Paper making and fiber liberation – Processes and products – Utilizing electrical or wave energy
Reexamination Certificate
1999-05-12
2001-05-29
Nguyen, Dean T. (Department: 1731)
Paper making and fiber liberation
Processes and products
Utilizing electrical or wave energy
C162S198000, C162S262000, C162S263000, C162SDIG004, C250S308000
Reexamination Certificate
active
06238522
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to paper-making machines and, more particularly, to the measurement of web thickness in a paper-making machine.
2. Description of the Related Art
The problems associated with the production of a web of a fiber material such as paper having a consistent thickness (or consistency or height) along the machine-direction (MD) and the cross-direction (CD) thereof, are well known in the art. Various production factors affect web thickness. Most if not all of the various production factors are controllable given relevant and accurate information about the web at a point or points along its production path. Maintaining a consistent profile is essential for the final product.
Also, it is necessary to determine that the web maintains a consistent profile. While there are seemingly many locations to determine the profile of the web, the type of system for making that determination generally dictates where the profiling system must be placed. In some cases more that one position along the web is necessary. It is known to perform weight profiling on the web (paper) in order to determine MD and CD consistency where this information is used to provide some control of the production variables. This category includes visual monitoring of the dry line, and use of ultrasonics at the wet end for determining wet sheet thickness in the MD sense. Devices as described above are generally located under the sensors that obtain MD and CD data for consistency determination at the wet end of a paper-making machine.
What is needed in the art is a wet end or dry end thickness consistency measurement apparatus and/or method.
SUMMARY OF THE INVENTION
The present invention is a method and apparatus for providing thickness measurement of a web of paper in a paper-making machine.
In one form, the present invention is an apparatus for determining the machine-direction (MD) and/or cross-direction (CD) thickness of a web of paper in a paper-making machine, the paper-making machine comprising at least one roll and a wire or felt adapted to support a web of paper. A gamma transceiver comprising a gamma radiation source and gamma radiation detector is positioned adjacent one side of the web of paper. Gamma radiation backscattered by the web of paper is detected and processed to provide a thickness measurement.
The gamma transceiver may be comprised of a plurality of gamma transceiver modules provided in a line or array depending on the desired profile of gamma radiation backscatter. The information may be processed by a processor/controller to determine a thickness profile. Such information may be used to adjust or control front end production parameters.
In another form, several gamma transceivers may be utilized at various points along the paper production path to provide thickness profiling of the paper at various stages of production or within a particular section of the paper-making machine.
In yet another form, the present invention provides a method for determining a thickness of a web of paper in a paper-making machine, the paper-making machine comprising at least one roll and a wire or felt adapted to support a web of paper. The method includes providing a gamma radiator proximate one side of the web and receiving backscattered gamma radiation with a gamma radiation detector. Signals representing the gamma radiation backscattered by the web of paper are processed to provide a thickness measurement.
REFERENCES:
patent: 3881987 (1975-05-01), Benz
patent: 4239591 (1980-12-01), Blake
patent: 5258622 (1993-11-01), Pratt, Jr.
patent: 5331163 (1994-07-01), Leahy et al.
Nguyen Dean T.
Taylor & Aust P.C.
Voith Sulzer Paper Technology North America Inc.
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