Patent Application
20240157514
Applicant claims priority under 35 U.S.C. § 119 of German Application No. 10 2022 112 000.7 filed May 12, 2022, the disclosure of which is incorporated by reference.
The invention relates to a device for sharpening edges of knives or other cutting tools with preferably a non-linear course and to a method of operating the device.
Wear occurs at the edges of knives, particularly sickle knives, through use thereof in high-performance cutting-up cutters, so-called slicers. Even with the hardest of knife materials this wear is considerable, since slicers are operated at high cutting speeds of up to 2,000 cuts per minute. With increasing wear the knives no longer provide smooth clean cuts and also the delivery position and delivery shape of the separated slices uncontrollably change.
Since knives are very costly the service life thereof has to be as long as possible. For this reason knives after becoming blunt have to be resharpened so that the full extent of the original cutting characteristics is achieved again.
In many applications this resharpening process is already necessary after each work shift, since not only cut quality, but also delivery quality of the separated slices have to be maintained.
Due to geometric relationships knives can be reground only as far as a specific wear limit, which currently is between 5 to 10 millimeters decrease in outer knife radius.
In that case it is necessary to design a sharpening process so as to ensure exactly the same edge geometry over the course of the edge as in the new state of the knife.
The reduction of material during the sharpening process shall then be as small as possible.
The object of the invention is therefore to propose a device and a method which combine these two aspects.
According to the invention this object is fulfilled in that a mount for fixing the knife, at least one measuring device and at least one grinder is provided.
It is thereby made possible on the one hand to determine the contour and thus the wear of the knife and to resharpen the knife by means of the grinder.
In that case according to the invention it has proved very advantageous if at least one drive for radial and/or transversal movement of the knife and/or the measuring device and/or the grinder is provided.
The device is thus very satisfactorily controllable.
A further very advantageous embodiment in accordance with the invention is present if the drives are configured as servo-drives, pneumatic motors, hydraulic motors or the like.
These drives have proved particularly suitable due to their respective characteristics.
An embodiment which is extremely advantageous in accordance with the invention is present if a cam disc is provided for controlling the grinding process.
The course of the edge of the knife is defined by means of the cam disc.
In that case it has also proved very advantageous if the cam disc is provided in virtual form.
Through a virtual predetermined cam disc this can be very easily exchanged depending on the knife to be processed.
A further very advantageous embodiment of the invention is present if a cleaning device is provided.
The knife can be cleaned before and/or after the grinding process by this cleaning device. Undesired particles are removed.
In that case it has proved particularly advantageous if the cleaning device is configured for use of compressed air and/or cleaning liquid.
Depending on the grinding materials used, cleaning is better suited by means of compressed air or by means of cleaning liquid.
According to the invention it has also proved very advantageous if a presser device is provided for the grinding device.
The presser device ensures a uniform grinding process.
Moreover, it has proved very advantageous if a control device is provided.
The data determined by the measuring device can be converted by means of the control device in such a way that the grinder can be controlled so that a smallest possible removal of material achieves reinstatement of the edge.
According to a further embodiment of the invention it is very advantageous if the measuring device is configured as an optical scanning device, particularly according to the principle of a light section.
As a result, very precise measurement data of the edge course can be determined contactlessly. The edge can in that case be measured at predetermined points.
A further very advantageous embodiment of the invention is present if a cover and/or a protective housing for the measuring device is or are provided.
Undesired contamination of the measuring device is thereby prevented above all during the grinding process.
An extremely advantageous method of operating a device according to the invention is present if a knife is clamped in a mount and initially the course of the edge by comparison with a predetermined cam disc is determined and then a difference from the predetermined cam disc profile is calculated on that basis and the sharpening process correspondingly regulated.
Through determination of the actual edge course the difference thereof from the target course can be ascertained, whereby the degree of wear is also known. An optimal grinding process for sharpening the edge is determined on that basis.
In that case it has proved very advantageous if determination of the course of the edge is carried out by a measuring device, wherein in that regard an optical measuring device operating according to, in particular, the principle of a light section can be used.
The use of a measuring device of that kind enables contactless determination of very precise measurement data.
Furthermore, it has proved very advantageous if the difference from the predetermined guide disc is determined by computer and these comparison values form the basis for control of the sharpening process by grinding.
An optimal sharpening process with little material removal can thus be carried out.
An equally very advantageous embodiment of the invention is present if the measuring device undertakes the measurements at discrete predetermined points.
Measurement data from discrete points usually suffices to determine the state of the edge.
According to a further realization of the invention it is also extremely advantageous if the measuring device determines the edge angle, the edge chamfer length, the edge flank angle and/or the edge chamfer length.
All these are indicators for the state of the edge. These must all be brought back to target dimension in order to guarantee optimal functioning of the knife.
It has also proved very advantageous if the wear state of the knife relative to the predetermined edge course is measured by the measuring device.
The degree of wear can thus be established and a decision made as to whether the knife can be sharpened again.
According to the invention it is also extremely advantageous if the knife is measured again after the grinding process and a target/actual value comparison is performed.
Quality control is thereby carried out. It is checked whether the desired effect was achieved by the grinding process. In a given case reprocessing can be undertaken.
Moreover, it is extremely advantageous if the control controls and monitors the relevant parameters of the grinding process primarily with respect to pressing force, grind angle, grinding disc rotational speed and speed of movement of the knife.
A very accurate and careful sharpening process is thus ensured.
According to a development of the invention it is also very advantageous if the control uses mechanisms of fuzzy logic and/or artificial intelligence and thus optimizes the sharpening process.
Adaptation of the sharpening process to different circumstances can thereby be ensured.
Further, it has proved very advantageous if the measuring device is covered by a protective housing during the grinding process and an actuator which places the protective housing on the measuring device before the start of the grinding process and removes it again afterwards can be provided for that purpose.
Undesired contamination, which interferes with the measuring process, of the measuring device by the grinding process is thus prevented.
Moreover, it has proved particularly advantageous if the knife is freed of grinding residues by a cleaning device after the grinding process, in which case a compressed air nozzle and/or a washing device with cleaning liquid can be provided for that purpose.
Through cleaning of the knife by means of compressed air and/or cleaning liquid, grinding particles—whether abraded material from the grinding device or even abraded material from the knife—are prevented from adhering to the knife and from falsifying the measurement results in a concluding measuring process. In addition, when the finally sharpened knife is removed, continued adhesion of these particles thereto is prevented.
A further very advantageous embodiment of the invention is present if the knife is cleaned by one or more brushes after the grinding process, wherein the brushes can be fixed and/or driven.
Adhering particles can also be removed very satisfactorily by means of brushes. Combination with a washing device is conceivable.
In that case it has proved very advantageous if the brushes can be equipped with plastics material bristles and/or textile bristles.
These bristles have proved particularly suitable.
According to the invention it is also very advantageous if the method is used for sharpening sickle knives.
Sickle knives in particular, which are used especially in high-performance cutting-up cutters, are subject to a large amount of wear and need careful handling during resharpening so as to guarantee a greatest possible service life and above all a uniform cut and uniform delivery of cut slices.
Other objects and features of the invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention.
In the drawings,
A device for sharpening a sickle knife 1 is equipped with a cam disc 2 and a hub 3 for mounting the sickle knife 1. The sickle knife 1 is fixedly connected with the hub 3 and cam disc 2 by means of, for example, screws 4. The hub 3 is rotationally moved by way of a drive, wherein the angular position of the sickle knife 1 is predetermined by the control or reported back to that.
The rotary drive of the cam disc 2, hub 3 and sickle knife 1 is placed on a linear guide so that the sickle knife 1 can be moved perpendicularly to its axis of rotation. This movement is so guided by rolling of the cam disc 2 on a stationary roller 5 or runner that the geometry of the cutting wedge of the knife edge can be detected by a stationary measuring device 6.
Resharpening of the sickle knife 1 also takes place by way of the cam disc 2 guided from a fixedly set position of a grinding disc 7.
The measuring device 6 and the grinder, consisting of grinding disc 7, presser unit 9 and grinder motor 8, are to be placed on respectively opposite sides of the linear guide so that by means of a pneumatic linear drive the cam disc 2 either runs along a roller 5 in the vicinity of the grinding disc 7 or is guided at a second roller 5 in the vicinity of the measuring device 6.
Through use of two servo-drives for the rotational movement and also the linear movement of the sickle knife 1 the cam disc 2 can be moved, electronically controlled by a virtual cam disc with the function R=f(g), into the settings for measuring or grinding.
The resharpening process of a sickle knife 1 is described, by way of example, by the following steps:
As illustrated, the sharpening process consists of a sequence of highly accurate measurements and grinding processes. During the grinding process not only cooling liquid, but also removed particles spray around in the sharpening device and can contaminate not only the sickle knife 1, but also all fixtures present in the surroundings. A precondition for precise measurement is cleaning of the sickle knife 1 as well as keeping the measuring device 6 clean. A very sensitive optical system is employed particularly if the light section method is used.
Cleaning of the sickle knife 1 of adhering grinding particles takes place in this embodiment by means of a water jet from a water nozzle 10 and a downstream air nozzle 11, which produces cleaning and drying of the region, which is to be measured, of the sickle knife 1. In a preferred variant the use of textile brushes is conceivable as an addition to or a substitute for the air nozzle.
The measuring device 6 has to be protected from contamination during the grinding process. This can take place on the one hand by removal of the measuring device 6 before each grinding process and reinstatement, after the end of the grinding process, for performance of the measurement.
However, the present invention substantially simplifies this procedure. The measuring device 6 can remain at a fixed position and is protected from any foreign particles by a protective hood 12 during the grinding process. The protective hood can be inverted, from a parked position during the measuring process, by an actuator over the measuring device 6 for protection thereof. Here the use of pneumatic stroke pivot units as actuator 13 has proved particularly worthwhile.
The protective mechanism can be automated by special control software in such a way that starting of the grinding process without protection of the measuring device 6 is excluded.
The present invention makes it possible for the entire sharpening process of the sickle knife 1 to be automated, in that setting variables such as, for example, the angle of incidence of the grinding disc 7 or the pressing force of the grinding disc 7 against the sickle knife 1 are controlled by setting motors 14 and actuators from a computer controller.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 112 000.7 | May 2022 | DE | national |
