Patent Application
20180085892
The invention relates to a grinding machine for grinding a surface of a workpiece, having at least one transport device for transporting a workpiece in a transport direction through the grinding machine, and having at least one grinding tool, wherein the grinding tool has at least one brush with grinding bristles.
Grinding machines of said type have long been known from the prior art and are used for a wide variety of different surfaces. For example, it is known for wood surfaces or metal surfaces to be machined using such grinding tools, for example grinding brushes or disk brushes, and thus, for example, for metallic components to be deburred and rounded at the edges, or for visually appealing surface effects to be generated in the surface of the workpiece. In particular in the case of grinding brushes being used, these normally extend over the entire width of the transport device, which may for example be a conveyor belt. The workpieces to be machined are normally not adapted to the width of the transport device, but have an extent in said direction which is smaller than that of the transport device and thus also smaller than the width of the grinding brush. This inevitably means that, during the grinding of the surface of a workpiece, not all of the grinding bristles of the brush come into contact with the workpiece. In particular, the grinding tool is normally more heavily loaded in the central region over the width of the grinding tool than in the edge regions.
From the prior art, efforts have been known to be made to counteract this effect, which leads to more intense wear of the grinding tool in the center, for example by virtue of the workpieces to be ground being guided through the grinding machine at different positions, such that grinding bristles of the brush which are otherwise not heavily loaded can also come into contact with a surface of the workpiece. Irregular wear of the grinding tool, and in particular of the grinding brushes, nevertheless occurs.
To be able to grind the desired pattern into the surface of a workpiece, or in order to specifically avoid particular grinding patterns and produce a surface which is formed with the least possible grinding patterns, it is however advantageous, or even necessary, for the grinding pressure with which the grinding bristles come into contact with the surface to be temporally and spatially constant. Otherwise, loading of the surface of the workpiece with varying intensity would have the effect that it is not possible to generate homogeneous grinding marks on said surface. The deburring or rounding of edges of metallic workpieces, for example, also necessitates that the contact pressure of the grinding tool on the surface of the workpiece be not only known and reproducible but in particular temporally and spatially constant. Therefore, grinding tools in the form of grinding brushes or disk brushes are nowadays removed from the grinding machine after a certain operating duration and are either exchanged or for example sent to the manufacturer of the grinding tools. There, less heavily worn grinding bristles are shortened in order to ensure that a homogeneous grinding bristle length is again present on the grinding brush or disk brush, and thus a homogeneous contact pressure is again ensured. This is time-consuming and expensive and leads to relatively long time periods in which the grinding machine cannot be used. This is the case even if, during the time in which a grinding tool is dismounted and for example sent away, another grinding tool is present in the grinding machine.
The invention is therefore based on the object of further developing a grinding machine such that it can be used more efficiently and can be operated with less downtime, and at the same time the grinding tool can be used for as long as possible.
The invention achieves the stated object by means of a grinding machine as per the preamble of claim 1, which is characterized in that it has a leveling unit.
A leveling unit is a functional unit within the grinding machine which, for example in a special operating mode of the grinding machine, serves to restore the concentricity and the straightness of the grinding tool, in particular of a brush roller. This special operating mode may be present for example in the form of a predetermined program stored in an electronic data memory, which program can be accessed and executed by an electronic controller of the grinding machine. Therefore, with a grinding machine according to the invention, it is only seldom necessary for the grinding tool itself, in particular the brush roller, to be removed from the grinding machine. This is necessary only when the brush roller has to be fully exchanged. If it is identified that the contact pressure of the grinding tool is no longer constant over the width of the brush roller or over the spatial extent of individual disk brushes, the special operating mode of the grinding machine is for example initiated manually. In this case, the concentricity and the straightness of the brush roller are restored by means of the leveling unit. This can be performed within a few minutes, such that, after the end of this time period, when the program stored for example in the electronic data memory has been fully executed, the grinding machine is again fully ready for use and provides virtually optimum grinding results.
The leveling unit advantageously has at least one leveling tool for shortening at least some of the grinding bristles.
During grinding using the grinding machine, individual grinding bristles of the grinding tool are more heavily loaded than others, and in particular wear more intensely, such that they have for example a shorter length than grinding bristles arranged for example at the edge of the grinding tool. To be able to ensure an optimum grinding result, it is now advantageously the case that all grinding bristles of the grinding brush, in particular of the brush roller, are shortened to one length, such that a homogeneous grinding re-suit is achieved. It is self-evidently also possible for a non-homogeneous length of the individual grinding bristles relative to one another to be set by means of the leveling unit, by virtue of grinding bristles in different regions of the grinding tool being shortened to different lengths, if this is desired and advantageous.
The leveling tool may for example be composed of a multiplicity of cutting elements which are for example arranged over the width of the grinding tool and which can thus shorten the grinding bristles of the grinding means simultaneously over the entire width. Here, the leveling tool may be formed as one large cutting element, for example a blade or shear which extends over the entire width, or may be composed of a multiplicity of different individual elements arranged adjacent to one another, by means of which it is then possible for different lengths of the grinding bristles to be set at different points of the grinding tool.
As an alternative to this, it has proven to be advantageous for the leveling tool to be arranged so as to be displaceable in a direction perpendicular to the transport direction. The leveling tool itself can then be of spatially small form, in particular with a relatively low inherent weight, such that the outlay in terms of apparatus required for the leveling unit in a grinding machine of said type is considerably reduced. In particular in the case of a brush roller, it is advantageous if the leveling unit is movable in a direction perpendicular to the transport direction, that is to say from left to right and vice versa in a grinding machine, and can thus move to any point over the width of the brush roller. Since the brush roller can be set in rotation in any case, it is possible in this way for all of the bristles of the brush roller to be shortened to the desired length.
The at least one grinding tool and/or the leveling tool is preferably arranged so as to be height-adjustable. In numerous known grinding machines, the grinding tool is height-adjustable in any case in order to be able to make the spacing between the grinding tool and the transport device variable and thus adjustable to different thicknesses of work-pieces to be machined. In this case, it is advantageous if the leveling tool is formed so as not to be height-adjustable relative to the transport device, such that a height adjustment of the grinding tool simultaneously results in a change in the spacing between the grinding tool and the leveling tool. It is self-evidently nevertheless also possible for the leveling tool to be designed to be height-adjustable, as long as the grinding tool and leveling tool are height-adjustable independently of one another. Only in this way can the spacing be changed and thus the length to which the grinding bristles can be shortened by the leveling tool adjusted.
The grinding tool preferably has a multiplicity of disk brushes which run in encircling fashion along an encircling contour, wherein the at least one leveling tool is arranged adjacent to the transport device. If the grinding tool has a brush roller, the arrangement of the leveling tool above said brush roller has proven to be advantageous because the bristles point in said direction in any case when the brush rotates. However, if disk brushes are used, the situation is different. In the case of a disk brush, it is generally the case that all of the grinding bristles are directed toward the workpiece, and the axis of rotation about which the disk brush rotates or is pivoted is perpendicular to the transport plane of the transport device. In this embodiment, too, it is possible for the leveling tool to be arranged above the disk brushes. In this case, it would be necessary, if the special operating mode of leveling is implemented, for the orientation of the disk brushes to be changed, and for the grinding bristles of the disk brushes to be oriented in the direction of the leveling tool. Although this is possible, it results in increased outlay in terms of apparatus and technical equipment.
A structurally more simple solution is possible if the disk brushes, which in addition to the rotation about their axis of rotation also revolve on a revolving contour, are in this case also moved in a region adjacent to the transport device, such that there are sections of the revolving contour in which the disk brushes and the grinding bristles of the disk brushes cannot come into contact with a workpiece situated on the transport device. The at least one leveling tool can be arranged in a particularly straightforward and space-saving and thus technically cumbersome manner in said regions, in which for example reversal points and curves of the revolving contour are situated. In this case, it is advantageous for multiple leveling tools to be arranged on both sides of the transport device.
In a preferred embodiment, the grinding machine has a measuring device for measuring the length of the grinding bristles. This may be performed for example contactlessly, in particular by means of light barriers, or by means of pressure or contact sensors, which measure whether particular points still come into contact with the revolving grinding bristles. Here, too, it has proven to be advantageous for the measuring device to be designed to measure the length of the grinding brushes at different points of the grinding tool. This means in particular that the length of the grinding bristles can be measured at different positions over the width of the grinding tool. The grinding machine furthermore has an electrical controller which is designed to bring the leveling tool into engagement with the grinding bristles and thereby shorten the bristles if a length difference between different bristles exceeds a predetermined threshold value. If, on the basis of the measurement results from the measuring device, the electrical controller identifies for example that a length difference between the length of the bristles in the central region of the grinding brushes and the bristles in the outer region of the grinding brush exceeds a predetermined threshold value, the electrical controller can automatically activate or initiate the operating mode of leveling, and thus ensure that the leveling tool is brought into engagement with the respective grinding bristles, such that the length difference between the individual bristles is reduced or adjusted to the desired dimension. As an alternative to this, the electrical controller may also trigger a display or alarm device such that an operator of the grinding machine recognizes that shortening of the grinding bristles is necessary.
The predetermined threshold value is advantageously dependent on the length of the grinding brushes. If the grinding brushes are already relatively short, for example because they have been shortened several times, it may be expedient for the predetermined threshold value to be selected to be relatively low, in order to achieve that a relative change in length remains as small as possible. However, if the length of the brushes is still relatively large, for example in the case of a brush roller which has been newly inserted into the grinding machine, larger length differences are by all means tolerable.
The grinding machine advantageously has an imbalance measuring device for measuring an imbalance of the grinding tool. In this way, too, it can be identified whether some or all of the grinding bristles have to be shortened.
The grinding machine preferably has a housing in which the grinding apparatus is arranged, wherein the transport belt is removable from the grinding machine, wherein the grinding apparatus and/or the grinding table do not have to be removed from the grinding machine.
As is conventional, the transport belt is not subjected to unduly heavy loads, such that a change of the transport belt during the operation of a grinding machine is a service action that has to be performed only seldomly. As is conventional, the grinding table and possibly additionally the grinding apparatus, that is to say the grinding means itself, must be removed from the housing of the grinding machine. The grinding table must subsequently be dismantled to such an extent that the transport belt is made accessible.
By means of this embodiment of the grinding machine, it is now made possible for the transport belt to be exchanged and removed from the grinding machine without the grinding apparatus and/or the grinding table having to be removed from the grinding machine. The exchange of the transport belt is thereby greatly simplified. If, for example, it is the intention for metallic surfaces composed of different metals to be ground one after the other, it is now possible, rather than the often cumbersome and time-consuming cleaning of a transport belt, to simply exchange the respective grinding belt, such that it is no longer necessary to remove particles of grinding dust or grinding chips adhering to the grinding belt. It is thus for example possible for different transport belts to be provided for different metals, which transport belts can be inserted into the grinding machine in accordance with the desired metal type to be ground. As an alternative to this, it is self-evidently also possible for a removed transport belt to be cleaned with the required care in order to be made ready for subsequent use with a different metal type. With the embodiment of the grinding machine according to the invention, this no longer has the result that it is no longer possible to grind workpieces during said period of cleaning of the transport belt. Rather, one of the transport belts can be cleaned while another transport belt is used in the grinding machine.
The housing preferably has an opening flap which can be placed into an open state and into a closed state, wherein the transport belt is accessible when the opening flap is situated in the open state. The opening flap is advantageously a door or a double door which is arranged such that the housing can be easily opened. When the housing is open, that is to say when the opening flap is situated in the open state, the transport belt can be easily removed from the grinding machine. The grinding table is advantageously fastened to at least one detachably installed support. In particular in the case of relatively large grinding machines or grinding modules, which possibly have more than one grinding apparatus, it is advantageous for the grinding table to be secured by means of at least one support on both sides of the transport belt. On the side on which the transport belt is accessible for example after the opening of the opening flap, it is advantageous if the support can be detached in as simple a manner as possible. This may be achieved for example by means of simple screw connections, which are released for the purposes of exchanging the transport belt. The number, positioning and type of fastenings and the installation of the detachably installed supports are in this case dependent on the size of the grinding machine, on the number of grinding apparatuses used, and on the nature of the grinding process, because these significantly co-determine the intensity of the pressure exerted by the grinding apparatuses on the workpiece and thus also on the transport belt.
The grinding machine advantageously has a suction device by means of which a workpiece lying on the transport belt can be acted on with a negative pressure. In this way, firstly, a holding force on the workpiece is increased, such that, even in the case of relatively high forces being exerted on the workpiece by the grinding apparatus, the workpiece cannot slip or move along the transport belt. Secondly, it is achieved that grinding chips or grinding dust can be suctioned away by the suction device, and thus the contamination and fouling of the interior space of the grinding machine with grinding dust or grinding chips is reduced.
The grinding machine preferably has multiple grinding modules which each have at least one grinding apparatus and one transport belt. Here, it is advantageously the case that each grinding module can be removed from the grinding machine, and for example replaced with another module, separately. In a preferred refinement, each module has at least one opening flap, particularly preferably a door, by means of which a part of the housing belonging to the module can be opened, whereby the transport belt is made accessible.
The grinding machine advantageously has an extraction chamber which is arranged below the transport belt and which has a base which is inclined with respect to the horizontal.
The grinding machine preferably has a suction device by means of which a workpiece lying on the transport belt can be acted on with a negative pressure, wherein the extraction chamber is part of the suction device. The extraction chamber is generally formed as part of the suction device, though may also be used without the possibility of acting thereon with negative pressure. The grinding chips to be discharged or the grinding dust are/is then, by means of the inclined base and the inherent weight of the chips or of the dust, led out of the grinding region of the grinding machine and collected, and can be easily removed.
An extraction chamber arranged below the transport belt is in this case arranged preferably only under that part of the transport belt on which the workpieces are transported through the grinding machine. The transport belt is generally an encircling endless belt which forms a closed contour. The extraction chamber is preferably arranged within said contour, as far as possible directly below the transport belt. For numerous embodiments, it is sufficient here for the extraction chamber to be arranged only in a partial region below the transport belt. Said partial region advantageously corresponds to the region in which the grinding apparatus is arranged above the transport belt. This is the region in which grinding chips and grinding dust are formed, which are to be discharged through the extraction chamber. The base of the extraction chamber advantageously encloses an angle of at least 5°, preferably at least 10°, particularly preferably at least 15°, and at most 30°, preferably at most 25°, particularly preferably at most 20′, with the horizontal. It has proven to be particularly advantageous if the base of the extraction chamber is inclined perpendicular to the transport direction along which the workpiece can be transported by the transport belt. This means that the workpiece is transported along the transport direction, and the inclination extends to the right or to the left therefrom. Grinding dust and grinding chips that are formed as a result of the machining of the surface of the workpiece by means of the grinding apparatus can pass through holes or openings provided in the transport belt into the extraction chamber, from where they can be extracted. This is further simplified, and made more efficient, by means of the inclined base of the extraction chamber. In this way, the remaining fouling of the grinding machine with grinding dust and grinding chips from a metal is considerably reduced, or ideally eliminated entirely.
The extraction chamber is advantageously connected or connectable, at the lower end of the base, to a suction device. Grinding dust and grinding chips can be suctioned out of the extraction chamber by means of said suction device. The base of the extraction chamber is consequently inclined toward said suction device.
The transport belt is advantageously coated with an anti-adhesion coating. The inner side of the extraction chamber, or at least the base of the extraction chamber, is particularly advantageously coated with an anti-adhesion coating. A polymer or a mixture of multiple polymers has proven to be advantageous as material for the anti-adhesion coating. In this way, too, the residual contamination and fouling of the transport belt and of the suction device, in particular of the extraction chamber, are reduced, and thus the outlay for cleaning is also reduced.
The base of the extraction chamber may preferably also be mechanically animated, that is to say in particular caused to vibrate. This may involve regular vibrations, such as for example sound waves, or individual, regularly or irregularly repeating shocks. In this way, chips or dust that have/has collected on the base of the extraction chamber can be moved, such that they/it can be collected and removed, for example extracted.
The grinding machine advantageously has multiple transport belts and multiple suction devices, wherein the suction devices each have an extraction chamber with an inclined base. If the grinding machine is equipped with multiple grinding apparatuses, which may be of different or identical design, it has proven to be advantageous for each of the apparatuses to be arranged in a grinding machine module, which can be exchanged or removed from the grinding machine separately, and in a manner separate from the other modules. For this purpose, it is advantageous if each of the modules, which may for example have one or two grinding apparatuses, has a dedicated transport belt which is responsible only for transporting the workpiece within the grinding machine module. In this way, firstly, a situation is prevented in which grinding chips or grinding dust is carried through the entire grinding machine by an excessively long transport belt, and furthermore, it is made possible for the individual assemblies and modules to be easily exchanged and dismounted, for example for the purposes of cleaning, maintenance or exchange.
The at least one transport belt is advantageously exchangeable without the grinding apparatus having to be removed. For this purpose, it is for example possible for a housing, which surrounds the grinding apparatuses, of the grinding machine to be opened. After any supports that may be present are removed, which supports hold the transport table, which has the transport belt, in position, have been removed, the transport belt can be removed. For this purpose, it is for example necessary for a tensioning device, which is responsible for imparting an adequate tension to the transport belt, to be released. The grinding belt can then be easily removed, without the need for dismantling the grinding machine entirely or for removing a grinding apparatus or a grinding module from the grinding machine.
The grinding machine preferably has a device for determining a radius of a contour of an object with an at least circular-segment-shaped cross section, which device has two abutment surfaces for the abutment of the object and at least one measuring slide, wherein the abutment surfaces are arranged at right angles with respect to one another and the measuring slide is arranged so as to be displaceable along an angle bisector of said right angle, such that the measuring slide is displaceable by virtue of the object being placed against the two abutment surfaces.
The device advantageously has a measuring device for measuring the distance by which the measuring slide is displaced when the object is placed against the two abutment surfaces. In a particularly advantageous refinement, the device has an electrical controller which is designed to determine the radius from the measured distance. The device preferably has a display device which is designed to display the radius and/or the distance by which the measuring slide has been displaced.
This embodiment is based on the realization that an object with a circular-segment-shaped or circular cross section which is arranged with the contour of said cross section against the two abutment surfaces arranged at right angles with respect to one another displaces the measuring slide. The circular-segment-shaped or circular cross section may in this case at least notionally be approximated by a circle with a radius which is to be determined by the device. Here, said circle forms the inscribed circle or inner circle with respect to a square, one corner of which is formed by the point at which the two abutment surfaces bear against one another. Said square may notionally be circumscribed by a circumscribed circle or outer circle, the central point of which is consequently situated at the central point of the inscribed circle and which runs through the contact point, that is to say the “corner”, of the two abutment surfaces. Here, the statements relating to circles, squares or points relate in each case to the cross section through the object which is inserted into the device according to an exemplary embodiment of the present invention.
The difference between the radius of the inscribed circle or inner circle and the radius of the circumscribed circle or outer circle corresponds in this case exactly to the distance by which the measuring slide still stands out from the corner formed by the two abutment surfaces. If it is known how far the measuring slide stands out from said corner without an inserted object, it is easily possible to calculate the size of the difference between the radius of the inner circle and the radius of the outer circle. In this way, it is also possible to determine the radius of the inner circle, which corresponds to the radius to be determined.
The device is advantageously arranged so as to determine the radius of an edge of the workpiece. This is advantageously performed after the workpiece has run along the grinding tool itself and interacted therewith, that is to say after the grinding process. By means of the very simple device for measuring the radius, it is possible in a particularly simple and nevertheless reliable and reproducible manner to determine whether the desired grinding result has been achieved, and the radius of the edge of the workpiece meets the legal or other requirements. For this purpose, it is merely necessary for that edge of the workpiece whose radius is to be measured to be placed against the two abutment surfaces of the device. The radius of the edge can be determined in a particularly simple manner from the distance by which the measuring slide is displaced in the presence of said abutment.
The grinding machine preferably has an actuator which moves the device against the desired edge of the workpiece. This is advantageously performed fully automatically, such that an intervention by operating personnel is not necessary. For this purpose, it may be advantageous if the grinding machine has a position detection device and/or an orientation detection device, by means of which the position and/or orientation of the workpiece on a transport device of the grinding machine can be identified. In this way, an electrical controller of the grinding machine can ensure that the actuator, which may for example be a robot arm, particularly preferably a multiply articulated robot arm, moves the device accurately toward, and places the device accurately against, the desired point of the workpiece to be inspected and the required edge.
A radius determined by means of the device is advantageously used as a control parameter or regulation variable in the electrical controller of the grinding machine. In particular if the determined radius does not satisfy the legal or other regulations, or has an excessively large deviation from a predetermined setpoint value, the workpiece can for example be passed through the grinding machine once again, or can be labeled as a reject or as a workpiece for reprocessing. It is furthermore possible, in particular if the determined radius is too small, that is to say the abrasion effected by the grinding machine is not sufficient to achieve the desired setpoint value, for the contact pressure of the grinding tool against the surface of the workpiece to be increased, and thus for increased grinding abrasion, and thus a larger radius of the edge, to be achieved in the case of subsequent workpieces. This is expedient in particular if multiple workpieces, in particular a large number of workpieces, which have a surface composed of the same material are to be machined and ground in succession.
It has proven to be advantageous for the grinding machine to have multiple such devices. In this way, different edges with possibly different setpoint radii can be measured simultaneously, and in this way the quality control process can be accelerated.
The grinding machine advantageously has an imbalance measuring device for measuring an imbalance of the grinding tool. In this way, too, it can be identified whether some or all of the grinding bristles have to be shortened.
An exemplary embodiment of the present invention will be discussed in more detail below on the basis of the appended drawing. In the drawing:
The grinding tool 2 is mounted on two mountings 6, and is driven by means of a motor 8 and a power transmission belt 10. Said grinding tool is rotatable about a longitudinal axis which runs through the mountings 6.
Above the grinding tool 2, there is situated a leveling tool 12 which, in this case, is a small rotating disk with a relatively sharp edge. Said leveling tool is arranged on a holder 14, in which a drive 16 for the leveling tool 12 is also situated. In the exemplary embodiment shown, the leveling tool 12 is, with the holder 14, movable to the left and to the right along a linear guide 18. In this way, said leveling tool can reach every point along the width of the grinding tool 2.
In the exemplary embodiment shown, the grinding tool 2 and the mountings 6 are mounted in displaceable fashion by a height adjustment means 20. In this way, a spacing between the shell surface 4 of the grinding tool 2 and the leveling tool 12 can be adjusted in continuously variable fashion. An adjustment motor 22 is provided for the height adjustment means 20.
If the height adjustment means 20 is activated and, for example in the illustration shown, the grinding tool 2 is raised relative to the leveling tool 12, and the leveling tool 12 is moved to the right and to the left by means of the linear guide 18, the leveling tool 12 comes into contact with the grinding bristles (not illustrated) situated on the shell surface 4 of the grinding tool 2 and shortens said bristles to the desired length. Owing to the centrifugal force of the rotating grinding tool, it is ensured that, in the embodiment shown, all of the grinding bristles are shortened to the same length.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 117 994.9 | Sep 2016 | DE | national |
