TIMING BELT WITH PROFILE-SIDE FABRIC LINING

Description

[0001] The invention relates to a toothed belt with at least one drive side provided with a tooth profile, wherein the tooth profile is provided with a fabric layer, and the fabric layer has a plastic coating at least on its outer side facing away from the tooth profile. Furthermore, the invention relates to a method for producing such a toothed belt.

[0002] The timing belts referred to here, such as those known from DE 10 2007 061735 A1, typically polyurethane timing belts, are manufactured by extruding the base material. During extrusion, reinforcements or tensile members, usually in the form of cords, are introduced into the extruded, still warm and relatively viscous material in a special outlet nozzle. These cords essentially absorb the tensile forces in the finished, cured timing belt.

[0003] The resulting still viscous polyurethane material, which forms the base material of the timing belt, is formed into the finished timing belt with the tension members between a belt and a forming wheel provided with external teeth, under heat extraction, whereby the belt wraps around the forming wheel under pressure over a wrap angle of approximately 200°. In the generic timing belts referred to here, a fabric layer runs onto the forming wheel on the toothed side of the timing belt shortly before the blank enters the wrap arc of the forming wheel. This fabric layer has a plastic coating at least on the outer side facing away from the tooth profile. This coated fabric, also called fabric reinforcement, is then pressed together with the blank into the shaping toothed outer contour of the forming wheel. Such fabric-reinforced timing belts are well known and advantageous, for example, with regard to wear reduction and noise reduction in timing belt drives.

[0004] Belts manufactured in this way are also used in wind turbines, for example, for adjusting rotor blades, and are therefore exposed to highly corrosive environmental conditions, particularly saltwater in offshore wind turbines. Such belts with a coated fabric reinforcement on the tooth side exhibit improved meshing with the associated pulleys, i.e., good tooth engagement, and provide protection and coverage for the tension members.

[0005] During the described and known production process, despite the greatest care, it can happen that the base material does not penetrate all areas of the fabric evenly during forming on the forming wheel. If the fabric is not fully penetrated during the manufacturing process, for example when using highly viscous PUR melts for the base material of the belt, areas can arise in the flank of the fabric reinforcement, i.e. in the edge areas of the future timing belt, where the fabric is not fully penetrated and is therefore open-pored. There is then a risk that moisture will penetrate through these edge areas due to gas exchange and / or capillary action during later use of the belt. This can subsequently spread across the entire width of the belt and could then lead to accelerated corrosion at the contact points with the tension member, thus reducing the service life of the belt.

[0006] In order to avoid such imponderables, the object of the invention was to provide a toothed belt and a method for its production in which undesirable corrosion stress caused by moisture penetrating the belt edges is avoided, perfect tooth engagement is still possible and a long service life of the belt is achieved even when used in a corrosive environment.

[0007] This problem is solved by the features of the main claim and the subordinate method claim. Further advantageous embodiments are disclosed in the respective subclaims.

[0008] At least in the lateral edge areas of the fabric layer, a seal is provided that extends to the lateral edges and the side surfaces bordering the timing belt, penetrating the fabric layer. Any pores present at the edge of the fabric or wetted areas not penetrated by the base material or coating are now sealed against the penetration of media and capillary action by the previously applied sealant, for example, by applying a sealing varnish. This ensures a long service life of the belt, even when used in corrosive environments.

[0009] A particularly advantageous design of the timing belt results from the use of a fabric layer that has a plastic coating only on the outer side facing away from the tooth profile, namely a so-called "doubled foil-fabric reinforcement." This means that the fabric layer is at least partially penetrated by the base material of the timing belt on its side facing the tooth profile, and in the central area of ​​the timing belt, almost completely. This simplifies the described manufacturing method and ensures extremely reliable processes.

[0010] A further advantageous embodiment is that the fabric layer also has at least one plastic coating on its side facing the tooth profile. The plastic coating on this side can then be designed in such a way that it bonds seamlessly to the base material of the timing belt.

[0011] The invention further comprises a material that penetrates the fabric layer, preferably a material that can be bonded to the base material of the timing belt and / or the plastic layers. The seal in the edge regions of the fabric layer can then be easily bonded to the adjacent materials and reliably prevents moisture penetration.

[0012] The invention further comprises the fact that the seal comprises a plastic material, preferably in the form of a plastic coating. Such a plastic material, in particular a plastic coating, makes the production of the timing belt particularly simple. The same advantages arise when the seal comprises a hot-melt adhesive based on ethylene vinyl acetate (EVA) or polyamide (PA) or is designed as such a hot-melt adhesive.

[0013] A further advantageous design is that the base material of the timing belt consists primarily of polyurethane, and the sealant consists of a polyurethane melt with an appropriately adjusted viscosity or a polyurethane-based varnish. By adjusting the viscosity of the polyurethane melt and / or varnish in this way, any displacement or distortion of the fabric structure can be reliably avoided, while maintaining the fabric's original elasticity and the required tooth load-bearing capacity.

[0014] The process according to the invention is advantageously used for the production, in which a) the base material of the timing belt is first extruded, b) during the extrusion of the associated outlet nozzle of the extruder, strength members or tensile members run into the extruded material, c) the blank thus created with tensile members is formed into the finished timing belt between a forming wheel provided with the negative of the toothing on its outer circumference and a belt circulating around the forming wheel, with heat being removed, whereby the belt surrounds the forming wheel over a wrap angle of approx.200° under pressure, d) shortly before the blank enters the arc of wrap of the forming wheel, a fabric layer runs onto the forming wheel, which is then pressed together with the blank into the shaping toothed outer contour of the forming wheel, whereby i) the fabric layer was provided with a plastic coating at least on its side facing the forming wheel before running onto the forming wheel and in its lateral edge regions with a seal extending up to its lateral edges and the side surfaces bordering the toothed belt and penetrating the fabric layer, ii) the coated and sealed fabric layer was also pre-shaped in such a way that it already has essentially the geometry of the tooth shape of the forming wheel before running onto the forming wheel, . after which the fabric layer pre-formed with the tooth shape runs onto the forming wheel in a meshing manner and is pressed together with the blank into the shaping toothed outer contour of the forming wheel to such an extent that the fabric layer and the seal are penetrated or connected to the polyurethane base material of the timing belt.

[0015] The preformed fabric layer thus meshes and synchronously runs onto the forming wheel and, together with the blank, is pressed into the toothed outer contour of the forming wheel. Only the base material is then deformed, and the fabric layer itself no longer needs to be pressed into the teeth of the forming wheel by the pressure generated in the base material. This allows, for example, the penetration depth of the base material into the fabric layer to be adjusted much more precisely than with conventional methods.

[0016] An advantageous development of the process is that the fabric layer is sealed with a plastic material that can be bonded to the polyurethane base material of the timing belt by painting, spraying, or dipping. These application methods are particularly easy to integrate into the manufacturing process or preparatory work.

[0017] The invention will be explained in more detail using an exemplary embodiment. The single figure shows the side area of ​​a section of a toothed belt 1 according to the invention, the drive side of which is provided with a tooth profile 2. The section of the tooth profile 2 shown here contains just one tooth in order to illustrate the inventive design of the toothed belt in detail. The toothed belt 1 is provided with tension members or cords 4, which are arranged in the longitudinal direction 3 of the toothed belt and integrated within the base material 5.

[0018] The tooth profile 2 of the toothed belt is provided with a fabric layer 6, wherein the fabric layer here has a plastic coating 7 on its outer side facing away from the tooth profile 2.

[0019] In the lateral edge area 8 of the fabric layer 6, which is visible here, a seal 10 made of a polyurethane-based lacquer is provided which extends to the lateral edges of the fabric layer and the side surfaces 9 bordering the toothed belt and penetrates the fabric layer.

[0020] The fabric layer 6 is more or less completely penetrated by the base material of the timing belt on and from its side facing the tooth profile. List of reference symbols (part of the description)

[0021] 1Timing belt 2Tooth profile 3Longitudinal direction 4Tension member / Cord 5Base material of the timing belt 6Fabric layer 7Plastic coating of the fabric layer 8Edge area of ​​the fabric layer 9Side surface of the timing belt 10Sealing

Claims

1. Toothed belt (1) having at least one drive side provided with a toothed profile (2), wherein the toothed profile is provided with a fabric layer (6) and at least on its outside facing away from the toothed profile (2) the fabric layer has a coating (7) made of plastics material, wherein at least in the lateral edge regions (8) of the fabric layer a sealing (10) of the fabric layer which extends to the lateral edges thereof and the lateral surfaces (9) delimiting the toothed belt and which penetrates the fabric layer (6) is provided, characterized in that the sealing (10) comprises a hotmelt adhesive based on ethylene vinyl acetate (EVA) or on polyamide (PA) or characterized in that the main material (5) of the toothed belt (1) is substantially composed of polyurethane and the sealing (10) is composed of a polyurethane melt or a polyurethane-based lacquer.

2. Toothed belt according to Claim 1, wherein starting from its side facing the toothed profile the fabric layer (6) is at least partially penetrated by the main material (5) of the toothed belt (1).

3. Toothed belt according to Claim 1, wherein on its side facing the toothed profile (2) the fabric layer likewise has at least one coating made of plastics material.

4. Toothed belt according to any of Claims 1 to 3, wherein the sealing (10) comprises a material penetrating the fabric layer (36), preferably a material joinable to the main material (5) of the toothed belt (1) and / or the plastics material layers.

5. Toothed belt according to any of Claims 1 to 4, wherein the sealing (10) comprises a plastics material, preferably in the form of a plastics material lacquer.

6. Process for producing a toothed belt made of thermoplastic polyurethane according to Claims 1 to 5, wherein a) the main material of the toothed belt is initially extruded, b) during the extrusion from the corresponding outlet die of the extruder strength members or tensile members are introduced into the extruded material, c) the resulting precursor comprising tensile members is formed between a forming wheel provided with the negative of the tooth pattern on its outer circumference and a belt running around the forming wheel with removal of heat to afford the finished toothed belt, wherein the belt wraps around the forming wheel under pressure at a wrap angle of about 200°, d) shortly before entry of the precursor into the wrapping arc of the forming wheel a fabric layer is introduced onto the forming wheel and is then together with the precursor pressed into the shapingly toothed outer contour of the forming wheel, wherein i) before being fed onto the forming wheel, at least on its side facing the forming wheel, the fabric layer was provided with a coating made of plastics material and in its lateral edge regions with a sealing which extends to the lateral edges thereof and the lateral surfaces delimiting the toothed belt and which penetrates the fabric layer, ii) the coated and sealed fabric layer was also preformed such that it already substantially has the geometry of the tooth shape of the forming wheel before it is fed onto the forming wheel, e) characterized in that the fabric layer preformed with the tooth shape is then meshingly fed onto the forming wheel and is then together with the precursor pressed into the precursor in the shapingly toothed outer contour of the forming wheel to such an extent that the fabric layer (6) and the sealing are penetrated by and joined with the polyurethane main material (5) of the toothed belt (1).

7. Process according to Claim 6, wherein the sealing of the fabric layer with a plastics material bondable to the polyurethane main material (5) of the toothed belt (1) is carried out by lacquering, spraying or immersing.