Patent Application
20240361279
The present invention is based on a measuring arrangement in a transport device for a metal strip,
Such a measuring arrangement is known. Reference can be made to WO 98/38482 A1 purely as an example. The flatness of the metal strip can be determined from the determined amplitudes of the mechanical vibrations of the areas of the metal strip. This is also explained in more detail in the aforementioned WO publication. A similar disclosure content can also be found in the technical article “Non-contact measurement of strip flatness” Steel Times International, July/August 2003, pages 16 and 17.
From the technical paper “New developments improve hot strip shape: Shapemeter-Looper and Shape Actimeter” by George F. Kelk et al., Iron and Steel Engineer, August 1986, pages 48 to 56, a measuring arrangement in a transport device for a metal strip is known, in which the measuring arrangement is arranged between a front device and a rear device of the transport device, said rear device being arranged downstream of the front device. The measuring arrangement has a mechanical excitation device by means of which the metal strip can be excited so as to vibrate mechanically in its thickness direction at an excitation frequency. The measuring arrangement also has a metal plate whose upper side faces the metal strip. A plurality of sensor elements is arranged in a substructure below the metal plate. The sensor elements are offset from one another as viewed in the width direction of the metal strip. It is possible by means of the sensor elements to acquire for each of the multiple areas of the metal strip that are offset from one another in the width direction a measurement signal that is characteristic of the amplitude of the excited mechanical vibration of the respective area of the metal strip can be acquired. The sensor elements protrude beyond their surroundings within the substructure.
A measuring arrangement in a transport device for a metal strip is known from U.S. Pat. No. 3,538,765 A, in which the measuring arrangement is arranged between a front device and a rear device of the transport device, said rear device being arranged downstream of the front device. The measuring arrangement has a metal plate, the upper side of which faces the metal strip. A plurality of sensor elements are arranged in the metal plate, offset from one another in the width direction of the metal strip. The sensor elements can be used to acquire a measurement signal for multiple areas of the metal strip that are offset from one another in the width direction. The sensor elements are arranged in the metal plate in such a way that they are flush with the upper side of the metal plate towards the metal strip. A synthetic, abrasion-resistant layer is applied to the upper side of the metal plate. This also appears to apply to the areas where the sensor elements are located.
When rolling metal strips the flatness of the rolled metal strip is an important quality feature. In particular, it should be avoided that the rolled metal strip becomes wavy after rolling.
For example, a measuring arrangement of the type mentioned above can be used to record the corresponding measured values. In particular, such measuring arrangements have the advantage over conventional measuring arrangements that the signal acquisition is contactless and therefore there is no risk of damaging the metal strip. However, such measuring arrangements also have some disadvantages.
Thus, in practice, for example, the sensor elements are installed in the metal plate in such a way that they are flush with the upper side of the metal plate. As a result, the sensors of the sensor elements—i.e. the elements that acquire the measurement signals—are laterally surrounded by the material of the metal plate. This results in signal attenuation. The acquired measuring signals therefore have a relatively low level and consequently a relatively low signal-to-noise ratio (SNR). Furthermore, in practice the acquired measurement signals are transmitted to the evaluation device as analogue signals via cable. Due to the long cables, distortions caused by temperature influences, crosstalk and other interference are possible. This makes it difficult to evaluate the acquired measurement signals.
The object of the present invention is to create possibilities by means of which the disadvantages of the prior art can be avoided.
The object is achieved by a measuring arrangement with the features of claim 1. Advantageous embodiments of the measuring arrangement according to the invention are the subject of the dependent claims 2 to 13.
According to the invention, a measuring arrangement of the type mentioned at the beginning is configured as follows,
On the one hand, this means that the sensor elements are no longer surrounded by metal on the sides, resulting in higher signal levels and therefore a better signal-to-noise ratio. Nevertheless, the sensor elements are protected from influences emanating from the metal strip due to the cover on their upper side and are protected from other environmental influences such as dust, dirt, water vapor, etc. due to their lateral sealing. The measuring arrangement is therefore very sensitive on the one hand, yet robust on the other.
Preferably, the cover has recesses on its underside that faces the sensor elements, so that a number of flow channels for a cooling medium are formed between the metal plate and the cover, wherein the sensor elements can be cooled by means of said cooling medium. This allows the sensor elements to be kept at a relatively constant temperature so that temperature influences when acquiring the measurement signals do not occur or can at least be minimized. Furthermore, the service life of the sensor elements can be increased by cooling.
The cooling medium is usually a gas. In particular, the cooling medium can be (purified) compressed air. In exceptional cases, however, a liquid can also be used as the cooling medium, for example an oil.
Preferably, the flow channels are designed in such a way that, with respect to one of the flow channels, the sensor elements are arranged sequentially one behind the other as viewed in the direction of flow of the cooling medium. This ensures that all sensor elements of the corresponding flow channel are forcibly cooled by the cooling medium.
It is preferably provided:
On the one hand, this ensures that the distance between the sensor elements and the metal strip is only slightly increased by the cover. On the other hand, this ensures that the cooling medium that is flowing through the respective flow channel is forced to flow around each sensor element of the respective flow channel, thereby forcing each sensor element to be cooled efficiently.
The mechanical excitation device often has a flat boundary surface that is facing the metal strip. In this case, the upper side of the cover preferably lies in the plane formed by the flat boundary surface. This results in an optimum coordination of the excitation device and the arrangement of the sensor elements including their cover.
The cover must be sufficiently mechanically stable and also sufficiently temperature-resistant. This can be achieved, for example, by the cover being made of ceramic or a (suitable) plastic.
Ceramics are generally dimensionally stable even at higher temperatures. This is not always the case with plastics. However, plastics are also known which are temperature-resistant to the required extent. Examples of such plastics are polyimides and polyester ester ketones (PEEK).
Preferably, channels for a cooling liquid are arranged in the metal plate, wherein the metal plate and thus indirectly also the sensor elements can be cooled by means of said cooling liquid. This can further improve the cooling of the sensor elements.
In a preferred embodiment, the following is also provided,
The sensor element is therefore the mechanical unit that is built into the metal plate. The sensor, on the other hand, is the element of the sensor element that actually acquires the measurement signals. The fixing element is the element that mechanically interacts with the metal plate.
The configuration of the sensor elements with sleeve, sensor and fixing element makes it possible to pre-assemble the sensor elements. In particular, this allows the distance between the upper edge of the sensor and the upper edge and/or the lower edge of the collar to be set precisely during the manufacture of the sensor element. This allows the sensor element to be fixed in a simple manner in the metal plate in such a way that the sensor has a defined distance from the upper side edge of the cover. The connection between the sleeve, sensor and fixing element is preferably non-detachable. For example, the aforementioned elements can be glued together, welded together or soldered together.
Preferably, the metal plate has receptacles for the sensor elements and each of said receptacles in turn has a radially inwardly projecting support ring for the respective collar of the respective sensor element. This allows the sensor elements to be fixed in the metal plate in a simple and precise manner and, above all, with an exact height position (i.e. as viewed in the direction of the metal strip).
Preferably, a plastic hood is applied to the respective sensor on its side facing the metal strip so that the respective sensor is sealed airtight and watertight insofar as it protrudes beyond the metal plate. This protects the sensor even better from environmental influences.
The sensor elements usually comprise eddy current sensors. In this case, the eddy current sensors of sensor elements that are arranged directly adjacent to each other in the metal plate are preferably operated at different operating frequencies. This can significantly reduce crosstalk. The minimum number of operating frequencies is two. In many cases it is three.
Preferably, the sensor elements have a coding that is characteristic of the operating frequency of the respective sensor element. The coding is such that it can be directly perceived by a person with their sensory organs. As a result, the sensor elements can be distinguished from one another by an operator in a quick and simple manner, so that installation of the sensor elements at the “correct” points on the metal plate is guaranteed. The coding can be of a mechanical and/or haptic and/or optical nature as required. In the case of mechanical coding, it may even be possible to make it impossible to install a sensor element in the “wrong” position on the metal plate.
Alternatively or additionally, for example, an evaluation device can check the operating frequency at which the sensor elements are working in each case. In this case, if it is stored in the evaluation device which sensor is to operate at which operating frequency, the evaluation device can carry out the check and issue an error message in the event of an error.
The characteristics, features and advantages of this invention described above and the manner in which they are achieved will become clearer and more comprehensible in connection with the following description of the embodiments, which will be explained in more detail in connection with the drawings. Hereby in a schematic illustration:
According to
A further roll stand can be arranged upstream of the roll stand on the in-feed side. Multiple further roll stands can also be arranged upstream of the roll stand on the in-feed side. It is also possible, for example, that a decoiler for uncoiling the metal strip 1 is arranged directly upstream of the roll stand. The front device 2 itself can also be a device other than a roll stand. Examples of such devices are a drive roller set and a decoiler. Which of these embodiments is given is of secondary importance in the context of the present invention. For this reason, the configuration of the rolling facility on the inlet side of the front device 2 is also not shown in the FIGS and is also not explained in more detail.
The transport device also has a rear device 3. The rear device 3 is arranged downstream of the front device 2. The rear device 3 can, for example, comprise a reel 4 and a deflection roller 5 upstream of the reel 4 as shown in
Various devices can be arranged between the front device 2 and the rear device 3, said various devices being of secondary importance in the context of the present invention, for example a thickness measuring device. The decisive factor in the present case is that a measuring arrangement 6 is arranged between the front device 2 and the rear device 3.
The measuring arrangement 6 has a mechanical excitation device 7. By means of the mechanical excitation device 7, the metal strip 1 can be excited so as to vibrate mechanically in its thickness direction. Specifically, the metal strip 1 is shown in
The mechanical excitation device 7 can, for example, be designed as a suction device as shown in
For example, a suction fan 9 can extract air from the area between the metal strip 1 and the measuring arrangement 6 via suction openings 10 (see in particular
As already mentioned, this configuration is well established. Detailed explanations are therefore not necessary.
In order to be able to cause the metal strip 1 to vibrate effectively, the mechanical excitation device 7 usually has a flat boundary surface 13. The flat boundary surface 13 faces the metal strip 1 and runs at a small distance (usually in the single-digit millimeter range) from the pass line. The suction openings 10 are arranged in the boundary surface 13.
The measuring arrangement 6 also has a metal plate 14 as shown in
A plurality of sensor elements 16 is arranged in the metal plate 14 as shown in
The cover 17 consists of an electrically insulating material. For example, the cover 17 can be made of a ceramic or a plastic. Suitable ceramics and suitable plastics, for example polyimides and polyester ester ketones (PEEK), are known to those skilled in the art.
The sensor elements 16 are arranged offset from one another as viewed in the width direction of the metal strip 1. In the specific embodiment of the present invention, the sensor elements 16 form two rows, with the corresponding sensor elements 16 being arranged next to one another within the respective row as viewed in the width direction, and the sensor elements 16 of the rows being arranged offset relative to the sensor elements 16 of the other rows as viewed in the width direction in the overall view of the rows. This configuration, i.e. with multiple rows of sensor elements 16 and rows offset from one another, is currently preferred, but is of secondary importance as a result.
It is possible by means of the sensor elements 16 to acquire for a respective area of the metal strip 1 a respective measurement signal MA that is characteristic of the amplitude A of the excited mechanical vibration of the respective area of the metal strip 1. The areas of the metal strip 1 are also offset from one another in the width direction of the metal strip 1 in accordance with the arrangement of the sensor elements 16.
The acquisition of the respective measurement signal MA is contactless. Possible configurations for this are generally known to persons skilled in the art. It is preferable that the sensor elements 16 (=assembly unit) comprise eddy current sensors as actual sensors 19 which acquire the respective measurement signal MA. In an eddy current sensor—see
The excitation current IA has an excitation frequency f, hereinafter referred to as the operating frequency so as to distinguish it from the excitation frequency fA. The operating frequency f is usually in the range of multiple kHz, sometimes even in the single-digit MHz range. The measurement signal MA also has the operating frequency f. The respective prevailing distance of the respective area of the metal strip 1 from the measuring arrangement 6 can thus be determined from the measuring signal MA in a manner known per se. The development of this distance over time provides the amplitude A of the mechanical vibration of the corresponding area of the metal strip 1.
This procedure is generally known and familiar to persons skilled in the art. It therefore does not need to be explained in detail.
According to
When the cover 17 is mounted on the metal plate 14, the sensor elements 16 are immersed in the receptacles 21 (of course only insofar as they protrude beyond the upper side 15 of the metal plate 14).
The cover 17 also has recesses 22 on its underside. In
In the illustration according to
According to
It can also be seen from
The cooling medium 23 can be (purified) compressed air, for example. This configuration offers the additional advantage that minor leakages are not critical. This is because the compressed air has a higher pressure than the ambient air. Despite the leakage no foreign bodies can therefore penetrate into the space that is covered by the cover 17. Nevertheless, the cooling of the sensor elements 16 can be maintained if the leakage is small enough.
In some cases, it may be sufficient to cool the sensor elements 16 solely with the cooling medium 23. In other cases, it is necessary to arrange channels 26 for a cooling liquid in the metal plate 14 as shown in the schematic diagram in
The structure of an individual sensor element 16 is explained in more detail below in conjunction with
According to
According to
The components, i.e. the sensor 19, the sleeve 27 and the fixing element 28, are fixed relative to each other. For example, the sensor 19 can be glued into the sleeve 27 and the fixing element 28 can be fixed to the sleeve 27 via soldering points or spot welds. When mounting the sensor element 16, the distance between the lower edge or the upper edge of the collar 31 and the upper side of the sensor 19 (or, if present, the upper side of the plastic hood 29) can be set in a defined manner. For example, the sensor 19 can be fixed in the sleeve 27 first. Before or after this, the plastic hood 29 can be placed on the sensor 19 if necessary. The distance between the lower edge or the upper edge of the collar 31 is then set. Only finally is the fixing element 28 fixed to the sleeve 27.
The metal plate 14 has—see in particular
As already explained above, the sensor elements 16 can be used to acquire a respective measurement signal MA for the areas of the metal strip 1. The acquisition is contactless, usually via eddy current sensors. For this purpose, the eddy current sensors have excitation coils 20 to which excitation currents IA of multiple kHz, sometimes even in the single-digit MHz range, are applied. The acquired measurement signals MA are initially analogue.
In the prior art, the measurement signals MA are transmitted via corresponding cables to an evaluation device 34 (see
As in the prior art, the evaluation device 34 is arranged outside the measuring arrangement 6, for example in a control cabinet. In the simplest case, the digitization devices 35 transmit the digitized measurement signals themselves to the evaluation device 34 as transmitted signals MA′. Alternatively, the digitization devices 35 can transmit signals derived from the digitized measurement signals to the evaluation device 34 as transmitted signals MA′.
The arrangement of the digitization devices 35 within the measuring arrangement 6 can be as required. For example, the digitization devices 35 can be designed as independent elements separate from the sensor elements 16 as shown in
The digitization devices 35 are shown in
The cables 36 are generally detachably connected to the digitization devices 35, for example via a screw connection or a bayonet-type connection. At the transition to the sensor elements 16, the cables 36 are preferably hermetically sealed (i.e. airtight and watertight). The seal can be made, for example, as is known for the spark plug connectors of motor vehicle engines, by means of rubber-elastic sleeves which are slidably arranged on the corresponding cable 36. Alternatively—and this is currently preferred—the cables 36 can be non-detachably connected to their respective sensor element 16.
With regard to the connection of the digitization devices 35 to the evaluation device 34, it is possible in principle to establish the connection via individual corresponding connection cables, as is done for the transmission of the analogue measurement signals MA in the prior art. However, it is preferable if the transmitted signals MA′ are transmitted to the evaluation device 34 via a common armored cable 37 with pre-assembled connections 38 as shown in
According to
The armoring 43 of the armored cable 37 can, for example, correspond to that which is usual for hydraulic lines whose hydraulic fluid is under a pressure in the range from 100 bar to 500 bar.
The dashed line L in
It is evident that the eddy current sensors of sensor elements 16, which are arranged directly adjacent to each other in the metal plate 14, are operated at mutually different operating frequencies f1, f2, f3. This allows any crosstalk behavior to be significantly reduced.
In the case of mutually different operating frequencies f1, f2, f3, it is also possible, as shown in
In the case of mutually different operating frequencies f1, f2, f3, the sensor elements 16 preferably have a coding 44 as shown in
Preferably, the digitization devices 15 also have a corresponding coding 45, so that the correct assignment is also readily apparent.
As shown in
In order to determine the amplitudes A, the evaluation device 34 first performs a linearization of the transmitted signals MA′ in a linearization block 46. The linearization block 46 thus outputs modified signals MA″, the respective value of which is proportional to the corresponding deflection of the respective area of the metal strip 1 at the time at which the corresponding (analogue) measurement signal MA was acquired. As part of the linearization process, the evaluation device 34 evaluates a characteristic curve K. The characteristic curve K is determined by the evaluation device 34 specifically for the metal strip 1. It can be determined, for example, as a function of geometric properties G and/or chemical properties C and/or thermodynamic properties T (for example temperature) and/or the history H of the metal strip 1. If necessary, an operating temperature T′ of the sensor elements 16 can also be taken into account when determining the characteristic curve K.
In order to determine the characteristic curve K, for example, the associated characteristic curves K can be stored in a determination device 47 for specific values of the geometric properties G, the chemical properties C, etc., so that the characteristic curve K actually utilized can be determined by selection and/or interpolation.
The modified signals MA″ are fed to a determination block 48 within the evaluation device 34. In the determination block 48, the evaluation device 34 determines the respective amplitude A of the excited mechanical vibration of the metal strip 1 for the areas of the metal strip 1. In the context of determining the amplitudes A, the evaluation device 34 preferably uses a Goertzel algorithm as shown in
The determined amplitudes A can be fed to a further determination block 49. In the determination block 49, the evaluation device 34 uses the amplitudes A to determine a flatness error PF for each of the areas of the metal strip 1. The determination of the flatness errors PF as such is no longer the object of the present invention. The evaluation device 34 can, for example, output the determined flatness errors PF to a control device (not shown) for the front device 2, so that the control device can activate flatness actuators of the front device 2 in such a way that the flatness errors PF are eliminated as far as possible.
The present invention has many advantages. The use of the cover 17 improves the sensitivity of the sensors 19. The replacement of the sensor elements 16 is significantly simplified. By configuring the sensor elements 16 as pre-assembled units, the positioning of the sensor elements 16 in the metal plate 14 can also be ensured reliably and precisely. This also applies to the subsequent replacement of a defective sensor element 16 with a new sensor element 16. The configuration of the sensor elements 16 as pre-assembled units also reduces the protection of the sensors 19 against moisture, dirt and, within limits, against high heat input. This improves the durability of the sensor elements 16. The cooling of the sensor elements 16 by means of the cooling medium 23 also provides improved protection against dirt and moisture. Crosstalk can be largely eliminated by using multiple operating frequencies f1, f2, f3. Thanks to the very early digitization of the measurement signals MA within the measuring arrangement 6, the measurement signals MA can be converted very quickly into a form that is immune to interference. This enables, among other things, an increase in the analyzable measuring range. Evaluation in conjunction with characteristic curves K, which are specific to the metal strip 1, also enables improved evaluation and evaluation in an enlarged measuring range. By using the characteristic curve K, an evaluation of the measurement signals MA is possible that is optimized for the respective metal strip 1. The evaluation using a Goertzel algorithm provides superior results with reduced computational effort.
Although the invention has been illustrated and described in detail by the preferred exemplary embodiment, the invention is not limited by the disclosed examples and other variants can be derived by the person skilled in the art without departing from the scope of protection of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21193743.8 | Aug 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/073329 | 8/22/2022 | WO |
