Belt joints

Abstract

A method of manufacturing a joint in a toothed belt, the toothed belt comprising a first belt section 10 having a first end-edge and a second belt section 20 having a second end-edge, the sections hav

Description

The present application relates to a method of making a joint in a belt, particularly for toothed belts. Introduction Endless belts can be formed by looping a desired length of belt material and forming a joint such that a first end of the belt material is joined to a second, opposing end. Common joining methods include vulcanised / spliced joints, butt joints and mechanical fasteners. One problem with this method is that it introduces a discontinuity into the belt (i.e. the joint) which is typically the weakest region of the belt and prone to breaking. Truly endless belts (as shown in figure 1) can be formed by winding a strip of belt material to form the belt as a continuous loop instead of joining opposing ends of a belt together. The belt doesn’t have a lateral joint and so can withstand comparatively higher tensile loads without being prone to failure. These belts are far more complex, costly and time-consuming to manufacture, particularly when they are reinforced with fibre layers or cables. There are numerous types of belts used in industry for different conveying or drive applications. Many prevalent types of belt require the use of teeth, typically on the underside of the belt to engage with corresponding grooves on a drum / roller. This ensures an accurate, one-to-one belt movement with respect to the rotating drum / roller. Teeth are used conventionally for timing belts and positively driven belts, which are a particular focus of the invention described herein. When joining the ends of toothed belts together, the teeth make the choice of joint more limited. For example, for a monolithic belt, a butt joint is typically used, where the ends of the belt are simply joined along a straight line running laterally in-between adjacent teeth. A simple butt joint of this type can be more prone to failure because the joint is a simple line perpendicular to the direction of tension in the belt in use. Figures 2 shows an example of another conventional joint for a toothed / timing belt, 5 formed using mechanical fasteners / pins. The teeth are provided with through- holes in the vicinity of the joint. Fingers are spliced into the ends of the belt and interlocked. The steel pins are inserted laterally through the aligned through-holes of the teeth along the fingers to increase the strength of the joint. However this type of joint is more complicated and they are not suitable for some applications. 10 It is the aim of the present invention to mitigate or overcome one or more of the above-mentioned problems. Summary of invention According to one aspect of the invention, there is a method of forming a belt joint, by bringing a first end-edge of a first section of a belt into contact with a second end-edge of a second section to form an interface between a first section and second section, and joining a common tooth to both the first and second sections such that the common tooth extends across the interface. According to a further aspect of the invention there is a belt comprising a joint formed between first and second belt sections defining an interface, a common tooth joined to the first and second sections such that the tooth extends across the interface. Preferably, the belt comprises a toothed belt, e.g. having a plurality of teeth spaced in the longitudinal direction of the belt. The belt may be a timing belt, or a conveyor belt or a drive belt. The common tooth may be on an underside of the belt. The plurality of teeth may be on an underside of the belt. An upper side or surface of the belt may or may not be devoid of teeth. The toothed belt may have a defined / regular tooth spacing in the longitudinal direction. The joint / interface may extend in a longitudinal direction of the belt a distance greater than or equal to the tooth spacing. One or more tooth of the belt may be removed prior to forming the joint. There may be a plurality of common teeth. The one or more common tooth may be oriented in parallel with plurality of teeth of the belt. The one or more common tooth may be spaced from an adjacent one or more of the plurality of teeth, e.g. equidistantly spaced or according to a regular spacing of the plurality of teeth. The joint / interface may extend in both a longitudinal and lateral direction of the belt, e.g. obliquely. The joint / interface may follow a path that changes directions a plurality of times, e.g. in the longitudinal direction, over the width of the belt. The joint / interface may be formed as inter-engaging fingers in the fist and second endedges. The joint / interface may follow a repeating, zig-zag, concertina, squarewave or castellated pattern. The joint may comprise a spliced joint. The common tooth may be laterally oriented. The common tooth may be straight / linear in form. The common tooth may extend across the interface a plurality of times, e.g. over the lateral width of the belt. The tooth may extend across the interface three or four or more times over the width of the belt. According to a further aspect of the invention there is a method of manufacturing a joint in a toothed / timing belt as according to appended claim 1. According to a further aspect of the invention there is a toothed / timing belt as defined in appended claim 5. Joining the sections may include one or a combination of welding, fusing and / or bonding, e.g. to form the joint / interface. Optional method steps or features are defined by way of dependant claims 2-4 and 6-25. The common tooth protects the joint by covering the interface and therefore reinforces the interface between the two ends, e.g. making the joint less prone to wear, delamination, tearing or the like and potentially prolonging the life of the belt. The belt may withstand higher tensile loads at the interface, even when not reinforced with fibres or wires within the belt, and therefore can be produced cost-effectively. The interface typically follows a continuous path over the full lateral width of the belt, e.g. from one lateral edge of the belt to the opposing lateral edge. The interface can be defined at the intersection of an end-edge of one section with the other section of belt, i.e. where the end-edge terminates with respect to the other section. In some embodiments the end-edges of the first section may abut directly against the second end-edge of the other section such that there is little or no overlap between the sections. Hence the interface is at the butted end-edges. In most applications however, the first and second sections will typically overlap, at least partially, meaning the first and second end-edges are not butting. The interface is formed where one of the end-edges terminates with respect to a major surface of the other section. The maybe two or more interfaces, for example a first interface in the top surface (e.g. upper / outer surface or a first major surface) or bottom surface (e.g. lower / inner or a second major surface) of the belt. The common tooth must be attached to both the first and second sections and so is continuous over at least a portion of the interface, meaning it comprises a portion which does not terminate at the interface and extends over / across the interface. Where the common tooth comprises an edge that extends away from the surface of the belt (e.g. the inner or outer surfaces), the edge may intersect with the interface such that the tooth extends from one section to the other of the sections. The tooth may intersect with the interface one or a plurality of times, for example 2 or more times, or 3 or more times, or 4 or more times, or 5 or more times, or 7 or more times, or 10 or more times. The belt may comprise a plurality of non-common teeth which do not extend over the interface. The non-common teeth may provide engagement with a driving / timing mechanism (i.e. a geared pully / drum) for the rotation of the belt in use. For example, the driving mechanism may have complementary engagement members (e.g. teeth) which engage with the non-common teeth. The non-common teeth are located in the first and / or second, and or middle sections of the belt strip. The common tooth is configured to operate with the same driving mechanism that drives the rotation of the belt through the non-common teeth of the first and second sections. In most applications the shape / profile of the common tooth / teeth will be identical to or substantially the same as the non-common teeth, i.e. being the same shape and size; however, the common tooth may differ just so long as it does not effect the rotation of the belt, i.e. it does not negatively interact with the driving mechanism. The width, longitudinal depth (thickness) and / or height of the common tooth may match that of other, e.g. non-common, teeth of the belt. The common tooth may be equally spaced from an adjacent tooth (e.g. common or non-common tooth) as the other non-common teeth in the longitudinal direction. The tooth spacing may be preserved between the common and other teeth. The belt is comprised from one or more strips of material having a longitudinal direction. The longitudinal direction corresponds to the length dimension of the strip. The length can be set according to the application of use, for example, the length may be greater than 5cm, or greater than 10cm, or greater than 20cm, or greater than 50cm, or greater than 1 m, or greater than 2m, or greater than 5m, or greater than 10m, or greater than 20m, or greater than 50m. The strip may comprise the first and second sections which may be brought together such as to form the joint. In alternative embodiments the belt may be comprised from a plurality of strips where the first section of one strip is bonded / attached to the second section of an adjacent strip. The strips may be elongate. The belt direction of travel in use may be in the longitudinal direction, i.e. along its length. The belt width (or strip or section width) may be defined as the direction that is perpendicular to the longitudinal direction. The belt / strip width may be greater than 1 cm, or greater than 2cm, or greater than 5cm, or greater than 10cm, or greater than 20cm, or greater than 50cm, or greater than 1m.Optionally, the width may be less than 1cm, or less than 2cm, or less than 5cm, or less than 10cm, or less than 20cm, or less than 50cm. The strip may have first and second major surfaces which correspond to the inner and outer surfaces once formed into a belt. The common tooth my extend from a major surface in a direction that is perpendicular to the longitudinal direction, for example, by 1 mm or more, or 2mm or more, or 3mm or more, or 5mm, or 1 cm or more, or 2cm or more, or 3cm or more. The common tooth and non-common teeth may be the same height, i.e. they extend from the major surface by the same distance. Alternatively, there may be a height difference between the common teeth and non-common teeth which may be less than 1 mm, or less than 2mm, or less than 5mm, or less than 1 cm. The first and second sections may have the same width. The middle section may be the same width as the first or second section. The common tooth may be elongate, such as to have a longer length than its width. The width a of the common tooth may be the same width as the non-common teeth. The tooth height may be substantially more than its width, for example greater than twice the width, or greater than three times the width, or greater than five times the width. The common tooth may fully extend across the width of the belt (i.e. the strip). Alternatively, the common tooth may only partially extend along the width of the belt. The common and non-common teeth may extend equally along the width of the belt, i.e. they are spaced apart along the longitudinal direction but are in the same position in the width dimension of the belt. In the plane which is parallel to the longitudinal direction, the cross-section of the common tooth may be cuboidal (eg. rectangular or square) or may be tapered from its root to its tip. Various tooth profiles are possible, including triangular, being Isosceles, equilateral, Scalene, or right angle triangle; domed / curved, e.g. being semi-circular. The common tooth profile may be symmetrical in cross section, e.g. trapezoidal or semicircular, or non-symmetrical. Heat and / or pressure may be applied to the first and second sections of the belt. An adhesive may be melted between the sections and / or common tooth to aid bonding the parts together. A predetermined elevated temperature and / or pressure may be maintained for treatment / formation of the joint, e.g. for a predetermined time. The opposing ends of the belt and the common tooth may be held in a press. The treatment may comprise heating the belt between 80-250°C; optionally between 120-200°C; optionally between 150-170°C. The heat / pressure treatment may be applied for up to 1 hour; optionally up to 30 mins; optionally up to 10 mins; optionally up to 5 mins; optionally up to 2 mins; optionally up to 1 min. The treatment may be at least up to 1 min; optionally at least 2 mins; optionally at least 5 mins; optionally at least 10 mins; optionally at least 30 mins; optionally at least to 60 min. The listed durations may instead be used to form appropriate ranges for the duration for which the treatment time is to last (e.g., between 10-30 mins). The treatment pressure may be at least 0.1 bar, for example at least 0.2 bar, 0.5 bar, 1 bar, 2 bar, 5 bar, or at least 10 bar; optionally at least 20 bar. The treatment pressure may be less than or equal to 20 bar or 10 bar, for example less than or equal to 8bar, 5 bar, 2bar, 1 bar, 0.5 bar or 0.2 bar. The listed pressures may instead be used to form appropriate ranges for the pressure (e.g., between 0.1-10 bar or 2-5 bar). A bespoke press or mould may be used for applying the common tooth to the joint. The bespoke press / mould may comprise a cavity for receiving the common tooth and holding the common tooth under pressure against the belt in the vicinity of the joint / interface. The belt may include reinforcing elements such as fibres or wires running substantially continuously through the strip of the belt, and / or first section and / or second section. The reinforcing elements are capable of withstanding high tensile loads. The fibre may comprise para-aramid fibres such as Kevlar (registered trade mark). The fibres may comprise other types of aramid fibres such as metaaramids. The fibre may comprise carbon fibres, nylon, glass or graphene fibres. The fibre section may comprise a mixture / blend of different combinations of fibres. The wires may be alloy, or non-alloy, and may comprise steel and / or aluminium. The wire may comprise aramid. The wires may be wrapped to cords (wired rope). The wire or cord diameter may be 1 mm or more, or 2mm or more, or 3mm or more, or 5mm, or 1cm or more. The fibres may be provided in the form of a textile layer, such as a mat, web, net or mesh. The fibres may be interlaced, knitted or woven or applied to a foil / support layer. The wire and / or fibres may extend solely longitudinally in the belt (i.e. the strip thereof) and may terminate in proximal to the first and / or second end-edge. The belt may be comprised from a Polyvinyl Chloride (PVC) and / or Polyurethane (PU) material. The first and / or second section may be comprised from the same material as the common teeth. The formed belt may have an unfurled length (e.g., when the belt is not formed into an endless belt) of 1 m or more, 2m or more, 5m or more, e.g. 10m or more, 20m or more, or 50m or more. The interface may follow a tortuous path through the width of the belt. The endedges may be profiled / cut define opposing formations or protrusions in the first and second end-edges. The opposing formations may be interlocked or interposed at the interface. The formations may comprise fingers / wedges (e.g. spliced formations). The interface may be angled with respect to the longitudinal direction such to have a wedge appearance, the angle may be greater than or equal to 5 degrees, 10 degrees, 20 degrees, 30 degrees, 45 degrees or 60 degrees. The belt or strip (e.g. the first, second and / or middle sections thereof) may comprise a plurality of layers or plies. The joint may comprise mechanical fasteners joining the first end-edge to the second end-edge. The fasteners may comprise staples, clips, pins, eyelets or a combination thereof. References to fibres herein may also refer to bundles of fibres, such as yarns. Workable embodiments of the invention are described in further detail below, by way of example only, with reference to the accompanying drawings, of which: Figure 1 shows a truly endless timing belt in the state of the art. Figure 2 shows a timing belt with a mechanical joint in the state of the art. Figure 3 shows a belt joint at different stages of a manufacturing process according to an example of the invention. Figure 4 shows a belt joint according to a second embodiment with overlapping edges. Figure 5 shows a third embodiment comprising a spliced joint. Figures 6a-f show various other plan views of arrangements of teeth and interface according to further embodiments of the invention. Figure 7 shows another embodiment of the invention with cleats. Figure 8 shows various alternative tooth profiles and types. Detailed description Workable examples of the technology will now be described with reference to the figures. Figures 1 and 2 are representative of the current state of the art for manufacturing timing belts. Timing belts refer to toothed belt made from a flexible material such as rubber or other polymers and have wide applications including as cambelts, or conveyer belts. A first aspect of the invention is shown in figure 3. An open-ended toothed belt comprises first 10 and second 20 sections which are joined forming an endless belt. The bottom surface (i.e. the inner surface in use; obscured from view in figure 3) is formed with a plurality of teeth 50 being spaced apart in the longitudinal direction L of the belt. The first 10 and second 20 sections comprise respective first 11 and second 21 end-edges which are brought (i.e. butted) together forming and interface 30 across the width of the belt. A tooth 40 is placed under / over the interface 30 (on the inner surface) as shown in figure 3(b). The belt is then treated such that the first 10, second 20 sections and tooth 40 are bonded together at the interface 30 as shown in figure 3(c). The tooth 40 is common to both the first and second sections 10, 20 as it extends over the interface 30 and defines a common tooth 40. Hence, the common tooth 40 is bonded to both the first 10 and second 20 sections. The teeth 50, common tooth 40 and belt sections 10, 20 may be comprised from the same material which. The treatment uses heat and pressure to partially melt the rubber material which is then welded together once re-cured. Alternatively and / or additionally, the treatment may include an adhesive located between the sections and / or common tooth to further increase the strength of the joint. The common tooth 40 strengthens the bond at the joint and provides protection from wear (as the belt rotates around pullies), thus increasing the service life of the belt. The manufacturing method is comparatively quicker than those in the art meaning the belts can be produced more cost effectively. It is key that the common tooth 40 (at least partially) extends over the interface 30 and is bonded / joined to both sections 10, 20 to achieve at least some benefits associated with the invention. The belt has first 25 and second 35 lateral edges that extend in the longitudinal direction L. The distance between lateral edges defines the belt’s width. The interface extends between the first and second lateral edges. A common tooth of the desired profile can be formed separately and attached to the interface 30, for example fusing, using an adhesive and / or welding. Teeth could for example be formed by extrusion and cut to the desired length. The common tooth 40 may be initially attached to the belt (for example at the first or second sections), removed and then reattached at the interface 30 as a common tooth 40. The standard tooth id preferably removed at the surface of the belt, e.g. to leave a belt of uniform depth at the site of the removed tooth when compared with the depth of the belt in-between teeth. Thus a standard tooth can be removed and reattached over the interface 30 to provide the common tooth 40. This ensures the common tooth matches the profile of the other teeth. This process can also be used for a plurality of teeth, e.g. where more than one common tooth is used over the interface 30, as will be described below. When removing one or more tooth, this can be achieved using a knife / blade, a heated knife, a hot wire, a waterjet cutter or other suitable severing means. This ensures the tooth is retained intact for reattachment after the interface has been formed. In other examples an existing tooth or teeth can be removed in a destructive manner, e.g. by grinding, milling or the like. The removed tooth is then replaced by a new, common tooth of the same or similar profile. Although not shown, the press used to apply heat and pressure to both the belt and common tooth may have cavities shaped to receive the teeth. The common tooth 40 may be placed in the respective empty cavity and thereby held in place whilst it is attached / fused with the belt over the interface 30. In this regard, it has been found beneficial to produce a mould / cast of the existing toothed belt profile, which can then serve as the press member for holding the belt during application of the common tooth 40. The mould may be produced from silicone for example. In other examples, the common tooth 40 can be formed by moulding / curing resin directly to the belt, i.e. by using injection moulding. A die in the form of the tooth can be located at the interface 30 and filled with the desired polymer / resin, e.g. at elevated temperature akin to moulding process. The material cures into the shape of the common tooth 40 and the die is removed. The common tooth 40, first section 10 and second section 20 are bonded together once cured. The belt comprises a plurality of non-common teeth 50 which are located on either the first 10, second 20 or middle 60 sections. The common tooth 40 engages with geared drive, sprocket or drum, i.e. in the same was as normal tooth, to drive the rotation of the belt or ensure timing of the belt. The common tooth 40 has the same profile, e.g. being identical in shape and size, to the non-common teeth 50 so that it can also engage with the geared driver. As shown in figure 3(c), the common tooth 40 is equally spaced with respect to the other non-common teeth 50. Figure 4 shows an alternative embodiment of the invention where the second section 20 partially extends over the first section 10 and is treated with the common tooth 40 in place. The second end-edge 21 is brought towards the first end-edge 11 (i.e. up to and then past). As shown in the detailed view at the top of figure 4, the end-edges of the first 10 and second 20 sections may be profiled, e.g. being stepped or of reduced / tapering depth such that they overlap within the depth of the belt. The first 11 and second 21 end-edges aren’t abutting in a simple end-to-end arrangement as shown in the first embodiment but are rather overlapping. The interface 30 is instead formed where the first end-edge 21 the terminates on the underside (inner surface) of the belt. The interface 30 is obscured from view in figure 4 as it is on the underside of the belt and the dashed-dotted line shows the location of interface 30. The common tooth 40 is bonded to the first 10 and second 20 sections across the interface 30 in the same way as the first embodiment and can be attached using the same methods. A second interface 31 is present on the top side of the belt where the second endedge 21 of the second section terminates over the first section. The top surface isn’t typically subject to the same levels of wear as the inner surface as it doesn’t come into direct contact with the toothed pullies. In practice, the second interface may be smoothed out when the first and end sections are treated. An adhesive or reinforcing material can be inserted in the overlapping region of the first 10 and second 20 sections in order to provide a stronger joint, e.g. that is more resilient to shear, tension, bending and or delamination, as necessary. Where both sides of the belt are toothed, the process of adding a common tooth can be repeated on the top surface at interface 31 such that there is one or more common teeth on both the top and bottom sides of the belt. The interface 30 in the first and second embodiments extends perpendicularly to the longitudinal direction; however, it may instead be angled with the respect to the longitudinal direction as will be described in further examples below. In other examples, the interface may follow a tortuous path, e.g. changing directions a plurality of times between the opposing lateral sides / edges 25, 35 of the belt. Figure 5 shows an embodiment of the invention with spliced or zig-zag interface 32 created by forming complimentary profiles in the opposing end-edges of the first 10 and second 20 sections and then joining the first and a second sections together such that the complimentary end-edge profiles fit together. In this manner, the interface 32 extends not only in the width direction of the belt, but also in longitudinal direction L. This means that the interface 32 has a longer length than the simple, linear interface 30. The profile in each end-face in this example comprises a plurality of fingers extending in the longitudinal direction which are inter-locked when the joint is formed. The fingers in the first section end-edge are laterally offset from the fingers in the second section end-edge so that they are complimentary and create a close fit when brought together. The interface is defined along the zig-zag profile of the spliced joint. In some embodiments, the profile is cut through the entire depth of the first endedge and the opposing second end-edge. In other examples, the profile is partially cut through only a portion of the belt depth and a different / offset profile may be cut through the remainder of the depth. This is akin to the stepped profile shown at the top of figure 4 but applied to a spliced joint. The fingers thus partially overlap so the interface is formed at the termination of the first end-edge of the first section on the bottom side of the belt, as with the embodiment of figure 4. Similarly, the top surface has a second interface with which may be offset from the first interface. For example the interface in the top surface may follow a similar / parallel path to that of the interface on the bottom surface but offset therefrom in the lateral direction. Where the sections of any embodiment of the invention may be comprised from a plurality of ply layers, the top and bottom ply layers may be spliced at different lengths such that the cuts are offset in the longitudinal direction. As the common tooth 40 in figure 5 extends perpendicularly to the longitudinal direction, it repeatedly extends over / across the interface 32 and therefore has multiple points / regions of contact with both the first and second sections. Depending on the desired tooth spacing and the length of the fingers in the longitudinal direction L, there may be multiple common teeth spanning both the first 10 and second 20 sections. For example, if the longitudinal length of the interface 32 is less than or equal to the tooth spacing, a single common tooth 40 may be applied mid-way along the longitudinal length of the interface. However, if the longitudinal length of the interface 32 is greater than or equal to the tooth spacing, then a plurality of common teeth may be spaced at different longitudinal lengths of the interface 32, whilst also preserving the regular tooth spacing. Where a plurality of common teeth 40 are applied, the relative position of the teeth along the interface may be adjusted by adjusting the longitudinal length of the profile in each end-edge and also its location relative to exiting teeth. For example, it may be beneficial to have a common tooth located at the apex of the fingers and / or at a mid-way along the fingers. In the different embodiments discussed above, the sections 10, 20 may be part of the same strip of material where the first section 10 is at one end of the strip in the longitudinal direction and the second section 20 is at the opposite end. A middle section 60 therefore extends between the first and second sections. The first and second sections may be brought together by folding at least one of the sections around, such as to the bring the first and section end-edges 11,21 together and then are joined as described above. The length of the strip in the longitudinal direction L determines the size of the belt once the joint is formed, i.e. a longer strip can be used to form a longer belt, and can be set as required / desired by the user or purpose for which the belt is to be used. Alternatively, multiple strips can be joined using the methods described above, where the first section 10 of a first strip is joined to the second section 20 of an adjacent strip. The common tooth 40 is still formed at the interface 30 of adjacent strips. Hence each strip has at least two common teeth 40, i.e. at each opposing end-edge 11,21 in the longitudinal direction L. The desired length of belt can thus be formed by attaching further strips in turn. Figure 6 shows plan views of belt surfaces for a variety of different embodiments of the invention with various tooth and joint / interface arrangements. The first representation in 6(a) corresponds to the embodiment shown in figure 1. The interface 30 extends perpendicularly with respect to the longitudinal direction L and so there is only a single common 40 tooth to both the first and second sections 10, 20. The common tooth 40 extends continuously over the interface between the opposing edges of the belt. In the embodiment shown in 6(b) the interface 33 is extending at an oblique angle a with respect to the longitudinal direction, i.e. one or both of the first and second sections has an angled end-edge. As the teeth still extend perpendicularly to the longitudinal direction, the interface can intersect with one, two, three or more teeth, meaning there are potentially a plurality of common 40 teeth spanning the first and second sections. The dotted lines represent intersections between the common tooth and interface, specifically how the interface runs through / behind the tooth. It should be understood that common teeth will obscure the view of the interface when the belt is seen from the bottom side. Figure 6(c) shows an embodiment with V-shaped teeth (i.e. chevrons) and a perpendicular extending interface. The single common tooth has two intersections 34 with the interface and therefore extends across the interface twice. Figure 6(d) shows a splice cut interface with perpendicularly / laterally extending teeth and substantially corresponds to the embodiment shown in figure 5. There are three common teeth in this example spanning the first and second sections, each having multiple intersections with the interface. Figure 6(e) shows and embodiment where the teeth (i.e. common and noncommon) teeth are not continuously extending across the width of the belt. There are total of nine common teeth (i.e. three rows of teeth) spanning the first and second sections, having varying number of intersections with the interface depending on their location. It will be appreciated that greater or fewer rows of teeth, or teeth in a row, could be used in different examples. Figure 6(f) shows an embodiment where the teeth extend across the width of the belt at an oblique angle to the longitudinal direction, in combination with a spliced joint. Various other configurations are possible using the above principles to ensure at least one common tooth intersects with the joint interface. In any such examples, the joint interface may be formed as a first step, e.g. with the first and second sections undergoing a joining process, and the common tooth / teeth may be applied as a further step. Alternatively the joint may be formed at the same time as the common tooth / teeth is applied. As the teeth may be used to mechanically drive the rotation of the belt or else to maintain the correct belt position / timing, the common teeth must be configured to engage with the mechanical driver (e.g. the teeth of the gear wheel, drum or similar) in the same way as the non-common teeth. The common tooth / teeth 40 in the embodiments described above are all parallel with the remaining teeth. The common teeth are also spaced apart from the adjacent teeth by the same distance in the longitudinal direction. However, in some embodiments, there may be gap, i.e, ‘missing teeth’ which may mean the teeth aren’t evenly spaced but the common teeth are still in sync / phase with the remaining teeth. The number of common teeth 40 may be dependent on the angle of the end-edge (with respect to the longitudinal direction), shape of the interface (e.g. splice cut) width of the sections, and / or dimensions on the teeth (i.e. width and length). As shown by embodiment 6(e), there may be a high number of teeth, for example more than 10. Figure 7 shows an embodiment where the top surface comprises a plurality of walls or cleats 60 which will be known to the skilled person to space, grasp, grip, or divide items being conveyed by the belt. The walls for the belt may be formed using the same process described above for the common teeth, such that there are one or more common walls 60 spanning the first and second sections. Thus the invention is not limited only to teeth but can cover other protrusions from the belt, which typically occur at regular spacing along the belt surface. Both teeth and other walls can be used collectively to reinforce a joint interface, e.g. on opposing sides of the belt, as necessary. Although the walls shown in figure 7 are simple dividers, it should be understood that any cleat known in the art can be attached to belt using the method described above. The teeth / walls in the embodiments described above are shown to be rectangular in cross sectional profile. However, the invention is equally applicable to other shaped teeth such as tapered, triangular, or curved teeth. Figure 8a shows a variety of different teeth profiles which may be suitable for use with the invention. The teeth profiles are generally tapered in from, extending from a wider base / root to a narrower tip. However the different possible teeth profiles allow for symmetrical or non-symmetrical teeth with either straight or curved sides. Figure 8b shows examples of other types of teeth which could be used with the invention. The embodiment on the far left shows asymmetrical curved tooth formed into a plurality of rows and columns with reference to the longitudinal direction. The middle-left example shows triangular teeth with one angled edge and one straight edge (i.e. perpendicular to the inner surface of the belt) such that the teeth a ramped or akin to a saw tooth profile. The middle-right example shows a plurality of circular-button teeth set out in rows and columns. The right-hand example shows an example three-dimensional profile of chevrons, e.g. corresponding with the embodiment of figure 6(e). Its should be understood that the total number of common teeth can vary between embodiments, the number of such teeth is only limited to what is practical to fit along a longitudinal length of the interface of the belt joint. However there can be as many as 5, 10 or 20 common teeth if desired. Similarly, a common tooth my intersect with the interface a plurality of times depending on the size and shape of the interface and tooth. For example, there can be as many as 3, 4, 5 or more intersections between the common tooth and interface. The technology described herein may be applied to a variety of belt types, including timing belts and monolithic belts, as well as laminate or multiply belts. The invention may also be applied to reinforced belts. The technology is suitable for hygienic belt applications if necessary. The invention may be applied to any conventional belt materials, including PU, PVC, silicone and the like. Due to the fact that the teeth have not been cut part way along their length during the joint / splice forming process, they are strong and create an un-interrupted cross member reinforcement to the joint. The common teeth can be made up from the same colour material as the belt or an alternative colour which would highlight the splice area and aid identification of the splice area for preventative maintenance checks and evaluation. Teeth can also be removed and replaced with alternative colours for a variety of reasons. Where new teeth are applied over the interface, they can be made from the same or different material from the remainder of the belt. A different blend of PU may be used to further reinforce the joint if necessary. Also, it is possible to use different reinforcing material within the tooth itself, for example a Para-Aramid or Polyester material within the tooth core. The invention described herein is compatible with the applicant’s earlier inventions disclosed in published UK patent application GB2623392. As such the common tooth / teeth reinforcement of the present invention may be applied to a belt joint that has a reinforcing material, e.g. such as an aramid material, spanning the joint interface within the thickness of the belt material. This allows two types of reinforcement to be applied to the joints of toothed belts in a manner not hitherto realised.

Claims

1. A method of manufacturing a joint in a toothed belt, the toothed belt comprising a first belt section having a first end-edge and a second belt section 5 having a second end-edge, the sections having a longitudinal axis and a pluralityof teeth spaced apart along the longitudinal axis, the method comprising the steps of:bringing the first and second end-edges together to form an interface between the first and second sections,10 fusing, bonding or adhering a common tooth to both the first andsecond sections such that the common tooth extends across the interface.

2. A method according to claim 1, where the common tooth is joined across the interface at elevated temperature and / or pressure using a press having a15 cavity shaped to correspond with the common tooth.

3. A method according to claim 1 or 2, where the common tooth is preformed and located at the interface.20 4. A method according to claim 3, the common tooth being initially formedintegrally as part of the first or second section, the common tooth being removed from said first or second section prior to forming the joint and reattached across the formed interface as a common tooth.25 5. A toothed belt comprising,a longitudinal axis,a plurality of teeth spaced apart along the longitudinal axis,a joint between a first end-edge of a first section of the belt, and asecond end-edge of a second section of the belt, the joint defining an30 interface between the first and second end-edges such that the first andsecond sections lie on either side of the joint,a common tooth fused, bonded or adhered to both the first and second sections such that the common tooth extends across the interface.

6. A belt according to claim 5, wherein the common tooth is elongate in form, a first portion of the length of the common tooth being joined to the first section and a second portion of the length of the common tooth being joined to the second5 section.

7. A belt according to claim 6, wherein the common tooth extends across a majority of a width dimension of the belt.10 8. A belt according to claim 6, wherein the interface comprises a line in amajor surface of the belt along which at least one of the first and second sections terminates and the common tooth spans or intersects said line.LO 9. A belt according to claim 8, wherein the first and second sections overlap15 at the interface and the line is a first line in a first major surface of the belt, which is offset from a further line in the opposing major surface of the belt.i—10. A belt according to any of previous claims 5 to 9, wherein the interface is, at least in part, perpendicularly oriented with respect to the longitudinal axis.2011. A belt according to any of claims 5-9, wherein the interface is at least in part obliquely angled with respect to the longitudinal axis.

12. A belt according to any of claims 5-11, wherein the interface changes25 directions a plurality of times along a length of the joint.

13. A belt according to claim 12, wherein the first end-edge comprises a first profile which is complimentary to a profile of the second end-edge such that the profiles fit together.3014. A belt according to any of claims 5-13, wherein the common tooth extendsperpendicularly to the longitudinal axis.

15. A belt according to any of claims 5-14, the common tooth is obliquely angled with respect to the longitudinal axis and / or the orientation of the interface.

16. A timing belt according to an of claims 5-15, wherein the common tooth5 intersects the interface a plurality of times across a width dimension of the belt.

17. A belt according to any of previous claim 5-16, wherein the plurality of teeth are spaced at a regular spacing along the belt in the longitudinal direction and the common tooth is spaced from adjacent teeth by said regular spacing.1018. A belt according to any of claims 5-17, wherein the common tooth has a cross-sectional profile that tapers or narrows between the surface of the belt and the tip of the tooth.15 19. A belt according to any of claims 5 to 18, wherein the common tooth fullyextends over the interface between the first and second lateral edges such that the interface is obscured from view on the major surface of the belt on which the common tooth is located.20 20. A belt according to any one of claims 5 to 18, the common tooth is notcontinuous between the first and second lateral edges.

21. A belt according to any of claims 5-20, the tooth having one or more side walls extending away from a major surface of the belt, where the side wall25 intersects with the interface.

22. A belt according to claim 21, wherein the side wall of the common tooth intersects with the interface a plurality of times.30 23. A belt according to any of claims 5-22, wherein the interface extends adistance in the longitudinal direction, the belt comprising a plurality of common teeth spaced apart in the longitudinal direction.LO CXI24. A belt according to any of claims 5-23, the plurality of teeth not located at the interface defining non-common teeth, the common tooth having a profile that is the same as the non-common teeth.5 25. A belt according to any of previous claims 5-24, wherein the belt orcommon tooth comprises reinforcement fibres or wires therein.A

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