Patent Publication Number: US-2021162565-A1

Title: Improved abrading wheel

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a § 371 national stage entry of International Application No. PCT/EP2017/057724, filed on Mar. 31, 2017, and entitled “IMPROVED BRADING WHEEL.” The content of this applications is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to abrading wheels. More specifically, the present invention relates to abrading wheels for grinding a product or finishing a surface of a rubber product to form a desired surface smoothness. 
     BACKGROUND OF THE INVENTION 
     Usually, abrading wheels are characterised by their ability to grind products or to tear products apart. For example, such products may be rubber tires or the like, where there is a desire to refurbish or recycle material. A use situation usually involves rotating the abrading wheel at high speed and applying the product to be grinded onto grit disposed onto an outer surface of the abrading wheel. Thereby, the part of the product in contact with the abrading wheel is disintegrated, and the abrading wheel may either be used to smoothen the surface of the remaining part of the product, or the abrading wheel may be used to disintegrate the entire product. However, during such use, several problems are known to occur. The particles from the product being grinded may quickly accumulate in the grit, thereby leaving the abrading wheel useless. In other words, the abrading surface will turn into a smooth surface over time due to the accumulation of particles in the grit. Further, the grit, and the surface onto which said grit is disposed, may heat up due to friction between the abrading wheel and the product being grinded. For example, the products being grinded may behave differently at elevated temperatures or the abrading wheel may attain temperatures exceeding what is considered safe. 
     US2002/035890A1 discloses a metal bonded drilling tool which is improved in grinding performance with a long life and can drill a hole in a dry condition without the need for water. The metal bonded drilling tool includes a cylindrical body having an open front end portion, a shank integral with the cylindrical body and having a threaded hole for use in mounting the tool to a rotary tool, and numerous abrasive grains bonded to a front edge of the cylindrical body and to inner and outer cylindrical surfaces of the front end portion of the cylindrical body by a bond member formed primarily of copper alloy. 
     GENERAL DESCRIPTION 
     The object of the invention is to solve some of the above-mentioned problems. This is realised by an abrading wheel comprising a circular core having an outer periphery, a rim arranged orthogonally to said circular core on said outer periphery, said rim comprising an inner surface and an outer surface, and a grit material disposed on at least part of said outer surface, and where a plurality of openings are arranged in said core for providing an airflow directed towards said inner surface, and wherein the outer surface of said rim is provided with a plurality of grooves, and where a main part of said grit material is disposed on said outer surface of said rim on spaces between said grooves. 
     By a circular core is meant a unitary, solid, continuous core of metal. Preferably, the circular core is made from steel. Preferably, the core has a thickness ensuring stability when rotating the abrading wheel at operation speeds. The thickness should correspond to the diameter and use of the tool, but may be from 2 to 6 mm. The diameter of the circular core may be between 50 mm and 300 mm, depending on use. An outer periphery is inevitably a part of a circular core as defined. By a rim is meant a ribbon-shaped metal comprising a width greater than the thickness of the circular core and a length equal to the circumference of the outer periphery of said circular core. The width of the rim defines the working width of the abrading wheel. The width of the rim may vary according to the use, but may be at least 20 mm or may be at least 200 mm. However, it should be noted that the width and in fact the entire abrading wheel may be scaled according to the desired use. The rim is mounted along an edge to the outer periphery. Thus, the rim is a circular element mounted onto said outer periphery. By a grit material is meant a material preferably having a hardness substantially higher than the product which the abrading wheel is meant to grind. The grit material constitutes grit. The grit material may be tungsten carbide. The grit material may be formed as small grains comprising a plurality of sharp spikes, or it may be other structures comprising sharp edges capable of grinding products. 
     Thereby, the abrading wheel is cooled during operation, heat is more easily dissipated, and accumulation of particles from the product being grinded is minimised. Due to the plurality of openings in the circular core, air is forced onto the inner surface of the rim thereby providing air cooling. Due to the presence of grooves on the outer surface, the surface area of said outer surface is inevitably increased thereby increasing the dissipation of heat and providing additional cooling to the abrading wheel. By disposing a main part of the grit material on spaces between the grooves, said grooves are kept free of grit material thereby minimising the risk of accumulation of material or particles in said grooves. The combination of cooling the abrading wheel and reducing the risk of accumulation of particles further increases the lifetime of said abrading wheel. 
     In an embodiment, the circular core may comprise a central axis and a central aperture for mounting the abrading wheel on a rotation tool. 
     By a central axis is meant an axis arranged orthogonally to the plane, wherein the outer periphery lies, and where said axis is arranged in the centre of the circular core. Thereby, the central axis is positioned equidistant from the outer periphery of the circular core. By a central aperture is meant a through-going opening arranged in the centre of the circular core. Preferably, the central aperture is arranged in a displaced depression, said depression being an integral part of the circular core. Preferably, the depression is displaced such that the central aperture is positioned in a position providing the highest amount of stability to the abrading wheel when said abrading wheel is rotating at operational speeds. Such position may be in a central position of the abrading wheel when considering the abrading wheel as a whole, i.e. centrally to the circular hub and midway of the width of the rim. 
     Thereby, the abrading wheel may be mounted on a rotation tool and set into rotation around the central axis. The central aperture may have a shape corresponding to a shape of the rotation tool, such that rotation is secure and efficient. Preferably, the central aperture comprises at least one indentation for engaging with a corresponding protrusion on the rotation tool, such that the abrading wheel is fastened securely. 
     In an embodiment, the cross section of the grooves may be V-shaped. 
     Thereby, the grooves extend into the outer surface of the rim. By the cross section of the grooves being V-shaped, particles are less likely to accumulate in the grooves, since the surface area in the vicinity of the vertex of the groove is minimised compared to other shapes, such as U-shaped grooves. 
     In an embodiment, the plurality of grooves may be arranged in a helix having an axis collinear and coinciding with the central axis. 
     In an embodiment, the plurality of grooves may be tilted relative to an edge of the rim. 
     By an axis of the helix being collinear and coinciding with the central axis, said axes are indistinguishable. Thereby, the grooves are oblique to a normal cutting angle between the product to be grinded and the outer surface of the rim. A normal cutting angle may be defined as the cutting angle, wherein the product to be grinded is applied orthogonally to the outer surface of the rim. That means normal incident of the product to be grinded onto the outer surface of the rim. An oblique cutting angle is efficiently realised when the grooves, and the accompanying intermediate spaces between said grooves, are arranged in a helix-shaped pattern along the circumference of the rim. Alternatively, the grooves may be tilted relative to an edge of the rim, said edge being collinear with the outer periphery of the central core. Thus, when applying said product orthogonally to the outer surface of the rim, a larger amount of grit material disposed on the spaces between the grooves makes impact onto the product to be grinded. In other words, the plurality of grooves arranged in a helix provide clearance for a majority of the grit, i.e. a majority of the grit is arranged aggressively relative to the product to be grinded, such that the efficiency of the grinding process in increased. By being arranged aggressively is meant that shadowing of grains of the grit material is minimised with respect to subsequent grains when the abrading wheel is rotating. In other words, an increased free space is provided for the grit material to come into contact with the product to be grinded. Further, the arrangement of the grooves along the direction of rotation provides an enhanced free flow of particles, such that accumulation in the grit of said particles originating from the product being grinded is minimised. Said free flow of particles causes said particles to be guided away from the abrading wheel along the grooves. In other words, the particles formed from the grinding process are guided in a route given by the arrangement of the grooves, and where said arrangement of grooves are in a helix, the route leads the particles out of the abrading wheel. Thereby, the abrading wheel has an inherent self-clearing effect. In combination with the aggressively arranged grit due to the helix or tilt arrangement, the abrading wheel experiences an increased lifetime. 
     In an embodiment, the plurality of grooves may be arranged parallel to each other and parallel to the outer periphery of the circular core. 
     By being arranged parallel to each other and parallel to the outer periphery of the circular core, the grooves are arranged orthogonally to the central axis of the abrading wheel, i.e. the central axis of rotation. In such an arrangement, grains of the grit material disposed on spaces between the grooves may be said to shadow subsequent grains of same grit material, i.e. the grinding efficiency of the abrading wheel is lowered which may be desired in certain use. 
     Thereby, the resistance between the grit and product to be grinded is reduced. That means that due to the grooves and accompanying spaces with grit material being aligned to the normal cutting angle, a smaller amount of grit material is exposed to the product to be grinded at a given time. Thus, the resistance is reduced which may be useful for certain products or situations. 
     In an embodiment, the rim may be a ribbon mounted onto the outer periphery of the circular core along an edge of said ribbon. 
     By a ribbon is meant a primarily rectangular piece of material bent to fit the outer periphery of the circular core. Thus, the ribbon comprises two side edges and two end edges, said end edges being joined to form a circular ribbon. One of said side edges are mounted on the outer periphery of the circular core, such that the abrading wheel resembles a bowl. 
     Thereby, the thickness of the circular core may be smaller than the width of the rim, such that the inner surface of the rim is exposed to air. It is noted that the mounting may be through welding, or the mounting may be through means of pressing, stamping, or casting the abrading wheel in a single piece. 
     In an embodiment, a tongue may be attached to each opening of the circular core, a plurality of tongues thereby being arranged in said circular core. 
     In an embodiment, the tongues may be formed from excess material bent away from the opening, the tongues thereby being an integral part of the circular core. 
     In an embodiment, the tongues are oriented such that air is forced onto the inner surface of the rim, thereby providing air cooling to the abrading wheel. 
     By a tongue is meant a partially free piece of material freed from the circular core. Thus, a tongue and an opening may be formed simultaneously by making appropriate cuts in the circular core, followed by bending an uncut edge away from the plane of the circular core. Thereby, the tongue is attached to the circular core through the bow and may therefore be considered an integral part of the circular core. Thus, the openings may be said to comprise integrated tongues. The tongues may be said to be cooling tongues. The tongues may be regarded as wings. Preferably, the plurality of tongues are bent towards an inner volume partly defined by the inner surface of the rim and the circular core. Preferably, the tongues are arranged in a homogenous pattern, such that the tongues are positioned identically relative to the opening for all openings provided in the circular core. Preferably, the openings are quasi-quadratic and the uncut edge is oriented orthogonally to the outer periphery of the circular hub. 
     Thereby, passive means for guiding an air flow onto the inner surface of the rim is realised. By passive means is meant that said air flow is pulled into the abrading wheel and guided onto the inner surface of the rim by the combination of high rotation speed of the abrading wheel and the orientation of the tongues. Said orientation of the tongues is chosen to maximise the air flow onto the inner surface of rim during high speed rotation of the abrading wheel. Thereby, the passive means for guiding an air flow onto the inner surface of the rim provides passive cooling means of the abrading wheel. Thereby, said passive cooling means causes a lower working temperature of the abrading wheel. 
     In an embodiment, the grit material may form an overhang above said grooves. 
     By an overhang is meant that free space is provided between the outer surface of the rim and parts of the grit material disposed primarily on the spaces between the grooves. 
     Thereby, the combined surface area of grit material exposed to the surroundings is increased compared to a situation where no overhang is provided. Thus, when using the abrading wheel for grinding a product, a larger part of said product may be in contact with the grit thereby increasing the efficiency of the abrading wheel. Further, the amount of grit may be increased by allowing an overhang while maintaining the presence of grit-free grooves for avoiding accumulation of particles as described earlier. Moreover, an increased surface area of grit material results in an increased amount of heat dissipation thereby increasing the cooling abilities of the abrading wheel. 
     In an embodiment, the grit material may be tungsten carbide. 
     Thereby, the grit material has a hardness superior to most materials which it is expected to grind. Materials possessing similar hardness, such as silicon carbide, are foreseen within the scope of the invention. 
     In an embodiment, the grit size may be between 14 and 220. 
     The grit size disclosed is standardised according to Federation of European Producers of Abrasives (FEPA). A grit size of  14  corresponds to a particle size (mean diameter) of 1.47 mm, and a grit size of 220 corresponds a particle size (mean diameter) of 0.058 mm. 
     Thereby, the grit may be varied according to use and the desired smoothness of the grinded product. 
     In an embodiment, the abrading wheel may be mounted onto a rotation tool, said rotation tool being capable of providing rotation around a central axis of the abrading wheel. 
     Preferably, the mounting is done by engaging a rotational part of the rotation tool in the central aperture and the indentation, where said central aperture and indentation corresponds to the dimension of the rotational tool and a protrusion in said rotational part, respectively. Thereby, the abrading wheel may be set in an efficient and secure rotation. 
    
    
     
       SHORT LIST OF THE DRAWINGS 
       In the following, example embodiments are described according to the invention, where 
         FIG. 1  illustrates a perspective view of an abrading wheel according to the invention. 
         FIG. 2  illustrates a second perspective view of an abrading wheel according to the invention. 
         FIG. 3  illustrates a top view of an abrading wheel according to the invention. 
         FIG. 4  illustrates a plurality of cross-sectional views of an abrading wheel according to the invention. 
         FIG. 5  illustrates an example of an outer surface of an abrading wheel according to the invention. 
         FIG. 6  illustrates a second example of an outer surface of an abrading wheel according to the invention. 
         FIG. 7  illustrates a close up cross-sectional view of a groove in an outer surface on an abrading wheel according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF DRAWINGS 
     In the following, the invention is described in detail through embodiments thereof that should not be thought of as limiting to the scope of the invention. 
       FIG. 1  is a perspective view of a part of an abrading wheel  100  according to the invention. The abrading wheel  100  comprises a circular core  101  having an outer periphery  103  and a central aperture  105 . Said central aperture  105  is arranged in a depression  109 . Said depression  109  protrudes into an inner volume (not shown) partly defined by said circular core  101  and a rim  111  arranged orthogonally to said core  101  on said outer periphery  103 . Thus, the abrading wheel  100  may be said to be bowl-shaped with a central depression  109 . Preferably, the depression  109  is an integral part of the core  101  therefore being considered as part of the core  101  in this context. Preferably, the central aperture  105  comprises at least one indentation  107  for mounting the abrading wheel  100  securely onto a rotation tool (not shown). The indentation  107  may be formed to correspond to a protrusion on said rotation tool (not shown). Said rotation tool may be used to rotate the abrading wheel  100  around a central axis L by engaging with the central aperture  105  and the at least one indentation  107 . The rim  111  may be either mounted through e.g. welding onto the outer periphery  103  of the core  101 , or the combined rim  111  and core  101  may be formed from a single piece of material, such that the outer periphery  103  is formed when bending/stamping said single piece of material. Alternatively, the core  101  and rim  111  are formed in a casting process. The core  101  is equipped with a plurality of openings  121 . Preferably, said openings  121  are arranged equiangularly in a circular pattern at a fixed distance from a centre point of the central opening  105 . The openings  121  are equipped with tongues  123 , said tongues  123  preferably being an integral part of the core  101  and formed from bending the material along an uncut edge  124 . For example, the openings  121  may be rectangular, such that the tongues  123  are formed from cutting along three edges thus leaving a fourth edge uncut and thereby allowing said fourth edge to be bent. Preferably, the tongues  123  are bent towards the inner volume (not shown). Preferably, the tongues  123  are bent evenly for all openings  121 , such that a homogenous pattern of the openings  121  and tongues  123  is formed. When the abrading wheel  100  is set into rotation by a rotation tool, the tongues and accompanying openings draw in an air flow, such that said air is forced onto an inner surface (not shown) of the rim  111 . Thereby, said air flow provides air cooling of the abrading wheel. Air cooling is essential when using the abrading wheel  100  for grinding purposes, where heating may occur due to friction. 
     The rim  111  is arranged orthogonally to the plane of the core  101 , i.e. the rim extends in a direction parallel to the central axis L. The rim comprises an outer surface  113  and an inner surface (not shown). The inner surface is oriented towards the inner volume (not shown) of the abrading wheel  100  partly defined by the core  101  and the rim  111 . The outer surface  113  comprises a plurality of grooves  131 , for example carved into said outer surface. Said plurality of grooves  131  twists around the central axis L. Preferably, the grooves  131  are arranged in a helix with an axis collinear and coinciding with the central axis L. The helix and the grooves  131  sketched in  FIG. 1  are highly exaggerated. Alternatively, the grooves  131  are parallel to each other and to the outer periphery  103  of the core  101 . Alternatively, the grooves  131  are tilted relative to the outer periphery  103 . Between said grooves  131 , intermediate protruding spaces  132  are formed, said spaces  132  inevitably having the same course, e.g. a helix, as the grooves  131 . A grit material  141  is disposed primarily onto said spaces  132  thereby leaving the grooves  131  free of grit material  141 . See  FIG. 5 a    and  FIG. 6 a    for a cross-sectional view of the grooves  131 , the spaces  132  and the disposed grit material  141 . Said grit material  141  is made from a hard material such as tungsten carbide having a hardness of 9 on the Mohs-scale. When the abrading wheel  100  is set into rotation and a product is applied onto the grit, the grit material  141  grinds said product. Due to the absence of grit material  141  in the grooves  131 , particles grinded off the applied product are less likely to accumulate in the grooves thereby increasing the lifetime of the abrading wheel  100 . In other words, particles entering the grooves  131  are free to move and eventually escape said grooves  131 , contrary to the case wherein grit material  141  would be disposed in the grooves  131 , whereby particles would get trapped and accumulate more easily. 
     By arranging the grooves  131  and accompanying intermediate spaces  132  in a helix or tilted relative to the outer periphery  103 , a larger amount of grit material  141  makes contact with the product to be grinded at any given time during rotation of the abrading wheel  100 , assuming the product makes normal incident onto the rim  111 . In other words, the helix arranged or tilted grooves  131  and spaces  132  provide an increased free space for a product making contact to the grit material  132  disposed in the spaces  132 . Thus, by the grooves  131  and accompanying spaces  132  being tilted or arranged in a helix, the grinding efficiency of the abrading wheel  100  is increased. 
     A further effect of the grooves  131  and the accompanying intermediate spaces  132  being arranged in a helix or tilted relative to the outer periphery  103  is that the particles formed by grinding a product on the abrading wheel  100  are guided out of the abrading wheel. In other words, grooves  131  arranged in a helix or tilted inevitably comprise ends  133  terminating along an edge of the rim  111 , where said ends  133  allow the particles to escape the abrading wheel  100 . 
     The presence of grooves  131  further increases the surface area of the abrading wheel  100  which in turn increases the dissipation of heat and thereby increases the cooling capabilities of said abrading wheel  100 . 
       FIG. 2  is a perspective view of the part of the abrading wheel  100  of  FIG. 1  shown from another angle. In this view, the inner volume partly defined by the core  101  and the rim  111  is exposed. The inner surface  115  of the rim is shown in this view. The depression  109  protrudes into said inner volume. The central aperture  105  and the indentation  107  are partly visible. The tongues  123  are shown to be bent into the inner volume along an uncut edge  124 . Further, the openings  121  are shown to be cut along three edges  221 ,  222 ,  223 , thereby leaving the uncut edge  124  uncut. The tongues  123  are all bent along the same uncut edge  124  relative to the core  101  thereby forming a homogenous pattern along the entire diameter along which the openings  121  are arranged. Preferably, the uncut edge  124  is orthogonal to the rim  111 . A grit material  141  is disposed on spaces between a plurality of grooves (not shown in this embodiment) on the outer surface  113  of the rim  111 . The grit material  141  is shown in further detail in  FIG. 5  and  FIG. 6 . 
       FIG. 3  shows a top view of the abrading wheel  100 . The top view exposes the inner volume. The direction of the central axis L serves as reference to  FIG. 1 . The plurality of openings  121  is shown without tongues  123 . However, it should be noted that in the case of said tongues  123  being an integral part of the core  101 , it is not optional to detach or attach said tongues  123 . The plurality of openings  121  is shown to be equiangularly spaced on the core  101  around the central axis L. The central aperture  105  is shown to be arranged symmetrically around the central axis L. The abrading wheel  100  is shown with two indentations  107 ,  107 ′, for improved stability when mounting the abrading wheel onto a rotation tool (not shown). The depression  109  is indicated by a dotted line. The grit material  141  is shown disposed on an outer surface  113  of the rim  111 . Three cross sections, A-A, B-B, and C-C, are indicated in  FIG. 4  and described in further detail below. 
       FIG. 4  shows the cross sections indicated in  FIG. 3 . 
       FIG. 4 a    illustrates the cross section A-A comprising two of the plurality of openings  121 . The tongues  123  are shown to be an integral part of the core  101  and being bent along an uncut edge  124  indicated by a dotted line. 
       FIG. 4 b    illustrates the cross section B-B. The tongue  123  attached to the opening  121  is shown as a displaced dotted box due to the choice of viewing angle. The rim  111  is shown being arranged orthogonally to the core  101 . An edge of the rim  101  is shown to be mounted onto the outer periphery  103  of the core  101 , the rim  111  thereby forming an acute angle of 90 degrees and an obtuse angle of 270 degrees relative to the core  101 . The rim  111  comprises a plurality of grooves  131  arranged in the outer surface  113 . The plurality of grooves  131  are separated by a plurality of spaces  132 . A grit material  141  is disposed onto said spaces  132 . 
       FIG. 4 c    illustrates the cross section C-C. The abrading wheel is rotationally symmetric around the central axis L. The direction of the central axis L corresponds to the direction given from  FIG. 1 . The depression  109  protrudes towards the inner volume partly formed by the core  101  and the rim  111 . More specifically, the depression  109  displaces the central aperture  105  towards a midway point defined from the width of the rim  111 . Thereby, stability of the abrading wheel  100  is increased when said abrading wheel  101  is exposed to rotational forces. 
       FIG. 5  and  FIG. 6  show two possible excerpts of the outer surface  113 . For reference, the orientation of the excerpts relative to the rim  111  is indicated by the directions x and z which are further defined in  FIG. 1 . A cross view of each excerpt is shown in  FIG. 5 a    and  FIG. 6 a   . The excerpts are examples of possible arrangements of the grooves  131  and accompanying spaces  132  thereby not limiting the scope of the invention. 
       FIG. 5  illustrates an excerpt of an outer surface  113  comprising a large separation of grooves  131 , i.e. large spaces  132 . Further, the grooves  131  and the accompanying spaces  132  are tilted at an angle  1  relative to the x-direction. The tilt forms a helix along the circumference of the rim  111  and around an axis coinciding with the central axis L (not shown). The grit material  141  is disposed on the spaces  132 , such that the grooves  131  are free of grit material  141 . A shaded triangle indicates a possible impact area  150  for a product to be grinded by the abrading wheel  100 . During rotation, a product making normal incident, i.e. “entering” the grit from the short cathetus  150   a , as shown by the direction of the arrow E, makes impact with the grit material  141  along the entire length of the hypotenuse  150   c . In the case of non-tilted grooves  131  and spaces  132 , the impact would be reduced to the width of the spaces  132  onto which the grit material  141  is disposed. Thereby, said impact area  150  illustrates the increased efficiency of the abrading wheel  100 , when the grooves  131  and accompanying spaces  132  are arranged in a helix or tilted. 
       FIG. 5 a    illustrates a cross-sectional view of the excerpt in  FIG. 5 . Preferably, the grooves  131  are V-shaped as illustrated. Preferably, the grit material  141  overhangs parts of the grooves  131  illustrated by the overhang  142 . 
       FIG. 6  and  FIG. 6 a    (cross-sectional view) illustrate an excerpt of an outer surface  113  comprising a small separation of grooves  131 , i.e. narrow spaces  132 . Further, the tilt given by the angle  1  is smaller than the excerpt illustrated in  FIG. 5 . 
       FIG. 7  illustrates a close-up cross-sectional view of a V-shaped groove  131  and grit material  141  disposed primarily on intermediate spaces  132  between said grooves  131 . It is noted how an overhang  142  of grit material  141  is formed, such that free space is provided between the slopes of the groove and said grit material  141 . 
     REFERENCE NUMBERS 
     E Entering direction of product 
     L Central axis 
       1  Angle relative to x-direction 
       100  Abrading wheel 
       101  Circular core 
       103  Outer periphery 
       105  Central aperture 
       107  Indentation 
       109  Depression 
       111  Rim 
       113  Outer surface 
       115  Inner surface 
       121  Openings 
       123  Tongues 
       124  Uncut edge 
       131  Grooves 
       132  Spaces 
       133  End of groove  131   
       141  Grit material 
       142  Overhang 
       150  Impact area 
       150   a  Cathetus 
       150   c  Hypotenuse 
       221  Edge 
       222  Edge 
       223  Edge