Messrad

Abstract

Measuring wheel (10, 24, 30, 36, 38, 39, 40) for length and / or speed measurements, with a cylindrical wheel body (12) having a lateral surface (14) with a running surface (18), wherein the running surface (18) is at least partially formed by a wear layer (20), characterized in that a thickness (D) of the wear layer (20) corresponds to a maximum tolerable abrasion of the running surface (18), and that the measuring wheel (10, 24, 30, 36, 38, 40, 52) has at least one wear indicator by which reaching the maximum tolerable abrasion of the running surface (18) can be visually detected.

Description

[0001] The present invention relates to a measuring wheel for length and / or speed measurements according to the preamble of claim 1 or a measuring device according to the preamble of claim 11.

[0002] A measuring wheel converts linear motion into rotational motion, which can be detected by a rotary encoder or a rotary sensor. This allows the speed and length of a moving object in contact with the measuring wheel to be measured.

[0003] Such measuring wheels can be used in measuring devices in the automation industry, with which, for example, - the speed of a transport or conveyor belt is determined - the speed and / or length of rail freight, i.e., virtually endless goods made of a wide variety of materials, is measured - goods moving on a conveyor belt are measured - the speed of storage shuttles that move back and forth in a guided storage aisle is determined

[0004] Such measuring devices are known, for example, from EP 3 091 331 B1 or DE 10 2022 108 742 B4 of the applicant.

[0005] For a linear motion to be accurately measured by a measuring wheel, its actual circumference must be known as precisely as possible. Any deviation of the actual circumference from a nominal circumference used as the basis for length and / or speed calculations leads to a measurement error. Direct contact between the measuring wheel and the surface being measured can cause abrasion on the wheel's running surface, which reduces the wheel's circumference and consequently alters the measured lengths or speeds. This abrasion typically occurs gradually, resulting in a gradual change in the measurement.

[0006] The wear on the running surface or the wear on the measuring wheel is barely or not at all detectable visually. This means the user receives no feedback about a potential measurement error or a distorted measurement result. A reliable determination of the wear is generally only possible through a mechanical measurement of the measuring wheel, which usually requires disassembly of the measuring device, or at least an interruption of its operation.

[0007] It is therefore an object of the invention to improve a measuring wheel or a measuring device for measuring a distance and / or a speed of an object moving relative to the measuring device in such a way that the aforementioned disadvantages can be avoided.

[0008] The problem is solved according to the invention by a measuring wheel with the features of claim 1 or by a measuring device with the features of claim 11.

[0009] A measuring wheel according to the invention for length and / or speed measurements comprises a cylindrical wheel body, which can be attached, for example, to a shaft of a rotary encoder. The cylindrical surface of the wheel body has a running surface that can be placed on an object. The running surface is at least partially formed by a wear layer whose thickness corresponds to the maximum tolerable wear of the running surface. Maximum tolerable means that a measurement error resulting from the wear of the running surface and the associated reduction in the circumference of the measuring wheel does not exceed a predetermined value.

[0010] "At least partially" means that the tread does not have to be entirely formed by the wear layer, but can also consist of other materials. The wear layer can preferably be part of the wheel body itself, i.e., made of the same material as the wheel body. Particularly preferably, the wear layer can be applied to the outer surface of the wheel body, and can be made of the same material as the wheel body or, more specifically, of a different material. For example, the wheel body can be made of plastic or metal (e.g., stainless steel or aluminum), and the wear layer can consist of a plastic or rubber layer applied to the outer surface of the wheel body.

[0011] The measuring wheel also features at least one wear indicator, allowing visual detection of when the maximum tolerable wear of the running surface has been reached. This enables wear of the measuring wheel to be determined without disassembly, particularly during use, thereby improving the operational process of the machine on which the measuring wheel is used.

[0012] The thickness of the wear layer can be less than 0.8 per mille, preferably less than 0.4 per mille, and particularly preferably less than 0.2 per mille of the nominal circumference of the measuring wheel. This allows for the detection of deviations in the circumference of the measuring wheel, and thus errors in speed or length measurements, of less than 0.5%, 0.25%, and 0.18%, respectively. Furthermore, with known wear, a measurement correction can be applied, enabling a measuring wheel that is at least partially worn to remain in use for a longer period.

[0013] In one embodiment of the measuring wheel, the wear indicator can preferably be formed by an indicator layer arranged between the outer surface and the wear layer, wherein the color of the indicator layer differs from the color of the wear layer. This makes it particularly easy to detect whether there is complete wear of the wear layer at any point on the running surface.

[0014] In a further embodiment of the measuring wheel, the wear indicator can preferably be formed by at least one first groove with a first depth in the wear layer, wherein the first depth of the first groove corresponds to the thickness of the wear layer. At least partial disappearance of the groove thus indicates that the maximum tolerable wear of the running surface has been reached. A wear indicator in the form of an indicator layer between the outer surface and the wear layer is not necessary in this case. However, in a further embodiment of this design, an indicator layer can be provided between the outer surface and the wear layer analogous to the previous embodiment, thereby further simplifying wear detection.

[0015] In one embodiment of the measuring wheel, the groove preferably runs perpendicular to an axis of rotation of the measuring wheel. This allows abrasion to be detected along the circumference of the running surface. The groove can run continuously around the entire circumference of the running surface or in sections. A continuous groove has the advantage that abrasion can be detected across the entire circumference of the running surface. A sectioned groove results in a flatter running surface. Preferably, several parallel grooves can be provided. This allows even one-sided abrasion of the wear layer to be detected.

[0016] In another embodiment of the measuring wheel, the groove can preferably run parallel to the axis of rotation of the measuring wheel. Particularly preferably, the groove can extend from one side face of the measuring wheel towards an opposite side face. This allows the wear of the wear layer on one side face of the measuring wheel to be detected.

[0017] In another embodiment of the measuring wheel, the groove can preferably run diagonally to the axis of rotation of the measuring wheel. Particularly preferably, the groove can extend from one side face of the measuring wheel towards an opposite side face. This allows the wear of the wear layer on one side face of the measuring wheel to be detected.

[0018] The wear layer preferably has at least one second groove with a second depth, wherein the second depth is less than the thickness of the wear layer. This allows the wear rate of the wear layer to be determined. For example, if the depth of the second groove is half the thickness of the groove layer, the disappearance of the second groove can indicate that the thickness of the wear layer has decreased by half. In a further embodiment of this design, the wear layer preferably has at least one third groove with a third depth, wherein the third depth is less than the second depth of the second groove. This allows the wear rate of the groove layer to be determined even more precisely.In this embodiment, for example, the disappearance of the third groove can indicate that the thickness of the wear layer has decreased by half, the disappearance of the second groove can indicate that the wear layer is almost completely worn and a replacement of the measuring wheel is imminent, and the disappearance of the first groove can indicate that the wear layer is completely worn and the measuring wheel must be replaced.

[0019] At least one inner surface of one or more of the grooves in the wear layer may preferably have a color that differs from the color of the wear layer, which makes it easier to detect the disappearance of the groove due to abrasion of the wear layer.

[0020] One or more of the grooves in the wear layer can preferably be filled with a material. In this case, the material forms part of the running surface. The color of the material preferably differs from the color of the wear layer, which makes it easier to detect if the groove disappears due to abrasion of the wear layer. Filling the groove with a material has the further advantage of creating a flat running surface.

[0021] A further aspect of the invention is a measuring device for measuring the displacement and / or velocity of an object moving relative to the measuring device. The measuring device comprises a rotary encoder and a measuring wheel, as described in one of the embodiments above, which is attached to a shaft of the rotary encoder. The measuring device includes a holding device configured to hold the rotary encoder and connect it to a stationary component of a machine. The holding device is further configured to press the measuring wheel against a surface, for example, of a conveyor belt or of the item to be measured, via the rotary encoder.The movement of the conveyor belt or the item to be measured causes the measuring wheel of the measuring device to move along with it, so that the rotation of the measuring wheel is transmitted via the shaft to the rotary encoder with precise angle of rotation, which can determine the distance and / or speed of the measuring wheel and thus of the conveyor belt or the item to be measured.

[0022] The measuring device preferably includes at least one sensor for optically acquiring and generating image data of the measuring wheel, in particular the running surface and / or the thickness of the wear layer of the measuring wheel. A display device, for example a monitor, can be configured to receive and output the image data of the measuring wheel from the sensor. This facilitates the operator's ability to recognize the condition of the running surface or the wear layer. Direct visual inspection of the measuring wheel by the operator is then unnecessary, which can be particularly advantageous when the measuring device is located in hard-to-reach positions on a machine.

[0023] Alternatively or additionally, the measuring device can include an evaluation unit configured to receive and evaluate the image data of the measuring wheel from the sensor. The evaluation unit can, for example, be configured to compare the received image data with predefined image data. Predefined image data can, for example, include images of the measuring wheel's running surface that are representative of different wear levels of the wear layer. The evaluation unit can further be configured to determine the wear level of the measuring wheel from the image data and transmit information about the wear level to a higher-level control system. Based on the wear level information, the higher-level control system can, for example, correct measured values ​​generated by the rotary encoder.

[0024] The invention is further explained below with regard to its advantages and features, with reference to the accompanying drawing and by means of exemplary embodiments. The figures in the drawing show: Fig. 1 to Fig. 7 schematic representations of exemplary embodiments of measuring wheels according to the invention; Fig. 8 a schematic representation of an embodiment of a measuring device with a measuring wheel according to the invention;

[0025] Fig. Figure 1 shows an embodiment of a measuring wheel 10 according to the invention from various perspectives. The measuring wheel 10 comprises a cylindrical wheel body 12 with a cylindrical surface 14 and a bore 16, which can serve to receive a shaft of a rotary encoder. The cylindrical surface 14 of the wheel body 12 has a running surface 18, which can be placed on an object. The running surface 18 is formed by a wear layer 20 with a thickness D. The thickness D of the wear layer 20 corresponds to a maximum tolerable abrasion of the running surface 18. A wear indicator formed by an indicator layer 22 is arranged between the cylindrical surface 14 and the wear layer 20. The color of the indicator layer 22 differs from the color of the wear layer 20. This makes it easy to visually detect when the running surface 18 is completely worn down at least in one area.

[0026] Fig. Figure 2 shows a further embodiment of a measuring wheel 24 according to the invention, in which the wear indicator is formed by at least one first groove 26 with a first depth T1 in the wear layer 20, wherein the first depth T1 of the first groove 26 corresponds to the thickness D of the wear layer 20. The disappearance of the groove 26 thus indicates that the maximum tolerable abrasion of the running surface 18 has been reached. The groove 26 runs perpendicular to the axis of rotation 28 of the measuring wheel 24. This allows abrasion to be detected along the entire circumference of the measuring wheel 24.

[0027] Fig. 3 shows an exemplary further training of the in Fig. 2 of the measuring wheel shown 24.

[0028] The measuring wheel 30 according to the invention has a second groove 32 and a third groove 34 with a first depth T1, which corresponds to the thickness D of the wear layer 20. The second groove 32 and the third groove 34 run parallel to each other and parallel to the first groove 26, whereby one-sided abrasion of the running surface 18 can be detected.

[0029] In Fig. 4 is a further embodiment of a measuring wheel 36 according to the invention as a further development of the one described in Fig. The measuring wheel 30 described in Figure 3 is shown. The second groove 32 has a second depth T2, which is less than the first depth T1 of the first groove 26. The third groove 34 has a third depth T3, which is less than the first depth T1 of the first groove 26 and less than the second depth T2 of the second groove 32, thus allowing a gradual wear of the running surface 18 to be determined.

[0030] Fig. Figure 5 shows a further embodiment of a measuring wheel 38 according to the invention, in which the wear indicator is formed by at least one first groove 26 with a first depth T1 in the wear layer 20, which runs parallel to the axis of rotation 28 of the measuring wheel 38, starting from a side surface of the measuring wheel 38 in the direction of an opposite side surface of the measuring wheel 28. This allows the abrasion of the wear layer 20 on a side surface of the measuring wheel 38 to be detected.

[0031] Fig. Figure 6 shows a further embodiment of a measuring wheel 39 according to the invention, in which the wear indicator is formed by at least one first groove 26 with a first depth T1 in the working layer 20, which runs diagonally to the axis of rotation 28 of the measuring wheel 39, starting from a side surface of the measuring wheel 39 in the direction of an opposite side surface of the measuring wheel 28.

[0032] In further, not shown, variations of the in the Fig. In embodiments 2 to 6 shown, an indicator layer can be placed between the outer surface 14 and the functional layer 20 analogously to the one shown in Fig. 1. This is provided for in the embodiment shown.

[0033] In Fig. Figure 7 shows an embodiment of a measuring wheel 40 according to the invention, in which a groove is filled with a material 42 whose color differs from the color of the wear layer 20. This allows for better detection of the groove's disappearance, and thus the material 42's loss, due to abrasion of the wear layer 20. Filling the groove with the material has the further advantage of creating a flat running surface.

[0034] Fig.Figure 8 shows an exemplary measuring device 44 for measuring the displacement and / or velocity of an object moving relative to the measuring device 44, in this embodiment a conveyor belt 46. The measuring device 44 comprises a rotary encoder 48 with a shaft 50 to which a measuring wheel 52, designed according to one of the embodiments described above, is attached. A holding device 54 holds the rotary encoder 48 and connects it to a stationary component 56 of a machine (not shown). The holding device 54 is further configured to press the measuring wheel 52 against a surface of the conveyor belt 46 via the rotary encoder 48. The movement of the conveyor belt 46 causes the measuring wheel 52 of the measuring device 44 to move along with it, so that the rotation of the measuring wheel 52 is transmitted via the shaft 50 to the rotary encoder 48 with precise angular accuracy, which can determine the displacement and / or velocity of the measuring wheel 52 and thus of the conveyor belt 46.The exemplary measuring device 44 includes an (optional) sensor 58 for optically acquiring and generating image data of the running surface 18 of the measuring wheel 52. A monitor 60 is designed to receive and output the image data in order to facilitate the recognition of the condition of the running surface 18 by an operator of the machine. Reference symbol list 10, 24, 30, 36, 38, 39, 40, 52 measuring wheel 12 cylindrical wheel bodies 14 Surface area 16 bore 18 tread surface 20 wear layer 22 Indicator layer 26 first groove 28 Rotation axis 32 second groove 34 third groove 42 Material 44 Measuring device 46 conveyor belt 48 rotary encoders 50 wave 54 Holding device 56 Component 58 Sensor 60" Monitor The thickness of the wear layer T1 first depth T2 second depth T3 third depth QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 3 091 331 B1

[0004] DE 10 2022 108 742 B4

[0004]

Claims

[1] Measuring wheel (10, 24, 30, 36, 38, 39, 40) for length and / or speed measurements, with a cylindrical wheel body (12) having a lateral surface (14) with a running surface (18), wherein the running surface (18) is at least partially formed by a wear layer (20), characterized by , that a thickness (D) of the wear layer (20) corresponds to a maximum tolerable abrasion of the running surface (18), and that the measuring wheel (10, 24, 30, 36, 38, 40, 52) has at least one wear indicator by which the achievement of the maximum tolerable abrasion of the running surface (18) can be visually detected. [2] Measuring wheel (10, 24, 30, 36, 38, 39, 40) according to claim 1, wherein the thickness of the wear layer is less than 0.8 per mille, preferably less than 0.4 per mille, particularly preferably less than 0.2 per mille of a nominal circumference of the measuring wheel (10, 24, 30, 36, 38, 40, 52). [3] Measuring wheel (10) according to one of the preceding claims, wherein the wear indicator is formed by an indicator layer (22) arranged between the outer surface (14) and the wear layer (20), wherein a color of the indicator layer (22) differs from a color of the wear layer (20). [4] Measuring wheel (24, 30, 36, 38, 39, 40) according to claim 1 or 2, wherein the wear indicator is formed by at least one first groove (26) having a first depth (T1) in the wear layer (20), wherein the first depth (T1) of the first groove (26) corresponds to the thickness (D) of the wear layer (20). [5] Measuring wheel (24, 30, 36, 40) according to claim 4, wherein the groove (26) extends perpendicular to an axis of rotation (28) of the measuring wheel (24, 30, 36, 40). [6] Measuring wheel (38) according to claim 4, wherein the groove (26) runs parallel to the axis of rotation (28) of the measuring wheel (40). [7] Measuring wheel (39) according to claim 4, wherein the groove (26) extends diagonally to the axis of rotation (18) of the measuring wheel (39). [8] Measuring wheel (30, 36) according to one of claims 4 to 7, wherein the working layer (20) has at least a second groove (32) with a second depth (T2), wherein the second depth (T2) is less than the thickness (D) of the working layer (20). [9] Measuring wheel (36) according to claim 8, wherein the working layer 20 has at least a third groove (34) with a third depth (T3), wherein the third depth (T3) is less than the second depth (T2) of the second groove (32). [10] Measuring wheel (40) according to one of claims 4 to 9, wherein at least one groove is filled with a material (42) whose color differs from the color of the wear layer (20). [11] Measuring device (44) for measuring the distance and / or speed of an object (46) moving relative to the measuring device (44), comprising a rotary encoder (48) and a measuring wheel (52) attached to a shaft (50) of the rotary encoder (48) and a holding device (54) for holding the rotary encoder (48), characterized by that the measuring wheel (52) is designed according to one of the preceding claims. [12] Measuring device (44) according to claim 11, wherein the measuring device (44) comprises at least one sensor (58) for optically detecting and generating image data of the measuring wheel (52), in particular the running surface (18) and / or the thickness (D) of the wear layer (20) of the measuring wheel (52). [13] Measuring device (44) according to claim 12, wherein the measuring device (44) comprises a display device (60) which is configured to receive and output the image data of the measuring wheel (52), in particular the running surface (18) and / or the thickness (D) of the wear layer (20) of the measuring wheel (52), from the sensor (58). [14] Measuring device (1) according to claim 12 or 13, wherein the measuring device (44) comprises an evaluation unit configured to receive and evaluate the image data of the measuring wheel (52), in particular the running surface (18) and / or the thickness (D) of the wear layer (20) of the measuring wheel (52) from the sensor (58).

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