Patent Application
20240261940
The present disclosure relates to a grinding tool which can be driven in rotation about an axis of rotation and comprises an abrasive band, the abrasive band being wound in a spiral around the axis of rotation with a plurality of superimposed layers and having a grinding layer on a band side facing away from the axis of rotation. Furthermore, the present disclosure relates to a method of manufacturing such a grinding tool.
U.S. Pat. No. 4,625,466 A discloses a grinding disk having an abrasive band wound about an axis of rotation. The abrasive band has a radially outward facing grinding layer and a foam layer radially on the inside. The grinding layer extends parallel to the axis of rotation. Furthermore, the grinding disk has a supporting plate to which the abrasive band is fastened with its circumferential edge aligned axially to the axis of rotation.
U.S. Pat. No. 2,725,693 A discloses an abrasive roll made from a strip of emery cloth rolled into a cylindrical shape around a small central mandrel, the abrasive roll being held together by a layer of adhesive extending along at least part of the length of the abrasive roll. The strip of emery cloth is rectangular in shape and is wound into a cylinder with the emery surface facing outward. A circular groove is provided in the abrasive roll, extending externally around the circumference of the abrasive roll and depressed inward toward the central mandrel.
DE 37 17 204 A1 describes an axially compressed circular disk-shaped layered body consisting of intermeshing fiber material and made of metal fibers. The layers are spirally wound layers of fiber strands.
One aspect is to provide a grinding tool with which a uniform grinding pattern can be achieved on the workpiece to be machined during a grinding process. A further aspect is to provide a method of manufacturing such a grinding tool, with which a uniform grinding pattern can be achieved on the workpiece to be machined during a grinding process.
As a solution, a grinding tool of the type mentioned above is proposed, in which the wound-up abrasive band is convexly curved in a longitudinal section along the axis of rotation with respect to the axis of rotation and the layers of the abrasive band reach radially into one another.
The terms “radial” and “axial” are used as abbreviations for “radial with respect to the axis of rotation” and “axial with respect to the axis of rotation”, respectively.
It is advantageous that the grinding tool continuously exposes fresh abrasive to the working surface on the workpiece to be machined. The abrasive band is consumed in the grinding process, as during use the individual layers of the abrasive band degrade from radially outward to radially inward, causing the outer diameter of the grinding tool to become smaller and smaller. Due to the radial engaging of the layers of the abrasive band, however, at least a partial area of the abrasive surface of the wound abrasive band extending over the layers is always exposed on an outer circumferential surface of the winding. This creates a reproducible, uniform surface on the workpiece over and over again. Due to the grinding surface facing away from the axis of rotation, the rotationally drivable grinding tool can be applied to the workpiece to be machined with the outer circumferential surface of the grinding tool, in particular with the winding. The grinding tool is thus particularly suitable for machining weld seams and fillet welds as well as joints.
Each of the layers is formed by a longitudinal band section of the abrasive band, each of which extends over one of the turns of the wound abrasive band. Preferably, the abrasive band is a self-contained continuous band material that can extend over all layers of the winding. In particular, all layers of the abrasive band are on top of each other; the abrasive band is virtually rolled up. A first layer begins at a first, radially outer end of the abrasive band and ends accordingly with a first winding around the axis of rotation. The last layer ends with a second, radially inner end of the abrasive band. Since the outer circumferential radius of the winding becomes smaller with each radially more inner layer, the longitudinal band sections of the abrasive band also become correspondingly shorter with each layer. Preferably, the abrasive band is wound around the axis of rotation with at least two and, in a further preferred manner, with at least ten layers. In particular, the winding has at least two and at most 150 of the layers of the abrasive band. Preferably, the winding has at least 3 and at most 50 layers of the abrasive band and further preferably at least 5 and at most 30 layers of the abrasive band. The winding can be designed without a carrier, whereby the second, radially inner end of the abrasive band can end at the axis of rotation or in the center of the winding. Alternatively, the winding can end at an inner circumferential circle so that the winding can have a central, axially extending recess into which a shaft for connecting the grinding tool to a rotary drive machine or a supporting body for stabilizing and/or connecting the grinding tool to a rotary drive machine can be inserted or fitted. The winding, respectively the wound abrasive band forms a grinding section of the grinding tool.
Due to its convex bulged design, the abrasive band has a profile geometry that is open to the axis of rotation. The profile geometry preferably refers to the geometry resulting from a longitudinal section through the abrasive band along the axis of rotation. In particular, the profile geometry has a U-shape and/or a V-shape at least partially along a band length of the abrasive band. The band length of the abrasive band corresponds to the extension of the abrasive band over all layers or the distance between the two ends of the abrasive band in the unwound state. The profile geometry can also be at least partially L-shaped and/or W-shaped and/or C-shaped. The profiling of the abrasive band can be produced, for example, by forming a band-shaped primary material. The primary material can be a flat abrasive, for example an abrasive material on a backing. In principle, the abrasive band to be wound up can also be provided already preformed accordingly. In particular, the radially further inward layers of the abrasive band can have the V-shaped profile geometry, whereby with each radially further outward layer the profile geometry can change into a U-shape, in particular continuously. It is advantageous that the outermost layer is U-shaped and the grinding layer of the outermost layer thus forms a round, outwardly curved grinding-effective circumferential surface of the grinding tool.
Furthermore, it can be provided that a, with respect to the axis of rotation, radially inner layer of the abrasive band is axially covered partially by an adjacent radially outer layer of the abrasive band. Due to this form of interleaving of the individual layers of the abrasive band, as soon as the outermost layer has been worked off at least partially, several of the layers of the abrasive band are always exposed at the outer circumferential surface of the grinding tool, at least in some areas. This ensures a consistent grinding pattern during the grinding process.
Further, the grinding tool may have a first main tool side and a second main tool side facing away from the first main tool side. The abrasive band can be arranged axially between the first main tool side and the second main tool side with respect to the axis of rotation. The second main tool side can be a rear side, or a side of the grinding tool facing the drive machine. In principle, however, it is also conceivable and possible that the grinding tool is clamped onto the spindle of the drive machine with the first main tool side facing the drive machine.
The grinding tool may have at least one stabilizing layer. This can improve the stability of the grinding tool and especially the grinding section. Furthermore, the at least one stabilizing layer can provide side or flank protection to prevent accidental scratching of the workpiece being machined. In particular, the grinding tool can be covered on its first main tool side and/or the second main tool side at least partially by one of the at least one stabilizing layers, respectively. The abrasive band may be attached to the at least one stabilizing layer. This fixes the wound abrasive band in place in a simple manner, preventing unintentional winding or unwinding during stor-age of the grinding tool or during the grinding process. The at least one stabilizing layer can have a maximum layer thickness of 2 millimeters and/or a minimum of 0.4 millimeters. As a result, the at least one stabilizing layer can, on the one hand, provide sufficiently stable support for the abrasive band and, on the other hand, continuously degrade together with the abrasive band during the grinding process. Preferably, the layer thickness is less than 1.5 millimeters and, in a further preferred manner, can be between 1.0 millimeters and 0.6 millimeters.
According to one embodiment, the grinding tool may have two of the stabilizing layers, with the first stabilizing layer facing the first main tool side and the second stabilizing layer facing the second main tool side of the grinding tool. The axial fixation of the abrasive band on both sides provides a particularly stable grinding tool. In a manner known per se, labels or the like can be applied to the main tool sides of the grinding tool, but these labels or the like themselves have no influence on the grinding properties or the durability of the grinding tool.
In particular, the at least one stabilizing layer is a self-contained layer that can be inherently stable. Expediently, the at least one stabilizing layer can degrade along with the wound abrasive band during use of the grinding tool. The at least one stabilizing layer can overlap the abrasive band axially, or extend over the grinding section of the grinding tool. A peripheral edge of the abrasive band facing the at least one stabilizing layer may be bonded to the at least one stabilizing layer. The respective circumferential edge is formed at one axial end of the wound abrasive band and follows the course of a spiral due to the winding of the abrasive band. In this way, the abrasive band can be fixed at at least one of the two open axial ends. An advantage is that the at least one stabilizing layer also allows the use of a particularly thin abrasive band, which would tear during the grinding process without such lateral stabilization. Such a thin abrasive band may, for example, have a backing of paper on which abrasive grains are applied.
Furthermore, the at least one stabilizing layer may have a binder which extends in an edge region of the abrasive band facing the respective stabilizing layer into intermediate spaces formed between the layers of the abrasive band. The fact that the side of the band facing away from the axis of rotation has the grinding layer, which can have a rough surface, and the side of the band facing the axis of rotation can have a flat, smoother surface, means that the intermediate spaces are formed between the adjacent layers into which the binder can penetrate when the grinding tool is manufactured. Preferably, the at least one edge region of the abrasive band provided with the binder extends over as small a proportion as possible of the axial extent of the abrasive band in order to keep the grinding layer free over as large an area as possible. This is because the binder can stick to the edge region of the grinding layer, which can locally impair the removal rate of the abrasive band. The advantage of this is that the at least one edge region has no or hardly any grinding effect and thus prevents scratching of the workpiece in the event of unintentional contact of the grinding tool with the respective main tool side on the workpiece to be machined. The at least one stabilizing layer can thus have a dual function, increasing the stability of the abrasive band on the one hand and providing side or flank protection on the other. In particular, the axial extent of the respective edge region is less than 20 percent of the width, i.e. the axial extent of the abrasive band, and further preferably less than 10 percent of the width, i.e. the axial extent of the abrasive band, and even further preferably less than 5 percent of the width, i.e. the axial extent of the abrasive band.
In a preferred manner, the layers are at least partially unconnected to each other. In other words, the layers are not glued together, at least partially, and lie loosely against each other. This produces a consistently reproducible, uniform surface on the workpiece and improves the removal rate of the grinding tool. If the abrasive band is attached to the at least one stabilizing layer, the unattached portion may be a central grinding region of the abrasive band that may be axially adjacent to the at least one edge region provided with the binder. If the abrasive band is fixed on both sides, the central grinding region can be formed accordingly between the two edge regions. Preferably, the central grinding region of the abrasive band extends over at least 60 percent of the axial extent of the abrasive band and, in a further preferred manner, may be between 70 percent and 90 percent. In a convenient manner, the central grinding region of the outermost layer is located in the peripheral surface of the grinding tool. As the grinding tool wears, the circumferential surface shifts radially inward. Thus, the grinding tool can grind the workpiece to be machined with the outer peripheral surface of the grinding tool. This makes the grinding tool particularly suitable for machining weld seams and fillet welds as well as joints.
The binder can be a resin or adhesive. The binder in the grinding tool may have cured. It is advantageous if the binder is thermally stable in the cured state to withstand the temperatures generated during grinding. In particular, the binder may be a thermoset. In particular, a phenolic resin may be provided as a binder, although another resin or bonding system may also be used, such as, in particular, epoxy resin, polylactide, also called polylactic acid, and lactates thereof, polyurethanes and mix-tures thereof. Furthermore, the binder can also be or comprise polymer foam.
The at least one stabilizing layer may comprise reinforcing interlinings, which may be provided with or embedded in the binder. The reinforcing interlining may comprise fabric and may be, for example, a glass fabric or other mineral fiber fabric, a natural fiber fabric, a metallic fabric such as a wire fabric, or the like, or combinations thereof. Several of the reinforcing interlinings can also be arranged one on top of the other in the at least one stabilizing layer to adjust the stability. Instead of the fabric, scrims, knitted fabrics, nonwovens, paper, vulcanized fiber, plastic disks or other reinforcing materials can also be provided, which fulfill the function of stabilizing, fixing and/or reinforcing the grinding tool, in particular the wound abrasive band. This can also be done, for example, by (individual) fibers that may be added to the binder.
Furthermore, the binder of the at least one stabilizing layer can be mixed with fillers. The fillers may include, for example, quartz flour, amorphous silica, rutile or the like. In particular, the fillers are abrasive and may include fluorides such as KBF4 or cryolite, or substances that are otherwise beneficial to the grinding process, such as lubricants or anti-stick agents that reduce clogging of the grinding tool in the grinding process.
Further, the at least one stabilizing layer may comprise or serve as a support for an abrasive. This allows the grinding tool to be designed for diverse requirements. For example, the at least one stabilizing layer may comprise an abrasive disk that may have a fabric backing. The abrasive disk can be a cut-off wheel, grinding disk or the like, or a bonded abrasive. The at least one stabilizing layer can be a support for another grinding disk, in particular a lamellar grinding disk or another of the aforementioned abrasive disks.
The grinding tool may have a central support section that may connect radially in-wardly to the grinding section. The wound abrasive band can be arranged in the circumferential direction around the axis of rotation around the support section. Preferably, the grinding section corresponds at least substantially to an annular section formed concentrically about the axis of rotation and having an inner diameter and an outer diameter. Preferably, the outer diameter of the grinding section corresponds to the outer diameter of the grinding tool, which lies in the circumferential surface of the grinding tool. In particular, the inner diameter of the grinding section corresponds to at least two-thirds of the outer diameter of the grinding tool, and further preferably corresponds to at least about five-sixths of the outer diameter of the grinding tool. This allows higher peripheral speeds to be achieved during grinding. In addition, the grinding section is designed to be radially far enough outward so that even when the radially innermost layers of the abrasive band are being worn down, the rotary drive machine does not interfere with or hit the workpiece during the grinding process.
The grinding tool can have a central supporting body, in particular concentric with the axis of rotation, around which the abrasive band is arranged. In particular, the supporting body can radially engage the profile of the radially innermost layer of the abrasive band, which is open to the axis of rotation. This increases the stability of the grinding tool. The greater the axial extension of the abrasive band, the deeper the supporting body can be inserted or arranged in the grinding section or the profile of the radially innermost layer of the abrasive band, which is open to the axis of rotation. In principle, however, it is also possible for the supporting body to be arranged radially outside the winding or to terminate with the radially inner end of the grinding section. The supporting body can be arranged at the level of the center of the abrasive band with respect to the axis of rotation or can be arranged towards the second main tool side. According to one embodiment, the grinding tool may be a grinding disk.
Furthermore, the abrasive band can be attached to the supporting body. In particular, the abrasive band is attached to the supporting body by means of the at least one stabilizing layer. The at least one stabilizing layer can thus overlap the abrasive band axially, or extend over the grinding section, and can extend at least partially over the supporting body. This prevents the abrasive band from detaching from the supporting body or rolling up during the grinding process. Analogous to the geometry of the grinding disk, the at least one stabilizing layer can be annular in shape. The reinforcing interlining can be designed as a circular blank, in particular with a central bore opening, which can be impregnated with the binder.
Furthermore, the support section and/or the supporting body can be plate-shaped. The support section may have a first main body side and a second main body side facing away from the first main body side. The two main body sides, like the main tool sides, are axially spaced apart. Further, the supporting body may have an outer circumferential edge, wherein the abrasive band is disposed about the outer peripheral edge. Preferably, the supporting body terminates radially outward with the outer circumferential edge. The supporting body may have a circular outer circumferential edge, which may be arranged concentric with the axis of rotation. The abrasive band may be arranged in a spiral around the outer circumferential edge and may be wound in the form of an Archimedean spiral. The first, radially outer end of the abrasive band may terminate at the outer periphery of the grinding disk and the second, radially inner end of the abrasive band may terminate at the outer circumferential edge of the supporting body. In particular, the second end of the abrasive band and especially the abrasive band as a whole is at least slightly spaced from the supporting body. Slight can mean that the distance between the second, radially inner end of the abrasive band and the supporting body is a maximum of 20 millimeters. Preferably, the abrasive band is connected to the supporting body only indirectly via the binder of the at least one stabilizing layer and optionally via the binder of the supporting body.
Preferably, the axial extension of the abrasive band is greater than an axial extension of the supporting body. This provides a stable grinding disk. The transition between the grinding section and the central support section can be stepped or rounded. In the grinding disk, the ratio of the maximum axial extension to the outer diameter of the grinding disk is preferably less than 1 to 1. Furthermore, the axial extension of the grinding disk along the wound abrasive band can be a maximum of 50 millimeters and preferably a maximum of 20 millimeters. The diameter of the outer circumference of the grinding disk can preferably be greater than 95 millimeters. Preferably, the diameter of the outer circumference of the grinding disk is in the range of 95 millimeters and 230 millimeters and further preferably in the range of 95 millimeters and 160 millimeters and even further preferably in the range of 125 millimeters and 150 millimeters. The diameter of the outer circumference edge of the supporting body is smaller than the diameter of the outer circumference of the grinding disk. Preferably, the diameter of the outer circumferential edge of the supporting body is about 15 percent to 50 percent and, in a further preferred manner, at least about 25 percent to 40 percent of the diameter of the outer periphery of the grinding disk.
A centrally arranged and axially extending bore can be formed in the supporting body to accommodate a spindle of a drive machine for driving the grinding tool in rotation about the axis of rotation. Furthermore, the supporting body can be cranked in order to be able to receive a clamping nut for fixing the grinding tool to the spindle of a rotary drive machine in a central cranking zone or in the recessed or axially recessed area. In the center of the supporting body, or in the central bore, a threaded bushing, a bore, for example, with a bore ring, or another way of fastening the grinding disk to the rotary drive machine, such as a bushing, an X-lock mount or the like, can be arranged in order to be able to fasten the supporting body directly or indirectly to the rotary drive machine via a separate support plate. The supporting body can also have a shaft, in particular one that is permanently integrated, for connecting the grinding disk to the drive machine.
According to one embodiment, the grinding tool may be a grinding sleeve, in which the abrasive band may be configured as a carrierless winding. Such a winding is also called unsupported or coreless. Furthermore, the grinding sleeve may also have the central supporting body around which the abrasive band is arranged. In the case of the abrasive sleeve, the ratio of the axial extension to the outer diameter of the abrasive sleeve is preferably greater than 1 to 1. Instead of the plate-shaped design of the supporting body, it can also be designed as a pin-like support onto which the spirally wound abrasive band of the abrasive sleeve can be attached or plugged.
The supporting body of the grinding tool can have vibration damping properties. In addition, the supporting body can serve to stabilize the grinding tool. Suitable materials for the supporting body include glass fabric or linen, which may be provided with binder, or materials made from wood pulp, cellulose, semi-cellulose or waste paper by gluing or pressing together, such as cardboard, or plastic, such as polyurethane, or rubber or the like.
Preferably, the abrasive band is a coated abrasive or abrasive cloth. Alternatively, the abrasive band can be a nonwoven without abrasive grains and/or a nonwoven with abrasive grains, which can also be referred to as abrasive nonwoven. In particular, the abrasive band is flexible. This allows the abrasive band to be wound as tightly as possible around the axis of rotation, so that the layers of the winding can lie closely on top of each other. Preferably, the abrasive band has a constant width, i.e. axial extension over the length of the band. In particular, the abrasive band has the grinding layer only on the side of the band facing away from the axis of rotation, which can also be referred to as the front side. In particular, the grinding layer extends over the entire surface of the front side of the abrasive band. Furthermore, the grinding layer can have abrasive grains which can be embedded in a matrix or a binder. The matrix can, for example, be a plastic or resin matrix. The abrasive grains can preferably be oriented in a majority direction, in particular perpendicular to the backing of the abrasive band. This may have been done, for example, by electro-static scattering, alignment in the magnetic field, or even via mechanical application methods.
The backing can be a fabric backing to which the grinding layer can be applied, in particular on one side. The fabric backing, or the fabric support, may comprise natural fibers, synthetic fibers, or a mixture thereof. Likewise, the backing can be made of non-woven materials, for example, non-woven fabrics, paper, scrims or other com-mon backing in the field of abrasives on backing, including vulcanized fiber, or subsequently weakened or arbitrarily recoated abrasives. Furthermore, the backing can be designed as thin and/or weakened as possible in order to be able to degrade quickly in the grinding process. This allows the grinding tool to release the grinding layer onto the underlying layer more quickly, allowing continuous exposure of fresh abrasive to the work surface on the workpiece being treated. The backing may be only thick enough to hold the grinding layer on the backing. In particular, such a thin backing may be paper or a thin woven or non-woven material having a thickness of, for example, less than 250 micrometers. The backing can also be weakened by perfora-tions, slits or the like.
Furthermore, the backing and/or the matrix, or the binder of the grinding layer, can be equipped with grinding aids or reinforced. Such grinding aids, like the fillers in the at least one stabilizing layer, may comprise, for example, quartz powder, amorphous silica, rutile or the like. In particular, the grinding aids are abrasive and may include fluorides, such as KBF4 or cryolite, or substances useful in other ways to the grinding process, such as lubricants, for example sulfur compounds, or anti-stick agents that reduce clogging of the grinding tool in the grinding process, such as stearates.
In particular, the abrasive band is formed in one piece. The grinding properties can be constant over the entire abrasive band. Alternatively, the abrasive band may have sections of different abrasive properties. Furthermore, the abrasive band can be composed of several profiled, band-shaped sections. The sections can be glued together, for example. Due to the different sections formed one after the other in the winding direction of the abrasive band, different properties can be combined. For example, radially outer layers of the abrasive band may have a coarser abrasive grain and radially inner layers of the abrasive band may have a finer abrasive grain. The combination of different abrasive grain types and sizes can enable a more universally applicable grinding tool. Furthermore, the combination of different backings and/or different abrasive bands can open up a wider range of applications for the grinding tool. This can be an average higher grinding performance on different materials or better appearance of the machined working surfaces on the workpiece, for example a finer surface, or better usability on rotary drive machines with low power.
The coarser the abrasive grain, the greater the thickness of the abrasive band or partial band. Accordingly, it is usually the case that the abrasive band or the partial band with a finer abrasive grain is thinner. Preferably, the grinding tool that has more coarse grain overall may have fewer layers than the grinding tool that has more fine grain in comparison. This allows the grinding tool to be provided with a constant outer diameter, regardless of the abrasive grain.
Furthermore, the grinding tool can be designed to be driven in a drive rotation direc-tion. This can be indicated on the label of the grinding tool, for example. The winding direction of the abrasive band can be opposite to the drive direction of rotation. This provides a more durable grinding tool. Alternatively, the winding direction of the abrasive band can also correspond to the drive direction of rotation. This increases the re-moval rate of the grinding tool, i.e. its aggressiveness.
According to one embodiment, the grinding tool has a single-layer winding comprising only the one abrasive band, which is spirally wound with a plurality of superimposed layers around the axis of rotation. Preferably, the superimposed layers of the abrasive band lie directly against each other, at least partially. To be directly adjacent to each other at least partially shall comprise, in the event that the grinding tool has the at least one stabilizing layer, the binder for attaching the wound abrasive band to the at least one stabilizing layer may be provided in the spaces between the layers in the at least one edge region of the abrasive band.
According to a further embodiment, the grinding tool comprises a multilayer winding with the abrasive band and at least one further abrasive band, wherein the abrasive band and the at least one further abrasive band are at least partially superimposed in multiple layers and are wound spirally with the multiple superimposed layers around the axis of rotation. In other words, the superimposed abrasive bands are wound together around the axis of rotation, resulting in the multi-layer structure. The at least one further abrasive band can be designed in the same way as the profiled abrasive band, so that reference is made here to the above description by way of abbreviation. In this way, abrasive bands of different types can be combined in the grinding tool. In particular, the winding may have two, three, four, five, six, seven, eight, or more than eight abrasive bands from the at least one abrasive band.
The abrasive bands form separate layers in the winding, with the abrasive bands lying unconnected on top of each other. It is possible that the abrasive bands are connected to each other at a radially inner end and/or a radially further outer end. Furthermore, the at least one further abrasive band may have a shorter band length than the abrasive band. As a result, the winding can have multilayer layers and single-layer layers. In particular, radially inner layers are multilayered and radially outer layers are single-layered. This gives the grinding tool different grinding properties, which result when the grinding tool is degraded and the outer radius becomes smaller as a result. At the beginning of the grinding process, only the abrasive band can be located in the outer circumferential surface of the grinding tool, and only when the winding is further degraded does the at least one additional abrasive band join the outer circumferential surface. In principle, the abrasive bands can also be of the same length, so that from the beginning the abrasive band and the at least one further abrasive band run out on the outer circumference of the grinding disk and all of the layers are correspondingly multi-layered.
As a further solution, a method for manufacturing the grinding tool of the type previously described is proposed, wherein the method comprises the following steps:
The band-shaped abrasive preferably has a grinding layer on only one side. The band-shaped abrasive may be a planar abrasive. In principle, the abrasive to be wound up can also be provided already profiled, so that it is convex in cross-section in the direction of the grinding layer. Pressing the wound primary material in this case will cause the abrasive to buckle further than already preformed.
The method results in the same advantages as described in connection with the grinding tool so that reference is made here to the above description by way of abbreviation. It is understood that all of the aforementioned embodiments of the grinding tool are transferable to the method and vice versa. Overall, the method enables a simple and cost-effective manufacturing of a grinding tool with which a uniform grinding pattern can be achieved on the workpiece to be machined during a grinding process.
The deformation of the originally flat primary material in the form of a band causes the primary material to buckle or bend and gives the abrasive band the desired profile geometry. The profiled abrasive band produced by forming can thus have a smaller axial extension than the width of the band-shaped primary material. For example, the profiled abrasive band may have an axial extension of about 10 millimeters and the band-shaped primary material may have a width of about 13 millimeters.
The wound primary material can be subjected in a press to a compressive force acting along the axis of rotation until the primary material, in particular the backing of the abrasive, yields and buckles. In the buckled state, the abrasive band receives the required profile geometry. The fact that the primary material is pressed in the wound or coiled state has shown that radially inner layers in particular acquire a V-shape, and with radially outer layers the profile geometry of the abrasive band transitions into a U-shape. This is advantageous because it gives the outer circumferential surface of the grinding tool a spherical grinding surface, especially one that is curved outward, due to the radially outermost layer.
The mold may have a bottom on which the wound primary material is placed. The cylindrical wall supports the primary material from the radial outside and prevents the winding from deflecting outward, so that the primary material can only buckle radially inward during pressing. In particular, the compressive force acts on the primary ma-terial in the direction of the axis of rotation, or a longitudinal axis around which the cylindrical wall is concentrically arranged, until the primary material buckles. This allows the profile geometry, which is open toward the axis of rotation, to be produced.
Preferred embodiments are illustrated in the drawings and described below. Wherein
The support section 39 has a first main body side 7 and a second main body side 8 facing away from the first main body side 7. The support section 39 comprises a supporting body 5, which is formed in the shape of a plate, in particular by pressing. The supporting body 5 is made, here merely by way of example, from two resin-impregnated circular blanks 10, 11, one above the other, which are pressed together. The two circular blanks 10, 11 are shown in
The grinding section 6 has an abrasive band 13 arranged as a winding around an outer circumferential edge 9 of the supporting body 5. The abrasive band 13 is wound in a spiral around the axis of rotation R with several, here exemplary eighteen, superimposed layers L1, L2, . . . L18. This results in a single-layer winding. In principle, however, it is also possible for the winding to be multi-layered with several such abrasive bands 13. The abrasive band 13 is flexible and may be an abrasive on a backing 14. As shown in
The abrasive band 13 is profiled in longitudinal section along the axis of rotation R and has a profile geometry that is open towards the axis of rotation R. The layers L1 . . . L18 of the abrasive band 13 are arranged reaching radially into one another, wherein a respective radially inner layer L2 . . . L18 of the abrasive band 13 is axially overlapped at least partially by an adjacent radially outer layer L1 . . . L17 of the abrasive band 13. In
Due to the, here, U-shaped profile geometry of the first layer L1 of the abrasive band 13, the circumferential side 4 of the grinding tool 1 is curved radially outward. The camber is maximum in a central grinding region 20 of the grinding tool 1. The precurved central grinding region 20 lies, due to the spiral winding at least substantially, on a circumferential circle with a diameter defining the outer diameter D1 of the grinding tool 1. The outer diameter D1 is larger than a maximum axial extension B1 of the grinding tool 1, which the grinding tool 1 occupies in the grinding section 6. The ratio between the axial extension B1 and the outer diameter D1 of the grinding tool 1 is preferably less than 1 to 1 and is, here merely by way of example, about 1 to 10. The supporting body 5 has an axial extension B5 that is smaller than the axial extension B1 in the grinding section 6. The supporting body 5 is thus axially offset relative to the grinding section 6, whereby the transition between the grinding section 6 and the supporting body 5 can be stepped. The grinding tool 1 is thus particularly suitable for machining weld seams and fillet welds as well as joints.
At the beginning of a grinding process, the band section of the grinding layer 16 extending over the first layer L1 is exposed in the circumferential side 4 of the grinding tool 1. The further radially inner layers L2 . . . L18 are then still completely covered by the first layer L1. In
The abrasive band 13 is a continuous band having a first end 21 and a second end 22. The first end 21 lies in the circumferential side 4 and the second end 22 terminates at the supporting body 5. The abrasive band 13 has a constant width B over its entire length, or a constant axial extension with respect to the axis of rotation R. The abrasive band 13 comprises, here merely by way of example, three partial bands 23, 24, 25, which are arranged one behind the other in the winding direction and are connected or bonded to one another. In principle, however, it is also possible for the partial bands 23, 24, 25 to be loosely adjacent to one another. Furthermore, it is also possible that the abrasive band 13 is a continuous abrasive band that has consistent grinding properties along its length. The winding direction is indicated by the arrow W in
The partial bands 23, 24, 25 differ from each other in their grinding properties. The first partial band 23 extends at least approximately over the band section of the abrasive band 13 forming the first layer L1. The backing 14 of the first partial band 23 is, here merely exemplary, made of paper, in order to achieve a rapid degradation of the first layer L1. The subsequent layers L2, L3 are formed by the second partial band 24, in which, here merely by way of example, the backing 14 is made of a woven fabric. Thus, compared to the first partial band 23, the second partial band 24 is more resistant and allows higher removal rates. The radially more inner layers L4 . . . L18 are formed by the third partial band 25, whose backing 14 is also made of a fabric. Unlike the previous two partial bands 23, 24, the third partial band 25 has abrasive grains 18 of finer grain size to allow fine grinding. In this way, at the beginning of the grinding process, the grinding tool 1 initially allows a high removal rate while producing a uniform surface on the workpiece. When the fourth layer L4 and the other radially inner layers L5 . . . L18 are reached, the removal rate of the grinding tool 1 decreases and the grinding pattern becomes increasingly refined. In principle, however, it is also possible for the abrasive band 13 to have consistent abrasive properties along its entire length.
Furthermore, the grinding tool 1 has two stabilizing layers 26, 27, in particular ring shaped, between which the abrasive band 13 and the supporting body 5 are held. The stabilizing layers 26, 27 connect the abrasive band 13 to the supporting body 5. In
The abrasive band 13 is bonded to the stabilizing layers 26, 27 via the binder 28. Specifically, the abrasive band 13 has an edge region 31, 32 at each axial end with a circumferential edge 33, 34 delimiting the abrasive band 13. Due to the winding of the abrasive band 13, the respective circumferential edge 33, 34 follows the trace of a spiral. It can be seen in
Furthermore, the binder 28 may be arranged in a transition region 36 formed between the radially innermost layer L18 and the outer circumferential edge 9 of the supporting body 5, or may have penetrated and hardened during the pressing process when the grinding tool 1 is manufactured. It can be seen in
To make the grinding tool 1, the second reinforcing interlining 30 may first be placed in a mold (not shown) having a cylindrical wall and a bottom. Subsequently, the coiled primary material 38 can be positioned in the mold on the lower reinforcing interlining 30. in the process, the radially outermost layer of the primary material 38 rests against the cylindrical wall of the mold. Further, the two fabric circular blanks 10, 11 are inserted into the center of the spirally wound primary material 38, and then the upper reinforcing interlining 29 is placed on the wound primary material 38. Optionally, the label 37 may be placed on the upper reinforcing interlining 29. In the further manufacturing process, a pressure plate, the outer diameter of which corresponds to the inner diameter of the cylindrical wall of the mold, is placed on the label 37 or the upper reinforcing interlining 29, and the components inserted in the mold for the grinding tool 1 are pressed together under a pressure force and temperature acting along the axis of rotation R to form the grinding tool 1. During pressing, the wound primary material 38 yields to the compressive force, whereby the primary material 38 can only buckle towards the center due to the radially outer support provided by the mold and the radially inner support provided by the fabric circular blank 10, 11. In the process, the primary material 38 buckles in a V-shape in the radially inner layers and, in particular, the radially outermost layer L1 buckles in a U-shape. The buckled primary material 38 forms the profiled abrasive band 13. As a result of the buckling of the primary material 38, the outer circumferential edge 9 of the supporting body 5 can and may deform. To further affect the buckling of the primary material 38, the mold may have chamfers on the cylindrical wall at the top and bottom edges. Furthermore, the bottom of the mold can have a central elevation on which the fabric circular blanks 10, 11 for the supporting body 5 can be placed. During pressing, the binder 28 partially penetrates into the spaces 35 and into the transition area 36 and, in the cured state, thus bonds the abrasive band 13 to the supporting body 5.
In
In
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021114052.8 | May 2021 | DE | national |
This application is a National Stage of International Application No. PCT/EP2022/064447 filed May 27, 2022, claiming priority based on German Patent Application No. 102021114052.8 filed May 31, 2021.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/064447 | 5/27/2022 | WO |
