Method for sharpening a knife

Abstract

In a method for sharpening a knife, dimensions of the knife are measured using a scanner. A desired shape is then determined by knife-edge shapes which are obtainable by removing material being determined as straight lines or curves. A machining quality is then determined and, of the possible knife-edge shapes, the one is selected which corresponds to the machining quality before, in order to achieve the desired shape, the knife is ground until the desired shape is reached.

Description

[0001] Method for sharpening a knife

[0002]

[0001] The invention relates to a method for sharpening a knife in which the dimensions of the knife are measured using a scanner.

[0003]

[0002] US Patent 2024 / 0293913 describes a method for determining the sharpness of a robotic lawnmower blade. The exact values ​​of the blade are determined, and it is checked whether the blade still meets the requirements.

[0004]

[0003] Starting from this, the invention is based on the objective of optimizing the process of sharpening a knife as much as possible.

[0005]

[0004] This problem is solved by a method having the features of claim 1. Advantageous further developments are the subject of the dependent claims.

[0006]

[0005] The invention is based on the finding that the grinding process can be largely automated if the analysis of the knife shape is combined with the control of the grinding machine.

[0007]

[0006] By initially measuring the dimensions of the knife with a scanner, it is possible to determine what type of knife it is. This makes it easy to determine where and how the knife needs to be sharpened. Furthermore, the analysis of the knife's shape, and in particular its cutting edge, reveals whether there are straight lines or serrations in the edge. It also shows how the angles of surfaces are formed and whether and where the cutting edge is sharp or less sharp.

[0008]

[0007] Blades used for mowing a lawn include reel mowers with a spirally curved cutting edge, robotic lawnmowers with rectangular blade plates with a cutting edge on one side of the plate, and rotary mowers with cutting edges arranged only on one side or symmetrically around a center. The invention relates in particular to blades of such rotary mowers in which cutting edges are provided on the blade at a radial distance from the center, which must be sharpened after intensive use.

[0009]

[0008] The analysis of the shape can lead to the conclusion, even before the grinding process, that the knife should no longer be ground due to excessively deep chips in the cutting edge, a crack in the knife, or a twisting of the knife.

[0010]

[0009] If such defects are detected in the first step, the process is terminated before the knife is sharpened. Either the scan of the knife shows that sharpening is no longer worthwhile, or it shows that there is a high risk of the knife breaking during further use.

[0011]

[0010] If, in the first step, the dimensions of the knife are measured, it is therefore advantageous if not only the dimensions of the cutting edge but also the dimensions of the entire knife and of cracks, chips, etc. are determined and measured.

[0012]

[0011] As a next step, a target knife shape is determined by identifying cutting edge shapes achievable through material removal, either as straight lines or curves, particularly without inflection points. Grinding a knife results in material removal, and depending on the grinding machine, only a certain amount of material removal can be achieved. Naturally, it would be advantageous if material could also be added, but grinding only allows for material removal, which means that, for example, when creating notches, a large amount of material often has to be removed, and in particular, more than is necessary for grinding the adjacent areas.

[0013]

[0012] The determination of the target shape therefore depends on the expected quality of the cutting edge. Generally, an optimum is not set as the target shape, but rather the target shape is determined based on a trade-off between machining time, material removal, and cutting edge shape. Here, the machining time generally correlates with the material removal.

[0013] The cutting edge shapes achievable through material removal should have virtually no notches and should follow a straight line or a simple curve as closely as possible. The cutting edges of knives are generally straight or curved, but without waves and, in particular, without a turning point in the shape of the sheath line.

[0014]

[0014] As a next step, to determine the machining quality, the material removal and / or the machining time to achieve a cutting edge shape and / or the remaining deviation from the target knife shape are determined.

[0015]

[0015] The machining quality must be determined individually, otherwise the machining time will become too long and the material removal may be too great. The machining quality may be limited by the available machining time. It may also be limited by a maximum material removal rate.

[0016]

[0016] Depending on the machining quality, only a certain target shape is possible. Therefore, in a next step, it is determined which cutting edge shape corresponds to the machining quality and this cutting edge shape is selected for machining.

[0017]

[0017] The knife can then be ground to achieve the desired shape until the desired shape is reached.

[0018]

[0018] The method according to the invention has the advantage that, with a predetermined processing quality that is selected beforehand, a knife can be ground fully automatically without the need for manual intervention.

[0019]

[0019] Increasingly better machining qualities can also be entered successively. Grinding is only performed up to the specified machining quality, and then it is determined whether further grinding should be carried out to achieve an even better machining quality. For this, a higher machining quality is then entered.

[0020] It is advantageous if the machining quality is defined as a ratio between the necessary material removal and / or the necessary machining time to achieve a cutting edge shape and the remaining deviation from the cutting edge shape.

[0020]

[0021] Any scanner capable of determining the shape of a cutting edge can be used. Using a 3D laser scanner is advantageous.

[0021]

[0022] For common blades, especially those used for sickle mowers, the dimensions of the original blade before use, and particularly before resharpening, are known. If the type of blade is known, then its original shape is also known. These dimensions of various blades can be entered into a database as the primary blade shape. This makes it possible to determine the corresponding blade shape based on the scanned dimensions of any blade by comparing the measured dimensions with those of blades in the database. This comparison also allows values ​​to be added or corrected. It is understood that a blade cannot be restored to its original shape by sharpening.However, based on the original shape, forms for sharpened knives can be defined that are easily achieved by grinding the knife and result in a sharp edge. These are shapes that, over a certain area, result in a uniform deviation from the original shape in order to form an edge that is either parallel or offset from the original shape.

[0022]

[0023] It is advantageous to measure the knife's dimensions again with a 3D laser scanner after achieving the target shape. This serves as a check, and the data can be saved as secondary master data and used when the knife needs resharpening after reuse. The secondary and / or primary master data can then be used to determine a suitable target shape.

[0024] In order to check the process and, if necessary, interrupt or correct it, it is advantageous if the dimensions of the knife and the target shape are displayed, preferably continuously, during the grinding of the knife.

[0023]

[0025] Accordingly, it can also be advantageous to display the remaining material removal and / or processing time required to achieve the desired shape during the sharpening of the knife.

[0024]

[0026] Finally, the remaining deviation from the cutting edge shape can also be displayed during the sharpening of the knife.

[0025]

[0027] A method for sharpening a sickle knife is described in more detail below.

[0026]

[0028] In a preferred embodiment of the method, the dimensions of a knife are measured using a scanner. Artificial intelligence is then used to determine a target knife shape based on similar knife shapes or a targeted modification of the scanned knife shape. It is advantageous if the target knife shape is determined as a straight line or curve, achievable by material removal. This is typically a straight line, but the line can also be curved or arc-shaped. Generally, such target knife shapes do not have an inflection point along the cutting edge.

[0027]

[0029] To determine a realistic machining quality, the material removal and / or machining time required to achieve a cutting edge shape, and / or the remaining deviation from the target blade shape, are defined. The cutting edge shape that most closely matches the machining quality is then selected. The blade is then ground to achieve the target shape until it is reached.

[0028]

[0030] To determine machining quality, a ratio can be established between the necessary material removal and / or machining time required to achieve a cutting edge shape and the remaining deviation from that shape. This ratio then corresponds to the machining quality, which can be increased as desired but should have a realistic value that is meaningful in practice.

[0029]

[0031] A 3D laser scanner is used as the scanner, and to determine the target knife shape, a prototype knife shape is first created by comparing the measured dimensions with the dimensions of knives in a database and supplementing or correcting them. The prototype knife shape should correspond to the shape of the knife before its use.

[0030]

[0032] After achieving the target shape, the dimensions of the knife are measured again with a 3D laser scanner, and during the grinding of the knife, the dimensions of the knife and the target shape are continuously displayed on a screen.

[0031]

[0033] To enable the operator to monitor and, if necessary, stop the grinding process, the remaining material removal and / or processing time required to achieve the target shape are displayed on the screen during the grinding process. This display can also show the remaining deviation from the cutting edge shape, either as a percentage or in absolute terms, to indicate the remaining processing time and allow the operator to stop the grinding process if a certain level of quality is reached.

Claims

Patent claims:

1. Method for sharpening a knife in which the dimensions of the knife are measured using a scanner, A target knife shape is determined by identifying cutting edge shapes achievable through material removal, as straight lines or curves, particularly without an inflection point. The material removal rate and / or the processing time required to achieve a cutting edge shape and / or the remaining deviation from the target blade shape are determined to define the processing quality. The cutting edge shape that corresponds to the processing quality is selected and The knife is sharpened to achieve the desired shape until the desired shape is reached.

2. Method according to claim 1, characterized in that the machining quality is defined as a ratio of the necessary material removal and / or the necessary machining time to achieve a cutting edge shape and the remaining deviation from the cutting edge shape.

3. Method according to claim 1 or 2, characterized in that a 3D laser scanner is used as the scanner.

4. A method according to any of the preceding claims, characterized in that a knife prototype is determined by comparing the measured dimensions with the dimensions of knives in a database and adding or correcting values.

5. A method according to any of the preceding claims, characterized in that, after the target shape has been achieved, the dimensions of the knife are measured again using a 3D laser scanner.

6. Method according to one of the preceding claims, characterized in that the dimensions of the knife and the target shape are displayed, preferably continuously, during the grinding of the knife.

7. Method according to one of the preceding claims, characterized in that during the grinding of the knife, the remaining material removal and / or the remaining processing time required to achieve the desired shape are displayed.

8. Method according to one of the preceding claims, characterized in that the remaining deviation from the cutting edge shape is displayed during the grinding of the knife.