US20050233681A1

US20050233681A1 - Abrasive element support with self-sucking device and method for removing grinding particles

Info

Publication number: US20050233681A1
Application number: US11/027,616
Authority: US
Inventors: Peter Jost
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-04-17
Filing date: 2004-12-30
Publication date: 2005-10-20
Also published as: EP1586417A2; DE102004018727A1; EP1586417A3

Abstract

An abrasive element support having an axis of rotation and a fastening surface for attachment of an abrasive element is designed as a self-sucking device in the form of a radial fan device. The fastening surface has a fastening element such as a hook and loop fastening element that allows passage of grinding particles in a direction parallel to the fastening surface. The radial fan device has intake and exit openings, wherein the intake opening is arranged closer to the axis of rotation than the exit opening. The intake and exit openings communicate through at least one acceleration chamber of the radial fan device.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to an abrasive element support having an axis of rotation and a fastening surface for fastening an abrasive element thereto.
2. Description of the Related Art
Such an abrasive element support is provided in order to support an abrasive element during grinding. For grinding a surface, the abrasive element support is driven in rotation by means of a drive shaft. The rotation of the abrasive element support with the abrasive element attached thereto generates grinding particles on the surface to be ground or machined. In this connection, there is the risk that the grinding particles or grinding dust will clog the abrasive element which has undesirable effects on the further grinding process. The abrasive element will lose its abrasive action already before a point in time where its abrasive particles become dull. These grinding particles should be removed as much as possible from the surface to be ground and from the grinding surface of the abrasive element so that the grinding efficiency of the abrasive element is maintained.
In this connection, it is known to provide the abrasive elements with through openings that connect the grinding surface to the backside of the abrasive elements. These through opening ensure that the grinding particles reach the backside of the abrasive elements. The through openings are aligned with openings within the abrasive element support that are in communication with a suction device through the axis of the abrasive element support. The grinding particles that pass through the openings are then transported away by the external suction device. However, this requires an external suction device and also a hollow drive shaft that is not always available.
Other grinding machines are provided with a suction hood. The suction hood is stationary and encloses the rotating abrasive element support at a minimal spacing. The external suction device connected to the suction hood generates a suction effect. This suction effect moves the particles radially outwardly within the fastening layer of the abrasive element support and between the abrasive element and the ground surface so that the particles reach an annular gap between the abrasive element support and the suction hood where they are received by the connected suction device. This suction arrangement however has only a limited effect.

SUMMARY OF THE INVENTION

It is an object of the present invention to design the suction effect acting on an abrasive element support to be more effective.
In accordance with the present invention, this is achieved in that the abrasive element support is configured as a self-sucking device.
Such an abrasive element support requires no suction device connected to the abrasive element support in order to transport the grinding particles away from the grinding surface on defined paths. The grinding particles are automatically transported away as a result of the properties of the abrasive element support. The abrasive element support automatically generates a suction effect simply by its rotation. This is to be understood as self-sucking device. The self-sucking device on an abrasive element support takes advantage of the movement of the abrasive element support during grinding. A combination of a rotational movement with a translatory movement is possible also, for example, oscillating movements of the abrasive element support. By means of these movements, a suction effect on the abrasive element support is produced. In contrast to this, in the case of abrasive element supports with external suction devices, for example, in the form of a vacuum cleaner, an additional external device must be provided in order to remove the grinding particles.
Preferably, the self-sucking device is configured as a radial fan device. In an abrasive element support configured as a radial fan device, the grinding particles and the surrounding air are moved in the radial direction. This is an especially effective way of using the movement of the abrasive element support for a self-sucking effect. As soon as grinding particles are produced by the rotational movement of the abrasive element support, the particles are moved away from the grinding surface by the radial fan device. In order for this movement to be generated, the rotational movement of the driven abrasive element support is utilized for the suction effect. The suction effect of the radial fan device is produced by a constructive configuration on the abrasive element support. In this connection, the rotational speed and the geometry of the radial fan device are important for the suction effect.
In a preferred embodiment, the fastening surface has an attachment device that enables particle flow therethrough in a direction parallel to the fastening surface. Such a fastening surface therefore has two functions. Its original function, i.e, to secure the abrasive element on the abrasive element support, is expanded by the function of providing passages for transporting away the grinding particles. These passages can also be provided by the abrasive element itself on the backside of the grinding surface. By configuring the fastening device such that the particles can flow through the fastening device parallel to the fastening surface, the particles can move parallel to the surface to be ground without the grinding surface of the abrasive element becoming clogged by particles. In this way, the effectiveness of the abrasive element during grinding is maintained.
Preferably, the radial fan device has at least one intake opening and at least one exit opening, wherein the intake opening is arranged closer to the axis of rotation of the abrasive element support than the exit opening, wherein the intake opening and the exit opening communicate via at least one acceleration chamber that has at least one acceleration device arranged between radial inner and radial outer locations. In this way, the geometry of the radial fan device provides a contribution in that the rotational movement of the abrasive element support alone generates already a suction effect by means of the radial fan device. This suction effect is the greater the faster the radial fan device rotates and the farther the intake openings and the exit openings are spaced from one another. As a result of the suction effect, the particles move from the surface to be ground in the direction toward the intake opening and flow through it. Subsequently, the particles move farther within the acceleration chambers from a radial inner location to a radial outer location and reach the exit openings of the radial fan device. At this point, the particles can be collected. For transporting the grinding particles away from the grinding surface to the exit openings of the radial fan device, an external suction device is therefore not required because the radial fan device produces a self-sucking action that is the result of the selected geometry and the rotational movement. The radial fan device ensures that the grinding particles are removed continuously from the grinding surface and can be collected at defined locations, i.e., at the exit openings of the radial fan device, or are available for being transported farther.
Preferably, the acceleration device forms an uninterrupted boundary delimiting the acceleration chamber. The acceleration device ensures that the air containing the grinding particles is moved in the tangential direction by the centrifugal force generated by the rotational movement of the abrasive element support. In this way, a radial suction effect is generated that moves the air and the particles from a radial inner location in a radial outward direction.
Preferably, the acceleration device is impermeable to air. Since the acceleration device moves grinding particles and air within the acceleration chambers, it is especially effective when the acceleration device itself is not air-permeable.
Preferably, the sum of the surface areas of the exit openings is at least as great as the sum of the surface areas of the intake openings. In this configuration of the opening surfaces, the suction effect of the abrasive element support is particularly effective. Also, bottlenecks during the transport of the grinding particles are prevented in this configuration. The grinding particles pass first through the intake openings and flow subsequently to the exit openings. Since the sum of the surface areas of the exit openings is greater than the sum of the surface areas of the intake openings, there is in any event sufficient space for the grinding particles when passing through the exit openings so that the particles can exit without impairment from the radial fan device.
Advantageously, the exit openings are uniformly distributed about the circumference of the abrasive element support. With a uniform rotation of the radial fan device, it is achieved in this way that the same quantities of grinding particles will flow out of the exit openings. This prevents overload and clogging of the grinding particles within individual exit openings.
It is preferred that the acceleration chamber has a deflecting device. A deflecting device enables that the spatial conditions in the fan device can be used effectively. For example, exit openings can be arranged in the outer surface of the abrasive element support while intake openings face the surface to be ground. The outer surface is a suitable location in order to provide a spacing as large as possible between the intake openings and the exit openings.
Preferably, the acceleration chamber has air deflecting means that impart to the grinding particles an exit direction with an axial directional component when leaving the exit openings. Air deflecting means can be integrated into the boundaries of the acceleration chamber or can be provided as separate elements within the acceleration chamber. The air deflecting means serve to direct the airflow with the grinding particles in a certain direction when leaving the acceleration chamber through the exit openings. It is practical in this connection when the grinding particles upon exiting the exit openings are guided away from the plane of the fastening surface of the abrasive element support. Their movement then has an axial directional component.
Preferably, the radial fan device has a single intake opening that is arranged in the radial center of the radial fan device. A single intake opening in the radial center of the radial fan device has the advantage that in this way the spatial conditions are effectively utilized. With this configuration it is achieved that a spacing as large as possible between the exit openings, arranged, for example, on the circumference, and the central intake opening is provided. This improves the suction effect of the radial fan device.
In an especially preferred embodiment, the fastening surface of the abrasive element support is provided with a hook and loop fastening element. The fastening surface, in the form of a hook and loop fastening element, can engage an adjoining hook and loop fastening element provided on the abrasive element in order to produce in this way a secure connection during the rotation of the abrasive element support and the abrasive element. A hook and loop fastener connection can be easily released so that without auxiliary devices the abrasive elements can be exchanged. Moreover, a hook and loop fastening element is permeable for grinding particles.
Expediently, the abrasive element support has a collecting device. In this way, the grinding particles can be collected with a single device and can be transported farther. A collecting device can be, for example, a hood that is connected to an external suction device in the form of a vacuum cleaner.
Advantageously, the collecting device is arranged at a spacing to the plane of the fastening surface of the abrasive element support. Because of the spacing of the collecting device from the plane of the fastening surface there is also spacing between the collecting device and the surface to be machined. Such an arrangement prevents undesirable frictional contacts that could lead to an undesirable alteration of the surface to be machined, for example, in the form of scratches. Also, the person grinding the surface to be machined can see immediately the grinding result without the collecting device blocking the person's view.
According to another embodiment it is provided that the abrasive element support is configured as an self-sucking attachment. This attachment can be fastened on an abrasive element holder that has no self-sucking device. In this way, it is possible to generate a self-sucking effect on the abrasive element holder also.
Preferably, the self-sucking attachment has a contact surface for attaching the self-sucking attachment on the abrasive element holder. The contact surface of the self-sucking attachment can be configured such that it adjoins areally a surface of the abrasive element holder without the function of the self-sucking attachment being affected.
Preferably, the contact surface is provided with a hook and loop fastening element. The abrasive element holder has in many cases already such a hook and loop fastening element. Accordingly, with an additional hook and loop fastening element on the self-sucking attachment it is possible easily to connect the abrasive element holder and the self-sucking attachment.
Expediently, the self-sucking attachment has a positioning arrangement. With such a positioning arrangement, the abrasive element support with self-sucking device and the abrasive element holder can be aligned with one another. During their common grinding movement it is ensured in this way that the abrasive element support and the abrasive element holder will not move relative to one another and remain centered relative to one another. The positioning arrangement can also be configured as a unitary part of the self-sucking attachment.
In regard to an abrasive element support arrangement comprising an abrasive element support and an abrasive element, wherein the abrasive element support has an axis of rotation and a fastening surface for attachment of an abrasive element, the object of the present invention is solved in that the abrasive element has through openings that are in communication with a self-sucking device of the abrasive element support.
While the abrasive element support and the self-sucking device rotate, for example, about a common axis of rotation, grinding particles are produced on the abrasive element because of the rotational movement. These grinding particles can be transported away through the through openings provided within the abrasive element. This is achieved by the self-sucking device that is in communication with the through openings. As a result of the suction effect of the self-sucking device, the grinding particles reach the backside of the abrasive element and can be moved farther by means of the self-sucking device.
It is preferred that the through openings of the abrasive element communicate with intake openings of the self-sucking device through a hook and loop fastening device through which the particles can flow radially, wherein the hook and loop fastener device is comprised of a hook and loop fastening element on the abrasive element support and a hook and loop fastening element on the abrasive element. A hook and loop fastening element provided on the abrasive element support and also on the abrasive element provides a simple possibility for connecting the abrasive element support and the abrasive element with one another. When at least one of the hook and loop fastening elements is designed to allow particles to flow through, the particles can move radially within this hook and loop fastener device in the direction to the intake openings. In most of the hook and loop fastener devices, both hook and loop fastening elements allow passage of particles.
In an advantageous embodiment, the self-sucking device is connected to an external suction device. The grinding particles, after exiting from the exit openings, can thus be transported farther and can be collected finally in the external suction device.
In a method for removing grinding particles or grinding dust from a grinding surface of an abrasive element on a rotating abrasive element support, the object of the present invention is solved in that the abrasive element support removes the grinding particles by means of a self-sucking device from the grinding surface.
The self-sucking device can be integrated into the abrasive element support but can also be in the form of an attachment connected to the abrasive element support. The grinding particles are removed along defined pathways from the grinding surface so that newly produced grinding particles are continuously transported away during the grinding process by means of the suction effect of the self-sucking device.
Preferably, the self-sucking device of the abrasive element support moves the grinding particles first in a first layer radially inwardly in the direction of at least one intake opening and, after they have passed through the intake opening, moves them in a second layer radially outwardly. Because the intake openings are positioned radially farther inwardly than the exit openings, the grinding particles first move radially inwardly. After passing through the intake openings, the grinding particles are conveyed outwardly by the suction effect of the self-sucking device of the abrasive element support. The first layer is, for example, a hook and loop fastening element and the second layer is, for example, the acceleration chamber of the self-sucking device. Both layers communicate through at least one intake opening.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing:
FIG. 1 is a schematic illustration of a first embodiment of a complete abrasive element support;
FIG. 2 is a section II-II of the abrasive element support according to FIG. 1 having an abrasive element as well as a collecting device attached thereto;
FIG. 3 is a section III-III of the abrasive element according to FIG. 2;
FIG. 4 is a section IV-IV of the abrasive element support according to FIG. 2;
FIG. 5 is a schematic section view of a second embodiment of an abrasive element support with abrasive element and a collecting device attached thereto; and
FIG. 6 is a schematic section view of a third embodiment of the abrasive element support with attached abrasive element.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Same elements in FIGS. 1 through 6 are identified with same reference numerals.
FIG. 1 shows an abrasive element support 1 on which an abrasive element 2 in the form of a disc is mounted. The abrasive element support 1 is mounted by means of a fastening device 3 on a drive shaft 4 so that, when rotating the drive shaft 4, the abrasive element support 1 and the abrasive element 2 rotate synchronously about an axis of rotation 5.
In FIG. 2, the abrasive element support 1 is illustrated in a side view according to section line II-II. The abrasive element support 1 is additionally enclosed by a collecting device 6. The abrasive element 2 is resting against the surface 7 to be ground. The abrasive element 2 is provided with through openings 8 that can also be seen in FIG. 3 showing section III-III as indicated in FIG. 2.
When by rotation of the abrasive element 2 with the driven abrasive element support 1 the surface 7 is ground, grinding particles are produced. These grinding particles pass through the through openings 8 as a result of the suction effect caused by the geometry of the abrasive element support 1 and reach the hook and loop fastening element 9, for example, a velvet fabric, a pile fabric or * a loop fabric, of the abrasive element 2. The abrasive element support 1 is provided on its fastening surface with a fastener in the form of a hook and loop fastening element 10. This hook and loop fastening element 10, for example, a hook fabric, forms together with the hook and loop fastening element 9 of the abrasive element 2 a fastener device. By means of this fastener device, the abrasive element 2 is connected to the abrasive element support 1. The hook and loop fastening elements 9 and 10 are designed to allow passage of particles therethrough so that the grinding particles can move in the radial direction. Because a single centrally arranged intake opening 11 is arranged closer to the axis of rotation than the exit openings 12, a suction effect acting on the grinding particles is generated in the through openings 8 and in the hook and loop fastening elements 9 and 10 by means of an acceleration chamber 13. The grinding particles are transported radially in the direction toward the intake opening 11 and pass through the intake opening 11. From here, the grinding particles move through the acceleration chambers 13 radially outwardly in the direction toward the exit openings 12. The grinding particles therefore travel from the surface 7 to be ground to the exit openings 12 along the path indicated by arrow 14. The arrow 14 is symbolically illustrated in FIG. 2 for one of the through openings 8 and one of the exit openings 12. Similar pathways result for all other through openings 8 of the abrasive element; the grinding particles flow in parallel through the openings 8.
FIG. 4 illustrates the section IV-IV of FIG. 2. In the center of the abrasive element support 1 the intake opening 11 is shown. When the grinding particles flow through this intake opening 11, they reach the acceleration chambers 13. These acceleration chambers 13 are formed by the support surfaces 15 and 16 of the support 1 as well as the acceleration devices 17 in the form of lateral boundaries. The acceleration devices 17 moreover have a radially extending curved geometry and are air-impermeable. They delimit the acceleration chambers 13 and are formed as uninterrupted boundaries in the direction from a radial inner location to a radial outer location. The exit openings 12 are uniformly distributed on the circumference of the abrasive element support 1 and have the shape of a section of a cylinder surface. The curved geometry of the acceleration devices 17 creates a preferred direction 18 for the abrasive element support 1. The suction effect acting in a direction from the surface 7 to be ground to the exit openings 12 of the abrasive element support 1 along the arrow 14 is generated only by the geometry and the rotational movement of the abrasive element support 1. An external suction device is not required for the particles up to this point.
The abrasive element support 1 is surrounded by a collecting device 6 so that the grinding particles exiting from the exit openings 12 cannot return to the surface 7 to be ground. The collecting device 6 is embodied as a plastic hood that remains dimensionally stable even when an external suction device is connected thereto. The collecting device 6 surrounds the abrasive element support 1 such that between the edge 19 of the abrasive element support 1 and the collecting device 6 an annular gap 20 is provided. The annular gap 20 opens into an external channel 21 that is arranged between the support surface 15 and the collecting device 6. The external channel 21 that extends as a circular chamber about the entire support surface 15 has at one location a connecting opening 22. This connecting opening 22 is arranged in the collecting device 6 and enables the connection of a hose 23 that extends to an external suction device. After the grinding particles have moved according to arrow 14 from the surface 7 to be ground to the exit openings 12 because of the action of the self-sucking device of the abrasive element support 1, the particles are guided by the connected external suction device from the exit openings 12 to the connecting opening 22 in direction of the second arrow 24 and reach through hose 23 the external suction device. Accordingly, the grinding particles of surface 7 to be ground are effectively removed because already the abrasive element support 1 as a result of its self-sucking device in the form of a radial fan device removes by suction the grinding particles up to the edge 18 of the abrasive element support 1. In prior art grinding devices, the transport of the grinding particles along the path of arrow 14 was effected also by the external suction device. An external suction device is needed in accordance with the present invention only for the transport of the grinding particles along the path of arrow 24. The self-sucking device of the abrasive element support 1 ensures the transport of the grinding particles along the path of arrow 14.
FIG. 5 shows a second embodiment of the abrasive element support 1 with attached abrasive element 2. In this embodiment, the acceleration chamber 13 has air deflecting means in order to guide the grinding particles according to arrow 14 not only radially outwardly but also in a vertical direction, i.e., axial direction, away from the surface 7 to be ground. In this way, the self-sucking device of the abrasive element support 1 ensures that the grinding particles are guided already by means of the abrasive element support 1 in the direction of the connecting opening 22 of the collecting device 26. This has the advantage that the collecting device 26 no longer rests, directly or in the form of brushes 25 as in FIG. 2, on the surface 7 to be ground. The risk that grinding particles return to the surface 7 to be ground is minimized by means of the air deflecting means of the acceleration chamber 13 designed as shown. The movement of the grinding particles has an axial component relative to the axis of rotation 5 of the abrasive element support 1 already when exiting from the exit openings. Accordingly, the collecting device 26 can end at a distance above the plane of the fastening surface of the abrasive element support 1. It does not contact the surface 7 to be ground. This has the advantage that a person working with the abrasive element support 1 and the collecting device 26 designed as described can freely view the surface 7 to be ground. Accordingly, the person can evaluate the grinding result instantly. Also, the axial component of the movement of the grinding particles has the advantage that the path in the direction toward the external suction device is shortened.
FIG. 6 shows a third embodiment with a conventional abrasive element holder 27 without self-sucking device but provided with a hook and loop fastening element 28. A further hook and loop fastening element 29, provided on the abrasive element support 1 that is embodied as a self-sucking attachment 30, together with the hook and loop fastening element 28 of the abrasive element holder 27 form a fastener device 28, 29. In this way, the self-sucking attachment 30 is connected to the abrasive element holder 27. For strengthening this connection, an attachment element 31 in the form of a screw is provided. For fixation of the position of the self-sucking device 30 on the abrasive element holder 27, the self-sucking attachment 30 has a positioning arrangement 32. In this embodiment, a circumferential projection of the self-sucking attachment 30 provides the positioning arrangement 32. With this measure it is ensured that the self-sucking attachment 30 is fixedly connected to the abrasive element holder 27 and is fixed in the radial direction. The abrasive element holder 27 is connected by an additional fastening element 33 in the form of a thread to the drive shaft.
The function of the abrasive element support 1 as a self-sucking attachment 30 is similar to that disclosed in connection with FIGS. 2 and 5. The self-sucking attachment 30 effects by means of its rotational movement or rotational and translatory movement that the grinding particles are moved away from the surface 7 to be ground through the passage openings 8 of the abrasive element 2 and through the fastening elements 9, 10 into the acceleration chamber 13 in the direction of arrow 14. They exit the acceleration chamber 13 through the exit openings 12. The acceleration chamber 13 of the embodiment of FIG. 6 can be provided with air deflecting means as those illustrated in FIG. 5. In this way, the grinding particles can also be moved in the axial direction away from the surface 7 to be ground. The grinding particles, after they have exited the exit openings 12, can also be transported farther by means of an external suction device and then collected.
While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

Claims

1. An abrasive element support having an axis of rotation and a fastening surface for attachment of an abrasive element, wherein the abrasive element support is configured as a self-sucking device.

2. The abrasive element support according to claim 1, wherein the self-sucking device is configured as a radial fan device.

3. The abrasive element support according to claim 2, wherein the fastening surface has a fastening element allowing passage of grinding particles in a direction parallel to the fastening surface.

4. The abrasive element support according to claim 2, wherein the radial fan device has at least one intake opening and at least one exit opening, wherein the at least one intake opening is arranged closer to the axis of rotation than the at least one exit opening, wherein the at least one intake opening and the at least one exit opening communicate through at least one acceleration chamber of the radial fan device, wherein the at least one acceleration chamber has at least one acceleration device that extends in a radial direction.

5. The abrasive element support according to claim 4, wherein the at least one acceleration device forms an uninterrupted boundary delimiting the at least one acceleration chamber.

6. The abrasive element support according to claim 4, wherein the at least one acceleration device is air-impermeable.

7. The abrasive element support according to claim 4, wherein a sum of surface areas of the at least one exit opening is at least as large as a sum of surface areas of the at least one intake opening.

8. The abrasive element support according to claim 4, wherein several of the at least one exit opening are provided and are uniformly distributed about a circumference of the abrasive element support.

9. The abrasive element support according to claim 4, wherein the at least one acceleration chamber comprises a deflecting means.

10. The abrasive element support according to claim 9, wherein the deflecting means are air deflecting means imparting to the grinding particles an exit direction when exiting from the at least one exit opening such that the exit direction has an axial directional component.

11. The abrasive element support according to claim 4, wherein the radial fan device has only one of the at least one intake opening and wherein the intake opening is arranged radially centrally within the radial fan device.

12. The abrasive element support according to claim 1, wherein the fasting surface of the abrasive element support has a hook and loop fasting element.

13. The abrasive element support according to claim 1, further comprising a collecting device.

14. The abrasive element support according to claim 13, wherein the collecting device is arranged at a spacing from the plane of the fastening surface of the abrasive element support.

15. The abrasive element support according to claim 1, configured as a self-sucking attachment.

16. The abrasive element support according to claim 15, wherein the self-sucking attachment has a contact surface configured to attach the self-sucking attachment to an abrasive element holder.

17. The abrasive element support according to claim 15, wherein the contact surface has a hook and loop fastening element.

18. The abrasive element support according to claim 15, wherein the self-sucking attachment has a positioning arrangement.

19. An abrasive element support arrangement comprising:

an abrasive element support;

an abrasive element;

wherein the abrasive element support has an axis of rotation and a fastening surface for fastening the abrasive element thereto;

wherein the abrasive element support is configured as a self-sucking device;

wherein the abrasive element has through openings communicating with the self-sucking device.

20. The abrasive element support arrangement according to claim 19, wherein the abrasive element support and the abrasive element are connected to one another by a hook and loop fastener device that is comprised of a first fastening element connected to the abrasive element support and a second fastening element connected to the abrasive element, wherein the self-sucking device has intake openings and wherein the through openings communicate with the intake openings through the hook and loop fastener device allowing passage of grinding particles in a radial direction.

21. The abrasive element support arrangements according to claim 19, wherein the self-sucking device is connected to an external suction device.

22. A method for removing grinding particles from a grinding surface of an abrasive element provided on a rotating abrasive element support, the method comprising the steps of:

configuring the abrasive element support as a self-sucking device and removing grinding particles from the grinding surface with the self-sucking device.

23. The method according to claim 22, wherein the self-sucking device moves the grinding particles first in a first layer radially inwardly in the direction toward at least one intake opening and moves the grinding particles, after having exited from the at least one intake opening, in a second layer radially outwardly.