Paper making and fiber liberation – Apparatus – Automatic control
Patent
1991-01-29
1994-03-29
Jones, W. Gary
Paper making and fiber liberation
Apparatus
Automatic control
162263, 162 11, 364471, D21F 106
Patent
active
052981223
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a measuring device and method for measuring the crosswise profile of a paper web.
Up to now it has been customary to move the measuring head along the measuring bridge, crosswise to the paper web, with always the same speed. This results in the measurements always taking place in the same time frame at the individual measurement places.
The goal of measuring is to determine the stable cross section of the web and to make corrections to the accumulation of material accordingly, for example by the required adjustment of the inside width of the headbox gap or slice --and along and crosswise to the direction of running--in order to achieve a desired cross section or transverse profile of the web. Formation of the desired cross section of the web is impaired by interference or disturbances in the material flow from the headbox. These interferences, which may result in deviations from the desired cross section, cannot always be precisely determined. It may happen that the frequency of the interference or disturbance and the frequency of measurement are in a whole number relationship to each other. In this case the measurement result may falsely indicate a deviation from the desired cross section. Therefore, a correction as a result of such a measurement cannot lead to the attainment of the desired cross section or transverse profile of the web.
GB-A-1 218 001 discloses a measuring device for determining average values, for example, for the thickness of a passing web. In this connection the sensing speed is controlled proportionally to the speed of movement of the web. However, this measuring system is not capable of preventing the falsification of the results caused by the matching of the measuring frequency and the interference frequency.
SUMMARY OF THE INVENTION
It is the object of the invention to suggest a device and a method for measuring the cross section of the paper web for the purpose of determining the stable cross section over a considered length of the paper web. This is intended to prevent miscalculations of the cross section and, consequently, inappropriate adjustment actions by means of the control devices affecting the cross section of the paper web.
Now in order to implement these and still further objects of the present invention, which will become more readily apparent at the description proceeds, the measuring device for measuring the crosswise profile or cross-section of a paper web, of the present development is manifested, among other things, by the features that there is provided a stationarily arranged measuring bridge extending in transverse direction of the paper web and beneath or in cooperative relationship with which there is movable the paper web in a predetermined direction of travel. A measuring head is provided for the measuring bridge and is movable back and forth on the measuring bridge in the transverse direction of the paper web at a measuring frequency for determining a measuring value representative of the thickness of the paper web at a predetermined measuring location above which there is momentarily located the measuring head during movement of the measuring head back and forth on the measuring bridge. The measuring bridge has measuring points or spots located along the measuring bridge and at respective locations of the measuring points the measuring head determines respective measuring values representative of the thickness of the paper web at predetermined measuring locations in the transverse direction of the paper web. Further, there are provided means for altering the measuring frequency of the measuring head which comprise process management means provided with traversing flow program means for selectively changing at lest any one of (i) a traversing time of the measuring head in the transverse direction of the paper web and (ii) a waiting time of the measuring head between two transverse passes of the measuring head in the transverse direction of the paper web. As a result, determination of the mea
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Munch Rudolf
Weisshuhn Elmer
Jones W. Gary
Lamb Brenda A.
Sulzer Escher Wyss
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