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

Abstract

Transmission belt (10) comprising a body (12) made of an elastomeric matrix (12a) and extending in a direction of extension (X) and a reinforcement (14) integral with the body (12) and extending over the width of the belt, the body (12) comprising a mechanical drive surface (15) comprising a plurality of teeth (16) extending transversely in a transverse direction (Y) perpendicular to the direction of extension (X). The elastomeric matrix (12a) is made of a first material comprising an elastomeric thermoplastic, 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). Figure for abstract: Fig 3

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 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 synchronously.

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

[0004] In this regard, reference may be made to [Fig. 1] which illustrates such a belt 1 comprising a body 2 in which reinforcing threads 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] Belts are generally made of rubber and require a molding process which can cause movements of the linear cables, as well as a vulcanization process requiring a baking step and therefore an increase in manufacturing time.

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

[0007] The aim of the invention is to propose 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 from an elastomeric matrix and extending in a direction of extension and a reinforcement integral with 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 in a transverse direction perpendicular to the direction of extension of the transmission belt.

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

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

[0011] The use of an elastomer thermoplastic to manufacture the body and therefore the teeth of the transmission belt in particular, by high-pressure injection, has the following advantages: advantage of being economical, ensuring good belt productivity and does not require an additional vulcanization or hot crosslinking step. The use of an elastomer thermoplastic reduces the wear rate of the teeth, the coefficient of friction with the pulleys and significantly improves the energy efficiency of the transmission belt.

[0012] Furthermore, the body can be recycled after use of the belt. The use of hydrogenated elastomeric thermoplastics further allows for reduced aging compared to the first material or unsaturated elastomeric thermoplastics.

[0013] The reinforcement is composed of at least one layer of at least one wound strip.

[0014] The strip is preferably substantially flat.

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

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

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

[0018] Such a substantially flat reinforcement not only makes it possible to reduce the overall thickness of the reinforcement and therefore of the belt, but also to increase the flexibility in bending in order to be able to adapt more easily to a mechanical member such as a pulley.

[0019] Furthermore, overmolding the body comprising the teeth of the belt directly onto the flat reinforcement makes it possible to simplify the manufacture of the belt without generating any movement of the reinforcement and without requiring a subsequent cooking 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 on the inside and a second layer of strip is radially on the outside.

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

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

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

[0024] Preferably, the strip 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 fibers, unit yarns, an assembly of yarns, cables, ribbons and films.

[0028] Each reinforcing element, useful for the purposes of the invention, may be presented in different forms, preferably in the form of a unitary wire, such as a continuous or discontinuous monofilament, or of 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 cabling or stranding devices and methods known to those skilled in the art, which are not described here for the sake of simplicity of the description.

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

[0031] By "thread" or "fiber" is generally meant any elongated element of great length relative to its cross-section, whatever the shape of the latter, for example circular, oblong, rectangular or square, or even flat, this wire being able to be straight or non-straight, for example twisted, or wavy.

[0032] By "film" or "ribbon" is generally meant an elongated element, of great length relative to its cross-section, the cross-section of which 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, the glass fibers are in the majority, i.e. they represent more than 50% of the fibers in the same layer.

[0035] In the present application, the term “high modulus” will be understood to mean an extension modulus (Young’s modulus) greater than or equal to 55 GPa.

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

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

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

[0039] According to another preferred embodiment of the invention, the reinforcement elements necessarily are high modulus fibers including carbon fibers. Preferably, carbon fibers are in the majority, i.e. represent more than 50% of the fibers.

[0040] More preferably still, the reinforcing elements are made of carbon fibers.

[0041] 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 approximately 50 / 50.

[0042] According to other preferred embodiments of the invention, reinforcing elements comprise 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 blend 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 0.1 mm and 0.4 mm.

[0045] For example, the reinforcement has a transverse dimension, that is to say a thickness, between 0.1 mm and 6 mm.

[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.

[0047] Each tooth has, in a non-limiting manner, 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 content of thermoplastic elastomer being within a range varying from 65 to 100 pce (parts by weight 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, connected by flexible, elastomeric blocks.

[0051] The first 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.

[0052] The number-average molecular mass (denoted Mn) of the TPE is preferentially between 30,000 and 500,000 g / mol, more preferably between 40,000 and 400,000 g / mol.

[0053] In the present application, when reference is made to the glass transition temperature of the TPE, this is 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 can reduce the performance of the underlayer 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.

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

[0055] 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); phenylene polysulfides; polyfluorinated materials (FEP, PFA, ETFE); polystyrenes (detailed below); polycarbonates; polysulfones; polymethylmethacrylate; polyetherimide; thermoplastic copolymers such as acrylonitrile-butadiene-styrene copolymer (ABS).

[0056] Alternatively, other monomers could be provided.

[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 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.

[0059] According to another example, the 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.

[0060] For example also, TPE is a linear or star copolymer whose elastomer 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 relative to the center of the drive belt, with the external surfaces being further apart than the internal surfaces.

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

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

[0064] The outer layer protects the reinforcement.

[0065] According to a second aspect, the invention relates to a method for manufacturing a transmission belt comprising a body made from an elastomeric matrix and extending in a direction of extension and a reinforcement integral with 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 in a transverse direction perpendicular to the direction of extension of the belt.

[0066] The elastomeric matrix is ​​made from a first material comprising a thermoplastic elastomer, with the acronym “TPE”.

[0067] The reinforcement is composed of at least one layer of at least one wound strip, preferably substantially flat.

[0068] The method comprising the following successive steps: - positioning the reinforcement around a cylindrical support, rigid over a width corresponding to at least n belts, preferably increased by an additional width to have clean extreme edges, - place and close 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 belts parallel to each other, and thus secure 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 the unit belts with a cutting tool, for example using cutting rollers.

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

[0070] The method 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 manufacturing of the belt without generating any movement of the reinforcement and without requiring a subsequent cooking step.

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

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

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

[0074] For example, during the injection step, 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 turns.

[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 undulations of the reinforcement layer.

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

[0080] 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:

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

[0082] [Fig.2] very schematically represents 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 [Fig.2];

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

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

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

[0087] [Fig.5] is a detail 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.ll] illustrate the different stages of a manufacturing process for the belt of the [Fig.3] ;

[0089] [Fig.7B] represents an alternative embodiment of Figure 7; and

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

[0091] 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:

[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 transverse axis Y, horizontal, perpendicular to the longitudinal axis X and oriented bottom up on [Fig.2A];

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

[0095] [Fig.2] 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).

[0096] By “thickness” is meant the dimension of the belt 10 in the transverse direction Y, visible in Figures 2A and 3 to 5.

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

[0098] By “width” is meant 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 from an elastomeric matrix 12a and a reinforcement 14 secured to said body 12 by overmolding, as will be described later in the method of manufacturing 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 relation to the center C of the transmission belt 10 when 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 member (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 has here, in a non-limiting manner, 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 grooves (not re presented) 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 on 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 makes it possible to protect the reinforcement 14. Thermoplastic elastomer body

[0111] The body 12 of the transmission belt 10 is shaped from a matrix 12a made of first thermoplastic elastomer material. The shaping can be carried out by molding, by 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 content of thermoplastic elastomer being within a range varying from 65 to 100 pce (parts by weight 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, connected by flexible, elastomeric blocks.

[0116] The number-average molecular mass (denoted Mn) of the TPE is preferably between 30,000 and 500,000 g / mol, more preferably between 40,000 and 400,000 g / mol.

[0117] In the present application, when reference is made to the glass transition temperature of the TPE, this is 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 can reduce the performance of the underlayer 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.

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

[0119] 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); phenylene polysulfides; polyfluorinated materials (FEP, PFA, ETFE); polystyrenes (detailed below); polycarbonates; polysulfones; polymethylmethacrylate; polyetherimide; thermoplastic copolymers such as acrylonitrile-butadiene-styrene copolymer (ABS).

[0120] Alternatively, other monomers could be provided.

[0121] For example, TPE is a copolymer whose elastomer part 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 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, the 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.

[0123] For example also, TPE is a linear or star copolymer whose elastomer 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 an elastomer thermoplastic 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, of ensuring good productivity of the belt and does not require an additional vulcanization step. The use of an elastomer thermoplastic 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 makes it possible to reduce aging compared to the first material or to unsaturated elastomeric thermoplastics. Reinforcement

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

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

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

[0130] The 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 makes it possible to reduce the overall thickness of the reinforcement and therefore of the belt, but also to increase the flexibility in flexion in order to be able to adapt more easily to a mechanical organ such as a pulley.

[0133] Furthermore, the overmolding of the body 12 comprising the teeth of the belt directly onto the flat reinforcement 14 makes it possible to simplify the manufacture of the belt without generating any movement of the reinforcement and without requiring a subsequent cooking step.

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

[0135] As illustrated in [Fig.3A], and in a non-limiting manner, the strips 14a of said first and second layers of strips are arranged juxtaposed.

[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 turn forming an angle between 0° and 5° depending on the direction of extension of the belt. Each turn is joined to 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 blend with other polymers.

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

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

[0143] For example, the diene elastomer is more preferably 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 chosen in particular 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 polyepoxide, unsaturated polyester, vinylester, cyanate ester type, polyurethanes and a blend 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 will be understood to mean an extension modulus (Young's modulus) greater than or equal to 55 GPa.

[0148] Such extension modulus 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 purposes of the invention, may be in different forms, for example in the form of fibers, preferably in the form of a unitary thread, such as a continuous or discontinuous monofilament, or an assembly of threads, whether these threads 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 cabling or stranding devices and methods known to those skilled in the art, which are not described here for the sake of simplicity of the description.

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

[0153] By "thread" or "fiber" is generally meant any elongated element of great length relative to its cross-section, whatever the shape of the latter, for example circular, oblong, rectangular or square, or even flat, this wire being able to be straight or non-straight, for example twisted, or wavy.

[0154] By "film" or "ribbon" is generally meant an elongated element, of great length relative to its cross-section, the cross-section of which has a shape ratio, width to thickness, 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, the glass fibers are in the majority, i.e. they represent more than 50% of the fibers in the same layer.

[0157] In the present application, the term “high modulus” will be understood to mean an extension modulus (Young’s modulus) greater than or equal to 55 GPa.

[0158] Such extension modulus 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 35 / 65, to 80 / 20, preferably 70 / 30 and preferably being approximately 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 are in 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 approximately 50 / 50.

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

[0165] The reinforcement 14 has a transverse dimension, that is to say a thickness, of between 0.1 mm and 6 mm.

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

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

[0168] As illustrated in [Fig.6], the method 30 for manufacturing the transmission belt 10 comprises a first step 31 of positioning the reinforcement 14 around a cylindrical support 20, rigid over a width corresponding to n belts plus a complementary 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 reinforcing 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 laying winding angle is small to limit parasitic lateral thrust. Generally, the laying winding angle is less than 2°. It can be adjusted by the width of the strip 14a.

[0175] The rigid cylindrical support 20 prevents undulations of the reinforcement layer 14.

[0176] During 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 visible in [Fig.7A] or 7B.

[0177] During a third step 33, the material of the elastomeric matrix 12a forming the body 12, and therefore the teeth 16, is injected at 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 makes it possible to produce n belts parallel to each other.

[0179] By “n belts” is meant 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 performed 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 carry out a high-pressure injection without these reinforcing strips 14a being pushed by the injected material, which is almost liquid and at high pressure.

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

[0183] During 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 to it.

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

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

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

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

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

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

[0191] 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.

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

[0193] Furthermore, the method 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 manufacturing of the belt without generating any movement 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

Claims

1. Transmission belt (10) comprising a body (12) made of an elastomeric matrix (12a) and extending in a direction of extension (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 in a transverse direction (Y) perpendicular to the direction of extension (X) of the transmission belt, characterized in that the elastomeric matrix (12a) is made of a first material comprising an elastomeric thermoplastic, in that said elastomeric matrix (12a) is overmolded on the reinforcement (14) and in that the reinforcement (14) is composed of at least one layer of at least one wound strip (14a).

2. A 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, in which the strip (14a) of the reinforcement (14) is wound in a helix forming an angle between 0° and 5° in the direction of extension of the belt, each helix being contiguous to the previous one.

4. A transmission belt (10) according to any preceding claim, wherein the strip (14a) extends in the direction parallel to the extension direction (X) of the belt (10).

5. A transmission belt (10) according to any preceding claim, wherein the reinforcing strip (14a) is comprised of high modulus reinforcing elements embedded in a matrix.

6. A transmission belt (10) according to claim 5, wherein the shape of the reinforcing elements is selected from fibers, unit yarns, an assembly of yarns, cables, ribbons and films.

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

8. Transmission belt (10) according to any one of the preceding claims, in which 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 0.1 mm and 0.4mm.

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

10. A transmission belt (10) according to any preceding claim, 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 from an elastomeric matrix (12a) and extending in a direction of extension (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 in a transverse direction (Y) perpendicular to the direction of extension (X) of the body (12), the elastomeric matrix (12a) being made from a first material comprising exclusively an elastomeric thermoplastic, 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 cylindrical support (20), rigid over a width corresponding to at least n belts, n being greater than or equal to two;- placing and closing an injection mold (25) on the reinforcement (14); - injecting, 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 belts (10) parallel to each other, - cooling the injection mold (25); - demolding the n belts from the injection mold (25); and - cutting out unit belts with a cutting tool (28).;

12. 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) to 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 step of positioning 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.

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