The present invention relates to an arrangement for determining blade pressure, which includes

- a doctor apparatus equipped with a doctor blade with a work edge, for doctoring or coating a surface,

- measuring means, which include one or more analysis members reacting to loading, that is arranged between the work edge of the doctor blade and the surface for determining the blade pressure.

In addition, the invention also relates to an apparatus and a method for determining blade pressure. The even distribution of the doctoring force over the entire length of the blade is important, so that the best possible result will be achieved with doctoring. For example, if the web breaks, the possibility of a drop-through will be reduced, if the doctor loads the surface being doctored over the entire length of the blade. It will also be possible to manage blade wear better, if the loading is even.

For the aforementioned reasons, from time to time it is necessary to adjust the loading force of the doctor, more generally the blade pressure against the surface being doctored. The solutions in use for determining the loading force required are based on ready-made graphs, in which a computational loading force is given. However, the graphs do not take into account, for example, possible reductions in loading due to the ageing of the blade or doctor apparatus.

Using known solutions, it is not possible to measure the evenness of the loading, while the loading force is based solely on computation. Therefore, the real situation remains a guess and, for example, two doctoring positions cannot be reliably compared. Many practical problems are associated with doctoring, in order to resolve which it would be important to be able to determine the true loading profile and force.

However, at present no apparatus exists that works in practice for the reliable on-site measurement of the doctoring profile and force, by means of which measurement could be performed as easily as possible. Some solutions are known from prior art, which have been developed for measuring the doctoring profile, and which are based on measurement set over the main length of the entire blade. However, associated with these is the significant problem that space around the blade is very limited and that the accessibility of the blade over its entire length is very poor . Publication EP1244850 discloses a so-called smart doctor, in which, in addition to the angle of the doctor blade, the blade pressure too can be determined indirectly. The term blade pressure refers to the pressure or force directed by the doctor blade to the surface. In the prior art, the question is pre- cisely of indirect determining, as the analysis member is located on some structure of the doctor. Thus, the determining of the blade pressure is mainly based on computation, and is thus imprecise. In addition, the smart doctor is expensive to purchase and operate. Finnish utility model register number 8431 discloses another measuring device that can be attached to the structure of a doctor or to a doctor blade.

A solution is known from Finnish patent 119525 B, in which an analysis member reacting to loading is arranged between the work edge of a doctor blade and the surface being doctored when determining the blade pressure. In this case, the analysis member is attached to the surface being doctored and it is formed by, for example, an elongated self-copying paper band, or a group of electronic sensors arranged on the surface. It is difficult to attach the band or sensor arrangement to the surface, which is several metres, or even more than ten-metres long. In addition, once measurement has ended, the band or sensors must be removed from the surface. In addition, the solution can only be used to measure a relatively narrow area of pressure.

The present invention is intended to create an arrangement, apparatus, and method for determining blade pressure, which is easy to implement, and by means of which blade pressure can be determined more easily and precisely than previously. The characterizing features of the arrangement according to the invention are stated in Claim 1, those of the apparatus in Claim 4, and those of the method in Claim 11.

In the invention, the analysis member is fitted to the work edge of the doctor blade, where it can be moved in the longitudinal direction of the doctor blade. Thus, in the invention, the entire relatively long blade is not measured all at one time, instead a narrow area of the entire length the blade is seen at one time. The invention allows most of the blade length to be progressively read, i.e. 'scanned' when measuring the blade pressure and thus the local blade pressure can be more easily determined. Thus, the determined blade pressure corresponds accurately to reality and local variations in blade pressure can be clearly seen.

According to one embodiment, measurement can be performed in a set manner continuously, so that the entire desired blade length will be measured progressively. According to a second embodiment, the analysis member can even be stopped at a de- sired point in the longitudinal direction of the blade and the blade loading then changed. In that case, the effect of the loading on the blade pressure at the point in question will be accurately determined. Through the invention, the blade pressure can be determined independently of the doctor-apparatus structure easily and simply from different types of doctor apparatus. A single type of analysis member can then be used in connection with all doctor apparatuses. In addition, it will be unnecessary to dismantle or alter the doctor apparatus. There is no need to arrange permanent measuring devices for the measurement on the blade or the surface being doctored, so that the actual measurement can be started quickly. The actual measuring of the blade pressure takes only a few minutes. In the same way, after measuring there is no need to separately remove measuring elements from the blade or the surface being doctored, so that production can be started rapidly. The other additional advantages achieved by means of the invention are stated in the description portion and the characteristic features in the Claims .

The invention, which is not restricted to the embodiment described in the following, is described in greater detail with reference to the accompanying figures, in which Figure 1 shows a doctor apparatus on the side of a web-forming machine,

Figure 2 shows a more detailed side view of the arrangement in connection with the blade of the doctor apparatus,

Figures 3a and 3b show side and end views of the apparatus, Figure 4 shows an axial view of the arrangement, in connection with several surfaces,

Figure 5 shows a flow diagram of a first embodiment of the method, and

Figure 6 shows a flow diagram of a second embodiment of the method.

Figure 1 shows a doctor apparatus 10 that is, as such, conventional, which in this case includes two consecutive doctors 11. Each doctor 11 is equipped with a doctor blade 12 for doctoring a surface 13. The doctor 11 includes blade holders 17, in which there are loading hoses 18 for loading the doctor blade 12 against the surface. In Figure 1, the doctor blade 12 is used to doctor the surface 13 of a roll 14, in order to keep it clean. Alternatively, the doctor blade can be used to even coating paste on the surface of the roll when coating the web, or the blade can be a creping blade (not shown) .

In terms of the operation of the doctoring apparatus, it is important to know the blade pressure, as well as possible variations in the blade pressure in different parts of the blade 12. Too low a blade pressure will weaken the doctoring result. On the other hand, too high a blade pressure can damage the surface while simultaneously accelerating wear of the doctor blade. An uneven blade pressure will also affect the doctoring result and, in addition, cause uneven wear in the doctor blade 12. Particularly in coating, an even blade pressure is important in terms of the coating result.

During the determining of the blade pressure, the roll 14 is stationary and thus does not rotate. The solution according to the invention can be used not only for measuring the loading of a stationary roll 14, but also for measuring a rotating roll 14. Figure 1 shows a special case of a doctoring apparatus 10, a so-called double doctor. It is obvious that the invention can be applied equally with a single-blade doctor.

Figure 2 shows in greater detail one schematic example of the arrangement for determining blade pressure, as a side view in connection with a blade 12. The arrangement includes the doctor apparatus 10 according to Figure 1, equipped with a doctor blade 12 with a work edge 19, for doctoring or coating a surface 13, and measuring means 15 according to Figure 2. The measuring means 15 include one or more analysis member 16 reacting to loading. The analysis member 16 is arranged to be a separate component, which is arranged for determining the blade pressure between the work edge 19 of the doctor blade 12 and the surface 13. More particularly, the analysis member is fitted to the work edge 19 of the doctor blade 12, where it can be moved in the longitudinal direction CD of the doctor blade 12 (Figure 4) . Thus, when determining the blade pressure, the structure and adjustments of the doctor apparatus 10 remain unchanged, so that the blade pressure determined by the arrangement will correspond precisely to reality. The measuring means 15 can also include means 22 for determining the location of the analysis member in the longitudinal direction CD of the doctor blade. The location of the analysis member 16, in the CD direction of the roll 14 and thus also of the blade 12 can be determined, for example, by means of a sensor 22 measuring distance or distance travelled, such as, for example, a distance laser, a measuring wire, or a roll. Precision in the order of magnitude of, for example, one centimetre, will be sufficient for the positioning means 22. The positioning sensor 22 can be attached, for example, to the rear side of the frame 27 of the analysis member 16. Correspondingly, the positioning sensor 22 can read the location data, for example, from a wire 31, which is strung from end to end of the blade 12 in its longitudinal direction CD. A corresponding CD position can be coded in the wire 31.

Figure 3a shows the analysis member 16, seen more generally in a side view and in Figure 3b in an end view. In its structure, the analysis member 16 is a rigid piece with a shape that does not change, so that it gives true results of the blade pressure. The length Ll of the doctor blade 12 can be many times the length L2 of the analysis member 16 (Figure 3a) . According to one embodiment, the length of the sensor element 16 in the longitudinal direction CD of the blade 12 can be, for example, a few tens of centimetres, for example, 10 cm. It will then be possible to determine the real local loading forces, because the area measured at one time is relatively narrow. In addi- tion, the size of the apparatus can be made so small that one .person can easily perform the measurement and can also easily carry the apparatus with them.

The analysis member 16 includes at least one set of analysis 5 means 23, which are fitted to the frame piece 27 of the analysis member. Thus, the measuring apparatus can consist of a sensor 23, which measures the loading between the blade 12 and the roll 14 and the sensor frame 27, to which the sensor 23 is attached.

10

According to one embodiment, the frame piece 27 can include flat-surfaced parts 27.1, 27.2 arranged opposite to each other, between which, for example, a flat sensor 23 is fitted. In addition, structure elements 27/3, by means of which a groove-

15 like stop 28 for the work edge 19 of the doctor blade 12 is formed, can also be attached to the frame piece 27. The stop 28 can also be parallel to the longitudinal direction of the doctor blade 12. The stop 28 for the work edge 19 of the doctor blade 12 is arranged in connection with the second part 27.2 of

20 the piece 27. Of course, the stop 27 can also be arranged directly in the part 27.2, for example by milling. In a manner that is, as such, known, the work edge 19 of the doctor blade 12 can be formed of a point bevel and a work point at its end (not shown) .

25

Thanks to the stop 28, the analysis member 16 is not attached permanently to either the blade 12 or the roll 14, but instead the member 16 remains, thanks to its own shape, between the blade 12 and the roll 14. Thus, the analysis member 16 remains

30 secured in the doctor blade 12 without separate attachment means. The stop 28 can be, for example, of a sliding material, for example, plastic or metal. Generally, the stop 28 is non- wearing and slippery. After use, particularly a doctor blade 12 used for doctoring has been ground into a sharp shape. The stop

35 28 should then withstand wear, so that the analysis member 16 will not be damaged when determining blade pressure. The stop 28 keeps the piece 27, and thus also the analysis member 16, in the correct position and attitude during measurement.

The frame piece 27 is thin, so that it will not distort mea- surement results. On the other hand, the thickness of the piece 27 does not interfere with the measurement results also in the sense that it will be sufficient if relative data is obtained on the loading, i.e. that they can be compared with the loading at other points in the longitudinal direction CD of the blade 12. The materials of the parts 27.1 - 27.3 are selected in such a way that they do not damage the surface of the roll 14 or the blade 12. For example, a very thin electronic film sensor, to both sides of which plate parts 27.1, 27.2 forming a frame 27 are attached, can be used as the sensor 23. Such a sensor 23 will react to the pressure it experiences and give a voltage or current message proportional to the pressure. The pressure- sensitive sensor can be an as such known PVDF film sensor. It is also possible to use, for example, an EMF sensor operating on the piezoelectric principle, as the pressure-sensitive sensor. In an EMF sensor, the change in resistance in a thin metal film is measured. If the magnitude of the change in the resistance is known, the real blade pressure can be determined.

It can be seen from Figure 3b that a traction point 29 is arranged in the frame piece 27, in order to move it in the longitudinal direction CD of the doctor blade 12. Thus, the position of the analyser member 16 in the CD direction of the blade 12 can be changed by pulling on a cord 30 attached to the traction point 29 (Figure 4) . The traction point 29 can be, for example, in the groove 28. An opposing traction point, to which the other end of the cord can be attached, can be, for example, in the roll counter-piece (not shown) . Figure 4 shows an axial view of the arrangement in connection with several surfaces 13 to be measured. For reasons of clarity, in this case only the doctor blade 12 is shown, and shown only as a broken line. The measuring means 15 also include means 25, 26 for recording the loading signal. A connection lead 24 is run from the analysis member 16 and more particularly from its sensor 23, and can be connected, for example, to a laptop computer 25. By using a centralizer 26 or router, several electronic analysis members 16 can be connected to a single computer 25. The magnitude and position of the blade pressure can then be processed from the voltage signals given by the sensors 23. The blade-pressure profile can than also be determined. Figure 5 shows in greater detail a first embodiment of the method according to the invention for determining blade pressure, in which the apparatus according to the invention can be used in the arrangement according to the invention. Once the machine's production has been run down and the roll 14 has stopped rotating, measuring means 15 with one or several analysis members 16 reacting to loading can be fitted in connection with the measuring target 14 between the work edge 19 of the doctor blade 12 and the surface 13. However, before this, as stage 501, the loading of the doctor apparatus 10 is removed, or at least reduced, so as to permit the installation of the measuring means 15. The doctor blade 12 then detaches from the surface 13.

Once the loading has been removed, as stage 502, the analysis member 16 can be fitted moveably to the work edge 19 of the doctor blade 12. After this, as stage 503, the loading of the doctor apparatus 10 can be reimposed, allowing the production adjustments to be maintained on the blade 12 during measurement. Another possibility for arranging the analysis member 16 on the blade 12 can be to push the member 16 to the other side, for instance, along with the blade 12, for example, when remov- ing an old blade from the blade holder 17, or when installing a new blade in the blade holder 17. In any event, setting the analysis member 16 in place happens place rapidly. As the next stage 504, the blade pressure is determined from the doctor apparatus 10 equipped with a doctor blade 12 with a work edge 19 and intended for doctoring, coating, or creping, by moving the analysis member 16 in the longitudinal direction of the doctor blade 12. During determining, the blade 12 nor- mally used in doctoring is held stationary in the blade holder 17 during the measurement and the analysis member 16 is, for example, pulled between the blade 12 and the roll 14 from one end of the blade 12 to the other at a suitable speed. Thus, in the solution, there is no attempt to measure the loading pro- file simultaneously over the whole blade 12, but instead measurement is performed as if by 'scanning'. In other words, it is also possible to speak of reading progressing over the entire blade length in the machine's cross direction CD. Thus, the measurement is quick to perform and can be easily repeated. In addition, the analysis member 16 is made truly small in size and the loading profile of the blade 12 can be measured comprehensively over the entire main length of the blade 12, for example, using only a single sensor. The analysis member 16 can, for example, be pulled manually along the blade from outside the machine. Thus, the performance of the measurement is simple, because it can be performed entirely from the tending side or drive side of the machine. The determining can be performed as a continuous measurement, in which case the analysis member 16 will produce a measurement signal the whole time, or else as discrete signals at set distances or moments in time.

At the same time as the analysis member 16 is pulled from one end of the blade 12 to the other, the loading signal coming from the analysis member 16 and the position of the analysis member 16 in the machine's CD direction are recorded. Recording can take place, for example, using a two-channel PDA. The distribution of the loading force 12 in the blade 12 in the machine's CD direction, i.e. the loading-force profile, is obtained as a result. Thus, the blade pressure can be determined electronically, so that the measurement results can be recorded and transferred easily.

Figure 6 shows a second embodiment of the method as a flow diagram, in which the change in the loading force is measured. Stages 601 - 603 may correspond to the embodiment of Figure 5. According to this embodiment, in stage 604 the analysis member 16 can also be stopped in connection with the determining of the blade pressure at least once in the longitudinal direction of the doctor blade 12. In other words, during the stoppage, the analysis member 16 is moved to the desired position in the longitudinal direction of the doctor blade 12.

After the stoppage, as stage 605, the loading pressure can be altered at the position in question. At the same time, or after the alteration, as stage 606, the effect of the loading pressure (the loading pressure 18 from the hoses 18, Figure 1) on the force loading the surface 13 of the roll 14 can be determined. Once measurement has been performed at one point, the analysis member 16 can be moved to the next point, i.e. return to stage 604 and repeat the same measuring procedure. This is continued, until measurements have been made at the desired points . In both of the aforementioned embodiments of the method, after measurement the doctor blade 12 is again detached from the surface 13 and the analysis member 16 is removed from the edge 19 of the doctor blade 12. After this, the doctor apparatus 10 is immediately ready for production operation. If necessary, the doctor apparatus 10 is adjusted on the basis of the determined blade pressure and its profile. Through the invention, the determining of blade pressure is rapid and can, if necessary, be repeated after possible adjustments . The arrangement , apparatus , and method according to the invention are suitable for determining the blade pressures of doctor blades in various types of doctor apparatus . Determining is rapid and the result is precise. Determining can be used simply to check the state of the doctor apparatus and the condition of its various components. At the same time, surface damage and, on other hand, possible drop-throughs will be avoided, when the real blade pressure and its profile are known. In addition, through the invention, it will be possible to compare the loadings at different doctoring positions.

Some examples of applications for the arrangement according to the invention are the centre roll in a press section and drying cylinders. The invention is suitable for measuring such critical doctoring positions, where the running down of the web is performed. The invention is particularly suitable for use in connection with a fibre-web machine, the application points being doctor blades that clear the roll surface, coating blades, and creping blades. Of course, the invention can also be used to measure cleaning doctors too. The invention can be used to detect, for example, beam deflections, which can arise in, for example, drop-throughs . In addition, the invention is also eminently suitable for detecting a tilted load.

Because one single sensor 23 is utilized in the invention, the calibration of the apparatus does not become such a large problem as in multi-sensor solutions measuring over the width of the entire machine (differences in the calibration of individual sensors appear as profile errors) . Measurement can be easily performed as either an absolute, or alternatively a relative measurement, depending on the calibration of the sensor 23 used. In addition, it is easy to calibrate an indi- vidual sensor 23 and the calibration can be checked easily and rapidly. It must be understood, that the above description and the related figures are only intended to illustrate the present invention. The invention is thus in no way restricted to only the embodiments disclosed or stated in the Claims, but many different variations and adaptations of the invention, which are possible within the scope on the inventive idea defined in the accompanying Claims, will be obvious to one skilled in the art .