Device for sharpening and method for operating the device

Abstract

A device for sharpening edges of knives or other cutting tools with preferably a non-linear course has a mount for fixing the knife, at least one measuring device and at least one grinder. In a method of operating this device, 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.

Claims

1: A device for sharpening edges of knives or other cutting tools with preferably a non-linear course, wherein a mount for fixing the knife, at least one measuring device and at least one grinder is provided.

2: The device according to claim 1, wherein at least one drive for radial and/or transversal movement of the knife and/or the measuring device and/or the grinder is provided.

3: The device according to claim 1, wherein the drives are configured as servo-drives, pneumatic motors, hydraulic motors or the like.

4: The device according to claim 1, wherein a cam disc is provided for controlling the grinding process.

5: The device according to claim 4, wherein the cam disc is provided in virtual form.

6: The device according to claim 1, wherein a cleaning device is provided.

7: The device according to claim 6, wherein the cleaning device is configured for use of compressed air and/or cleaning liquid.

8: The device according to claim 1, wherein a presser device is provided for the grinder.

9: The device according to claim 1, wherein a control device is provided.

10: The device according to claim 1, wherein the measuring device is configured as an optical scanning device, particularly according to the principle of a light section.

11: The device according to claim 1, wherein a cover and/or a protective housing for the measuring device is or are provided.

12: A method of operating the device according to claim 1, wherein 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.

13: The method according to claim 12, wherein determination of the course of the edge is carried out by a measuring device, wherein in that case an optical measuring device which operates in particular according to the principle of a light section can be used.

14: The method according to claim 12, wherein 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.

15: The method according to claim 12, wherein the measuring device undertakes the measurements at discrete predetermined points.

16: The method according to claim 12, wherein the measuring device determines the edge angle, the edge chamfer length, the edge flank angle and/or the edge chamfer length.

17: The method according to claim 12, wherein the wear state of the knife relative to the predetermined edge course is measured by the measuring device.

18: The method according to claim 12, wherein the knife is measured again after the grinding process and a target/actual value comparison is performed.

19: The method according to claim 12, wherein 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.

20: The method according to claim 12, wherein the control uses mechanisms of fuzzy logic and/or artificial intelligence and thus optimises optimizes the sharpening process.

21: The method according to claim 12, wherein 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 i-t the protective housing again afterwards can be provided for that purpose.

22: The method according to claim 12, wherein the knife is freed of grinding residues by a cleaning device after the grinding process, wherein a compressed air nozzle and/or a washing device with cleaning liquid can be provided for that purpose.

23: The method according to claim 12, wherein the knife is cleaned by one or more brushes after the grinding process, wherein the brushes can be fixed and/or driven.

24: The method according to claim 23, wherein the brushes can be equipped with plastics material bristles and/or textile bristles.

25: The method according to claim 12, wherein the method is used for sharpening sickle knives.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] 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.

[0060] In the drawings,

[0061] FIG. 1 shows a spiral or sickle knife,

[0062] FIG. 2 shows a detail view of a section through the edge of such a knife, and

[0063] FIG. 3 shows a schematic view of a device for sharpening and measuring such a knife.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] The resharpening process of a sickle knife 1 is described, by way of example, by the following steps: [0070] 1. Determining all data relevant to the resharpening process by measuring and storing over the entire edge course a degree of wear v, an edge angle a, an edge chamfer length s, an edge flank angle b and an edge flank length fin dependence on angular position g of the sickle knife 1. The measuring should preferably be carried out with a resolution in the region of 1 ?m. [0071] 2. Calculation of the necessary grinding parameters in dependence on the measurement results. The edge surface is to be ground, depending on, for example, the knife position at the angle g with the highest degree v of wear, to such an extent that the edge course corresponds with an exact offset of the original edge course R=f(g)?k, wherein k corresponds with the calculated offset value. Moreover, the target rotational speed of the grinding disc 7 as a function of the angular setting g of the sickle knife 1 can be calculated by way of the circumferential speed of the knife and the respective degree v of wear. [0072] 3. After calculation of the grinding process of the edge surface this is executed over the entire edge course by means of the grinding disc 7 controlled in rotational speed. In that regard the calculated rotational speed of the grinder motor 8 is electronically regulated. The axially acting pressing force F of the grinding disc 7 against the sickle knife 1 is, in a presser unit 9, either mechanically (pneumatically, gravimetrically or by spring-loading) kept constant or precisely regulated by means of electromagnetism during the grinding process. [0073] 4. A check is carried out by means of a fresh measuring cycle as to whether the calculated grinding process has led to the desired result or whether a fresh grinding process is needed. In the case of differences of the grinding result from the target values a correction of the calculation procedure is useful. Adaptation of the calculation process is preferably carried out with inclusion of methods of artificial intelligence. [0074] 5. The edge flank surface is also to be reground, since with increasing regrinding of the edge surface the edge chamfer length s is larger. The measurement values of the edge chamfer length s and the edge flank length f, the edge angle a and the edge flank angle b are used for calculation of this grinding process. [0075] 6. A concluding check of the grinding results by means of fresh measurement serves to release the knife for reuse.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.