Paper making and fiber liberation – Processes and products – With measuring – inspecting and/or testing
Reexamination Certificate
2000-03-20
2004-06-01
Griffin, Steven P. (Department: 1731)
Paper making and fiber liberation
Processes and products
With measuring, inspecting and/or testing
C162S263000, C162SDIG006, C250S339020, C250S339110, C250S559040, C250S559050, C250S559110, C356S429000
Reexamination Certificate
active
06743337
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. § 119 of German Patent Application No. 199 12 500.7, filed on Mar. 19, 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 process and apparatus for determining properties of a traveling material web, e.g., a paper web in a paper machine.
2. Discussion of Background Information
When manufacturing webs, for example, paper webs, an effort is made to obtain the greatest possible amount of information about the material web being created, in order to have the option of intervening deliberately in the manufacturing process.
It is known to take spectroscopic measurements using electromagnetic radiation in the IR range on a paper web in a paper machine to determine parameters which are relevant for the process from the interaction of the IR radiation with the paper web information. To do so, traversing measurement heads, i.e., running crosswise (transverse) to a web travel direction, are used which operate with multiple discrete wavelengths in order to inspect the paper web, e.g., with regard to moisture, basis weight, opacity, or content.
The problem with such traversing systems is the high production speed in modem manufacturing machines which, in the case of paper machines can be, e.g., on the order of 2,000 m/min. With the known traversing measurement systems, it is impossible at such high process speeds to obtain cross-direction profiles or so-called “time-shifted cross profiles,” because the distribution of the respective pertinent parameters across the width of the material web cannot be determined or can be determined only with insufficient accuracy. Furthermore, the large dimensions of traversing systems are a disadvantage because they can only be used at very few locations of the machine, for example, only at the end of a paper machine.
It is also known to evaluate continuous IR spectra using different mathematical processes, in which the measurements are taken at only one location and are frequently taken with complex, expensive instruments, such as FTIR spectrometers.
Known devices and/or processes are described, e.g., in U.S. Pat. No. 4,098,641, EP-0 137 696, WO 98/36264, WO 95/08019, WO 93/15389, and WO 95/31709, the disclosures of which are expressly incorporated by reference herein in their entireties.
SUMMARY OF THE INVENTION
The present invention provides the simplest and least expensive capability for determining the properties of a traveling material web which, in particular, allows quick cross-direction profiles to be determined at selected places on the material web.
The present invention includes a plurality of measuring points on the material web that are simultaneously illuminated and imaged through at least one optical device on one detection surface divided into multiple individual detection surfaces of at least one detector.
According to the invention, multiple areas of the material web can be simultaneously inspected without contact. The division of the detection surfaces of the detector makes it possible to process or evaluate the signals generated by the imaging of the measuring points on the detection surface of the detector separately at first by measuring point and subsequently to combine them into an overall image of the material web. According to the invention, for each measurement, a partial area of the material web containing the measuring points is imaged on the detection surface of the detector. Therefore, a snapshot of the material web is obtained with each measurement. Because measurements are taken simultaneously at all measuring points according to the invention, the result can be used for a quick control and/or adjustment of the manufacturing process immediately after the measurement. In combination with sufficiently rapid processing devices, it is therefore possible to achieve continuous process monitoring with the capability of immediate correction. A quick adjustment prevents or minimizes the production of rejects and results in fewer quality fluctuations. Moreover, the quick intervention allowed by the process according to the invention can be particularly advantageous in the case of material changes or generally when changing over to another product.
According to the invention, the material webs can fundamentally be inspected with regard to every property by which the interaction of electromagnetic radiation with the material web is influenced. In manufacturing paper, e.g., the moisture content or moisture, basis weight, opacity, fiber orientation, thickness, surface properties, type and/or distribution of contents, etc., are parameters with regard to which an inspection of the paper web that is being produced or the finished product is of interest. The capability of inspecting in rapid succession each of several areas of the material web simultaneously, makes it possible, e.g., to measure the moisture of the paper web immediately after the press part of a paper machine, in order to adjust a vapor bubble box of the dry part on the basis of the measurement results.
Of course, the present invention is not limited to paper machines or to specified positions in a machine. Instead, properties of other material webs, e.g., any chosen fiber material webs, including cardboard webs as well as textile webs, which are of interest can be determined at any chosen position of the manufacturing machine.
When, according to an exemplary embodiment of the invention, the measuring points are located along a substantially straight line, it becomes possible for the material web to be line scanned using the detector and/or the optical device. In this regard, the material web can be illuminated in such a way that the straight line formed by the measuring points extends at least substantially cross-wise (or perpendicularly) to the web travel direction (i.e., the measuring points are substantially illuminated through the optical fibers). In this way, current cross-direction profiles of the material web can be obtained, in order to determine the distribution of the parameters across the width of the material web.
The use of electromagnetic radiation in the IR range to illuminate the measuring points according to another exemplary embodiment of the invention makes it possible to operate IR spectroscopy at the measuring points. This radiation is particularly appropriate for determining the moisture of paper webs. For example, radiation in the range of approximately 0.1 &mgr;m to 40 &mgr;m can be used. A preferred wavelength range is in the near-IR range and includes, e.g., wavelengths between approximately 1.0 &mgr;m and 2.5 &mgr;m.
The material web can be illuminated using appropriate sources of IR radiation in order to take reflection measurements at the illuminated measuring points, with the measurements preferably taken in diffuse reflection. It is also possible to transilluminate the material web with IR radiation and to take transmission measurements by detecting on the detector any radiation that penetrates through the material web at the respective measuring points.
According to another exemplary embodiment of the invention, each measuring point can be imaged using an optical fiber.
Using optical fibers, the radiation originating from the measuring points can be guided to any chosen place, particularly one that is spatially separated from the material web. Thus, the space required for the invention at the material web can be minimized. The process according to the invention can therefore be carried out even when space is limited and consequently, in principle, can be used at any position on a machine for manufacturing the material web. Consequently, the space available for the detector or the devices adjacent to the detector is not limited. Therefore, the invention also makes it possible to take measurements, e.g., immediately after the servo components of the machine which are used to influence manufacturing. In that way, the cont
Greenblum & Bernstein P.L.C.
Griffin Steven P.
Hug Eric
Voith Sulzer Papiertechnik Patent GmbH
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