Patent Application
20210316419
Exemplary embodiments of the invention relate to a grinding device and to a grinding means.
Such grinding devices consist of a shape-stable support element, which may be in the form of a support disc or in the form of a grinding block, the latter in the case of manual use.
The grinding means is in the form of a flexible grinding sheet or a grinding belt, which is held on the support element by means of a hook-and-loop connection, for which purpose the support element/grinding means pairing has suitably designed hook-and-loop layers.
In the case of the grinding means, this is provided on the side of a carrier that is located opposite a grinding layer, which consists of an abrasive grit, it being possible for the carrier to be made of paper, film, fabric, or a combination thereof.
In addition to this hook-and-loop connection, which establishes a form fit, it is proposed in DE 10 2017 108 191, which was not previously published, to hold the grinding means on the support element, i.e., a support disc, by means of a material bond, by means of a form fit or by frictional engagement, the frictional engagement being established by sucking the grinding means onto the support disc.
The material bond takes place by adhesion, wherein the contact surface of the carrier that makes contact with the support disc is equipped with a self-adhesive layer.
However, the known connections of the grinding means to the support element are disadvantageous in some respects, in particular with regard to handling, but also with regard to relatively cost-intensive production.
For instance, the construction of the carrier for providing the hook-and-loop or self-adhesive layer is cost-intensive, in particular since such a layer has to be formed in multiple stages. In addition, they are subject to a relatively high degree of wear due to the connection being made and released.
The holding of the grinding means on the support element by means of vacuum requires special measures with regard to the air permeability and sealing. This means that the support disc must have apertures, through which air is sucked in order to hold the grinding means thereon.
The handling when equipping the grinding device with grinding means is also sometimes quite awkward and stands in the way of optimized use, in particular with regard to changeover times.
This applies equally to a grinding device as discussed in DE 10 2010 001 769 A1, in which frictional engagement between the support element and the grinding means is achieved in that the support element is provided with bristles on the side thereof facing towards the grinding means, which bristles engage in a necessarily porous surface of the carrier.
The disadvantage with this is that the carrier is permeable, as a result of which grinding dust enters the area of connection to the support element, which leads to considerable problems as the operating time increases.
U.S. Pat. No. 3,345,785 A discloses a grinding device with the suggestion of a frictional connection between a flexible support element and a grinding means, wherein the friction fit is established between a peripheral flange of the grinding means and the support element.
The problem addressed by the invention is that of further developing a grinding device and a grinding means of the generic type in such a way that it can be produced more easily and cost-effectively, and it is easier to handle.
First, it is crucial that the coefficient of friction between the support element and the grinding means, which is held thereon across the entire surface, is sufficient to absorb the longitudinal and transverse forces that occur during grinding, wherein according to the invention the coefficient of friction of the pairing is between 0.2 and 0.5.
As has been found, such a coefficient of friction is sufficient, in particular, when grinding a finished surface at certain points, wherein the friction force between the support disc and the grinding means is generated by pressure when the grinding device, i.e., the support element and the grinding means, is pressed onto the surface to be treated. This friction force is preferably between 0.5 and 2.0 N/mm2.
As long as the friction force is greater than the counterforce produced by the grinding process, mutual displacement of the support element and grinding means is prevented. Given the appropriate coefficient of friction of the pairing, grinding across a surface is possible without any problem, wherein the grinding means is designed to be flexible in the same way as in the case of point grinding.
The grinding means, which may be in the form of a single sheet or a grinding belt, consists of a carrier and a grinding layer held thereon. While the carrier, which forms a contact layer to the support element, is constructed in multiple stages in the prior art and is designed in particular for a hook-and-loop or adhesive connection, the carrier according to the invention is produced as a single layer made of a suitable plastic, which should be both elastic and flexible.
Polymers, elastomers or leathers are particularly suitable for this, the thickness of the carrier being between 0.7 and 4 mm.
As mentioned, due to the flexible and elastic nature of the carrier, the grinding of both flat and curved surfaces is possible, the curved surfaces being convex or concave.
As has surprisingly been found, the frictional connection between the support element and the grinding means is particularly advantageous when the grinding means is in web form. Since the grinding belt is precisely aligned and guided in the area of connection to the support element, problem-free positioning between the support element and the grinding sheet is ensured.
The grinding belt is lifted off for moving the support element to the next position, or the grinding belt slides away from the support disc when the lifting or tearing force with which the grinding belt is detached from the support element is greater than the friction force between the support element and the grinding belt.
In a manner known per se, the grinding itself takes place, as mentioned, at certain points or across a surface, using orbital, rotating or vibrating movements.
Instead of the aforementioned one-piece construction of the carrier, there is also the possibility of multi-piece construction. By way of example, the carrier carrying the grinding means may be made of paper, while the contact surface which bears against the support element is made of an elastomeric, rubber-like or leather material.
Particularly if the surface of the carrier is smooth, for example in the form of a film, the surface assigned to the support element is slightly structured and is likewise formed of an elastomeric, rubber-like, or leather material.
The rough surface of the carrier formed of a fabric is slightly structured on the side held by frictional engagement on the support element and is possibly formed of a foam. For the pairings mentioned, additional anti-slip means are not absolutely necessary.
In any case, account should be taken of the fact that the surfaces may be dry, moist or wet, with a corresponding effect on the friction pairs.
One exemplary embodiment of the invention will be described below with reference to the accompanying drawing.
The single FIGURE shows a grinding device according to the invention in a schematic side view.
The FIGURE shows a grinding device 1 for removing a flaw in a surface, in particular a finished surface, of an object (not shown) by grinding.
This grinding device 1 has a robot arm 2 and a support element 3 held thereon in the form of a support disc, which support element is movable, for example in an orbital, vibrating or rotating manner, relative to the surface in order to grind the flaw.
In the grinding position, i.e., in contact with the surface of the object, as shown in the FIGURE, a grinding means 5, in the example in the form of a grinding belt, bears with frictional engagement against the support element 3, wherein the rear side of the grinding means 5, so to speak, which bears against the support element 3, is designed as a carrier, which on the other side carries an abrasive grit that makes contact with the surface of the object.
The grinding means 5 is held in a dispenser in the form of a cassette 4 and is wound as a roll 6 on an unwinding shaft 7, and is wound onto a winding shaft 8, preferably in cycles, in a manner corresponding to the grinding process.
The frictional engagement between the support element 3 and the grinding means 5 is released by lifting the support element 3, so that the grinding means 5 can be advanced without hindrance.
Although the invention has been illustrated and described in detail by way of preferred embodiments, the invention is not limited by the examples disclosed, and other variations can be derived from these by the person skilled in the art without leaving the scope of the invention. It is therefore clear that there is a plurality of possible variations. It is also clear that embodiments stated by way of example are only really examples that are not to be seen as limiting the scope, application possibilities or configuration of the invention in any way. In fact, the preceding description and the description of the FIGURES enable the person skilled in the art to implement the exemplary embodiments in concrete manner, wherein, with the knowledge of the disclosed inventive concept, the person skilled in the art is able to undertake various changes, for example, with regard to the functioning or arrangement of individual elements stated in an exemplary embodiment without leaving the scope of the invention, which is defined by the claims and their legal equivalents, such as further explanations in the description.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2018 121 625.4 | Sep 2018 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/073205 | 8/30/2019 | WO | 00 |
