Data processing: measuring – calibrating – or testing – Measurement system
Reexamination Certificate
2000-05-25
2002-11-12
Hilten, John S. (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
C702S172000
Reexamination Certificate
active
06480802
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for determining the flatness of a material strip, as well as to a device for performing the method.
2. Background Information
Undesired unevennesses extending in travel in the longitudinal direction, as well as in the transverse direction thereto are formed in a metal sheet produced in the form of a material strip during the cold and hot rolling of metal sheets. These unevennesses cause the material strip to be deflected to various extents perpendicular to the surface, thus spoiling the flatness, and leading to different strip elongations for several longitudinal portions of the material strip which are disposed transverse to the longitudinal direction. It is therefore necessary during the rolling of a metal sheet to monitor the flatness of the produced material strip and, if deviations from flatness are detected, to influence the conditions of the rolling process.
The value of strip elongation is measured in “I” units, where one I units means a relative length change of 10
−5
, which corresponds, for example, to 10 &mgr;m per meter.
Several methods for measuring flatness are known.
A first method comprises scanning the surface of the material strip by means of a pulsed laser beam, with which a grid of points and their associated distance from the laser light source is recorded. The results are used to determine the deflection of the material strip and thus the flatness.
In a second method, a geometric pattern such as a striated pattern is projected onto the surface by means of an optical imaging device. This pattern is monitored by a camera. Surface deflections distort the pattern, and the magnitude of the distortion provides a measure of the flatness.
The two methods described in the foregoing work on contactless principles, and so they are used preferably in the hot-rolling process. The ambient conditions, however, necessitate frequent maintenance of the optical components, especially during hot rolling. In both methods, moreover, a measuring device must be set-up in addition to the devices normally used for measurement of strip thickness profiles. These devices usually operate with high-energy electromagnetic radiation.
A third method uses a plurality of pressure sensors, which are disposed side-by side, roll along with the material strip and are in contact with the material strip. Different deflections lead to different pressures, and so the measured pressures can be evaluated as a measure of flatness. The disadvantage of this method lies in the mechanical contact of the individual pressure sensors with the material strip, and so, especially in the case of the hot-rolling process, the method cannot be used because of the high temperatures. Even in cold rolling, however, the method suffers from the disadvantage that the mechanical contact leads to wear.
Finally, methods and devices are known that use high-energy electromagnetic radiation such as X-rays or gamma rays to measure strip thickness transverse profiles, as well as the strip contour, or in other words, the shape and position of the material strip over the width. Using this measuring method, however, it has not yet been possible to determine the flatness of the material strip.
SUMMARY OF THE INVENTION
It is emphasized that unevennesses which can also be measured by means of the method describe hereinafter can occur not only in material strip produced from metal sheets, but also in material strips from other materials. Thus the term material strip, rather than metal strip is used in general hereinafter.
The technical problem underlying the present invention is to specify a method and a device for determining the flatness of a material strip, in which device and method the strip elongation is calculated from the values of strip contour.
The present invention thus concerns a method for determining the flatness of a material strip, the material strip predefining a longitudinal direction, comprising:
recording measured values at a plurality of measurement points by at least two radiation sources and a plurality of detectors, the measurement points being disposed transverse to the material of the strip and being sensed by at least two detectors, each of which detects radiation at various solid angles,
moving the material strip in the longitudinal direction relative to the radiation sources and the detectors, and rows of measured values substantially encompassing all measurement points are recorded at each of several given intervals,
calculating the slope of the material strip for each recorded measurement point from the measured values of the detector pairs,
calculating the wavelength and phase of slope changes for successive rows of measured values at a known relative velocity in the longitudinal direction,
calculating at least one extremum and the respective associated closest row of extreme measured values from the wavelength and phase,
calculating the transverse contour by summing the slope values of the rows of extreme measured values, and then determining the amplitude of the transverse contour, and
calculating the strip elongation from the wavelength and amplitude of the contour.
The present invention also relates to a device for determining the flatness of a material strip, the material strip predefining a longitudinal direction, comprising:
at least two radiation sources, which are disposed transverse to the longitudinal direction and spaced apart from each other;
a plurality of detectors, which are disposed transverse to the longitudinal direction at a distance from each other and from the radiation source, the material strip being disposed between the radiation sources and the detectors, each of at least two detectors being oriented towards two different radiation sources and forming a detector pair or pairs, and axes formed respectively by a detector together with a radiation source intersecting each other substantially in the region of the material strip and thus predefining measurement points; and
means for evaluation of measured values which are recorded by the detectors, the evaluation means calculate from the measured values the slope of the material strip at the measurement points and therefrom the flatness of the material strip.
The technical problem described in the foregoing is solved by the method according to the present invention, wherein measured values are first recorded at a plurality of measurement points by means of at least two radiation sources and a plurality of detectors. The said measurement points are disposed such that they lie transverse to the longitudinal direction and spaced apart from each other in the material of the strip.
The measurement points are sensed individually by at least two detectors, each of which detects radiation at various solid angles. At any time, therefore, one detector is oriented towards one of the at least two radiation sources and the other detector is oriented towards the other radiation source. Thus those volume elements of the material strip through which there passes the radiation sensed by the detectors can be regarded as the measurement points.
Furthermore, the material strip is moved in the longitudinal direction relative to the radiation sources and the detectors. Rows of measured values substantially encompassing all measurement points are recorded at each of several given intervals. The slope of the material strip is then calculated for each recorded measurement point from the measured values of the detector pairs. Thus there is obtained a grid of measured values and associated slope values extending over a given region of the material strip.
Knowing the velocity of the material strip in the longitudinal direction relative to the radiation sources and detectors, it is then possible to calculate, for successive rows of measured values, the wavelength and phase of the slope changes, which changes characterize the flatness. In this context, the wavelength is to be understood as the distance between each of two successive regions with the same deflec
Frishauf Holtz Goodman & Chick P.C.
Hilten John S.
IMS Messsysteme GmbH
Washburn Douglas N
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