Device and method for the non-destructive magnetic testing of a chain

Abstract

Device (10) for magnetically testing a chain (11) with several chain links (12), wherein the device (10) can be arranged on an axial section (21) of the chain (11) and is movable relative to the chain (11) or conversely the chain (11) is movable relative to the device (10) in the longitudinal direction (45a) of the chain (11), comprising: - a magnet arrangement (20) with several magnets which are configured to form a magnetic field (22) in the axial section (21), preferably in the longitudinal direction (45a) of the chain (11); - a guide device (19) for guiding the chain (11); - a sensor arrangement (24) with a plurality of magnetic field sensors (25) which are arranged in a sensor area (43) in the axial section (21) on a line (26) encircling the chain (11);- a length measuring device (27) configured to determine the relative path length (33) between the sensor arrangement (24) and the chain (11), wherein the length measuring device (27) has several magnetic field sensors (53) arranged longitudinally (45a) to the chain (11), which are configured to detect relative movements between the device (10) and the chain (11); and - an evaluation unit (30) configured to receive measurement data (31) from the magnetic field sensors (25), to assign these data to a circumferential position (32) and the detected path length (33) with spatial resolution, and to detect defects (34) in the chain (11) in the spatially resolved measurement data (31).

Description

The invention relates to devices and methods for the non-destructive, magnetic testing of a chain. Chains are used in a wide variety of technical applications, such as in production and industrial plants, as drive chains, and in lifting equipment. During operation, individual chain links can become damaged and / or deformed, for example, longitudinally, causing the chain to stretch, or transversely, causing individual links to bend. Longitudinal or transverse deformation, or damage to the chain links, can render the chain completely unusable and necessitate replacement. Continuing to use deformed or broken chain links can damage components interacting with the chain, such as sprockets, guides, or similar parts. This can lead to the shutdown of entire production lines. Furthermore, in safety-critical applications, this can pose a risk to life and limb.It is therefore desirable to detect changes in the condition of the chain as early as possible during operation. In DE 10 2014 225 834 B4 a drive chain length testing system is described which has a measuring device with a horizontal detection sensor and a vertical detection sensor with which elongations of the drive chain can be determined. DE 10 2016 015 364 A1 also describes a method for determining geometric characteristics of chain links of a link chain, in which visible edges are optically detected and the geometric characteristics of the chain links are determined from this. Optical methods for detecting deformations are prone to errors, especially when the chain is dirty. Furthermore, defects in individual chain links can be concealed if the geometry of the chain links is determined from only a few directions. Furthermore, magnetic testing devices for the non-destructive testing of chains, ropes, or similar elongated test specimens are known, in which the test specimen is magnetized and magnetic fields or changes in magnetic flux are detected and evaluated by means of suitable sensor devices. Such devices are known, for example, from DE 10 2019 004 240 A1, KR 10 2021 0 105 167 A, DE 38 21 070 A1, US 5 321 356 A, and WO 2015 / 030 600 A1. Based on this, the object of the invention is to provide an improved device and an improved method for the non-destructive, magnetic testing of a chain, which enables improved spatially resolved detection and evaluation of defects along the chain. The problem is solved by the device according to claim 1 and the testing method according to claim 11. The device according to the invention for the non-destructive, magnetic testing of a chain with several chain links can be arranged, in particular, on an axial section of the chain and moved relative to the chain, or conversely, the chain can be moved relative to the device in the longitudinal direction of the chain. The device according to the invention comprises a magnet arrangement, a sensor arrangement, a length measuring device, and an evaluation unit. The magnet arrangement includes several magnets with which a magnetic field is generated. The generated magnetic field extends, in particular, in the longitudinal direction of the chain. The magnet arrangement can, for example, have a first magnetic area at a first axial position of the axial section and a second magnetic area at a second axial position of the axial section 21, between which the magnetic field is generated. Alternatively, the generated magnetic field can also extend in the transverse direction of the chain.The sensor arrangement comprises a plurality of magnetic field sensors positioned along a line encircling the chain within a sensor area at an axial position of the axial section. This chain-encircling line preferably encloses the entire chain. The line can be adapted to the outer contour of the chain, for example, by having a cross-shaped form. The length measuring device is configured to determine the relative path length between the sensor arrangement and the chain. It includes several magnetic field sensors arranged in the chain direction, configured to detect relative movements between the device and the chain. The evaluation unit is configured to receive measurement data from the magnetic field sensors, spatially assign this data to a circumferential position and the measured path length, and detect defects in the chain within the spatially resolved measurement data. This makes it possible to detect defects in individual chain links early in the operation, before individual chain links can break and thus the chain can fail completely. A special feature of the present invention is that the magnetic field sensors completely encircle the chain, thereby enabling the detection of magnetic field variations across the entire circumference of the chain. This allows for the detection of defects in individual chain links that would otherwise occur in difficult-to-access locations. Such defects in the chain can include, for example, indentations, deformations of the chain links, cracks in the chain links, and the like. To detect defects in the chain links, the evaluation unit is preferably configured to compare the spatially resolved measurement data in the circumferential direction with a reference function, for example by correlating or convolving the reference function with the spatially resolved measurement data. The reference function can be, for example, a rectangular function or the absolute value of a trigonometric function such as a sine or cosine function. The magnetic areas can contain permanent magnets, such as rare-earth magnets, or electromagnets to generate the magnetic field. In particular, the line encircling the chain, on which the magnetic field sensors of the sensor array are arranged, is adapted to a transverse clearance of the chain. This transverse clearance is specifically the sum of the transverse outlines of at least two chain links. Adapting the encircling line to the chain's clearance allows even hard-to-reach areas on the chain links to be reliably detected by the magnetic field sensors, enabling the detection of defects in these areas. Preferably, the guide device has several guide surfaces on which the individual chain links are guided. The guide device can be designed as a single piece or in multiple parts. If the guide device is designed as a single piece, it can have at least one guide element on which the multiple guide surfaces are arranged. The guide element can be made of a plastic such as polyamide or the like. Alternatively, the guide device can also have one or more spring-loaded rollers, in which the rolling surfaces of the rollers form the guide surfaces of the guide device. Regardless of the specific design of the guide device, it is configured to establish a relative alignment between the sensor assembly and the individual chain links. This alignment of the chain links can then be maintained by the guide device during the testing process. If the guide device has at least one guide element, a through-hole can be formed in the guide element, the flanks of which form the guide surfaces for the chain links. Preferably, the contour of the through-hole is adapted to the transversely summed outlines of at least two chain links. It is preferred that the through-hole be cross-shaped. The through-hole may be designed with clearance relative to the contour of the chain. The device features, in particular, an openable housing in which a test bore is formed, extending from a first side of the housing to an opposite second side of the housing. Preferably, the magnet arrangement and the sensor arrangement are housed within the housing, thereby protecting them from dirt and other external influences. Preferably, the magnet arrangement and the sensor arrangement are arranged at least partially around the test bore. It is also preferred that the guide device is arranged, at least partially, within the test bore. The guide device can have at least one additional guide element by which the chain is guided within the device. For example, the first guide element can be located in one entry area of ​​the test bore and the additional guide element in the other entry area of ​​the test bore. Alternatively, the guide device can also have only one guide element that extends along the entire length of the test bore. The sensor arrangement can further comprise at least one measuring coil that extends at least partially (in the circumferential direction) around the chain. The sensor arrangement can also comprise several such measuring coils. The measuring coil can be designed as a single piece or in multiple parts. Furthermore, the one or more measuring coils can be arranged offset from the magnetic field sensors along the longitudinal axis. Preferably, the evaluation unit is configured to fuse the measurement data from the magnetic field sensors with the measured path length of the length measuring device and, preferably, with the measurement data from the measuring coil in such a way that at least a three-dimensional measurement image of the measured magnetic field strengths in the circumferential and longitudinal directions of the chain is generated. This allows a complete measurement image of the chain to be generated. The evaluation unit is also specifically designed to detect error patterns in the three-dimensional measurement image that indicate a misalignment in the chain. In particular, the evaluation unit is designed to mark these error patterns and place a virtual marker in the measurement data at the detected error pattern location. The length measuring device comprises a plurality of sensors arranged in the direction of the chain. These sensors can extend along at least a portion, for example, at least 25%, 40%, 50%, 60%, or 70% of the length of the axial section. The sensors can be designed as magnetic field sensors, enabling the determination of the relative motion between the device and the chain. The plurality of magnetic field sensors, together with the sensor arrangement, can form a sensor unit or separate sensor units. The evaluation unit can include a length measuring module configured to determine the relative motion between the device and the chain from the data of the additional (magnetic field) sensors. Furthermore, the additional sensors can also be designed as optical sensors, configured to determine the relative motion between the device and the individual chain links. The device can also include a storage unit and a communication interface configured to temporarily store the measurement data from the sensor arrangement and the longitudinal measuring device as needed and to send this data to the evaluation unit. In this embodiment, the evaluation unit is located within the device housing. Alternatively, the evaluation unit can be located within the device housing. In this embodiment, the evaluation unit can have a communication interface configured to connect to other user devices in order to transmit the processed and evaluated measurement data to these devices. Furthermore, the problem is solved by a method for the non-destructive magnetic testing of a chain. The method according to the invention comprises: - Arranging the chain to be tested in an axial section in which a magnetic field is generated such that the chain is located longitudinally within the generated magnetic field; - Determining the magnetic field strength on a line encircling the chain, which is arranged transversely to the longitudinally generated magnetic field; - Determining the relative path length between the sensor arrangement and the chain; - Assigning the measurement data from the magnetic field sensors to a circumferential position and the measured path length, preferably by creating an associated, spatially resolved measurement image; and - Detecting defects in the chain in the associated measurement data. The features and advantages described in connection with the device according to the invention are applicable accordingly to the method according to the invention. Further details of advantageous embodiments or aspects of the invention will become apparent from the drawings, the description, and the dependent claims. Figure 1 shows an example of the device according to the invention; Figure 2 shows an example of the magnet arrangement and the sensor arrangement of the test device; Figure 3A shows an example of the guide device and the sensor arrangement; Figure 3B shows another example of the guide device with the sensor arrangement; Figure 4 shows a schematic view of the signal processing of the device according to the invention; Figures 5A-5E show examples of defects in a chain. Fig. 1 shows an example of a device 10 according to the invention for the non-destructive testing of a chain 11 with a plurality of chain links 12. The device 10 has a housing 13 which is designed to be opened. For opening the housing 13, it has an upper housing shell 14 and a lower housing shell 15. The housing 13 also has a first side 16 and a second side 17 opposite the first side 16, with a test bore 18 extending from the first side 16 to the second side 17. The chain 11 to be tested is arranged within the test bore 18 during the test. In the example shown in Fig. 1, a guide device 19 is also arranged within the test bore 18, which is designed to guide the chain links 12 of the chain 11 within the device 10 during the test process.The device 10 also has a magnet arrangement 20, which is arranged such that a magnetic field 22 is arranged in an axial section 21 in the longitudinal direction of the chain 11. The device 10 or the chain 11 can be moved relative to each other along a longitudinal direction 45a of the chain 11, as indicated by the arrows 23 in Fig. 1. A transverse direction 45b of the chain 11 is defined transverse to the longitudinal direction 45a. In the axial section 21, a sensor arrangement 24 with a plurality of magnetic field sensors 25 is also arranged on a line 26 encircling the chain 11. The length measuring device is formed by a plurality of magnetic field sensors 53 arranged in the longitudinal direction 45a of the chain 11, as shown in dashed lines in Fig. 1. The arrangement, together with the sensor arrangement 24, can form a T-shaped arrangement (as shown) in the side projection. Alternatively, the arrangement can also form an L-shaped arrangement in the side projection or comprise two or more ring-shaped magnetic field sonores. In this case, it is no longer necessary for the device 10 to have an additional length measuring device 27 outside the housing 13. Rather, the length measuring device 27 is already implemented within the housing 13 in the form of the additional plurality of magnetic field sensors 53. The details of the sensor arrangement 24 are described in detail below with reference to Fig. 2, Fig. 3A, and Fig. 3B. Figure 1 also shows a length measuring device 27, which, however, is not part of the invention. This length measuring device 27 has a measuring wheel 28 which is rotatably mounted about an axis and pivotably attached to the housing 13 by means of an arm 29. The measuring wheel 28 can be spring-loaded against the chain 11 via the arm 29. Furthermore, the device 10 has an evaluation unit 30 which is configured to receive measurement data 31 from the magnetic field sensors 25 and the length measuring device 27, to assign these to a circumferential position 32 and a recorded path length 33 with spatial resolution and to detect defects 34 in the spatially resolved measurement data. Furthermore, the device 10 has a communication interface 35, which is configured to communicate with user terminals, for example, to communicate detected defects 34 or the spatially resolved measurement data to the user terminal 36. The device 10 may also have a storage device 37, which may be configured to temporarily store measurement data from the sensors 25, 27 and / or the evaluation unit 30. Fig. 2 illustrates the magnet arrangement 20 together with the sensor arrangement 24 and the chain 11 to be tested. The magnet arrangement 20 has a first magnet section 38 at a first axial position 39 and a second magnet section 40 at a second axial position 41 of the axial section 21. The first magnet section 38 and the second magnet section 40 are connected to each other via a yoke 42. The first magnet section 38 has, in particular, permanent magnets that are polarized in the opposite direction to the permanent magnets of the second magnet section 40. In Fig. 2, the negative poles are labeled N and the positive poles S. The field lines of the magnetic field 22 formed between the first magnet section 38 and the second magnet section 40 are shown as dashed lines in Fig. 2. The magnetic field 22 extends longitudinally to the chain 11. Unlike in Fig.As shown in Figure 2, the first magnetic area 38 and the second magnetic area 40 can also contain electromagnets, between which the magnetic field 22 is constructed accordingly. The sensor arrangement 24 comprises a plurality of magnetic field sensors 25, which are arranged in a sensor area 43 at a third axial position 44 located between the first and second axial positions 39, 41 on a line 26 encircling the chain. The magnetic field sensors 25 are, for example, designed as Hall sensors. In Fig. 2, a length measuring device 27 is further shown in dashed lines, which is realized by the plurality of magnetic field sensors 53, from whose data the relative path length between the device 10 and the chain 11 can be determined. Fig. 3A shows an exemplary cross-section of the sensor arrangement 24. In the example shown in Fig. 3A, the magnetic field sensors 25 are arranged on a circular line 26 around the chain 11. The magnetic field sensors 25 are arranged equidistant from each other on the line 26. Figure 3A also shows an example of the guide device 19. In the example shown here, the guide device 19 has a guide element 46 in which a cross-shaped through-hole 47 is formed. The individual chain links 12 of the chain 11 are guided in the cross-shaped through-hole 47. The flanks of the through-hole 47 form guide surfaces 48 for the individual chain links 12. The dimensions of the through-hole 47 are adapted to the dimensions of the chain links, with the through-hole having a clearance fit with the chain 11. The guide element 46 can be interchangeably connected to the test device 10. In particular, the test device 10 can have many different elements 46, each adapted to different chains 11. Fig. 3B shows another example of the sensor arrangement 24 together with the guide device 19. The above statements relating to Fig. 3 apply accordingly to the example shown in Fig. 3B, with reference to the reference numerals. The example shown in Fig. 3B differs from the example shown in Fig. 3A in that the sensor arrangement 24 has more magnetic field sensors 25 than the example shown in Fig. 3A. Furthermore, the two examples differ in that these magnetic field sensors 25 in Fig. 3B are not arranged on a circular circumferential line 26, but rather on a line 26 adapted to the cross-sectional contour of the chain 11. In particular, the line 26 shown in Fig. 3B is not circular. Fig. 4 schematically shows the signal processing of the device 10 according to the invention. The measurement data 31 from the magnetic field sensors 25 and the path lengths 33 from the length measuring device 27 are received by the evaluation unit 30. The evaluation unit 30 can be configured to fuse the received data in such a way that at least a three-dimensional measurement image 52 of the detected magnetic field strength in the circumferential direction 32 and in the longitudinal direction 33 of the chain 11 is generated. The evaluation unit 30 is also configured to detect defective patterns 49 in the three-dimensional measurement image 52. In the example shown in Fig. 4, several regular patterns 50 are depicted, which result from the eyelets of the individual chain links 12 in connection with the relative movement. In addition, Fig. 4 shows a defective pattern 49, which indicates a crack in a chain link 12.Information about the defect pattern 49 and the defects 34 detected in the measurement data 31, 33 can be virtually marked by the evaluation unit 30. This information, or the raw data underlying the information, can be stored in a storage device 37 and / or transmitted via the communication interface 35, for example, to a user terminal 36 or an external computing device, such as a computer, a server, or cloud, and processed, displayed, or stored there. Figures 5A, 5B, 5C, 5D, and 5E show several different examples of defects 34 in a chain link 12 of the chain 11. In Figure 5A, one of the chain links 12 has a notch 34. In the example shown in Figure 5A, the notch does not yet affect the chain link length 51. However, it can be detected and identified at an early stage using the device 10. Figure 5B shows a defect 34 in which a chain link 12 is completely broken. In the example shown in Figure 5B, the chain link length 51 of the affected chain link 12 is also not yet increased. Figure 5C also shows a crack as a defect 34, but in this example, the chain link length 51 is increased compared to the regular chain link length. Fig. 5D also shows a defect 34 where a chain link 12 is bent.This defect 34 is also characterized by a characteristic defect pattern 49 in measurement figure 52. Fig. 5E also shows an example of the chain 11 in which individual chain links 12 have elongated. The elongation 34 of the individual chain links 12 is also recognizable as a defect pattern 49 in measurement figure 52. The invention relates to a device 10 and a method for the non-destructive, magnetic testing of a chain 11 with several chain links 12, which is guided by means of a guide device 19 through a magnet arrangement 20 on an axial section 21, wherein a sensor arrangement 24 with a plurality of magnetic field sensors 25 is arranged in the axial section 21. The magnetic field sensors 25 are arranged on a line 26 encircling the chain 11. The device 10 also includes a length measuring device 27, which is configured to detect the path length of the chain relative to the device 10 or vice versa via additional magnetic field sensors arranged in the chain direction 45a.The device also has an evaluation unit 30, which is designed to receive the measurement data in the magnetic field sensors, to assign them to a circumferential position and the recorded path length with spatial resolution, and to detect defects 34 of the chain 11 in the spatially resolved measurement data. Reference symbol: 10 Device 11 Chain 12 Chain link 13 Housing 14 Upper housing shell 15 Lower housing shell 16 First side of housing 17 Second side of housing 18 Test through-hole 19 Guide device 20 Magnet arrangement 21 Axial section 22 Magnetic field 23 Relative movement between device and chain 24 Sensor arrangement 25 Magnetic field sensors 26 Line 27 Length measuring device 28 Measuring wheel 29 Arm 30 Evaluation measuring unit 31 Measurement data 32 Circumferential position 33 Path length 34 Defect 35 Communication interface 36 User terminal 37 Storage device 38 First magnetic area 39 First axial position 40 Second magnetic area 41 Second axial position 42 Yoke 43 Sensor area 44 Third axial position 45a Longitudinal direction of the chain 45b Transverse direction of the chain 46 Guide element 47 Through-hole 48 Guide surfaces 49 Defect pattern 50 regular pattern 51 chain link length 52 measurement illustration

Claims

Device (10) for magnetically testing a chain (11) with several chain links (12), wherein the device (10) can be arranged on an axial section (21) of the chain (11) and is movable relative to the chain (11) or conversely the chain (11) is movable relative to the device (10) in the longitudinal direction (45a) of the chain (11), comprising: - a magnet arrangement (20) with several magnets which are configured to form a magnetic field (22) in the axial section (21), preferably in the longitudinal direction (45a) of the chain (11); - a guide device (19) for guiding the chain (11); - a sensor arrangement (24) with a plurality of magnetic field sensors (25) which are arranged in a sensor area (43) in the axial section (21) on a line (26) encircling the chain (11);- a length measuring device (27) configured to determine the relative path length (33) between the sensor arrangement (24) and the chain (11), wherein the length measuring device (27) has several magnetic field sensors (53) arranged longitudinally (45a) to the chain (11), which are configured to detect relative movements between the device (10) and the chain (11); and - an evaluation unit (30) configured to receive measurement data (31) from the magnetic field sensors (25), to assign these data to a circumferential position (32) and the detected path length (33) with spatial resolution, and to detect defects (34) in the chain (11) in the spatially resolved measurement data (31). Device (10) according to claim 1, characterized in that the line (26) encircling the chain (11), on which the magnetic field sensors (25) of the sensor arrangement (24) are arranged, is adapted to a light space of the chain (11) in the transverse direction (45b) of the chain (11). Device (10) according to claim 1 or 2, characterized in that the guide device (19) has several guide surfaces (48) on which the chain links (12) of the chain (11) are guided. Device (10) according to one of the preceding claims, characterized in that the guide device (19) has at least one guide element (46), wherein a through hole (47) is formed in the guide element (46), the flanks of which form the guide surfaces (48) for the chain links (12) of the chain (11). Device (10) according to claim 4, characterized in that a contour of the through hole (47) is adapted to the outlines summed in the transverse direction (45b) of at least two chain links (12). Device (10) according to one of the preceding claims, characterized in that the device (10) has an openable housing (13) in which a test through-hole (18) is formed, which extends from a first side (16) of the housing (13) to an opposite, second side (17) of the housing (13). Device (10) according to claim 6, characterized in that the magnet arrangement (20) and the sensor arrangement (24) are housed in the housing (13) and are arranged at least partially around the test passage bore (18), wherein the guide device (19) is preferably arranged at least partially in the test passage bore (18). Device (10) according to one of the preceding claims, characterized in that the evaluation unit (30) is configured to fuse the measurement data (31) of the magnetic field sensors (25) with the detected path length (33) of the length measuring device (27) in such a way that at least a three-dimensional measurement image (52) of the detected magnetic field strength in the circumferential direction and in the longitudinal direction (45a) of the chain (11) can be generated. Device (10) according to claim 8, characterized in that the evaluation unit (30) is configured to detect error patterns (49) in the three-dimensional measurement image (52) which indicate a defect (34) in the chain (11). Device (10) according to one of the preceding claims, characterized in that the device (10) also has a storage unit (37) and a communication interface (35) which are configured to temporarily store the measurement data (31) of the sensor arrangement (24) and the length measuring device (27) as required and to send these to the evaluation unit (30). A method for the magnetic testing of a chain (11), comprising: - Arranging the chain (11) to be tested in an axial section (21) in which a magnetic field (22) is formed, wherein the chain (11) preferably extends longitudinally in the formed magnetic field; - Detecting the magnetic field strength with a plurality of magnetic field sensors (25) of a sensor arrangement (24) in a sensor area (43) in the axial section (21) on a line (26) encircling the chain (11); - Determining the relative path length (33) between the sensor arrangement (24) and the chain (11) using several magnetic field sensors (53) arranged in the longitudinal direction (45a) of the chain (11); - Assigning the measurement data (31) of the magnetic field sensors (25) to a circumferential position (32) and the detected path length (33) and preferably creating an associated, spatially resolved measurement image (52); as well as- detecting defects (34) of the chain (11) in the associated measurement data (31).

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