A power transmission belt comprising a plurality of teeth overmolded onto a reinforcement with at least one strip, and a method for manufacturing such a belt

Abstract

A drive belt (10) comprising a body (12) made of an elastomeric matrix (12a) and extending along an extension direction (X), and a reinforcement (14) integral with the body (12) and extending across the width of the belt, the body (12) comprising a mechanical drive surface (15) comprising a plurality of teeth (16) extending transversely along a transverse direction (Y) perpendicular to the extension direction (X). The elastomeric matrix (12a) is made of a first material comprising a thermoplastic elastomer, said elastomeric matrix (12a) being overmolded onto the reinforcement (14). The reinforcement (14) is composed of at least one layer of at least one wound strip (14a). (See Figure 3 for abbreviations.)

Description

Title of the invention: Power transmission belt comprising a plurality of teeth overmolded on a reinforcement with at least one strip, and method of manufacturing such a belt

[0001] The present invention relates to the field of transmission of drive forces, more particularly of transmission belts, in particular synchronous belts.

[0002] 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 in a synchronous manner.

[0003] The belt generally comprises a matrix and a reinforcement comprising a plurality of linear cables or wires embedded in said matrix.

[0004] Reference may be made in this regard to [Fig. 1] which illustrates such a belt 1 comprising a body 2 in which reinforcing wires 4 are embedded. The body 2 is delimited transversely by an external surface 3 and an internal surface 5. The mechanical drive surface 5 comprises a plurality of ribs or teeth 6 each extending in the direction perpendicular to the direction of extension of the belt 1.

[0005] The belts are generally made of rubber and require a molding process which can cause linear cable movements, as well as a vulcanization process requiring a baking step and therefore an increase in manufacturing time.

[0006] Moreover, such reinforcements are particularly rigid, so that adapting the belt onto a pulley can prove difficult.

[0007] The object of the invention is to provide an improved belt, easy to manufacture and easy to install on a mechanical component such as a pulley.

[0008] The invention relates to a transmission belt comprising a body made of an elastomeric matrix and extending along an extension direction and a reinforcement attached to the body and extending over the width of the belt, the body comprising an internal drive surface comprising a plurality of teeth or ribs extending transversely along a transverse direction perpendicular to the extension direction of the transmission belt.

[0009] The elastomeric matrix is ​​made of a first material comprising a thermoplastic elastomer, with the acronym "TPE".

[0010] The elastomeric matrix is ​​overmolded onto the reinforcement.

[0011] The use of a thermoplastic elastomer to manufacture the body and therefore the teeth of the transmission belt in particular, by high-pressure injection, has The advantages include being economical, ensuring good belt productivity, and eliminating the need for additional vulcanization or hot curing. The use of a thermoplastic elastomer reduces tooth wear, the coefficient of friction with pulleys, and significantly improves the energy efficiency of the drive belt.

[0012] Furthermore, the body can be recycled after the belt has been used. The use of hydrogenated elastomeric thermoplastics also reduces aging compared to the first material or unsaturated elastomeric thermoplastics.

[0013] The reinforcement consists of at least one layer of at least one rolled strip.

[0014] The strip is preferably substantially flat.

[0015] By "substantially flat" is meant a strip comprising a thickness along the transverse axis that is small compared to its width along the vertical axis.

[0016] By "small", we extend a thickness at least twice as small as the width, for example at least three times, or even five times, or even ten times smaller than the width.

[0017] By "thickness" we mean the dimension of the belt in the transverse direction, perpendicular to the longitudinal extension direction of the belt.

[0018] Such a substantially flat reinforcement not only reduces the overall thickness of the reinforcement and therefore of the belt, but also increases flexibility in bending in order to be able to adapt more easily to a mechanical component such as a pulley.

[0019] Furthermore, overmolding the body including the belt teeth directly onto the flat reinforcement simplifies the manufacture of the belt without generating displacement of the reinforcement and without requiring a subsequent baking step.

[0020] Advantageously, the reinforcement comprises at least two layers of at least one strip superimposed along the transverse axis. The first layer of strip is radially inward and a second layer of strip is radially outward.

[0021] Preferably, the strips of said first and second layers of strips are arranged in a juxtaposed manner.

[0022] Each strip extends in the direction parallel to the direction of extension of the belt.

[0023] Preferably, each strip of the reinforcement is wound in a helix or spiral forming an angle between 0° and 5° with respect to the direction of extension of the belt. Each spiral is contiguous with the previous one.

[0024] Preferably, the strips of the second strip layer are oriented at an angle opposite to the first strip layer.

[0025] According to one embodiment, the reinforcing strip is made up of high-modulus reinforcing elements. The reinforcing elements are coated with a matrix.

[0026] The reinforcing elements are preferably oriented in the direction of extension of the strip.

[0027] For example, the shape of the reinforcing elements is chosen from among fibers, single wires, an assembly of wires, cables, tapes and films.

[0028] Each reinforcing element, useful for the needs of the invention, can be in different forms, preferably in the form of a single wire, such as a continuous or discontinuous monofilament, or an assembly of wires, whether these wires are twisted together, for example, in the form of a cable, or essentially parallel to each other.

[0029] Each reinforcing element is more preferably in the form of a single wire or an assembly of wires, for example a cable or a strand manufactured with devices and processes of cabling or stranding known to the person skilled in the art, which are not described here for the sake of simplicity of the exposition.

[0030] The reinforcement can also be in the form of a ribbon or film.

[0031] By "wire" or "fiber", one generally means any long, thin element of large length relative to its cross-section, whatever the shape of the latter, for example circular, oblong, rectangular or square, or even flat, this wire can be straight or non-straight, for example twisted, or wavy.

[0032] By "film" or "strip", we generally mean a long, thin element, of great length relative to its cross-section, whose cross-section has a shape ratio, width to thickness, greater than five, preferably greater than ten.

[0033] Preferably, each reinforcing element is metallic or textile.

[0034] According to a preferred embodiment of the invention, the reinforcing elements are high modulus fibers comprising glass fibers. Preferably, glass fibers are predominant, i.e., they represent more than 50% of the fibers in the same layer.

[0035] In the present application, "high modulus" shall mean an extension modulus (Young's modulus) greater than or equal to 55 GPa.

[0036] Such an extension module is measured in accordance with ASTM D4848-98 (2012).

[0037] More preferably, the reinforcing elements are made of glass fibers.

[0038] Preferably, the volume ratio of polymer matrix / glass fibers ranging from 30 / 70, preferably from 35 / 65, to 80 / 20, preferably from 70 / 30 and being preferably about 45 / 55.

[0039] According to another preferred embodiment of the invention, the reinforcing elements are high-modulus fibers comprising carbon fibers. Preferably, the carbon fibers constitute the majority, i.e., represent more than 50% of the fibers.

[0040] Even more preferably, the reinforcing elements are made of carbon fibers.

[0041] Preferably, the volume ratio of polymer matrix / carbon fibers ranging from 30 / 70, preferably from 35 / 65 to 90 / 10, preferably to 60 / 40, and preferably being about 50 / 50.

[0042] According to other preferred embodiments of the invention, reinforcing elements include aramid fibers, basalt fibers or quartz fibers.

[0043] For example, the matrix composing the reinforcing strip is chosen from a thermosetting polymer or a thermoplastic polymer, used alone respectively or in cutting with other polymers.

[0044] For example, the thickness of the elastomeric matrix forming the body between the base of the teeth and the reinforcement is between 0.1mm and 0.4mm.

[0045] For example, the reinforcement has a transverse dimension, i.e. a thickness, between 0.1mm and 6mm.

[0046] The teeth are intended to be engaged in grooves or slots of complementary shape, for example provided on pulleys on which the belt is intended to be mounted.

[0047] Each tooth has, in no way limitingly, a trapezoidal shape in cross-section.

[0048] A thermoplastic elastomer is a block copolymer comprising at least one elastomer block and at least one thermoplastic block, and the total thermoplastic elastomer content being in the range of 65 to 100 parts per hundred parts of elastomer.

[0049] In other words, thermoplastic elastomers have an intermediate structure between thermoplastic polymers and elastomers.

[0050] These are block copolymers, consisting of rigid, thermoplastic blocks, linked by flexible, elastomeric blocks.

[0051] The first material composed of a thermoplastic elastomer is chosen from the following copolymers: a copolymer in which the elastomer blocks are unsaturated, and which comprises styrene blocks and diene blocks, a copolymer in which the blocks elastomers are unsaturated, and which comprise styrene blocks and diene blocks, and a linear or star copolymer whose elastomer blocks comprise a saturated part and an unsaturated part.

[0052] 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.

[0053] In this application, reference is made to the glass transition temperature of the TPE, and this refers to the Tg relative to the elastomer block. The TPE preferably has a glass transition temperature ("Tg") that is preferably less than or equal to 25 °C, and more preferably less than or equal to 10 °C. A Tg value above these minimums may reduce the performance of the underlayer during very low-temperature use; for such use, the Tg of the TPE is even more preferably less than or equal to -10 °C. Also preferably, the Tg of the TPE is greater than -100 °C.

[0054] As is known, TPEs exhibit two peak glass transition temperatures (Tg, measured according to ASTM D3418), the lower temperature being relative to the elastomer portion of the TPE, and the higher temperature being relative to the thermoplastic portion of the TPE. Thus, flexible blocks of TPE are defined by a Tg below ambient temperature (25°C), while rigid blocks have a Tg above 80°C.

[0055] Thermoplastic blocks having a Tg (or Tf, where applicable) greater than or equal to 80°C can be made up of polymerized monomers of various kinds, in particular, they can constitute the following blocks or mixtures thereof: polyolefins (polyethylene, polypropylene); polyurethanes; polyamides; polyesters; polyacetals; polyethers (polyethylene oxide, polyphenylene ether); polyphenylene sulfides; polyfluorinated compounds (FEP, PFA, ETFE); polystyrenes (detailed below); polycarbonates; polysulfones; polymethyl methacrylate; polyetherimide; thermoplastic copolymers such as acrylonitrile-butadiene-styrene copolymer (ABS).

[0056] Alternatively, other monomers could be used.

[0057] For example, TPE is a copolymer whose elastomer blocks are saturated, and contain styrene blocks and alkylene blocks.

[0058] 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, triblock, 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.

[0059] 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 diblock, linear or star 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.

[0060] For example, TPE is also a linear or star copolymer whose elastomeric blocks comprise a saturated part and an unsaturated part such as, for example, styrene / butadiene / butylene (SBB), styrene / butadiene / butylene / styrene (SBBS) or a mixture of these copolymers.

[0061] The terms "external" and "internal" are defined in relation to the center of the transmission belt, the external surfaces being further apart than the internal surfaces.

[0062] According to one embodiment, the belt comprises an outer layer overmolded onto the outer surface of the reinforcement.

[0063] The outer layer is preferably made of the same material as the body, i.e. in the first thermoplastic elastomer material.

[0064] The outer layer helps to protect the reinforcement.

[0065] According to a second aspect, the invention relates to a method for manufacturing a transmission belt comprising a body made in an elastomeric matrix and extending along an extension direction and a reinforcement attached to the body and extending over the width of the belt, the body comprising an internal drive surface comprising a plurality of teeth or ribs extending transversely along a transverse direction perpendicular to the extension direction of the belt.

[0066] The elastomeric matrix is ​​made of a first material comprising a thermoplastic elastomer, with the acronym "TPE"

[0067] The reinforcement consists of at least one layer of at least one rolled strip, preferably substantially flat.

[0068] The process comprising the following successive steps: - Positioning the reinforcement around a rigid cylindrical support with a width corresponding to at least n belts, preferably increased by an additional width to ensure clean extreme edges, - Placing and closing an injection mold on the reinforcement, - inject, at high pressure into the injection mold, a first material to form the elastomeric matrix of the body, and therefore the teeth of the n parallel belts, and thus bond said body to the reinforcement by overmolding, - cool the injection mold, either by letting it cool for a period of between 20s and 30s, or by applying cold to it; - demolding of the n belts from the injection mold; and - cutting of the individual belts with a cutting tool, for example using cutting rollers.

[0069] Alternatively, cutting could be carried out using knives, laser, water jet, etc...

[0070] The process of manufacturing the belt by injecting a material forming the body and therefore the teeth of the belt directly onto the flat reinforcement, makes it possible to simplify the manufacture of the belt without generating displacement of the reinforcement and without requiring a subsequent baking step.

[0071] Advantageously, once cut, the n resulting belts are separated.

[0072] The use of the elastomeric matrix of the body to assemble the turns of the reinforcement strip makes it possible to make a high-pressure injection without the turns of the reinforcement strip being pushed by the injected material, which is quasi-liquid and at high pressure.

[0073] High-pressure injection means a pressure between 500 bars and 3000 bars.

[0074] For example, during the injection stage, the first material is injected through injection cannulas provided in the mold into cavities of shapes corresponding to the teeth of the belt.

[0075] The injection step can be carried out, for example, in less than 3 seconds.

[0076] For example, during the reinforcement positioning step, the reinforcement strip is wound around the external cylindrical surface of the cylindrical support in the form of helical windings or helices or spirals.

[0077] In other words, the reinforcing strip is placed around the external cylindrical surface of the cylindrical support with a helical or spiral winding and therefore with a certain angle which will be a function of the width of the reinforcing strip and the radius of the belt.

[0078] The rigid cylindrical support prevents undulation of the reinforcing layer.

[0079] For example, the cylindrical support is delimited by an external cylindrical surface and two lateral surfaces.

[0080] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0081] [Fig.1] represents in detail in partial cross-section a transmission belt according to the state of the art;

[0082] [Fig.2] represents, very schematically, a general view of a transmission belt according to the invention;

[0083] [Fig.2A] illustrates in detail a flat portion of the transmission belt of the [Fig.2];

[0084] [Fig.3] is a detailed view of a transmission belt according to a first embodiment of the belt of [Fig.2];

[0085] [Fig.3A] is a detailed view of the belt reinforcement in [Fig.3];

[0086] [Fig.4] is a detailed view of a transmission belt according to a second embodiment of the belt of [Fig.2];

[0087] [Fig.5] is a detailed view of a transmission belt according to a third embodiment of the belt of [Fig.2];

[0088] [Fig.6], [Fig.7A], [Fig.8], [Fig.9], [Fig.10] and [Fig.l 1] illustrate the different stages of a belt manufacturing process [Fig.3];

[0089] [Fig.7B] represents a variant embodiment of figure 7; and

[0090] [Fig. 12] represents a flowchart of the manufacturing process of the belt of the [Fig.3].

[0091] In the following description, the terms "longitudinal", "transverse", "vertical", "front", "rear", "left" and "right" are defined according to the usual orthogonal coordinate system for transmission belts, shown in the drawings, and which includes:

[0092] - a longitudinal axis X, horizontal and oriented from left to right on the [Fig.2A] in the direction of movement of the transmission belt;

[0093] - a horizontal transverse axis Y, perpendicular to the longitudinal axis X and oriented of bottom to top on the [Fig.2A];

[0094] - a vertical axis Z, orthogonal to the longitudinal and transverse axes X and Y and directed from from back to front on the [Fig.2A].

[0095] Fig. 2 illustrates an example of a transmission belt, referenced 10 as a whole, configured to transmit rotational motion and / or mechanical power between two or more mechanical components, for example pulleys (not shown).

[0096] By "thickness" we mean the dimension of the belt 10 in the transverse direction Y, visible in figures 2A and 3 to 5.

[0097] By “length”, we mean the dimension of the belt 10 in the longitudinal direction X, visible in figures 2A and 3 to 5.

[0098] By "width" we mean the dimension of the belt 10 in the vertical direction Z, visible in figures 2A and 3 to 5.

[0099] The transmission belt 10 is here in the closed or assembled state, ready to be used for the mechanical drive of the mechanical components.

[0100] The transmission belt 10 comprises a body 12 made in an elastomeric matrix 12a and a reinforcement 14 attached to said body 12 by overmolding, as will be described later in the manufacturing process of the transmission belt 10.

[0101] The elastomeric body 12 is delimited transversely by an external surface 13 and an internal surface 15.

[0102] The terms "external" and "internal" are defined in terms of the center C of the transmission belt 10 when it is closed, the external surfaces being further apart than the internal surfaces.

[0103] The internal surface 15 of the body 12 forms a mechanical drive surface configured to drive a mechanical element (not shown).

[0104] As illustrated in Figures 2, 2A, 3, 4 and 5, the mechanical drive surface 15 comprises a plurality of ribs or teeth 16 each extending in a transverse direction perpendicular to the direction of extension of the transmission belt 10.

[0105] Each tooth 16 here has, in no way limitingly, a trapezoidal shape in cross-section. The general directions of the teeth 16 are substantially parallel to each other.

[0106] The teeth 16 extend over the entire length of the belt 10.

[0107] The teeth 16 are intended to be engaged in grooves or slots (not represented) of complementary shape, for example provided on pulleys on which the belt 10 is intended to be mounted.

[0108] As illustrated in the embodiment of [Fig.5], the transmission belt 10 comprises an outer layer 17 overmolded onto the outer surface of the reinforcement 14.

[0109] The outer layer 17 is preferably made of the same material as the body 12.

[0110] The outer layer 17 helps to protect the reinforcement 14. Body made of thermoplastic elastomer

[0111] The body 12 of the transmission belt 10 is formed from a die 12a made of a first thermoplastic elastomer material. The shaping can be carried out by molding, extrusion, or other known shaping techniques.

[0112] The body 12 contains the reinforcing strips 14a which are embedded in the matrix 12a.

[0113] In the example illustrated in [Fig.4], the thickness of matrix 12a between the base of the teeth 16 and the reinforcing layer 14 is between 0.1mm and 0.4mm. Thermoplastic elastomer

[0114] A thermoplastic elastomer is a block copolymer comprising at least one elastomer block and at least one thermoplastic block, and the total thermoplastic elastomer content being in the range of 65 to 100 parts per hundred parts of elastomer.

[0115] In other words, thermoplastic elastomers have an intermediate structure between thermoplastic polymers and elastomers. They are block copolymers, consisting of rigid, thermoplastic blocks linked by flexible, elastomer blocks.

[0116] 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.

[0117] In this application, reference is made to the glass transition temperature of the TPE, which refers to the Tg relative to the elastomer block. The TPE preferably has a glass transition temperature ("Tg") that is preferably less than or equal to 25 °C, more preferably less than or equal to 10 °C. A Tg value above these minimums may reduce the performance of the underlayer during very low-temperature use; for such use, the Tg of the TPE is even more preferably less than or equal to -10 °C. Also preferably, the Tg of the TPE is greater than -100 °C.

[0118] As is known, TPEs exhibit two peak glass transition temperature (Tg, measured according to ASTM D3418), the lower temperature being relative to the elastomer portion of the TPE, and the higher temperature being relative to the thermoplastic portion of the TPE. Thus, flexible blocks of TPE are defined by a Tg below ambient temperature (25°C), while rigid blocks have a Tg above 80°C.

[0119] Thermoplastic blocks having a Tg (or Tf, as the case may be) greater than or equal to 80°C may be made from polymerized monomers of various kinds; in particular, they may constitute the following blocks or mixtures thereof: polyolefins (polyethylene, polypropylene); polyurethanes; polyamides; polyesters; polyacetals; polyethers (polyethylene oxide, polyphenylene) ether); phenylene polysulfides; polyfluorides (FEP, PFA, ETFE); polystyrenes (detailed below); polycarbonates; polysulfones; polymethyl methacrylate; polyetherimide; thermoplastic copolymers such as acrylonitrile-butadiene-styrene (ABS) copolymer.

[0120] Alternatively, other monomers could be provided.

[0121] For example, TPE is a copolymer in which the elastomer portion is saturated, and comprise styrene blocks and alkylene blocks. The alkylene blocks are preferably ethylene, propylene, or butylene. More preferably, this TPE elastomer is selected from the following group, consisting of linear or star-shaped diblock, 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.

[0122] 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 diblock, linear or star 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.

[0123] For example, TPE is also a linear or star copolymer whose elastomeric blocks comprise a saturated part and an unsaturated part such as, for example, styrene / butadiene / butylene (SBB), styrene / butadiene / butylene / styrene (SBBS) or a mixture of these copolymers.

[0124] The use of a thermoplastic elastomer to manufacture the body 12 and therefore the teeth 16 of the transmission belt 10, in particular by high-pressure injection, has the advantage of being economical, ensuring good belt productivity, and eliminating the need for an additional vulcanization step. The use of a thermoplastic elastomer reduces the wear rate of the teeth 16, the coefficient of friction with the pulleys, and significantly improves the energy efficiency of the transmission belt 10.

[0125] Furthermore, the body 12 can be recycled after use of the belt.

[0126] The use of hydrogenated elastomeric thermoplastics reduces aging compared to the first material or unsaturated elastomeric thermoplastics. Reinforcements

[0127] Reinforcement 14 is illustrated in detail in [Fig.3A].

[0128] The reinforcement 14 is composed of at least one wrapped strip 14a.

[0129] As illustrated, there are several turns of a strip.

[0130] Strip 14a is preferably substantially flat.

[0131] By "substantially flat" is meant a strip comprising a thickness along the transverse axis Y at least twice as much as the width of the strip, along the vertical axis Z.

[0132] Such a substantially flat reinforcement 14 not only reduces the overall thickness of the reinforcement and therefore of the belt, but also increases the flexibility in bending in order to be able to adapt more easily to a mechanical component such as a pulley.

[0133] Furthermore, overmolding the body 12 including the belt teeth directly onto the flat reinforcement 14 simplifies the manufacture of the belt without generating displacement of the reinforcement and without requiring a subsequent baking step.

[0134] As illustrated in [Fig.3A], and in no way limitingly, the reinforcement 14 comprises two layers of strips superimposed along the transverse axis, the first layer of strips radially inside and a second layer of strips radially outside.

[0135] As illustrated in [Fig.3A], and in no way limitingly, the strips 14a of said first and second layers of strips are arranged in a juxtaposed manner.

[0136] Each strip 14a extends in the direction parallel to the direction of extension of the belt 10.

[0137] Generally, the reinforcement 14 comprises at least one layer of at least one strip 14.

[0138] As illustrated in [Fig. 6], the strip 14a of the reinforcement 14 is wound in a helix or spiral forming an angle between 0° and 5° with respect to the direction of extension of the belt. Each spiral is contiguous with the previous one.

[0139] For example, the reinforcing strip 14a is made up of high-modulus reinforcing elements (not shown). The reinforcing elements are coated with a matrix.

[0140] Preferably, the polymer matrix constituting the strips comprises a thermosetting polymer or a thermoplastic polymer, used alone respectively or in cutting with other polymers.

[0141] The matrix of the strips may comprise a rubber composition based on at least one elastomer, dienic or non-dienic, for example thermoplastic, preferably of a crosslinked or crosslinkable type composition and having, in the crosslinked state, a secant modulus in extension at 10% elongation greater than or equal to 5MPa, preferably greater than or equal to 1OMPa.

[0142] According to another preferred embodiment of the invention, this main matrix surrounding the rubber composition strips can also exhibit very high rigidity, i.e. a MA10 modulus greater than or equal to 30 MPa.

[0143] For example, the diene elastomer is more preferentially chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), butadiene copolymers, isoprene copolymers, and mixtures of these elastomers, such copolymers being in particular chosen from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR) and isoprene-butadiene-styrene copolymers (SBIR).

[0144] Preferably, the polymer matrix constituting the strips can be chosen from thermosetting resins of the type polyepoxide, unsaturated polyester, vinyl ester, cyanate ester, polyurethanes and a cutting of these resins, or from thermoplastic resins such as polyesters (PET, PBT, PEN, PBN), polyamides (nylon, aramid), polyamides, polyethersulfones, polyphenylenesulfone, polyketones (PK, PEEK).

[0145] Particularly suitable among the aforementioned resins are thermosetting resins having a glass transition temperature greater than or equal to 160°C and thermoplastic resins having a melting temperature greater than or equal to 180°C.

[0146] Note that reinforcing fillers (silica, carbon black), or thermoplastic fillers or elastomeric fillers may be added to the above resins.

[0147] In the present application, high modulus shall be understood to mean an extension modulus (Young's modulus) greater than or equal to 55 GPa.

[0148] Such an extension module is measured in accordance with ASTM D4848-98 (2012).

[0149] The reinforcing elements are preferably oriented in the direction of extension of the strip 14a.

[0150] Each reinforcing element, useful for the needs of the invention, can be in different forms, for example in the form of fibers, preferably in the form of a single wire, such as a continuous or discontinuous monofilament, or an assembly of wires, whether these wires are twisted together, for example, in the form of a cable, or essentially parallel to each other.

[0151] Each reinforcing element is more preferably in the form of a single wire or an assembly of wires, for example a cable or a strand manufactured with devices and wiring or stranding processes known to those skilled in the art, which are not described here for the sake of simplicity.

[0152] The reinforcement can also be in the form of a ribbon or film.

[0153] The term "wire" or "fibre" generally means any long, thin element of large length relative to its cross-section, whatever the shape of the latter, for example circular, oblong, rectangular or square, or even flat, this wire can be straight or non-straight, for example twisted, or wavy.

[0154] By "film" or "strip", we generally mean a long, thin element, of great length relative to its cross-section, whose cross-section has a width-to-thickness ratio greater than 5, preferably greater than 10.

[0155] Preferably, each reinforcing element is metallic or textile.

[0156] According to a preferred embodiment of the invention, the reinforcing elements are high modulus fibers comprising glass fibers. Preferably, glass fibers are predominant, i.e., they represent more than 50% of the fibers in the same layer.

[0157] In this application, "high modulus" shall mean an extensional modulus (Young's modulus) greater than or equal to 55 GPa.

[0158] Such an extension module is measured in accordance with ASTM D4848-98 (2012).

[0159] More preferably still, the reinforcing elements are made of glass fibers.

[0160] Preferably, the volume ratio of polymer matrix / glass fibers ranging from 30 / 70, preferably from 35 / 65, to 80 / 20, preferably from 70 / 30 and being preferably about 45 / 55.

[0161] According to another preferred embodiment of the invention, the reinforcing elements are high-modulus fibers comprising carbon fibers. Preferably, the carbon fibers constitute the majority, i.e., represent more than 50% of the fibers.

[0162] More preferably still, the reinforcing elements are made of carbon fibers.

[0163] Preferably, the polymer matrix / carbon fiber volume ratio ranging from 30 / 70, preferably from 35 / 65 to 90 / 10, preferably to 60 / 40, and preferably being about 50 / 50.

[0164] According to other preferred embodiments of the invention, reinforcing elements include aramid fibers, basalt fibers or quartz fibers.

[0165] The reinforcement 14 has a transverse dimension, i.e. a thickness, between 0.1mm and 6mm.

[0166] Fig. 12 illustrates a manufacturing process 30 for the transmission belt of Fig. 3.

[0167] The manufacturing process 30 will be described with reference to Figures 6 to 11 which illustrate certain steps of said process 30.

[0168] As illustrated in [Fig.6], the process 30 for manufacturing the transmission belt 10 includes a first step 31 of positioning the reinforcement 14 around a rigid cylindrical support 20 over a width corresponding to n belts plus an additional width to have clean extreme edges.

[0169] The cylindrical support 20 is delimited by an external cylindrical surface 21 and two lateral surfaces 22, 23.

[0170] The reinforcement 14 is wound around the external cylindrical surface 21 of the cylindrical support 20 in the form of helical windings whose winding angle is between 0° and 5°, preferably between 0° and 3°, preferably between 0° and 1°.

[0171] In other words, the reinforcement 14 is placed around the external cylindrical surface 21 of the cylindrical support 20 with a helical or spiral winding and therefore with a certain winding or helix angle which will be a function of the width of the reinforcement strip 14a and the radius of the belt 10.

[0172] For example, if the width, i.e. the dimension along the vertical direction Z, of the strip 14a is 10 mm and the radius of the belt 10 is 10 cm, the winding angle will be 0.9°.

[0173] According to another example, if the width of the strip 14a is 5 mm and the radius of the belt 10 is 10 cm, the winding angle will be 0.45°.

[0174] It is important that this installation winding angle be small to limit unwanted lateral thrust. Generally, the installation winding angle is less than 2°. It can be adjusted by the width of the strip 14a.

[0175] The rigid cylindrical support 20 prevents undulation of the reinforcing layer 14.

[0176] In a second step 32, an injection mold 25 is placed on the reinforcement layer 14 and said injection mold is closed by pressing it onto the reinforcement layer 14, as seen in [Fig.7A] or 7B.

[0177] In a third step 33, the material of the elastomeric matrix 12a forming the body 12, and therefore the teeth 16, is injected under high pressure into the injection mold 25. The material is injected through injection cannulas 26 provided in the mold 25 into cavities 27 of shapes corresponding to the teeth 16 of the belt 10.

[0178] The injection step 33 allows n parallel belts to be produced.

[0179] The term "n belts" means several belts, for example n is equal to at least two, preferably at least five, for example at least ten.

[0180] The injection step can be carried out in less than 3 seconds.

[0181] The use of the elastomeric matrix 12a forming the body 12 of the belt to assemble the turns of the reinforcing strip 14a makes it possible to make a high-pressure injection without these reinforcing strips 14a being pushed by the injected material, quasi-liquid and at high pressure.

[0182] High-pressure injection means a pressure between 500 bar and 3000 bar.

[0183] In a fourth step 34, the mold is cooled, either by letting it cool for a period of between 20s and 30s, or possibly by applying cold.

[0184] Then, in a fifth step 35, the body 12 is removed from the injection mold 25 so as to obtain the future n belts.

[0185] In a sixth step 36, the unit belts are cut according to cutting zones Zl, visible on the [Fig. 10].

[0186] In the example illustrated in [Fig. 11], the cutting is carried out using cutting rollers 28.

[0187] Alternatively, cutting could be carried out using knives, laser, water jet, etc...

[0188] Finally, once cut, the n resulting belts are removed from cylinder 22 and separated at step 37.

[0189] The installation of the flat reinforcements 14 of a certain width causes a drop at the beginning and end of the cylindrical support 20. It is therefore important that the cylindrical support 20 allows for the production of a large number of belts after the cutting step, limiting this drop to the first and last belt. The drops of the first and last belt are visible in [Fig. 10].

[0190] In the context of the invention, the carbon products mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass.

[0191] The term "phr" (in English) means, for the purposes of this patent application, part by weight per hundred parts of elastomer, thermoplastic and non-thermoplastic combined. For the purposes of the present invention, thermoplastic elastomers (TPEs) are included among the elastomers.

[0192] Thanks to the particular structure of the transmission belt including a reinforcement comprising reinforcing strips, the belt has a lower flexural rigidity, thus facilitating its insertion onto pulleys.

[0193] Furthermore, the belt manufacturing process by injecting a material forming the body and therefore the teeth of the belt directly onto the flat reinforcement allows to simplify the manufacture of the belt without generating displacement of the reinforcement and without requiring a subsequent cooking step.

[0194] Finally, the use of a thermoplastic elastomer material for the body, and therefore the teeth of the belt, makes it possible to reduce energy losses and improve the energy efficiency of the belt.

Claims

Demands

1. Transmission belt (10) comprising a body (12) made of an elastomeric matrix (12a) and extending along an extension direction (X) and a reinforcement (14) integral with the body (12) and extending over the width of the belt (10), the body (12) comprising an internal drive surface (15) comprising a plurality of teeth (16) extending transversely along a transverse direction (Y) perpendicular to the extension direction (X) of the transmission belt, characterized in that the elastomeric matrix (12a) is made of a first material comprising a thermoplastic elastomer comprising a block copolymer comprising at least one elastomer block and at least one thermoplastic block, and the total thermoplastic elastomer content being in the range of 65 to 100 parts per hundred (parts by weight per hundred parts of elastomer),in that said elastomeric matrix (12a) is overmolded onto the reinforcement (14) and in that the reinforcement (14) is composed of at least one layer of at least one wound strip (14a).

2. Transmission belt (10) according to claim 1, wherein the strip (14a) of the reinforcement (14) is substantially flat.

3. Transmission belt (10) according to claim 1 or 2, wherein the strip (14a) of the reinforcement (14) is wound in a helix forming an angle between 0° and 5° along the direction of extension of the belt, each helix being contiguous with the previous one.

4. Transmission belt (10) according to any one of the preceding claims, wherein the strip (14a) extends in the direction parallel to the extension direction (X) of the belt (10).

5. Transmission belt (10) according to any one of the preceding claims, wherein the reinforcing strip (14a) is made up of high modulus reinforcing elements embedded in a matrix.

6. Transmission belt (10) according to claim 5, wherein the shape of the reinforcing elements is chosen from fibers, single wires, an assembly of wires, cables, tapes and films.

7. Transmission belt (10) according to claim 5 or 6, wherein the matrix composing the reinforcing strip is selected from a thermosetting polymer or a thermoplastic polymer, used alone respectively or in cutting with other polymers.

8. Transmission belt (10) according to any one of the preceding claims, wherein the thickness of the elastomeric matrix (12a) forming the body (12) located transversely between the base of the teeth (16) and the reinforcement (14) is between 0.1mm and 0.4mm.

9. Transmission belt (10) according to any one of the preceding claims, wherein the reinforcement (14) has a transverse dimension between 0.1mm and 6mm.

10. Transmission belt (10) according to any one of the preceding claims, further comprising an outer layer (17) overmolded onto the outer surface of the reinforcement (14).

11. A method of manufacturing (30) a transmission belt (10) comprising a body (12) made of an elastomeric matrix (12a) and extending along an extension direction (X) and a reinforcement (14) integral with the body (12) and extending over the width of the belt (10), the body (12) comprising an internal drive surface (15) comprising a plurality of teeth (16) extending transversely along a transverse direction (Y) perpendicular to the extension direction (X) of the body (12), the elastomeric matrix (12a) being made of a first material comprising exclusively a thermoplastic elastomer comprising a block copolymer comprising at least one elastomer block and at least one thermoplastic block, and the total thermoplastic elastomer content being in the range of 65 to 100 parts per hundred parts of elastomer,the reinforcement (14) being composed of at least one layer of at least one wound strip (14a), the method comprising the following successive steps: - positioning the reinforcement (14) around a rigid cylindrical support (20) over a width corresponding to at least n strips, n being greater than or equal to two; - placing and closing an injection mold (25) on the reinforcement (14); - inject, at high pressure into the injection mold (25), a first material to form the elastomeric matrix (12a) of the body (12), and thus the teeth (16) of n parallel belts (10), - cool the injection mold (25); - demold the n belts from the injection mold (25); and - cut unit belts with a cutting tool (28).

12. A manufacturing method (30) according to claim 11, wherein during the injection step, the first material is injected through injection cannulas (26) provided in the injection mold (25) into cavities (27) of shapes corresponding to the teeth (16) of the belt (10).

13. A manufacturing method (30) according to claim 11 or 12, wherein during the positioning step of the reinforcement (14), the strip (14a) of the reinforcement (14) is wound around an external cylindrical surface (21) of the cylindrical support (20) in the form of helical windings.

Images