belt 10, except the internal surface 15a of one of the end portions 12a.

[0114] The teeth 16 are intended to be engaged in grooves or grooves (not shown) of complementary shape, for example provided on pulleys on which the belt 10 is intended to be mounted.

[0115] In the initial, unassembled state, visible in Figures 2 and 3, the power transmission belt 10 is delimited along its longitudinal extension axis X by two free end portions 12a, 12b.

[0116] Each free end portion 12a, 12b is delimited transversely by an internal surface 15a, 15b and an external surface 13a, 13b.

[0117] The inner surface 15a of one of the end portions 12a and the outer surface 13b of the other of the end portions 12b form contact surfaces of the end portions 12a, 12b.

[0118] The reinforcing elements 14a, 14b are embedded in the matrix 12. The reinforcing elements 14a, 14b form the core of the transmission belt 10.

[0119] As illustrated, the reinforcing elements 14a, 14b are parallel to each other in the vertical direction Z and extend along two superimposed reinforcing layers in the transverse direction Y, i.e. in the thickness of the matrix 12.

[0120] Each reinforcing layer 14a, 14b has a transverse dimension, i.e. a thickness, of between 0.1 mm and 7 mm.

[0121] Each reinforcing layer 14a, 14b is embedded in the matrix 12, that is to say surrounded by the matrix 12.

[0122] The end portions 12a, 12b have a thickness less than the total thickness of the body 11.

[0123] One of the end portions 12a is composed of a first section of the belt having a thickness less than the thickness of the body 11 to retain only the external reinforcing layer 14b and the other of the end portions 12b is composed of a second section of the belt having a thickness less than the thickness of the body 11 to retain only the internal reinforcing layer 14a.

[0124] The inner surface 15a of one of the end portions 12a is offset transversely outwards relative to the inner surface 15 of the body 11.

[0125] The outer surface 13b of the other of the end portions 12b is offset transversely inwardly relative to the outer surface 13 of the body 11.

[0126] When assembling the end portions 12a, 12b together, the inner surface 15a of one of the end portions 12a is superimposed transversely on the outer surface 13b of the other of the end portions 12b so that the inner reinforcing layer 14a of one of the end portions 12a is opposite in the longitudinal direction X the inner reinforcing layer 14a of the other of the end portions 12b and the outer reinforcing layer 14b of one of the end portions 12a is opposite in the longitudinal direction X the outer reinforcing layer 14b of the other of the end portions 12b. Thus, the neutral fiber of the reinforcements is preserved.

[0127] The junction zone ZI between the two end portions 12a, 2b is located between two reinforcement layers 14a, 14b.

[0128] In other words, the joining of the end portions 12a, 12b makes it possible to superimpose the first and second sections of the belt 10 and to reconstitute the belt in the assembled state.

[0129] As illustrated in Figures 2 to 4, the inner surface 15a of one of the free end portions 12a, here the left portion, is partly coated with an inner bonding layer 17 and the outer surface 13b of the other of the free end portions 12b, here the right portion, is partly coated with an outer bonding layer 18.

[0130] In this example, the inner bonding layer 17 forms an inner contact surface and the outer bonding layer 18 forms an outer contact surface.

[0131] Said contact surfaces are intended to come into contact along the transverse axis Y perpendicular to the belt 10 when the belt is in the assembled state. Said contact surfaces are parallel or slightly inclined relative to the extension axis X of the belt 10 during the heat-sealing step described below with reference to FIG. 7.

[0132] By way of non-limiting example, the internal bonding layer 17 may be crosslinked only at the interface with the matrix 12 and the external bonding layer 18 may be crosslinked only at the interface with the matrix 12 during the heat-sealing step described below with reference to FIG. 7.

[0133] The internal surface 15a of one of the free end portions 12a is devoid of teeth 16.

[0134] The connecting layers 17, 18 here have the same length in the direction of extension of the belt 10.

[0135] The connecting layers 17, 18 are located exclusively on each of the end portions 12a, 12b of the transmission belt 10.

[0136] The free end portions 12a, 12b of the transmission belt 10 are assembled at a junction zone Z l, by bringing the connecting layers 17, 18 into contact in a direction perpendicular to the direction of extension of the belt 10, then by bonding between said connecting layers 17, 18 by applying a pressure of between 0. lbars and 20 bars and heat, in particular a temperature of between 80°C and 300°C, preferably between 120°C and 200°C.

[0137] Thus, the transmission belt 10 is prepared upstream of the installation site to avoid any additional material being brought to the installation site.

[0138] In fact, the bonding system is directly included in the transmission belt 10, without the need to provide external glue or adhesive.

[0139] Such a connection of the free end portions of the transmission belt makes it possible to obtain good mechanical strength at the junction zone ZI in the assembled position, as will be explained with reference to figure 7.

[0140] Thanks to the connecting layers 17, 18, the transmission belt 10 is dimensional. In other words, it is designed so that once in the closed or assembled state, the belt has a length adapted to the desired dimension.

[0141] Alternatively, the drive belt may not be dimensional.

[0142] For example, each bonding layer 17, 18 may be coated with a removable protective film (not shown) intended to be removed before assembly of the free end portions 12a, 12b of the belt 10.

[0143] Each protective film is made, for example, of polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), polyamide or nylon (PA), polyethylene terephthalate (PET), polyester, etc.

[0144] The protective films have the function of protecting the associated bonding layer 17, 18 during storage and handling of the transmission belt 10. The protective films make it possible to easily store the transmission belt 10 in its initial, unassembled state, without the risk of accidental welding of the free end portions 12a, 12b.

[0145] In order to assemble the transmission belt 10, the end portions 12a, 12b in the free state are mounted in a tool 30, visible in FIG. 8, so as to superimpose the two connecting layers 17, 18 or more generally the internal surface 15a of one of the free end portions 12a with the external surface 13b of the other of the free end portions.

[0146] A pressure F1, F2 of between 0.1 bar and 20 bar is applied to the end portions 12a, 12b in a direction perpendicular to the direction of extension of the belt 10 and heat, in particular a temperature of between 80°C and 300°C, preferably between 120°C and 200°C in order to heat-weld said free end portions 12a, 12b together.

[0147] In the embodiment illustrated in Figures 2 to 4, the body 11 of the belt 10 is shaped from a matrix 12 made of a second elastomeric material not comprising thermoplastic and each bonding layer 17, 18 is shaped from a third thermoplastic elastomer material.

[0148] Shaping can be achieved, for example, by molding, extrusion or other known techniques.

[0149] Alternatively, as illustrated in FIG. 5, the body 11 of the belt 10 is shaped from a matrix 12 made of a first thermoplastic elastomer material. In this embodiment, the belt 10 does not comprise bonding layers 17, 18.

[0150] In this case, the free end portions 12a, 12b of the transmission belt 10 are assembled at the junction zone Z l , by bringing the end portions 12a, 12b into contact together, in particular the internal surface 15a of one of the end portions 12a with the external surface 13b of the other of the end portions 12b, for example in a direction perpendicular to the direction of extension of the belt 10, then by connection between said internal surface 15a and said external surface 13b by applying a pressure of between 0.1 bar and 20 bar and heat, in particular a temperature of between 80°C and 300°C, preferably between 120°C and 200°C.

[0151] Said internal surface 15a and said external surface 13b here form the contact surfaces of the end portions 12a, 12b of the belt 10.

[0152] As illustrated in Figures 2 to 5, the end surface of each of the end portions 12a, 12b extends along a plane YZ comprising the vertical axis Z and the transverse axis Y.

[0153] The embodiment illustrated in Figure 6, in which the same elements bear the same references, differs from the previous embodiment only in that the end surface of each of the end portions 12a, 12b extends along an inclined plane YZ' comprising the transverse axis Y and an axis Z' inclined at an angle of between 0° and 60° relative to the vertical axis Z, so that the contact surface between the ends of the end portions 12a, 12b extends along a vertically inclined plane.

[0154] In other words, the contact surfaces between the ends of the end portions 12a, 12b are beveled.

[0155] In the example illustrated in Figure 6, the body 11 is shaped from a matrix 12 made from the first thermoplastic elastomer material. Alternatively, it can be provided that the body

[0156] 1 1 is shaped from a matrix 12 made from the second non-thermoplastic elastomer material and that the belt comprises connecting layers 17, 18 secured at least in part to the end parts 12a, 12b.

[0157] Non-thermoplastic elastomer body

[0158] In the embodiment illustrated in Figures 2 to 4, the elastomeric body 11 of the belt is shaped, from a matrix

[0159] 12 in elastomer or non-thermoplastic elastomer.

[0160] In this embodiment, the end portions 12a and 12b of the body 11 of the belt 10 are coated with the connecting layers 17, 18 made of elastomeric thermoplastic. The addition of connecting layers 17, 18 to the end portions 12a, 12b of the transmission belt 10 facilitates the connection of said end portions 12a, 12b and provides improved thermal resistance of the belt 10.

[0161] Non-thermoplastic elastomeric matrix

[0162] By "non-thermoplastic elastomeric matrix" is meant a matrix with elastomeric behavior.

[0163] The non-thermoplastic elastomeric matrix 12 in which the reinforcing elements 14 are embedded comprises one or more elastomers.

[0164] The non-thermoplastic elastomeric matrix 12 is made of a second material.

[0165] Preferably, the second material comprises at least one elastomer chosen from the group consisting of a natural rubber (NR), a synthetic polyisoprene (IR), a butadiene-styrene copolymer (SBR).

[0166] Generally, the non-thermoplastic elastomeric matrix 12 does not include a thermoplastic block.

[0167] In other words, the elastomeric matrix 12 is made of diene rubber as a non-thermoplastic elastomer, this diene rubber being able to be used alone, or in a blend with at least one (i.e. one or more) other non-thermoplastic rubber or elastomer.

[0168] By “diene” elastomer or rubber, we mean one or more elastomers derived at least in part (i.e.; a homopolymer or a copolymer) from diene monomers (monomers carrying two carbon-carbon double bonds, conjugated or not).

[0169] In one embodiment, the non-thermoplastic elastomeric matrix 12 comprises a so-called “reinforcing” filler.

[0170] When a reinforcing filler is used, any type of reinforcing filler known for its ability to reinforce an elastomeric matrix may be used, for example an organic filler, such as carbon (CB), a reinforcing inorganic or mineral filler such as silica, or a mixture of these two types of fillers. The rubber compositions may also include all or part of the usual additives normally used in elastomeric materials, such as plasticizing resins or extending oils, whether the latter are aromatic or non-aromatic in nature, protective agents such as anti-ozone waxes, antioxidants, etc.

[0171] Preferably, the non-thermoplastic elastomeric matrix 12 comprises a crosslinking system (not shown).

[0172] The crosslinking system advantageously comprises a co-crosslinking agent, preferably sulfur or triallylcyanurate. Advantageously, the level of the co-crosslinking agent is between 0.5 pce and 5 pce.

[0173] Reinforcing elements

[0174] In one embodiment, each reinforcing element 14 of a reinforcing layer is metallic.

[0175] Alternatively, each reinforcing element 14 may be made of a non-metallic material, for example polyethylene terephthalate (PET), polyamide or nylon (PA6), carbon, glass, rayon, etc.

[0176] For example, each reinforcing element 14 is a wire reinforcing element. The reinforcing elements 14 may be woven to form a woven layer.

[0177] By "wire reinforcement element" is meant elongated elements of great length relative to their cross-section, whatever the shape of the latter, for example circular, oblong, rectangular, square or flat.

[0178] A wire reinforcement element can be straight or non-straight, for example twisted or corrugated.

[0179] A reinforcing element may comprise a plurality of elementary metal monofilaments assembled together.

[0180] The wire reinforcement elements may be arranged in the length direction of the transmission belt (i.e. in the longitudinal direction), optionally at an angle of between 0° and 45° relative to the length direction of the belt.

[0181] Bonding layers Each bonding layer 17, 18 directly coats one of the free end portions 12a, 12b of the elastomeric matrix 12.

[0182] By layer “directly” coating an object, we mean that the layer is in contact with the object without any other object, in particular another layer, being interposed between the two.

[0183] Each bonding layer 17, 18 has a transverse dimension, i.e. a thickness, of between 20 pm and 100 pm, preferably between 30 pm and 60 pm.

[0184] Each bonding layer 17, 18 is made of a third material which may be distinct from the second material forming the elastomeric matrix 12.

[0185] The third material preferably comprises exclusively a thermoplastic elastomer, with the acronym “TPE”.

[0186] In particular, the third material, before being shaped to compose the bonding layers 17 and 18, does not include a co-crosslinking system agent.

[0187] Thermoplastic elastomer body

[0188] Alternatively, the elastomeric body 11 of the belt is shaped from a matrix 12 of first thermoplastic elastomer material. The shaping can be carried out by molding, by extrusion, or by other known techniques.

[0189] The body 11 contains the reinforcing elements 14 which are embedded in the matrix 12.

[0190] In this embodiment, the end portions 12a and 12b directly comprise surfaces made of thermoplastic elastomer material. The bonding layers are made of the matrix 12 which is therefore made of thermoplastic elastomer.

[0191] Thermoplastic elastomer

[0192] A thermoplastic elastomer is a block copolymer comprising at least one elastomer block and at least one thermoplastic block, and the total content of thermoplastic elastomer being in a range varying from 65 to 100 pce (parts by weight per hundred parts of elastomer). In other words, thermoplastic elastomers have an intermediate structure between thermoplastic polymers and elastomers. They are block copolymers, consisting of rigid, thermoplastic blocks, connected by flexible, elastomer blocks.

[0193] The second material is distinct from the first material in that the second material does not comprise rigid, thermoplastic blocks.

[0194] The number-average molecular mass (denoted Mn) of TPE is preferably between 30,000 and 500,000 g / mol, more preferably between 40,000 and 400,000 g / mol.

[0195] In the present application, when reference is made to the glass transition temperature of the TPE, this refers to the Tg relative to the elastomer block. The TPE preferably has a glass transition temperature ("Tg") which is preferably less than or equal to 25°C, more preferably less than or equal to 10°C. A Tg value higher than these minima may reduce the performance of the bonding layer during use at very low temperatures; for such use, the Tg of the TPE is more preferably still less than or equal to -10°C. Also preferably, the Tg of the TPE is greater than -100°C.

[0196] As is known, TPEs have two peaks of glass transition temperature (Tg, measured according to ASTM D3418-21), the lower temperature being relative to the elastomeric part of the TPE, and the higher temperature being relative to the thermoplastic part of the TPE. Thus, the soft blocks of TPE are defined by a Tg lower than room temperature (25°C), while the rigid blocks have a Tg higher than 80°C.

[0197] Thermoplastic blocks having a Tg (or Tf, where appropriate) greater than or equal to 80°C can be made from polymerized monomers of various natures, in particular, they can constitute the following blocks or their mixtures: polyolefins (polyethylene, polypropylene); polyurethanes; polyamides; polyesters; polyacetals; polyethers (polyethylene oxide, polyphenylene ether); polyphenylene sulfides; polyfluorinated materials (FEP, PFA, ETFE); polystyrenes (detailed below); polycarbonates; polysulfones; polymethylmethacrylate; polyetherimide; thermoplastic copolymers such as acrylonitrile-butadiene-styrene copolymer (ABS).

[0198] Alternatively, other monomers could be provided.

[0199] For example, TPE is a copolymer whose elastomer blocks are saturated, and include styrene blocks and alkylene blocks. The alkylene blocks are preferably ethylene, propylene or butylene. More preferably, this TPE elastomer is chosen from the following group, consisting of linear or star-shaped diblock or triblock copolymers: styrene / ethylene / butylene (SEB), styrene / ethylene / propylene (SEP), styrene / ethylene / ethylene / propylene (SEEP), styrene / ethylene / butylene / styrene (SEBS), styrene / ethylene / propylene / styrene (SEPS), styrene / ethylene / ethylene / propylene / styrene (SEEPS), styrene / isobutylene (SIB), styrene / isobutylene / styrene (SIBS) and mixtures of these copolymers.

[0200] According to another example, TPE is a copolymer whose elastomer blocks are unsaturated, and which comprises styrene blocks and diene blocks, these diene blocks being in particular isoprene or butadiene blocks. More preferably, this TPE elastomer is chosen from the following group, consisting of linear or star diblock or triblock copolymers: styrene / butadiene (SB), styrene / isoprene (SI), styrene / butadiene / isoprene (SBI), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / butadiene / isoprene / styrene (SBIS) and mixtures of these copolymers.

[0201] For example, TPE is also a linear or star copolymer whose elastomer blocks include a saturated part and an unsaturated part, such as styrene / butadiene / butylene (SBB), styrene / butadiene / butylene / styrene (SBBS) and mixtures of these copolymers.

[0202] Figure 7 illustrates the steps of a method 100 for manufacturing the transmission belt 10. During a first step 101, at least the contact surfaces between the end portions 12a, 12b are shaped from a matrix in a thermoplastic elastomer material.

[0203] Shaping may be accomplished by molding, extrusion, or other known techniques.

[0204] According to one embodiment, the elastomeric body 11 of the belt is shaped from an elastomeric matrix 12 in a first thermoplastic elastomer material.

[0205] According to another embodiment, the elastomeric body 11 of the belt is shaped from an elastomeric matrix 12 in a second non-thermoplastic elastomeric material.

[0206] The method 100 further comprises a step 104 of assembling the end portions 12a, 12b of the transmission belt 10 in the free state at a junction zone, by bringing the contact surfaces into contact together in a direction perpendicular to a direction of extension of the belt 10.

[0207] The assembly step 104 is carried out by applying a pressure of between 0.1 bar and 20 bar and heat, in particular a temperature of between 80°C and 300°C, preferably between 120°C and 200°C.

[0208] Thus, the belt is prepared upstream in a production site, which can be separate from the installation site to avoid any additional material being brought to the installation site.

[0209] In the case where the elastomeric body 11 of the belt is shaped, from an elastomeric matrix 12 in a second non-thermoplastic elastomer material, the method 100 comprises a step 105 of shaping the contact surfaces in thermoplastic elastomer material.

[0210] Step 105 of shaping the contact surfaces made of thermoplastic elastomer material comprises a step 102 of shaping each bonding layer 17, 18 from the third material described above and a step 103 of laying during which the internal bonding layer 17 is deposited on at least a portion of the internal surface 15a of one of the end portions 12a and the external bonding layer 18 is deposited on at least a portion of the external surface 13b of the other of the end portions 12b.

[0211] The manufacturing method 100 further comprises a step 106 of curing the belt 10 comprising the non-thermoplastic elastomeric body 11, optionally comprising the reinforcements, and comprising the bonding layers 17 and 18.

[0212] For example, the cooking of the belt 10 can be carried out in a mold, in an oven, for example at a temperature between 100°C and 200°C, preferably between 100°C and 150°C at a pressure between 0.1 bars and 20 bars, preferably at a temperature of 140°C to 2 bars.

[0213] In this embodiment, during the curing step, although the bonding layers 17, 18 do not have a crosslinking system, the crosslinking system of the elastomeric matrix 12 in the second material is sufficient to bond the bonding layers 17, 18 of thermoplastic elastomer with said non-thermoplastic elastomeric matrix 12 by crosslinking. Indeed, the crosslinking system of the elastomeric matrix 12 migrates during the assembly of the belt 10, under the effect of pressure and thanks to the supply of heat, from the matrix to the bonding layers 17, 18.

[0214] In other words, the bonding layers 17, 18 are crosslinked only locally at the interface with the non-thermoplastic elastomeric matrix 12 during the assembly step 104.

[0215] This crosslinking connection between the elastomeric matrix 12 and the bonding layers 17, 18 is robust over time.

[0216] In polymer chemistry, crosslinking is the formation of one or more three-dimensional networks, either chemically or physically. Polymer crosslinking is well known and will not be described further.

[0217] In the context of the invention, the carbon products mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. The term "pce" (in English "phr") means, within the meaning of the present patent application, part by weight per hundred parts of elastomer, thermoplastic and non-thermoplastic combined. Within the meaning of the present invention, thermoplastic elastomers (TPE) are part of the elastomers.

[0218] Thanks to the particular structure of the transmission belt comprising two layers of reinforcement superimposed in the transverse direction, a neutral fiber of the reinforcements is maintained.

[0219] Furthermore, the thermowelding of the thermoplastic integrated into the belt allows to benefit from a bonding system directly included in the transmission belt, without the need to provide an external glue or adhesive. Furthermore, such a connection of the free end portions of the transmission belt allows to obtain good mechanical strength at a junction zone in the assembled state of the belt.

Claims

CLAIMS 1. Transmission belt (10) or track comprising a body (11) extending in a longitudinal direction (X) comprising a main portion (12c) and two end portions (12a, 12b) each extending from one end of the main portion (12c), produced in a matrix (12), and delimited by two end portions (12a, 12b), said transmission belt (10) being configured to pass from an initial state, in which the end portions (12a, 12b) are free to an assembled state in which the end portions (12a, 12b) are integral with each other via a contact surface, characterized in that each of the end portions (12a, 12b) comprises at least one layer of reinforcing elements embedded in said body (11) and a contact surface (15a, 13b, 17, 18), in that at least the contact surfaces (15a, 13b, 17, 18) are made of thermoplastic elastomer and in that the reinforcing elements (14a,14b) extend along at least two reinforcing layers superimposed along a transverse direction (Y) in the thickness of the matrix (12) in the assembled state of the belt., 2. Transmission belt (10) according to claim 1, in which each reinforcing layer (14a, 14b) has a transverse dimension, between 0.1 mm and 7 mm.

3. Transmission belt (10) according to claim 1 or 2, wherein the contact surfaces (15a, 13b, 17, 18) are located transversely between the two reinforcing layers (14a, 14b).

4. Transmission belt (10) according to claim 3, wherein the end portions (12a, 12b) have a thickness less than the total thickness of the matrix (12).

5. Transmission belt (10) according to claim 4, in which one of the end portions (12a) comprises a first section having a thickness less than the total thickness of the body (11) of the belt and a single external reinforcing layer (14b) and the other of the end portions (12b) comprises a second section having a thickness less than the total thickness of the body (11) of the belt and a single internal reinforcing layer (14a), and wherein, in the assembled state of the belt, the internal surface of the first section is superimposed transversely on the external surface of the second section so that the sheet of neutral fibers of the belt is at the same transverse position at the main portion and at the end portions when the belt is in the assembled state of the belt.

6. Transmission belt (10) according to any one of claims 3 to 5, in which the matrix (12) is made of a first thermoplastic elastomer material and in which the internal surface (15a) of one of the end portions (12a) forms a first contact surface and the external surface (13b) of the other of the end portions (12b) forms a second contact surface, said contact surfaces being configured to be integral with each other in the assembled state of the transmission belt (10).

7. Transmission belt (10) according to any one of claims 3 to 5, wherein the matrix (12) is made of a second non-thermoplastic elastomer material and wherein the inner surface (1 a) of one of the end portions (12a) is coated at least in part with an inner bonding layer (17) crosslinked only locally at the interface with the matrix (12) and the outer surface (13b) of the other of the end portions (12b) is coated at least in part with an outer bonding layer (18) crosslinked only locally at the interface with the matrix (12), said bonding layers (17, 18) being made of a third thermoplastic elastomer material and configured to be integral with one another in the assembled state of the transmission belt (10).

8. Transmission belt (10) according to claim 7, wherein each connecting layer (17, 18) has a transverse dimension of between 20 pm and 100 pm, preferably between 30 pm and 60 pm.

9. Transmission belt (10) according to claim 7 or 8, wherein the second non-thermoplastic elastomer material of the matrix (12) comprises at least one elastomer selected from the group consisting of a natural rubber (NR), a synthetic polyisoprene (IR), a butadiene-styrene copolymer (SBR).

10. Transmission belt (10) according to claim 6 or any one of claims 7 to 9, in which the first material or the third material is composed of a thermoplastic elastomer comprising a block copolymer comprising at least one elastomer block and at least one thermoplastic block, and the total content of thermoplastic elastomer being within a range varying from 65 to 100 pce (parts by weight per hundred parts of elastomer). 1 1. Transmission belt (10) according to claim 10, in which the first material or the third material composed of a thermoplastic elastomer is chosen from the following copolymers: a copolymer whose elastomer blocks are unsaturated, and which comprises styrene blocks and diene blocks, a copolymer whose elastomer blocks are unsaturated, and which comprises styrene blocks and diene blocks, and a linear or star copolymer whose elastomer blocks comprise a saturated part and an unsaturated part.

12. Transmission belt (10) according to any one of the preceding claims, wherein the end surface of each of the end portions (12a, 12b) extends along a plane (ZY) comprising the vertical axis (Z) and the transverse axis (Y).

13. Transmission belt (10) according to any one of claims 1 to 11, wherein the end surface of each of the end portions (12a, 12b) extends along a plane (Z'Y) comprising the transverse axis (Y) and an inclined axis (Z') relative to the vertical axis (Z).

14. Method (100) for manufacturing a transmission belt (10) comprising a body (11) extending in a longitudinal direction (X) comprising a main portion (12c) and two end portions (12a, 12b) each extending from one end of the main portion (12c) and each comprising at least a layer of reinforcing elements (14a, 14b) embedded in said body (11) and a contact surface (15a, 13b, 17, 18), said transmission belt (10) being configured to pass from an initial, unassembled state, in which the end portions (12a, 12b) are free to an assembled state in which the end portions (12a, 12b) are integral with one another via their contact surface, the reinforcing elements (14a, 14b) extend along at least two superimposed reinforcing layers in a transverse direction (Y) in the thickness of the body (11) in the assembled state of the belt (10), in which: - the contact surfaces are shaped from a matrix (12) made of a thermoplastic elastomer material; and the end portions (12a, 12b) of the transmission belt (10) are assembled in the free state at a junction zone (Z 1 ), by bringing the contact surfaces into contact together in a direction (Y) perpendicular to a direction of extension (X) of the belt, then by bonding said contact surfaces by applying a pressure of between 0.1 bar and 20 bar and heat, in particular a temperature of between 80°C and 300°C, preferably between 120°C and 200°C.

15. Manufacturing method (100) according to claim 14, in which the body (11) of the belt (10) is shaped from an elastomeric matrix made from a first thermoplastic elastomer material, the contact surfaces being directly formed on the body (11).

16. Manufacturing method (100) according to claim 14, wherein: - the body (11) of the belt (10) is shaped from an elastomeric matrix (12) made from a second non-thermoplastic elastomeric material; - an internal bonding layer (17) and an external bonding layer (18) are formed from a third thermoplastic elastomer material; - the internal bonding layer (17) is deposited on at least one part of an inner surface (15a) of one of the end portions (12a); - the external bonding layer is deposited on at least a part of an external surface (13b) of the other of the end portions (12b), said bonding layers (17, 18) forming the contact surfaces, and before the step of assembling the end portions (12a, 12b) of the transmission belt (10), a step (106) of curing the belt (10) comprising the non-thermoplastic elastomeric body (11), comprising the reinforcing elements (14a, 14b), and comprising the bonding layers (17, 18) is carried out.

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