Optics: measuring and testing – By monitoring of webs or thread
Reexamination Certificate
2000-03-24
2002-12-24
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By monitoring of webs or thread
Reexamination Certificate
active
06498646
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. § 119 of German Patent Application No. 199 13 929.6, filed on Mar. 26, 1999, 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 relates to a device for determining the properties of a material web, e.g., a paper web, having at least one radiation source and at least one identification device for radiation that is emitted by the radiation source and that penetrates the material web and/or is reflected by the material web.
2. Discussion of Background Information
Devices of the type generally disclosed above are known, e.g., from U.S. Pat. No. 5,233,195, which describes the use of a &bgr;-emitter and an X ray source, as well as an ionization chamber as a detection device. Known from U.S. Pat. No. 5,010,766 is a plate divided into four sections, which is provided on one side of a moving web that is being examined. The plate interacts with a configuration of four eddy current sensors on the other side of the web. In the article (ISBN 952-5183-09-2) “Paper Machine Applications with Fullsheet Imaging Measurement” by Shih-Chin Chen et al., pages 330-337,
Control Systems '
98, “
Information Tools to Match the Evolving Operator Role,
” Sep. 1-3, 1998, Porvoo, Finland, a configuration comprising a light source, CCD cameras, and high speed processors is mentioned, where the light from the light source transmitted by a moving web is detected by CCD cameras.
SUMMARY OF THE INVENTION
The present invention provides an apparatus and a process which permit examination of a material web with a high degree of accuracy, particularly with respect to a number of different properties of the material web.
According to an exemplary embodiment of the invention, the detection device includes at least one detection area that is divided in non-uniform fashion into a large number of individual sensors.
The division of the detection area of the detection device permits examination of the material web that is both locally and temporally differentiated, because part of the radiation that strikes one of the individual sensors is characteristic of an area of the material web that was either penetrated or reflected by the given radiation. With a rapid read-out of the individual sensors belonging to the detection device, momentary pictures of the material web with respect to the properties under examination can be prepared in rapid sequence which, in principle, permits a seamless examination of the material web. The local resolution achievable with the invention is limited only by the size of the individual sensors. In principle, therefore, any desired level can be selected.
The non-uniform division of the detection area provided by the invention allows for an advantageous adjustment of the detection device to the conditions characteristic of the given measurement. In a particular embodiment, the movement of the material web relative to the detection device can be taken into account by the length of the individual detection areas of at least several of the individual sensors in the travel direction of the material web exceeding the length extending in the direction cross-wise thereto. In general, the individual sensors forming the detection area can differ with respect to the size and/or the shape of their individual detection areas.
According to another exemplary embodiment of the invention, it is also possible to vary the number of individual sensors per surface unit over the detection area. For example, it can be arranged in such a way that the number of individual sensors per surface unit in a central zone of the detection area is greater than in at least one marginal zone of the detection area. An optimal relation can be achieved thereby between the signal
oise ratio and the total number of sensors.
In another particular embodiment of the invention, the individual sensors can be microprocessors which, e.g., have individual detection areas of less than approximately 1 cm
2
, preferably of about 1 mm
2
.
In another embodiment of the invention, a 10×10 (or 100 total) array of microsensors, each with a square detection area of approximately 1 mm
2
, can be positioned in checkerboard pattern. In this manner, the microsensors can form a continuous, square detection zone that may be positioned in a center of a detection area. The detection area can also include marginal zones formed, e.g., of oblong, particularly rectangular, microsensors having individual detection areas of several mm
2
and having longitudinal axes oriented in the web travel direction.
It is noted that it is fundamentally possible to utilize any desired geometric arrangement of the individual sensors. For example, the detection areas, at least in certain zones, can be provided in the form of concentrically positioned, ring-shaped individual sensors. Further, the given detection zone, or the entire detection area, can be, e.g., rectangular, circular, or triangular.
Furthermore, the detection area according to the invention can include a plurality of detection zones formed of individual sensors which are, e.g., staggered or offset relative to one another or which can be movably positioned.
In another embodiment of the invention, the microsensors can be semiconductor detectors, e.g., semiconductor sensors of very pure silicon manufactured especially for detecting electromagnetic radiation or electrically charged particles. In principle, it is also possible to use other radiation detectors, e.g., ionization detectors (such as ionization chambers) or scintillation detectors (such as scintillation tubes).
In principle, the device according to the invention can be provided with an approximately point-like radiation source that emits radiation in a specific solid-angular area. The radiation emitted by a point radiation source can also be widened by additional devices to permit planar radiation of the material web. It may be preferable for the radiation source to be designed in such a way that a radiation surface is provided. Further, the shape of the radiation area of the radiation source may preferably correspond to that of the detection area of the detection device.
It is also possible to provide a plurality of individual radiation sources instead of a single radiation source and to arrange those sources in the form of a source array.
It may be preferable for the radiation source, in keeping with the above-noted features of the invention, to be designed to provide a substantially homogeneous or uniform distribution of radiation intensity when no material is located in the radiation path.
The radiation source can be designed to release radiation with a constant intensity over time or with an intensity that is preferably varied in regular fashion, specifically a pulsing intensity. The radiation used can be of an electromagnetic type, particularly that provided by microwaves, LED light, laser beams, or X rays. In cases in which pulsed radiation is used, LEDs or lasers are the preferred radiation source. The given radiation source can be designed so as to permit adjustment of the wavelength of the electromagnetic radiation. It is also possible to use radiation sources with different wavelengths simultaneously. In principle, it is also possible to combine sources using different types of radiation.
In another possible embodiment of the invention, the radiation source is designed to radiate electrically charged particles and is particularly designed as an &agr;-emitter and/or a &bgr;-emitter.
During operation of the device according to the invention, it may be preferable to position the radiation source on one side of the material web and the detection device on the other side, so that radiation penetrating the material web will be recorded. In principle, it is also possible to position the radiation source and the detection device on the same side of the material web and to detect the radiation reflected from the material web. Moreover, tra
Griech Wolfgang
Typpo Pekka M.
Font Frank G.
Nguyen Tu T.
Voith Sulzer Papiertechnik Patent GmbH
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