Drive belt for a roller conveyor having rollers with concave grooves and associated conveyor

Abstract

A transmission belt (100) for a roller conveyor having rollers, made of steel or plastic and having concave grooves, the belt comprising: - an elastomeric body (102) comprising a back portion (104) and a belly portion (106) formed by a single tooth, the outer surface of the elastomeric body having a convex shape configured to engage with the concave grooves of the rollers; - a set of tension cords (110) embedded in the body (102) between the back portion (104) and the belly portion (106) of the body; - a coating (112) disposed on the outer surface of the tooth, having the shape of the outer surface of the tooth and defining a coefficient of friction with the concave grooves of the rollers that is non-zero and less than or equal to 0.8.

Description

Technical Field

[0001] The present invention relates to a transmission belt for a roller conveyor having rollers with concave grooves. The present invention also relates to a concave groove roller conveyor provided with such a belt.

Background Art

[0002] Roller conveyors are widely used in the transportation and logistics sectors to route and sort all kinds of objects, especially packages. Generally speaking, these conveyors comprise a plurality of rollers driven in rotation by a drive element via a transmission element. There are various types of rollers and just as many transmission elements, each having its own specific requirements. In particular, roller conveyors having rollers with circular concave grooves are extremely common. These are shown, for example, in FIGS. 1 to 4.

[0003] FIGS. 1 and 2 show a conventional configuration of a circular groove roller conveyor, namely a straight conveyor 1a as shown in FIG. 1 and a curved portion of a conveyor 1b as shown in FIG. 2.

[0004] Normally, each of the rollers 10 of the conveyors 1a, 1b comprises a groove 12 with a circular groove bottom 14 at at least one of its longitudinal ends. A circular belt 2, namely a circular belt 2 with a disc-shaped cross-section, is engaged in these grooves 12 to drive the rollers 10. These belts are usually made of polyurethane, are inexpensive and are easy to fit into the grooves.

[0005] During operation, the drive roller drives in rotation an adjacent roller 10 known as a slave roller by means of the belt 2. This drive roller is similar to the slave roller except that it comprises a motor that can switch itself on. The drive roller then drives in rotation the first slave roller by means of the first belt 2, and the first roller itself may drive in rotation the second slave roller by means of a second belt or the like.

[0006] In order to maximize the torque transmission between the two rollers, the belt 2 must be placed on the bottom 14 of the groove 12 with the largest possible contact surface while avoiding contact with the side surface 16 of the groove 12 as much as possible. Contact with the side surface of the groove results in several detrimental effects. First, since there are two contact surfaces between the belt and the groove located at relatively different distances from the axis of rotation of the roller, the belt is subjected to two very different speeds. This increases the deformation and wear of the belt. Second, the belt is prone to turning inside out. These detrimental situations are particularly common in the curved sections of the conveyor because the curvature promotes contact between the belt and one side surface of the groove.

[0007] Document US - A1 - 2009 / 107809 describes a typical example of a roller conveyor.

[0008] Next, it is necessary to distinguish between different types of roller conveyors.

[0009] Figure 3 shows a first type of roller 10 made of steel, with a groove 12 formed directly at one end of the roller 10. These grooves may be, for example, pressed into the roller. In this case, there is a region Z1 for the passage of the package that extends over the entire length of the roller 10, and thus surrounds the transmission region Z2 where the groove 12 and the circular belt 2 are located. In this configuration, a passage region Z1 that is as wide as possible is possible, but problems may occur when the package comes into contact with one of the belts 2. When an impact occurs between the belt 2 and the package, the belt 2 may come out of the groove 12 of the roller 10, which may cause the conveyor to stop.

[0010] To prevent this, the diameter of the cross - section of the circular belt 2 is selected to be strictly smaller than the depth of the groove 12. For example, for a groove depth of 10 mm (millimeters), the diameter of the belt cross - section is 6 mm.

[0011] However, this limits the contact surface between the belt 2 and the bottom 14 of the groove 12, and thus the torque that can be transmitted by the belt between the two rollers.

[0012] Alternatively, as shown in FIG. 4, there is a roller provided with a drive head 18 attached to one end of the roller 10. The drive head 18, which is usually made of plastic, has the advantage of having a transmission region Z2 close to the end of the roller 10 and the side profile of the conveyors 1a, 1b. In this way, the region Z2 of the belt is separated from the region Z1 through which the package being conveyed passes over the roller, and thus it is possible to limit or even prevent the contact of the package with the belt 2. However, for the same conveyor width, the roller of FIG. 4 can drive a smaller package than the roller of FIG. 3.

[0013] In practice, current circular belts have relatively poor torque transmission and insufficient service life, especially in the curved portions of conveyors where they are likely to turn inside out easily, resulting in accelerated wear or even breakage, especially at the level of belt welding.

[0014] The documents of U.S. Patent Application Publication No. 2002 / 03997, U.S. Patent Application Publication No. 2014 / 323257, Japanese Unexamined Patent Publication No. 53 - 37266, European Patent Application Publication No. 3045771 or British Patent Application Publication No. 697901 show other types of belts that can be used in roller grooves.

[0015] Another object of the present invention is to propose a transmission belt for a roller conveyor with concave grooves that does not have at least one of the above - mentioned drawbacks.

[0016] Another object of the present invention is to provide a transmission belt for a roller conveyor having rollers with concave grooves that provides improved performance with respect to the torque that can be transmitted between two rollers.

[0017] Another object of the present invention is to propose a transmission belt for a roller conveyor having rollers with concave grooves, which in particular also limits the risk of the belt turning inside out at the curved sections of the conveyor. SUMMARY OF THE INVENTION

[0018] Accordingly, a transmission belt for a roller conveyor having rollers with concave grooves made of steel or plastic is proposed, the belt comprising: - an elastomeric body comprising a back part and a belly part formed by a single tooth, the outer surface of the elastomeric body having a convex shape configured to cooperate with the concave grooves of the rollers; - a set of tension cords embedded in the body between the back and belly parts of the body; - a coating disposed on the outer surface of the tooth, the shape of the outer surface of the tooth defining a coefficient of friction with the concave grooves of the rollers that is non-zero and less than or equal to 0.8.

[0019] Thus, the present invention ensures an improvement in the torque transmissible by the belt and its stability. In fact, in use, the contact surface between the belt and the bottom of the grooves of the rollers is wide thanks to the convex shape of the teeth of the belt that conforms to the concave shape of the grooves. In addition, the combination of this convex shape of the teeth and the coating disposed on the outer surface of the teeth means that the coefficient of friction of the belt in the grooves can be set to a controlled value. Thanks to the controlled coefficient of friction and the presence of cords that improve the tensile modulus of the belt, the transmitted torque can be maintained under control. This also reduces in particular the risk of the belt turning inside out when the belt rides up on the sides of the grooves, especially at the curved sections of the conveyor.

[0020] The belt according to the present invention may include one or more of the following features, either separately or in combination with each other: - a coefficient of friction of 0.3 or more; - the set of tension cords defines a tensile modulus of the belt between 500 N and 1500 N, preferably between 800 N and 1500 N, and more preferably between 800 N and 1200 N; - The codes of the set of codes are made of a polyamide-based or polyester-based material, - The coating partially embedded in the teeth is selected from a knitted fabric, a woven fabric, a non-woven fabric, or a set of fibers, - The coating is made of a material selected from polyamide, polyester, cellulose fibers such as cotton, a mixture of cellulose fibers and polyurethane, or a combination thereof, - The body is made of a material selected from ethylene-propylene-diene monomer, ethylene-propylene copolymer, polybutadiene, polyurethane, or natural rubber, - The body is made of a material selected from ethylene-propylene-diene monomer or ethylene-propylene copolymer, and the coating is a film of at least partially cross-linked thermoplastic material containing at least 30% polyethylene, and the thermoplastic film covers the outer surface of the teeth, - The film contains particles and / or fibers of graphite, molybdenum disulfide, and / or polytetrafluoroethylene.

[0021] The present invention also relates to a conveyor comprising a plurality of rollers with concave grooves made of steel or plastic rollers, and the rollers are connected to each other in pairs by a belt as described above so that the coating of the belt contacts the concave grooves of the rollers.

[0022] The conveyor according to the present invention may include one or more of the following features, separately or in combination with each other: - The belt has a height that is strictly lower than the depth of the groove that receives the belt, - The concave grooves of the rollers are made of a plastic material selected from polyamide, polypropylene, or a composite material based on fibers embedded in a thermoplastic or thermosetting resin, - The belt is installed between the rollers with a laying tension between 60 N / strand and 100 N / strand.

Brief Description of the Drawings

[0023] The present invention will be preferably understood with reference to the following description given by way of example only and with reference to the accompanying drawings.

[0024]

Figure 1

[0025]

Figure 2

[0026]

Figure 3

[0027]

Figure 4

[0028]

Figure 5

[0029]

Figure 6

[0030]

Figure 7

[0031]

Figure 8

[0032]

Figure 9

[0033]

Figure 10

[0034]

Figure 11

[0035]

Figure 12

[0036]

Figure 13

[0037]

Figure 14

[0038]

Figure 15

[0039]

Figure 16

BEST MODE FOR CARRYING OUT THE INVENTION

[0040] Detailed Description of the Invention Hereinafter, for the purpose of explaining the prior art, reference is made to a transmission belt for a roller conveyor having a roller with a concave groove as described above and shown in FIGS. 1 to 4.

[0041] Figures 5 and 6 respectively show a cross-sectional view, a perspective view, and a partial cross-sectional view of a transmission belt 100 for conveyors 1a and 1b having rollers 10 with concave grooves 12. The "concave groove" means any groove having a substantially concave cross-section, for example, a circular groove (i.e., one having a groove bottom in the shape of an arc of a circle, or a groove having an elliptical or oval bottom).

[0042] The belt 100 includes an elastomeric body 102 and a set of tension cords 110 and a coating 112.

[0043] The elastomeric body 102 includes a back portion 104.

[0044] The elastomeric body 102 also includes a belly portion 106 formed by a single tooth, the outer convex surface of which is configured to cooperate with the concave grooves 12 of the roller conveyors 1a, 1b, and 10. The outer convex surface of the tooth may be, for example, arcuate, elliptical, or oval, depending particularly on the shape of the concave surface forming the groove. Advantageously, the outer surface of the tooth of the belly portion 106 forms an arc when the groove of the roller is circular.

[0045] Furthermore, this convex outer surface serves to define the coefficient of friction (COF) between the belt 100 and the groove 12 of the roller 10, such that the belt 100 is configured to be installed. In practice, the higher the coefficient of friction, the greater the torque that can be transmitted. However, the higher the coefficient of friction, the higher the risk that the belt 100 will turn inside out, particularly at the curved portions of the conveyor. Conversely, the lower the coefficient of friction, the less torque is transmitted, and thus the torque that can be transmitted from any one roller to another is limited.

[0046] The control of this parameter will be described later.

[0047] In addition, the back portion 104 and the belly portion 106 of the body 102 need not be connected by the side portion 108, but may be connected.

[0048] The belt 100 also comprises a set of tension cords 110. The cords 110 are embedded in the body 102 between the back portion 104 and the belly portion 106 of the body 102. The cords 110 increase the tensile modulus of the belt 100. Thus, they extend along the length of the belt and are arranged adjacent to each other across the width of the body 102. The cords 110 of the set of cords are made of a material selected in particular from polyamide (PA) or polyester. Thus, in the application in question, it is possible to achieve high torque transmission while maintaining a very limited elongation of the belt 100.

[0049] The structure of each cord 110, the number of cords 110 arranged across the width of the belt 100, and the choice of the material constituting them can be varied and depend on the tensile modulus required for the belt 100 in order to ensure torque transmission while limiting the elongation of the belt 100. The general effect of the presence of such cords 110 is to enable high torque transmission, especially as compared with known circular belts (generally made of polyurethane) without cords for this type of conveying application.

[0050] Advantageously, the tensile modulus of the belt is selected between 500 N (Newton) and 1500 N. More advantageously, the tensile modulus is between 800 N and 1500 N, preferably between 800 N and 1200 N.

[0051] The belt 100 also comprises a coating 112 arranged on the outer surface of the teeth. This coating 112 contributes, together with the shape of the teeth, to defining the coefficient of friction (COF) between the belt 100 and the steel roller 10 or the plastic drive head 18 of the roller 10.

[0052] The coating 112 can usually be selected from knitted fabric, woven fabric, non-woven fabric, or an assembly of fibers.

[0053] In this case, the elastomeric body 102 of the belt may be made of a material selected from ethylene-propylene-diene monomer (EPDM), ethylene-propylene copolymer (EPM), polybutadiene (BR), polyurethane (PU), or natural rubber, but is not limited thereto.

[0054]

[0055] In this case, the coating 112 may be made of a material usually selected from polyamide, polyester, cellulose fiber, particularly cotton, a mixture of cellulose fiber and polyurethane, particularly a mixture of cotton and polyurethane, or a combination thereof.

[0056] In particular, the coating 112 may be a polyamide knit or a cotton fabric mixed with polyurethane.

[0057] Also in this case, a part of the coating 112 is embedded in the teeth.

[0058] In this case, the coefficient of friction is related to various parameters such as the type of the coating 112 such as knitted fabric or woven fabric, the nature of its material, such as polyamide, its basis weight, or its penetration rate τ into the flank portion 106 at the level of the outer surface of the teeth. This also depends on the nature of the elastomer and its characteristics.

[0059] The coefficient of friction between the elastomer and steel or plastic is particularly high and usually exceeds 1.5. The above-mentioned parameters for characterizing the coating 112 can, depending on the choices made, reduce the coefficient of friction (compared to the same surface without the coating 112) and thus make it possible to control it. Given a number of parameters, there are many ways to define the coefficient of friction. From a practical point of view, first, the type of the coating 112 (mesh, woven fabric, etc.) is selected, then the material forming it (polyamide, polyester, etc.), its grammage (the higher the grammage, the more the coating 112 covers the outer surface and vice versa), and finally the penetration rate into the teeth may be selected. This penetration rate τ is defined as the ratio of the total thickness of the coating 112 embedded in the teeth of the elastomer-based body 102. Locally, this penetration rate τ can vary from one point to another on the belt 100, so the average penetration rate τ is considered over the entire belt 100. In practice, the penetration rate τ is not zero and strictly less than 100%, and its exact value depends on other parameters. The selection of these parameters also depends on the nature of the elastomer used.

[0060] Hereinafter, specific examples of embodiments will be shown.

[0061] FIG. 7 is merely intended to illustrate this concept of the penetration rate τ of the coating 112 from the outer surface of these teeth into the teeth, where the coating 112 is considered to be a mesh. Thus, on the left side of this FIG. 7, the penetration rate τ is 0 (0%), and a part of the mesh 112 does not penetrate the body 102. In contrast, on the right side of FIG. 7, the penetration rate τ is 100%, and the mesh 112 is completely embedded in the body 102 (right). Finally, in the center of FIG. 7, various situations representing a penetration rate τ of 9, which is not zero and strictly less than 100%, are shown.

[0062] Alternatively, the coating 112 may be a film of a partially crosslinked thermoplastic material containing at least 30% polyethylene (PE: polyethylene), and this film covers the outer surface of the teeth. It is understood that the thermoplastic film does not penetrate the teeth.

[0063] In such a case, the body 102 of the belt 100 is preferably based on an ethylene alpha olefin elastomer, in particular EPDM or EPM.

[0064] The thermoplastic film may contain between 30% and 90% polyethylene, preferably between 50% and 90% polyethylene, more preferably between 75% and 90% polyethylene.

[0065] The polyethylene in the film crosslinks with an elastomer, such as EPDM or EPM, in the presence of a peroxide or another crosslinking agent. This helps the adhesion of the film to the elastomer.

[0066] The thermoplastic film may be composed of a blend of polyolefins containing a homopolymer or copolymer containing ethylene. Ethylene copolymers include ethylene / alpha-olefin copolymers, ethylene / unsaturated ester copolymers, ethylene / acrylate / acrylic acid copolymers, ethylene / methacrylic acid copolymers, polyethylene-ethylene octene copolymers, etc. The thermoplastic film may also be based on low density polyethylene.

[0067] The thermoplastic film may have a thickness between 10 μm (micrometers) and 500 μm, more specifically between 50 μm and 200 μm.

[0068] Advantageously, the thermoplastic film also contains particles and / or fibers of graphite, molybdenum disulfide and / or polytetrafluoroethylene (PTFE). In particular, this affects the coefficient of friction.

[0069] The particles may have a particle size between 15 μm and 200 μm, preferably between 30 μm and 100 μm, more specifically between 30 μm and 90 μm.

[0070] The type of film described above for coating 112 is already known to those skilled in the art per se, and thus its manufacture is not difficult. However, it is not used for the applications under consideration here.

[0071] Examples of embodiments of the belt according to the present invention

[0072] Referring to FIGS. 5 and 8, an example of an embodiment of a method in which belt 100 can be used is shown below.

[0073] The elastomeric body 102 is made of peroxide-cured EPDM having a hardness between 75 and 85 Shore A due to the presence of peroxide in ethylene propylene diene monomer (EPDM) that affects the coefficient of friction. This EPDM is selected with a Mooney point of 100 and a viscosity of ML(1+4) at 100 °C. This viscosity is determined according to the ISO 289-1 standard that defines the test temperature (100 °C), the sample preheating time (1 minute) before starting shear, and the shear time (4 minutes).

[0074] In this example of the embodiment, the geometric shape, as defined below and shown in FIG. 8, is possessed by belt 100. The body 102 has a thickness, i.e., height H, of 2.3 mm and a width L of 6 mm. A single convex tooth of the body 102 has the shape of an arc of a circle with a diameter D of 10 mm.

[0075] The set of cords 110 embedded in the body 102 comprises nine cords 110. The cords 110 have a diameter d of 0.6 mm, and their centers are laterally separated by a pitch p of 0.7 mm. Also, the center of each cord 110 is located at a distance h of 0.7 mm from the back 104 of the belt 100.

[0076] Each cord 110 is made of polyamide (PA), in particular, 940×1×2 polyamide 6-6 (PA66), i.e., each thread is 940 dtex (decitex), i.e., 940×10 -7has a linear mass density of kg / m (kilogram / meter), and each thread is first twisted individually and then with the other. Each cord 110 also has a Young's modulus of 400 MPa (megapascal), or 400 N / mm 2 (Newton per square millimeter).

[0077] Therefore, the tensile modulus of the belt may be calculated and expressed as the product of the Young's modulus of the cord 110 and the cross-sectional area of the cord 110. In this example of the embodiment, the belt has nine cords 110 each having a diameter d of 0.6 mm, giving a total cross-sectional area of 2.54 mm 2 . Therefore, the tensile modulus of the belt is about 1000 N. In other words, the set of cords 110 defines the tensile modulus of the belt 100.

[0078] The coating 112 is a polyamide (PA) jersey knit with a tubular finish and a basis weight of 60 g / m 2 (gram per square meter), particularly polyamide 6-6 (PA66). FIG. 9 shows a photograph of a cross-section of an example of an embodiment of the belt 100. In FIG. 9, the penetration rate τ may be qualitatively estimated by measuring the ratio f2 of the knitted fabric within the teeth to the thickness f1 of the knitted fabric. In this example, the penetration rate τ of the new knitted fabric into the teeth at the level of the outer surface of the knitted fabric is about 50%.

[0079] As described above, the basis weight selected in this example of the embodiment is 60 g / m 2 . However, the inventors believe that a low basic basis weight can be used to achieve similar properties. This basis weight may be at least 20 g / m 2 , preferably at least 30 g / m 2 , more preferably at least 40 g / m 2 .

[0080] Now, refer to FIGS. 10 to 12 showing the steps in the manufacture of the belt 100 according to the foregoing embodiment. FIGS. 10 to 12 show half views in the longitudinal cross-section.

[0081] The method of manufacturing the belt is well known in the prior art. Usually, this involves placing the belt material forming the assembly 200 around the mandrel 202, and then placing this mandrel 202 together with the assembly 200 into the mold 204, and then the mold 204 is pressed against the assembly 200 to take the desired shape. Then, the assembly 200 can be cut to the desired width to obtain the belt 100.

[0082] Figure 10 shows a case where the belt material forming the assembly 200 includes the (raw state) back 104 of the belt body 102, the cord 110, and the (raw state) belly portion of the belt body 102. On the right side of Figure 10, the assembly 200 is already placed on the mandrel 202. On the left side of Figure 10, there is a sleeve 206 of the braid 112.

[0083] The sleeve 206 of the braid 112 is arranged around the mandrel 202 so as to cover the outer surface of the assembly 200 and is stretched by about 20% in the direction defined by the circumference of the mandrel 202, as shown in Figure 11.

[0084] Figure 12 shows the mandrel 202 with the assembly 200 and the braided sleeve 206 112 arranged around it when introduced into the mold 204 having at least one concave pattern on its inner wall 208.

[0085] The mold 204 is pressed against the assembly 200 and the sleeve 206 of the braid 112 with a pressure of 7 bar, whereby the inner wall 208 of the mold 204 having at least one concave pattern forms a corresponding convex pattern on the outer surface of the assembly 200 together with the braid 112. Also, due to the pressure of the mold 204, the braid 112 can penetrate through the outer surface of the formed teeth. At the same time, the mandrel 202 is heated to 170 °C to vulcanize the back portion 104 and the belly portion 106 configured to form the vulcanized elastomer body 102. It is understood that the concave pattern of the mold 204 is printed on the assembly 200 using the braid 112.

[0086] In order to characterize the belt 100 manufactured in this way, various tests were carried out. In some cases, the characteristics of a belt of the prior art, i.e., a polyurethane (PU)-based circular belt having a circular cross-section, a diameter of 6 mm, and a tensile modulus of 250 N, rather than cords or any other form of reinforcement, were compared with the obtained results.

[0087] Test: Determination of the coefficient of friction of the belt of an example embodiment on a steel pulley

[0088] The coefficient of friction of the belt was determined using the experimental apparatus shown in FIG. 12. For this test, a belt 100 in the form of a single strand (not welded so as to be closed on its own) is placed on a pulley P. The pulley P is selected to represent a steel roller with a circular groove. One end of the belt strand 100 is attached to a mass M that generates a force F of 1.75 daN (decanewton), the other end of the belt 100 is attached to the frame, and the tension T exerted on the strand of the belt 100 is measured by a suitable measuring means S such as a force sensor. The pulley P is rotated at a speed of 43 rpm for 2 minutes of the test. Then, at the end of this 2 minutes, the force is measured on the still rotating pulley.

[0089] The coefficient of friction (COF) is then determined by the following relationship.

Equation

[0090] The coefficient of friction of the strand of the belt 100 tested in this way was evaluated to be 0.3.

[0091] After identifying all the characteristics of the belt 100 according to the examples of the embodiments, particularly the tensile elastic modulus and the coefficient of friction on the steel pulley representing the circular-grooved roller of the conveyor, tests were conducted to verify the performance of the belt 100.

[0092] Result 1: Determination of the maximum transmission torque

[0093] The test for determining the maximum transmissible torque of the belt 100 manufactured in this way was carried out on a test bench comprising two pulleys simulating the two rollers of the conveyor, one driving part, and one receiving part. The driving pulley rotates at 305 rpm. The resistance torque is gradually applied to the driven pulley in steps of 0.1 Nm (Newton meter) so that the belt slides on the pulley. This pair is shown in FIG. 14 and defines the abscissa of the graph described below.

[0094] When the belt 2,100 engages with the groove 12, the belt has a certain adhesion force with the bottom 14 of the groove 12 and can drive the roller 10. This adhesion will withstand a certain torque limit for the tangential force on the surface of the belt 2,100. If this limit is exceeded, slip will occur and it will no longer be driven. Practically, this means that the belt 2,100 slips within the groove 12.

[0095] Next, the overall slip ρ is calculated according to the relationship

Equation

[0096] Therefore, when the maximum torque is reached, i.e., when the driven pulley is blocked and its speed ω r becomes zero, the slip becomes 100%.

[0097] Referring now to FIG. 14, which shows a comparison of the occurrence of slip as a function of torque for a conventional circular belt 2 (curve A) and a belt 100 according to an example embodiment of the present invention (curve B).

[0098] Curve A shown in FIG. 14 shows that for the conventional circular belt 2, the slip is 100% at a maximum torque close to 0.7 Nm. On the other hand, curve B shows that for the belt 100 according to the example embodiment, the slip is 100% at a maximum torque close to 2.1 Nm. That is, the belt 100 has a torque transmission capacity about three times that of the conventional belt 2. In practice, this means that the drive rollers on conveyors 1a, 1b equipped with the belt 100 in this example embodiment of the present invention can drive three times the number of slave rollers 10 as the conventional circular belt 2.

[0099] Result 2: Durability test

[0100] The durability test of the belt 100 according to the example embodiment was carried out on a test bench simulating a curved conveyor. This test bench includes a drive roller and a slave roller arranged adjacent to the drive roller, but its longitudinal axis is not oriented parallel to the longitudinal axis of the drive roller, and more precisely, it is arranged at an angle offset by 6° with respect to the longitudinal axis of the drive roller. To lay the belt on the rollers according to the example embodiment, an elongation of 8% compared to the length at rest is required, which is converted to a laying tension of 80 N / strand (in the case of a tensile modulus of 1000 N). "Strand" means a portion of the belt 100 configured to extend between two rollers 10 during use. The drive roller rotates at 305 rpm. The test was carried out at room temperature.

[0101] To evaluate the behavior of the belt over time, the test consists of repeating a certain number of on / off cycles of 1 s / 1 s (seconds). This means that the drive roller rotates for 1 second, then stops for 1 second, then starts again for 1 second and continues until 500,000 cycles are reached. The acceleration / deceleration associated with the start / stop cycles combined with the inertia of the slave roller generates a resistive torque.

[0102] The belt according to the invention has been observed to pass this endurance test with limited wear marks. This means that the coefficient of friction remains stable over time.

[0103] A similar test was carried out on a conventional circular belt as described above. The circular belt has been observed to experience wear and become brittle.

[0104] This last test marks the end of the description and results related to the manufacturing example of the embodiment.

[0105] It should also be noted that in order to change the coefficient of friction, other tests were carried out on a belt similar to that shown in the example of the embodiment by only changing the rate of penetration of the fabric into the teeth. It was determined that the coefficient of friction should not exceed an approximate value of 0.8, because if this value is exceeded, there is a risk that the belt will turn inside out in the grooves of the rollers on the curved conveyor.

[0106] Therefore, the coefficient of friction between the belt 100 and the groove 12 of the roller 10 must be 0.8 or less.

[0107] Advantageously, this coefficient of friction of the belt 100 is non-zero and less than 0.8, and at the same time the tensile modulus of the belt 100 is between 500 N and 1500 N, advantageously between 800 N and 1500 N, preferably between 800 N and 1200 N.

[0108] More preferably, the coefficient of friction between the belt 100 and the groove 12 of the roller 10 is between 0.3 and 0.8, and is combined with the tensile elastic modulus of the belt 100 between 500 N and 1500 N, preferably between 800 N and 1500 N, and more preferably between 800 N and 1200 N.

[0109] The present invention also relates to a concave groove roller conveyor similar to the conveyors 1a and 1b shown in FIGS. 1 and 2.

[0110] These conveyors 1a and 1b include a plurality of rollers 10 having concave grooves 12 connected to each other in pairs by a belt 100 as described above. Advantageously, the belt 100 is installed between the rollers 10 with a laying tension between 60 N / strand and 100 N / strand.

[0111] FIGS. 15 and 16 show the belt 100 according to the present invention engaging with a concave groove 12 formed in a roller 10, for example, made of steel, and a concave groove 12 belonging to a drive head 18 made of plastic, for example, a composite material based on fibers embedded in polyamide (PA), polypropylene (PP), or a thermoplastic or thermosetting resin. In both cases, the convex teeth on the belly portion 106 of the body 102 of the belt 100 cooperate with the concave groove 12, particularly the bottom 14 of the groove 12. It is understood that the radius of curvature of the bottom 14 of the groove 12 is substantially equal to the radius of curvature of the teeth on the belly portion 106 of the body 102. Thereby, the contact surface between the belt 100 and the bottom 14 of the groove 12 is maximized.

[0112] FIGS. 15 and 16 also show that the belt 100 is installed in the groove 12 of the roller 10 of the conveyors 1a and 1b such that each belt 100 has a height H that is strictly lower than the depth PR of the groove 12 that receives each belt 100.

[0113] As described above, the transmission capacity of the belt 100 according to the present invention is at least twice that of the conventional circular belt 2. Therefore, the conveyor according to the present invention can be provided with twice as many slave rollers 10 as the conveyor provided with the conventional circular belt 2. This means that, for example, if a conventional conveyor is sized to include a plurality of drive rollers separated from each other by at least three to five slave rollers, the conveyor according to the present invention can include a plurality of drive rollers separated from each other by at least six to ten slave rollers. Of course, this can be even larger if the conventional conveyor is of such a size.

[0114] In light of the above, it is clear that the belt according to the present invention enables the improvement of the torque that can be transmitted by the belt and its stability. In fact, in use, the contact surface between the belt and the bottom of the groove of the roller is wide due to the convex shape of the teeth of the belt that conforms to the concave shape of the groove. In addition, the combination of this convex shape of the teeth and the coating arranged on the outer surface of the teeth means that the friction coefficient of the belt in the groove can be set to a controlled value. Due to the controlled friction coefficient and the presence of cords that improve the tensile modulus of the belt, the torque that can be transmitted and the level of deformation of the belt when in contact with one side of the groove can be controlled, which, in particular, limits the risk of the belt turning inside out in the curved part of the conveyor.

[0115] Another advantage is that the belt has durability over time. In fact, thanks to the friction coefficient that remains stable over time, the belt does not wear rapidly, thereby improving its service life.

[0116] Another advantage is the reduction in the manufacturing cost of the conveyor. In fact, thanks to the improvement in the torque that can be transmitted by the belt according to the present invention, many slave rollers can be made subordinate to the drive rollers in the conveyor. As a result, the number of drive rollers can be reduced, saving infrastructure and energy.

Claims

1. A transmission belt (100) for a roller conveyor (1a, 1b) having a roller (10) provided with a concave groove (12) made of steel or plastic, wherein the belt comprises: - An elastomeric body (102) having a back portion (104) and a belly portion (106) formed by a single tooth, and the outer surface of the elastomeric body (102) has a convex shape configured to engage with the bottom (14) of the concave groove (12) of the roller (10); - A set of tension cords (110) embedded in the body (102) between the back portion (104) and the belly portion (106) of the body; - A coating (112) disposed on the outer surface of the tooth, and the coating (112) defines a coefficient of friction with the concave groove of the roller, which is non-zero and less than or equal to 0.8, with the shape of the outer surface of the tooth. A transmission belt (100) comprising the above.

2. The belt (100) according to claim 1, wherein the coefficient of friction is 0.3 or more.

3. The belt (100) according to any one of claims 1 or 2, wherein the set of tension cords (110) defines a tensile elastic modulus of the belt between 500 N and 1500 N, preferably between 800 N and 1500 N, and more preferably between 800 and 1200 N.

4. The belt (100) according to any one of claims 1 to 3, wherein the cords (110) of the set of cords are made of a polyamide-based or polyester-based material.

5. The belt (100) according to any one of claims 1 to 4, wherein the coating (112) partially embedded in the tooth is selected from a knitted fabric, a woven fabric, a non-woven fabric, or a set of fibers.

6. The belt (100) according to claim 5, wherein the coating (112) is made of a material selected from polyamide, polyester, cellulose fibers such as cotton, a mixture of cellulose fibers and polyurethane, or a combination thereof.

7. The belt (100) according to any one of claims 1 to 6, wherein the body (102) is made of a material selected from ethylene-propylene-diene monomer, ethylene-propylene copolymer, polybutadiene, polyurethane, or natural rubber.

8. The body (102) is made of a material selected from ethylene-propylene-diene monomer or ethylene-propylene copolymer, the coating (112) is a film of at least partially cross-linked thermoplastic material containing at least 30% polyethylene, and the thermoplastic film covers the outer surface of the teeth. The belt (100) according to any one of claims 1 to 4.

9. The belt (100) according to claim 8, wherein the film contains particles and / or fibers of graphite, molybdenum disulfide, and / or polytetrafluoroethylene.

10. A conveyor (1a, 1b) comprising a plurality of rollers (10) provided with concave grooves (12) made of steel or plastic, the rollers being connected to each other in pairs by a belt (100) according to any one of claims 1 to 9, whereby the coating (112) of the belt contacts the bottom (14) of the concave grooves (12) of the rollers. Conveyor (1a, 1b).

11. The conveyor according to claim 10, wherein the belt (100) has a height (H) that is strictly lower than the depth (PR) of the groove (12) that receives the belt (100).

12. The conveyor according to any one of claims 10 or 11, wherein the concave grooves (12) of the rollers (10) are made of a plastic material selected from polyamide, polypropylene, or a composite material based on fibers embedded in a thermoplastic or thermosetting resin.

13. The conveyor according to any one of claims 10 to 12, wherein the belt (100) is installed between the rollers (10) with a laying tension between 60 N / strand and 100 N / strand.

Images