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.
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.
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.
In the following, example embodiments are described according to the invention, where
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.
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
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.
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
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.
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/057724 | 3/31/2017 | WO | 00 |