Patent Application
20210008682
Exemplary embodiments of the present invention relate to a method for partially grinding a surface and a grinding device for carrying out the method.
After checking a surface, which is finish-painted in particular, by means of a sensor system, a recognized flaw has heretofore been manually treated, for which purpose a handheld grinding machine is used, having a grinding disk on which an abrasive sheet is held.
The mounting of the abrasive sheet on the grinding disk is typically achieved by a hook-and-loop connection, wherein the pairing grinding disk/abrasive sheet is formed accordingly on the sides thereof facing toward one another.
Another type of fastening of the abrasive sheet on the grinding disk is achieved by a self-adhesive adhesive bond.
A further type of mounting the abrasive sheet on the grinding disk is performed by suction, for which purpose the grinding machine is connected to a suction device.
To remove the flaw, i.e., to match it with the adjacent unflawed regions, an abrasive sheet having a very fine grain is used, wherein the grinding procedure per se is performed in a punctiform manner, but using orbital, rotating, and/or vibrating movements.
A whole array of required work steps results from the manual processing of the flaw, which oppose cost optimization.
Thus, changing the abrasive sheet is relatively time-consuming and thus costly, above all because the abrasive sheet has to be fastened exactly, centrally, and having the correct side on the grinding disk.
An application of the handheld grinding machine having the associated grinding disk and the abrasive sheet fixed thereon not parallel to the surface is particularly subject to error and requires an additional work effort.
When pulling off the abrasive sheet protruding laterally beyond the grinding disk, grinding dust located in the grain can become detached and interfere with the treatment process as a whole, above all because the grinding dust is distributed in a larger region on the surface.
U.S. Pat. No. 5,394,654 discloses a method for removing a flaw of a treated surface, in which the flaw is recognized visually, i.e., by visual inspection, and manually marked. This marking is subsequently acquired by means of cameras as the foundation of a subsequent treatment. However, because of the exclusively visual recognition of the flaw, this method is not suitable for ensuring a uniform, reproducible work sequence.
DE 20 2013 101 858 U1 reflects prior art differing from the method of the type in question. It describes using a facility to grind the surface before surface finishing, for example, by painting. This literature does not give any indication of the treatment of a finish-painted surface, as the method of the type in question provides.
Furthermore, a grinding device is disclosed in U.S. Pat. No. 2,258,733 A, which has an abrasive belt as the abrasive sheet, wherein this grinding device is not suitable, however, for carrying out grinding work of the type in question.
Exemplary embodiments are directed to refining a method of the type in question in such a way that it can be carried out more cost-effectively.
By way of the invention, the grinding of the surface in the region of a flaw is automated, from which an entire array of advantages results over the method according to the prior art.
The duration of the post treatment is shortened, since the abrasive belt is exactly aligned for the optimum use in the connection region to the grinding disk. The exact guiding, which is typically not absolutely maintained during manual treatment, and which requires a longer treatment time to achieve the corresponding result, is now no longer to be taken into consideration with respect to the treatment duration, i.e., the treatment to achieve an optimum grinding result is now possible more reliably, reproducibly, and in a significantly shorter time.
A further advantage of the invention is the possibility of inclining the grinding disk, which has proven to be particularly effective. Both the number of the grinding points and also the grinding result are thus influenced with a reduction of the roughness depth.
Of course, substantial cost advantages result therefrom, which are noteworthy insofar as the treatment of the surface in the meaning of the invention is carried out on mass-produced products, i.e., in a quasi-uninterrupted work sequence.
According to a further concept of the invention, the abrasive belt is supplied from a dispenser to the grinding disk and fixed thereon. This fixation can be performed by a velour hook-and-loop connection, an adhesive bond, or a vacuum connection, wherein then the grinding disk, correspondingly modified with suction openings, is connected to a suction device.
To detach the connection, in particular the hook-and-loop connection and adhesive bond, an ejector is provided in the region of the grinding disk, after the use of which the abrasive belt is moved further by the corresponding distance up into a following unused region of the abrasive belt. The transportation of the abrasive belt preferably takes place cyclically, wherein, depending on the experiential value, the abrasive belt can be used in the unchanged position in relation to the grinding disk for multiple treatment passes.
Due to the cyclic advance of the abrasive belt in the active region of the grinding disk, as needed, a substantial shortening of the treatment time similarly results, in relation to the manual changing of the abrasive sheet.
With the use of a robot according to the invention, a further fitting time reduction results over the prior art due to dispensing with required distances for removing and changing the abrasive sheet.
According to a further aspect of the invention, the abrasive belt dispenser is a cassette having one unwinding shaft and one winding shaft. In this case, this cassette is a component of a grinding device having a robot arm and is to be completely replaced as needed, i.e., after consumption of the abrasive belt, and possibly to be re-equipped with abrasive belt.
Instead of the use of the cassette in the automatic grinding machine, the cassette can also be a component of a handheld grinding device. The grinding dust accumulating during the grinding can be separated in the cassette by way of a corresponding construction of the cassette.
Furthermore, in the grinding device according to the invention, the abrasive belt can partially be held tensioned in the cassette, for which a braking device can be provided in the cassette or directly adjacent outside, but which is functionally connected to the abrasive belt.
To tension the abrasive belt, pneumatically or hydraulically actuated cylinders can be provided, of which one presses the abrasive belt onto a deflection roller before the abrasive belt runs in toward the grinding disk and thus fixes it, and another cylinder engages on the abrasive belt on the outlet side, wherein this cylinder is operationally connected to a force sensor system, for example, a pressure sensor system.
The grinding movement of the surface, as is known from the prior art, is performed in the automatic grinding machine by a corresponding modification of the drive, wherein an orbital or vibrating movement is generated. In the case of rotating grinding, the cassette as a whole is also moved.
To be able to better treat more sensitive surfaces, the longitudinal edges of the abrasive belt are formed differently in the shape thereof, for example, linear, wavy, zigzag, or as a combination thereof.
The length of the used abrasive web is detectable by means of a sensor system. This can be ascertained in a computer-controlled manner via the initial length and the end of the abrasive belt.
Additionally, or alternatively, a sensor, for example, in the form of a laser, which detects a passage provided at the end of the abrasive web, is connected upstream from the grinding disk in the advancing direction of the abrasive belt, wherein this passage is placed in such a way that the abrasive belt length can be maximally utilized.
Problems have heretofore resulted when the abrasive belt, in particular in the case of one the carrier of which consists of paper, tears, which results in damage both on the surface to be ground and also on the grinding device itself.
To detect such a tear, according to a further concept of the invention, a corresponding sensor system is provided, which is preferably arranged before the grinding disk viewed in the passage direction of the abrasive belt. This sensor system is designed, for example, so that it comprises a movement sensor and a follower, which moves synchronously with the abrasive belt and is provided with markings, wherein this sensor system is associated with the non-driven output of the abrasive belt, preferably in the cassette.
In the event of a tear of the abrasive belt, the drawing off thereof by an unwinding shaft is interrupted, so that it is at a standstill, as is the follower, which is arranged in a twist-locked manner in relation to the unwinding shaft and which can be formed as a gear wheel, for example, wherein the teeth form the markings. A different configuration of the follower is also conceivable, if it comprises elements as markings permitting the movement of the follower or its standstill to be detected via the movement sensor.
The method according to the invention and an exemplary embodiment of a grinding device according to the invention will be described hereafter on the basis of the appended drawings.
In the figures:
A robot arm 2 supporting a grinding disk 3, which is moved accordingly by the sensor system to the flaw, is operationally connected to the sensor system.
In this case, the abrasive belt 5 is held on the grinding disk 3, which is movable in relation to the surface, for example, in an orbital, vibrating, or rotating manner, for grinding the flaw.
The abrasive belt 5 is held in a dispenser in the form of a cassette 4 and wound onto a roll 6 on an unwinding shaft 7 and is wound onto a winding shaft 8, preferably cyclically, in accordance with the grinding procedure.
The abrasive belt 5 is mounted on the grinding disk 3 in an integrally-joined or friction-locked manner, for example, by a detachable adhesive bond or by a hook-and-loop connection or suction connection. For the latter, a suction device (not shown) is provided, which is connected to the grinding disk 3.
The abrasive belt 5, which is recognizable as a portion in each of various embodiment variants in
To detach the abrasive belt 5 from the grinding disk 3, ejectors 9 are provided in the region of the grinding disk 3, in accordance with the illustrations in
In this case, ejectors 9 are provided on both sides of the grinding disk 3 in the example shown in
In
In
The winding shaft 8 is driven and draws the abrasive belt 5 off of the unwinding shaft 7, wherein the abrasive belt 5 is guided via a plurality of deflection rollers 13.
To be able to detect the end of the abrasive belt after completed usage, a laser source 14 is provided downstream of the unwinding shaft 7, which detects a passage (not shown) introduced at the end of the abrasive belt 5 during its production with the aid of a laser beam 15, so that the useful length of the abrasive belt 5 can be optimally utilized.
Since the cassette 4 is fixedly connected to the robot arm 2 in the exemplary embodiment, but the grinding disk 3, in contrast, is held using associated assemblies via a movable contact flange on the robot arm 2, the abrasive belt 5 has to be kept under constant tension in the region of the grinding disk 3.
Two tensioning elements are provided for this purpose in the example, specifically in the form of pneumatically or hydraulically actuated cylinders 11, 12, wherein one cylinder 11 presses the abrasive belt 5 against a deflection roller 13 before the entry of the abrasive belt 5 toward the grinding disk 3.
On the outlet side, i.e., downstream of the grinding disk 3, the abrasive belt 5 is tensioned by the cylinder 12, which engages on the abrasive belt 5 between two deflection rollers 13, via which the abrasive belt 5 is guided.
A sensor system is shown as a detail in
This sensor system consists of a movement sensor 16 and a follower 17 corresponding thereto, which is designed as a gear wheel and is held in a rotationally-fixed manner on the unwinding shaft 7, so that it executes a synchronous movement with the freely rotating unwinding shaft 7.
Since the unwinding shaft 7 is quasi-entrained with the abrasive belt upon actuation of the winding shaft 8, which is connected to a motor, the follower 17 is also pivoted accordingly. In the event of a tear of the abrasive belt 5, the unwinding shaft 7 stands still, as does the follower 17, which is detected by the movement sensor 16, so that the drive of the winding shaft 8 is interrupted.
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 2017 108 191.7 | Apr 2017 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/059660 | 4/16/2018 | WO | 00 |
