Sanding element

[0001] The invention relates to an abrasive element with successively overlapping layers comprising abrasive grains as set out in the preamble of claim 1. An example of such an abrasive element is described in EP-A-1 093 885.

[0002] Such abrasive elements are usually made in the form of a so-called laminated disc, where successive layers are arranged on the disc in a circumferential direction so that they overlap. Such abrasive elements are used, for example, for grinding and finishing, and especially for polishing welds on metal workpieces.

[0003] A laminated disc with a series of overlapping layers is described in US Patent US 6 582 289. The layers are formed alternately from an abrasive cloth containing abrasive grains and from layers provided with an active abrasive layer. The active abrasive layer does not contain abrasive grains, it is mainly used to remove the removed material and reduces the heating of the workpiece to be ground.

[0004] However, existing abrasive elements have the disadvantage of being relatively hard in contact with the surface of the workpiece to be machined, making it difficult to exert constant pressure between the workpiece and the abrasive element. In addition, existing abrasive elements have a relatively short life, after grinding the metal surface with such an aggressive abrasive element, the surface must then be treated with a so-called finishing wheel to obtain a smooth and aesthetically acceptable surface.

[0005] The object of the invention is to prevent these drawbacks by providing an abrasive element with a much longer life than the current abrasive elements, while allowing a very perfect finishing of the workpiece to be carried out in a very quick manner, as a result of which two different discs will not be necessary. The abrasive element of the invention has the properties of claim 1 and allows material to be removed from the workpiece as well as perfect finishing of the workpiece, in both cases from an aesthetic and technical point of view. Namely, with the abrasive element according to the invention, it is possible to achieve a very high surface smoothness in one operation.

[0006] To this end, said layers are formed alternately from abrasive layers and from compressible layers in such a way that each abrasive layer rests on the compressible layer.

[0007] Practically, compressible layers are elastically compressible.

<td>[0008] In a favorable way,</td><td>mentioned</td><td>layer</td><td>compressible</td>

<td>contain nonwoven fibers,</td><td>especially</td><td colspan="2">synthetic fibers</td>

<td>non-woven.</td><td></td><td></td><td></td>

<td>[0009] According to preferred</td><td>example</td><td>execution</td><td>element</td>

abrasive according to the invention, abrasive grains are provided on said fibers.

[0010] According to an interesting embodiment of the abrasive element of the invention, said fibers are joined together by gluing, for example, with a synthetic resin, and thus form a three-dimensional open fibrous structure.

[0011] Preferably, said layers are fixed on a circular disk-shaped support, whereby the free edges of these layers run virtually radially, whereby the abrasive element forms a so-called laminated disc.

[0012] Other details and advantages of the abrasive element of the invention will be apparent from the following description of several special embodiments of the invention; the description is given merely as an example and in no way limits the scope of the claimed protection; the references used here refer to the attached drawings.

[0013] FIG. 1 schematically shows a grinding element according to the invention in plan view.

[0014] Fig. 2 schematically shows the abrasive element in a cross-sectional view taken along the line II-II according to Fig. 1.

[0015] Fig. 3 schematically shows in more detail the compressible layer according to the invention, in cross section and in a larger scale.

[0016] FIG. 4 schematically shows two pipes welded together at an angle of 90 ° in top view.

[0017] Equal references denote identical elements in the drawings.

[0018] The invention generally relates to an abrasive element, and more particularly to a laminated disc which comprises successively overlapping layers. The layers are formed alternately from abrasive layers, the outer or free surface of which contains abrasive grains, and from compressible layers on which the abrasive layers rest.

[0019] Fig. 1 shows an abrasive element in the form of a laminated disc 1. It comprises an almost indeformable circular support 2 in the form of a disc on which the abrasive layers 3 and the compressible layers 4 are alternately attached in such a way that each layer 4 overlaps on the friction layer

3. In this way, the abrasive layer 3 always rests with its working part on the corresponding compressible layer 4.

[0020] Said support 2 has a central hole 5 through which the laminated disc 1 can be attached to the drive in a known manner. A drive, not shown in the drawings, allows the laminated disc 1 to rotate at high speed about its axis, and when the disc 1 is pressed against the workpiece, layers 3 and 4 contact the ground surface of said workpiece.

[0021] Thanks to this, the disc of the invention allows even contact with the surface of the workpiece under almost uniform pressure, due to the compressibility of the layers 4.

[0022] The abrasive layers 3 are formed, for example, of cotton or polyester textile fabric onto which the abrasive grains are attached by means of a binding layer. Thus, such layers 3 are formed, for example, of abrasive cloth. The layers may also be formed of paper, polyester or a mixed substrate, such as a blend of polyester and cotton, on which abrasive grains are provided. [0023] The compressible layers 4 consist mainly of fibers 10. The compressible layers 4 are formed in particular of non-woven synthetic fibers 10, which are joined together by means of a synthetic resin and thereby form a three-dimensional open fibrous structure. The fibrous structure is glued onto the nonwoven base 11 or otherwise attached to it.

[0024] Furthermore, the abrasive grains 9 are attached to the fibers 10 by means of synthetic resin. To ensure that when using the laminated disc 1 the fibers 10 adhere to each other irrespective of the heat generated during grinding, thermosetting synthetic resin is preferably used as said synthetic resin. Synthetic fibers 10 are formed, for example, from polyamide yarns with a diameter of 0.75 to 0.85 mm.

In this way, the compressible layers 4 form a three-dimensional open fibrous structure that deforms elastically. The fibers 10 run in an almost random manner in the structure. The compressible layer 4 is shown in cross-section in Fig. 3.

[0026] Because the layers 3 and 4 overlap, each abrasive layer 3 is at least partly supported by the compressible layer 4. On contact of the laminated disc 1 with the surface of the workpiece to be finished, on the contact surface between said workpiece and laminated 1 the shield will be exerted practically uniform pressure, as already mentioned above. [0027] To ensure relatively soft contact between the surface of the workpiece and the laminated disc 1, the thickness of the compressible layers 4 is preferably equal to at least three times the thickness of said abrasive layers 3.

[0028] According to an interesting embodiment of the abrasive element according to the invention, the thickness of the abrasive layers 3 is almost 0.5 mm to 1 mm, while the thicknesses of the compressible layers 4 are, for example, from 3 to 8 mm. Each of layers 3 and 4 forms a rectangle with a shorter side 6 having a length of almost 20 mm and a longer side 7 of about 30 mm. The longer side 7 of the upper side of layers 3 and 4, in other words their free edge, runs virtually radially on the support 2, while the shorter side 6 lies in the tangential plane around the perimeter of the layers.

Layers 3 and 4 overlap towards their short side 6 by a distance virtually equal to 2/3 to 5/6 the length of this short side 6. Layers 3 and 4 preferably overlap by 3/4 the length of the short side 6.

[0030] Layers 3 and 4 are firmly attached to said support 2 by means of an adhesive layer 8.

[0031] The laminated disc 1 according to the invention is of particular interest when used to remove a surface layer from a metal surface.

[0032] Fig. 4 schematically shows a workpiece consisting of two pipes 12 and 13, made of stainless steel with a diameter of 40 mm, which was welded together at a right angle. The formed weld 14 extends at an angle of 45 ° to the axis of the pipes 12 and 13.

[0033] According to the state of the art, after traditional aggressive grinding with an abrasive device, e.g. a fibrous structure in which abrasive grains are supplied.

[0034] In some cases it is possible to grind and finish the workpiece in one operation with one and the same finishing wheel. In this case, the finishing wheel is completely worn after smoothing the surface of five workpieces. When the same finishing process is carried out by means of the laminated disc 1 according to the invention, it has been observed that one disc can process sixteen such workpieces before it is worn.

[0035] In addition, it has been found that for smoothing welded joints with a traditional finishing wheel, the required machining time is 41 minutes and 36 seconds. When 25 identical welds are smoothed with the laminated disc of the invention, only 23 minutes and 52 seconds are needed.

[0036] Thus, it has been established from research that the laminated disc of the invention can process almost twice as fast as traditional finishing discs. Furthermore, it has been found that the durability of the laminated disc according to the invention is more than three times longer than the durability of a traditional finishing disc.

[0037] The abrasive layers and compressible layers may contain all types of abrasive grains, such as, for example, ceramic abrasive grains or alumina abrasive grains, zirconia oxygen abrasive grains, silicon carbide or agglomerate of these grains. Very good results have been obtained for so-called structured abrasive grains, which are described, for example, in European patent EP 1 011 924 and which are used, for example, according to a regular distribution with a specific orientation on the layers of the abrasive element. Structural grains are created, for example, from traditional abrasive grains, the surface of which is covered with so-called functional powders, such as finely divided abrasive grains, antistatic additives, lubricants, etc.

[0038] In addition, abrasive layers 3 and / or compressible layers 4 may be formed of a plurality of layers of the same type. Thus, it is also possible for the abrasive element to include a series of overlapping layer assemblies, as a result of which these assemblies are alternately formed of at least one abrasive layer 3 and at least one compressible layer 4. Each abrasive layer set 3 rests on the same compressible layer assembly 4. This means, inter alia, that an abrasive layer assembly comprising, for example, two or more abrasive layers 3 may rest on only one compressible layer 4, or that, for example, each abrasive layer 3 may rest on the compressible layer assembly 4. The layers of each layer assembly preferably overlap .

[0039] In another embodiment of the abrasive element

<td colspan="2">according to the invention layers</td><td colspan="2">3 and 4 not necessarily</td><td>they must be</td>

<td>fixed</td><td>to support in</td><td>shield shape</td><td>but</td><td>may be</td>

<td>also</td><td>be fastened on</td><td>example to the belt</td><td>about</td><td>closed</td>

<td>circuit</td><td>^.</td><td></td><td></td><td></td>

<td> 10 [0040]</td><td>Friction element</td><td>according to the invention</td><td>no</td><td>must be</td>

used for the finishing treatment of welded joints made of only stainless steel, but can also be used to improve the smoothness of the surface of generally any material, such as metal alloys, stone, plastics, etc.

CIBO NV

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