Synchronous transmission belt and an assembly comprising this belt and an associated pulley

Abstract

Synchronous transmission belt (100) having an elastomer-based body (102) comprising a dorsal portion (104), a ventral portion (106) and a set of traction cords (110) between the dorsal portion (104) and the ventral portion (106), the ventral portion having a plurality of transverse teeth (112, 112'), each transverse tooth (112, 112') having in cross section a first profile (116) with two inclined flanks (117) connected by at least one rounded portion, each transverse tooth having a tooth height H1, and a plurality of longitudinal teeth (114, 114'), each longitudinal tooth extending between two transverse teeth substantially perpendicularly to said transverse teeth and having in cross section a second profile (118) with two inclined flanks (119) connected by at least one rounded portion, each longitudinal tooth having a non-zero tooth height H2, which is less than or equal to the tooth height H1.

Description

Description TITLE: SYNCHRONOUS TRANSMISSION BELT AND AN ASSEMBLY COMPRISING THIS BELT AND AN ASSOCIATED PULLEY Technical field of the invention

[0001] The present invention relates to a synchronous transmission belt. The invention also relates to an assembly comprising the belt and at least one associated pulley. The invention also relates to a method of manufacturing such a belt. Technological background

[0002] Generally speaking, belt power transmission is widespread and concerns very varied application areas, for example the automotive sector, the conveyance of objects, or even the transmission for velocipedes (commonly called bikes), such as a bicycle.

[0003] Some applications require the transmission of very high torques. Not all types of belts, for example poly-V ® belts, i.e., grooved in the longitudinal direction of the belt, necessarily have the required performance level for such applications. Synchronous systems are therefore preferred, i.e., a synchronous belt with transverse teeth and corresponding pulleys. This is particularly the case for bicycle applications.

[0004] However, these synchronous transmission systems require perfect parallelism of the rotation axes and good alignment of the pulleys. Otherwise, the belt risks moving laterally on the pulleys and thus deteriorating and / or coming off them.

[0005] To prevent these lateral movements, it can be useful for the transmission system to include a means of guidance. There are solutions that consist of placing flanges on the pulley, on either side of the belt. However, the belt tends to rub against these elements, which accelerates its wear, and prevents the evacuation of foreign elements such as water or gravel.

[0006] Other solutions propose central machining in the tooth of the synchronous belt, thus defining a groove which will be housed on a web corresponding material arranged in the center of the pulley with which the belt cooperates. This is for example what is proposed in document EP-B1-3 478 561.

[0007] However, this principle is restrictive in terms of the production of pulleys and the machining of the belt teeth. In addition, the groove created on the belt by this machining can be damaged by the insertion of foreign bodies during operation. These foreign bodies can, for example, be mud or gravel when such a system is used for a bicycle application.

[0008] Other solutions propose a negative of the first solution, that is to say that the belt comprises, in addition to the synchronous teeth, at least one web which engages in a groove made in the corresponding pulley. This configuration is notably proposed by documents WO-A1 -2021 / 180678.

[0009] Also, documents EP-B1 -3 478 561 and WO-A1 -2021 / 180678 each propose a synchronous belt whose transverse teeth each have a rounded top, in particular with an overall arc-shaped profile. The web, for its part, whether positive (on the pulley) or negative (on the belt), then only fulfills a lateral locking function for the belt.

[0010] Document CN-U-208 651 535 proposes a synchronous belt whose transverse teeth each have a right trapezoidal profile. This document also proposes a longitudinal V-shaped tooth between each transverse tooth.

[0011] Generally speaking, to maximize the transmission of torque between two pulleys, the belt must rest on the pulley with the largest possible contact surface, while limiting the mechanical constraints linked, in particular, to the winding of the belt and the shape of the teeth.

[0012] Such constraints have the effect of accentuating the deformation of the belt teeth, or even causing the appearance of cracks, particularly at the root of the teeth, and therefore accelerating the deterioration of the belt.

[0013] Also, an objective of the invention is to propose a synchronous transmission belt which does not have at least one of the aforementioned drawbacks.

[0014] Another objective of the invention is to propose a synchronous transmission belt offering improved performance on the torque transmissible between two pulleys. Summary of the invention

[0015] There is therefore proposed a synchronous transmission belt comprising an elastomer-based body comprising a dorsal portion, a ventral portion and a set of traction cords between the dorsal portion and the ventral portion, the ventral portion having, on the one hand, a plurality of transverse teeth, each transverse tooth having in section a first profile with two inclined flanks converging towards each other in the direction of a peak of the transverse tooth, the flanks of the transverse tooth being connected by at least one rounded part, each transverse tooth having a tooth height H1, and, on the other hand, a plurality of longitudinal teeth, each longitudinal tooth extending between two transverse teeth substantially perpendicular to the transverse teeth and having in section a second profile with two inclined flanks, converging towards each other in the direction of a peak of the longitudinal tooth,the flanks of the longitudinal tooth being connected by at least one rounded part, each longitudinal tooth having a tooth height H2, this height H2, non-zero, being less than or equal to the tooth height H1.,

[0016] Thus, thanks to the invention, an improvement in the torque transmitted by the belt and its stability are ensured. Indeed, in use, the contact surface between the belt and the pulley intended to receive it is high thanks to the profiles of the teeth, and in particular thanks to the longitudinal teeth which not only have a function of guiding the belt on the pulley but participate, with the shape of their profile, in the transmission of the torque, together with the transverse teeth. The presence of cables improving the traction modulus of the belt, the transmissible torque can be controlled.

[0017] The belt according to the invention may comprise one or more of the following characteristics, taken in isolation from each other or in combination with each other: - the tooth height H2, non-zero, of each longitudinal tooth is strictly less than the tooth height H1 of each transverse tooth, - the tooth height H2 of each longitudinal tooth is such that 0.4 x H1 < H2 < 0.8 x H1, - each transverse tooth has a first trapezoidal profile in section with rounded angles, - the first profile of each transverse tooth comprises two convex summit portions, these convex summit portions being located on either side of a summit portion, and two concave portions, said concave portions being located on either side of a base of the transverse tooth, - each convex top portion of the first profile has an approximate radius of curvature of between 0.6 mm and 1.4 mm, and each concave portion has a radius of curvature of between 0.6 mm and 1.4 mm, - the second profile of each longitudinal tooth comprises two concave portions, these concave portions being located on either side of a base of the longitudinal tooth, and a tooth apex, said apex being convex, - each concave portion of the second profile has a radius of curvature of between 0.8 mm and 1.6 mm, and said vertex of the second profile has a radius of curvature of between 0.8 mm and 1.6 mm, - the second profile of each longitudinal tooth is a trapezoidal profile with rounded corners, - the synchronous transmission belt comprises a coating arranged at an external surface of the plurality of transverse and longitudinal teeth, - the elastomer-based belt body is a material selected from an ethylene-alpha-olefin or a polyurethane, and the coating is a textile material or an elastomer thermoplastic film, - each cord of the set of traction cords is made of aramid, polyester, glass fibers or carbon fibers or a combination thereof, - the transverse teeth are distributed with a pitch of 11 mm.

[0018] The invention also relates to an assembly comprising at least one pulley and a synchronous transmission belt as described above, each pulley comprising: two circumferential rows of teeth parallel to each other and configured to receive the tooth recesses of the plurality of transverse teeth of the belt, and - a circumferential groove, separating the two circumferential rows of teeth, configured to receive the plurality of longitudinal teeth of the belt.

[0019] The assembly, according to the invention, may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another: the assembly comprises a first pulley of given dimension and a second pulley of different dimension from the first pulley, - the assembly comprises a first pulley and a second pulley which are identical, - each circumferential row of teeth has tooth recesses having a depth P1 greater than a height H1 of the transverse teeth of the belt, - the longitudinal groove has a depth P2 greater than a height H2 of the longitudinal teeth of the belt, - each pulley is made of a material chosen from steel, aluminum or plastic.

[0020] The invention also relates to a method of manufacturing a synchronous transmission belt as described in the above, the method comprising the following steps: - forming a belt blank with belt materials around a cylindrical mandrel; removing the blank from the mandrel; - insert the blank inside a cylindrical mold comprising on an internal cylindrical wall, a pattern, negative of the transverse and longitudinal teeth to be formed on a belt; - press the blank against the mold using an inflatable rubber bladder, and heat the mold so as to vulcanize the belt blank; - demould the vulcanized blank; and - cut the vulcanized blank to form the belt. Brief description of the figures

[0021] The invention will be better understood with the aid of the following description, given solely by way of example and with reference to the appended drawings in which:

[0022] Figure 1 represents a schematic perspective and partial view of a belt according to the invention,

[0023] Figure 2 shows a schematic side view of the belt of Figure 1,

[0024] Figure 3 shows a schematic side view of another embodiment of a synchronous transmission belt according to the invention,

[0025] Figure 4 shows a schematic cross-sectional view of the belt of Figure 1,

[0026] Figure 5 shows a schematic cross-sectional view of another embodiment of the synchronous transmission belt according to the invention,

[0027] Figure 6 represents a schematic view of a step of a method of manufacturing a belt according to the invention, in particular the positioning of a belt blank in a mold,

[0028] Figure 7 shows a schematic longitudinal sectional view of a detail of the step of the method of Figure 6,

[0029] Figure 8 represents a schematic view of another step of the method of manufacturing a belt according to the invention, in particular the positioning of an inflatable bladder inside the blank,

[0030] Figure 9 represents a schematic longitudinal sectional view of a detail of the step of the method of Figure 8,

[0031] Figure 10 shows a schematic view of another step of the method of manufacturing a belt according to the invention, in particular the printing of the mold pattern on the blank,

[0032] Figure 11 shows a schematic longitudinal sectional view of a detail of the step of the method of Figure 10,

[0033] Figure 12 shows a schematic view of another step of the method of manufacturing a belt according to the invention, in particular the removal of the molded blank,

[0034] Figure 13 represents a schematic view of a tensile strength test of the belt according to the invention,

[0035] Figure 14 represents a schematic perspective view of an assembly according to the invention comprising at least one pulley and one synchronous transmission belt,

[0036] Figure 15 represents a schematic side view of the assembly of Figure 14, and

[0037] Figure 16 shows a schematic cross-sectional view of the assembly of Figure 14. Detailed description of the invention

[0038] We are interested in Figure 1 which shows a perspective view of an embodiment of a synchronous transmission belt 100 according to the invention.

[0039] The synchronous transmission belt 100 comprises an elastomer-based body 102 and a set of traction cables 110.

[0040] The elastomer-based body 102 comprises a dorsal portion 104. This elastomer-based body 102 also comprises a ventral portion 106, formed of a plurality of teeth 112, 112', 114, 114'. This plurality of teeth 112, 112', 114, 114' comprises on the one hand a plurality of transverse teeth 112, 112' and on the other hand a plurality of longitudinal teeth 114, 114'. The plurality of transverse teeth 112, 112' and the plurality of longitudinal teeth 114, 114' each comprise an external surface configured to cooperate, at least in part, with a tooth recess of a pulley.

[0041] Each transverse tooth 112, 112' further has, in section, a first profile 116 with two inclined flanks 117 converging towards each other in the direction of the top of the tooth, these two flanks 117 being, moreover, connected by at least one rounded part at the top.

[0042] By “rounded” we mean that the first profile 116 of the transverse teeth 112, 112' has a shape defining at least one curvature.

[0043] In one embodiment, illustrated in Figures 2 to 4, this first profile 116 may be trapezoidal with rounded corners.

[0044] By "trapezoidal" we mean that the first profile 116 of the transverse teeth 112, 112' has a trapezoidal shape, that is to say a deformed trapezium, or trapezoid. Thus, the top of each transverse tooth 112, 112' defines a top portion 116a, of non-zero dimension, parallel or not to an imaginary base 116b of the transverse tooth 112, 112' (represented by a broken line in FIG. 2), itself parallel to the dorsal portion 104 of the belt 100. In other words, the top of each transverse tooth 112, 112' defines a top portion 116a, of non-zero dimension, parallel or not to the dorsal portion 104 of the belt 100. It is then understood that the dorsal portion 104 of the belt 100 is substantially planar and that the top portion 116a is also substantially planar.

[0045] By “rounded angles” it is understood that the first profile 116 of the transverse teeth 112, 112' comprises, on the one hand, at least one angle describing a curvature in a convex manner at the level of the apex of the transverse tooth 112, 112', called the summit convex portion 116c, and / or, on the other hand, at least one angle describing a curvature in a concave manner at the level of the tooth hollow 120, called the concave portion 116d.

[0046] In other words, the first profile 116 of the transverse teeth 112, 112' advantageously comprises a substantially flat top portion 116a of tooth, at least one convex top portion 116c and at least one concave portion 116d of the bottom of the tooth hollow 120.

[0047] Typically, the top portion 116a of the transverse teeth 112, 112' may have a non-zero dimension of between 3 mm and 6 mm.

[0048] Typically, the top convex portion 116c is the result of a cubic spline of several points, or nodes, of the first profile 116. In this way, an equal convexity on either side of each point is defined. Furthermore, an approximate radius of curvature R1 can be determined for this top convex portion 116c.

[0049] Typically, the summit convex portion 116c has an approximate radius of curvature R1 which can be between 0.6 mm and 1.4 mm.

[0050] The concavity of the concave portion 116d is directly dependent on the spline obtained and described previously. In other words, the radius of curvature R2 of the concave portion 116d depends on this spline.

[0051] Typically, the radius of curvature R2 of the concave portion 116d may be between 0.6 mm and 1.4 mm.

[0052] Each transverse tooth 112, 112' having an axis of symmetry Y, it is understood that the first profile 116 of each transverse tooth 112, 112' comprises, when it is trapezoidal with rounded angles, two convex summit portions 116c, located on either side of the summit portion 116a, and two concave portions 116d, located on either side of the base 116b.

[0053] In a variant, the first profile 116 of each transverse tooth 112, 112' can be defined as being the component of a segment between two points, of a bitangent radius between this segment and the base 116b of the tooth, in other words a concave portion 116d, and of a spline tangent both to the segment and to a straight line tangent to the top of the transverse tooth 112, 112'.

[0054] This type of profile allows, in use, a higher torque transmission by the belt 100 but can lead to a reduction in the quality of the meshing. Furthermore, this also makes it possible to reduce the stress on the transverse tooth 112, 112' as well as its deformation.

[0055] Each longitudinal tooth 114, 114' of the plurality of longitudinal teeth 114, 114' further extends between two transverse teeth 112, 112', and this, substantially perpendicular to these transverse teeth 112, 112'. It is understood that the belt 100 therefore has crossed teeth. Furthermore, in the width of the belt 100, a single longitudinal tooth 114, 114' advantageously extends between two transverse teeth 112, 112'.

[0056] Each longitudinal tooth 114, 114' further has, in section, a second profile 118 with two inclined flanks 119 converging towards each other in the direction of the top of the tooth, these two flanks 119 being further connected by at least one rounded portion at the top. The flanks 119 may, taken together, have a generally V or U shape for example.

[0057] As previously, “rounded” means that the second profile 118 of the longitudinal teeth 114, 114' has a shape defining at least one curvature.

[0058] The second profile 118 of each longitudinal tooth 114, 114' may have a vertex defining a summit portion 118a, of zero dimension. In such a case, the vertex of the longitudinal tooth 114, 114' is convex and describes an arc of a circle.

[0059] In this case, the second profile 118 of the longitudinal teeth 114, 114' advantageously comprises at least one concave portion 118d of the bottom of the tooth hollow 120 and a convex tooth top 118c.

[0060] Typically, the concave portion 118d of the bottom of the tooth hollow 120 has a radius of curvature R2' of between 0.8 mm and 1.6 mm.

[0061] Typically, the 118c convex tooth apex has a radius of curvature R3 between 0.8 mm and 1.6 mm.

[0062] Each longitudinal tooth 114, 114' has an axis of symmetry. It is therefore understood that the second profile 118 of each longitudinal tooth 114, 114' comprises two concave portions 118d, located on either side of the base 118b and a convex tooth apex 118c.

[0063] Alternatively, not shown, the second profile 118 of each longitudinal tooth 114, 114' may be trapezoidal with rounded corners, i.e. substantially similar to the first profile 116, described previously. In such a case, the top of each longitudinal tooth 114, 114' defines a top portion 118a, of non-zero dimension, parallel or not to an imaginary base 118b of the longitudinal tooth 114, 114', itself parallel to the dorsal portion 104 of the belt 100. In other words, the top of each longitudinal tooth 114, 114' defines a top portion 118a, of non-zero dimension, parallel or not to the dorsal portion 104 of the belt 100. It is then understood that the dorsal portion 104 of the belt 100 is substantially planar and that the top portion 118a is also substantially planar.While the at least one curvature is defined, on the one hand, by at least one angle describing a curvature in a convex manner at the level of the apex of the longitudinal tooth 114, 114', and / or, on the other hand, at least one angle describing a curvature in a concave manner at the level of the tooth hollow 120. The second profile 118 of the longitudinal tooth 114, 114' having an axis of symmetry Y', it is understood that the second profile 118 of each longitudinal tooth 114, 114' comprises two convex summit portions, located on either side of the summit portion 118a, and two concave portions 118d, located on either side of the base 118b.

[0064] Furthermore, the inclined flanks 119 of each longitudinal tooth 114, 114', connected by the rounding, form, between them, an angle whose value is between 30° and 50°. Advantageously, the value of this angle is between 30° and 45°, and preferably between 35° and 45°.

[0065] Furthermore, the transverse teeth 112, 112' have a tooth height H1 and the longitudinal teeth 114, 114' have a tooth height H2. The tooth height H2, non-zero, of the longitudinal teeth 114, 114' is less than or equal to the tooth height H1 of the transverse teeth 112, 112'.

[0066] Advantageously, the tooth height H2, non-zero, of the longitudinal teeth 114, 114' is strictly less than the tooth height H1 of the transverse teeth 112, 112'.

[0067] A tooth height H2 of the longitudinal teeth 114, 114' lower than a tooth height H1 of the transverse teeth improves the flexural flexibility of the belt 100. Improved flexural flexibility facilitates the winding of the belt 100 on pulleys with a small diameter. This latter characteristic is, in particular, sought after for a bicycle application for example.

[0068] Typically, the tooth height H1 of the transverse teeth 112, 112' may be between 2.5 mm and 5 mm.

[0069] Typically, the tooth height H2 of the longitudinal teeth 114, 114', when strictly less than the tooth height H1 of the transverse teeth 112, 112', may be such that 0.4 x H1 < H2 < 1.0 x H1. Advantageously, the tooth height H2 is such that 0.4 x H1 < H2 < 0.9 x H1, still advantageously such that 0.4 x H1 < H2 < 0.8 x H1, and preferably such that 0.5 x H1 < H2 < 0.8 x H1.

[0070] It has also been observed that with a tooth height H2 greater than or equal to 0.4 x H1, good lateral guidance of the belt is ensured, while with a tooth height H2 less than or equal to 0.8 x H1, good winding of the belt on a pulley is ensured.

[0071] The transverse teeth 112, 112' serve, in use, for the transmission of torque, and this transmission of torque is all the higher due to the presence of inclined flanks 117 connected to each other by at least one rounded part. Furthermore, the longitudinal teeth 114, 114' also ensure the transmission of torque in addition to a self-centering function of the belt 100. Indeed, the angle formed by the flanks 119 introduced by the profile 118 of the longitudinal tooth 114, 114', as previously described, participate in the transmission of torque. In addition, the rounded shape of the profile 118 allows the belt 100, in the event of lateral displacement thereof, to self-center more quickly on the pulley on which it is intended to be mounted, improving its guidance. The presence of the longitudinal teeth 114, 114' also limits the deformation of the transverse teeth 112, 112'. This torque transmission and this guidance are both improved due to the fact that the tooth height H2 of the longitudinal tooth 114, 114' is less than or equal to the tooth height H1 of the transverse tooth 112, 112'. Indeed, in the case where a tooth height H2 would be greater than the tooth height H1, constraints may appear, with in particular a reduction in the flexibility of the belt 100 and a lack of suitability with the pulleys on which the belt 100 would be intended to cooperate.

[0072] The transverse teeth 112, 112' of the belt 100 may be distributed with a pitch of 8 mm, 11 mm or 14 mm. Advantageously, the transverse teeth 112, 112' of the belt 100 are distributed with a pitch of 11 mm.

[0073] The belt 100 also comprises a set of traction cords 110. The cords 110 are embedded in the body 102 between the dorsal portion 104 and the ventral portion 106 of the body 102. The cords 110 make it possible to increase the tensile modulus of the belt 100. They therefore extend along the length of the belt and are arranged next to each other across the width of the body 102. A cord 110 of the set of cords may in particular be made of a material chosen from aramid, polyester, glass fibers or carbon fibers, or a combination thereof. They therefore make it possible, for the application considered, to allow greater torque transmission while maintaining a very limited elongation of the belt 100.

[0074] The composition of each cord 110, the number of cords 110 arranged across the width of the belt 100 and the choice of material constituting them is variable and depends on the desired tensile modulus for the belt 100 to ensure torque transmission while limiting the elongation of the belt 100. The presence of such cords 110 has the general effect of enabling higher torque transmission.

[0075] Advantageously, the tensile modulus of the belt 100 is chosen between 10000 N / mm of belt width (Newton per millimeter of belt width) and 30000 N / mm of belt width, measured linearly between 0 and 1% elongation of the belt.

[0076] The synchronous transmission belt 100 may also comprise a coating 122 arranged at the external surface of the plurality of teeth 112, 112', 114, 114', as shown in FIGS. 3 and 5. The coating 122 is of particular interest for reinforcing the tooth root, i.e. the concave portions 116d, 118d of the transverse teeth 112, 112' and the longitudinal teeth 114, 114'.

[0077] The coating 122 may typically be made of a textile material selected, in a non-limiting manner, from a knit, a fabric or a non-woven fabric. In this case, the coating 122 may be made of a material typically selected from a polyamide (PA) or a polyamide-elastane blend.

[0078] Alternatively, the coating 122 may be an elastomeric thermoplastic film having a polymer matrix that is the combination of a thermoplastic matrix and an elastomeric matrix. The elastomeric portion of the elastomeric thermoplastic is advantageously an ethylene-alpha-olefin such as ethylene-propylene-monomer (EPM) or ethylene-propylene-diene monomer (EPDM). The thermoplastic matrix of the elastomeric thermoplastic is advantageously an olefinic thermoplastic, for example a low-density polyethylene.

[0079] This thermoplastic elastomeric film can have a thickness between 50 pm (micrometer) and 200 pm.

[0080] The elastomer-based body 102 of the belt 100 may be made of a material selected, without limitation, from an ethylene-alpha-olefin such as ethylene-propylene-monomer (EPM) or ethylene-propylene-diene monomer (EPDM), a hydrogenated butadiene-acrylonitrile copolymer (HNBR) or polyurethane (PU).

[0081] Example of embodiment of a synchronous transmission belt according to the invention

[0082] In the following, reference is made to Figures 2 to 5 which show a particular embodiment of the belt 100.

[0083] The elastomer-based body 102 is made of peroxide-vulcanized ethylene-propylene-diene monomer (EPDM) with, in this example, a hardness of 85 Shore A.

[0084] In this exemplary embodiment, the belt 100 has a geometry defined as follows and illustrated by figures 2 and 4. The body 102 has a thickness T of 6.5 mm, taken from the dorsal portion 104 to the top of the transverse teeth 112, 112', and a width of 12 mm.

[0085] Each transverse tooth 112, 112' has a height H1 of 5 mm. Furthermore, in this exemplary embodiment, the first profile 116 of each transverse tooth 112, 112' is trapezoidal with rounded corners. This first profile 116 has a top portion 116a of 2 mm and a convex top portion 116c whose approximate radius of curvature R1 is 1.2 mm.

[0086] Each longitudinal tooth 114, 114' has a height H2 of 2.2 mm. Furthermore, the second rounded profile 118 of each longitudinal tooth 114, 114' has a concave portion 118d of the bottom of the tooth hollow 120 with a radius of curvature R2' of 1.2 mm and a convex tooth apex 118c with a radius of curvature R3 of 1.6 mm. Furthermore, the inclined flanks 119 connected by at least one rounded portion of the second profile 118 of each longitudinal tooth 112, 112' form, between them, an angle of 40°.

[0087] The set of cords 110 embedded in the body 102 comprises 13 cords 110. The cords 110 have a diameter d of 0.8 mm and their centers are separated laterally by a pitch p of 0.92 mm. The center of each cord 110 is furthermore located at a distance of approximately 0.7 mm from the dorsal portion 104 of the belt 100.

[0088] Each 110 cord is made of aramid, and in particular a 1100x1x4 aramid, that is to say that each thread has a count of 1100 dtex (decitex), or 1100x10 7 kg / m (kilogram per meter), and that each wire is first twisted individually before being twisted by four. Each 110 cable also has a Young's modulus of 30,000 MPa (MegaPascal), or 30,000 N / mm 2 (Newton per square millimeter).

[0089] The tensile modulus of the belt can thus be calculated and is expressed as the multiplication of the Young's modulus of the cord 110 with the cross-sectional area of ​​the cord 110. In the exemplary embodiment, the belt 100 has 13 cords 110, the diameter d of each cord 110 of which is 0.8 mm, i.e. a total cross-sectional area of ​​approximately 6.53 mm 2 This set of cables 110 thus makes it possible to define the traction module of the belt 100 at a value of approximately 195900 N.

[0090] In this exemplary embodiment, the transmission belt 100 comprises a coating 122, visible in FIGS. 3 and 5. This coating 122 is a polyamide knit, in particular a polyamide 66 with a weight of 150 g / m 2 (gram per square meter).

[0091] In this embodiment, the transverse teeth 112, 112' of the belt 100 are distributed with a pitch of 11 mm. This pitch also has the advantage of allowing optimized torque transmission and space requirements. Indeed, with a lower pitch, the torque transmission is less, while with a higher pitch, the space requirements due to the size of the teeth increase.

[0092] Reference is now made to Figures 6 to 12 which illustrate steps of manufacturing a belt 100 according to the aforementioned embodiment.

[0093] The method of manufacturing a belt 100 according to the invention consists of: - forming a belt blank 10 with belt materials around a cylindrical mandrel; - remove the blank from the mandrel; - inserting the blank 10 inside a cylindrical mold 12 comprising, on an internal cylindrical wall, a negative pattern of the transverse teeth 112, 112' and longitudinal teeth 114, 114' to be formed on the belt 100, - pressing the blank 10 against the mold 12 by means of an inflatable rubber bladder 14, and heating the mold 12 so as to vulcanize the belt blank 10; - demould the vulcanized blank; and - cutting the vulcanized blank 10 so as to form the synchronous transmission belt 100.

[0094] First, the belt materials that form the blank 10 are placed on a cylindrical mandrel (not shown). These belt materials include the back portion 104 (in the raw state) of the belt body 102, the cords 110 and the ventral portion 106 (in the raw state) of the belt body 102. These belt materials may also include the coating 122, placed on the ventral portion 106 of the belt body 102. In Figures 6 and 7, the blank 10 has been removed from the cylindrical mandrel and is already inserted inside the cylindrical mold 12 which has on its internal cylindrical wall at least one pattern, negative of the profile of the transverse teeth 112, 112' and the longitudinal teeth 114, 114' to be formed on a belt. It is understood that the ventral portion 106 (in the raw state) is positioned in contact with the mold 12.

[0095] In Figures 8 and 9, the inflatable bladder 14 is placed inside the blank 10.

[0096] In Figures 10 and 11, the inflatable bladder 14 is inflated, with a pressure of 20 bars, so as to press the dorsal portion 104 (in the raw state) of the blank 10 against the mold 12 (see arrow E in Figure 11). In this way, the internal wall of the mold 12 with at least one pattern, negative of the teeth 112, 112', 114, 114' to be formed on a belt, forms a corresponding pattern on the external surface of the ventral portion 106 of the blank 10. At the same time, the mold 12 is heated to 182°C to ensure vulcanization of the dorsal 104 and ventral 106 portions intended for form the body 102 in vulcanized elastomer. It is understood that the pattern of the mold 12 is printed on the blank 10 during this step.

[0097] The blank 10, which is now vulcanized, is then demolded, as illustrated in Figure 12, before being cut to the desired width to obtain a belt 100 according to the invention.

[0098] In the following, the tensile strength of the synchronous transmission belt 100 thus produced was tested. The test carried out complies with various standards, including ISO 4210-8 and the French and European standard NF EN 15194.

[0099] These standards describe the tensile strength test illustrated in Figure 13. In this test, the belt 100 according to the invention is mounted on two similar or identical drive pulleys P, P'. At least one of the two pulleys P, P' is free to rotate. During the test, the tensile load is gradually increased until the tensile force exerted on the belt 100 reaches 4000 N. For the force exerted on the belt 100 to reach 4000 N, a tensile load F of 8000 N is required.

[0100] When this threshold is reached, the 100 belt shows no cracks, breaks or delamination, in accordance with the recommendations of the standards.

[0101] End of example.

[0102] With reference to Figures 14 to 16, the invention also relates to an assembly 300 comprising a synchronous transmission belt 100 as described above and at least one pulley 200.

[0103] From a practical point of view, the 300 set can be presented advantageously in the form of a kit or already assembled.

[0104] Preferably, the belt 100 is intended to be mounted, in use, on two pulleys 200, i.e. a first pulley and a second pulley. Each of the pulleys 200 comprises, on the one hand, two circumferential rows of teeth 210, 210' parallel to each other and configured to receive the tooth recesses 122 of the plurality of transverse teeth 112, 112' of the belt 100 and comprises, on the other hand, a circumferential groove 220, separating the two circumferential rows of teeth 210, 210', configured to receive the plurality of longitudinal teeth 114, 114' of the belt 100.

[0105] Advantageously, the assembly 300 comprises a first pulley of given dimension and a second pulley of different dimension from the first pulley (not shown). By different dimension is meant a second pulley whose diameter is greater or less than the diameter of the first pulley.

[0106] Advantageously, the assembly 300 comprises a first pulley and a second pulley which are identical. Identical means two pulleys which have the same dimensions, for example the same diameter and rows of teeth 210, 210' with the same geometries.

[0107] Each pulley 200 may be made of a material selected, but not limited to, from steel, aluminum, or plastic. Each of these materials has properties in terms of mechanical strength, density, or cost that can be adapted to predefined applications.

[0108] Each circumferential row of teeth 210, 210' further comprises tooth recesses 212 having a depth P1. Advantageously, this depth P1 is greater than the height H1 of the transverse teeth 112, 112' of the belt 100.

[0109] The circumferential groove 220 of each pulley 200 also has a depth P2. Advantageously, this depth P2 is greater than the height H2 of the longitudinal teeth 144.

[0110] The teeth of each of the circumferential rows of teeth 210, 210' can be distributed with a pitch of 8 mm, 11 mm or 14 mm.

[0111] It is therefore understood that there is a clearance 230 between the top of each tooth 112, 112', 114, 114' and, on the one hand, the tooth hollow 210 of the pulleys 200 and, on the other hand, the bottom of the groove 220. This clearance 230 has the advantage of being a means of evacuating foreign bodies, such as mud, water or stones, which could, during operation, become inserted into the assembly 300, and more particularly between a pulley 200 and the belt 100. These foreign bodies being evacuated more easily, the risks of wear of the belt 100 are reduced.

[0112] In light of what has been described in the foregoing, it is clear that the belt according to the invention allows an improvement in the torque transmissible by the belt and its stability. Indeed, in use, the contact surface between the transverse and longitudinal teeth of the belt and the teeth of the pulley is high thanks to the shapes of the teeth of the belt. This high contact surface and the The presence of cables improving the belt's traction modulus, the transmissible torque can be controlled as well as the levels of belt deformation, which reduces belt wear over time, and therefore improves its lifespan. In addition, the longitudinal teeth allow the belt to be guided on the pulley and thus prevent lateral movement of the latter.

[0113] Another advantage is that when the belt is mounted on a pulley of the assembly according to the invention, it allows the removal of external elements which may become inserted into the hollows of the teeth of the pulley, such as for example water, earth, mud or even stones.

Claims

Claims [1] Synchronous transmission belt (100) comprising an elastomer-based body (102) comprising a dorsal portion (104), a ventral portion (106) and a set of traction cords (110) between the dorsal portion (104) and the ventral portion (106), the ventral portion (106) having, on the one hand, a plurality of transverse teeth (112, 112'), each transverse tooth (112, 112') having in section a first profile (116) with two inclined flanks (117) converging towards each other in the direction of a peak of the transverse tooth (112, 112'), said flanks (117) of the transverse tooth being connected by at least one rounded portion, each transverse tooth having a tooth height H1, and, on the other hand, a plurality of longitudinal teeth (114, 114'), each longitudinal tooth (114, 114') extending between two transverse teeth (112,112') substantially perpendicular to said transverse teeth and having in section a second profile (118) with two inclined flanks (119), converging towards each other in the direction of a summit of the longitudinal tooth (114, 114'), said flanks (119) of the longitudinal tooth being connected by at least one rounded part, each longitudinal tooth having a tooth height H2, said tooth height H2, non-zero, being less than or equal to the tooth height H1., [2] Belt (100) according to claim 1, wherein the tooth height H2 of each longitudinal tooth (114, 114') is such that 0.4 x H1 < H2 < 0.8 x H1. [3] Belt (100) according to any one of claims 1 or 2, in which each transverse tooth (112, 112') has in section a first trapezoidal profile (116) with rounded angles. [4] Belt (100) according to claim 3, wherein said first profile (116) of each transverse tooth (112, 112') comprises two convex top portions (116c), said convex top portions being located on either side of a top portion (116a), and two concave portions (116d), said concave portions being located on either side of a base (116b) of the transverse tooth. [5] Belt (100) according to claim 4, in which each convex top portion (116c) of said first profile (116) has an approximate radius of curvature (R1) between 0.6 mm and 1.4 mm, and each concave portion (116d) has a radius of curvature (R2) between 0.6 mm and 1.4 mm. [6] Belt (100) according to any one of claims 1 to 5, wherein said second profile (118) of each longitudinal tooth (114, 114') comprises two concave portions (118d), said concave portions being located on either side of a base (118b) of said longitudinal tooth, and a tooth apex (118c), said apex (118c) being convex. [7] Belt (100) according to claim 6, wherein each concave portion (118d) of said second profile (118) has a radius of curvature (R2') of between 0.8 mm and 1.6 mm, and said vertex (118c) of the second profile has a radius of curvature (R3) of between 0.8 mm and 1.6 mm. [8] Belt (100) according to any one of claims 1 to 7, wherein said second profile (118) of each longitudinal tooth (114, 114') is a trapezoidal profile with rounded corners. [9] A belt (100) according to any one of claims 1 to 8, comprising a coating (120) arranged at an outer surface of the plurality of transverse (112, 112') and longitudinal (114, 114') teeth. [10] The belt (100) of claim 9, wherein the elastomer-based belt (100) body (102) is made of a material selected from an ethylene-alpha-olefin or a polyurethane, and the coating (120) is a textile material or an elastomeric thermoplastic film. [11] A belt (100) according to any one of claims 1 to 10, wherein each cord (110) of the set of tensile cords is made of aramid, polyester, glass fibers or carbon fibers or a combination thereof. [12] Assembly (300) comprising at least one pulley (200) and a synchronous transmission belt (100) according to any one of claims 1 to 11, each pulley comprising: two circumferential rows of teeth (210, 210') parallel to each other and configured to receive the tooth recesses (122) of the plurality of transverse teeth (112, 112') of the belt (100), and a circumferential groove (220), separating the two circumferential rows of teeth, configured to receive the plurality of longitudinal teeth (114, 114') of the belt (100). [13] An assembly (300) according to claim 12, wherein each circumferential row of teeth (210, 210') comprises tooth recesses (212) having a depth P1 greater than a height H1 of the transverse teeth (112, 112') of the belt (100). [14] Assembly (300) according to any one of claims 12 or 13, wherein the longitudinal groove (220) has a depth P2 greater than a height H2 of the longitudinal teeth (114, 114') of the belt (100). [15] A method of manufacturing a belt (100) according to any one of claims 1 to 14, said method comprising the following steps: forming a belt blank (10) with belt materials around a cylindrical mandrel; removing the blank from the mandrel; inserting the blank (10) inside a cylindrical mold (12) having, on an internal cylindrical wall, a negative pattern of the transverse and longitudinal teeth to be formed on a belt; pressing said blank (10) against said mold (12) by means of an inflatable rubber bladder (14), and heating said mold so as to vulcanize the belt blank; demolding the vulcanized blank; and cutting the vulcanized blank so as to form the belt.

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