DEVICE FOR DETERMINING THE THICKNESS OF AN OBJECT

Abstract

With regard to a reliable measurement of the thickness of an object (4) even in an environment with high temperatures, a device (1) is provided for determining the thickness of an object (4), more particularly a strip-like or flat object (4), preferably for use in a hot rolling process, having a frame (2) with at least one leg (5, 6), the at least one leg (5, 6) having a sensor (8a, 8b) for the contactless measuring of the distance to the object (4), which device is characterised in that the at least one leg (5, 6) has a structure consisting of a plurality of layers in order to reduce the temperature effect on the frame (2) and/or on the sensor (8a, 8b).

Claims

1-15. (canceled)

16. Device (1) for determining the thickness of an object (4), the device comprising a frame (2) having at least one leg (5, 6), wherein the at least one leg (5, 6) comprises a sensor (8a, 8b) for contactless measuring of the distance to the object (4), wherein, in order to reduce a temperature effect on at least one of the frame (2) or the sensor (8a, 8b), the at least one leg (5, 6) has a structure consisting of a plurality of layers.

17. Device according to claim 16, wherein the plurality of layers includes a first layer that comprises a base frame element (9) which is preferably configured as a hollow body or is formed by such a base frame element (9).

18. Device according to claim 17, wherein the sensor (8a, 8b) is associated with the base frame element (9) or is disposed in the base frame element (9).

19. Device according to claim 16, wherein the base frame element (9) comprises a cooling device, wherein the cooling device is preferably disposed in or on the base frame element (9).

20. Device according to claim 19, wherein the cooling device comprises a cooling register (14) filled with a cooling medium.

21. Device according to claim 17, wherein the base frame element (9) is such that a specifiable fluid can flow through it.

22. Device according to claim 20, wherein a fluid flow is implemented by means of a forward flow (18a) from the cooling device to the sensor (8a, 8b) and a return flow from the sensor (8a, 8b) back to the cooling device.

23. Device according to claim 17, wherein a second layer comprises a preferably substantially closed jacket (11) for the first layer or is formed by such a jacket (11), wherein the return flow or the forward flow is preferably implemented between the jacket (11) and the base frame element (9).

24. Device according to claim 23, wherein the jacket (11) is composed of a plurality of segments which are preferably coupled by means of elastic membranes.

25. Device according to claim 17, wherein a further layer comprises a radiation protection means (12) for the first or the second layer or is formed by such a radiation protection means.

26. Device according to claim 25, wherein the further layer is mounted on the first layer or on the second layer so as to be movable or displaceable relative to the first layer or the second layer, preferably by means of a guide, in particular a slotted guide.

27. Device according to claim 23, wherein at least one of the jacket (11) or the radiation protection means is made of a preferably polished and/or shiny metal.

28. Device according to claim 17, wherein the first layer and/or the second layer and/or the further layer comprises a passage, preferably closed by means of a glass or heat protection glass, for sensor signals to and/or from the object (4).

29. Device according to claim 17, wherein an intermediate space through which a specifiable fluid, preferably ambient air (10), can flow is formed between the first layer and the second layer and/or between the second layer and the further layer in order to create a fluid layer.

30. Device according to claim 17, wherein the first layer is coupled to the second layer or the further layer and/or that the second layer is coupled to the further layer via a locally acting connecting means.

31. Device according to claim 16, wherein the device is a strip-shaped or plate-shaped object (4) for use in a hot rolling process.

32. Device according to claim 19, wherein the cooling device is disposed in a connecting piece (7) of the base frame element (9).

33. Device according to claim 21, wherein the fluid is ambient air (10).

34. Device according to claim 25, wherein the radiation protection means (12) is a radiation protection sheet.

35. Device according to claim 27, wherein the polished and/or shiny metal has a low emissivity.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0051] There are various ways to advantageously configure and further develop the teaching of the present invention. For this purpose, reference is made firstly to the subordinate claims and, secondly, to the following explanation of a preferred design example of the device according to the invention on the basis of the drawing. In the context of the explanation of the preferred design example on the basis of the drawing, other generally preferred configurations and further developments of the teaching are discussed as well. In the drawing, the figures show

[0052] FIG. 1 in a side view (A) and in a front view (B) a design example of a device according to the invention for determining the thickness of an object,

[0053] FIG. 2 a cross-section, enlarged, through an upper leg of the device according to FIG. 1,

[0054] FIG. 3 a cross-section, enlarged, through a lower leg of the device according to FIG. 1, and

[0055] FIG. 4 in a side view, sectioned, the device of FIG. 1.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

[0056] FIG. 1 shows a design example of a device 1 according to the invention in a side view (A) and in a front view (B). A C-shaped frame 2 is mounted on a linear axle 3 such that it can be moved in a traversing manner relative to the object 4 to be measured, for example a steel sheet 4. Thus, a measuring track is recorded transversely to the movement direction of the steel sheet 4. The C-shaped frame 2 consists of an upper leg 5 and a lower leg 6, which are connected to one another via a connecting piece 7. At the outer end of each leg 5, 6 there is a respective optical distance sensor 8a, 8b, for example a laser profile sensor. The upper sensor 8a measures against the upper side of the steel strip or the steel sheet 4, the lower sensor 8b measures against the underside of the steel strip or the steel sheet 4. The two measurement values and the known distance between the sensors 8a, 8b can be used to determine the thickness of the steel strip or the steel sheet 4.

[0057] FIG. 2 shows a cross-section through the upper leg 5 of the C-frame 2. The sensor 8a is fastened to an inner base frame element 9. Cooling air 10 flows through the interior of the base frame element 9 and also flows past the sensors 8a, 8b and cools them. The base frame element 9 is surrounded by a jacket 11. Said jacket is disposed at a distance from the base frame element 9; specifically using only a few punctiform fastenings (not shown), so that thermal bridges are ideally avoided. Cooling air 10 also flows between the jacket 11 and the base frame element 9.

[0058] FIG. 3 shows a cross-section through the lower leg 6 of the C-frame 2, whereby the lower leg 6 is additionally provided with a radiation protection sheet 12. This radiation protection sheet 12 is likewise connected to the jacket 11 by means of sporadically disposed spacers 13a, 13b. The spacers 13a, 13b are implemented in a floating manner so that movements of the radiation protection sheet 12 resulting from the different temperature expansion are not transmitted to the jacket 11. The radiation protection sheet 12 is not closed in an airtight manner, so that heating of an air layer 19 between the radiation protection sheet 12 and the jacket 11 is reduced with the aid of the convection.

[0059] FIG. 4 shows a lateral sectional view through the C-frame 2. A cooling register 14 is provided in the connecting piece 7 between the upper leg 5 and the lower leg 6. The cooling register 14 comprises cooling fins 15 for exchanging heat with the cooling air 10. In the cooling register 14, a cooling liquid is used to remove the heat to the outside via a connector 16. An air flow 18a, 18b is produced inside the C-frame 2 with the aid of a fan 17. The air flows from the cooling register 14 inside the base frame element 9 inside the upper leg 5 and the lower leg 6 to the sensors 8a, 8b. From there, the cooling air 10 then flows in the intermediate space between the base frame element 9 and the jacket 11 back to the cooling register 14, where the cooling air 10 releases the absorbed heat again. Thus, a closed cooling circuit is created inside the C-frame 2.

[0060] The design example of the device according to the invention provides a device for determining the thickness of sheet-like or plate-shaped objects 4, in particular for use in hot rolling, which consists of a C-frame 2 having an upper leg 5 and a lower leg 6 and a connecting piece 7, whereby an optical sensor 8a, 8b for determining the thickness is disposed on least on one leg 5, 6. To eliminate temperature effects on the at least one sensor 8a, 8b, the leg 5, 6 of the C-frame 2 carrying the sensor 8a, 8b has a multilayered structure.

[0061] With respect to further advantageous configurations of the device according to the invention, reference is made to the summary of the description and to the attached claims in order to avoid significant repetitions. Certain aspects are, however, reiterated below.

[0062] Essential aspects of design examples of the device according to the invention are summarized illustratively in the following:

[0063] With the present invention, it is possible to realize a multistage cooling concept with a preferably closed cooling circuit. In the case of the example configuration of the frame as a C-shaped frame, the cooling concept initially consists of decoupling the C-shaped frame or connecting frame of the sensors from temperature effects from the environment. This can be achieved with a variety of measures to minimize the effect of the ambient temperature, including the temperature input to the frame structure caused by thermal radiation. In the following, the structure of a design example of a C-frame according to the invention is described from the outside to the inside:

[0064] In a first stage, a radiation protection sheet is applied as the outermost layer, so to speak. It consists of polished/shiny metal, for example a steel or stainless steel having a low emissivity factor as a measure for the directional thermal emissivity. Since, according to Kirchhoff's law, the directional thermal emissivity is equal to the absorptivity, a material having a low emissivity factor or emissivity reflects incident thermal radiation very efficiently.

[0065] The radiation protection sheet is suspended on a jacket. The connection is configured such that different thermal expansion of the materials used is compensated, for example with the aid of a slotted guide.

[0066] In an experimentally installed device, the temperature of the side of the sheet facing away from the target increases by up to 150° C. within less than ten minutes.

[0067] A second stage consists of an air gap between the radiation protection sheet and the underlying jacket. Air has insulating properties and also serves to transport heat. The first radiation protection layer, the radiation protection sheet, is not sealed in an airtight manner, so that, in the second stage, heat is dissipated by convection.

[0068] A third stage consists of the jacket, which is again made of polished/shiny metal, for example a steel or stainless steel with low emissivity.

[0069] This jacket encloses a base frame element or the base C-frame in an almost airtight manner, but is mechanically connected to said base frame element only at the base surface, the intersection with the linear axle, and in the front region of the measuring legs. In the area in which the jacket covers the sensors, the jacket comprises a respective opening so that the light path of the optical sensors is not adversely affected. In order to create an airtight seal, the openings are closed with a heat protection glass. The heat protection glass is transparent to the optical radiation of the sensors, for example laser radiation, but blocks thermal radiation in the infrared spectrum. This makes it possible for the temperature fluctuation on the inside of the jacket or jacket sheet to be only about a quarter of that of the radiation protection sheet.

[0070] A fourth stage again consists of an air gap, here between the jacket and the base frame element. Air circulates inside said air gap in an active and closed cooling circuit.

[0071] A final stage is formed by the actual base C-frame or base frame element. Said frame or frame element comprises the sensor receptacles at the ends of the legs and the cooling register inside the connecting piece. These are both implemented as hollow bodies through which the air of the cooling circuit flows.

[0072] For airflow, the air enclosed inside the jacket circulates with the aid of a fan as follows: From the fan, which is located inside the connecting piece in the base frame element, the air flows via the cooling register through the legs of the base frame element to the sensors. The cooling register comprises a cooling medium and cooling fins that ensure an efficient transfer of heat from the cooling air to the cooling medium. The heat is dissipated from the base frame element to the outside by means of the cooling medium, for example via an external fan. From the sensors, the air flows between the outside of the base frame element and the jacket back to the fan. As a result, there is virtually no temperature fluctuation at the base frame element.

[0073] Therefore, using the abovementioned measures, the high ambient temperature occurring on the outside of the thickness measuring system or the device is very efficiently incrementally reduced to such an extent that moderate temperatures prevail at the base frame element, and thus also at the location of the sensors, which are firstly within the permissible temperature range for the sensors and secondly do not adversely affect the measurement.

[0074] However, the resulting stepped temperature profile in the cross-section of the measuring system or device means, for example, that the radiation protection sheet has a significantly higher temperature than the jacket. Due to the different expansion, this leads to a relative displacement of the radiation protection sheet with respect to the jacket.

[0075] In order to avoid mechanical stresses, the radiation protection sheet and the jacket are connected to one another at only a few points. Said points are configured such that there is no rigid connection. They are instead mounted in a floating manner. This implementation therefore allows for different thermal expansion of the two layers.

[0076] The same applies for the next layer, the jacket, as well. The jacket is divided into a plurality of segments, each of which is connected in an airtight manner to an elastic membrane. The membranes can absorb and compensate the length changes that occur due to temperature expansion. The connecting segments between the upright and the sensor head are likewise mounted in a floating manner in order to minimize fluctuations when forces are introduced into the base frame element.

[0077] As a result of the multistage cooling concept, only minimal cooling capacity is required. The majority of the produced radiant heat is already kept away from the jacket by the radiation protection sheet. The back side of the protection sheets is furthermore cooled by the draft created by the convection.

[0078] Thermal conduction from the jacket into the base frame element is virtually eliminated structurally by reducing the mechanical connections between the jacket and base frame element. In this stage, the jacket is cooled by the air cooling, whereby only a small cooling capacity has to be provided to the jacket because it can heat up (in practice by up to 40° C.) without affecting the thickness measurement. The heat absorption of the base frame element due to the thermal radiation of the jacket is low in this temperature range, because both the radiating and the absorbing surfaces have a low emissivity factor or emissivity.

[0079] The air cooled in the cooling register flows directly in the interior of the base frame element to the sensors, so that both the base frame element and the sensors exhibit virtually no temperature fluctuation during operation.

[0080] As a result of the abovementioned measures, the effect of the ambient conditions on the thickness measurement is largely eliminated.

[0081] The largest remaining disturbance variable is the varying heating within a respective leg (on the side facing the second leg and on the side facing away from the second leg). Due to the length of the legs, differences in the range of a few 1/10° C. are enough to produce significant measurement errors. For this purpose, the temperatures at the relevant locations are measured and the effect on the thickness measurement is determined. During operation, the resulting error can be eliminated almost completely by factoring in a correction value.

[0082] Lastly, it must expressly be noted that the above described design example serves only to explain the claimed teaching, but does not limit said teaching to this design example.