GRINDING MACHINE FOR GRINDING A SURFACE OF A WORKPIECE

Abstract

The invention relates to a grinding machine for grinding a surface of a workpiece, wherein the grinding machine comprises a plurality of grinding elements (2) and at least one drive device, by means of which the plurality of grinding elements (2) can be set in oscillatory motion, wherein the grinding machine comprises at least two supporting structures (4), on which at least one grinding element (2) is arranged and which can be moved in an oscillatory manner in directions opposite each other by the at least one drive device.

Description

The invention relates to a grinding machine for grinding a surface of a workpiece, wherein the grinding machine comprises a plurality of grinding elements and at least one drive device, by means of which the plurality of grinding elements can be brought into an oscillating motion.

A grinding machine of this type is known, for example from EP 1 175 961 A2.

Currently, a very wide range of grinding machines are used to machine workpiece surfaces, for example made of wood. The workpiece is customarily conveyed through the grinding machine on a conveying device, with the surface that is to be machined generally facing upward. In this way, the workpiece is conveyed through beneath the grinding elements, coming into contact with the latter. The grinding elements may, for example, be in the form of wire cup brushes or grinding belts; the latter are generally configured in the form of endless grinding belts which revolve around a plurality of diversion rollers.

To obtain the best possible grinding appearance, it is known from the prior art to impart an oscillating motion, often running transversely to the conveying direction along which the workpiece is conveyed through the grinding machine, to the plurality of grinding elements. In this way, the grinding traces of different grinding elements overlap one another on the surface of the workpiece, resulting overall in a more homogeneous grinding appearance.

To allow production to be as cost-effective and economical as possible, it is of considerable interest to be able to machine, in particular grind the surface of, the largest possible number of workpieces within a predetermined period of time. This means that not only should the conveying speed at which the workpiece is conveyed through the grinding machine be selected to be as high as possible, but also the oscillating motion of the plurality of grinding elements should achieve the highest possible oscillation frequency, so that the grinding traces of different grinding elements overlap one another as often as possible. The limit to these movements is generally achieved at the point at which the quality of the grinding results deteriorates.

In the grinding machine described in EP 1 175 961 A2, the individual grinding elements are configured as wire cup brushes, of which for example eight are disposed on a carrying frame which is moved to and fro in oscillating fashion together with the rotary drive. The individual grinding brushes can be set in rotation about their longitudinal axis by means of the rotary drive.

One disadvantage is that the components that are to be moved have a relatively high mass. In total, the carrying frame, the wire cup brushes disposed thereon and the rotary drive, together with any force-transmission means which may be present, have to be set in the quickest possible reciprocating motion. These large masses which have to be accelerated and decelerated very quickly lead firstly to a high energy outlay and secondly to high mechanical stresses on the bearings used for the individual components. Moreover, for example the machine bed and the entire mechanical structure of the grinding machine are also subject to considerable vibrations, which leads to mechanical wear and thus to a reduced durability and operating life of the grinding machine.

The invention is therefore based on the object of further developing a grinding machine in such a way that the grinding result remains of a high quality while the stresses on the structure of the machine and the energy outlay are reduced.

The invention achieves this object by means of a grinding machine for grinding a surface of a workpiece, wherein the grinding machine comprises a plurality of grinding elements and at least one drive device, by means of which the plurality of grinding elements can be brought into an oscillating motion, wherein the grinding machine is distinguished by the fact that the grinding machine has at least two carrying structures, on each of which at least one grinding element is disposed and which are movable in oscillating fashion in opposite directions by means of at least one drive device.

With this configuration, the grinding elements continue to be set in oscillating motion, the direction of which is advantageously transverse to a conveying direction along which the workpieces are conveyed through the grinding machine. In this way, a high-quality grinding result is achieved. However, since the grinding elements are disposed on at least two carrying structures, which can be moved in oscillation in opposite directions, the mass and inertia forces generated for the oscillating motion as a result of the acceleration and deceleration of the respective carrying structures are compensated for. If the carrying structures to be moved, together with the grinding elements located thereon, are equal in terms of mass, these forces cancel one another out, so that there are no, or at least no significant mechanical stresses on the machine.

Preferably, the at least one drive device has a pivot element, on which, at two different positions, the at least two carrying structures are disposed in such a manner that they are movable in opposite directions by means of an oscillating pivoting movement of the pivot element. It has proven particularly advantageous if the pivot element is a drive wheel on which the carrying structures are disposed, in particular in articulated fashion, at two opposite positions. The pivot element is set in an oscillating pivoting motion. This means that the pivot element is initially pivoted through a defined angle in one direction before being pivoted through the same angle in the opposite direction. In this way, through multiple repetition, an oscillating pivoting motion is generated. If the two carrying structures are then disposed at different positions on this pivot element, in particular in articulated fashion, this pivoting motion of the pivot element can be converted into a linear oscillating motion. In particular if the two carrying structures are disposed at two opposite positions, the result is that the linear motions of the two carrying structures are exactly opposed to one another. The two positions at which the carrying structures are arranged, in particular in articulated fashion, are in particular preferably located opposite one another with respect to the pivot axis of the pivot element.

Advantageously, the drive device has a rotary element on which the carrying structures are disposed by means of a conversion device, in such a manner that the conversion device converts a rotary motion of the rotary element into opposite transverse movements of the carrying structures. The rotary element may, for example, be configured in the form of a circular disk, in which case, for example, a conversion device is arranged on each of the two opposite sides of these disks. These conversion devices are connected to the carrying structures. If the rotary element is then set in rotation, the conversion devices, which may be disposed on the sides of the rotary element, for example by means of respective bolts, are also moved. The conversion devices are configured in such a way that they convert the rotary motion of the rotary element into transverse oscillating movements. This can be achieved, for example, by means of connecting rods disposed on one another, as is known, for example, in the case of steam locomotives. If the two conversion devices, of which it is advantageous to provide one for each carrying structure, are positioned at different positions of the respective side face of the rotary element, it is particularly easy to ensure that the transverse movements of the carrying structures, brought about by the respective conversion devices, run in opposite directions and at the same time oscillate.

As a result, the design of the drive device is significantly simplified, since it is no longer necessary to provide a pivot element that has to be accelerated and decelerated. Instead, the rotary element can be set in continuous rotation, thereby reducing the design outlay.

The grinding elements are preferably wire cup brushes which are mounted rotatably about an axis of rotation. It has proven particularly advantageous if at least one rotary drive is arranged on each carrying structure, in order to rotate the wire cup brushes disposed on the respective carrying structure about the axis of rotation. If the rotary drive for the wire cup brushes of a carrying structure is disposed on the carrying structure itself, its position relative to the wire cup brushes does not change even during the oscillating motion of the carrying structures. This has the result that there is no need to use complicated force-transmission means in order, for example, to take account of a varying distance between the rotary drive and the wire cup brushes. In this way, the design of the grinding machine is made simpler and can be of more compact configuration, i.e. takes up less space. Since it is preferable to arrange a rotary drive on each carrying structure, which particularly advantageously have the same structural configuration, the overall mass which has to be set in an oscillating motion is increased, but the forces acting on the equipment and in particular on the drive device on account of the accelerated and decelerated mass cancel one another out. Although greater masses therefore have to be moved, the mechanical stresses on the machine and in particular the supporting parts of the grinding machine remain unchanged through the acceleration and deceleration.

Advantageously, the rotary drive is disposed in such a manner that it rotates adjacent wire cup brushes in opposite directions. As an alternative, it is, of course, also conceivable for the rotary drive to rotate adjacent wire cup brushes in the same direction. Combinations of these two configurations are also possible. By suitably selecting the force-transmission means from the rotary drive to the wire cup brushes, it is possible to achieve any desired configuration of the directions of rotation of the individual wire cup brushes. Different configurations at the different carrying structures are also possible.

Preferably, the carrying structures are mounted in such a manner as to be displaceable along a guide. In this way, the drive device has only to apply the force required for the movement and the deceleration of the parts that are to be moved, in particular the carrying structures with the grinding elements disposed thereon.

The drive device does not need to supply support and bearing for the parts that are to be moved. In a preferred configuration, the carrying structures can be pulled out of the grinding machine by being displaced along the guide. For this purpose, it may be useful to release the carrying structures from the force-transmission means which transmit the force applied by the drive device to the carrying structures. This is suitable in particular if, for example, the carrying structures need to be cleaned or undergo maintenance operations or grinding elements need to be repaired or replaced. In this case, the structure described here makes it particularly simple, quick and therefore cost-effective to fit the grinding machine for example with different grinding elements, in order to achieve different grinding results if appropriate for other workpieces or other materials.

The carrying structures may advantageously be displaced so far along the guide that they at least over a large part but advantageously over their entire length project out of, for example, a casing of the grinding machine. However, it is important only that they be easily accessible in this displaced state, so that maintenance, cleaning or refitting work to be carried out can be carried out easily. The grinding machine may have a casing which, for example, has closeable flaps and/or doors, behind which the guidance of the carrying structures is concealed. This increases the working safety, since this prevents, for example, people from being able to enter or reach into the area of operation of the individual grinding elements when the grinding machine is operated.

The respective carrying structure need not be completely removed from the grinding machine. It is often sufficient for it to be displaced into a position in which the individual component of the carrying structure and the components disposed on the carrying structure are easily accessible.

In a preferred configuration of the grinding machine, the same number of grinding elements are located on each carrying structure. In this way, the most exact possible matching of masses of the elements to be moved is achieved, so that the mass forces acting on the equipment are further reduced.

Preferably, the grinding machine has a conveying device for conveying the workpiece in a conveying direction, and the carrying structures are displaceable in a direction perpendicular to this conveying direction, preferably independently of one another. This direction will generally be the vertical direction, in order in this way to be able to react, for example, to workpieces of different thicknesses. If the carrying structures are supported for example by the guide means, it is particularly simple to configure the carrying structures to be vertically displaceable by simply making the guide means displaceable. If the carrying structures are configured to be displaceable independently of one another, different grinding elements may be disposed on different carrying structures, in order in this way, for example, to allow coarse-grinding and precision-grinding to be carried out in succession. The grinding elements may in this case have a different thickness or height, so that the respective carrying structure must be arranged at different distances from the conveying device. Of course, other exemplary embodiments are also conceivable, in which different distances of the different carrying structures relative to the conveying device are advantageous.

An exemplary embodiment of the present invention is explained in more detail below with the aid of the accompanying drawings, in which:

FIG. 1 shows a schematic plan view of an excerpt from a grinding machine according to a first exemplary embodiment of the present invention,

FIG. 2 shows a schematic side view of a grinding machine according to a further exemplary embodiment of the present invention,

FIGS. 3a+3b show the schematic arrangement of force-transmission means of a grinding machine according to a further exemplary embodiment of the present invention,

FIG. 4 shows a schematic sectional illustration through a grinding machine according to an exemplary embodiment of the present invention, and

FIG. 5 shows a further schematic plan view of an excerpt of a grinding machine.

FIG. 1 shows a schematic plan view of a part of a grinding machine. The figure shows a multiplicity of grinding elements 2, which are configured as wire cup brushes. They are disposed on two carrying structures 4, which may be configured as carriages. A rotary drive 6 is located on each carrying structure 4 and sets the grinding elements 2 in rotation on their respective carrying structure 4 by way of force-transmission means 8.

Each carrying structure 4, by way of the right-hand end as seen in FIG. 1, is secured to a pivot element 10, which in the exemplary embodiment shown is configured as a drive wheel. At two opposite positions 12, the carrying structures 4 are connected to the pivot element 10, in the exemplary embodiment shown by way of tapping points. The pivot element is then pivoted in oscillating fashion, this oscillating pivoting motion being converted into an oscillating linear motion as indicated by the double arrow 14. The particular configurations of the tapping points by which the carrying structures 4 are secured to the positions 12 of the pivot element 10 allow in fact exclusively linear oscillating movements to be carried out by the carrying structures 4.

FIG. 2 shows a schematic side view of the equipment illustrated schematically in FIG. 1. The grinding elements 2 are configured as wire cup brushes and project downwards in the direction of the workpiece. The two rotary drives 6 are illustrated offset with respect to one another, since the two carrying structures 4, which in the view shown are arranged one behind the other, are also positioned offset with respect to one another. The pivot element 10 is illustrated in the right-hand part of FIG. 2.

The carrying structures 4 are mounted by means of a guide 16, which is only schematically illustrated and along which they are configured to be displaceable. The guide itself is mounted by way of two length-adjustable supports 18, the length of which is adjustable. In this way, the distance between the grinding elements 2 and a workpiece or a conveying device on which the workpiece is conveyed can be adjusted. In this way, it is also possible to use a separate guide 16 for each carrying structure 4, said guide having special supports 18, so that the height of the various carrying structures 4 can be adjusted independently. If appropriate, the articulation of the carrying structures 4 on the pivot element 10 must be taken into suitable consideration here.

FIGS. 3a and 3b each show schematic plan views of grinding elements 2, which in their upper part have gearwheels 20, by means of which they mesh with the force-transmission means 8. The latter may, for example, be configured in the form of a toothed belt or a chain. In the exemplary embodiment shown in FIG. 3a, adjacent grinding elements 2 are operated in opposite rotational directions, while in the exemplary embodiments shown in FIG. 3b all the grinding elements 2 are rotated in the same direction. For this purpose, diversion rollers 22, which ensure a sufficient tension of the force-transmission means 8, are present between each pair of grinding elements 2.

FIG. 4 shows a side view along the longitudinal extent of the carrying structures 4. The figure shows the grinding elements 2 and the carrying structure 4, which in the present case is configured as a carriage. The carrying structure 4 engages in guides 16, which in the exemplary embodiment shown are suspended from a carrier 24. As illustrated in FIGS. 3a and 3b, the gearwheels 20 mesh with the force-transmission means 8, which is not shown in FIG. 4. The supports 18, which support the carrier 24, are again vertically adjustable, in order to be able to adjust for different thicknesses of the workpiece. Moreover, a further height-adjustment frame 26 may be present. The height adjustments of the height-adjustment frame 26 and of the supports 18 ensure that it is possible to react to workpieces of different thicknesses and grinding brushes of different lengths. In particular if the various carrying structures can be vertically adjusted separately from one another, it is also possible to use different grinding brushes for different carrying structures 4.

The particular feature of the grinding machine presented here is the drive which leads to the oscillation of the two carrying structures 4. Since the carrying structures 4 always have to be moved in opposite directions, accelerated and decelerated, particularly if the masses of the two carrying structures 4 together with the elements located therein are identical, the mass forces and inertia forces cancel one another out. If the masses are not exactly identical, the mass forces and inertia forces are merely reduced. This particular drive form allows the oscillation speeds and frequencies which are appropriate to the particular application to be made as high as desired without disruptive mass forces acting externally on the machine structure of the grinding machine.

FIG. 5 shows the situation in which the carrying structures 4 are displaced to the left, in the direction indicated by the arrows 28, along the guides, which are not illustrated in FIG. 5. For this purpose, first of all the pivot element 10 is moved into the neutral position, and then the connection between the pivot element 10 and the carrying structures 4 is released. Then, the carrying structures 4 can be displaced and moved to the left over the guide and in this way, for example, removed from the grinding machine in order to fit different grinding elements 2, to clean the equipment, to carry out maintenance or to carry out other forms of checks.

LIST OF DESIGNATIONS

• 2 Grinding element
• 4 Carrying structure
• 6 Rotary drive
• 8 Force-transmission means
• 10 Pivot element
• 12 Position
• 14 Double arrow
• 16 Guide
• 18 Support
• 20 Gearwheel
• 22 Diversion roller
• 24 Carrier
• 26 Height-adjustment frame
• 28 Arrow

Claims

1. A grinding machine for grinding a surface of a workpiece, comprising:

a plurality of grinding elements;

at least one drive device which is configured for bringing the plurality of grinding elements into an oscillating motion; and

at least two carrying structures on each of which at least one grinding element of the plurality of grinding elements is disposed, and wherein the at least two carrying structures are movable in oscillating fashion in opposite directions by the at least one drive device.

2. The grinding machine as claimed in claim 1, wherein the at least one drive device has a pivot element on which, at two different positions, the at least two carrying structures are disposed in such a manner that they are movable in opposite directions by an oscillating pivoting movement of the pivot element.

3. The grinding machine as claimed in claim 1, wherein the at least on drive device has a rotary element on which the at least two carrying structures are disposed by a conversion device in such a manner that the conversion device converts a rotary movement of the rotary element into opposite transverse movements of the at least two carrying structures.

4. The grinding machine as claimed in claim 1 wherein one or more of the plurality of grinding elements are wire cup brushes which are mounted rotatably about an axis of rotation.

5. The grinding machine as claimed in claim 4, further comprising at least one rotary drive is disposed on each of the at least two carrying structures, wherein the at least one rotary drive one each of the at least two carrying structures rotates the wire cup brushes disposed on the at least two carrying structures about the axis of rotation.

6. The grinding machine as claimed in claim 5, wherein the at least one rotary drive is disposed such that it rotates adjacent the wire cup brushes in opposite directions.

7. The grinding machine as claimed in claim 1 wherein the at least two carrying structures are mounted so that they are displaceable along a guide.

8. The grinding machine as claimed in claim 7, wherein the at least two carrying structures are pulled out of the grinding machine by being displaced along the guide.

9. The grinding machine as claimed in claim 1 wherein a same number of grinding elements of the plurality of grinding elements is arranged on each of the at least two carrying structures.

10. The grinding machine as claimed in claim 1 further comprising a conveying device for conveying the workpiece in a conveying direction, and the at least two carrying structures are displaceable in a direction perpendicular to the conveying direction.

11. The grinding machine as claimed in claim 10 wherein each of the at least two carrying structures are displaceable in the direction perpendicular to the conveying direction independently of one another.