Method and equipment in the measurement of the flatness of the flow surface of the headbox of a paper machine

1. A method in the measurement of the flatness of a flow surface of a headbox of a paper machine, in which, according to the method, the flatness of the flow surface is determined by placing a measuring tool on the flat surface formed by the flow surface at several different points in the transverse direction and measuring the position of the measuring tool at each point, the method comprising the steps of:

arranging a measuring sensor at at least two points in the longitudinal direction of the measuring tool, in order to determine the distance between the measuring tool and the flat surface at the points at which the measuring tool is placed, said measuring tool being set for a period of time at one of said points in the transverse direction of the headbox and after said period of time the measuring tool being moved in the transverse direction of the headbox to another of said points in the transverse direction of the headbox;

reading relative dimensions provided by the measuring sensors at each said point in the transverse direction of the headbox, and

combining the position of the measuring tool and the dimensions from the measuring sensors, in order to determine the absolute values of the measured points;

arranging an angle sensor in connection with the measuring tool; and

determining the longitudinal alignment of the measuring tool by means of said angle sensor.

2. A method according to claim 1 , characterized in that the flatness is measured from the lower lip belonging to the headbox, which forms the said flow surface of the headbox.

3. A method according to claim 1 , characterized in that, in the measurement of each transverse point, the longitudinal alignment of the measuring tool relative to the headbox is also measured.

4. A method according to claim 1 , characterized in that, in the measurement, electro-optical devices are used, and are connected to a computer, in order to process and record the measurement results and to form a three-dimensional model depicting the profile of the flat surface.

5. A method according to claim 1 , characterized in that the position of the measuring tool at different transverse points is determined relatively over the entire width of the headbox, after which the measurement is fixed to the headbox, in order to determine the absolute values of the measured points.

6. Equipment in the measurement of the flatness of a flow surface of a headbox in a paper machine, the equipment comprising:

a measuring tool, which is arranged to be set at several different points on the flat surface formed by the flow surface;

a measuring device for measuring the position of the measuring tool at each of said several different points;

means for recording the measurement results;

the measuring tool including a measuring sensor at at least two different points in the longitudinal direction of the measuring tool for measuring the distance between the measuring tool and the flat surface at the several different points at which the measuring tool is set;

means are arranged for combining relative dimensions provided by the measuring sensors and the position of the measuring tool, in order to determine the absolute values of the measured points; and

an angle sensor arranged in connection with the measuring tool, for determining the longitudinal alignment of the measuring tool.

7. Equipment according to claim 6 , characterized in that the measuring tool includes a rigid beam, to which three feet are fitted, of which one foot is arranged at one end of the beam, to be installed at the front edge of the lower lip forming the flow surface.

8. Equipment according to claim 6 , characterized in that there are 4-14, measuring sensors, each of which is a separate differential transformer.

9. Equipment according to claim 6 , characterized in that the measuring device is a laser, preferably a semiconductor laser equipped with distance measurement.

10. Equipment according to claim 9 , characterized in that for the laser the equipment includes a photosensitive reference sensor, which is arranged to be fitted at the opposite end of the headbox to the laser, for determining a base level.

11. Equipment according to claim 10 , characterized in that for the laser there is a photosensitive sensor in the measuring tool, the sensor window of which is arranged at the base level, in order to measure the deviation of the measuring tool relative to the base level.

12. Equipment according to claim 10 , characterized in that the laser and the reference sensor are arranged to be set in front of the front edge of the lower lip forming the flow surface, in order to set the base level outside of the headbox.

13. Equipment according to claim 6 , characterized in that the equipment includes a digital camera, which is arranged to be set in front of the lower lip forming the flow surface, for imaging it from in front.

14. Equipment according to claim 13 , characterized in that the digital camera includes a base equipped with rolling elements for moving the digital camera over the flat surface of the lower lip during imaging and thus for determining the profile of the front edge of the lower lip.