Data processing: measuring – calibrating – or testing – Measurement system – Dimensional determination
Reexamination Certificate
1999-07-13
2003-02-25
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Dimensional determination
C702S040000, C702S172000
Reexamination Certificate
active
06526369
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 198 31 612.7 filed on Jul. 14, 1998, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a measurement system and process for measuring the cross-direction profile of specific properties of a material web, e.g., a paper or cardboard web, in a paper and/or cardboard machine or in a coating machine.
2. Discussion of Background Information
Measurement systems which are similar in general to above-described measurement systems and commonly known operate on the basis of IR-, &agr;-, &bgr;-, and &ggr;-rays with traversing measurement arrangements. Further, as disclosed in “Wochenblatt für Papierfabrikation [Paper Fabrication Weekly]”, Vol. 11/12, p. 609 and 611 (1998), non-traversing measurement devices which are designed for spectroscopic measurement immediately downstream from the headbox of a paper machine are also known.
Among other disadvantages, the known measurement systems require measurements to be taken mainly in long, free stretches of the material web. In conventional traversing measurement systems, a pure cross-directional profile measurement is virtually excluded since the traversing movement entails a sort of zigzag scanning. Measurement is normally possible only in the wire section and at the end of a respective paper machine, however, excessively long operating cycles tend to result due to the large number of final control elements lying between, which causes relatively imprecise control.
The use of CCD cameras for measuring surface weight is already known. It is true that these devices can detect the entire paper surface produced. However, the expensive image processing is particularly disadvantageous.
Measurement devices for measuring conductivity of the material on the wire in the wet section are also known. While these measurement devices can be arranged relatively near the headbox control elements in question, a disadvantage is that conductivity is a measure of moisture and not of surface weight. Thus, for example, an application for coaters is excluded.
SUMMARY OF THE INVENTION
The present invention creates an improved measurement system of the type generally discussed above which eliminates the above-noted disadvantages, and which ensures shorter control times and more accurate control.
Thus, the apparatus of the present invention includes at least one stationary cross-direction profile measurement device that includes at least one radiation (illumination) source positioned to irradiate (illuminate) the material web in a plurality of defined different wavelength ranges and at least one sensor positioned to measure the intensity of radiation which has been affected by the material web. The apparatus also includes at least one measurement and/or evaluation electronic system. The at least one sensor is adapted to measure only one of the plurality of defined different wavelength ranges of the radiation at a time.
Based on the design according to the present invention, a more accurate measurement of the cross-direction profile of specific properties is possible while reducing space requirements and increasing economy. Moreover, it is possible to take measurements at relatively inaccessible points, e.g., areas of closed travel, in which the material web is supported, e.g., by a roll, a belt, a sieve, and/or a felt. In this regard, radiation reflected by the material web or a coating on the material web can be detected by at least one sensor. Additionally or alternatively, radiation which has passed through the material web or a coating on the material web can be detected by at least one sensor. The detection of reflected radiation from the material web or a coating on the material web advantageously requires less space.
According to an exemplary embodiment of the present invention, at least two stationary cross-direction profile measurement devices can be spaced in a web travel direction of travel. Advantageously, these spaced apart at least two stationary cross-direction profile measurement devices can be associated with at least one unit of a web production machine, e.g., a press section, a dryer section, and/or of a coating machine. The web production machine may produce, e.g., paper webs and/or cardboard webs.
In particular, the present invention can be utilized to reduce control times. For example, it can be advantageous to position at least one stationary cross-direction profile measurement device immediately before and/or immediately after at least one actuator or control element, which is provided to control the respective cross-direction profile.
Based upon the design according to the present invention, it may be possible to provide at least one stationary cross-direction profile measurement device in at least the press section and/or dry section of a paper and/or cardboard machine.
Alternatively or additionally, at least one stationary cross-direction profile measurement device may be provided in at least the wire section and/or at the end of a paper and/or cardboard machine.
A filter device or element may be provided to filter out specific disturbance variables and/or the influence of at least one actuator or control element on the respective cross-direction profile. For example, exponential filters or moving average filters can be utilized. Moreover, more sophisticated filters, such as Kalman filters, may also be utilized.
In order to reduce the space requirement and increase the economy of operation, it may be expedient to connect the radiation source and/or the sensor to at least one light guide.
Moreover, the at least one stationary cross-direction profile measurement device can be designed for operation in the near infrared range (NIR).
At least one stationary cross-direction profile measurement can be designed, e.g., for quantitative detection of surface weight, moisture, thickness, specific ingredients, and/or other properties of the material web.
In particular, for measuring in regions of a free web stretch, a respective stationary cross-direction profile measurement can be provided with at least one optical radiation source to irradiate the material web and can include at least one photodetector to measure the intensity of the optical radiation affected by the material web.
If the material web is irradiated via a plurality of radiation sources of different wavelength ranges, the material web can be irradiated, e.g., by the individual different radiation sources and/or by different chronologically consecutive combinations of radiation sources.
In another advantageous embodiment of the measurement system according to the present invention, at least one stationary cross-direction profile measurement device may be provided with a plurality of sensors of different spectral sensitivity. In this manner, the respective stationary cross-direction profile measurement device preferably includes only one radiation source to irradiate the material web.
In principle, it is possible to provide at least one sensor/filter unit having a spectral sensitivity and/or permeability that is adjustable.
In an exemplary embodiment, at least one light-emitting diode may be provided as a radiation source, which can be particularly advantageous in view of the longevity of service as well as the low cost of such components. Thus, a long-standing prejudice, i.e., that such light-emitting diodes are allegedly not suitable for this purpose, is also overcome by the present invention.
In a wavelength range from 1300 to 2400 nm, there can be relatively strong peaks in the absorption spectrum, e.g., approximately 1450 nm water-overtone, approximately 1930 nm water, approximately 2100 nm cellulose fiber, approximately 2010 nm clay, approximately 2300 nm latex and lignin, approximately 2300-2400 nm polyethylene and other plastics, for which light-emitting diodes are not currently available or are too expensive. Accordingly,
Meinecke Albrecht
Münch Rudolf
Barbee Manuel L.
Greenblum & Bernstein P.L.C.
Voith Sulzer Papiertechnik Patent GmbH
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